Crustal Deformation

Question 1

Mountains manifest through three geologic processes

Answer 1

• Uplift
• Deformation
• Metamorphism

Question 2

What is orogenesis

Answer 2

Building of mountains

Question 3

The three results from deformation

Answer 3

-Displacement (change in location)
-Rotation (change in orientation)
-Distortion (change in shape)

Question 4

What is strain

Answer 4

Change in shape caused by deformation

Question 5

What are the three types of strain

Answer 5

-Stretching (pulling apart)
- Shear (sliding past)
-Shortening (squeezing together)

Question 6

Two major types of deformation

Answer 6

• Brittle
• Ductile

Question 7

Factors that affect the type of deformation that occurs

Answer 7

-Temperature
-Pressure
-Deformation rate
-Composition

Question 8

What is brittle deformation

Answer 8

Rock breaks through fracturing and occurs in the shallow crust

Question 9

What is ductile deformation

Answer 9

Rocks deform by flowing and folding, and occurs at higher T and P deeper in the crust

Question 10

How deep into the earth’s crust do rocks transition from deforming brittlely to deforming like a ductile

Answer 10

~10-15 km

Question 11

What is stress

Answer 11

A strain that is caused by force acting on a rock

Question 12

What is the relationship between stress applied and the amount of deformation

Answer 12

Large force per area stress results in large amounts of deformation

Question 13

What are the types of stress and how do they affect the thickness of the crust (3)

Answer 13

• Compression, causes thickening of the crust
• Tension, causes thinning of the crust
• Shear, doesn’t cause thickening or thinning

Question 14

Explain what dip and strike are in terms of mapping geologic features

Answer 14

Strike: Horiztonal intersection with a tilted surface
Dip: The angle of the surface down from the horizontal line

Question 15

What is a joint and how does it develop

Answer 15

Planar rock fractures without any offset, and develop from tensile stress in brittle rock

Question 16

How do veins develop from joints

Answer 16

Joints often have cracks that allow groundwater to flow through and when minerals precipitate out its creates veins

Question 17

What is a fault

Answer 17

A planar fracture showing displacement

Question 18

Identify the difference between hanging-wall and footwall

Answer 18

Hanging wall is above the fault and footwall is below

Question 19

What are the three classifications of faults

Answer 19

-Dip slip: Blocks move parallel to the dip of the fault
-Strick slip: Blocks move parallel to the fault strike plane
- Oblique slip: Components of both dip slip and strike slip

Question 20

What are the three types of dip-slip faults

Answer 20

-Reverse fault where the hanging moves up at a steep angle
-Thrust fault where the hanging wall moves up at a gentle slope
-Normal fault where the hanging wall moves down fault slope

Question 21

What is the amount of offset in a fault called

Answer 21

Displacement

Question 22

What is an anticline

Answer 22

Is a fold that looks like an arch

Question 23

What is a syncline

Answer 23

Is a fold that opens upward like a trough

Question 24

What is a monocline

Answer 24

Is a fold-like carpet draped over a stair step

Question 25

What are a dome and basin

Answer 25

Dome: Fold that looks like an overturned bowl
Basin: Fold that looks like an upright bowl

Question 26

What are the two ways that fold develops

Answer 26

Flexural slip and passive flow

Question 27

What flexural slip

Answer 27

Is when the layers slide past one another, like bending a deck of cards

Question 28

What is passive slip

Answer 28

Form in hot, soft, ductile rock at high T

Question 29

Look at slides 37-47 to see all examples of different folds

Answer 29

.

Question 30

Mountain uplift is driven by: (3)

Answer 30

• Convergent boundaries
• Continental collision
• Rifting