Mastery Check #5 - Plate Tectonics
The Earth's crust is broken up into plates, which are constantly moving around. If you look at the maps below, you should be able to see a pattern between Earthquakes, volcanoes, trenches, mid-ocean ridges, and plate boundaries. Earthquakes and volcanoes don't happen randomly around the world. They are concentrated along the edges of plates. Many things happen at plate boundaries but we will focus on two things.
What is happening at Trenches?
Trenches are places where two plates come together. One plate will sink below another plate and, when it gets deep enough and hot it enough, it will melt. This causes magma to rise up and from volcanoes. Also, as the plate push against each other, they build up pressure and energy. When the pressure is great enough, the plates shift and releases all that stored up energy. This is what causes earthquakes. Plates coming together is what causes the most powerful earthquakes and the most explosive volcanoes.
What is happening at Mid-ocean ridges?
Mid-ocean ridges are places where two plates are moving away from each other. As they spread apart, magma from deep in the Earth comes to the surface and creates new ocean crust. The tension between the spreading plates, builds up pressure that is released in Earthquakes. Plates spreading apart creates volcanoes and earthquakes that are not very powerful or explosive.
What evidence is there that Pangaea existed?
Pangea is a supercontinent that existed on Earth about 250 million years ago. There were no people around at that time to tell us about Pangea so how do we know that it existed? There are three main evidences we will focus on:
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