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What continent do you live on? North America? Africa? Asia? Australia? Europe? South America? Would you believe that those continents used to be one of ?

That's what scientists believe. They think that, about 270 million years ago, almost all of the on Earth was part of one supercontinent . Today, scientists refer to that former supercontinent as , which comes from a Greek word that means "all the Earth."

covered about one-third of Earth's surface. So what took up the other two-thirds of Earth's surface? was surrounded by a worldwide called Panthalassa.

Scientists theorize that began to split apart around 200 million years ago. Over time, the separate pieces drifted farther and farther apart, creating the continents we know today. The movement of the continents also created the Atlantic and Indian Oceans.

Of course, we don't have any records or photographs from that long ago. So the existence of is just a . In fact, it was German meteorologist Alfred Wegener who first proposed the idea of way back in 1912 as part of his theories about how continents drift.

Wegener's theories have since been replaced by a more modern understanding of plate . Scientists, who have studied how the floor spreads apart, believe that broke apart slowly in several stages rather than all at once.

Scientists who have studied plate think that wasn't the only supercontinent in Earth's past. Modern theories hold that a supercontinent called Rodinia existed a billion years ago and another supercontinent named Pannotia formed about 600 million years ago.

Plate tectonic theories tell scientists that the Earth's crust is made up of various plates that continue to move even today. For example, scientists believe the continents are moving together again, albeit extremely slowly.

Followers of plate tectonic theories believe Africa is colliding with southern Europe and Australia is colliding with Southeast Asia. A new could form within the next 50 million years when Africa and Australia merge with Europe and Asia! This and subsequent break-up of Earth's landmasses is known as the supercontinent or Wegenerian cycle.

How do scientists know all this? They make educated guesses about what might have happened of years ago based upon evidence they find today. For example, scientists have found from identical species on continents that are now far apart.

Geological evidence also gives scientists clues as to how formed and subsequently broke apart. For example, scientists have found matching geological trends on both the eastern coast of South America and the western coast of Africa, leading them to believe these two landmasses must have been joined together at one time.

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What continent do you live on? North America? Africa? Asia? Australia? Europe? South America? Would you believe that those continents used to be one of ? That's what scientists believe. They think that, about 270 million years ago, almost all of the on Earth was part of one supercontinent .

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What's beneath your feet right now? Carpet? Tile? A concrete sidewalk? Grass, dirt, and leaves? No matter what you're standing on right now, you're standing at the tip of the iceberg, so to speak. Whether you realize it or not, there are thousands of miles of Earth below your feet made up of all sorts of materials, including , , rivers of water, , and solid iron to name just a few.

If you've ever dug a hole in your backyard, you know that digging can be a lot of work. It can be fun, though, to see what lies below the . Your hole probably consisted mainly of dirt and possibly a few rocks along the way.

The deeper you dig, the harder it is to see to the bottom of the hole you're digging. Unless you climb down into the hole, it also gets harder to dig the deeper you go. That's why people who dig holes for a living, such as coal mines and water wells , use specialized equipment that allows them to dig really deep holes.

Even the deepest coal mines and water wells , though, barely scratch the of what lies beneath Earth's outer layer, called the crust. Below the crust lies the , which is semi-solid and consists of and magma that moves about.

Below the , you'll find Earth's , which is made up of two parts. There is a liquid outer that surrounds a solid inner . Scientists believe the solid inner is a solid ball of iron and that's under a lot of . How much ? Try about 9 million times the atmospheric humans experience at sea level on Earth's .

All that keeps the metal in the inner in solid form, despite its extremely high temperature. Recent scientific studies lead experts to believe that Earth's inner is approximately 10,800º F - or about the same temperature as the of the Sun!

But how do scientists know how hot Earth's is? They can't see it. They can't dig down deep enough to use a thermometer to measure its temperature. Despite the fact it's right under our feet, Earth's is maddeningly inaccessible .

Earth's is about the size of Pluto. Given the thousands of miles of and other materials that separate those of us on the from the , it might as well be as far away as Pluto! How can we really know anything about it?

Modern scientists have come up with ways to study Earth's layers. Geologists, for example, have long used waves to learn about what lies below Earth's . waves are the types of waves produced by earthquakes and other tectonic plate movements that occur below Earth's .

By measuring waves, scientists can learn a lot about the composition of Earth's subsurface layers. Because the layers are made up of different materials that vary in thickness, researchers are able to analyze the ways in which waves bounce off the boundaries between various layers. waves travel through in much the same way that sound waves travel through air.

As for Earth's , scientists believe it's made mostly of iron because of the magnetic field that exists around Earth. Using advanced technology, scientists have been able to pinpoint with greater specificity the exact melting point of iron, which allows them to make educated guesses about the temperatures that must exist in Earth's inner and outer cores.

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How Do We Know the Temperature of Earth's Core?

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What's beneath your feet right now? Carpet? Tile? A concrete sidewalk? Grass, dirt, and leaves? No matter what you're standing on right now, you're standing at the tip of the iceberg, so to speak.

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Today's Wonder of the Day was inspired by melonie from morris , NY. melonie Wonders, " why there are earthquakes? " Thanks for WONDERing with us, melonie!

Unlike the on our bodies, though, this on the Earth is not all in one piece. Instead, it consists of many pieces that fit together a bit like a jigsaw .

Scientists call these pieces plates. plates differ from jigsaw pieces in that they constantly but slowly move around, sliding past and/or bumping into one another.

The edges of the plates are called boundaries. The rough boundaries occasionally get stuck, but the rest of the plates keep moving.

When a moves far enough, its edges break free along an area called a . When two plates slip past one another , the people who live in the area close to the experience an earthquake .

The spot on the of the Earth directly above where the earthquake occurs underground is called the of the earthquake . After an earthquake , there are often smaller earthquakes - called aftershocks - that occur in the same place. These aftershocks have been known to continue for weeks, months, and even years after the main earthquake .

Earthquakes can be very destructive. The sudden motion of plates can cause injuries and serious property damage, especially because there is often little or no advance warning of earthquakes.

When boundaries become stuck, their usual energy from motion is stored and builds up until, during an earthquake , it is released in the form of waves that radiate outward from a in all directions. As these waves reach the of the Earth, they shake the ground and everything on it.

If you ever experience an earthquake firsthand, it's important to remember and follow a few safety tips:

Get low and take cover under a protective object, such as a sturdy table or desk.

Hold on and try to stay as steady as possible.

Stay inside until the earthquake ends.

Stay away from windows, furniture, and other items that could fall on you.

If you're in bed, stay there and protect your head with your pillow.

If you're outside, move to a clear spot away from buildings, trees, and power lines.

If you're in a car, slow down and stop in a clear area until the earthquake stops.

Take earthquake safety seriously! Scientists estimate that there are 500,000 detectable earthquakes in the world each year. Of these, approximately 100,000 of them can be felt, and at least 100 of them cause some kind of damage.

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Today's Wonder of the Day was inspired by melonie from morris , NY. melonie Wonders, " why there are earthquakes? " Thanks for WONDERing with us, melonie! Unlike the on our bodies, though, this on the Earth is not all in one piece.

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Stop! The ground is hot ! Have you ever shouted those words on the playground? Many kids love to pretend that the ground is covered in hot , forcing them to hop around or swing through the air on the monkey bars to avoid a certain death from falling into the .

While it's fun to pretend, real hot is fairly easy to avoid, since it usually moves quite slowly. It is very hot, though. If you were to fall into hot , it would not be a pleasant experience. Your skin would be melted and burned by that can approach temperatures well over 2,000º F!

is molten . It is created deep beneath Earth's surface (often 100 miles or more underground), where temperatures get hot enough to . Scientists call this molten when it's underground.

Eventually, some makes its way to Earth's surface and escapes via a volcanic eruption. When erupts onto Earth's surface and begins to , scientists then call it . Explosive eruptions can throw great distances. Most eruptions, however, create slow-moving flows that might cover only a few yards per minute at the most.

Deep below Earth's surface, the most common type of produced is . makes up much of the ocean floor, and it's also the substance most often seen when Hawaiian volcanoes . When it reaches Earth's surface, it erupts as basaltic .

If you were a in a cartoon and you wanted to take over the world, hot might be a good weapon to have in your . However, it can be very difficult to the power of a . Is there any way that you could create your own ?

It's not like you could throw some rocks in your and them into . The in your kitchen at home simply doesn't produce enough heat. Of course, if you were a in a cartoon, you might have lasers or some other trick up your sleeve.

Though it might sound far-fetched, humans have actually made their own without the assistance of a . Scientists and students at Syracuse University, who are part of the Syracuse University Project (and NOT villains of any sort!), have successfully used industrial furnaces to chunks of crushed from Wisconsin to create their own !

Once created, the is poured onto a thick slab of solid ice to create a up to a few yards long. Faculty, students, and even interested members of the public are invited to enjoy the up close.

The main goal of making the is to conduct scientific experiments to study basaltic . Usually, scientists can only eruptions, which happen only occasionally and usually without warning. Creating allows them to conduct controlled experiments like never before.

In between experiments, however, kids are often allowed to roast hot dogs and marshmallows over the hot . Beyond the scientific purposes of the , art students have also been allowed to use molds to create fascinating sculptures.

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Stop! The ground is hot ! Have you ever shouted those words on the playground? Many kids love to pretend that the ground is covered in hot , forcing them to hop around or swing through the air on the monkey bars to avoid a certain death from falling into the .

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Today's Wonder of the Day was inspired by Jaye. Jaye Wonders, " How hot does lava get? " Thanks for WONDERing with us, Jaye!

Volcanoes are like huge valves that from deep inside Earth. When they , they remind us of how the forces are that continually reshape Earth.

Deep inside Earth (90 miles or more), temperatures get hot enough to melt rock. This rock is called . When it , it begins to float toward the surface of Earth.

If it breaks through Earth's surface, it is then called lava. Although lava can be into the air through a volcanic eruption, it's more common for lava to flow from a through cracks called fissures.

Lava is made up of mostly silicon and oxygen. As lava escapes and travels before cooling, it often mixes with other elements, such as iron, magnesium, potassium, and calcium.

When lava first breaks through Earth's surface, it is an hot . On average, fresh lava can be between 1,300° F and 2,200° F (700° and 1,200° C)! Depending on its exact temperature , fresh lava usually glows either orange/red (cooler) or white (hotter).

Eventually, lava cools and returns to solid rock again. However, some forms of lava can flow great distances before cooling enough to . The word lava comes from the Italian word for "stream."

Although popular movies may make you worry about the deadly power of lava flows, they usually move slowly enough to give people plenty of time to get out of the way. It's for anyone to die as a direct result of a lava flow, but it can be to land and property in its path.

Active lava flows at volcanoes might move several feet per minute when hot. As the lava flows cool, they slow down to a rate of only a few feet per day.

Geologists in Hawaii keep a close watch on active lava flows. They use handheld global positioning system (GPS) receivers to map lava flows as accurately as possible.

The GPS receivers use radio waves from satellites orbiting Earth to pinpoint locations within 15 feet. In this way, geologists can monitor lava flows that may be advancing toward areas where people live.

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Today's Wonder of the Day was inspired by Jaye. Jaye Wonders, " How hot does lava get? " Thanks for WONDERing with us, Jaye! Volcanoes are like huge valves that from deep inside Earth. When they , they remind us of how the forces are that continually reshape Earth.

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Today's Wonder of the Day was inspired by braden from AL. braden Wonders, " How are volcanoes formed!?!? " Thanks for WONDERing with us, braden!

The Earth consists of three layers. The outer layer of Earth we live on is called the . It's about 18 miles thick.

Below the lies an 1,800-mile thick layer called the . A combination of rock and gases called lies between the Earth's and the . The innermost layer is called the .

A is a mountain that extends down to a pool of between the and . It's basically a hole in the Earth from which can . The name "" comes from the name of Vulcan, a god of fire in Roman mythology.

Volcanoes are like huge safety valves that release the that builds up inside the Earth. When builds up, eruptions occur. shoots up through the and flows down its sides. When flows out of a , we call it . Fresh can be as hot as 2,200° F, glowing red or white as it flows.

Eruptions can cause mudslides, avalanches, and floods. eruptions have knocked down entire forests and triggered tsunamis and earthquakes.

As they , volcanoes spew huge clouds of volcanic ash into the atmosphere. The ash consists of tiny bits of rock and glass. Ash clouds can cover hundreds of miles, creating problems for airplanes and changing weather patterns. Volcanic ash can also damage the lungs and cause other respiratory problems for those who breathe it.

The United States contains several active volcanoes, mainly in Hawaii, Alaska, California, Oregon, and Washington. Hawaii and Alaska have the greatest chance of experiencing eruptions near areas where many people live.

Here are some interesting facts you may not know about volcanoes:

Historical records exist for almost 600 volcanoes around the world, while some scientists believe there are over 1,500 active volcanoes! No one really knows for sure how many volcanoes exist under the oceans.

Over half of the world's volcanoes arise in a belt around the Pacific Ocean called the Ring of Fire.

On any particular day, approximately 20 volcanoes are in the process of erupting.

The "danger zone" of a extends for up to 20 miles in all directions.

On May 18, 1980, Mount St. Helens erupted in Washington, killing 58 people and causing over $1 billion in property damage.

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Today's Wonder of the Day was inspired by braden from AL. braden Wonders, " How are volcanoes formed!?!? " Thanks for WONDERing with us, braden! The Earth consists of three layers. The outer layer of Earth we live on is called the . It's about 18 miles thick.

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Have you ever seen a explode? If so, we hope you weren't anywhere near it! Volcanic eruptions can be catastrophic events that cover the landscape for miles in hot and . If you're like most people, you've probably only seen video of previous volcanic eruptions.

If you had the chance to explore the inside of a , would you do it? What do you think you'd find? Not all volcanoes are active. In fact, most of them are and present no particular danger of eruption anytime in the near future.

Seismologists and other scientists often study these volcanoes in order to learn more about how they work. For example, scientists in Iceland have descended into the of some volcanoes to explore their chambers to see what they're made of and how they contributed to past eruptions.

When escapes through a onto Earth's surface, scientists call it . When it cools enough to turn back into a , scientists call it . When it's under Earth's surface, it exists as a dynamic, substance that ranges in temperature from approximately 1,300º F to almost 2,400º F.

tends to be less dense than the layers of it forms in. As a result, it moves upward toward Earth's surface via any path it can find. When it reaches an area where layers don't allow an upward path, it will collect in a large pool that scientists call a .

Many chambers exist deep under Earth's surface, making them extremely hard to detect. Most of the chambers scientists have identified are very close to Earth's surface. For example, chambers under active volcanoes might be as close as 1-5 miles below Earth's surface. While this sounds very deep, it's extremely close in geological terms, especially when you think about the distance to Earth's core.

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Have you ever seen a explode? If so, we hope you weren't anywhere near it! Volcanic eruptions can be catastrophic events that cover the landscape for miles in hot and . If you're like most people, you've probably only seen video of previous volcanic eruptions.

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Today's Wonder of the Day was inspired by Victor from AL. Victor Wonders, " what are the physical and chemical properties of the mantle? " Thanks for WONDERing with us, Victor!

What's under your feet? Depending upon where you're currently standing, it could be dirt, rock, or grass. But what's really under your feet? If you were to dig straight down, what would you find? And how far could you dig? Could you really dig a hole to China?

Scientists who study Earth and its composition will tell you that Earth is made up of three main layers. We human beings live on the outer layer called the .

Under the lies the , which is made up of hot and other semi- rocks and minerals. activity in the often results in noticeable changes in the we live on, including volcanic eruptions and earthquakes.

Beneath the , you'll find the . Earth's is the , hottest layer, and it's made up of two layers itself: the outer which borders the and the inner , which is a ball-shaped layer made almost entirely of metal.

The outer is about 1,400 miles , and it's made mostly of a combination (called an ) of and , along with small amounts of other elements like gold, platinum, and . These metals can, of course, be found on the surface of Earth in form. In the outer , they're in a very hot form. How hot? Try between 7,000-9,000º F!

The inner , which is about 750 miles , is made of . Unlike the outer , the inner is mostly . Although the in the inner is even hotter (10,000º F or more - as hot as the surface of the Sun!) than the outer , the intense pressure from the rest of the planet is so great that the cannot melt.

Billions of years ago when Earth was formed, all the heaviest substances sank toward the middle of the developing planet. Lighter, less substances stayed closer to the . That's why the inner is comprised of some of the heaviest materials on Earth.

With a ball of metal as its , all of Earth is magnetic. Scientists believe Earth's powerful magnetic field is controlled by the outer . Earth's magnetic field protects us from all sorts of charged particles floating around the solar system, including many of the Sun's harmful rays.

Although it might be hard to imagine. scientists believe the metals in Earth's are in constant motion. Some scientists even believe Earth's inner rotates faster than the rest of the planet. Movement within Earth's outer occasionally changes the location of Earth's magnetic North and South Poles.

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Today's Wonder of the Day was inspired by Victor from AL. Victor Wonders, " what are the physical and chemical properties of the mantle? " Thanks for WONDERing with us, Victor! What's under your feet? Depending upon where you're currently standing, it could be dirt, rock, or grass.

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Isn't there just something so comfortable about the ground under your feet? After all, part of the thrill of sports like ice skating and roller skating is the slightly out-of-control feeling you get when you're sliding (or rolling) along.

But what if the ground under your feet wasn't so ? What if it moved and shook and tossed you about like a rag doll? That's what some people experience from time to time when the earth under their feet shifts and unexpectedly . What are we talking about? Earthquakes, of course!

Although the ground seems extremely , it's actually made up of pieces of rock that slowly, but constantly move. These pieces of Earth's crust - what scientists call plates - collide with and rub against one another.

Every once in a while, the edges of plates will break or slip , releasing bursts of in the form of earthquakes. In fact, earthquakes happen constantly, every day, all around the world.

Many earthquakes are just too small to be felt by our senses. However, the U.S. Geological estimates that as many as 1.3 million earthquakes that can be felt by humans may occur each and every year!

Occasionally, large earthquakes will occur, releasing in the form of waves more powerful than thousands of atomic bombs. When this happens, the results can be devastating. For example, a powerful earthquake off the coast of Japan in 2011 damaged thousands of buildings and caused the deaths of over 20,000 people.

Earthquakes have been around since the beginning of time. Scientists have really only begun to understand and measure them in the last 100 years or so, though. Today, scientists around the world use sophisticated monitoring equipment to detect and measure earthquakes. One day, they may be able to use that information to predict when major earthquakes are likely to occur.

Scientists who study earthquakes - called seismologists - concentrate on areas of Earth's crust where plates are moving in different directions. They call these areas lines. By studying lines, they hope to understand earthquakes better and learn to predict when they might occur.

Seismologists have learned that most earthquakes occur along established lines. Groups of lines combine to form zones. Some of the most extensive and active zones are given names, such as the San Andreas in California and the New Madrid that extends over 120 miles through several Midwestern states, including Illinois, Missouri and Arkansas.

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Isn't there just something so comfortable about the ground under your feet? After all, part of the thrill of sports like ice skating and roller skating is the slightly out-of-control feeling you get when you're sliding (or rolling) along. But what if the ground under your feet wasn't so ?

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If you've ever taken a bath or swum in a lake or pool, you've probably enjoyed creating your own waves. Unlike solid objects, water is and easy to move around. The harder you push with your hands, the bigger the waves will be.

Now imagine what happens in the ocean when an earthquake occurs underground. If you've ever felt an earthquake or seen one on television, you know that they have the power to shake the ground and move large buildings.

When an earthquake occurs under the ocean floor, the earthquake 's massive energy is transferred to the water above it, creating a series of water waves called a . The word comes from the Japanese words tsu (harbor) and nami (wave).

In addition to earthquakes, tsunamis can be caused by other events that generate enough energy to displace a large volume of water, such as eruptions, landslides, meteors, and even underwater tests of devices. Given the frequent earthquake and activity in the Pacific Rim, tsunamis happen often in Japan.

Tragically, because of the huge amounts of water and energy involved, tsunamis can cause tremendous damage to coastal areas. On December 26, 2004, a massive earthquake in the Indian Ocean caused a series of devastating tsunamis along the coasts of the areas bordering the Indian Ocean. One of the deadliest natural disasters in history, waves up to 100 feet high crashed into coastal communities, killing over 230,000 people in 14 countries, including Indonesia, Sri Lanka, India, and Thailand.

You may recall the earthquake and that occurred in Japan on March 11, 2011. That resulted in mass destruction including a power plant that released into the Pacific Ocean.

Normal ocean waves created by the wind have an average wavelength (measured from crest to crest) of approximately 330 feet and an average height of about 6.6 feet. A , on the other hand, can have a wavelength of 120 miles or more. Traveling at up to 500 miles per hour in the deep ocean, a 's height might only be as little as 3 feet, making it almost impossible to detect, even for a ship in the area.

As a approaches a , though, things begin to change dramatically. As it approaches shallow waters, an effect known as wave shoaling compresses and slows the wave to below 50 miles per hour. Wavelength also decreases dramatically, but - the height of the wave - increases greatly, leading to the unmistakable wall of water that causes such destruction along coastlines.

Approximately 80% of tsunamis happen in the Pacific Ocean, although they're possible in any large body of water, including lakes. Tsunamis cannot be prevented and can rarely be predicted with . In the event of an earthquake , oceanographers, geologists, and seismologists often urge potentially-affected areas to issue warnings.

Regions that experience tsunamis regularly have developed warning systems to give as much advance warning as possible to people who live along the . In Japan, for example, coastal communities are well-educated about earthquakes and tsunamis. Japanese shorelines feature warning signs and warning sirens atop nearby hills.

Although tsunamis cannot be prevented, some - countries use engineering lessons learned from earthquakes to reduce shoreline damage. Many Japanese coastal communities have built walls, floodgates, and channels to block or redirect water from incoming tsunamis.

One of the best ways to make a coast -proof, though, is quite natural: plant trees! Scientists noticed that some locations in the path of the 2004 Indian Ocean suffered little damage because trees, such as coconut palms and mangroves, absorbed the 's energy. In fact, one small Indian village saw little damage because the broke against a forest of over 80,000 trees that had been planted along the shoreline just two years earlier in an attempt to set a Guinness World Record.

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If you've ever taken a bath or swum in a lake or pool, you've probably enjoyed creating your own waves. Unlike solid objects, water is and easy to move around. The harder you push with your hands, the bigger the waves will be. Now imagine what happens in the ocean when an earthquake occurs underground.