Ch 8

Geology 100 with Hooyer at University of Wisconsin - Milwaukee

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By: Abigail Zielke
Created: 2010-04-07
Size: 41 flashcards
Views: 3

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Force

a push or pull that causes or tends to cause change in the motion of a body

Stress

the amount of force divided by the area where the force is applied

How do rocks respond to force and stress

If stress is small rock may reamain unchanged, if stress is greater rock may be displaced , rotated, have its shaped modified , or strained , or all four

Displacement

in response to stress a rock may be moved from one place to another, rock may stay same shape or change as it moves

Rotation

rock may be rotated in response to stress

Strain

a rock may respond to stress by deforming internally; change size or shape without layers breaking or rotating

brittle behavior

at shallow levels of crust

ductile (flowing) behavior

at deeper levels where temperature and pressure are higher

Strain: a rock may respond to stress by deforming internally; change size or shape without layers breaking or rotating

Rock Behavior
brittle behavior: at shallow levels of crust
ductile (flowing) behavior: at deeper levels...
Mineral Response
Stable: at shallow level with low pressure...
Recrystalization: at deep levels of crust w/...
Effect of Fulids
At low temperatures fluids have little effect...
Veins: may occur at low levels of crust where...
At deep levels hot water and other fluids...

Stable

at shallow level with low pressure and temperature minerals remain stable

Recrystalization

at deep levels of crust w/ high temperatures and pressure minerals recrystallize into smaller crystals and new minerals may grow

-Veins

may occur at low levels of crust where water fills fractures with minerals

Stress field

the entire array of stresses applied on a point or volume of rock

syncline

a fold, generally concave and upward, with the youngest rocks in the center

confining pressure

when the force imposed on the rock is the same amount from all directions

fluid pressure

pushes outward in all directions (water in pores push outward)

differential stress

what deforms rocks

-comprension

when a stress pushes in on rock

-Tension

when stress is directed outward, pulling the rock

-Shear

stresses on the edge of the block were applied in opposite directions

-tension @ shallow

can form from fractures that help the rock stretch as it is pulled apart

-shear @ shallow

usually forms a fault

fault

a fracture along which two rock masses have slipped past one another

-compression @ deep

can squeez the rocks and form tightly squashed folds and new metamorphic structures

-tension @ deep

difficult to maintain deep in crust; high confining pressure pushes inward and generally is greater than any forces pulling rock apart; can fracture the rock and form veins

-shear @ deep

commonly is distributed across a wide zone; rocks deform and flow as weak solids

joints

fracture that form as simple cracks representing places where the rock has pulled apart by a small amount

joints form

perpendicular to the direction of least stress

vertical joints

when the stress field allows the rock to be pulled apart in a horizontal direction; can form in compass direction, depending on the orientation of the stresses

horizontal joints

form if a rock is pulled apart in a vertical direction; can occur when tectonic stresses push on the sides of the rock, which causes the vertical stress to be the smallest stress

horizontal joints: form if a rock is pulled apart in a vertical direction; can occur when tectonic stresses push on the sides of the rock, which causes the vertical stress to be the smallest stress

ways to describe faults
dip: a fault surface that is inclined in one direction; described in terms of...
strike: when water floods area of fault it will intersect or strike along a...
dip-slip faults: slip along a fault can be parallel to the dip - one block...
strike-slip fault:can occur in a horizontal direction, parallel to the strike.
oblique-slip fault: slip along a fault can also occur in a direction that is...

dip

a fault surface that is inclined in one direction; described in terms of degrees from horizontal or use of terms such as steep, moderate, and gentle

strike

when water floods area of fault it will intersect or strike along a horizontal line; orientation of a surface's strike relative to true norht

dip-slip faults

slip along a fault can be parallel to the dip - one block moves up or down relative to the other block

oblique-slip fault

slip along a fault can also occur in a direction that is oblique - neither parallel to the dip nor the strike

hanging wall

the block above the fault

footwall

the block below the fault

normal fault

if the hanging wall moves down relative to the footwall; forms when the rock units are pulled apart and lengthenen

reverse fault

if the hanging wall moves up relative to the footwall; forms as a result of horizontal compression and shortens the rock units in a horizontal direction

thrust fault

a reverse fault that has a gentle dip

strike-slip fault

when rocks along a fault move with a side-to-side motion, parallel to the strike of the fault surface

About this deck

By: Abigail Zielke
Created: 2010-04-07
Size: 41 flashcards
Views: 3

About StudyBlue

“I have been getting MUCH better grades on all my tests for school. Flash cards, notes, and quizzes are great on here. Thanks!”
Kathy