Plate TectonicsWhat evidence do scientists have to support the fact that the Earth’s crust

is continuously moving?

Plate Tectonics

• The theory that describes how tectonic plates move and shape Earth’s surface

• Tectonic plates are huge pieces of crust that fit together at their edges to cover Earth’s surface.

About 12 plates exist on Earth

Earth’s Interior• Crust – Rigid outer shell

of Earth– Oceanic and Continental

Crust

• Mantle

– Upper mantle is partially molten

– Lower mantle is rigid (solid)

Earth’s Interior

• Core– Outer core is

molten iron, source of Earth’s magnetic field

– Inner core is solid, Iron and Nickel

Plate Boundaries

Divergent Boundary

Convergent Boundary

Transform Boundary

Divergent Boundary

• Two tectonic plates move apart from each other

• Rift valleys – long narrow depressions

• Rift valley in East Africa

Convergent Boundary

• Two tectonic plates move towards each other (come together)

• Oceanic Plates are more dense

• Continental Plates are less dense

Subduction• Process when one tectonic plate slips

beneath another plate

• Oceanic – Oceanic

– Subduction Occurs

– Deep Sea Trenches (Marianas Trench)

• Oceanic – Continental

– Subduction Occurs

– Trench and Volcanic Arch (Peru – Chile Trench)

• Continental – Continental

– Mountain Building

– Himalayas

– Aleutian Islands

Transform Boundary

• Region where two plates slide past each other

• Earthquakes occur at transform boundaries

• San Andreas Fault in San Francisco