Aim: How do the plates of the Earth move?

Do Now:

Using the worksheet, “Plate Movement: In out and Sideways”, answer the following questions below.

- What forms at a spreading zone?- What forms at a fracture zone?- What three features form at a

convergence zone?

I. Causes of Plate Motion

Convection currents within the mantle push and pull the plates (ESRT p.10)

•Convection occurs when warm material rises and cool material sinks (DENSITY!)

II. Types of Plate Boundaries

1. Divergent boundaries form where two plates move apart (spreading).

• Rift valleys are found at the boundaries the divergent plates.

• Oceanic ridges are found on either side of the rift valley.

• Seafloor spreading produces new oceanic crust at divergent plate boundaries

2. Convergent boundaries form where two plates come together.

Which type of crust sinks under

the other and why?

• Oceanic crust sinks since it is more dense.

• Subduction zones are where one plate is forced down into the mantle beneath a second plate.

• trenches mark the subduction zones on the surface.

Subduction zone

A. Oceanic Crust vs. Continental Crust

• Continental Volcanoes form from the rising magma. (example: Andes Mountains)

• Oceanic crust sinks beneath the continental.

B. Oceanic Crust – Oceanic Crust

• Volcanic Islands grow out of the ocean (example: Aleutian Islands)

• One of the two plates sinks under the other.

• The two plates collide and the continents being carried are forced upward.

C. Continental Crust – Continental Crust

• Mountain ranges form from the uplift of these continents (example: Himalayan Mountains)

3. Transform fault boundaries formwhere two plates grind/slide pasteach other.

• They move parallel

• Faults and fractures

• Shallow earthquakes occur

- cuts and cracks.

San Andreas fault in California is an example of a transform boundary

Boundary Type Movement Features

Convergent

Divergent

Transform

ESRT PAGE 5