Download Plate Tectonics

Plate Tectonics
3 Movements at plate boundaries
Divergent boundaries
• Plates are moving apart
• As plates move apart, new crust forms Cause of
movement is convection cells in mantle
• Mid ocean ridges are divergent boundaries where
seafloor spreading occurs – an example is the
Mid-Atlantic Ridge.
• Rift valleys are divergent boundaries on land –
The Great Rift Valley in east Africa is an example
of a continent breaking apart. The Red Sea is a
part of the rift.
Convergent plate boundaries
• Two plates are colliding or moving together
• Old crust is being deformed or destroyed(melted)
due to collision
• At convergent zone one of two things can happen
– Oceanic plate crust can be forced down underneath
less dense continental or oceanic crust, forming a
deep ocean trench at the subduction zone. Ex:
Aleutian trench south of Alaska
– Continental plates colliding cause rocks to fold and
break, creating mountain ranges Ex: Himalaya
mountains where India collides with Asia
Transform Boundary
• Two plates sliding past each other.
• Crust is neither created nor destroyed (side
swipe)
• Example: San Andreas fault in S. Calif
between the N. American and Pacific plates