Further information: Plate tectonics

Three types of plate boundary.

Plate boundaries refers particularly to places where continental plates touch or have touched in the past.

The major types of plate boundaries are:

1. Spreading boundaries. Mid-Atlantic Ridge and Africa's Great Rift Valley are examples. Rift valleys, mountains (orogeny), volcanoes.
2. Collision boundaries. These collide, forming a subduction zone (West coast of the Americas) or a continental collision (India with Asia). Mountains (orogeny), valleys, volcanoes.
3. Transform or fault boundaries. Here plates grind past each other along transform faults. Earthquakes and volcanoes often occur along the fault.
4. Conservative boundaries: little or no relative motion.

All boundaries except the conservative ones are sites of major geological activity. view more...