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Plate Tectonics
Plate tectonics is the theory that Earth’s surface is divided into several rigid plates, and that geological phenomena such as earthquakes, volcanoes, and mountain formation occur as these plates move relative to one another.
These plates include the Earth’s crust and the upper mantle, and they are known to move very slowly (a few millimeters to several centimeters per year) due to convection currents in the mantle.
Plate Boundaries, Volcanic Belts, and Earthquake Zones
As plates are created and move, they may collide with one another. Various crustal changes occur along plate boundaries, resulting in faults, earthquakes, and volcanic activity.
- Plates move away from each other
- Magma rises and creates new crust
- Examples: Mid-Ocean Ridge, Iceland
- Plates collide with each other
- One plate moves beneath another (subduction), or mountain ranges are formed
- Examples: Himalayas, Japan Trench
- Plates slide past each other horizontally
- Earthquakes occur frequently
- Example: San Andreas Fault