EAS 210 > CHPTR 9 Deformation > Flashcards

CHPTR 9 Deformation Flashcards

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1
Q

deformation

A

changes in the shape, volume, position or orientation of rock layers

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2
Q

folds

A

wavy deformation - anticline

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3
Q

fault

A

straight deformation

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4
Q

primary structures

A

occur when rock formed

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5
Q

primary structures example

A

strata
cross-bedding
ripple marks
mud-cracks
graded belts

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6
Q

secondary structures

A

occurs after rock forms

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7
Q

secondary structure examples

A

folds
faults

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8
Q

stress

A

force per unit area :)

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9
Q

differential stress

A

the force is not being applied evenly - the element will be deformed

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10
Q

strain

A

change in shape of a rock when stress is applied

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11
Q

elastic limit for rocks

A

0.001

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12
Q

plastic behaviour + example

A

material behaves as a very viscous liquid - does not return to original shape when stress is removed

ex. glacial ice

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13
Q

fracture

A

breaks, with formation of cracks

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14
Q

area under the curve of a stress-strain graph

A

toughness (absorbed energy before fracture)

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15
Q

where does compressional stress occur and what does it cause

A

convergent plate boundaries - faulting and folding

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16
Q

where does tensional stress occur and what does it cause

A

divergent plate boundaries - faults

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17
Q

where does shear stress occur

A

transform plate boundaries

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18
Q

what encourages brittle deformation

A
  • low temp./pressures (near surface)
  • crystalline igneous rocks
  • fast deformation
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19
Q

what does brittle deformation form

A

joints and faults

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20
Q

what encourages ductile deformation

A
  • high temp.//pressures (deep/close to magma body)
  • sedimentary + metamorphic rocks
  • slow deformation
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21
Q

what does ductile deformation form

A

folds

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22
Q

strike direction

A

intersection of a horizontal plane with an inclined plane (compass direction)

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23
Q

dip angle

A

max angle of inclined plane

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24
Q

anticline

A

concave down (Arch)

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25
syncline
concave up (like a sink)
26
axial plane
axis of symmetry with limb on each side
27
axis
intersection of axial plane and a particular rock layer
28
plunge
difference in angle between horizontal and axis. (if you go along the axial plane, does the ground change elevation)
29
upright fold
- symmetric - axial plane vertical - limbs dip at same angle in opposite directions
30
inclined fold
- asymmetric - axis plane not vertical - limbs dip at different angles (from horizontal)
31
overturned fold
- asymmetric - axis plane not vertical - different angles in same direction (from horizontal)
32
ways to see folds
outcrops, geophysics
33
outcrops
visible exposure of underground rocks - dig it up - beach cliffs
34
geophysics (seismic reflection)
map rock layers with reflected sound waves
35
when doing seismis reflection, which rock type has worse quality lines
igneous
36
monocline
single change in direction: - fault moves - as sedimentary rocks settle on top, they drape over the fault, creating a gradual incline
37
dome
concave down warping of crustal rocks - anticline in all directions
38
basin
down-warping of crustal rocks - syncline in all directions
39
dome ages of layers
centre strata is oldest outer strata is youngest (highest is oldest)
40
basin ages of layers
centre strata is youngest outre strata is oldest (highest is oldest)
41
joint
fractures with no appreciable displacement has occurred (cracks in rocks but no movement like a fault would have)
42
what kind of rocks can have joints
igneous and sedimentary
43
fault
fractures along which appreciable displacement has occurred
44
fault trace
the fault line
45
fault scarp
cliff or steep incline along the faultline
46
hanging wall
the side of the fault that you could hang off of
47
foot wall
the side of the fault that you could stand on
48
dip slip faults + types
the slip is parallel to the dip reverse normal thrust
49
normal fault
hanging wall moves down relative to footwall
50
reverse fault
hanging wall moves up compared to footwall
51
thrust fault
reverse fault with a dip less than 45 degrees
52
megathrust fault
occurs in subduction zones responsible for the largest earthquakes
53
klippe
remnant portion of a nappe after erosion has removed connecting portions
54
nappe
sheetlike body of rock that has been moved above a thrust fault
55
strike slip fault
strike and slip are parallel
56
right lateral fault
when looking at the fault, the other side appears to have moved right
57
left lateral fault
when looking at the fault, the other side appears to have moved left
58
true or false: faults can have a mix of dip-slip and strike slip motion
True
59
strike slip faults result in:
1. sag ponds 2. offset drainage 3. linear valley
60
sag ponds
body of water collected in a depression formed by strike slip movement it is disconnected from any source of water
61
offset drainage
one side of a river is moved; the path of the flow of water changes
62
linear valley
along the fault line creates a linear valley
63
blind thrust fault
fault does not rupture to the surface - no scarp but there is deformation
64
Economic importance of faults
1. water flows through faults 2. reliable source of oil and gas resources
65
Economic importance of faults - water flows through faults
heavy and valuable minerals are deposited in faults - particularly at the intersections of major faults
66
Economic importance of faults - source of oil and gas
- organic materials experience high temp and pressure when buried - oil and gas form and move upwards - impermeable layer overlies a porous layer and resevoirs form
67
Structural traps by faults/folds; list types
1. antiklinale trap 2. fault trap 3. salt trap
68
stratigraphic trap by deposition explain
formed by the sequence of deposition - places an impermeable cap rock above a porous reservoir layer
69
antiklinale trap
anticline structure creates an oil/gas reservoir
70
fault trap
a fault structure creates an oil/gas reservoir
71
salt trap
the oil/gas reservoir is trapped between the salt dome and an impermeable cap rock
EAS 210
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