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toc =Earth's Crust in Motion=

Vocabulary

 * earthquake**- the movement deep underground that occurs when stress releases
 * stress**- the energy released during an earthquake
 * shearing**- the stress force that makes two rocks go in different directions
 * tension**- the stress force that stretches rock until it breaks or changes
 * compression**- the stress force that squeezes rock
 * deformation**- the changes caused by the forces of stress
 * fault**- a crack in the earth's crust that forms after an earthquake
 * strike-slip** **faults**- caused by shearing, rocks move past each other but with barely any up-and-down movement
 * normal** **faults**- caused by tension, creates a slanted fault leaving one rock above the other
 * hanging wall**- the hanging wall lies below the footwall in a normal fault but is the opposite in a reverse fault
 * footwall**- the footwall is above the hanging wal in a normal fault, but is the opposite in a reverse fault
 * reverse** **faults**- caused by compression, also creates a slanted fault leaving the previous rock below the other rock
 * fault-block-mountain**- a mountain formed by two faults that carry a rock mass
 * folds**- when compression occurs and either rock doesn't give in, the rock folds
 * anticline**- caused by folding, uplifts rock creating a hump
 * syncline**- also caused by folding, the space between the hump (anticline)
 * plateau**- caused by compression, a large mass of rock above the sea

Stress in the crust

 * Earthquake
 * caused by stress
 * three types of stress tension, compression, shearing
 * all these forces cause deformation
 * mountains, faults, footwalls, hanging walls

Types of Stress

 * Tension
 * stretches rock to become thinner in the middle or until it breaks
 * causes normal fault
 * Shearing
 * causes rocks to break and slip past each other
 * causes strike-slip fault
 * Compression
 * pushes rock together
 * can make rock break or fold
 * can make a reverse fault

Kinds of Faults

 * Strike-Slip Faults
 * two rocks slip past each other from shearing
 * not much up or down movement
 * if between plates, fault called transform boundary
 * Normal Faults
 * Tension creates fault at an angle
 * one rock lies bellow the other
 * in __normal faults only__, a footwall is the rock that is above the hanging wall
 * When tension occurs, hanging wall goes downward
 * Reverse Faults
 * opposite of normal fault, but caused by compression
 * foot wall is __below__ hanging wall in a reverse fault

Friction Along Faults

 * Friction is the force that opposes the motion of one surface as it moves across another surface.
 * lower the friction, the less rock sticks, higher the friction is, the more rocks lock
 * friction high in some places, when stress releases them in those places, an earthquake is created
 * like the San Andreas fault

Mountain Building
Anticlines and Syniclines
 * rocks can use forces of stress to change earths surface.
 * Mountains Formed by Faulting
 * when normal faults uplift a block of rock, a fault block mountain forms
 * two normal faults [[image:A_Fault_Block_Mountain.jpg caption="When the middle block slips down a valley formes like the Sierra Nevada, Great Basin, and Mojave desert"]]
 * when two hanging walls slip down, middle block goes up
 * Mountains formed by folds
 * sometimes crust folds when pushed together by other crust by compression
 * Himalayas and the Alps were caused by folding
 * Some folding collisions form earth quakes because folding rocks can fracture and produce faults \


 * caused by folding
 * anticlines= upward bump of a fold
 * synicline= downward bump of a fold.
 * in black hills south of Dakota and Illinois Basin this occured
 * Plateaus
 * plateaus are large areas where FLAT land above sea are
 * different flat layers, some are wider than it is tall like the Colorado Plateau.

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