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