Everyone you've ever met is from Earth. Unless you have something interesting to tell us. Earth is the
prototype for terrestrial planets. It rotates fairly quickly. It consists of a mixture of rock and iron. Its interior is
divided into layers, that is, differentiated. Like most terrestrial planets, Earth has a relatively thin atmosphere.
Earth is also special in so many ways. It is the only place in the universe where we know life to exist. We have liquid water
in our oceans and free oxygen in our atmosphere, which was not at breathable levels until just a few hundred million years
ago. Earth also has plate tectonics, which which just might be essential to life. This animation shows how the crust of Earth
has floated around over the last 750 million years.
However, plate tectonics can have its downside as well. Sometimes the plates of Earth’s crust move quickly and violently.
We call these events earthquakes. How common are earthquakes on Earth? Watch this animation. Or this one. And what is
happening right now?
