Geology Final Exam Flashcards
(125 cards)
1
Q
A rock whose original minerology and/or texture has changed due to pressure and temperature WITHOUT melting
A
metamorphic rocks
2
Q
protolith of blue schist
A
basalt
3
Q
protolith of garnet-staurolite schist
A
shale
4
Q
increase in temperature with increasing depth
A
geothermal gradient
5
Q
average geothermal gradient
A
30C/km
6
Q
minerals are stable over restricted conditions of T (and P)
A
geothermometry
7
Q
pressure gradient
A
0.3-0.4 kbars/km
8
Q
pressure in all directions (analogous pressure under water)
A
confining pressure
9
Q
force exerted in a specific direction .causes folding, deformation, and minerals to align.
A
directed pressure
10
Q
minerals are stable over restricted conditions of P (and T)
A
geobarometry
11
Q
fluids can add or remove chemical components resulting in changes in the bulk composition
A
mesosomatism
12
Q
protolith for gneiss
A
granite
13
Q
protolith of marble
A
limestone
14
Q
set of flat or wavy parallel planes produced by deformation
A
foliation
15
Q
Foliated rocks are classified by
A
- crystal size
- nature of foliation
- segregation of minerals into light and dark bands
- metamorphic grade
16
Q
order of increasing grade in metamorphic rocks (increasing metamorphic grade)
A
slate, phyllite, schist, gneiss, migmatite
17
Q
heat from igneous rock intrusions metamorphoses surrounding rock (small scale)
A
contact metamorphism
18
Q
heat and pressure are imposed over large areas of the crust (large scale).i.e. mountain belts. result from changes in P and T. rocks are deformed (folded and faulted). Formed from collision of tectonic plates.
A
regional metamorphism
19
Q
metasomatism of the oceanic crust by hydrothermal circulation
A
hydrothermal (seafloor) metamorphism
20
Q
meteorite impact
A
shock metamorphism
21
Q
groupings of rocks of different mineral composition based on temperature and pressure. Minerals in a rock are clues to the history (P and T) of the rock.
A
metamorphic facies
22
Q
the set of all P-T conditions experienced by a rock during its metamorphic history
A
Pressure-Temperature Path
23
Q
increasing pressure and temperature
A
prograde
24
Q
decreasing pressure and temperature
A
retrograde
25
pulls rocks apart,(stretching) at divergent boundaries.
rift valleys.
tensional forces
26
pushed rocks together (squeezing and shortening), at convergent boundaries.
mountain belts.
compressional forces
27
pushes either side of a formation in opposite directions, at transform boundaries.
i.e. san andreas fault
shearing forces
28
compressive features
folding, reverse/thrust faulting
29
tensional features
stretching, thinning, and normal faulting
30
shearing features
shearing, strike-slip faulting
31
minor internal strain, catastrophic break
brittle
32
smooth, continuous plastic deformation
ductile
33
folding, stretching, thinning, shearing
ductile
34
reverse, normal, strike-slip faulting
brittle
35
low confining P
low T
high strain rate
low water content
brittle
36
high confining P
high T
low strain rate
high water content
ductile
37
where do brittle deformations occur?
shallow crust
38
where do ductile deformations occur?
deep crust
39
the direction of the intersection of a rock layer with a horizontal surface
strike
40
angle at which the bed inclines from the horizontal (down and to the right of strike)
dip
41
fracture with no offset
joint
42
fracture with offset
fault
43
the wall that is below feet
footwall
44
FUN (Footwall Up Normal)
drops younger rocks down against older rocks (footwall older than hanging wall). divergent boundaries. found in rift zones.
normal faulting
45
FDR (Footwall Down Reverse)
puts older rocks on top of younger rocks (footwall younger than hanging wall). convergent boundaries.
reverse faulting
46
repeated sequences of large lateral displacement
thrust faulting
47
side to side movement, can still have footwalls or hanging walls
strike-slip faulting
48
a convex-upward fold whose core contains the older rocks (mountain shaped)
anticline
49
a concave-upward fold whose core contains the younger rocks (valley shaped)
syncline
50
an imaginary surface that divides a fold as symmetrically as possible
axial plane
51
the line made by the length-wise intersection of the axial plane with the beds
fold axis
52
fold with a non-horizontal fold axis
plunging fold
53
limbs dipping symmetrically away form axial planes
symmetrical folds
54
one limb that dips more steeply than the other
asymmetrical folds
55
limbs that dip in the same direction. one or both limbs are tilted beyond vertical.
overturned folds
56
a broad circular anticlinal structure, with the beds dipping radially away from a central point
dome
57
a broad circular synclinal structure, with the beds dipping radially toward a central point
basin
58
the occurrence of one event in relation to another
relative dating
59
the number of years that have passed from the event until now
absolute dating
60
newer ones were formed on top of older ones
principle of superposition
61
sediments are deposited in nearly horizontal beds
principle of original horizontality
62
geologic features that cut across rock must be younger than the rock they cut through
principle of cross-cutting relationships
63
objects enclosed in rock must be older than the time of rock formation
principle of inclusions
64
layers are continuous until encountering an obstruction
principle of lateral continuity
65
layers of sedimentary rocks contain fossils in a definite sequence
principle of faunal sequence
66
surface between two layers that was not deposited in an unbroken sequence; record of missing time
unconformity
67
younger sediments rest upon the eroded surface of tilted or folded older rocks
angular unconformity
68
an unconformity between beds that are parallel
disconformity
69
an unconformity between stratified rocks above and unstratified igneous or metamorphic rocks below
nonconformity
70
same # protons, different # neutrons
isotope
71
undergo spontaneous decay to form atoms of another element (parent isotope)
radioactive isotopes
72
undergo spontaneous decay to form atoms of another element (daughter isotope)
radiogenic isotopes
73
How to date igneous rocks?
age of crystallization
74
How to date metamorphic rocks?
yes; new mineral grows with only parent atoms or heating releases the daughter and resets the clock.
no; heating is not sufficient to reset clock.
age of metamorphism (not age of original rock)
75
How to date sedimentary rocks?
Date igneous intrusions in sedimentary rocks.
Date volcanic ash layers.
Use fossils.
76
Age of the earth is known from
meteorites and moon
77
low density silicate materials (O, Si, Al, K)
crust
78
40 km thick
density: 2.8 g/cm^3
continental crust
79
7 km thick
3.0 g/cm^3
oceanic crust
80
less dense continental crust floats higher on denser mantle than oceanic crust
isostatic balance
81
most of the planet. high density silicate materials (O, Si, Mg, Fe, Ca, Fe).
density of 3.4 g/cm^3.
SOLID, GREEN, ULTRAMAFIC
mantle
82
upper 100 km layer that is strong and rigid
upper mantle
83
lower 100 km is weak and deformable, ductile
lower mantle
84
mostly Fe, but also Ni, S, O.
LIQUID because of temperature.
density of 11 g/cm^3
outer core
85
mostly Fe, but also Ni.
SOLID because of temperature.
density of 13 g/cm^3
inner core
86
crust and upper mantle (100 km).
relatively cold, strong, rigid
lithosphere
87
weaker part of the upper mantle, hot, weak, ductile
asthenosphere
88
basalt is extruded at MORs. basalt records the magnetic field at the time of cooling. crust moves away from the ridges and becomes older.youngest near ridges and oldest near continent.
sea floor magnetic anomalies
89
occur at zones of upwelling mantle. produces new oceanic crust. basaltic volcanism. small, shallow, earthquakes. normal faults, high heat flow. (mid ocean ridges)
divergent boundaries
90
explosive andesitic volcanism. intrusion of granite at depth. large earthquakes, shallow to deep. metamorphism, folds, thrust faults. (subduction zones)
convergent boundaries
91
no igneous activity. no metamorphism. large, shallow earthquakes. strike-slip faults.
transform boundaries
92
attraction of oppositely charged ions, intermediate strength (halite)
ionic bonding
93
electron sharing, very strong (diamond)
covalent bonding
94
weak electrical bonding, intermolecular bonding (water)
van der waals bonding
95
naturally occurring, crystalline substance, inorganic, specific chemical composition
minerals
96
how to id rocks
mineralogy, texture
97
form when magma erupts at the surface, rapidly cooling to fine ash or lava and developing tiny crystals. fine-grained rocks.
extrusive igneous rocks
98
crystallize when molten rock intrudes into un-melted rock masses in earth's crust. coarse-grained rocks
intrusive igneous rocks
99
low silica content, darker
mafic
100
high silica content, lighter
felsic
101
result from explosive volcanic ejection
pyroclastic material
102
lithified volcanic ash
tuff
103
rock with two stages of cooling; slow cooling and fast cooling
porphyr
104
how do rocks melt
decompression, and addition of water
105
what most likely causes melting at divergent boundaries
decompression
106
what most likely causes melting at convergent boundaries
addition of water, increase in temperature
107
melts are always more than their parent
felsic
108
causes wide range of composition of igneous rocks
partial melting, fractional crystallization, magma mixing, assimilation
109
mafic minerals crystallize at higher temperatures than felsic minerals. mafic minerals crystallize first from cooling magmas. high temperatures = faster crystallization
bowen's reaction series
110
provide a record of history
sedimentary rocks
111
process by which rocks are broken down. physical and chemical.
weathering
112
process by which rocks are moved after breaking down
erosion
113
physically transported rock fragments produced fro
114
physically transported rock fragments produced from weathering of preexisting rocks (sandstone/shale)
clastic sediments
115
direct, chemical deposition typically in marine settings (limestone, evaporite)
chemical and biochemical sediments
116
selection of clasts according to particle size
sort
117
more mafic rocks tend to weather
faster
118
gravitation balance that determines elevation
isostasy
119
elevation is function of
thickness and density
120
pressure at the base of various parts of the curst is equal. to have the same pressure underneath and different densities, the thickness differs.
principle of isostasy
121
magma transferred to continents at subduction zones (increase continent size)
magmatic addition
122
buoyant fragments of crust attached to continents due to plate motions (increase continent size)
continental accretion
123
mountain building process of folding, faulting, magmatism, and metamorphism
orogeny
124
vertical motions of largely flat lying rocks without faulting or significant folding
erogeny
125
general up or down warping of the crust with no faulting or folding.
epeirogeny
