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Kernowite, O Novo Mineral Descoberto Na Inglaterra

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Kernowite, O Novo Mineral Descoberto Na Inglaterra

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O mineral foi descoberto por cientistas que analisaram uma rocha extraída na Cornualha, região litorânea no oeste da Inglaterra, há cerca de 220 anos.

Um grupo liderado por Mike Rumsey, mineralogista do Museu de História Natural, descobriu este extraordinãrio mineral enquanto estudava uma rocha retirada da mina Wheal Gorland no vilarejo de St Day.

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A thousand years ago, a thriving early Swahili village bustled on the banks of Tanzania's Pangani River, a few miles inland from the Indian Ocean. Residents built their houses out of wood lattices daubed with earth. They filled their nets with fish and crafted beads from shells. Their ceramics were plain and functional.

And then one day, a tsunami barreled in, triggered by an earthquake on the other side of the Indian Ocean.

New research, funded by the National Geographic Society and published today in Geology, describes a macabre rarity in the geological record. The villagers evidently had no chance to escape the torrent that overtook them. Many drowned in their razed homes and were buried in the wreckage. As far as the study's authors know, the Tanzanian site is the first-and oldest-tsunami deposit bearing human remains found in East Africa. The oldest such deposit with human remains in the world, found across the Indian Ocean in Papua New Guinea, is 7,000 years old.

The Tanzanian site adds a crucial data point in the study of Indian Ocean tsunamis, which can prove devastating. Even though large tsunamis in the region occur relatively infrequently, about once every 300 to 1,000 years or so, they do happen-and in East Africa, the stakes are high. Tanzania's economic center Dar es Salaam, which sits on the coast, is one of the world's fastest-growing cities. United Nations projections forecast that Dar es Salaam will become a "megacity" with more than 10 million residents by 2030 and may exceed 70 million by the end of the century. ( Find out more about the rapidly growing Dar es Salaam-and how its planners are trying to keep up.)

East Africa got lucky in 2004, when a tsunami triggered by a huge earthquake off the coast of Indonesia killed more than 227,000 people. The bulk of the damage and fatalities from that tsunami occurred in South and Southeast Asia. The waves also made their way to the shores of East Africa, but the first wave made landfall on the continent during an extreme low tide, mitigating its impact.

The tsunami that occurred a thousand years ago, however, was a different story. "It doesn't seem to have been that big of a tsunami, but if people are living on low ground, and they have no idea what's coming, it's probably the worst situation," says Jody Bourgeois, a sedimentologist and tsunami specialist at the University of Washington who reviewed the new study before publication. "There's no earthquake to warn you, because you're on the other side of the Indian Ocean."

Uncovering an ancient disaster

Despite the potential for Indian Ocean tsunamis to reach East Africa's shores, the region's tsunami risk hasn't been studied much. The Tanzanian site is one of only a handful of known East African tsunami deposits from the past 12,000 years. "This kind of information needs to be known by governments and by the population," says lead study author and National Geographic Explorer Vittorio Maselli, a geologist at Canada's Dalhousie University.

Maselli started studying the thousand-year-old tsunami in the spring of 2017, while he was working in the University of Dar es Salaam's geology department. By chance, he found out about the work of archaeologist Elinaza Mjema, also at the University of Dar es Salaam, who had been working at a site 95 miles to the northwest, near the town of Pangani. An early Swahili fishing village, the area once abounded with beads and ceramics, and the university used it to teach proper archaeological field techniques.

But when Mjema took students there in 2010, test pit after test pit revealed human bone. "Every student was going: Teacher, there is a skeleton," he says. "It was a surprise."

Mjema returned to the site in 2012, 2016, and 2017, and his further excavations found bodies that were randomly oriented in the dirt -including one with intact iron bracelets around its ankles. War and disease didn't seem to account for the village's sudden demise. No cut marks or signs of illness were on any of the bones. By the looks of it, the village's men, women, and children had drowned and were buried in the shattered remains of their homes.

A team of researchers including Maselli and study co-author Andrew Moore, a sedimentologist at Earlham College in Richmond, Indiana, visited the site in 2017 to take more sediment samples. They were facing a race against time. The University of Dar es Salaam had begun digging holes on the property to make fish ponds to teach aquaculture, destroying some of the archaeological site in the process. The researchers dug their trenches along the ponds' margins and collected whatever they could. "Within about three months' time, maybe less, they were going to fill those ponds with water," Moore says. "Some of this was very much salvage geology."

The sand that buried the village contained the remains of fish, rodents, birds, amphibians, and even the shells of small marine mollusks-a sign that water had washed in from the Indian Ocean, several miles downriver. And wherever the researchers dug, they kept finding more human bones. "Sometimes, it was kind of emotional-we needed to think about the science, but in the meantime, we were working with the people who died there," Maselli says.

Radiocarbon dating of charcoal and bone in the deposits confirmed that the flooding event happened about a thousand years ago. Tsunami deposits from around the Indian Ocean also date to that time, suggesting that an event similar in scale and intensity to the 2004 tsunami occurred a millennium ago.

Computer simulations found that an earthquake along the Sunda megathrust-the fault off the coast of Indonesia that triggered the 2004 tsunami-could have formed big enough waves to explain the Pangani deposits. The Pangani River's funnel-shaped bay would have amplified the tsunami waves as they raced upriver, making the flooding at the site even more destructive.

"If we go to other places around Africa that saw 2004-like events ... would we find this ancient event writ in the rock history?" Moore wonders.

Revisiting risk

The research team hopes their study will motivate work to assess the tsunami risks facing East Africa. In particular, more detailed mapping of the region's ocean floor is needed, Maselli says. Just like mountain ranges channel the flow of air, the ocean floor's topography affects the movement of waves and currents. And tsunamis don't just come from earthquakes; they can be triggered by underwater landslides, too.

"The United States has a huge program for mapping the entire shelf and slope all along the Atlantic coast for understanding landslides," Maselli says. "We don't know for East Africa."

As for the ancient community, Mjema's archaeological work shows signs of post-tsunami renewal. Within 50 to 100 years, people were building atop the flood deposits. Even today, building in the area continues. Though local officials have started moving construction out of the lowlands, Mjema says, recent buildings have been erected on old tsunami deposits along the Pangani River. Will these communities be prepared for the next possible catastrophe?

"We can learn a lot from the past, if we really want to understand what we are facing," Mjema says.

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1,000-year-old bones represent oldest tsunami victims in East Africa

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A thousand years ago, a thriving early Swahili village bustled on the banks of Tanzania's Pangani River, a few miles inland from the Indian Ocean. Residents built their houses out of wood lattices daubed with earth. They filled their nets with fish and crafted beads from shells. Their ceramics were plain and functional.

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Pedaços raros do manto da Terra encontrados expostos em Maryland

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Pedaços raros do manto da Terra encontrados expostos em Maryland

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Standing among patches of muddy snow on the outskirts of Baltimore, Maryland, I bent down to pick up a piece of the planet that should have been hidden miles below my feet.

On that chilly February day, I was out with a pair of geologists to see an exposed section of Earth's mantle. While this layer of rock is usually found between the planet's crust and core, a segment peeks out of the scrubby Maryland forest, offering scientists a rare chance to study Earth's innards up close.

Even more intriguing, the rock's unusual chemical makeup suggests that this piece of mantle, along with chunks of lower crust scattered around Baltimore, was once part of the seafloor of a now-vanished ocean.

Over the roughly

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Rare chunks of Earth's mantle found exposed in Maryland

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Standing among patches of muddy snow on the outskirts of Baltimore, Maryland, I bent down to pick up a piece of the planet that should have been hidden miles below my feet. On that chilly February day, I was out with a pair of geologists to see an exposed section of Earth's mantle.

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Um dos vulcões mais perigosos de África acabou de entrar em erupção

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Um dos vulcões mais perigosos de África acabou de entrar em erupção

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A structure is surrounded by lava on May 23, 2021, during the eruption of Mount Nyiragongo, which can be seen in the background. A river of lava came to a halt on the outskirts of Goma, sparing the city in the eastern Democratic Republic of the Congo from disaster after the nighttime eruption prompted thousands of residents to evacuate.

Photograph by Moses Sawasawa, AFP via Getty Images

Lava from the recent eruption stopped just short of the city of Goma in the Democratic Republic of the Congo. But geologic factors and inconsistent monitoring make the volcano a perpetual threat.

Mount Nyiragongo is rarely calm. The mountainous volcano in the east of the Democratic Republic of the Congo (DRC) is one of the few places in the world to feature a persistent lake of lava bubbling within its summit crater.

And late on May 22, local time, things abruptly escalated: Fractures opened up in the volcano's rocky sides, spilling fast-moving lava down its slopes. Some of it headed toward the city of Goma, a metropolis just six miles away that's home to around 1.5 million people. The night sky shimmered with a crimson hue as lava, sometimes piling up to three stories high, speedily invaded the streets of several villages surrounding Goma and swallowed any buildings it encountered, setting them ablaze. As of this writing, there have been 15 confirmed casualties, a number expected to rise in the coming days.

Two of Nyiragongo's recent eruptions, in 1977 and 2002, were full-blown disasters. In 1977, estimates suggest somewhere between 600 and 2,000 people were killed by lava flows. In 2002, molten rock destroyed up to a fifth of Goma, leaving 120,000 people homeless and killing around 250 people through carbon dioxide asphyxiation, burns, and the lava-triggered explosion of a gas station.

These past disasters have left volcanologists nervous every time Nyiragongo shows signs of life. "It's one of the most dangerous volcanoes in Africa," says Benoît Smets, a geohazards expert at the Royal Museum for Central Africa in Tervuren, Belgium.

Nyiragongo's deadly reputation is due to a perfect storm of factors. Because of the geologic complexities of the region, its lava is remarkably fluid, able to move at up to 40 miles an hour. Eruptions can also send large amounts of lethal carbon dioxide gas to the surface. That's extremely worrying, since millions of people live in the volcano's shadow.

Debris engulfs buildings in Bushara village, near the city of Goma in the Democratic Republic of the Congo, on May 23, 2021, after Mount Nyiragongo erupted.

Photograph by Justin Katumwa, AFP via Getty Images

Add in the region's political instability and bouts of conflict, and Nyiragongo is a profoundly difficult volcano to monitor. Despite the best efforts of the Goma Volcano Observatory-set up in the eponymous city in 1986-no clear warning signals were detected prior to its latest eruption.

Fuel their curiosity with your gift

With all these factors in play, the fiery mountain is capable of producing "the kind of eruptions you really fear," says Corentin Caudron, a volcanologist at the Institute of Earth Sciences in Grenoble, France.

A tectonic rift

Nyiragongo, whose peak stands 11,400 feet above the DRC's Virunga National Park, owes its existence to two things. One is the leisurely geologic fragmentation of Eastern Africa. A strip of land from the Red Sea down to Mozambique is being pulled asunder, with the Nubian plate to the northwest and the Somalian plate to the southeast moving in opposite directions by a few inches every decade. This tectonic divide is known as the East African Rift.

Among other things, this rifting action makes pathways for magma to rise and create volcanoes. What's more, a plume of superheated but solid mantle material is rising from considerable depth to interact with the underbellies of the tectonic plates. This combination of rifting and pluming creates some strange magmatic concoctions, says Christopher Jackson, a geologist at the University of Manchester in the U.K.

Most magma has a decent amount of silica in it, a compound that acts as a sort of skeleton in molten rock. The less silica you have, the less viscous or goopy the lava is once it erupts. Basaltic magma, the stuff erupting out of Iceland's Reykjanes Peninsula right now, has a low proportion of silica in it, making it fairly runny, but on a flat surface it can easily be outwalked.

Not so for Nyiragongo's molten matter: Its lava has such a deficit of silica that it zips across the ground, especially if the lava is erupting at a high rate. If the lava erupts from a high elevation, the volcano's steep slope may give it an additional speed boost.

A person at the border point known as "Petite Barriere" in Gisenyi, Rwanda, on May 23, 2021, carries a suitcase on their head as people flee from Goma, Democratic Republic of Congo, after Mount Nyiragongo erupted.

Photogrpah by Simon Wohlfahrt, AFP via Getty Images

The volcano's magma is also particularly rich in carbon dioxide, an invisible, odorless gas. This gas often quietly exudes to the surface via aquifers above deep-seated bodies of degassing magma. Being denser than air, the gas gathers unnoticed in low-lying areas. Locals refer to it as mazuku, or "evil wind."

"We have many people die because of mazuku every year in the area," Smets says. If carbon dioxide-rich magma is tapped by Nyiragongo, dangerous volumes of the gas may also gush out of fissures and flood areas rather suddenly.

A volcanic ambush

Eruptions at Nyiragongo generally transpire when the pressure of accumulating magma or an earthquake forces open fissures in the sides of the mountain, leading to the catastrophic draining of the lava lake or the eruption of magma stored deeper down.

But like the volcanoes that make them, individual eruptions have their own unique behaviors and properties, and no two are identical. Monitoring volcanoes for signs of upcoming paroxysms is therefore fraught with difficulties, and Nyiragongo's latest flare-up is a perfect example of these challenges.

Between eruptions, Nyiragongo's summit crater tends to fill up with magma, and it has been doing just that since the 2002 eruption. In 2016, a second vent opened at the summit. In 2020, volcanologists flown in by UN peacekeepers, who shielded the scientists from armed rebels in the area, noticed the lava lake was filling up faster than ever. A worrying sight, but scientists can't be sure whether the height of the lava lake is an indicator of the volcano's readiness to erupt.

On May 10, 2021, the Goma Volcano Observatory detected an uptick in seismic activity at the summit. This was perhaps suggestive of magma moving about at shallow depths, but it was not a surefire harbinger of an upcoming eruption.

The observatory's efforts to keep an eye on Nyiragongo have been somewhat stymied as of late. Some of its seismic stations had been subjected to theft and vandalism, with the risk of violence leaving many of them unrepaired. The observatory also lost financial support from the World Bank last year amid allegations of embezzlement.

Consequently, for several months, remote sensors lacked an internet connection, and regular on-site measurements of the volcano were not possible. Despite these ongoing issues, the observatory, with a small budget from the DRC government, and in cooperation with other international partners, kept up its efforts to monitor Nyiragongo.

But in the end, the volcano erupted unexpectedly, providing no clear geologic hints that it was about to blow. "There was absolutely no precursor for this eruption," Smets says. "Nobody could have detected this eruption" in advance.

This weekend's eruption surprised a city haunted by Nyiragongo's past infernos. Down to luck alone, the lava missed Goma. By Sunday morning, the eruption had lost its intensity. The lava stopped less than 1,000 feet from Goma's edge, leaving behind a frozen, hissing river of volcanic rock.

Even so, tragedy struck 17 nearby villages, which suffered incursions of lava, leading to the loss of hundreds of houses, a school, three health-care centers, and a water pipeline. As of this writing, two people burned to death, nine died in a traffic collision during the chaotic evacuation, and four prisoners were killed as they attempted to escape their cells.

A future of fire

Nyiragongo is still making a lot of seismic noise, and some significant earthquakes are shaking the region, hinting at turbulence below. But scientists don't know whether another eruption could happen soon.

This past weekend is the first time that an expansive suite of monitoring equipment-as opposed to the small assortment of seismic stations in the past-has been up and running during a Nyiragongo eruption. That's great news for those wishing to study the current geologic activity, but without older data to compare it with, the recent volcanic activity is difficult to interpret. But, Caudron says, these records will be invaluable to scientists working to understand the churnings of the volcano in the run up to the next eruption.

Nyiragongo will certainly erupt again, eventually. Lava could tear through Goma next time. If the area's Lake Kivu is disturbed by major underwater volcanic activity, significant quantities of carbon dioxide may flood its shores. And if the magma moves elsewhere below ground, a new volcanic vent could open up in the middle of the city.

The hazards are plentiful and omnipresent around this hyperactive volcano. Goma, along with Gisenyi-a Rwandan city contiguous with Goma-are in near-perpetual peril.

But work is continuously being done to bolster scientists' understanding, from determining how often it erupts to mapping out the likely future paths of lava flows, says Matthieu Kervyn, a natural hazards expert at the Free University of Brussels in Belgium.

Whatever the science reveals, many of the city's residents likely can't or won't move to somewhere safer, even those who live in the eventual paths of the volcano's future flows. Should lava once again slither through the streets of Goma, it could inflict great harm and lasting trauma on millions of people.

But perhaps the recent close encounter with widespread destruction will spark a renewed mitigation effort, leading to more robust scientific work on the ground, more active monitoring, and renewed city planning in the most at-risk areas.

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Mount Nyiragongo just erupted-here's why it's one of Africa's most dangerous volcanoes

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Lava from the recent eruption stopped just short of the city of Goma in the Democratic Republic of the Congo. But geologic factors and inconsistent monitoring make the volcano a perpetual threat.

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Esta notícia aborda o terremoto de Fukushima no Japão que aconteceu no dia 13 de fevereiro de 2021 este teve uma magnitude de 7,1 na escala de Richter acabando por provocar alguns estragos e ferir cerca de 100 pessoas. Mas será que realmente foi um sismo? Não, os cientistas averiguaram a situação e chegaram à conclusão que poderiam ser efeitos secundários da catástrofe de 2011. A catástrofe de 2011 resume-se: "Aconteceu quase 10 anos após o terremoto de Tohoku em março de 2011 , um terremoto de magnitude 9,0 que causou um tsunami catastrófico e resultou em milhares de mortes e no derretimento de um reator nuclear.”. Quando me refiro aos efeitos secundários do sismo de 2011 refiro-me a réplicas que podem demorar anos até décadas para se manifestarem. A zona tectónica deste local é onde a placa tectônica do Pacífico desliza sob a placa na qual o norte do Japão se senta a uma taxa de 7/10 cm por ano ou seja para uma zona como esta foi um terramoto muito simples o que levou a que os cientistas dissessem que tenha sido um um abalo premonitório que é caracterizado desta maneira, quando uma rocha depois de ultrapassar o limite de elasticidade não liberta toda a energia antes acumulada podendo demorar anos e anos até libertá-la toda sob forma de ondas sísmicas que constituem os abalos premonitórios. Tendo os factos de que o terramoto de 2011 libertou 1000 vezes mais energia que o mais recente e que o seu epicentro seja na mesma zona é possível que seja sim uma réplica tal como os cientistas afirmaram na notícia.

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A 7.1 magnitude earthquake was recorded off the coast of Fukushima Prefecture in northeastern Japan on Saturday night, injuring around 100 people, closing roads and trains, and leaving almost a million people without electricity overnight.

It came almost 10 years after the nearby Tohoku quake of March 2011, a magnitude 9.0 earthquake that caused a catastrophic tsunami and resulted in thousands of deaths and a nuclear reactor meltdown.

In the hours after Saturday's quake, there were several aftershocks up to magnitude 5, and officials warned there could be more to come.

The Japan Meteorological Agency said the quake itself was an aftershock of the 2011 event. That might seem odd, but aftershocks of a major earthquake can persist for years and even decades.

How do you know if it's an aftershock?

The earthquake occurred in what's a called a "subduction zone", where the Pacific tectonic plate slides under the plate on which northern Japan sits at a rate of 7 to 10 cm per year. It's an area where there are a lot of earthquakes. It was a structurally simple earthquake: what's called a "thrust" or "reverse slip" quake, in which rock above the fault moves up and over the rock below the fault.

In areas with low seismic activity, we can recognise aftershock patterns for years and decades after a major quake. The Christchurch earthquake of 2016, for example, was an aftershock of the 2010 quake. Some scientists think aftershock sequences in regions like the eastern USA and Australia may persist for centuries.

In these seismically quiet places, it's relatively easier to spot aftershocks. The main hallmark is that the rate of quakes in an area is higher after a major quake than it was before. When the rate of quakes has dropped back to what it was originally, we say the aftershocks have stopped.

AFLO / MAINICHI / EPA

However, in places like Japan with high seismic activity, it can be hard to say whether one earthquake is an aftershock of another.

On one hand, the rates of aftershocks reduced to pre-2011 rates within about 3 years of the Tohoku earthquake and thus the sequence may have concluded.

On the other hand, rates of seismic activity were continuing to decrease in a fashion consistent with an ongoing aftershock sequence. And Saturday's earthquake appears to have occurred in an area that generated fewer immediate aftershocks following the 2011 event, suggesting this earthquake could have occurred as rupture of a remaining "sticky part" of the 2011 fault that generated the Tohoku earthquake.

Read more: Underground sounds: why we should listen to earthquakes

So was this an aftershock?

It's certainly plausible that Saturday's quake was an aftershock.

The 2011 quake was enormous - the largest ever recorded in Japan, and the fourth-largest worldwide since modern record-keeping began around 1900. It released around 1,000 times as much energy as Saturday's earthquake, and created a rupture more than 500 km long with 10s of meters of slip. But the slip on the fault was not uniform and seismic activity continued in some areas that did not fail entirely in that earthquake.

Given all this, it's almost certain there will be some relationship between the two quakes.

What's more, there have been relatively few aftershocks of the 2011 quake close to where this one happened. This suggests it might have been a "balancing out" of stresses.

On the other hand, there have been several magnitude 7 quakes over the past century within 100 kilometres or so of this one, so it's hardly out of the ordinary.

A definite answer on whether this was an aftershock or not will require detailed analysis of the quake and others in the region.

What we can learn from this

A quake like this one can be a valuable reminder of how important it is to learn the lessons of a disaster.

The earthquake generated very strong shaking in areas of Japan that were severely affected by the 2011 earthquake shaking and tsunami. Effects such as liquefaction are likely to have occurred again.

People sometimes think a big quake relieves stress built up in Earth's crust and you can relax afterwards. In reality, it's the opposite. When you have a big quake, there's a higher probability you'll have more to come. Subsequent earthquakes, whether they adhere to statistical definitions of aftershocks or not, can induce recurrent hazards that cause more damage to buildings and infrastructure and present risks to human life.

After a disaster, it is critical to act to reduce future exposure and vulnerability to future disasters through actions such as more considered land-use planning informed in part by better maps of seismic hazards, enhancing coastal protection through engineering of sea-walls and breakwaters and using vegetation, and making sure that warning and evacuation protocols are efficient and effective.

Japan is a world leader in many of these aspects, and the lessons learned from Tohoku are likely to have generated outcomes that minimised some of the loss and damage that could have otherwise occurred from Saturday's earthquake.

Read more: Japan's latest tsunami reaction shows lessons learned from previous disasters

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The Fukushima quake may be an echo of the 2011 disaster - and a warning for the future

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A 7.1 magnitude earthquake was recorded off the coast of Fukushima Prefecture in northeastern Japan on Saturday night, injuring around 100 people, closing roads and trains, and leaving almost a million people without electricity overnight.

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Esta notícia baseia-se numa falha, A Falha de Cascadia situada no noroeste do pacifico, que apresenta elevada potência para atividade sísmica, mas esta é silenciosa(na zona central) e o que fizeram foi tentar explicar esta peculiaridade com imagens do interior da terra (+100 km de profundidade) . Utilizando a teoria do ressalto elástico existem sismos devido ao atrito existente nas falhas\placas tectónicas que ao provocarem tensões nas rochas faz com que haja uma acumulação de energia até estas atingirem o seu limite de elasticidade, quando este é ultrapassado a energia liberta-se propagando-se sob forma de calor e\ou ondas sísmicas, esta peculiaridade existe, devido as placas tectónicas diferentes pressões o que faz com que esta seja mais silenciosa numas zonas mais do que outras, tal como referem na notícia “One has to do with plate locking, which tells us where stress is accumulating along the fault. If the tectonic plates are locked – that is, really stuck together and unable to move past each other – stress builds. Eventually that stress can be released rapidly as an earthquake, with the magnitude depending on how large the patch of fault that ruptures is.”. Para estudarem melhor este fenómeno colocaram vários GPS para identificar os pontos onde se sente que a placa trava mais (existe maior tensão). Com isto verificaram que realmente a zona central é que trava menos (menos tensão) e que a zona onde existe mais atividade sísmica é a do norte onde existe maior tensão (placa trava mais). Concluindo assim que o raciocínio geológico utilizado anteriormente estava correto.

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The Pacific Northwest is known for many things - its beer, its music, its mythical large-footed creatures. Most people don't associate it with earthquakes, but they should. It's home to the Cascadia megathrust fault that runs 600 miles from Northern California up to Vancouver Island in Canada, spanning several major metropolitan areas including Seattle and Portland, Oregon.

This geologic fault has been relatively quiet in recent memory. There haven't been many widely felt quakes along the Cascadia megathrust, certainly nothing that would rival a catastrophic event like the 1989 Loma Prieta earthquake along the active San Andreas in California. That doesn't mean it will stay quiet, though. Scientists know it has the potential for large earthquakes - as big as magnitude 9.

Geophysicists have known for over a decade that not all portions of the Cascadia megathrust fault behave the same. The northern and southern sections are much more seismically active than the central section - with frequent small earthquakes and ground deformations that residents don't often notice. But why do these variations exist and what gives rise to them?

Our research tries to answer these questions by constructing images of what's happening deep within the Earth, more than 100 kilometers below the fault. We've identified regions that are rising up beneath these active sections which we think are leading to the observable differences along the Cascadia fault.

Cascadia and the 'Really Big One'

The Cascadia subduction zone is a region where two tectonic plates are colliding. The Juan de Fuca, a small oceanic plate, is being driven under the North American plate, atop which the continental U.S. sits.

Subduction systems - where one tectonic plate slides over another - are capable of producing the world's largest known earthquakes. A prime example is the 2011 Tohoku earthquake that rocked Japan.

Cascadia is seismically very quiet compared to other subduction zones - but it's not completely inactive. Research indicates the fault ruptured in a magnitude 9.0 event in 1700. That's roughly 30 times more powerful than the largest predicted San Andreas earthquake. Researchers suggest that we are within the roughly 300- to 500-year window during which another large Cascadia event may occur.

Many smaller undamaging and unfelt events take place in northern and southern Cascadia every year. However, in central Cascadia, underlying most of Oregon, there is very little seismicity. Why would the same fault behave differently in different regions?

Over the last decade, scientists have made several additional observations that highlight variations along the fault.

One has to do with plate locking, which tells us where stress is accumulating along the fault. If the tectonic plates are locked - that is, really stuck together and unable to move past each other - stress builds. Eventually that stress can be released rapidly as an earthquake, with the magnitude depending on how large the patch of fault that ruptures is.

Geologists have recently been able to deploy hundreds of GPS monitors across Cascadia to record the subtle ground deformations that result from the plates' inability to slide past each other. Just like historic seismicity, plate locking is more common in the northern and southern parts of Cascadia.

Geologists are also now able to observe difficult-to-detect seismic rumblings known as tremor. These events occur over the time span of several minutes up to weeks, taking much longer than a typical earthquake. They don't cause large ground motions even though they can release significant amounts of energy. Researchers have only discovered these signals in the last 15 years, but permanent seismic stations have helped build a robust catalog of events. Tremor, too, seems to be more concentrated along the northern and southern parts of the fault.

What would cause this situation, with the area beneath Oregon relatively less active by all these measures? To explain we had to look deep, over 100 kilometers below the surface, into the Earth's mantle.

Imaging the Earth using distant quakes

Physicians use electromagnetic waves to "see" internal structures like bones without needing to open up a human patient to view them directly. Geologists image the Earth in much the same way. Instead of X-rays, we use seismic energy radiating out from distant magnitude 6.0-plus earthquakes to help us "see" features we physically just can't get to. This energy travels like sound waves through the structures of the Earth. When rock is hotter or partially molten by even a tiny amount, seismic waves slow down. By measuring the arrival times of seismic waves, we create 3D images showing how fast or slow the seismic waves travel through specific parts of the Earth.

Emilie Hooft, CC BY-ND

To see these signals, we need records from seismic monitoring stations. More sensors provide better resolution and a clearer image - but gathering more data can be problematic when half the area you're interested in is underwater. To address this challenge, we were part of a team of scientists that deployed hundreds of seismometers on the ocean floor off the western U.S. over the span of four years, starting in 2011. This experiment, the Cascadia Initiative, was the first ever to cover an entire tectonic plate with instruments at a spacing of roughly 50 kilometers.

What we found are two anomalous regions beneath the fault where seismic waves travel slower than expected. These anomalies are large, about 150 kilometers in diameter, and show up beneath the northern and southern sections of the fault. Remember, that's where researchers have already observed increased activity: the seismicity, locking, and tremor. Interestingly, the anomalies are not present beneath the central part of the fault, under Oregon, where we see a decrease in activity.

So what exactly are these anomalies?

The tectonic plates float on the Earth's rocky mantle layer. Where the mantle is slowly rising over millions of years, the rock decompresses. Since it's at such high temperatures, nearly 1500 degrees Celsius at 100 km depth, it can melt ever so slightly.

These physical changes cause the anomalous regions to be more buoyant - melted hot rock is less dense than solid cooler rock. It's this buoyancy that we believe is affecting how the fault above behaves. The hot, partially molten region pushes upwards on what's above, similar to how a helium balloon might rise up against a sheet draped over it. We believe this increases the forces between the two plates, causing them to be more strongly coupled and thus more fully locked.

A general prediction for where, but not when

Our results provide new insights into how this subduction zone, and possibly others, behaves over geologic time frames of millions of years. Unfortunately our results can't predict when the next large Cascadia megathrust earthquake will occur. This will require more research and dense active monitoring of the subduction zone, both onshore and offshore, using seismic and GPS-like stations to capture short-term phenomena.

Our work does suggest that a large event is more likely to start in either the northern or southern sections of the fault, where the plates are more fully locked, and gives a possible reason for why that may be the case.

It remains important for the public and policymakers to stay informed about the potential risk involved in cohabiting with a subduction zone fault and to support programs such as Earthquake Early Warning that seek to expand our monitoring capabilities and mitigate loss in the event of a large rupture.

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Parts of the Pacific Northwest's Cascadia fault are more seismically active than others - imaging data suggests why

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The Pacific Northwest is known for many things - its beer, its music, its mythical large-footed creatures. Most people don't associate it with earthquakes, but they should. It's home to the Cascadia megathrust fault that runs 600 miles from Northern California up to Vancouver Island in Canada, spanning several major metropolitan areas including Seattle and Portland, Oregon.

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O que aconteceria se o núcleo da terra arrefece-se?- 2ª parte

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O que aconteceria se o núcleo da terra arrefece-se?- 2ª parte

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Isto irá acontecer pois irá desaparecer as correntes de convecção causadas pelo calor interno na terra o que não irá movimentar as placas tectónicas que não irão originar atividade vulcânica pois não vai haver a ascensão de magma em limites tectônicos(nem no rift de limites divergentes nem em zonas de subducção limites convergente) e como não haveria calor não existiriam também vulcões formados por hotspot (a ascensão das plumas térmicas não aconteceria) também não existiria atividade sísmica natural (causa da exatamente pelo movimento das placas delas “rasparem uma na outra” ou abatimentos vulcânicos) além disso não existiriam ondas marinhas, os animais não conseguiriam orientar-se e não existiria uma proteção contra as partículas nocivas vindas do sol já que ao arrefecer-se o núcleo este perderia, passado algum tempo, o seu campo magnético, causado por um ‘‘redemoinho’’ de ferro fundido no núcleo externo que ao arrefecer deixaria de estar fundido não existindo então o “redemoinho” que origina o campo que é o responsável por  manter todas estas características antes referidas. Além disso a atmosfera iria ser muito fina já que não existiriam vulcões para manterem os solos férteis (não existiria tanta fotossíntese) e não teríamos os gases para compor a atmosfera tal como a conhecemos o que também iria permitir a penetração de alta radiações vindas do sol. Estes fatores fariam todos com que a vida na terra tal como a conhecemos hoje em dia fosse impossível sendo interessante como apenas o arrefecimento do núcleo, condicionando várias características, poderia levar o nosso mundo a destruição.

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O que aconteceria se o núcleo da terra arrefece-se?- 1ª parte

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O que aconteceria se o núcleo da terra arrefece-se?- 1ª parte

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Esta foi a pergunta feita por uma criança(Amelia de 13 anos) a qual um especialista respondeu.

O núcleo da terra está cada vez a arrefecer mais e que quando arrefecer por completo este irá tornar-se completamente sólido isto pois a teoria mais aceite que estudamos na escola e que como existe um aumento de temperatura com a profundidade (verificado pelo gradiente geotérmico e pelo grau geotérmico que estudam a variação da temperatura com a profundidade e quantos m/km se precisam descer para a temperatura aumentar 1°C isto  respetivamente)o núcleo está num estado liquido.

A suposição do que pode acontecer com a terra é que seja parecido com o que acontece/aconteceu em Marte.

Onde teríamos uma atmosfera muito fina sem vulcões e sismos mas porquê ?

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It's core to life on Earth. Shutterstock.

Curious Kids is a series for children of all ages, where The Conversation asks experts to answer questions from kids. All questions are welcome: find out how to enter at the bottom of this article.

What would happen if the Earth's core was no longer molten hot? - Amelia, age 13, Devon, UK

Thanks Amelia, that's a very good question! The Earth's core is cooling down very slowly over time. One day, when the core has completely cooled and become solid, it will have a huge impact on the whole planet. Scientists think that when that happens, Earth might be a bit like Mars, with a very thin atmosphere and no more volcanoes or earthquakes. Then it would be very difficult for life to survive - but that won't be a problem for several billions of years.

Right now, the Earth's core is not entirely molten. The inner core is a sphere of solid iron, while the outer core is made of molten iron thousands of kilometres thick.

Scientists know this because the shock waves made by earthquakes can be recorded on the other side of the Earth - and we would not expect to see them there if the inner core was also molten.

The whole core was molten back when the Earth was first formed, about 4.5 billion years ago. Since then, the Earth has gradually been cooling down, losing its heat to space. As it cooled, the solid inner core formed, and it's been growing in size ever since.

But this process is very slow: the inner core only grows about one millimetre a year, because the Earth has a rocky mantle in between its hot core and its cold surface, which stops it from cooling down too quickly - just like your coat keeps you warm in winter.

The slow cooling of our planet causes the molten iron in the outer core to flow and swirl fast as heat is transported to the mantle, and this gives Earth its magnetic field. The magnetic field is like a magnet that acts at a distance, and even though we cannot see it with our eyes, it does lots of important jobs on our planet.

The Earth's magnetic field protects life on the Earth's surface from harmful particles coming from the sun. It also keeps the planet's atmosphere in place and helps animals to find their way around.

The heat escaping from the core also makes material move around in different layers of our planet - from the rocky mantle to the rigid plates on the surface, where you and I live.

This movement can cause the plates on the surface to rub together, which creates earthquakes and volcanoes. That's why living in places where two plates meet - such as Nepal or Japan - can be very dangerous.

When the molten outer core cools and becomes solid, a very long time in the future, the Earth's magnetic field will disappear.

When that happens, compasses will stop pointing north, birds will not know where to fly when they migrate, and the Earth's atmosphere will disappear. This will make life on Earth very difficult for human beings and other life forms.

When the Earth has cooled completely, the movement in the mantle will also stop eventually. Then, the plates on the surface will no longer move and there will be fewer earthquakes and volcanic eruptions.

You might think that this would be good for people - especially those living in places like Tokyo - but volcanic eruptions also produce fertile soil for farming, and gases that make up the air that we breathe.

After all this, Earth could look a bit like Mars. On the surface of Mars, scientists have seen features that are related to volcanoes and moving plates. But they are not moving any more, and there is no magnetic field and only a thin atmosphere left.

We do not know whether the core of Mars is still molten or not, but a robot called InSight recently landed on Mars that will help us to find out!

But for now, you don't have to worry about the Earth's core losing all its heat and becoming solid, because the mantle is wrapped around the core, keeping it nice and warm.
Hello, curious kids! Have you got a question you'd like an expert to answer? Ask an adult to send your question to us. You can: * Email your question to curiouskids@theconversation.com
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Curious Kids: what would happen if the Earth's core went cold?

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The Earth's core is cooling down, and one day it will be completely solid - when that happens, Earth might look a lot like Mars.

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A rocha mais antiga da terra coletada na lua.

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A rocha mais antiga da terra coletada na lua.

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Uma das rochas coletadas pelos astronautas da Apollo 14, em 1971, contém um fragmento da crosta da terra que apresenta mais de 4,011 bilhões de anos.
Os cientistas acreditam que a rocha teve origem na terra e que devido aos impactos dos meteoritos que ocorreram durante a terra primitiva tenham impulsionada-a para a lua.
“Se isso for verdade, então esta é uma descoberta fascinante” porque como estudamos ao longo destes 2 anos as rochas são muito importantes para o estudo da terra.
Podemos estudar as rochas a partir de dois processos, datação relativa que estuda os princípios estratigráficos e os fosseis e a datação absoluta que envolve o estudo de isótopos radioativos que se direcionam mais para as rochas magmáticas.
A rocha apresenta o tamanho de uma bola de basquete pesando quase 9 quilos.
É identificada como breccia, resultante da colagem pedregosa feita a partir de pedaços de muitas outras rochas diferentes e mais antigas.
Classificando-a como rocha sedimentar, pois é constituída por clastos típicos das mesmas.
Para descobrir a origem desta rocha, os cientistas realizaram um estudo num mineral presente nessa rocha, zircão.
Zircão pode ser identificado como mineral índice, ou seja, é um mineral que nos permite descobrir a que condições a rocha formou-se e o seu tipo.
Após a realização do estudo conclui-se que o mineral formou-se em condições diferentes da lua. Pois, formaram-se em magmas muito mais frios e ricos em oxigénio do que a lua normalmente tem.
Atualmente estão à busca de mais amostras de rochas com formação terrestre na lua.

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Scientists may have just found the oldest intact Earth rock-on the moon. A study published Thursday in Earth and Planetary Science Letters makes the case that one of the rocks collected by Apollo 14 astronauts in 1971 contains a fragment of Earth's ancient crust, dating back more than 4.011 billion years.

It's possible that the fragment formed in a weirdly water-rich pocket of magma deep within the ancient moon. But the study authors think it's likelier that the rock formed within our planet's crust and got jettisoned to the moon by one of the many meteor impacts that bombarded early Earth.

If so, the fragment is one of the oldest Earth rocks ever found. The oldest minerals found on Earth come from Australia's Jack Hills and are up to 4.4 billion years old. But those dates have been disputed, and even if the minerals really are that old, they're debris left over from rocks that disintegrated long ago. By contrast, the Apollo 14 fragment is much more fully preserved.

"It is technically a 'rock,' whereas the Jack Hills [minerals] are individual, contextless crystals," lead study author Jeremy Bellucci, a researcher at the Swedish Museum of Natural History, writes in an email.

The finding adds to the Apollo missions' decades-long scientific legacy, and it further cements the moon as the solar system's premier archivist. Since the moon is so ancient, airless, and geologically inactive, its surface records the history of impacts in the early solar system -most likely including impact debris sent there from other worlds. It's thought that up to 0.5 percent of the schmutz on the lunar surface first formed on Earth, and bits and pieces of other rocky planets, such as Venus or Mars, probably litter the moon, too.

But the Apollo 14 rock, if confirmed to have earthly origins, would be the first of its kind plucked from the moon and in scientific hands.

"If that's true, then this is quite a fascinating finding," says Cornelia Rasmussen, a researcher at the University of Texas at Austin who studies the chemistry of Earth's impact craters. "We don't really have a rock record of this time on Earth, which means [the find] gives us a window to a time we can't really study here."

Digging deep

Collected by Apollo 14 astronaut Alan Shepard on February 6, 1971, the rock bearing the suspected piece of Earth-formally named 14321-is one of the largest that the Apollo missions brought back from the moon.

The basketball-size stone weighs almost 20 pounds. It's a type of rock called a breccia, sort of a stony collage pieced together from bits of many different, older rocks. The impact that made Imbrium crater, one of the huge dark splotches on the moon's near side, likely forged this larger rock and flung it to the Apollo 14 landing site.

Most of its components, called clasts, are dark in color. But one piece stands out as oddly bright, with a makeup similar to the granites you might find on Earth. To find out where did this outlier bit of 14321 came from, Bellucci's team re-sampled the rock and focused on minerals within it called zircons.

"Zircon is an incredibly hardy, robust, sturdy mineral," says study coauthor David Kring, a senior staff scientist at the Lunar and Planetary Institute. "So if you are looking for a relic of the most ancient geologic processes, zircon's a very good mineral to begin with."

When the team analyzed these zircons and the surrounding quartz, they found that the oddball clast formed in conditions that would've been really weird on the moon at the time. For one, the zircons formed in far colder, oxygen-rich magmas than the moon typically has.

In addition, the clast seems to have formed at pressures you'd only find on the moon more than a hundred miles below its surface. But the impact that geologists think formed 14321 probably dug no more than 45 miles into the lunar ground. If the clast formed so deep, how did it get up to the surface?

The researchers soon realized that the clast's head-scratching properties make perfect sense if it instead formed on Earth. About 12 miles beneath Earth's surface, magmas experience temperature, pressure, and oxygen levels just like the ones that formed the mystery clast. When Bellucci made a chart that compared Earth's zircons against the lunar ones, the similarities became clear.

"It was dead in the middle of the terrestrial field, and then I was like, Whoa ... that's awesome!" Bellucci says. "From there, it snowballed."

Seeking more samples

Future research on the samples could firm up Bellucci's interpretation. It's also possible that other moon rocks currently in humanity's collection contain flecks of ancient Earth.

"I'm sure we'll find additional samples, and I have a sneaky suspicion that this is going to prompt a lot of other people in the community to do likewise," Kring says.

Fresh samples from the moon also would help-and may be coming soon. For instance, China's upcoming Chang'e-5 lunar mission is expected to return samples. But for now, work on the Apollo material is grounded. Though U.S. lawmakers have reportedly reached a deal to fund the U.S. government temporarily, the ongoing shutdown has derailed many scientists' lives-including those of the study authors.

As of Thursday evening, Kring says, "my institute is going to be shutting down at the end of tomorrow. We're not going to be able to do the exciting science that this discovery illustrates."

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This may be Earth's oldest rock-and it was collected on the moon

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Scientists may have just found the oldest intact Earth rock-on the moon. A study published Thursday in Earth and Planetary Science Letters makes the case that one of the rocks collected by Apollo 14 astronauts in 1971 contains a fragment of Earth's ancient crust, dating back more than 4.011 billion years.

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Noutro experimento os cientistas vieram a confirmar que os pináculos formam-se devido a fluxos convectivos naturais que aumentam a taxa de dissolução. Usando o mesmo processo para a criação desta floresta eles pensam que os poros ou fissuras das rochas porosas possam atuar como fios protetores e condutores (quase como um fio elétrico onde passa o fluxo de energia) onde fluxos lá passam criando colunas afiadas. Este processo assemelha-se um pouco à formação de estalagmites, já que as gotas que vão caindo no chão vão formar também um pináculo ascendente.

(Os resultados foram publicados no PNAS).

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Segundo uma lenda antiga, uma belíssima donzela, Ashima, afogou-se num rio, acabando por se transformar em pedra, surgindo a maravilhosa Floresta de Pedra de Shilin, na China.

Apesar de ser uma bela história de fantasia, os cientistas encontraram uma explicação para este fenómeno. Eles investigaram os processos de formação destes pilares irregulares, que apresentam formas pontiagudas a seguir à dissolução e exposição ao ar de formações minerais submersas na água.

Para perceberem melhor isto, os investigadores fizeram várias simulações e experimentos com recurso a doces, mostrando então como a água corrente esculpe os picos afiados (este é um processo de meteorização física - a ação das águas em movimento). Durante os experimentos foi referido que estas florestas são um exemplo do relevo cársico ou cárstico (é um relevo geológico que pode ser caracterizado pela dissolução química das rochas - meteorização química - que leva ao aparecimento de várias características físicas, tais como dolinas, lapiás, entre outros; é também importante referir que este relevo ocorre principalmente em terrenos de rochas calcárias, daí ocorrer a dissolução). No decorrer eles explicaram que os pináculos em forma de agulha, bem como os pináculos em forma de pregos resultam primeiramente da dissolução com uma forma suave.

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According to ancient legend, a beautiful maiden named Ashima drowned in a river, and turned into stone. This, it has been said for centuries, is how China's stunning Stone Forest of Shilin first took shape.

According to new research, however, there's another explanation for the phenomenon that gives stone forests their surreal and otherworldly forms, and while it might not quite match the magic and mystery of Ashima's tragic tale, it is perhaps a more convincing take in these modern, sceptical times.

In a new study, scientists investigated the formation processes behind these jagged pillars, which naturally take on their spiky shapes after mineral formations submerged in water slowly dissolve over time once they become exposed to the air.

"This work reveals a mechanism that explains how these sharply pointed rock spires, a source of wonder for centuries, come to be," says experimental physicist Leif Ristroph from New York University.

"Through a series of simulations and experiments, we show how flowing water carves ultra-sharp spikes in landforms."

While it might take decades or centuries for a real stone forest to blossom, the same trick can be observed in just hours with a suitable analogue, the researchers found. In this case, they used candy.

Stone forests are an example of karst topographies, but the hydrological conditions that sharpen the tips of their rocky 'trees' can be mimicked in the lab - or even just the kitchen, it seems - using a recipe of table sugar, corn syrup, and water.

In the right ratios, this makes something called hard-crack candy, which is composed of about 99 percent sugar content. When a block of this candy seeded with an imprint of smooth surface shapes was immersed in water and then removed, the researchers observed it progressively dissolve into an array of sharp spikes in the space of about 2 hours.

"Needlelike pinnacles, as well as bed-of-nails-like arrays of pinnacles, emerge robustly from the dissolution of solids with smooth initial shapes," the researchers explain in their paper.

"Although the liquid is initially quiescent and no external flow is imposed, persistent flows are generated along the solid boundary as dense, solute-laden fluid descends under gravity."

In a separate experiment, the researchers simulated the process in a mathematical model, which confirmed that self-sculpting pinnacles result during dissolution, due to natural convective flows that end up enhancing dissolution rates in a feedback loop that makes the shards sharper, rather than blunter.

As to how the same process creates stone forests in the real world, the team thinks that fluid-filled pores or fissures in porous rock could act as conduits for the same kind of flows, with minor cavities expanding as their surfaces dissolve, and ultimately spawning sharp rocky columns.

"Our pinnacle arrays form via dissolutive widening of pores, whose initial arrangement set the pattern of pinnacles, and a similar progression toward stone forests is thought to be initiated by vertical columns between intersecting fissures," the authors write.

In a lab setting, with a contrived, pre-shaped block of candy, the results produce a neat and symmetrical array of spikes, but as actual stone forests show, the same order is not apparent when this process plays out in the real world - creating a myriad of shapes so striking and unexpected, they can even give rise to legends.

"These events yield a bed-of-nails morphology, here, a square lattice of spikes that reflects the initial lattice of pores," the team explains.

"More random seeding of pore locations is expected to generate disordered arrays of pinnacles of varying girth and height, which may more closely resemble natural pinnacles and stone forests."

The findings are reported in .

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Scientists Finally Discover How 'Stone Forests' Develop Their Otherworldly Forms

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According to ancient legend, a beautiful maiden named Ashima drowned in a river, and turned into stone. This, it has been said for centuries, is how China's stunning Stone Forest of Shilin first took shape.

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As ilhas barreiras como guarda costeiros - 2° parte

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As ilhas barreiras como guarda costeiros - 2° parte

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Em relação à sua formação pode-se chamar a estas ilhas, ilhas em movimento. Dão-lhes este nome já que elas migram naturalmente, para zonas onde irão acumular areia em certas áreas e erodir em outras, sendo por isso sistemas dinâmicos que se formam e reformam constantemente. Porém apesar da migração também se podem formar novas ilhas no oceano, seja porque o nível do mar desceu (e a isto chama-se uma regressão marinha, na qual o hidrodinamismo da água aumenta, aumentando consequentemente a granulometria dos sedimentos que se depositam) ou porque os sedimentos elevam o fundo marinho ou até mesmo a téctonica que o eleva (isto pode acontecer numa situação de limites convergentes, onde ocorre a formação de uma cadeia montanhosa - orogénese -, ou numa situação de limites divergentes porque ocorre um espessamento crustal). Outra hipótese é elas deslocarem-se lateralmente ao longo da costa, enquanto as correntes transportam sedimentos (estas correntes podem estar relacionadas com o hidrodinamismo da água que existe durante uma regressão marinha) de uma extremidade da ilha para outra.

Ao longo do tempo estas ilhas normalmente movem-se em direção à costa, devido à subida do nível do mar (transgressão marinha), na qual as ondas atingem as ilhas durante as tempestades, movendo a areia que se encontra do lado do oceano para o interior.

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As ilhas barreiras como guarda costeiros - 1° parte

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As ilhas barreiras como guarda costeiros - 1° parte

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As ilhas barreiras são os nossos guardas costeiros, protegendo-nos dos furacões e das tempestades, em cerca de 10% dos litorais pelo mundo.

Mas como é que elas fazem isto? Esta proteção começa sobretudo nas finas faixas de areia (basicamente são constituídas por solo arenoso e de fácil erosão, estando sujeitas à ação de ondas que transportam um alto nível de energia) que servem de margem às costas do Atlântico e do Golfo dos EUA. É nelas onde grande parte da força dos furacões e tempestades é absorvida, reduzindo assim a energia das ondas. Para além disto, elas também oferecem a proteção de ambientes permitindo que se formem estuários e pântanos por detrás destas faixas.

E apesar de tudo isto elas também têm funções ecológicas muito importantes, tais como reduzir a erosão costeira, purificar a água e servir de habitat para peixes e pássaros.

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When storms like Hurricane Michael make landfall, the first things they hit often are barrier islands - thin ribbons of sand that line the U.S. Atlantic and Gulf coasts. It's hard to imagine how these narrow strips can withstand such forces, but in fact, many of them have buffered our shores for centuries.

Barrier islands protect about 10 percent of coastlines worldwide. When hurricanes and storms make landfall, these strands absorb much of their force, reducing wave energy and protecting inland areas.

They also provide a sheltered environment that enables estuaries and marshes to form behind them. These zones serve many valuable ecological functions, such as reducing coastal erosion, purifying water and providing habitat for fish and birds.

Many barrier islands have been developed into popular tourist destinations, including North Carolina's Outer Banks and South Carolina's Hilton Head and Kiawah. Islands that have been preserved in their natural state can move with storms, shifting their shapes over time. But many human activities interfere with these natural movements, making the islands more vulnerable.

USACE

Islands on the move

Barrier islands are made of sandy, erodible soil and subject to high-energy wave action. They are dynamic systems that constantly form and reform. But this doesn't necessarily mean the islands are disappearing. Rather, they migrate naturally, building up sand in some areas and eroding in other areas.

New islands can form out in the ocean, either because local sea level drops or tectonics or sediment deposition raises the ocean floor. Or they may shift laterally along the shore as currents carry sediments from one end of the island toward the other. On the East Coast, barrier islands usually move from north to south because longshore currents transport sand in the same direction.

USGS

And over time many barrier islands move landward, toward the shore. This typically happens because local sea levels rise, so waves wash over the islands during storms, moving sand from the ocean side to the inland side.

Building on shifting sands

Building hard infrastructure such as homes, roads and hotels on barrier islands interrupts their lateral migration. Needless to say, beach communities want their dunes to stay in place, so the response often is to build control structures, such as seawalls and jetties.

This protects buildings and roads, but it also disrupts natural sand transportation. Blocking erosion up-current means that no sediments are transported down-current, leaving those areas starved of sediment and vulnerable to erosion.

Many sandy tourist beach towns along the East Coast also turn to beach nourishment - pumping tons of sand from offshore - to replace sand lost through erosion. This does not interrupt natural sand transportation, but it is a very expensive and temporary fix.

For example, since the 1940s Florida has spent over US$1.3 billion on beach nourishment projects, and North Carolina has spent more than $700 million. This added sand will eventually wash away, quite possibly during Hurricane Michael or the next hurricane to hit the coast, and have to be replaced.

What kind of protection?

In some cases, however, leaving barrier islands to do their own natural thing can cause problems for people. Some cities and towns, such as Miami and Biloxi, are located behind barrier islands and rely on them as a first line of defense against storms.

And many communities depend on natural resources provided by the estuaries and wetlands behind barrier islands. For example, Pamlico Sound - the protected waters behind North Carolina's Outer Banks - is a rich habitat for blue crabs and popular sport fish such as red drum.

USGS

Unmanaged, some of these islands may not move the way we want them to. For example, a storm breach on a barrier island that protects a city would make that city more vulnerable.

Here in Mississippi, a string of uninhabited barrier islands off our coast separates Mississippi Sound from the Gulf of Mexico. Behind the islands is a productive estuary, important wetlands and cities such as Biloxi and Gulfport. Because the Mississippi River has been dredged and enclosed between levees to keep it from spilling over its banks, this area does not receive the sediment loads that the river once deposited in this part of the Gulf. As a result, the islands are eroding and disappearing.

To slow this process, state and federal agencies are artificially nourishing the islands to keep them in place and preserve the cities, livelihoods and ecological habitats behind them. This project will fill a major breach cut in one island by Hurricane Camille in 1969, making the island a more effective storm buffer for the state's coast.

When to retreat?

Geologically, barrier islands are not designed to stay in one place. But development on them is intended to last, although critics argue that climate change and sea level rise will inevitably force a retreat from the shore.

Reconciling humans' love of the ocean with the hard realities of earth science is not easy. People will always be drawn to the coast, and prohibiting development is politically impractical. However, there are some ways to help conserve barrier islands while maintaining areas for tourism activities.

First, federal, state and local laws can reduce incentives to build on barrier islands by putting the burden of rebuilding after storms on owners, not on the government. Many critics argue that the National Flood Insurance Program has encouraged homeowners to rebuild on barrier islands and other coastal locations, even after suffering repeated losses in many storms.

Second, construction on barrier islands should leave dunes and vegetation undisturbed. This helps to keep their sand transportation systems intact. When roads and homes directly adjacent to beaches are damaged by storms, owners should be required to move back from the shoreline in order to provide a natural buffer between any new construction and the coastline.

Third, designating more conservation areas on barrier islands will maintain some of the natural sediment transportation and barrier island migration processes. And these conservation areas are popular nature-based tourism attractions. Protected barrier islands such as Assateague, Padre and the Cape Cod National Seashore are popular destinations in the U.S. national park system.

Finally, development on barrier islands should be done with change in mind and a preference for temporary or movable infrastructure. The islands themselves are surprisingly adaptable, but whatever is built in these dynamic settings is likely sooner or later to be washed away.

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Barrier islands are natural coast guards that absorb impacts from hurricanes and storms

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When storms like Hurricane Michael make landfall, the first things they hit often are barrier islands - thin ribbons of sand that line the U.S. Atlantic and Gulf coasts. It's hard to imagine how these narrow strips can withstand such forces, but in fact, many of them have buffered our shores for centuries.

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Como os cristais podem ajudar a prever o futuro da Austrália - 4° parte

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Como os cristais podem ajudar a prever o futuro da Austrália - 4° parte

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Outra opção é usar a química e a forma dos cristais que cresceram dentro do magma, de forma a perceber o “mapa” do interior da Terra percebendo a rota do magma. Nas fotos abaixo pode-se ver as diferentes formas dos cristais: os pontiagudos e em forma de esqueleto crescem quando o magma ascende e arrefece rapidamente.

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Como os cristais podem ajudar a prever o futuro da Austrália - 3° parte

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Como os cristais podem ajudar a prever o futuro da Austrália - 3° parte

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Outra pista são os minerais presentes nas rochas vulcânicas e os fragmentos do manto que elas trazem consigo, isto porque, estes fragmentos preservam as “memórias” do meio no seu processo de ascensão.

Na primeira foto (linha de cima) podemos observar que a espessura da rocha é bastante fina, cerca de metade da espessura de um cabelo humano. Na segunda foto podemos ver que os cristais menores foram formados próximos ou até mesmo na superfície, ao contrário dos cristais menores que foram desenvolvidos em maior profundidade (pode-se dizer isto, já que, para os cristais tornarem-se maiores precisam de mais tempo para se desenvolver e, neste caso, para tal acontecer era necessário formaram-se em profundidade).

As duas outras fotos (linha de baixo) foram tiradas através de um microscópio eletrónico. Nelas podem-se verificar que as bordas dos cristais ficaram mais claras, o que significa que a composição química mudou de maneira a se adaptar ao novo ambiente - a isto chama-se difusão. Esta informação é importantíssima já que os cientistas podem prever o tempo mínimo que o magma leva para viajar da fonte à superfície através desta fronteira química.

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Como os cristais podem ajudar a prever o futuro da Austrália - 2° parte

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Como os cristais podem ajudar a prever o futuro da Austrália - 2° parte

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Então como podemos saber o tempo que resta?

Uma das primeiras pistas que os cientistas têm está nas rochas vulcânicas escuras, ou rochas melanocratas (predomínio de minerais máficos), que contêm peridotito, uma rocha constituinte do interior do manto da Terra. Estes fragmentos terão se juntado às rochas vulcânicas ainda no estado líquido, na ascensão do magma. Este processo teve que se dar rapidamente, pois caso não a constituição de peridotito desta rocha não seria tão alta (isto porque se o magma tivesse levado mais tempo a ascender, ou seja, mais tempo no interior da terra, a rocha vulcânica envolvente teria uma espessura muito maior) como podemos ver na imagem.

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Como os cristais podem ajudar a prever o futuro da Austrália - 1° parte

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Como os cristais podem ajudar a prever o futuro da Austrália - 1° parte

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Ao longo da margem leste da Austrália estende-se por mais de 4000km uma trilha de vulcões, formando um dos cinturões mais longos do mundo, tendo sido à cerca de 5000 anos que as últimas erupções ocorreram (no Mount Gambier e no Mount Schank - cratera de um dos vulcões mais jovens da Austrália). Com base nestas últimas erupções é possível dizer que existem duas regiões vulcânicas ativas possíveis. Uma delas localiza-se no nordeste (sudoeste de Cairns) e no sudeste (de Melbourne até ao sul da Austrália). É nesta última localização que ambos os vulcões - Mount Gambier e Mount Schank - se encontram, fazendo parte da Newer Volcanics Province, uma região que está ativa há pelo menos 4.5 milhões de anos.

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Environmental scientists see flora, fauna and phenomena the rest of us rarely do. In this series, we've invited them to share their unique photos from the field.
Volcanic activity is a constant global threat. It's estimated over 1 billion people live within the potential, direct impact range of volcanic eruptions.

Just recently, lava flows from the eruption of Mount Nyiragongo, a volcano in the Democratic Republic of Congo, killed 32 people, with many more missing. Tens of thousands of people have been forced to flee the city of Goma.

This shows why understanding more about the inner workings of volcanoes is critical to improve the safety of those living in their shadows.

As a volcano scientist, my research takes me across Australia and all over the world. But sometimes, the most stunning revelations actually occur in the lab.

I take a microscopic look at volcanic rocks and fragments of the Earth's mantle to estimate just how fast molten rock (magma) moves from deep in the Earth to the surface. This can help us prepare for future eruptions.

Australia's fiery past - and future

Since the demise of the dinosaurs to recent human settlement, magmatic activity has left behind a trail of volcanoes stretching over 4,000 kilometres down Australia's eastern margin, forming one of the world's most extensive volcanic belts.

Read more: Australia's volcanic history is a lot more recent than you think

The last mainland eruptions took place at Mount Gambier and Mount Schank in South Australia around 5,000 years ago, a mere blink of a geological eye.

These eruptions were witnessed by local Aboriginal people and incorporated into oral traditions that have been passed down for hundreds of generations.

Based on the time since the last eruption, there are potentially two active volcanic regions in mainland Australia: in the northeast (southwest of Cairns) and southeast (from Melbourne across into South Australia).

The Mount Gambier and Mount Schank volcanoes are two of more than 400 volcanoes in the active southeast region called the Newer Volcanics Province, which has been active for at least the last 4.5 million years.

It's considered likely there'll be a future eruption in this province, but it's not known when or where exactly the eruption will be.

So how much warning time might we have?

To answer this question, we have to unravel the secrets held by past eruptions, now locked away in the erupted rocks and the crystals within them.

Our first clue is that many of the dark black volcanic rocks that erupted in the Newer Volcanics Province (and others) contain chunks of green rock, called peridotite.

These dense green rock fragments are, in fact, pieces of the Earth's upper mantle that were plucked out by the rising magma and carried all the way to the surface from depths of greater than 30 or 40 kilometres below our feet.

Heather Handley

These fragments can sink back down through the liquid rock during its ascent, like a pebble dropped into a cylinder of honey. So in order to reach the surface, the rising magma had to move fast - likely taking just a few days from the source.

Volcanic crystal balls

In the same way tree rings can tell you about what the climate was like when the tree grew, the crystals within volcanic rocks and the mantle fragments they carry preserve memories of the environment on their upward journey through the Earth.

In the photo below, you can see how cross-polarised light passing through the mantle rock reveals a mosaic of colourful crystals. The darker part is the enclosing volcanic rock.

This thin slice of rock is just 30 microns in thickness, about half the thickness of a typical human hair.

Heather Handley

Now let's take a look through a scanning electron microscope at the border where the mantle crystals make contact with the now-solidified magma.

In the two photos below, you can see the rim of the crystals has become lighter in colour, which means it changed its chemical composition. This is so it could adapt to its new magma environment on ascent in a process called diffusion.

We use the sharpness of this chemical boundary to estimate how long mantle fragments sat in the magma before the rock erupted.

In other words, the minimum time magma took to travel from source to surface - an eruption warning time.

Read more: Curious Kids: Why do volcanoes erupt?

I can also use the chemistry and shapes of crystals that grew within the magma itself to map out the plumbing system beneath the volcano - the route magma takes to the surface.

The photos below show some of the different shapes crystals can form as the magma rises to the surface, cooling along the way. The spiky and skeleton-shaped crystals grow when the rising magma cools fast and by a large degree.

And we're finding so far that individual volcanoes in the Newer Volcanics Province can take strikingly different pathways to the surface. This could result in varying eruption warning times.

Australia isn't prepared

With likely maximum warning times of some past eruptions in Australia on the order of days, it's worth considering how prepared we are for future eruptions - and not just from within Australia. If the global pandemic has taught us anything, it's to expect the unexpected.

Large volcanic events are far from recent human memory, but in the Asia-Pacific region, they occur with a frequency of around every 400 years.

The federal government's recent announcement of A$600 million towards establishing a new National Recovery and Resilience Agency will help Australia adapt to some climate change-associated hazards. But volcanic events appear to be excluded.

Preparing for the next potentially cataclysmic volcanic event in Australia's neighbouring Ring of Fire should be part of Australia's risk and resilience conversation.

Read more: The government has pledged over $800m to fight natural disasters. It could be revolutionary - if done right

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Photos from the field: the stunning crystals revealing deep secrets about Australian volcanoes

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Environmental scientists see flora, fauna and phenomena the rest of us rarely do. In this series, we've invited them to share their unique photos from the field. Volcanic activity is a constant global threat. It's estimated over 1 billion people live within the potential, direct impact range of volcanic eruptions.

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O Inexplicável Terramoto que Durou 32 Anos

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O Inexplicável Terramoto que Durou 32 Anos

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Os terremotos são resultantes da libertação de energia acumulada nas placas tectónicas através da deformação plástica.

Em fevereiro de 1861 um enorme terremoto de magnitude 8,5 na escala de Richter atingiu a Ilha Indonésia de Sumatra; "causou convulsões na terra, levantando uma parede de água que caiu nas costas próximas e matou milhares de pessoas" - disse Maya Wei-Haas, redatora do Nacional Geografic.

Cientistas afirmam que este grande evento trágico foi o mais longo já registado, que durou mais do que o dobro do recorde anterior- https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2015GL064928

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When a magnitude 8.5 mega-earthquake struck off the Indonesian island of Sumatra in February 1861, it caused the land to convulse, stirring up a wall of water that crashed on nearby shores and killed thousands of people.

Now, it seems that tragic event was no isolated incident: It actually marked the end of the longest earthquake ever recorded, which crept through the subsurface for a whopping 32 years. Known as a slow-slip event, these kinds of quakes have been known to unfurl over days, months, or years. But the newly described event lasted more than twice as long as the past record-holder, scientists report in Nature Geoscience.

"I wouldn't have believed that we would find a slow-slip event so long, but here we found it," says study author Emma Hill, a geodesist at Nanyang Technological University's Earth Observatory of Singapore.

The discovery of such a slow-moving earthquake promises to help scientists grasp the surprising variety of ways our restless planet moves-and the deadly potential for these silent events to spark much more potent quakes.

Much like their high-speed cousins, slow-motion earthquakes release energy built up from the shifts of tectonic plates. But instead of unleashing it in a ground-rattling burst, slow quakes sluggishly release strain over time, and so are not hazards on their own. Still, the subtle shifts of the subsurface potentially load strain on adjacent zones along a fault, which could increase the risk of a bigger temblor nearby.

Other areas of Indonesia are already showing cause for concern. The southern island of Enganno is "sinking a little too fast," says Rishav Mallick, first author of the new study and a Ph.D. candidate at Nanyang Technological University in Singapore. While he cautions that the data come from just one location, they hint that a slow-motion quake may already be in progress near the island.

"It's not just one isolated event in the 1800s," Mallick says. "We're seeing this happen right now."

Clues written in coral

The new study relies on an unexpected scribe of Earth's tectonic shifts: coral.

Some types of coral, such as the finger-like Porites, grow outward and upward until they are lingering just below the water's surface. If the water rises, the coral rapidly shoots upward again. If the water drops, the coral exposed to the air dies, while the submerged part continues growing outward. Because these corals bulk up in layers, like trees growing in concentric rings, scientists can use their skeletons to chart relative water level changes over time.

"They basically act like natural tidal gauges," Hill says.

Changes in sea level can come from climate change-driven factors, such as melting glaciers, or from shifts in the height of the landscape. Off Sumatra's western coast, the latter types of changes lay bare a subterranean battle between tectonic plates.

In this zone, the Australian tectonic plate plunges beneath the Sunda plate, but it gets stuck along a zone directly beneath an arc of Indonesian islands. As the plates collide, the descending slab tugs on the land above. This flexes the surface, which pulls the plate's edge lower into the sea, but causes other parts of the plate to rise.

If the strain builds so high that an earthquake rips through the region, the land will abruptly shift, reversing the effect and sending some coastal areas shooting upward. Just such a shift happened after a magnitude 8.7 quake gripped Sumatra in 2005.

"As the reef moved up in the earthquake, the entire ecosystem was left exactly in place," study co-author Aron Meltzner wrote in a blog about his 2005 field experiences while a Ph.D. student at CalTech. Branching corals, sea urchins, shellfish, crabs, and "an occasional unlucky fish" all lay dead or dying, exposed on nearly dry land.

Meltzner, who is now a geologist at Nanyang Technological University in Singapore, returned to study the corals around Sumatra year after year to untangle the many records they hold. In a 2015 study, he and his colleagues documented the sudden shift in land movements leading up to the giant 1861 quake.

Before 1829, the ground near the island of Simeulue sank by about one to two millimeters each year, based on the coral data. But then the rate jumped suddenly, with the land sinking up to 10 millimeters a year until the 1861 temblor ripped through the region. The team initially thought the change was due to a shifting region where two tectonic plates lock together, but they weren't sure of the precise cause.

In 2016, Nanyang Technological University's Mallick turned a fresh eye on the coral data. By modeling the physics of the subduction zone and the movement of fluids along the fault, the researchers found that the rapid change was caused by a release of built-up strain-the beginning of a slow-motion earthquake.

Earthquake flavors

Slow earthquakes have only been recognized since the late 1990s, when they were initially spotted in the Pacific Northwest of North America and in the Nankai region off the coast of Japan. Their languid energy release means they cause subtle shifts at the surface, so they weren't discovered until GPS technology had improved enough to chart such minuscule changes.

Yet the more places researchers have looked since then, the more slow earthquakes they've found, from the coasts of New Zealand to Costa Rica and even Alaska. "We see aseismic slip everywhere," says Lucile Bruhat, a geophysicist at Ecole Normale Supérieure (ENS) in Paris, France, who wasn't part of the study team.

Slow-motion quakes take on many different flavors. In Cascadia and Nankai, the slow quakes strike with remarkable regularity, stirring every 14 months or so in Cascadia and every three to six months in Nankai. In both locations, these long-duration quakes are also accompanied by a slew of tiny quakes known as tremors.

Bruhat likens the process to a person walking across a wooden floor. "You're moving and the wood is cracking around you," she says. "All the cracks would be tremors."

Over the years, scientists have also found that the duration of slow quakes can vastly differ. In Alaska, for example, researchers discovered one event that lasted at least nine years, only realizing they were looking at a slow quake after the creeping surface halted in 2004, Mallick says. The newfound event near Sumatra pushes the possible durations of slow quakes further than ever before.

"A lot of people have suggested that these bigger, longer slow-slip events are possible," says Laura Wallace, a geophysicist at the University of Texas at Austin and GNS Science in New Zealand, who was not part of the study team. But continuous monitoring of land motions near subduction zones has only happened in the last couple of decades or so, which means "we're really only looking at a small snapshot in time," she says.

Keeping tabs

Understanding these slow events is crucial to grasping the potential risks they pose for triggering bigger temblors. Slow slips preceded many of the mightiest earthquakes ever recorded, including Indonesia's cataclysmic magnitude 9.1 Sumatra-Andaman earthquake in 2004, Japan's devastating magnitude 9.1 Tōhoku earthquake in 2011, and Chile's destructive magnitude 8.2 Iquique earthquake in 2014.

"It's a hot topic right now in the field," says Noel Bartlow, a geophysicist specializing in slow earthquakes at the University of Kansas who was not part of the study team. But precisely demonstrating that slow-slip events can actually spark bigger geologic shudders has long posed a challenge. Not every slow quake leads up to a big shake.

"The evidence is kind of growing, but it's still limited to a few case studies," she says.

Part of the problem is that catching a long-lived temblor in the act is not easy. The lengthy quake in the new study crept along a shallow section of the fault, which lies underwater away from the land, Bartlow explains. But traditional GPS stations are useless on the seafloor since their signals don't penetrate very far through water. And few spots on Earth have a natural record of such movements akin to the corals of Indonesia.

There are instruments that can help, but they're pricey, Bartlow says. She's planning to search for similar shallow slow-slip events off the coast of the Pacific Northwest with instruments that use optical fibers to measure the strain of the surface.

Though monitoring is often considered one of the "less sexy things" scientists can do, Hill says, it's vital to understanding our planet in all its complexities.

"Whenever we think we understand tectonics, then the Earth will throw another surprise at us," Hill says. "The more we collect these really long datasets, the more surprises like this that we're going to get."

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An earthquake lasted 32 years, and scientists want to know how

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The slow quake-the longest ever recorded-ended in disaster in 1861. Experts are racing to find today's equivalents.

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Relâmpagos no Ártico são mais Frequentes e Preocupantes

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Relâmpagos no Ártico são mais Frequentes e Preocupantes

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Os relâmpagos são emissões intensas de radiação eletromagnética que resultam de uma descarga electroestática na atmosfera, produzidos por uma grande diferença de potencial elétrica entre porções de matéria nuvem-nuvem ou nuvem-solo.

Antes era muito raro haver relâmpagos no Ártico, mas com o brusco aquecimento global, este fenómeno tem-se tornado mais frequente.

Este fenómeno tem preocupado bastante os cientistas, pois é um sinal da rápida alteração climática que estamos a viver nos dias de hoje e que no futuro pode despoletar uma cascata de mudanças ecológicas, podendo libertar as enormes reservas de carbono do Ártico para a atmosfera, apressando o aquecimento global.

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Lightning in the Arctic used to be so vanishingly rare that people could go their whole lives without seeing a flash. But as the region warms rapidly, it may become more common-with effects that could reach outside the Arctic.

One recent study projects that the occurrence of lightning in the Arctic could double by the end of the century. Another study suggests that the number of Arctic flashes may have tripled within the last decade alone-though some researchers question that result.

Increased lightning is a worrying sign of today's rapidly accelerating climate change, scientists say, but they're also concerned for the future: More lightning could set off a cascade of ecological shifts that could release huge Arctic reserves of carbon into the atmosphere, accelerating warming further.

"The previous numbers [of lightning flashes] have been small, but it could have a really big climate impact," says Yang Chen, a researcher at the University of California, Irvine, and the lead author of one of the new studies, published in Nature Climate Change.

Lightning-lit fires are increasing

In 2002, when researchers interviewed Indigenous elders from an Arctic community in northwest Canada, none could remember seeing more than a few lightning storms in their lifetimes. One elder recalled having seen a single storm in the 1930s, when she was only five years old.

Scientists weren't really thinking about Arctic lightning back then either: It was so rare that even researchers who had spent decades of summers in the region might have never seen a flash.

"When I first came to Fairbanks, I'd see a thunderstorm and I'd be surprised," says Uma Bhatt, a meteorologist at the University of Alaska, Fairbanks who has studied lightning's rise in the Arctic and has lived in the state for 22 years.

In 2014 and 2015, some of the largest fires ever recorded burned across vast swaths of Alaska and Canada's Northwest Territories. Like over 90 percent of all fires in the Arctic, these were sparked by lightning strikes.

As the Arctic warms and dries, plants there are becoming more flammable. But after 2014 and 2015, Sander Veravebeke, a climate scientist at Amsterdam's Vrije Universitat and a co-author of one of the recent papers, wondered if there was another piece of the story: Were the lightning flashes that start fires also becoming more common?

"I checked the lightning data for those years and saw, ok, this isn't a coincidence," says Veravebeke, "An increase in lightning almost immediately leads to increase in fire."

In a 2017 paper, he and colleagues found that the number of lightning-started fires in Alaska and the Northwest Territories had more than doubled since 1975, culminating in record-breaking numbers of ignitions in both places during the devastating 2014 and 2015 seasons.

Is there more lightning?

But was lightning actually flashing more often across the whole Arctic? That turns out to be a tricky question to answer, because no consistent, continually measured Arctic-wide records of the phenomenon exist.

A satellite launched in 1995 recorded polar lightning flashes, but it retired in 2000. Newer lightning-sensing satellites see only as far north and south as the mid-latitudes, not all the way to the poles.

Ground-based networks, which use sensors that detect the radio waves produced by lightning bolts, now record flashes that happen nearly everywhere in the world. Bhatt, using a regional network in Alaska, found a 17 percent increase in lightning activity between 1986 and 2015.

But Arctic-wide records are short, extending back less than 20 years, and are still not conclusive enough to document a solid trend, climate scientists say.

Recently, a team at the University of Washington dug into data from the World Wide Lightning Location Network, a land-based network of sensors that has been operational since 2004. They found that the number of flashes recorded north of 65 degrees increased from under 50,000 in 2010 to roughly 250,000 in 2020. Some of that might be attributable to an increase in the number of sensors, the researchers say, but estimate that lightning in the region has grown by a factor of three over the last decade.

Another global lightning-detection network run by the company Vaisala, however, does not capture this dramatic increase. The Global Lightning Database 360 became operational in 2012, so their record is shorter than the Washington team's, but the network is more sensitive, recording more and fainter flashes than the others.

But from 2012 to 2020, they didn't record any clear increase in lightning activity, says Ryan Said, a research engineer at Vaisala. That doesn't necessarily mean there isn't a trend, he says-just that it will take more years of observation to really figure out how the patterns are changing.

"This is really just the beginning of that journey," he says.

The Vaisala lightning network has detected some unusual activity in recent years. In the summers of 2019 and 2020 the GLD360 recorded well over 100 flashes north of 85 degrees-including a spate of ultra-rare lightning within 300 nautical miles of the North Pole.

More lightning is probably coming

Whether or not the shifts are already happening, climate change means that more lightning is almost certainly coming to the Arctic, says Chen.

Lightning formation requires some very specific ingredients that have been rare in the far North, but that climate change may be making more common.

First, air at the surface has to be warm and loaded with moisture, ready to buoy rapidly. The air above it must be cold enough that when the warm air shoots upward, its moisture freezes into tiny ice particles. The whole system has to be so turbulent that the air swirls and roils, flinging around the ice particles with such vigor that they knock electrons from each other and become electrically charged. And then, finally, the giant discharge will occur, either within the cloud itself or between the cloud and the ground.

The Arctic's cold, relatively stable atmosphere has not historically proved hospitable for thunderstorms. But air temperatures in the region have risen one to two degrees Celsius in the past three decades alone, faster than anywhere else on the planet.

Chen and his colleagues, including Veravebeke, wanted to estimate how much more lightning those changed climate conditions could induce by the end of the century. They compared the lightning data from the satellite that had recorded Arctic flashes in the 1990s with weather data from the same time period to figure out what atmospheric conditions matched up best with the rare occurrences of lightning in the region.

Climate models projected those specific lightning-conducive conditions, and by extension lightning-which is slightly different from the overall likelihood of thunderstorms-were likely to happen about one and a half times as often over the tundra in the future and nearly double over the northern forests. That's a much bigger relative change than the 50 percent increase projected for the continental U.S. Globally, some research suggests there could be actually be a decrease in total lightning activity by 2100, in part because the lightning-rich tropics may warm so much that ice crystals form less often.

It's not possible to match up the satellite data Chen and his colleagues used to estimate lightning with the ground-based networks used to detect the recent rise in activity, so the two results can't be directly compared or integrated. But they both underscore that "Arctic lightning is becoming more important," says Veravebeke.

But the biggest concern isn't the lightning itself; it's what the lightning might do. Wildfires anywhere in the world can release the carbon stored in forests and soils. The 2020 Australian wildfires, for example, emitted over 800 million metric tons of carbon dioxide, nearly one and a half times the country's annual total.

Fires don't just burn woody stuff aboveground. "Burning is three dimensional," explains Michelle Mack, an ecologist and Arctic expert at Northern Arizona University. It combusts organic matter in the soil below the surface flames-and the soil in the Arctic is much more carbon-rich than in other parts of the world. It often holds decades of accumulated carbon just in the upper few inches. Arctic fires scouring away those surface soils can release at least twice as much carbon as their Californian counterparts, Veravebeke says.

The research suggests that by the end of the century, just because of more lightning starting more fires, the area burned and carbon emitted from the Arctic could increase by over 150 percent over today's average annual fire-related emissions of about 3.4 million metric tons of carbon.

But it could get worse. Fires change the ecosystem, facilitating the northward march of forests and shrubs by opening up new areas for them to grow. That in turn increases the chance of fires, because woody stuff catches fire more readily than tundra.

Forests are also warmer and thus more fire-prone than tundra, because they are darker and thus absorb more sunlight. If lightning-induced fires increase and speed up the northward spread of forests, Chen and his colleagues found, the carbon emissions could increase by 570 percent over today's, adding about 23 million metric tons of CO2 to the atmosphere each year-about a fifth as much 2020's catastrophic in California.

The team outlined but didn't do the math on the scarier carbon concern: that lightning-instigated fires could also expose the carbon-rich permafrost that underlies five million square miles of the Arctic, accelerating the rate at which it's thawing and releasing its immense stores of trapped carbon. In other words, that 570 percent increase in carbon emissions? "That's the low end of the estimates," Chen says.

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Once-rare Arctic lightning is now more frequent-and may reshape the region

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Lightning in the Arctic used to be so vanishingly rare that people could go their whole lives without seeing a flash. But as the region warms rapidly, it may become more common-with effects that could reach outside the Arctic. One recent study projects that the occurrence of lightning in the Arctic could double by the end of the century.

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Foi nas Ilhas Shumagin, no sul do Alasca que os terramotos aconteceram. O primeiro foi do tipo "certo" ao contrário do segundo.

Esta região encontra-se numa zona de subducção havendo por isso terramotos (isto porque nas zonas de subducção - zonas em que uma placa submerge na outra - há bastante fricção entre as duas placas (neste caso é entre a placa Norte-americana e a placa do Pacífico)). Porém, o segundo terramoto não foi consequência desta subducção, mas sim proveniente de um limite transformante, onde duas placas deslizam para lados horizontalmente em relação uma à outra. Mas qual é a diferença entre eles? Basicamente os terramotos provenientes de zonas de subducção tem características diferentes dos de limites transformantes. Enquanto os primeiros são geralmente intermédios ou profundos (desde os 70 km até aos 670 km), os segundos são maioritariamente superficiais (entre a superfície e os 70 km)).

Então, mas como é que os cientistas puderam concluir isto? Eles pensaram que havia uma falha nesta zona de subducção da placa do Pacifíco, mas que não a conseguiam “ver”. Explicaram também que na crosta oceânica há algumas falhas transformantes que se desenvolveram no rifte oceânico, havendo a hipótese desta falha na zona de subducção ser uma “relíquia” do rifte.

Segundo eles, esta descoberta faz sentido e consegue explicar melhor a natureza das ilhas Shumagin, sendo mais provável do tipo desacoplado (mais do que um tipo) do que acoplado (um único tipo).

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The wrong type of earthquake in an area where there should not have been an earthquake led researchers to uncover the cause for this unexpected strike-slip earthquake -- where two pieces of crust slide past each other on a fault -- in places where subduction zone earthquakes -- one geologic plate slipping beneath another -- are common.

"The first earthquake that occurred in the Shumagin Islands region of Alaska was the right type," said Kevin P. Furlong, professor of geoscience, Penn State. "The second one was a strike-slip earthquake and that made no sense. That was the part that got us thinking."

In subduction zones, where two tectonic plates meet, one plate slides beneath the other. If the plates slide smoothly, they are considered unlocked or uncoupled. If the plates hang-up on each other for a time until the forces overcome the friction holding them and then release, causing an earthquake, they are considered locked or coupled. Some portions of a subduction zone can be locked while other parts may be unlocked.

In 2020, a subduction zone interface earthquake, the type expected at a subduction zone, occurred on the Alaska-Aleutian subduction zone to the east of an area called the Shumagin Gap. This first earthquake happened where other, similar earthquakes occurred in the past.

The Shumagin Gap is an area of the subduction zone considered to be unlocked and where geoscientists assume no earthquakes will occur. However, where the first earthquake occurred, just on the edge of the Shumagin Gap, the subduction zone is locked, and earthquakes have occurred there.

In October 2020, a strike-slip earthquake occurred in the Pacific Plate right in the middle of the gap, which was unexpected.

"There must be a fault in the subducting Pacific Plate, and we can't see it," said Furlong.

He explained that in the oceanic crust there are strike-slip faults that develop at the mid-oceanic ridges. This fault in the Shumagin Gap could be a relic of a fault from the mid-ocean ridge, activated in a different way. It appears to be in the correct direction, Furlong added.

To investigate this event, Furlong and Matthew Herman, assistant professor of geology, California State University, Bakersfield, modeled the earthquakes. They also included data from the small tsunami that occurred from the second earthquake. They found that, with the presence of a fault in the subducting plate, the uncoupled nature of the Shumagin Gap made an earthquake there more likely than if the area was coupled. The researchers report their result today (Mar. 24) in Science Advances.

"The potential for unusual earthquakes in these regions makes sense from our computational models," said Herman. "But it is still pretty counterintuitive that making the expected kind of earthquakes less likely actually makes other types of big earthquakes more likely."

The researchers found that tsunami data was helpful, especially in areas where GPS data were not available. Tsunamis also allow paleoseismologists to look at past events through any deposits left by previous earthquakes. Previously there was no evidence of large earthquakes in this area from tsunami data.

"There are probably other areas that are uncoupled where we assume they are safe from earthquakes, but they aren't," said Furlong. "They are unlikely to have a big subduction earthquake, but they could have a strike-slip earthquake. If there are people in the area, it could do damage with shaking and a small tsunami."

Furlong suggested there is an increased recognition that there are other ways of generating earthquakes on plate boundaries, and that we need to be a little more forward-thinking when we consider earthquakes on these boundaries.

The National Science Foundation supported this research.

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earthquakes; natural disasters; tsunamis; geology; geography; oceanography; earth science; landslides

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Weird earthquake reveals hidden mechanism

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The wrong type of earthquake in an area where there should not have been an earthquake led researchers to uncover the cause for this unexpected strike-slip earthquake -- where two pieces of crust slide past each other on a fault -- in places where subduction zone earthquakes -- one geologic plate slipping beneath another -- are common.

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O Planeta Anão Vivo mais próximo da Terra

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O Planeta Anão Vivo mais próximo da Terra

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Um planeta anão é um corpo celeste com massa muito pequena, o que faz com que estes não sejam os astros dominantes na sua órbita e possui uma lua com um valor de massa muito próximo ao seu.

Ceres, o planeta anão mais próximo da Terra, foi identificado em 1801 por Giuseppe Piazzi, um astrónomo italiano, e está localizado entre Marte e Júpiter, numa região conhecida como Cinturão de Asteroides.

Dados retirados entre 2017 e 2018 mostram que é provável que o planeta anão tenha água líquida salgada a escorrer na sua superfície. Com esta descoberta, a humanidade vui de perto que Ceres está geologicamente ativo.

Também se tem conhecimento que este planeta teve um passado ativo, com criovulcões gelados que entraram em erupção à milhões de anos.

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Tucked into the asteroid belt between Mars and Jupiter, the dwarf planet Ceres is a small world that holds big surprises. A slew of new research from NASA's Dawn spacecraft advances the case that-in its own cold, salty way-Ceres is a geologically active body, with ice volcanoes and surviving pockets of an ancient ocean.

About a year's worth of data collected by Dawn from late 2017 through late 2018-during its final orbits before running out of fuel-show that the dwarf planet probably has briny liquid seeping out on its surface, as well as mounds and hills that formed when ice melted and refroze after an asteroid impact about 20 million years ago.

The idea that liquid water could persist on Ceres-a world that's less than a third of the moon's width-would have once seemed outlandish. But now that humankind has seen it up close, we know that frigid, tiny Ceres is geologically alive.

The findings help address Ceres's central mystery: a 57-mile-wide impact crater known as Occator that's covered with perplexing bright spots of salt. As recently as 1.2 million years ago, cold underground brine oozed out onto Occator's floor to form these salty deposits, the new research suggests.

Bulging mountains and hills also support the idea that Ceres experiences a kind of ice-cold cryovolcanism, with briny mud or slush acting like molten lava does on Earth. In one region of Occator's crater floor, Dawn spotted hints that brines had dribbled out of ice volcanoes within the past few decades, if not more recently.

"We've provided strong evidence that Ceres is geologically active in the present, [or] at least in the very recent past," says Dawn's principal investigator Carol Raymond, the manager of the NASA Jet Propulsion Laboratory's Small Bodies Program in Pasadena, California. "And there's some tantalizing evidence that it could be ongoing."

Beyond exotic volcanoes, the new findings add Ceres to the growing list of worlds that had all the required ingredients for life at one point or another: liquid water, energy, and carbon-bearing organic molecules. Thanks to the heat of asteroid impacts, scientists say that Ceres may have been habitable-though not necessarily inhabited-for short periods of time.

"We've got this recent, warm, wet geologic system that has all the ingredients that we think you need for life," says Kirby Runyon, a planetary geologist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, who wasn't involved with the studies.

A dwarf planet up close

Seven studies published today in three journals- Nature Astronomy, Nature Communications, and Nature Geoscience- relay data from the final leg of the Dawn mission, which orbited Ceres from 2015 to 2018. For the mission's grand finale, Dawn swooped to within 22 miles of Ceres's surface, snapping pictures with a stunning resolution of 10 feet per pixel, equivalent to seeing a golf ball from more than a quarter mile away.

Ever since Dawn detected Occator's bright spots in 2015, scientists have puzzled over how they formed. Researchers quickly learned the features were made of salts, likely deposited in the crater from brines seeping up onto Ceres's surface. The question was where the brines came from.

Researchers think Occator Crater is roughly 20 million years old. The impact that created it would have generated immense amounts of heat, turning the normally frigid landscape into a frothy bath of churning saltwater. But using computer simulations, the Dawn team found that the collision's heat largely dissipated within five million years or so.

Some of the salty bright spots were laid down within the past four million years, so the impact couldn't have created them. Instead, the fluids must have been coming from an ancient, deep reservoir of liquid brine.

Ceres's gravity revealed the brine's probable sources, thanks to the fact that a planet's gravitational tug can vary slightly from area to area based on the local landscape and crust density. Researchers could track this variation at Ceres by measuring small-scale changes in Dawn's velocity as the spacecraft orbited the dwarf planet.

When researchers combined this data with Ceres's topography, they found that the ground beneath Occator was less dense than the surrounding crust. Two reservoirs of brine, ellipsoids shaped like giant M&M's, appear to sit below the crater. The bigger one, some 260 miles wide, lies 30 miles directly beneath the crater at the base of Ceres's crust. A smaller briny reservoir about 120 miles wide sits to the crater's southeast, 12 miles beneath the surface.

"If you were to drill, you might be able to reach an aquifer, and then you'd get very cold brine to come out," says Bill McKinnon, a planetary scientist at Washington University in St. Louis who wasn't involved in the new studies.

Oozing leftovers of an ancient ocean

These brine pockets are the relics of a larger, possibly global ocean that once existed on Ceres, the team concluded. As anyone who's driven on a salted road in winter has seen, dissolved salts can keep water in a liquid state at temperatures colder than its usual freezing point. In the case of Ceres, the brines are estimated to be about minus 22°F, requiring a lot of salt and possibly a mixture of muddy, fine-grained minerals to stay in liquid form.

The brines are "definitely not for scuba diving-it's like a big swamp," says study co-author Julie Castillo-Rogez, a JPL planetary scientist and Dawn team member.

Whatever slammed into Ceres and created Occator Crater likely kickstarted the icy volcanism that brought briny material to the surface. Unlike volcanoes on Earth, cryovolcanoes on Ceres develop as ice in the dwarf planet's crust freezes and expands, compressing and pressurizing pockets of underground brine.

The Occator impact cracked Ceres's crust, leaving fractures that deep brines could use to wend their way up to the surface. Once they spilled out, the water evaporated, leaving the bright, salty deposits that we see today.

Some observations even suggest that the activity on Ceres is ongoing. In one of the seven studies, a team led by Maria Cristina De Sanctis, a planetary scientist at Italy's National Institute of Astrophysics, found evidence that Occator's bright spots include hydrated sodium chloride. The water component of this salt should boil off into space within a hundred years of coming to the surface, the researchers say. Since the material is still hydrated, though, Ceres's icy volcanoes could still be chugging along.

"It's very likely that this volcano is still active, in the sense that water, in a lower amount, is still rising," says Dawn team member Andreas Nathues, a planetary scientist at Germany's Max Planck Institute for Solar System Research and co-author of several of the new studies.

The solar system's many icy worlds

Dawn and NASA's New Horizons spacecraft, which flew by Pluto in 2015, have shown that small, icy bodies are far more active than once thought, stretching how scientists imagine the geology of dozens of alien worlds.

Like Ceres and its bright spots, "every planet seems to have its something special," says McKinnon, a New Horizons co-investigator. "Geology is going to rhyme-but it's not going to repeat."

A team led by Castillo-Rogez submitted a proposal to NASA today for a Ceres sample-return mission, which would launch no earlier than 2031, since it can take years to approve, design, and build a spacecraft. The mission would collect a hundred grams of material from Occator's floor and send it back to Earth.

That may not sound like much material to work with, but the samples would represent much more pristine and primitive material than anything we've yet been able to study, Raymond says. "By getting into the details of what is in these bodies, we're going to learn a tremendous amount."

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Dwarf planet Ceres is geologically alive

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Tucked into the asteroid belt between Mars and Jupiter, the dwarf planet Ceres is a small world that holds big surprises. A slew of new research from NASA's Dawn spacecraft advances the case that-in its own cold, salty way-Ceres is a geologically active body, with ice volcanoes and surviving pockets of an ancient ocean.

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Exploração sustentável dos recursos energéticos em Portugal

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Exploração sustentável dos recursos energéticos em Portugal

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Energia eólica ‘offshore’
O projeto piloto Windfloat Atlantic é o primeiro parque eólico marítimo, que fornece uma energia limpa, no sentido da emissão direta de gases de estufa, e inesgotável.
Estas estações promovem a diversificação da origem de energia e um avanço tecnológico na descarbonização, porém não são só vantagens. Elas provocam poluição visual na zona onde são instaladas; poluição sonora aos moradores locais; impactos nos ecossistemas marinhos e na fauna, mais especificamente na colisão de aves; instabilidade associada, já que pode haver alturas em que o vento seja insignificante para poder rodas as pás das turbinas; gasto de recursos minerais para a construção.
Como grupo pensamos que o projeto possa vir a ser rentável, contudo pode trazer grandes riscos para a biosfera, nomeadamente a marinha. Deveria então ser pensado se vale a pena construir estas estações eólicas marítimas.

Energia hídrica ou hidrelétrica
No nosso país cerca de 25/30% das energias consumidas proveem de centrais hídricas (por exemplo, a barragem do Alqueva, no Alentejo). Esta energia é bastante vantajosa, já que é renovável, limpa, contribui para a redução da dependência energética exterior (menos importação de combustíveis fósseis), evita por cada MWh de energia hídrica produzida, a e4missão de 0.37 toneladas de gases com efeito de estufa, entre outras. Contudo, tem algumas desvantagens, sendo principalmente a construção das barragens, que podem vir a provocar alterações nos ecossistemas, erosão dos solos e o deslocamento de populações ribeirinhas e o alargamento da terra (esta última depende maioritariamente da região e do relevo).
Nós achamos que este tipo de energia é bastante vantajoso, porém as construções das barragens nem sempre pode ser uma boa opção, isto é, a produção desta energia pode ter uma finalidade, na qual o termo "renovável" possa não ser aplicado. Quando a energia não tem como fim atender às necessidades energéticas, mas sim lucrativas, tornando-se em algo meramente negociável, causando impactos extremamente prejudiciais ao ambiente e ecossistemas.

Energia geotérmica ou geotermal
Esta energia é maioritariamente usada no arquipélago dos Açores (duas ilhas de São Miguel e uma na Terceira), sendo responsável por 23% das necessidades energéticas. Como neste tipo de recurso, o calor é a fonte de produção de energia, acaba por se tornar uma boa alternativa à queima de combustíveis fósseis, podendo ser usada 24h/dia (ao contrário da energia eólica ou solar). No entanto, esta energia tem bastantes desvantagens começando por ser prejudicial à saúde devido ao sulfeto de hidrogénio, poluição dos aquíferos, dano na paisagem graças à poluição térmica e o elevado impacto ambiental.
Concluímos que este tipo de energia não é uma opção limpa, contudo nas zonas em que se poderia/pode-se aproveitá-la para ser utilizada para os moradores locais ou edifícios.

-Ana, Iolanda, Bianca e Beatriz

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O derretimento dos Glaciares do Alasca estão a contribuir para a ocorrência de terremotos 

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O derretimento dos Glaciares do Alasca estão a contribuir para a ocorrência de terremotos 

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O Alasca Tem uns dos maiores glaciares do mundo. O peso do gelo dos glaciares faz com que a/s placa/s tectónica/s abaixo deles afundem e, quando esses glaciares derretem o solo volta a subir como uma esponja.

O degelo é um fenómeno que acontece devido ao aquecimento global, derivado À intensificação do efeito-estufa, fazendo com que haja um aumento significativo do derretimento do gelo de glaciares, montanhas, etc...

Desta forma, o degelo dos glaciares contribui para a ocorrência de terremotos.

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In 1958, a magnitude 7.8 earthquake triggered a rockslide into Southeast Alaska's Lituya Bay, creating a tsunami that ran 1,700 feet up a mountainside before racing out to sea.

Researchers now think the region's widespread loss of glacier ice helped set the stage for the quake.

In a recently published research article, scientists with the University of Alaska Fairbanks Geophysical Institute found that ice loss near Glacier Bay National Park has influenced the timing and location of earthquakes with a magnitude of 5.0 or greater in the area during the past century.

Scientists have known for decades that melting glaciers have caused earthquakes in otherwise tectonically stable regions, such as Canada's interior and Scandinavia. In Alaska, this pattern has been harder to detect, as earthquakes are common in the southern part of the state.

Alaska has some of the world's largest glaciers, which can be thousands of feet thick and cover hundreds of square miles. The ice's weight causes the land beneath it to sink, and, when a glacier melts, the ground springs back like a sponge.

"There are two components to the uplift," said Chris Rollins, the study's lead author who conducted the research while at the Geophysical Institute. "There's what's called the 'elastic effect,' which is when the earth instantly springs back up after an ice mass is removed. Then there's the prolonged effect from the mantle flowing back upwards under the vacated space."

In the study, researchers link the expanding movement of the mantle with large earthquakes across Southeast Alaska, where glaciers have been melting for over 200 years. More than 1,200 cubic miles of ice have been lost.

Southern Alaska sits at the boundary between the continental North American plate and the Pacific Plate. They grind past each other at about two inches per year -- roughly twice the rate of the San Andreas fault in California -- resulting in frequent earthquakes.

The disappearance of glaciers, however, has also caused Southeast Alaska's land to rise at about 1.5 inches per year.

Rollins ran models of earth movement and ice loss since 1770, finding a subtle but unmistakable correlation between earthquakes and earth rebound.

When they combined their maps of ice loss and shear stress with seismic records back to 1920, they found that most large quakes were correlated with the stress from long-term earth rebound.

Unexpectedly, the greatest amount of stress from ice loss occurred near the exact epicenter of the 1958 quake that caused the Lituya Bay tsunami.

While the melting of glaciers is not the direct cause of earthquakes, it likely modulates both the timing and severity of seismic events.

When the earth rebounds following a glacier's retreat, it does so much like bread rising in an oven, spreading in all directions. This effectively unclamps strike-slip faults, such as the Fairweather in Southeast Alaska, and makes it easier for the two sides to slip past one another.

In the case of the 1958 quake, the postglacial rebound torqued the crust around the fault in a way that increased stress near the epicenter as well. Both this and the unclamping effect brought the fault closer to failure.

"The movement of plates is the main driver of seismicity, uplift and deformation in the area," said Rollins. "But postglacial rebound adds to it, sort of like the de-icing on the cake. It makes it more likely for faults that are in the red zone to hit their stress limit and slip in an earthquake."

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earthquakes; global warming; natural disasters; ice ages; early climate; evolution; ancient dna; fossils

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Melting glaciers contribute to Alaska earthquakes

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Glaciers in Southeast Alaska have been melting since the end of the Little Ice Age, many of which are in close proximity to strike-slip faults. When these glaciers melt, the land begins to rise, and the faults they'd previously sutured become unclamped.

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Geólogos marinhos encontraram um fluxo meteórico de água a 2.625 pés (800 m) abaixo do nível do mar no norte da Noruega.

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Geólogos marinhos encontraram um fluxo meteórico de água a 2.625 pés (800 m) abaixo do nível do mar no norte da Noruega.

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A agua deste é subterrânea meteórica, água doce que se origina de precipitação, como chuva e neve, esta água é tão pura que os pescadores dizem que se poderia fazer até café com ela.
Este vazamento é provavelmente proveniente de um grande aquífero por debaixo dos sedimentos do fundo do mar. Esta formação deverá ter começado durante  a ultima época do gelo,  pois as  espessas calotas polares empurraram para baixo a crosta terrestre com uma força tremenda, espremendo grandes quantidades de água derretida por rachaduras no fundo do mar.
Este fenómeno era inesperado apesar de que tenha acontecido algo semelhante no oceano Atlântico, não se esperava este fenómeno nesta zona.

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Uma "viagem" ao interior da lua a partir de rochas coletadas na Apollo 17 e 15 

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Uma "viagem" ao interior da lua a partir de rochas coletadas na Apollo 17 e 15 

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Alberto Saal um dos autores do estudo diz que por muito tempo consideramos que as rochas basálticas provenientes da lua continham uma variação limitada de isótopos de enxofre indicando que o interior da Lua possui composição homogênea do isótopo. Mas com estas novas rochas "vidros vulcânicos" avaliou-se os isótopos de enxofre com isto verificou-se diferentes quantidades de isótopos indicando que estes viriam de diversas reservas do interior da lua. Com este estudo mostraram que existem variações do isótopo e que estas seriam explicadas pelos processos "recentemente" ocorridos na Lua como cristalização e congelamento.

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Durante as missões do programa Apollo, da NASA, os astronautas coletaram amostras de rochas lunares que foram trazidas para análise em Terra. Agora, ao analisar o material trazido pelas missões Apollo 15 e 17, entre 1971 e 1972, uma equipe de cientistas encontrou uma assinatura de isótopo que indica a ocorrência de eventos geológicos na história recente da Lua, como a formação de seu núcleo e a cristalização do oceano de magma.

Segundo Alberto Saal, co-autor do estudo, por muito tempo foi considerado que as amostras de rochas basálticas lunares tinham variação limitada na proporção de isótopos de enxofre, o que deveria indicar que o interior da Lua possui composição homogênea do isótopo. Agora, no estudo, eles mostraram que os vidros vulcânicos analisados possuem, na verdade, bastante variação na proporção, que pode ser explicada pelos eventos que ocorreram na história recente lunar.

A Apollo 17 pousou na região de Taurus-Littrow, escolhida por suas rochas mais antigas e jovens que aquelas das outras missões (Imagem: Reprodução/NASA/Kevin M. Gill)

Eles trabalharam com a composição do isótopo de enxofre porque ela pode revelar detalhes sobre a evolução química da lava que, um dia, fluiu pela Lua. Assim, eles analisaram 67 amostras de vidro vulcânico com inclusões de lava que foram trazidas durante as missões Apollo, que podem representar alguns dos materiais vulcânicos mais primitivos presentes em nosso satélite natural. Essas inclusões são pequenas bolhas de lava que ficaram presas no vidro, que "prendem" a lava antes que o enxofre e outros elementos sejam liberados como gases nas erupções, um processo chamado de "desgaseificação". Por isso, elas indicam como era a fonte original de lava.

Os cientistas mediram os isótopos do enxofre nas inclusões derretidas e no vidro, e usaram os resultados para calibrar um modelo do processo de desgaseificação para todas as amostras: "após sabermos mais sobre a desgaseificação, é possível estimar como era a composição original do isótopo de enxofre das fontes que produziram a lava", diz Saal. No fim, os cálculos mostraram que a lava veio de diferentes reservas do interior da Lua, com diferentes proporções dos isótopos de enxofre. Os valores do isótopo do enxofre 34, considerado "pesado", podem ser explicados pelos processos de congelamento e cristalização pelos quais a Lua jovem passou.

Isso fez com que o enxofre fosse removido do magma, produzindo reservas sólidas com o isótopo pesado - provavelmente, essa foi a fonte dos valores do isótopo já encontrados em algumas rochas basálticas e vidros vulcânicos coletados na Lua. Os resultados obtidos sugerem que as amostras registraram eventos críticos que ocorreram ao longo da história lunar. Embora mais estudos sejam necessários com outras amostras para que seja possível entender melhor a composição dos isótopos na Lua, estes resultados já ajudam a resolver questões antigas sobre o que fica no interior do nosso satélite natural.

O artigo com os resultados do estudo foi publicado na revista Science Advances.

Fonte: Brown University

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Rochas coletadas nas Apollo 15 e 17 revelam pistas do que há no interior da Lua

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Uma nova análise de amostras de rochas trazidas da Lua durante as missões Apollo 15 e 17 entre 1971 e 1972 revelou processos que ocorreram no início da evolução da Lua, como a formação do núcleo e a cristalização do oceano de magma

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Ka'ena: novo vulcão subaquático no Havai

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Ka'ena: novo vulcão subaquático no Havai

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Na ilha de O'ahu descobriu-se mais um vulcão, que é agora o terceiro.

O Ka'ena foi reconhecido agora como vulcão, porém antes era conhecido por um cume submarino, de batimetria baixa, isto é, pouco profundo. Tendo sido nos flancos (partes laterias) deste cume que os outros dois vulcões, o Wai'anae e Ko'olau se vieram a formar.
Antes deste reconhecimento pensava-se que o Wai'anae era excecionalmente grande, mas os cientistas achavam estranho a sua morfologia e algumas lavas incomuns. Por isto, foram feitas análises e com ajuda de dados geoquímicos, de idade, geofísicos e observações geológicas, confirmaram que Ka'ena não fazia parte do Wai'anae. Era sim um edifício vulcânico mais antigo, que já estava antes da formação destes outros vulcões.

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Novo mineral descoberto no Reino Unido: o Kernowite

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Novo mineral descoberto no Reino Unido: o Kernowite

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É um novo mineral que foi descoberto numa única espécime, extraída à 220 anos, em Cornwall.

O grupo de cientistas responsáveis por esta descoberta, ficaram admirados por nos anos em que estamos poderem adicionar mais um mineral à lista - isto porque durante séculos, os mineralogistas acreditavam que os cristais verdes seriam uma variação de outro mineral, a liroconita. Contudo a análise química mostrou que este tem uma composição diferente.

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Mr Rumsey, principal curator of minerals at the NHM in London, said: "A lot of these discoveries happened over 100 years ago when the mines were still active, so the discovery of a new mineral from Cornwall, particularly one that is related to the region's most famous mineral, is really quite amazing.

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Kernowite: New mineral found on rock mined in Cornwall

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Mr Rumsey, principal curator of minerals at the NHM in London, said: "A lot of these discoveries happened over 100 years ago when the mines were still active, so the discovery of a new mineral from Cornwall, particularly one that is related to the region's most famous mineral, is really quite amazing.

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Novo mineral descoberto no Reino Unido: o Kernowite - continuação

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Novo mineral descoberto no Reino Unido: o Kernowite - continuação

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Mas afinal o que é um mineral e como é que se forma?
Para começar um mineral é uma substância química que ocorre de forma natural por processos geológicos (que podem ser a libertação de voláteis durante erupções vulcânicas com ajuda do vapor na cristalização; depósitos de sais, evaporação e precipitação que formam evaporitos; e outra forma é o metamorfismo que ajuda na recombinação de elementos).
Porém este mineral é do tipo secundário, formando-se de maneira um pouco diferente: a sua formação dá-se quando outras rochas, perto da superfície têm os seus componentes químicos mobilizados pela água que por lá circula, levando que os elementos agora presentas na água se recombinem e formem novos minerais. É por isto que é difícil datar a formação de minerais secundários.

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Vulcão Sinabung na Indonésia voltou a entrar em erupção?

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Vulcão Sinabung na Indonésia voltou a entrar em erupção?

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Como sabemos a indonésia é uma zona que se situa no anel de fogo do pacifico, onde existe o encontro de placas tectónicas que originou mais de 400 vulcões estando pelo menos 129 ativos.
A última vez em que este entrou em erupção foi em agosto de 2020, mas este mês o vulcão voltou a entrar em erupção, desta vez com o uma erupção que surpreendeu todos, com uma grande libertação de cinzas que atingiu os 5 km de altura. Esta erupção cobriu, com uma espessa camada de cinzas, 20 km de raio em volta do cone, apesar de não ter ferido ninguém.
Este vulcão apresenta erupções mistas tal como o tipo de cone indica e a sua formação é consequência do encontro convergente da placa Australiana e a do Pacífico (sendo um vulcão interplaca), que se formou devido à ascensão de magma até à superfície deste tipo de limite.

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O vulcão Sinabung, um dos mais ativos da ilha indonésia de Sumatra, expeliu esta segunda-feira fumo e cinzas a uma altura de cinco quilómetros, não havendo registo de feridos, informou a agência de vulcanologia.

#BREAKING: Large eruption reported at Mount Sinabung Volcano in northern Sumatra, Indonesia. pic.twitter.com/BSxxBfC6Al

- UA News (@UrgentAlertNews) August 10, 2020

Uma espessa camada de cinza cobriu várias aldeias num raio de 20 quilómetros em torno da cratera, disse um funcionário do posto de observação do vulcão Sinabung à agência de notícias Associated Press (AP).

Caída de cenizas en la Ciudad de #Berastagi norte de #Sumatra en #Indonesia ???????? tras la erupción hoy del Monte @Sinabung
Créditos ???? Immanuel Padang https://t.co/rj40PwTdJ4 pic.twitter.com/OTJf0Hx89r

- Geól. Sergio Almazán (@chematierra) August 10, 2020

Os residentes foram aconselhados a permanecer a cinco quilómetros da cratera.

Cerca de 30 mil pessoas foram forçadas a deixar as suas casas nos últimos anos, devido à atividade do vulcão Sinabung.

O vulcão, um dos três que na Indonésia registam frequentemente erupções, esteve adormecido durante quatro séculos, mas entrou em atividade em 2010, provocando dois mortos.

Quatro anos depois, em 2014, morreram 16 pessoas numa erupção vulcânica, e sete em 2016.

A Indonésia situa-se no chamado Anel de Fogo do Pacífico, uma área de grande atividade sísmica e vulcânica, com mais de 400 vulcões, dos quais pelo menos 129 continuam ativos e 65 são qualificados como perigosos, incluindo o Sinabung.

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Vulcão indonésio Sinabung entrou em erupção: lançou fumo e cinzas e não causou feridos

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O vulcão Sinabung, um dos mais ativos da ilha indonésia de Sumatra, expeliu esta segunda-feira fumo e cinzas a uma altura de cinco quilómetros, não havendo registo de feridos, informou a agência de vulcanologia. #BREAKING: Large eruption reported at Mount Sinabung Volcano in northern Sumatra, Indonesia.

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Drone regista a formação de um tornado nos Estados Unidos

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Drone regista a formação de um tornado nos Estados Unidos

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No dia 17/03/2021 foram registados mais de 21 tornados nos Estados Unidos.
Durante esse dia um drone conseguiu registar a formação de um dos tornados, resultante da mudança na direção do vento e do aumento da velocidade com a altitude, criam uma tendência de rotação horizontal, através da contribuição de correntes de ar frio e quente.
A primavera é uma altura muito marcada por estes fenómenos nos Estados Unidos. Isto deve-se ao encontro de uma massa de ar frio e seco, que vem do Canadá, com uma massa de ar quente e húmido, que chega do Golfo do México.

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Drone registra formação de tornado no Alabama, EUA

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Drone registra formação de tornado no Alabama.

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Todos os anos o continente americano afasta-se 4cm da Europa e da África!

Neste estudo descobriu-se a razão deste afastamento.
É na dorsal meso atlântica. Devido ao limite divergente das placas, que se movem em sentidos opostos, o magma começou a ascender para preencher os espaços vazios à medida que as placas se afastam.

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Quatro centímetros. Esta é a distância que todos os anos o continente americano fica mais longe da Europa e da África. Ou que o Atlântico fica mais largo, se quisermos ver por outra perspetiva. E a culpa é de um raro fenómeno geológico: um aumento de matéria nas profundidades da crosta terrestre bem no meio deste oceano.

As conclusões são de uma investigação científica cujos resultados foram publicados esta quinta-feira na revista Nature. Trocado por miúdos, ou seja simplificando o tema para leigos, estes continentes estão assentes em placas tectónicas que se movem muito lentamente. O que este estudo mostra é que a placa dos continentes americanos (Norte e Sul) e as placas da Europa e África se estão a afastar muito mais depressa do que era suposto.

Entre estes continentes, bem no fundo do mar, está a dorsal mesoatlântica, que faz parte do sistema global de dorsais oceânicas, grandes cadeias de montanhas submersas que resultam exatamente do lento afastamento das placas tectónicas. Esta longa cordilheira (nalguns pontos emerge à superfície em pequenas ilhas), é o limite divergente das placas que se movem em sentidos opostos. O magma do interior da Terra ascende pelo espaço que se forma: debaixo desta crosta, a matéria sobe para preencher esse espaço vazio que é criado à medida que as placas se afastam.

Até agora, a comunidade científica acreditava que esse processo era impulsionado pelas forças da gravidade. Isso fazia com que as partes mais densas das placas voltassem para o fundo Terra. No entanto, a força motriz por trás da separação das placas do Atlântico permanecia um mistério, porque este oceano não tem placas densas, e elas não se afundam, iam ficando no fundo do mar, formando novas placas.

Agora, o que esta equipa de sismólogos sob comando da Universidade de Southampton encontrou foram evidências de um afloramento do manto da terra, o material entre a crosta terrestre e o seu núcleo, que pode estar a empurrar estas placas de baixo e a fazer com que os continentes se desloquem muito mais depressa.

O mais estranho é que quando estes afloramentos acontecem - e eles já aconteciam - dão-se a pequenas profundidades, máximos de 60 km. Este está a gerar-se a mais 600 km, nas profundidades do Atlântico.

Podemos agora perguntar, e o que é que isto interessa? De facto, já se sabia que a América se estava a afastar da Europa e de África há milhares de milhares de anos. Que até já estiveram unidas. Mas estes resultados trazem novos conhecimentos sobre como o interior da Terra, o fluxo do magma (sempre em movimento, em correntes de convecção) está afinal ligado às placas tectónicas. E estas observações nunca tinham sido vistas.

Mais, e mais importante. Esta descoberta sobre a movimentação das placas permite que se compreenda cada vez melhor os desastres que elas provocam. E não são poucos: desde sismos a tsunamis, acabando, claro, em erupções vulcânicas. Um dia, talvez, sejamos capazes de os prever.

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O Atlântico está a ficar cada vez mais largo. A culpa é de um fenómeno geológico raro, mas que pode um dia ajudar a prevenir sismos

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Quatro centímetros. Esta é a distância que todos os anos o continente americano fica mais longe da Europa e da África. Ou que o Atlântico fica mais largo, se quisermos ver por outra perspetiva. E a culpa é de um raro fenómeno geológico: um aumento de matéria nas profundidades da crosta terrestre bem no meio deste oceano.

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Inundações na Austrália fazem milhares de pessoas serem evacuadas à medida que a intensidade da chuva piora

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Inundações na Austrália fazem milhares de pessoas serem evacuadas à medida que a intensidade da chuva piora

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A costa do estado New South Wales está sob alerta severa por conta do mau tempo.

As inundações são fenômenos naturais, mas podem intensificar por conta das práticas humanas nos espaços urbanos.
Normalmente os rios que nunca secam durante o ano costumam ter dois tipos de leito: um menor e principal, por onde a água corre durante a maior parte do tempo, e um maior e complementar, que é alcançado só em períodos de cheias. Este fenómeno é mais comum em áreas planas, também chamadas de planícies de inundação.
A interferência do Homem nos cursos de água, podem também provocar cheias e inundações, de diversas formas. Em casos extremos, apesar de serem menos comuns, tais situações podem estar relacionadas com rompimentos de diques e barragens, o que pode causar problemas sérios à sociedade. Mas, na maioria das vezes, está ligada à má utilização do espaço urbano, tal como o entupimento das fossas e esgotos, problemas nos sistemas de drenagem, remoção de vegetação, impermeabilização do solo e ocupação desordenada do espaço geográfico.

"1.400 socorristas conduziram mais de 700 resgates em enchentes e
responderam a mais de 7.500 pedidos de assistência."

Apesar da chuva forte causar inundações, também atrasa a vacinação da população contra a covid-19.

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Some 18,000 people have been evacuated from severe floods across New South Wales (NSW) in Australia, with more heavy rainfall predicted.

The state's entire coast is now under a severe weather warning.

Days of torrential downpours have caused rivers and dams to overflow around Sydney - the state capital - and in south-east Queensland.

The military is being deployed to help with search and rescue, in what has been called a "one-in-50-years event".

Australia's Bureau of Meteorology has forecast "increased rainfall, strong winds, damaging surf and abnormally high tides" in New South Wales on Tuesday.

It also said that some 10 million people across every state and territory except Western Australia were now under a weather warning.

NSW Premier Gladys Berejiklian said no deaths had been reported by late Monday - describing it as "a miracle given what we have been through".

But there has been widespread damage in the affected areas, which are home to about a third of Australia's 25 million people.

Ms Berejiklian said many of the communities "being battered by the floods" had been affected by bushfires and drought the previous summer.

"I don't know any time in state history where we have had these extreme weather conditions in such quick succession in the middle of a pandemic," she said.

PM Scott Morrison has offered funds for those forced to evacuate. He told parliament there was "serious risk still ahead".

Swollen rivers cut off roads and bridges, and almost 200 schools in NSW will remain shut on Tuesday.

People in more than 15 mostly low-lying areas have been ordered to evacuate and a similar number have been given evacuation warnings.

Areas north and west of Sydney, the NSW Central Coast and the Hawkesbury valley have been of particular concern.

There have been some 15,000 evacuations from the Mid-North Coast and a further 3,000 in Sydney, officials said.

The Australian Defence Force will provide search and rescue helicopters on Tuesday, after a request from the NSW government.

PM Morrison told MPs: "Across NSW, 1,400 first responders have conducted over 700 flood rescues and responded to over 7,500 requests for assistance."

He added: "This is an ongoing situation that is evolving and is extremely dangerous."

One stranded family was lifted from their flooded home by a helicopter. Responders also saved a family with a baby from flooding in their home in Sydney's west.

There have been images of dead wildlife, livestock floating through flooded areas and rows of houses engulfed up to their windows.

The Hawkesbury and Nepean rivers - which border Sydney to the north and west - reached higher levels on Monday than during a devastating flood in 1961.

Meanwhile, the Warragamba Dam, Sydney's main water source, began spilling over for the first time in five years. It reached a peak daily discharge on Sunday of 500 gigalitres - equivalent to the volume of Sydney Harbour - before falling back to 300 GL on Monday.

On Sunday a young couple saw their house north of Sydney swept away by flash floods on what should have been their wedding day. Shocked neighbours filmed the uprooted three-bedroom cottage bobbing along the Manning river after it burst its banks.

In Port Macquarie's North Shore, one resident was filmed dragging a stingray through what was his front lawn.

In south-east Queensland, flash floods also affected Brisbane and the Gold Coast at the weekend.

What is the latest forecast?

Conditions in many areas of New South Wales are expected to worsen, with officials warning that two weather systems could collide, creating a "last blast" of rain and storms going into Wednesday.

The Bureau of Meteorology said heavy rainfall would affect the whole NSW coast and several inland areas on Tuesday, bringing a "serious risk" of flash flooding.

"This situation is far from over," it tweeted.

But it added: "Most areas of New South Wales will see a clearing trend early Wednesday as a drier airmass moves into the region."

The bureau said the rainfall so far - up to 90cm in some areas - had been "extraordinary", with many areas across NSW resembling an "inland sea".

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Ms Berejiklian, the NSW premier, said: "What we're going through now is different to what you've been through for the last 50 years, so please take it seriously."

Jamisontown resident Ellen Brabin told ABC News that she had not seen floods as severe as this in more than 40 years.

"I've seen all the floods and stuff, and never had to move before so this is different," she said.

From fires to floods

The intense summer of rain and floods in eastern Australia is a stark contrast to a year ago, when many of the same areas were scorched by mammoth bushfires and ravaged by drought.

This side of the continent is currently experiencing a La Niña weather pattern, which typically brings more rainfall and tropical cyclones during summer.

Two of Australia's three wettest years on record have been during La Niña events. Typically a La Niña sees a 20% increase in average rainfall from December to March in eastern Australia.

Scientists say that climate change is also intensifying La Niña's impact, and making weather patterns more erratic.

Are you in the affected region? If it is safe to do, share your experiences by emailing haveyoursay@bbc.co.uk.

Please include a contact number if you are willing to speak to a BBC journalist. You can also get in touch in the following ways:

If you are reading this page and can't see the form you will need to visit the mobile version of the BBC website to submit your question or comment or you can email us at HaveYourSay@bbc.co.uk. Please include your name, age and location with any submission.

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Boats and boating--Equipment and supplies

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Australia floods: Thousands evacuated as downpours worsen

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A severe warning is extended to the whole New South Wales coast, in the worst flooding in decades.

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Portáteis e telemóveis são os novos "diamantes de sangue"

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Portáteis e telemóveis são os novos "diamantes de sangue"

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Nesta notícia é possível observar-se o quanto os recursos são explorados, tal como as pessoas que trabalham nestes locais que passam horas exaustivas nestes locais,  sem qualquer tipo de proteção e uma remuneração baixíssima para este trabalho.
Segundo a notícia publicada nos 7 mares, por António Marujo, no dia 11 de setembro de 2020 morreram 50 jovens, pois ficaram bloqueados nos túneis de uma mina, próxima ao rio Elila que transbordou por conta da chuva forte e que foi o suficiente para causar uma grande tragédia.
Existem empresas mundialmente conhecidas que contribuem para a exploração destes materiais e das pessoas que são obrigadas a trabalhar entre 10 a 12 horas por dia, para o fabrico de todo o tipo de eletrodomésticos, mas aquele que se destaca em primeiro lugar é o telemóvel.
Este tipo de exploração é, geralmente, subterrânea, em minas, em que os seus recursos são de domínio público do estado, tendo que os recursos extraídos destas explorações são os mais valiosos. Quando se encontra um novo jazigo novas pessoas são procuradas para explorar estes recursos e trazer benefícios para o estado, o problema é que muitas vezes acabam por serem jovens ou crianças que por falta de segurança e uma instabilidade das minas acabam por falecer ou contrair graves doenças.

Na nossa opinião algo devia ser feito, pois as pessoas que trabalham nas minas estão constantemente em perigo.
Por ano morrem 15000 pessoas e nesta estatística são incluídas crianças e jovens que continham uma vida inteira pela frente, em que a maioria está em busca de dinheiro para sobreviver (algumas crianças chegam até a desistir da escola). Para estatísticas encontramos um site que mostra os anos de vida perdidos com a intoxicação pelo mercúrio nas minas.
Devemos arranjar uma solução para este problema como, por exemplo, tornar o trabalho da mineração mais justo, tanto nos salários como na segurança/direitos (humanos e dos trabalhadores).

-Ana, Iolanda, Bianca e Beatriz

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Uma das grandes figuras da teologia contemporânea, estudioso e defensor do movimento ecuménico: Hans Küng morreu esta terça-feira, 6, na Alemanha, país em que há muito vivia, com a idade de 93 anos.

Se queremos compreender como se desenvolveu a ética económica na cristandade medieval e, depois, no capitalismo, temos de procurar mover-nos na sua radical ambivalência, partindo da primeira teologia cristã. As diversas conceções medievais, o debate que delas brotou e a questão que hoje se coloca (não só) à Europa.

"Há portas que não devem ser fechadas, porque Deus é que está do outro lado dessas portas", dizia, a terminar o debate, Jorge Teixeira da Cunha, padre e professor de Teologia Moral na Universidade Católica Portuguesa (UCP), no Porto. No programa Olhe Que Não, que passou nesta quarta-feira, 7 de abril, ao início da tarde, na TSF, com moderação do jornalista Pedro Pinheiro, discutiu-se o documento da Congregação para a Doutrina da Fé, do Vaticano, que respondia "negativo" a uma pergunta sobre se a Igreja não pode abençoar uniões homossexuais.

É uma tomada de posição conjunta muito pouco frequente: o arcebispo de Cantuária e primaz da Igreja Anglicana, Justin Welby, e o cardeal Vincent Nichols, arcebispo de Westminster e presidente da Conferência Episcopal [católica] de Inglaterra e Gales, publicaram na edição de 6 de abril do Evening Standard uma carta aberta em que criticam asperamente a decisão do Governo do primeiro-ministro Boris Johnson de suspender a ajuda humanitária a vários países.

A audiência geral do Papa Francisco desta quarta-feira, 7 de abril, foi transmitida nos novos canais de Youtube do Vaticano com tradução em língua gestual italiana e também em língua gestual americana.

Que me fosse concedido o desejo de aquietar a consciência, aquele dom invejável dos sábios discretos;
às tantas, vivo cansada de uma mente desobediente a perturbar cada instante que a vida me dispõe.

Se os cristãos fossem hoje a cumprir a Torah à letra estaríamos a apedrejar até à morte os adúlteros e os homossexuais, não poderíamos envergar roupa com incorporação de determinados tipos de tecidos, não podíamos comer um rol imenso de alimentos e satisfaríamos muitos outros interditos, além de guardar religiosamente o sábado, quando ninguém poderia trabalhar.

Daniel Faria o último grande poeta português do século XX, morreu há pouco mais de vinte anos. No sábado, dia 10, assinala-se o 50.º aniversário do seu nascimento. A Associação Casa Daniel assinala a efeméride com a iniciativa "50 Vozes para Daniel Faria" para evocar os poemas e a memória do poeta.

breve comentário aos textos bíblicos lidos em comunidade | Páscoa - Dia de Páscoa B | Lisboa, 4 de Abril de 2021.
António Pedro Monteiro

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Os jovens explorados e mortos no Congo para que possamos ter telemóveis e computadores

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Cada operação dos nossos telemóveis, computadores ou jogos electrónicos, cada airbag dos automóveis ou cada arma sofisticada têm, na sua origem, uma indústria de escravatura e morte. Curta viagem às minas do Congo, onde há duas semanas morreram mais 50 pessoas - entre as quais muitas crianças e jovens - vítimas de mais uma das tragédias frequentes na mineração artesanal.

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Rifte vai dividir África em dois e formar um oceano no meio

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Rifte vai dividir África em dois e formar um oceano no meio

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Uma fissura de 15 metros de profundidade e 20 de largura está a dividir o Quénia, destruindo também  a autoestrada Nairobi-Narok.
Esse acontecimento acaba por relembrar aos cientistas um facto importante já esquecido "Africa está se a dividir".
Os cientistas acreditam que daqui a cerca de cinco milhões de anos África não será um continente, mas dois.

Mas porque razão?
Esse rifte formado situa-se num local de encontro de duas placas tectónicas: a Africana e a Somali. Ambas as placas estão a realizar um movimento divergente ou seja estão afastando-se uma da outra. Acabando por originar um rifte que é uma designação dada às zonas onde a crosta terrestre e a litosfera associada estão a sofrer uma fratura acompanhada por um afastamento em direções opostas de porções vizinhas da superfície terrestre.

Acredita-se que a fenda não irá para de crescer por causa da forte atividade vulcânica presente.

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Pode demorar entre cinco e dez milhões de anos, mas os cientistas acreditam que vai mesmo acontecer: o continente africano ficará um dia dividido em dois. A convicção vem do comportamento das placas tectónicas na região de Afar, Etiópia, no leste africano, uma paisagem rochosa onde três pedaços de crosta terrestre se encontram.

As placas tectónicas são elementos rochosos de formato irregular que avançam, deslizam, comprimem, mas sobretudo separam-se, e que em África foram dando origem, ao longo de milhões de anos, ao que hoje se conhece como Mar Vermelho e ao Golfo de Aden. A "placa Árabe", como é conhecida a que fica no topo do vértice, afastou a região da Arábia, onde hoje fica o Iémen, de solo africano, na zona do Djibuti, dividindo aí os dois continentes.

Barcroft Media

As outras duas placas que formam este triângulo no leste de África são a "placa Núbia" e a "placa Somali", e também elas estão a ficar cada vez mais distantes.

Estes fenómenos geológicos, nos quais África é rica, ficam numa zona conhecida como Vale do Rift, que se estende por mais de três mil quilómetros entre a Etiópia, o Quénia, a Tanzânia e parte de Moçambique, cortando o território desses países e separando-os do resto do continente. É aí que deverá formar-se uma nova bacia oceânica.

Importa dizer que este enorme espaço que atravessa o Vale do Rift não é totalmente visível, mas apenas em partes, como na fenda que se deixa ver no deserto da Etiópia e que tem cerca de 56 quilómetros.

SIMON MAINA

Em maio de 2018, uma outra fenda apareceu no Quénia, na mesma região do Vale do Rift, cortando o território entre a capital, Nairobi, e Narok. O aparecimento foi atribuído tanto à atividade sísmica como a fortes chuvas que o país tinha sentido no mês anterior.

A maior parte do trabalho científico é, por isso, feito a partir de satélite e do apoio de instrumentos de GPS, que permitem identificar e medir de forma mais precisa o comportamento do solo. Uma das grandes dúvidas que ainda permanecem é mesmo o que está a causar a divisão, ainda que a forte atividade vulcânica na região possa explicar parte. Um desses vulcões é o Erta Ale, que tem estado em constante erupção há mais de meio século.

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Fenda vai dividir África em dois e formar um oceano no meio. Mas não será nem no tempo dos nossos bisnetos

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Cientistas acreditam que daqui a cerca de cinco milhões de anos África não será um continente, mas dois. Forte atividade vulcânica contribui para aumentar o tamanho de uma fenda que não se vê em toda a sua extensão, mas que não pára de crescer

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O oceano Atlântico está a ficar maior - continuação

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O oceano Atlântico está a ficar maior - continuação

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Isto deve-se a uma pequena zona de transição no manto, onde as ondas S ou secundárias (fazem parte das ondas internas, juntamente com as ondas P ou primárias  e, são as primeiras a serem registadas pelos sismógrafos - neste caso as ondas S, são as mais lentas e só se propagam em meios sólidos, com um tipo de onda transversal) percorrem-no mais lentamente. Na sequência disto, a velocidade das ondas sísmicas na transição desta dorsal para o fundo oceânico é mais lenta. Estas observações permitiram concluir que o material (magma) é transferido do manto inferior para o superior.

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Geological Phenomenon Widening the Atlantic Ocean

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O sismo deu-se pelas 09h51 no dia 17 de março de 2021 e foi registado nas estações de Rede Sísmica do Continente com uma magnitude de 3.4, na escala de Richter, e de grau IV na escala de Mercalli, com o epicentro a cerca de 8 km a Este de Loures.

Um sismo é um fenómeno natural que resulta de uma rotura no interior da Crosta Terrestre, devido à libertação de energia. Geralmente, este fenómeno acontece devido ao choque entre placas tectónicas, criando assim ondas sísmicas.

Os sismos são medidos por observação de sismógrafos e a escala utilizada mais frequente para medir a sua magnitude é a escala de Richter, que classifica a sua intensidade entre 1 a 9.

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Sismo em Lisboa sentido em várias zonas da cidade

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De acordo com o Instituto Português do Mar e da Atmosfera, pelas "09h51 foi registado nas estações da Rede Sísmica do Continente um sismo de magnitude 3.4 (Richter) cujo epicentro se localizou a cerca de 8 km a Este de Loures" a uma profundidade de 9 quilómetros.

Diz ainda o IPMA que "o sismo, de acordo com a informação disponível até ao momento, foi sentido com intensidade máxima III/IV (escala de Mercalli modificada) na região de Lisboa".

No Twitter, dezenas de pessoas relatam que sentiram a terra a tremer durante alguns segundos.

Achei que fosse meu gato se coçando loucamente no sofá mas foi mesmo um mini tremor de terra em Lisboa pra começar o dia
- Lucas Sobral (@luhnatico) March 18, 2021

quem sentiu Tremor Terra Lisboa?? Estou em São Domingos de Benfica, forte!
- Lígia Morais (@GiLia) March 18, 2021

Não há qualquer indicação de estragos provocados pelo sismo desta manhã. À Agência Lusa, o Comando Distrital de Operações de Socorro (CDOS) de Lisboa indicou, pouco depois das 10:00, não ter registo de ocorrências associadas a este sismo.

Há relatos de que o abalo foi sentido em vários concelhos da Grande Lisboa, como Loures, Odivelas, Cascais, Amadora e Sintra.

Os sismos são classificados segundo a sua magnitude como micro (menos de 2,0), muito pequeno (2,0-2,9), pequeno (3,0-3,9), ligeiro (4,0-4,9), moderado (5,0-5,9), forte (6,0-6,9), grande (7,0-7,9), importante (8,0-8,9), excecional (9,0-9,9) e extremo (superior a 10).

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Sismo em Lisboa sentido em várias zonas da cidade

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De acordo com o Instituto Português do Mar e da Atmosfera, pelas "09h51 foi registado nas estações da Rede Sísmica do Continente um sismo de magnitude 3.4 (Richter) cujo epicentro se localizou a cerca de 8 km a Este de Loures" a uma profundidade de 9 quilómetros.

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Relatos afirmam que o abalo foi
sentido em vários concelhos da Grande Lisboa, como Sintra, Loures, Odivelas, Cascais e Amadora.
Não houve quaisquer indicações de estragos nem de ocorrências provocados pelo sismo.

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Alerta tsunami após sismo de magnitude 7,2

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Alerta tsunami após sismo de magnitude 7,2

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Neste sábado o nordeste do Japão foi atingido por um sismo de magnitude 7,2 da escala de richter.
Ocorreu ás 18h09 locais (9h09 em Lisboa) perto da costa Miyagi, a uma profundidade de 60 quilómetros do Oceano Pacífico.
Logo após o abalo foi emitido um alerta tsunami.
Mas porque razão foi emitido esse alerta? Para quem não sabe o tsunami é uma série de ondas causadas pelo deslocamento de um grande volume de um corpo de água.
Por esse motivo após o sismo verificou-se uma subida do mar em cerca de um metro originando o tsunami.
Não há relatos de danos provocados pelo sismo e pelo tsunami em Miyagi.

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Alerta de tsunami foi emitido para a prefeitura de Miyagi. Actividade em várias centrais nucleares foi interrompida por precaução, mas empresas de energia não detectaram quaisquer anomalias.

Um sismo de magnitude 7,2 na escala de Richter abalou este sábado o nordeste do Japão, por volta das 18h26 locais (9h26 em Portugal).

As autoridades japonesas emitiram um alerta de tsunami ​, entretanto levantado, devido a uma subida do nível do mar de cerca de um metro junto à costa de Miyagi. Não foram, no entanto, registadas mais ocorrências na região nordeste do arquipélago.

As cidades de Shichigahama e Watari foram evacuadas pelas autoridades, com cerca de 25 mil pessoas a terem de ser deslocadas, sendo que a restante população da região foi aconselhada a evitar aproximar-se do mar.

Segundo a Agência Meteorológica do Japão, o hipocentro está localizado a uma profundidade de 60 quilómetros. O sismo atingiu o valor 5 na escala de Shindo, utilizada no Japão para medir a intensidade dos sismos - no sismo de 2011, foi medida uma intensidade 7, o valor máximo.

Fonte da Agência Meteorológica do Japão adiantou aos jornalistas que o abalo deste sábado é mais uma réplica do sismo de magnitude 9 que devastou a região há dez anos. Um sismo de magnitude 7,3 na escala de Richter registado em Fevereiro, que deixou quase um milhão de pessoas na zona de Fukushima, foi a última réplica registada do abalo de 2011.

A companhia de electricidade Tohoku Electric Power suspendeu a actividade na central nuclear de Onagawa para verificar se existia alguma irregularidade, sem que tenham sido encontrados problemas.

A Tokyo Electric Power também já anunciou que não houve anomalias na central nuclear de Fukushima, destruída pelo sismo, seguido de tsunami, de Março de 2011.

Parte da prefeitura de Miyagi ficou sem electricidade na sequência do sismo, de acordo com a Tohoku Electric Power. O sismo foi sentido em várias regiões da ilha do Japão, incluindo na capital do país, Tóquio, a cerca de 400 quilómetros do epicentro.

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Levantado alerta de "tsunami" no Japão, depois de sismo de magnitude 7,2

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Alerta de tsunami foi emitido para a prefeitura de Miyagi. Actividade em várias centrais nucleares foi interrompida por precaução, mas empresas de energia não detectaram quaisquer anomalias. Um sismo de magnitude 7,2 na escala de Richter abalou este sábado o nordeste do Japão, por volta das 18h26 locais (9h26 em Portugal).