Structural Geology

Question 1

Structural Geology

Answer 1

Study of how rocks deform in response to stresses in the Earth

Question 2

Types of Earth Stressors?

Answer 2

1.) Compression : contraction/shortening of rock or fossil (pushed together); common at convergent boundaries
2.)Normal Stresses: Act at right angles to a surface (Common at all 3 tectonic settings)
-small area=high stress
-large area= low stress
3.) Tension: elongation/stretching (pulled apart); common at divergent boundaries
4.) Shear

Question 3

Tectonic Setting of Compression

Answer 3

Convergent Boundary

Question 4

Tectonic Setting of Tension

Answer 4

Divergent Boundary

Question 5

Tectonic Setting of Shear Stress

Answer 5

Transform, Divergent, Convergent

Question 6

Brittle Deformation

Answer 6

Fracture of rock due to stress

Question 7

Ductile Deformation

Answer 7

Bend and Flow of rock due to stress (w/out brittle fracture)
*Pliable not Brittle

Question 8

Brittle-Ductile Transition
-> depth of deformation?
->Factors that determine how a rock Deforms?

Answer 8

-Rocks deform ductiley ~300-400 °C
-10-15km depth (ie; pressure)
-ductile-brittle transition is dependent on rock type
*Below brittle-ductile transition ; faults = shear zones due to no fracture in the rock
Factors:
1.)Temp/Pressure
2.) Deformation Rate:
-slow deformation=ductile
-fast deformation=brittle
3.) Rock Type

Question 9

Brittle Faults Settings

Answer 9

1.) Normal
2.) Reverse
3.) Strike-Slip

Question 10

Normal Faults

Answer 10

Hanging wall is down relative to footwall
occur @ Divergent Boundaries:
-continental expansion settings (ex: Nevada Basin and Range)
-Mid-Ocean Ridges

Question 11

Reverse Faults

Answer 11

Hanging wall up, footwall down
@Convergent Boundaries
-subduction plate=footwall
-overriding plate=hanging wall
Low angle reverse faults=thrust faults

Question 12

Strike-Slip

Answer 12

Vertical fault, lateral displacement
ex; San Andreas, Alpine Fault

Question 13

Restraining Bend

Answer 13

Bend within strike-slip fault which causes compression across the straining bend
ex: Santa barbs and Mt. Denali

Question 14

Ductile Fault Settings

Answer 14

Shear zones

Question 15

Faulting

Answer 15

slip between two rocks along brittle fracture

Question 16

Tilting

Answer 16

Rotations of rock layers due to stress

Question 17

Folding

Answer 17

Bending of rock layers due to stress

Question 18

Joint Formation

Answer 18

Brittle fractures with no displacement (naturally formed cracks in rock)

Question 19

Types of Folding (2)

Answer 19

1.) Anticline
2.) Syncline

Question 20

Anticline

Answer 20

Concave down

Type of folding

Question 21

Syncline

Answer 21

Concave up

Question 22

Deformation in Santa Barbara

Answer 22

Resistant band along the San Andreas Fault causes compression and uplifting wave-cut terraces and the Santa Ynez Mts.
-Folding under Santa Barbs