Geology- rock structures
Terms
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- Strike
-
-perpendicular to the direction of the dip
-direction of line of intersection - Dip
-
-angle at which a rock layer or fault is inclined from the horizontal
-at a right angle to the strike - tension
- -pulls a rock body apart
- Compression
- -pushes a rock body inwards
- Shear
- -when two adjacent parts of a rock body slide agaisnt each other
- Brittle Deformaton
- fractures (faults)
- Ductile Deformation
- does not fracture (folds)
- Anticline
- -formed by upfolding or arching of rock layers
- sycline
- -formed by downfolding of rock layers
- Faults
- -fractures in the crust upon which displacement has taken place
- Normal Faults
-
- steep dips of about 60%
-flatten out with depth
-ex:dip slip fault
-hanging wall moves down relative to foot wall - Reverse Faults
-
-dips greater than 45%
-horizontal shortening of the crust
-hanging wall moves up relative to foot wall - Thrust Faults
-
-dips less than 45%
-horizontal shortening of the crust - Plunging anticline or syncline
- - when the axis of the fold penetrates into the ground
- Domes
- - a circular or elongated sturcutre caused by upwarping
- Basins
- -similar to a dome, but caused by downwarping
- Dip Slip Faults vs. Strike Slip Faults
-
dip slip-vertical
strike slip- lateral or horizontal - Black Hills, South Dakota
- Structural Basin
- San Andreas Fault
- long, linear valleys
- Grabens
- flat, sediment filled valleys
- Horsts
- abruptly rising bedrock ranges