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  • This is planet Earth. The surface of Earth may look like its all in one piece but it's

  • not. It's actually made up of several pieces called plates. Let me explain.Okay so if you

  • cut the Earth in half this is what it would look like. The Earth is made up of four main

  • layers like a big round cake. The inner layer is called the inner core which is a hard ball

  • of hot metals. Around the inner core there's the outer core which is made up of very hot

  • liquid metals. Then there's the mantle which is made up of really hot melted rock, called

  • magma. Sometimes, magma will come to the surface as lava in volcanoes. The fourth layer is

  • called the crust. Like the crust of a piece of toast, the crust of the Earth is the hardest

  • and outermost layer of the Earth. We live on the crust. The crust is not a perfect ball.

  • It is broken up into many pieces called plates. These plates fit together like puzzle pieces

  • around the Earth. Now if you look at the map you can see where the plate boundaries are.

  • These plates are called Tectonic Plates and these Tectonic Plates can move. This is the

  • world today and this is what Scientists think the world looked like 300 million years ago.

  • This land mass is called Pangea. Over time the plates moved slowly apart. They moved

  • at about the speed that your fingernails grow so it took a very long time for them to get

  • to their present positions. Remember the Mantle from earlier? Well, the mantle is the layer

  • of Earth right below the Crust and it is made of hot melted rock. This melted rock moves

  • around the mantle and since it's right below the crust; when the mantle moves, the Tectonic

  • Plates of the crust moves as well. The plates move in three ways. They converge, that means

  • come together. When this happens one plate subducts, or goes under, another plate and

  • it melts back into the mantle. This happens very slowly, again about as slow as your fingernails

  • grow. And it happens mostly in oceans so you don't have to worry about any land being subducted

  • any time soon. When two continental or land plates collide they form mountains. This is

  • how the Himalayan Mountain Range was formed in India. The tallest mountain in the world

  • formed when two plates crashed together and crumpled up. Sorta like how a car crumples

  • when it hits something big. The second way that plates interact is it divergent boundaries.

  • This is where plates diverge, or move apart. And this is also how oceans form. As Pangea

  • began to break up and the Americas began to move farther away from Africa the Atlantic

  • Ocean formed in between the continents as the plates diverged. In the middle of the

  • Atlantic Ocean you can see the Mid-Atlantic Ridge. This is where the North American and

  • Eurasian Plates meet and this is where they are being moved apart. Here, new ocean crust

  • id formed which pushes the Americas and Europe about one inch farther apart every year. The

  • third way that plates can interact is at Transform faults. A transform boundary is when two plates

  • are not moving together, converging, and they're not moving apart, diverging. Instead these

  • plates simply slide next to each other. This is happening in California right now along

  • the San Andreas Fault line. This is why there are so many earthquakes in California. When

  • the two plates rub together, they shake the ground and make earthquakes. Okay, so let's

  • review. The Earth is made up of layers and the top layer is called the crust. The crust

  • is broken down into Tectonic Plates which very slowly move around the Earth because

  • of movement in the mantle, which is the hot layer of melted rock under the crust. The

  • plates move together at convergent boundaries, they move apart at divergent boundaries and

  • they slide past each other at transform boundaries. The movement of the plates is extremely slow

  • and there is very little change every year. But over millions and billions of years, you

  • can see big changes in the way the Earth looks. We know all of this because of great scientists

  • who dedicated their lives to researching and trying to learn more about this great planet

  • we call home.

This is planet Earth. The surface of Earth may look like its all in one piece but it's

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B2 中高級 美國腔

板塊構造學。為學生分解 (Plate Tectonics: Broken Down For Students)

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    Amy.Lin 發佈於 2021 年 01 月 14 日
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