- from Earthquakes
Earth has had earthquakes for all of its 4.6 billion years.
These days, scientists know a lot about them. But it’s still not easy to tell when or where one will hit. Also, there’s no way to control a quake. Most scientists say earthquakes are caused by the rocky plates that cover the Earth. Quakes happen when the plates press really hard against each other and the rock breaks. The plates move all the time, but usually the rock bends very slowly. Then the rock can’t bend any more. It breaks and snaps back to its original shape, like a rubber band. That’s what causes an earthquake. This idea is called the elastic rebound theory.
A lot of energy is released when the rock breaks. It makes different types of waves, known as seismic waves. They pass through and around the Earth. The place where the energy is released is the center, or focus, of the earthquake. The waves flow away from the center like water waves.