1. Tectonic Plate Boundaries and Their Effects
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2. Divergent Boundaries: Examples are East African Rift and Mid-Atlantic Ridge

3. Divergent Boundaries Due to convection cells in Mantle.
Two plates move away from each other.
Results in volcanoes, rift valleys, mid-ocean ridges.
Youngest rock at spreading ridge.
Normally Basalt is erupted to make new oceanic crust.
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4. Convergent Boundaries: Example: Japan

5. Oceanic-Continental Convergent
More dense oceanic crust SUBDUCTS under less dense continental crust.
Called Subduction Zones.
Forms volcanoes and mountains from melting of overlying continental crust. Also earthquakes.
Examples: Cascade Mountains in Washington and Andes Mountains in South America.

6. Oceanic-Oceanic Convergent
When older, more dense oceanic crust subducts under younger oceanic crust.
Results in deep trenches (Marianas Trench) and Island Arcs of Volcanoes (Ex. Japan). Also earthquakes.

7. Continent-Continent Convergence
When two continents collide.
Forms mountains and deforms crust (folding and faulting).
Metamorphism also a result
Example: Himalayas and ancient Appalachians.
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8. Transform Boundaries

9. Transform Boundaries Plates slide past each other.
Results in shear, bending, breaking, and earthquakes.
Offset: How much a plate has moved over time.
Example: San Andreas Fault in Calfornia.
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10. Causes of Plate Movement
Convection Cells
Ridge Push
Slab Pull
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11. Convection Cells
Hot magma rises in the mantle, heated by earth’s core.
The magma cools at it moves toward the the crust and sinks.
Opposing convection cells create friction on the lithosphere that breaks it apart.

12. Ridge Push
As the newer, warmer rock cools and becomes denser, it begins to slide down the slope between the lithosphere and the asthenosphere.