lecture 3.2 - Deformational structures (brittle + faults)

Question 1

define undeformed rocks

Answer 1

lateral continuity layers (beds)

Question 2

describe the principle of superposition

Answer 2

the layer underneath the superior layer = oldest layer

oldest layer = 1 in ascending older

Question 3

define stress

Answer 3

application of forces to a rock layer

Question 4

define strain

Answer 4

deformation of a rock layer due to stress

Question 5

What are the 3 types of stress? Define them

Answer 5

compression - opposing forces directed towards each other (–> . <–)

Tension - opposing forces directed against each other (<– . –>)

Shear - forces sliding past each other (–>
<–)

Question 6

what are the 3 types of strain? Define them

Answer 6

Elastic - rock deforms when stress is present, but returns to OG shape after stress is gone

Plastic - rock deforms while stress is present and stays deform after stress is gone

Brittle - Rock “fractures” and breaks into pieces to relieve stress

Question 7

What strain deformation are seen in faults

Answer 7

brittle deformation

Question 8

convergent margin is what stress

Answer 8

compression

Question 9

divergent margin is what stress

Answer 9

tension

Question 10

transform fault is what stress

Answer 10

shear

Question 11

relationship between stress vs. strain

Answer 11

stress –> strain

Question 12

Head block vs. Foot block

Answer 12

Head = area above fault
Foot = area below fault

Question 13

Name both types of faults and compare them.

Answer 13

Normal fault = Hanging (head) block falls down relative to Foot block

Reverse fault = Hanging (head) block moves up relative to Foot block

Question 14

How do we know which block is moving?

Answer 14

we don’t. Assume head block moves and foot block stays stationary

Question 15

How to identify normal fault vs. reverse fault?

Answer 15

Normal fault = tension = gap in bed (region extended)

Reverse fault = compression = overlap in bed (region shortened)