STAAR Review: Plate Tectonics

Earth's crust is broken into 2 plates

Continental crust

Oceanic crust

Convergent

Divergent

Transform

When the crust (plates) shift or slide past one another, it isn't a smooth movement

Earthquakes are felt when these plates move

The crack in the crust is called a plate boundary or fault line

The San Andreas fault in California is an example

Plates divide or separate

This is called seafloor spreading

Magma comes up and cools into rock to create new ocean crust

A mid ocean ridge is formed (volcanic mountains)

Younger rock is near the ridge and they get older as you move away

When 2 continental plates collide they fold up and make a mountain

When one continental and one oceanic plate collide, the heavier oceanic plate sinks

This sinking process is called subduction

The continental crust pushes up into a mountain

The old subducting curst melts into magma forcing it to go up into the mountain making it a volcanic mountain

A deep ocean trench is also formed when the oceanic plate sinks

When one oceanic plate collides with another oceanic plate, the older heavier oceanic plate will sink, or subduct

A deep ocean trench is formed

The older crust will melt into magma and form volcanic islands