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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
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
