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Volcano videos if you would like to learn and explore more

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Volcano videos if you would like to learn and explore more

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At first it may seem odd that people would want to live close to a volcano. After all, volcanoes have a nasty habit of exploding, discharging liquid rock, ash, poisonous gasses, red hot clouds of embers, and generally doing things that kill people. Yet, throughout history, people have deliberately chosen to risk all those hazards and live near them, even on the slopes of active volcanoes that have erupted within living memory.

They chose to live close to volcanoes because they felt that the advantages outweighed the disadvantages. Most volcanoes are perfectly safe for long periods in between eruptions, and those that do erupt more frequently are usually thought of, by the people who live there, as being predictable.

Today, about 500 million people live on or close to volcanoes. We even have major cities close to active volcanoes. Popocatapetl (pronounced poh-poh-kah-teh-peh-til) is a volcanic mountain less than 50 miles from Mexico City in Mexico.

In short, the main things that attract people to live near active volcanoes are minerals, geothermal energy, fertile soils and tourism.

Lets look at each one...

Minerals
Magna rising from deep inside the earth contains a range of minerals. As the rock cools, minerals are precipitated out and, due to processes like the movement of superheated water and gasses through the rock, different minerals are precipitated at different locations. This means that minerals such as tin, silver, gold, copper and even diamonds can be found in volcanic rocks. Most of the metallic minerals mined around the world, particularly copper, gold, silver, lead and zinc are associated with rocks found deep below extinct volcanoes. This makes the areas ideal for both large scale commercial mining and smaller scale local activities by individuals and small groups of locals. Active and dormant volcanoes have the same mineralisation, so like extinct volcanoes, they are rich sources of minerals.
Hot gasses escaping through vents also bring minerals to the surface, notably sulphur, which collects around the vents as it condenses and solidifies. Locals collect the sulphur and sell it.

Geothermal Energy

Geothermal energy means heat energy from the earth. It's unusual to use the heat directly, by building your house on top of a steam vent for example, because it's unpredictable, dangerous and messy.

The heat from underground steam is used to drive turbines and produce electricity, or to heat water supplies that are then used to provide household heating and hot water. Where steam doesn't naturally occur it is possible to drill several deep holes into very hot rocks, pump cool water down one hole and extract steam from another hole close by.

The steam isn't used directly because it contains too many dissolved minerals that could precipitate out and clog pipes, corrode metal components and possibly poison the water supply.

Countries such as Iceland make extensive use of geothermal power, with approximately two thirds of Iceland's electricity coming from steam powered turbines. New Zealand and to a lesser extent, Japan, also make effective use of geothermal energy.

Fertile Soils

Volcanic rocks are rich in minerals, but when the rocks are fresh the minerals are not available to plants. The rocks need thousands of years to become weathered and broken down before they form rich soils. When they do become soils though, they form some of the richest ones on the planet. Places such as the African Rift Valley, Mt Elgon in Uganda, and the slopes of Vesuvius in Italy all have productive soils thanks to the breaking down of volcanic rocks and ash. The Naples area, which includes Mount Vesuvius, has such rich soils thanks to two large eruptions 35,000 and 12000 years ago. Both eruptions produced very thick deposits of ash and broken rocks which have weathered to rich soils. Today, the area is intensively cultivated and produces grapes,vegetables, orange and lemon trees, herbs, flowers and has become a major tomato growing region.

Tourism

Volcanoes attract millions of visitors every year, for different reasons. As an example of the wilder side of nature, there are few things that can beat seeing an erupting volcano blowing red hot ash and rock thousands of feet into the air. Even the less active ones that are just puffing out steam and smoke are impressive sights and attract tourists from around the world.

Around the volcano may be warm bathing lakes, hot springs, bubbling mud pools and steam vents. Geysers are always popular tourist attractions, such as Old Faithful in the Yellowstone National Park, USA. Old Faithful is such a popular tourist feature that it even has its own 24 hour Old Faithful webcam.

Iceland markets itself as a land of fire and ice, attracting tourists with a mix of volcanoes and glaciers, often both in the same place. The wild, raw and barren volcanic landscapes also attract tourists who want to see what the early planet may have looked like.

Tourism creates jobs in shops, restaurants,hotels and tourist centres / national parks. Locals economies can profit from volcanism throughout the year, whereas skiing, for example, has only a limited winter season.

In Uganda, a country trying hard to increase its tourist industry, the volcanic region around Mt Elgon is being heavily promoted for it's landscape,huge waterfalls, wildlife, climbing and hiking and its remote 'get away from it all' location.

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Geography Site: Why do people live near volcanoes

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At first it may seem odd that people would want to live close to a volcano. After all, volcanoes have a nasty habit of exploding, discharging liquid rock, ash, poisonous gasses, red hot clouds of embers, and generally doing things that kill people.

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The ghost-like casts from the Roman city of Pompeii are a reminder of the lethal eruption of Mount Vesuvius in AD79, which killed thousands and preserved their bodies in the position of their death. But it wasn't red-hot lava or suffocating clouds of ash that killed them, it was something far more unusual. Lava flows, or the molten rock that oozes from shield volcanoes moves far too slowly to be truly deadly. The real killers are much more frightening.

Here are four ways a volcano can kill:

The Roman cities of Pompeii and Herculaneum were annihilated on 24 August AD79 when Mount Vesuvius erupted explosively, sending fast-moving waves of superheated gas down the sides of the volcano at hurricane speeds. These 'pyroclastic flows' contain gas, ash and rock and can travel up to 450mph (700km/h).

The first wave hit the nearby Herculaneum with temperatures as high as 500 degrees Celsius. The searing heat was enough to boil the brains and instantly vaporise the flesh of its victims so that only blackened skeletons remained.

But how the people of Pompeii died has remained a mystery for many centuries. Volcanologists have now discovered they were killed by a later wave of pyroclastic flow.

Pompeii's wave was significantly cooler than the one that swept through Herculaneum, so although the victims bodies remained intact, the heat 'cooked' their flesh instantly. They were preserved by the falling volcanic ash and some of these can still be seen in Pompeii today.

Pyroclastic flows are arguably the most deadly volcanic event because they can travel for miles and are impossible to outrun.

They are produced by explosive 'composite volcanoes', which are made up of alternating layers of lava, ash and rock. When a composite volcano erupts, the rock layer is smashed into tiny dust particles. These particles mix with the hot ash and gases to form a giant mushroom cloud.

As the eruption weakens, this cloud can collapse under its own weight. It then cascades down the side of the volcano as a pyroclastic flow - destroying everything in its path. But that's not the only way they can cause big problems...
How devastating could the next Mount Vesuvius eruption be?
In Colombia, 1985, a volcano called Nevado del Ruiz erupted. As pyroclastic flows exploded from the volcano they melted the glaciers on the mountain.

The melted water mixed with the volcanic ash, mud and rock, causing four enormous hot 'lahars' to speed down the mountain at 40mph (60km/h).

Lahars are concrete-thick mixtures of mud and water that slide down mountains like avalanches. They can be extremely destructive because they travel with enough force to carry huge boulders at high speeds for up to 50 miles (80 km).

The lahars from Nevado del Ruiz flowed into the six major rivers at the base of the volcano before engulfing the town of Armero - killing more than 20,000 of the people that lived there.

Pyroclastic flows and lahars are dramatic events, yet volcanoes can also be silent killers.

When a volcano sits beneath a lake, gases from the magma can filter through cracks in the Earth and become trapped under the water as carbon dioxide.

Violent movement, from an earthquake or landslide for example, can cause the carbon dioxide to rise rapidly to the surface of the lake - a rare but deadly event called a 'limnic' eruption.

One of only two limnic eruptions ever recorded happened in Cameroon in 1986. A landslide disturbed a deep lake called Lake Nyos which sat within the crater of an inactive volcano.

More than 80 million cubic metres of carbon dioxide was released and surged into nearby villages; suffocating more than 1,700 people and thousands of animals and livestock.
Hear a survivor's account of the Lake Nyos disaster
Poisonous volcanic gases, lahars and pyroclastic flows are deadly to almost anyone who gets in their way. But the devastating effects of a volcanic eruption can be even more far reaching.

In the Philippines in 1991, Mount Pinatubo exploded in a cataclysmic eruption, blasting 22 million tonnes of ash particles and sulphur dioxide 12 miles (19 km) into the atmosphere. Fierce winds from a passing typhoon blew the ash in all directions before it fell like thick snow on nearby buildings. Many roofs collapsed under the sheer weight; killing 300 people in their homes.

Explosive eruptions like this are so powerful that lightweight ash particles can be lifted as high as the lower stratosphere by convection currents. When ash and volcanic gases spread across the globe after Mount Pinatubo's eruption, they reflected some of the Sun's radiation back into space.

This caused the global temperature to drop by 0.6 degrees Celsius. The cooling effect only lasted for two years. But some scientists think that volcanic activity like this may have caused a change in climate which contributed to the Permian mass extinction - an event which saw a staggering 96% of all the species on Earth perish.

Could a new giant volcanic eruption produce enough ash and gas to trigger extreme climate change that might threaten all life on Earth?
Did volcanoes wipe out 96% of life on Earth?

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The ghost-like casts from the Roman city of Pompeii are a reminder of the lethal eruption of Mount Vesuvius in AD79, which killed thousands and preserved their bodies in the position of their death. But it wasn't red-hot lava or suffocating clouds of ash that killed them, it was something far more unusual.

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Wider reading

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As GCSE Geographers I expect you to always be keeping an eye on the news! 

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As GCSE Geographers I expect you to always be keeping an eye on the news! 

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Visit BBC News for up-to-the-minute news, breaking news, video, audio and feature stories. BBC News provides trusted World and UK news as well as local and regional perspectives. Also entertainment, business, science, technology and health news.

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Mrs Morillon's GCSE class 2014-2016

OCR B Geography