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Introduction to plate tectonics

Earth's lithosphere is broken up into tectonic plates, which move slowly over time. A plate boundary is where two tectonic plates meet. There are three types of plate boundaries: convergent, divergent, and transform. Created by Khan Academy.

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  • blobby green style avatar for user nmelo574
    why is there so many layers on earth seface
    (7 votes)
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    • blobby blue style avatar for user SuperSwetter
      I'm pretty sure when the solar system was formed from particles, Earth was mixed with these particles with many layers. The different materials were different layers on Earth's surface. More dense elements went in the core and the less dense elements went above on the crust. I hope I answered this correctly. Good question!
      (6 votes)
  • blobby green style avatar for user mmfinley2
    What would happen if the plates stop moving
    (5 votes)
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  • blobby green style avatar for user LucaS
    Why are we alive
    (3 votes)
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  • starky ultimate style avatar for user ✐®oman
    If the continents kept moving, could they eventually collide? Or would it be more likely for them to just continue breaking apart?
    (2 votes)
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    • duskpin ultimate style avatar for user Mark
      The Indian subcontinent is currently colliding with the Eurasian plate. East Africa is currently rifting and will eventually become two separate land masses.

      As long as plate tectonics remains active then continents will collide and continents will rift. It's happened many times in the past, it's happening now, and will happen many times in the future. It's what the planet does.
      (5 votes)
  • piceratops seed style avatar for user John Mendoza
    How many exact layer are there on earth
    (2 votes)
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    • female robot amelia style avatar for user Johanna
      Your answer depends on how you're defining "layers". MyName? identified the three layers of the Earth as defined by what they're made of (their chemical composition). If you're talking about the mechanical layers of the Earth (which are defined by how they behave, like whether they're solid or liquid and how rigid they are), The five mechanical layers are the:

      -Lithosphere: This is the rigid, solid outer layer. It's made out of the crust and the top part of the mantle and contains the tectonic plates.

      -Asthenosphere: This is the less rigid part of the mantle right under the lithosphere. The tectonic plates drift on currents in the asthenosphere.

      -Mesosphere: This is the stiffer part of the mantle under the asthenosphere.

      -Outer core: This is made of iron and nickel in a liquid state. Currents in the outer core generate the Earth's magnetic field!

      -Inner core: This is also made of iron and nickel, but it's solid.

      So, depending on what kind of layers you mean, there are either 3 or 5 main ones. There are also different layers of rocks in the crust, mostly corresponding to rocks of different ages.
      (5 votes)
  • blobby green style avatar for user vvin8354
    I wonder what the Eath will look like in a million years,like will some of the contents move togher and make a super content?
    (3 votes)
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  • starky seed style avatar for user Khloe Van Ommen
    are these answers made by robots
    (3 votes)
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  • starky seed style avatar for user Llorry
    They say that the continent was all connected years ago and broke apart. That means it's gonna keep dividing in the future.
    (3 votes)
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  • aqualine ultimate style avatar for user SBEAST
    ⠀⠀⠀⠉⠛⠛⠿⠿⠶⠶⠶⠶⠶⠿⠿⠿⠟⠛⠛⠋⠉⠀⠀⠀⠀⠀⠉⠉⠛⠛⠻⠿⠿⠿⠶⠶⠶⠶⠶⠾⠿⠛⠛⠋⠁please upvote
    (3 votes)
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  • primosaur seed style avatar for user cody.livermore
    Why are supercontinents, like Pangaea, considered part of a cycle? Which part of the cycle is the Earth experiencing right now?
    (2 votes)
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Video transcript

- [Narrator] What if I told you that the earth below you is moving? You'd probably say, "Of course it's moving. We're standing on a planet that's spinning on its axis while revolving around the Sun at about 107,000 kilometers per hour. And on top of that, our whole solar system is circling the center of the Milky Way galaxy." But there's another kind of movement that happens slowly in the rock beneath your feet. Earth's lithosphere, which is made up of the crust and the upper part of the mantle, is broken up into pieces called tectonic plates. These plates move around on top of the asthenosphere, which is the section of the mantle just below the lithosphere. Don't bother racing a tectonic plate, because your victory would be guaranteed. Tectonic plates typically only move a few centimeters in a year, which is about as fast as your fingernails grow. However, after millions of years, those distances add up. This means that the Earth hasn't always looked the way it does now. Scientists believe that the continents were once all connected in one big supercontinent called Pangea. Just imagine if the continents were still connected today. You could drive from Africa to Antarctica or even take a train from South America to Europe. Over 200 million years, Pangea broke apart, and the pieces drifted into the continents we know today. So if the plates move so slowly, how do we know that they move at all? Scientists have documented evidence from various features on Earth that support the theory of plate tectonics. If you cut out the continents on a map, you could see that they almost fit together like a jigsaw puzzle. For example, the east coast of South America looks like it could fit into the west coast of Africa. Matching or complementary coastlines is one piece of evidence that continents were once in different locations. Another piece of evidence is that scientists have found fossils from the same species on different continents. There's no way those land organisms could've traveled across the ocean. This suggests that the animals lived when the continents were connected. And the plates are still moving, slowly but surely, to this day. But they aren't all moving in the same direction. A plate can collide with one plate, move away from a different plate, and slide past another. We categorize the ways plates interact at their edges as having convergent, divergent, or transform boundaries. Con is a Latin prefix meaning together, so convergent plate boundaries are places where two plates come together. Let's take a look at an example of a convergent boundary where the Indian tectonic plate collides with the Eurasian plate. The crust of the plate becomes compressed, and the Indian tectonic plate gradually moves under the Eurasian plate. However, the lower density of the crust keeps the Indian plate from sinking back into the asthenosphere all the way. This lifts up the Eurasian plate and creates the Himalayan mountains. These mountains are some of the highest in the world, and they include Mount Everest, which is the tallest mountain above sea level. And the two plates are still colliding. This causes the Himalayas to grow by more than one centimeter each year. Another kind of plate movement is called a divergent boundary. The di in divergent comes from a Latin prefix meaning apart, so divergent boundaries happen where two tectonic plates move apart. Divergent boundaries can create different kinds of land forms, like rift valleys and mid-ocean ridges. The third kind of plate boundary is called a transform boundary or transform fault, and it happens when two plates slide past each other. Okay, maybe slide isn't the best word for it, because the plates don't move in one continuous motion. You can imagine when two incredibly large, bulky, rocky things move past each other, there's a lot of friction. Pressure builds up between the plates, and once it gets to be too much, the plates slip and release the pressure. This motion causes earthquakes. And you might be wondering, what causes plates to move? Well, scientists are always learning about the Earth, since the Earth is so complex. Although Earth's internal heat may play a small role, more evidence shows that gravity is key. Tectonic plates are solid, and they're denser and cooler than the asthenosphere. Because the asthenosphere is also pretty solid, the plates rest on top of it. However, the asthenosphere is so hot that it can behave a bit like clay. This means that at convergent boundaries, the edges of the plates can sink into the asthenosphere, a process that is driven by gravity. So even though you'd win in a race against a tectonic plate, the plate will still keep on moving millions of years after you've declared yourself to be the winner.