What Causes Earthquakes?

The San Andreas Fault is in the news as it is said to be “locked and loaded” and ready to generate an earthquake. This video from National Geographic shows that most of the volume of the Earth is located in its hot, molten core, which is in constant motion as the inner molten rock rises close to the crust and its tectonic plates, then cools and falls back to the core, where the cycle begins again. Where two tectonic plates meet, such as at the San Andreas Fault, the edges of the plates are under tremendous pressure to slide against one another, and scientists now predict an earthquake could happen any time.