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Plate Boundaries, Faults, and Stress
Unit 2 Lesson 2
Lithosphere -
Asthenosphere -
rigid, brittle crust and uppermost part of mantle
Oceanic crust – thin, dense, basalt
Continental crust – thick, low density, granite
partially molten part of upper mantle, able to flow
Plate Boundaries
TransformConvergent Divergent
plates move toward each other and collide; crust is destroyed & one plate is pushed below the other
plates slide horizontally past each other; crust is neither produced or destroyed
plates move away from each other; new crust is generated between the separating plates
Convergent Plate Boundary
Continent to Continent
Subduction
Form mountain belts
Oceanic crust dives beloweither oceanic or continentalcrust
Form deep-sea trench
Ocean-continent – volcanic mountains along edge
Ocean-ocean – volcanic island arc
Convergent Plate Boundary
Subduction Zones
Faults Fractures (breaks) in the earth occur when a
force is applied to the underlying rock, which movement occurs.
Stress is the force per unit area acting upon a material.
There are 3 types of stress that acts upon the Earth’s rocks: Compression: decreases material volume
(shorten) Tension: pulls the material apart (lengthen) Shear: Causes the material to slip or twist
(distortion)
Types of Faults Slip Faults
Horizontal tension Sideways movement
Normal Fault Tension (Apart)
Down on advancing block
Thrust/Reverse Fault Compression
Uplift of advancing block
Examples of Faults Reverse Fault
Note the compression Note the uplift
San Andreas Fault Pulled apart Sideways movement
Fault Summary… http://youtu.be/lyfND_lugSo