Earth's surface - or lithosphere - is made of 8 major tectonic plates and several more minor ones.
These continental and oceanic plates, which average about 50 miles in thickness, are constantly in motion,
sliding and slipping several inches a year.

Where these massive areas of Earth's crust meet - at plate boundaries or fault zones - plates can pull apart, collide or slide across each other. When these movements happen, earthquakes are sure to follow. And depending on the type of plate boundary, temblors can be minor in intensity or can trigger severe earthquakes that cause rock and mudslides, topple buildings and rip apart the ground.

Earth's surface is scarred by tens of thousands of miles of these fault zones, mostly along continental shorelines and at the bottom the oceans. This map shows the major plates and their boundaries.

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