Earthquakes are nothing new to this planet. They’ve been shaking the Earth for all of its 4.6 billion years.
Though today’s scientists know a lot about them, earthquakes are still hard to predict and impossible to control. Today, most scientists think earthquakes are caused by the rocky plates covering the Earth. Quakes happen when the plates press so hard against each other that the rock breaks. The plates move all the time, but usually the rock bends very slowly and there’s no sudden, violent movement. Finally, the rock can’t bend any more. It breaks and snaps back to its original shape, like a rubber band. Then an earthquake happens. This explanation is known as the elastic rebound theory.
When the rock breaks, a huge amount of energy is released. That causes waves, known as seismic waves, to travel through the Earth and over its surface. The place where the energy is released is the center, or focus, of the quake. The waves ripple away from the focus like water waves.
