Earth Layers

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What do you know about the inside of our planet?

In our Layers of the Earth video, you will discover some facts about the four main layers that make up our beautiful earth!

The first thing you'll learn is that the earth is not simply a giant ball of dirt, rocks, and minerals.

On the contrary, our planet is much more than meets the eye.

The crust is the outer layer of the earth and is actually between 5 and 25 miles thick depending on where you are. Under the oceans, it is only about 3 to 5 miles thick, and we refer to these areas as oceanic crust. The crust beneath the land reaches up to 25 miles thick. We refer to these parts as continental crust. The temperatures of the earth's crust can range anywhere between air temperature and 1600°F, which is hot enough to melt rocks! This thin layer consists of broken pieces called plates, which float on top of the soft mantle layer below. (The movement of these plates is what often causes earthquakes.) The mantle layer is the largest at about 1800 miles thick. It comprises extremely hot, dense rock that flows like asphalt. The temperature at the top is about 1600°F, but it's about 4000°F at the bottom! This layer is basically made up of melted rock that allow the plates of the earth's crust to float on top. The melted rock that escapes to the earth's surface lead to the creation of volcanoes. Then comes the outer core of the earth. The outer core consists mostly of melted nickel and iron. This layer lies around 1800 miles below the earth's surface and is around 1400 miles thick. The temperature ranges from 4000°F to 9000°F! The inner core is about 800 miles thick with 9000°F temperatures. There is so much pressure in the core that the metals squeeze very tightly, forcing them to vibrate as solids do. This pressure comes from the weight of the other layers that press down on it.

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In this video we will explain plate tectonics!

Together we will learn about the two main types of tectonic plates, Oceanic and Continental. We also cover the 3 kinds of boundaries which are: Convergent, Divergent, and Transform. This helps us understand exactly how the plate tectonics move AND what happens when they do. We will also learn about Pangaea and how all of the plates were once together and over millions the plate tectonics have cause the continents to separate.

Layers Of The Earth

The inner core | The outer core | The mantle | The crust

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Earth is the only planet in our solar system that has life as we know it. This is because it has a unique atmosphere and a solid surface with liquid water. Earth also has a variety of different layers, each with its own unique properties.

Starting at the center, Earth is composed of four distinct layers. They are, from deepest to shallowest, the inner core, the outer core, the mantle and the crust. Except for the crust, no one has ever explored these layers in person. In fact, the deepest humans have ever drilled is just over 12 kilometers (7.6 miles). And even that took 20 years!

Still, scientists know a great deal about Earth’s inner structure. They’ve plumbed it by studying how earthquake waves travel through the planet. The speed and behavior of these waves change as they encounter layers of different densities. Scientists — including Isaac Newton, three centuries ago — have also learned about the core and mantle from calculations of Earth’s total density, gravitational pull and magnetic field.

The inner core

This solid metal ball has a radius of 1,220 kilometers (758 miles), or about three-quarters that of the moon. It’s located some 6,400 to 5,180 kilometers (4,000 to 3,220 miles) beneath Earth’s surface. Extremely dense, it’s made mostly of iron and nickel. The inner core spins a bit faster than the rest of the planet. It’s also intensely hot: Temperatures sizzle at 5,400° Celsius (9,800° Fahrenheit). That’s almost as hot as the surface of the sun. Pressures here are immense: well over 3 million times greater than on Earth’s surface. Some research suggests there may also be an inner, inner core. It would likely consist almost entirely of ironز

The outer core

This part of the core is also made from iron and nickel, just in liquid form. It sits some 5,180 to 2,880 kilometers (3,220 to 1,790 miles) below the surface. Heated largely by the radioactive decay of the elements uranium and thorium, this liquid churns in huge, turbulent currents. That motion generates electrical currents. They, in turn, generate Earth’s magnetic field. For reasons somehow related to the outer core, Earth’s magnetic field reverses about every 200,000 to 300,000 years. Scientists are still working to understand how that happens.

The mantle

At close to 3,000 kilometers (1,865 miles) thick, this is Earth’s thickest layer. It starts a mere 30 kilometers (18.6 miles) beneath the surface. Made mostly of iron, magnesium and silicon, it is dense, hot and semi-solid (think caramel candy). Like the layer below it, this one also circulates. It just does so far more slowly.

Near its upper edges, somewhere between about 100 and 200 kilometers (62 to 124 miles) underground, the mantle’s temperature reaches the melting point of rock. Indeed, it forms a layer of partially melted rock known as the asthenosphere (As-THEEN-oh-sfeer). Geologists believe this weak, hot, slippery part of the mantle is what Earth’s tectonic plates ride upon and slide across.

Diamonds are tiny pieces of the mantle we can actually touch. Most form at depths above 200 kilometers. But rare “super-deep” diamonds may have formed as far down as 700 kilometers below the surface. These crystals are then brought to the surface in volcanic rock known as kimberlite.

The mantle’s outermost zone is relatively cool and rigid. It behaves more like the crust above it. Together, this uppermost part of the mantle layer and the crust are known as the lithosphere.

The crust

Earth’s crust is like the shell of a hard-boiled egg. It is extremely thin, cold and brittle compared to what lies below it. The crust is made of relatively light elements, especially silica, aluminum and oxygen. It’s also highly variable in its thickness. Under the oceans (and Hawaiian Islands), it may be as little as 5 kilometers thick. Beneath the continents, the crust may be 30 to 70 kilometers thick.

Along with the upper zone of the mantle, the crust is broken into big pieces, like a gigantic jigsaw puzzle. These are known as tectonic plates. These move slowly — at just 3 to 5 centimeters per year. What drives the motion of tectonic plates is still not fully understood. It may be related to heat-driven convection currents in the mantle below. Some scientists think it’s caused by the tug from slabs of crust of different densities, something called “slab pull.” In time, these plates will converge, pull apart or slide past each other. Those actions cause most earthquakes and volcanoes. It’s a slow ride, but it makes for exciting times here on Earth’s surface

Tectonic plates

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African Plate | Antarctic Plate | Eurasian Plate | Indo-Australian Plate | North American Plate

Pacific Plate | South American Plate

Where tectonic plates meet, they can be pulling away from each other, pushing towards one another or sliding past each other. These motions create mountains, earthquakes and volcanoes.

For billions of years, Earth has been remodeling itself. Huge masses of molten rock rise from deep inside Earth, cool into a solid, travel along our planet’s surface and then sink back down. The process is known as plate tectonics.

The term tectonics comes from a Greek word meaning “to build.”

Tectonic plates are huge moving slabs that together make up Earth’s outer layer. Some span thousands of kilometers on a side. In all, a dozen major plates cover Earth’s surface.

You might think of them as the cracked eggshell jacketing a hard-boiled egg. Like an eggshell, plates are relatively thin — on average only about 80 kilometers thick. But unlike an egg’s cracked shell, tectonic plates travel. They migrate atop Earth’s mantle. Think of the mantle as the thick white part of a hard-boiled egg.

Earth’s hot, liquid innards also are always in motion. That’s because warmer materials are generally less dense than cooler ones, notes geologist Mark Behn. He’s at the Woods Hole Oceanographic Institution in Massachusetts. So, hot stuff in Earth’s middle “rises up — kind of like a lava lamp,” he explains. “Once it gets back to the surface and cools off again, then it will sink back down.”

The rising of hot rock from the mantle to Earth’s surface is called upwelling. This process adds new material to tectonic plates. Over time, the cooling outer crust becomes thicker and heavier. After millions of years, the oldest, coolest parts of the plate sink back into the mantle, where they remelt again.

“It’s like a giant conveyor belt,” explains geophysicist Kerry Key at the Scripps Institution of Oceanography. It’s at the University of California, San Diego. That conveyer belt drives the movement of the plates. The plates’ average speed is about 2.5 centimeters (roughly an inch) or so per year — about as fast as your fingernails grow. Over millions of years, though, those centimeters add up.

So over eons, Earth’s surface has changed a lot. For instance, roughly 250 million years ago, Earth had one giant landmass: Pangaea. Plate movement split Pangaea into two huge continents, called Laurasia and Gondwanaland. As Earth’s plates kept moving, those landmasses each broke apart more. As they spread and traveled, they evolved into our modern continents.

Although some people mistakenly talk about “continental drift,” it’s the plates that move. Continents are just the tops of plates that rise above the ocean.

Moving plates can trigger huge impacts. “All the action is mostly at the edges,” notes Anne Egger. She’s a geologist at Central Washington University in Ellensburg.

Colliding plates can crush against each other. Abutting edges rise as mountains. Volcanoes can form when one plate slides beneath another. Upwelling also can create volcanoes. Plates sometimes slide past each other at places known as faults. Usually these motions happen slowly. But large movements can trigger earthquakes. And, of course, volcanoes and earthquakes can cause massive destruction.

The more scientists learn about plate tectonics, the better they can understand these phenomena. If scientists could warn people when these events were coming, they also might help limit damage.

Plate Boundaries

Tectonic Plates

Active volcanoes, plate tectonics and the "Ring of Fire"

The global distribution of earthquake in the period from 1900 to 2014 and global plate boundaries

Images of tectonic plates

Conclusion

Tectonic plates are large pieces of the Earth's lithosphere (crust and upper mantle) that move relative to each other. The lithosphere is broken into seven major plates and many smaller plates. The major plates are:

Tectonic plates move over a layer of hot, molten rock called the asthenosphere. The asthenosphere is more fluid than the lithosphere, and it allows the tectonic plates to slide over it.

Tectonic plates move in different directions and at different speeds. The fastest-moving plate is the Pacific Plate, which moves at a rate of about 10 centimeters (4 inches) per year. The slowest-moving plate is the Eurasian Plate, which moves at a rate of about 3 centimeters (1 inch) per year.

The movement of tectonic plates is responsible for many of the Earth's geological features, such as mountains, volcanoes, and earthquakes. When two tectonic plates collide, one plate may be forced under the other in a process called subduction. This can create mountains and volcanoes. When two tectonic plates slide past each other, it can create earthquakes.

The Impact of Tectonic Plates on Life

Tectonic plates have a major impact on life on Earth. The movement of tectonic plates creates mountains, which provide habitats for a variety of plants and animals. The movement of tectonic plates also creates volcanoes, which release nutrients into the soil that help to support plant growth.

Tectonic plates can also have a negative impact on life on Earth. Earthquakes and volcanoes can cause widespread damage and loss of life. However, the benefits of tectonic plates outweigh the risks. Tectonic plates are essential for the creation and maintenance of the Earth's diverse ecosystems.

How the Tectonic Plates Move

Arthur Holmes suggested that this thermal convection was like a conveyor belt and that the upwelling pressure could break apart a continent and then force the broken continent in opposite directions carried by the convection currents. This idea received very little attention at the time. Not until the 1960's did Holmes' idea receive any attention.

Greater understanding of the ocean floor and the discoveries of features like mid-oceanic ridges, geomagnetic anomalies parallel to the mid-oceanic ridges, and the association of island arcs and oceanic trenches occurring together and near the continental margins, suggested convection might indeed be at work.

These discoveries and more led Harry Hess (1962) and R.Deitz (1961) to publish similar hypotheses based on mantle convection currents, now known as "sea floor spreading". This idea was basically the same as that proposed by Holmes over 30 years earlier, but now there was much more evidence to further develop and support the idea.

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