4.16.12

Article Review due Friday

Homework: Pg 468 #1-14

Objectives

Explain the process of convection.

Summarize how convection in the mantle is related to the movement of tectonic plates.

Compare and contrast the process of ridge push and slab pull

Question

What makes the plates move?

Mantle Convection

Does anyone remember the layers of the Earth?

What about their properties

Earth Layers

Mantle Convection

remind me how a convection current works

A substance warms and becomes less dense

It rises

As it cools it becomes more dense

It sinks

Mantle Convection

Look at a diagram of the Earth again

What role do you think that convection plays in moving Earth’s plates?

Earth Layers

Mantle Convection

As magma rises at a ridge it forces the plates apart

Magma that cools at the ridge forms new ocean floor

The sideways movement of the magma pulls the plate

Cooling, sinking magma pulls plates into the subduction zone

Mantle Convection

Convection currents alone aren’t enough to push the plates

When magma rises the ridge is lifted up

Gravity causes the ridge to push the plate towards the subduction zone

Called Ridge Push

Mantle Convection

The edge of the plate sinking into the trench pulls on the rest of the plate

Called Slab Pull