Test 2 Material Flashcards
1
Q
Metamorphic Rocks
A
formed by increases in pressure, or pressure from igneous, sedimentary, or other metamorphic rocks
2
Q
How to create Metamorphic Rocks
A
Heat, Pressure, Fluids, and Parent Rock
3
Q
Heat in Metamorphic rock formation
A
from nearby magma or geothermal gradient, causes minerals to change and recrystallize
4
Q
Pressure in Metamorphic rock formation
A
two types: confining and differential
5
Q
Confining Pressure
A
weight of overlaying rocks increases with depth, applied equally in all directions, become smaller and denser material
6
Q
Differential pressure
A
pressure that is not equal on all sides, rock is distorted and minerals line up, occurs during deformation which happens during mountain building
7
Q
Fluids in Metamorphic rock formations
A
water and other volatiles, enhances migration of ions and promotes recrystallization of existing minerals
The water comes from pore spaces of sedimentary, fractures in igneous rocks, and hydrous minerals
8
Q
Parent rock in metamorphic formation
A
mineral composition determines the degree to which a rock will change.
9
Q
How is Metamorphic rock classified
A
size, shape, arrangement of mineral grains
10
Q
Foliation
A
planar arrangement of mineral grains, compositional banding, formed by rotation and recrystallization of elongated minerals
11
Q
Non-Foliated
A
no elongated minerals to align, equidimensional (round-ish) crystals
12
Q
Slate
A
fine grained (parent material: shale), slaty cleavage
13
Q
Types of Foliated Rocks
A
Slate, Phyllite, Schist, Gneiss
14
Q
Phyllite
A
minerals not large enough to visibly identify, glossy appearance
15
Q
Schist
A
medium to coarse grained, schistosity texture
16
Q
Gneiss
A
medium to coarse grained, banded appearance, formed under very high temperature and pressur
17
Q
Metamorphic grade
A
describes the pressure and temperature of which a rock was subjected to, leads to different metamorphic minerals and different foliation textures.
18
Q
Low grade metamorphic to high grade metamorphic
A
Slate, Phyllite, Schist, Gneiss
19
Q
Non-Foliated Rocks
A
Marble and Quartzite
20
Q
Marble
A
coarse, crystalline, parent rock is limestone
21
Q
Quartzite
A
interlocking quartz grains, parent rock is sandstone
22
Q
Metamorphic Environments
A
contact metamorphism, and regional metamorphism
23
Q
contact metamorphism
A
increase temperature from nearby magma, low grade metamorphism
24
Q
Regional metamorphism
A
associated with mountain building
25
Metamorphic Zone
the texture of a metamorphic rock depends on the pressure and temperature
26
Index minerals
form under certain temperature an pressure, they can help identify the metamorphic processes that a rock was subject to
27
Metamorphic Facies
more specific temperature and pressure range, given by numbers
28
Wegner's Lines of Evidence
the continents have a jigsaw puzzle fit, evidence of past glaciations, striations, tropical and subtropical environments across N America and NW Africa, coal deposits, distribution of fossils, correlation of geologic units
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striations
scratches on rock produced by ice moving over it
30
Wegner's problems
continental rocks are weaker than oceanic rock, rotational forces of the earth are too small to move massive chunks of land
31
Military contribution to plate tectonics
during WWII the military developed sonar technology to map out the ocean floor
32
bathymetry
shape of the sea floor
33
facts about the ocean floor
there are highs and lows, variable sediment thickness on ocean floor, was not old enough to have been accumulating for all of earth's history
34
who is younger oceans or continents
oceans
35
Sea floor spreading
new ocean crust is made at mid ocean ridges and crust gets older as it moves away
36
trenches
where the sea floor is consumed
37
mid ocean ridge
where sea floor is created
38
history of magnetic reversals
preserved magnetic records are symmetric around mid ocean ridges, they can be used to identify the spreading center
39
Oldest oceanic crust
200 million years
40
oldest continental crust
4 billion years
41
crust
oceanic and continental
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mantle
below the crust, plastic consitency
43
the core
liquid outer, solid inner, both composed of iron and nickel
44
lithosphere
crust and the upper mantle, it is rigid, brittle and cold
45
Asthenosphere
rest of the mantle, plastic, flows very slowly and not molten
46
Oceanic vs Continental lithosphere
Continental - about 150 km thick and primarily made of granite
Oceanic - from 10-100km thick and primarily made of basalt and gabbro
47
Plate
piece of lithosphere
48
plate tectonic theory
pieces of lithosphere move relative to one another move over the asthenosphere
49
Identifying plate boundaries
earthquakes and volcanoes usually happen at boundaries
50
How far do plates move each year
they move between 2-7 cm, which is as fast as fingernail growth
51
Types of plate boundaries
divergent, convergent, and transform
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divergent boundary
where two plates are moving away from each other, also known as a constructive boundary, builds new crust
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rift
divergent boundary on continental crust
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ridge
divergent boundary on oceanic crust
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Convergent boundary
where two plates are colliding or running into one another, also known as destructive boundary, carries a lot of volatiles into the mantle and creates volcanoes, oceanic crust dives under continental
56
volcanic island arc
happens when two oceanic plates converge
57
mountain building event
when two continental plates converge
58
subduction zone
ocean-ocean or ocean-continent convergent boundary
59
transform boundary
where plates move past one another, side by side, also known as a conservative boundary
60
conservative
plate material is neither created or destroyed
61
destructive
plate material is destroyed
62
constructive
plate material is created
63
left vs right lateral
describes the relative motion of the plate boundary
64
hotspots (oceanic vs continental)
volcanoes in Hawaii are caused by hots spots, plate moves while the hot spot is stationary, so that is why there are multiple islands in a row, they can also come up underneath continents - yellowstone
65
Plate vs Continental boundaries
some plates follow the boundaries of continents and some do not
66
Active margin
at edges of continents where you have an active plate boundary
67
passive margin
transitional area between oceanic and continental crust, minimal tectonic activity
68
Wilson Cycle
describes how continents rift apart and then come back together again through time
69
why do plates move?
they are largely driven by convection in the mantle, where heat from the core creates convection cells in the mantle and the plates ride the convective flow like a moving sidewalk
70
how do we measure the movement of continents
it is measured in relation to hot spots, plates move, hot spots don't move
71
Importance of plate tectonics
explains earth's major surface processes, distribution of ancient organisms and minerals, geologic distribution of earthquakes, volcanoes, and mountains.
72
Why do we care about volcanoes?
they emit huge quantities of gas and debris into the atmosphere, ash produced by eruptions leads to very fertile soil, often located near coastlines where lots of people live, beautiful and interesting but also unpredictable and dangerous
73
Mount Vesuvius
Destroyed Pompeii and Herculaneum in 79AD
74
Mount Pelee
Martinique (Lesser Antilles) erupted in 1902 and killed everyone except one guy, largest number of casualties (28,000) from a volcano this century
75
Mount Galeras
Columbia, erupted in 1993, six geologists and three tourists were inside when it erupted
76
Mount Saint Helens
Washington, erupted in 1980, there were 57 casualties, and the damage cost was 2.7 billion dollers
77
General features of Volcanoes
Summit opening, vent, fumarole
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Summit Opening
produced by the collapse of the volcano following an eruption, crater, and caldera
79
crater
a summit opening less than 1km
80
caldera
a summit opening greater than 1 km
81
vent
connection between the summit opening and magma chamber
82
fumarole
emits gas and smoke
83
Controlling factors on volcano type
shape and explosivity of a volcano is controlled by viscosity
84
Viscosity
determined by composition: felsic - higher viscosity, mafic - lower viscosity
temperature
volatiles - explosivity of eruption related to how easily gasses escape
85
Mafic lavas
gases easily escape, low viscosity, mild eruptions, broad shaped volcanoes, bassalt
86
felsic lavas
gasses are trapped, high viscosity, explosive eruptions, steep-sided volcanoes, rhyolite and andesite
87
Products of eruptions
lava, pyroclastic materials, pyroclastic flow, and lahar
88
lava
magma extruded by the volcano
89
pahoehoe
ropey texture lava
90
Aa
rough blocky texture lava
91
Pyroclastic materials
debris extruded by volcano, bomb-big, lapilli-middle, and ash-small
92
Nuee Ardente (Pyroclastic Flow)
hot gasses infused with ash and debris, avalanche like and can reach speeds of 200 km/h, it is like a cloud
93
Lahar
volcanic mudflow, mixture of melted snow and volcanic debris, moves down hill
94
Types of Volcanoes
Sheild, Composite, Cinder-cone
95
Sheild Volcano
broad and slightly dome shaped, cover large areas, mild eruptions of large volumes of mafic lava, Example: Kilauea, Hawaii
96
Composite volcano
large, classic-shaped, steep sided volcano, alternating layers of lava and pyroclastic material, violent eruptions of felsic lava, Example: Mount Saint Helens, Mount Fuji
97
Cinder Cone
built from ejected pyroclastic material, steep-sloped volcano but small in size, they occur in groups
98
Volcanic Related Feautres
Caldera, Lava Domes, lava tube, columnar joints, pillow lava
99
Caldera
a steep-walled depression at summit formed by collapse
100
How calderas form
1. magma chamber fills and eruption begins
2. as eruption proceeds, the magma chamber drains and central portion of volcano collapses
3. the collapsed area becomes the caldera
101
lava domes
bulbous mass of congealed lava, associated with explosive eruptions
102
lava tubes
an insulated tube where the outside lava has cooled an solidified, but the lava inside can now flow fast (50km/h), associated with mild mafic eruptions
103
Columnar joints
lava contracts as it cools, opening joints, forms hexagonal column that cools down into the lava
104
pillow lava
lava rapidly chilled through contact with water, composes most igneous rock in the upper oceanic crust
105
Where are volcanoes found
found at ridges and rifts, subduction zones, and above hotspots
106
general volcanic lava composition based on location
oceanic setting - mafic
continental setting - intermediate or felsic
107
Ridges and Rifts (divergent boundaries)
decompression melting occurs as the plates move apart from each other, large quantities of mafic magma produced
108
Subduction Zones (convergent boundaries)
volatiles carried down with plate lead to melting and magma, tends to produce felsic magma, Example: "Ring of Fire"
109
Hotspots (volcanoes)
occur within a tectonic plate, associated with mantle plumes, magma composition depends on location, mafic - under oceanic, felsic - under continental
110
Stress
force applied to a specific area
111
strain/deformation
how rocks change shape over time, a change in volume and or shape, caused by the application of stress
112
Three types of stress
compression, tension, shear
113
compression
convergent boundaries
114
tension
divergent boundaries
115
shear
transform boundaries
116
elastic deformation
strain is proportional to stress, rock returns to its original shape once stress is removed
117
plastic deformation
a rock is permanently deformed and will not return to its original shape, two types: brittle and ductile
118
brittle deformation
where the rock snaps or breaks
119
ductile deformation
where the rock sort of flows and stretches
120
factors controlling deformation
temperature and pressure, time, rock composition/strength
121
temperature and pressure in deformation
higher temperature and pressure = ductile deformation
lower temperature and pressure = brittle deformation
122
time in deformation
stress applied slowly = ductile deformation
stress applied quickly = brittle deformation
123
geologic structures
faults, joints, folds, dome, basin
124
joints
result of brittle deformation, no movement, "natural cracks", tend to occur in groups, helps advance weathering
125
faults
result of brittle deformation, normal fault - tension, reverse fault - compression, strike slip fault - shear
126
folds
result of ductile deformation, series of wave like undulations caused by deformation and stress
127
anticline
folds pointing up like an A
128
syncline
folds point down like a smile U
129
oldest rocks location in anticline and syncline
oldest rocks are in the middle of an anticline and are on the outside of a syncline
130
Limb
"arms" of the fold
131
axial plane
imaginary plane that divides the fold in half
132
hinge line
line connecting points of maximum curvature
133
dome
upwarped rock layers
134
basin
down warped rock layers
135
strike
the compass direction of the line produced by a intersection of a rock layer with a horizontal plane, measured clockwise from north
136
what type of deformation is higher metamorphic grade
ductile - higher metamorphic grade
137
what type of plate boundary is often associated with metamorphism and ductile deformation
convergent boundaries
138
Accreted terrains
land added to a continent through convergent margins
139
orogenesis
term used to describe an episode of mountain building
140
What holds mountains up
crust underneath shortens and thickens creating a root
141
Isostasy
gravitational balance between the lithosphere and the asthenosphere. tectonic plates "float" at a height dependent on their thickness and density
142
Isostasy Equation
(D-block/D-float) = (T-root/T-block)
143
Isostatic rebound
happens to glaciers when the ice melt so the curst has to snap back in place
144
Craton
crust that has not experienced an orogeny for at least 1 billion years
145
Parts of a Craton
shield, and platform
146
shield
where Precambrian igneous and metamorphic rocks are exposed
147
platform
where Precambrian rocks covered by a thin layer of sediment
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