Theory of Plate Tectonics

• Theory that pieces of lithosphere move around on top of the asthenosphere

Plate Boundaries

• The edges of different pieces of The lithosphere meet at lines called plate boundaries

Plate Boundaries

Plate Videos

So the plates move.Now What?

•As the plates move, they produce changes in Earth’s surface, including volcanoes, earthquakes, mountain ranges, and deep-ocean trenches.

3 Types of Plate Boundaries

Divergent

Convergent

Transform

Divergent

Transform

3 Types of Boundaries

Divergent boundary= two plates move apart

• Magma rises and creates new crust or seafloor

Causes: mid-ocean ridges, rift valleys, new crust , volcanoes

Divergent Boundaries

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Diverging Africa

Diverging Iceland

3 Types of Boundaries

• Convergent= when two tectonic plates push into one another.

Convergent Boundaries

• Continental vs. Continental

• Continental vs. Oceanic

• Oceanic vs. Oceanic

Continental vs. Continental•When two continental crustal plates collide, the continents buckle upward and form mountains.

Himalayas- Asia

Himalayas- Asia

Oceanic vs. Continental

•The oceanic plate slides under the continental plate.

•The continental crust crumbles and forms new mountains.

Oceanic vs. Continental

• Ex: Andes mtn in S.

America

Cascade Mtns. in N. America- Mt. St. Helens

Oceanic vs. Oceanic

•Two oceanic plates collide, one of the oceanic plates slides under the other.•also called a subduction zone

Hawaiian Islands

Oceanic vs. Oceanic

Transform boundary

• When two tectonic plates slide past each other horizontally

Produces?

Earthquakes

San Andreas Fault

New Madrid Fault

How do the plates move?

• CONVECTION CURRENTS• Hot material rises while

cooler material near the

surface sinks

• Convection example

How do the plates move?

• CONVECTION CURRENTS• Hot material from deep within the Earth

rises while cooler material near the surface sinks

Convection currents

How do we know?

• Sea-floor spreading

=new ocean floor is

created as two

lithospheric plates

pull away from

one another.

Seafloor spreading

The Plates Move…So what now?

Which way?

• 50 million years