A fault line is a place where two Teutonic plates meet. One of the largest in the world is the San Andrea's Fault Line. The Teutonic plates start to move and that's what causes the earthquake. When 2 or more plates meet and scratch. There are a ton of fault lines all over the world. The plates are the outer layer of the earth called the lithosphere. There are seven major Teutonic plates. Where the ocean plate meets with the continental plate the ocean plate slides below the continental plate. That makes an ocean trench. Below are some of the major plates.