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Geology > Test 2 (Lectures 4-8) Pt. 3 > Flashcards

Test 2 (Lectures 4-8) Pt. 3 Flashcards

(68 cards)

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1
Q

What are metamorphic rocks?

A

Pre-existing rocks that have undergone solid-state changes

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1
Q

What does the word “meta” stand for?

A

Change

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2
Q

What does the word “morphe” stand for?

A

Form

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3
Q

The preexisting rocks that are altered during metamorphism are called

A

Protoliths

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4
Q

Metamorphism can alter to what type of protoliths?

A
  • Igneous
  • Sedimentary
  • Metamorphic
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5
Q

Protoliths undergo changes in what?

A
  • Texture
  • Mineralogy
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6
Q

Why do protoliths undergo these changes?

A

They can happen due to:
- temperature
- pressure
- tectonic stress
- the amount of reactive water

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7
Q

What are some metamorphic processes?

A
  • Recrystallization
  • Neocrystallization
  • Pressure solution
  • Plastic Deformation
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8
Q

What is recrystallization?

A

When minerals change shape and size through dissolution and growth of crystals. Ex - limestone to marble

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9
Q

What is neocrystallization?

A

Formation of new metamorphic minerals from old (those from protoliths)

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10
Q

What is pressure solution?

A

When mineral grains partially dissolve where their surfaces press together

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11
Q

What is plastic deformation?

A

When mineral grains soften and deform when rock is squeezed or sheared at elevated temperature and pressure

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12
Q

What are the two different kinds of differential stress?

A
  • Normal
  • Shear
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13
Q

Why does differential stress occur?

A

It’s a result of tectonic forces

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14
Q

Mountain building creates a horizontal compression ___; rifting creates a horizontal extension _____

A

Push; pull

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15
Q

How does normal stress work?

A

Operates perpendicular to a surface

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16
Q

What is compression?

A

Push-together normal stress

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17
Q

What is tension?

A

Pull-apart normal stress

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18
Q

How does shear stress work?

A

It acts as a parallel to the surface

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19
Q

How does differential stress occur?

A

It causes inadequate mineral shapes to align in preferred orientations

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20
Q

Why does foliation develop?

A

The rocks have been subjected to differential stress

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21
Q

What is foliation?

A

A planar fabric that cuts through the rock

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22
Q

What are some foliated metamorphic rocks?

A
  • Phyllite
  • Schist
  • Metaconglomerate
  • Gneiss
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23
Q

What are some non-foliated metamorphic rocks?

A
  • Quartzite
  • Marble
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24
What are the different types of metamorphism?
- Thermal - Burial - Dynamic - Regional - Hydrothermal - Subduction - Shock
25
What is contact (or thermal) metamorphism?
Metamorphism that is due to heat from a body of magma invading host rock
26
Dynamic metamorphism involves
A breakage of rock by shearing within a fault zone
27
When does dynamothermal tend to occur?
It occurs during the development of mountain belts. This process is also called regional metamorphism.
28
What does directed compression do?
Smashes pre-existing rocks and buries them deeply where they get heated by geothermal gradient and plutonic intrusions
29
What is hydrothermal metamorphism?
When hot, chemically, aggressive water chemically alters basalt
30
What is subduction metamorphism?
When trenches and accretionary prisms have a low geothermal gradient
31
What are shields?
Large regions of ancient high-grade metamorphic rocks are exposed in continental interiors
32
Mountains occur in elongate curvilinear ____ or ____
Belts; orogens
33
Mountain building is a process called
Orogenesis
34
Mountains reflect the geologic processes of
- Uplift - Deformation - Metamorphism
35
Mountain building involves many geological processes such as
- Deformation - Jointing - Faulting - Forming
36
What does deformation do?
It changes the character of rocks
37
Where does brittle deformation mainly occur?
It occurs in the shallower crust
38
What are the two major deformation styles?
Brittle and ductile
39
What is strain?
The change in shape caused by deformation or by a leading force (stress)
40
Stress
Force applied across a unit area
41
What are the different types of stress?
- Compression - Tension - Shear - Pressure
42
What is compression?
When an object is squeezed
43
What is tension?
When the ends of an object are pulled apart
44
What is shear?
When surface slide past each other
45
What is pressure?
When an object feels the same pressure from all sides
46
The geometry of planar surfaces during rock formation is described using
Strike and slip
47
Dip is always ___ to strike
perpendicular
48
What are joints?
Planar rock features without any offset to develop from tensile stress in brittle rock
49
Fractures filled with minerals are called
Veins
50
What are faults?
Planar fractures that show offset
51
The amount of offset is called?
Displacement
52
What are some fault motions?
- Dip-slip faults - Strike-slip faults - Oblique slip faults
53
In a normal fault, the hanging wall moves..
Down
54
In a reverse fault, the hanging wall moves...
Up
55
In a thrust fault the hanging wall is..
A reverse fault with a 30-degree dip
56
Strike-slip faults have fault motion ____ to the strike of the fault
Parallel
57
Slickensides and linear grooves are
Slip lineations
58
Fault scarps are visible when
Faults intersect the surface
59
What is a hinge?
A line along which curvature is greatest
60
What are limbs?
Less curved "sides" of a fold
61
What does the axial plane do?
Connect hinges of successive layers
62
What is an anticline?
A fold that looks like an arch
63
What is a syncline?
A fold that opens outward like a through
64
What is a dome?
A fold with the appearance of an overturned bowl
65
What is a basin?
A fold shaped like an upright bowl
66
Where are the youngest rocks found in a basin?
They're found in the basin
67
Where are the youngest rocks found in a dome?
They're found in the sides or the corners

Geology (19 decks)

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