A meteorologist named Alfred Wegener had a theory about how the continents got where they are today. He thought that they had started as one supercontinent named Pangaea, and then drifted to their current position. His theory wasn't believed during his time because he had no way to prove it. There were some things that back his theory up like the same fossils being found on different continents with different climates and the way the edges of the continents fit together like a puzzle.
Today, we know he was correct in thinking that. The proof we have is because of the discovery of tectonic plates. They are giant plates that "carry" the continents. They move because they are on the asthenosphere, a plastic-like layer of the mantle. They move because of something called a convection current. In these currents in the asthenosphere, the cooler plastic-like mantle is denser so it goes down closer to the center of the Earth and pushes the warmer mantle up.
The pressure and temperature there are higher in the lower area, so the once cooler mantle becomes hot, and the hot mantle becomes cool. They then switch, and keep switching, and pushing the plates.
These plates are the cause of earthquakes, tsunamis, the creation of mountains, rift valleys, and volcanoes. Different things happen at different types of boundaries.
On convergent boundaries, two or more plates move towards each other and collide, causing earthquakes. This is also how tsunamis are caused. An earthquake at sea occurs, and sends a wave of water that travels at great speeds, and crashes when it gets to the shore. Also, when two plates collide, they may hit and go up and form mountains.
On a divergent boundary, two or more plates move away from each other. On these boundaries, rift...