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Earth Science 2 > structural geology (week 2) > Flashcards

structural geology (week 2) Flashcards

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1
Q

what is deformation

A
  • causes rocks to change shape, size, location or orientation
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2
Q

what analysis can be performed on deformed rocks

A
  • descriptive
  • kinematic, where changes in position or shape of the rock
  • dynamic, where forces/stress acting on rock *rheology
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3
Q

how are things kinematically analysed

A
  • motion of objects
  • interpret deformational movements
  • translation, distortion, rotation, dilation and dilation
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4
Q

what is stress

A
  • is the force applied to a given area and is defined per unit area
  • stress= force/area
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5
Q

what is differential stress

A
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6
Q

what is stress ellipsoid

A
  • maximum extension occurs when stress=3
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7
Q

what is strain ellipsoid

A
  • when maximum compression occurs towards stress=1
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8
Q

what are the two types of strain and how is it formed

A
  • product of stress
  • brittle- cracking/fracturing
    -ductile- bending and flowing
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9
Q

co axial vs non co axial

A

-CO AXIAL
-horizontal stretching/ shortening

NON CO AXIAL
- shear strain

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10
Q

is a pure shear co axial or non-coaxial

A

co-axial

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11
Q

is a simple shear co axial or non-coaxial

A
  • non co axial
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12
Q

under what conditions does brittle and ductile deformation occur

A

low temperature= brittle
high temperature= ductile

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13
Q

deformation style is dependant of rheology, what factors come into play

A
  • temperature
  • minerology
  • grain size
  • rock fabric
  • fluids
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14
Q

how can strength be quantified in rocks

A
  • a compression rig can be used to yield the strength of rocks and soils
  • 3 principal axis of strength
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15
Q

how can the failure envelope be calculated

A
  • based on representative rig compression results
  • ## represents the force needed to cause a specific material to fail (fracture)
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16
Q

a very important example of modelled stress in rocks

A
  • the shakespeare cliff
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17
Q

what is a fault

A

-ma structural break in a rock across which there is notable dispacement

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18
Q

what is a joint

A
  • fractures which have no notable displacement
    important in engineering geology
19
Q

two examples of faults

A
  • highland boundary fault
  • moine thrust
20
Q

fault rock to describe the moine thrust

A

mylonites

21
Q

what are the 3 main types of fault movements

A
  • dip slip
  • oblique- slip fault
  • strike- slip
22
Q

what are the types of dip slip faults

A
  • normal fault
  • reverse fault
23
Q

what is a normal fault

A
  • hanging wall block moves down relative to the footwall
  • extension of the earths crust thins the crust
24
Q

what are reverse dip-slip and thrust faults

A
  • hanging wall block moves up relative to the footwall
  • results in compression of the earths crust= thickens the crust
  • ## reverse faults are steeper than thrust faults
25
Q

how do faults work as mineralisation zones

A
  • precipitation of ore minerals can occur within the fault and surrounding fractures
26
Q

how do faults operate as conduits

A
  • formation of hydrothermal ore deposits on the seafloor from fluid transport along faults
27
Q

what are horst and graben structures

A
  • normal fault bounded valleys= grabens
    -normal fault bounded ridges=horsts

for example, the basin and range province, in western USA

28
Q

how are mountain belts formed

A
  • compression- thrust faults- mountain belts
29
Q

what is the process in which mountain belts build

A

orogenesis

30
Q

how do sinistral strike slip faults

A
  • sinistral - (left lateral) strata on the opposite side of the fault plane is displaced on the left
  • dextral- (right lateral) - strata on the opposite side of the fault plane is displaced to the right
31
Q

how do faults operate as conduits

A

provide natural resources as hydrothermal ore deposits on the seafloor due to fluid transport along faults

32
Q

how do ores operate as mineralisation zones

A
  • precipitation of ore minerals can occur within the fault and the surrounding fractures
33
Q

what deposit provides gold to the scotgold resource Limited

A

cononish

34
Q

what is strike

A
  • orientation of a horizontal line on a planar structure
35
Q

what is dip

A

-angle of inclination on a planar structure

36
Q

what is dip direction

A
  • the compass direction in which the planar structure is dipping
37
Q

how do folds form

A
  • caused by compression stress parallel to the bedding planes in a rock body
  • ductile deformation process-very slow process (avg= 100,000 years to several mill)
38
Q

ANATOMY OF A FOLD

A
  • hinge- zone of max curvature
  • hinge line- line of maximum curvature
39
Q

what can be used to quantify tightness

A
  • interlimb angle
  • shows how much distrotion a rock has experienced
40
Q

what is the axial trace

A
  • where the axial plane intersects the earths surface
41
Q

whats an antiform

A
  • fold closes upwards (angry)
42
Q

whats a synform

A
  • fold closes downwards (smiley!)
43
Q

old rocks in the fold core

A

synformal anticline

44
Q

young rocks in the core of the fold

A

antiformal syncline

Earth Science 2 (10 decks)

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