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Geology > CH. 4 > Flashcards

CH. 4 Flashcards

1
Q

What is the bulk of Earth’s crust

A

Igneous Rocks

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2
Q

How are igneous rocks formed

A

cooling anf solidifaction of magma- minerals crystallize

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3
Q

Two different types of igneous rocks

A

extrusive and intrusive

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4
Q

Extrustive Igneous rocks

A

AKA Volcanic
Magma erupts on Earth’s surgace, melt solidifies above surface (Volcanism)
Lava flows
Pyroclastic deposits: Ash bets, tuffs, pumice/scona
cools quickly, fine-grained, not differentiate easily

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5
Q

Intrusive Igneous rocks

A

AKA Plutonic
magma solidifies below the surface
formy various igneous features- plutons
cools slowly, coarse-grained, see the difference

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6
Q

Pluton types

A

Igneous Sikes
Igneous Sills
Laccoliths
Stocks
Batholiths

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7
Q

Igneous dikes

A

Intrusion that cuts across layers (vertical)

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8
Q

Igneous Sills

A

Intrusion that runs parallel to layers (horizontal)

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9
Q

Laccoliths

A

Lens shape, causes surface doming

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10
Q

Stocks

A

<100 Km^2, irregular shaped

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11
Q

Batholiths

A

> 100 Km^2, massive
hundred of miles long
forms from multiple smaller plutons
associated with convergent plate boundary
exposed by erosion
SIena Nevada Batholith

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12
Q

Irregular plutons

A

stocks
Columnar joints
Batholiths

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13
Q

Columnar Joints

A

way it cools, cracks form, cool outward to inward

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14
Q

Crystallization from a melt

A

how igneous rocks form
mostly silicate minerals form
size of mineral relates to how fast the melt cools

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15
Q

Order of how silica mineral crystalize from melt associated with what

A

melt temp and composition

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16
Q

CHaractersitics of how to classify rock

A

Texture and composition

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17
Q

texture

A

crystal grain size and others
Cooling rate influence texture

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18
Q

Cooling rate influencing texture

A

Faster cooling- smaller crystal zide
Slower cooling- bigger crystal size
cooling instantly- no crystals- glass

Slow cooling- coarse grained (intrusive)
Fast cooling- fine grained (extrusive)

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19
Q

Various sizes of minerals classification

A

Pegmatitic
Phanerititic
medium grained
APHANITIC
glassy
Poryphitic

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20
Q

Pegmatitic

A

Huge crystals
VERY slow crystallization
greater than 71 cm

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21
Q

Phanerititic

A

Coarse grained- slow crystallization, large crystals

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22
Q

medium grained

A

still big- below ground- but not quite at phanerititic yet

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23
Q

Aphanitic

A

faster cooling, no large minierals
fine-grained

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24
Q

Glassy

A

instant cooling, no minerals
obsidian

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25
Q

Poryphitic

A

larger crystals with fine grained matrix
two different cooling histories
Darker minerals cool in magma chamber, gowing, then at surface, erupted, rest of melt quickly solidified
most are extrusive solidic rorck

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26
Q

Different textures

A

Vesocles
Pyroclastic

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27
Q

Vesicles

A

preserved gas bubble
vesicular basalt
scoria
pumice

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28
Q

scoria

A

basalltic, grade, small volcanoes that burst

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29
Q

Pumice

A

volatile-rick lava, very quickly quenched

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30
Q

Pyroclastic texture

A

volcanoes erupt explosively, pieces of lava, rocks, and ash are thrown into atmosphere and then deposited on surface as loose material- tephra
recognized by choaitc mix of crystals, angular glass shards, and rock fragments

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31
Q

tephra

A

the materials that cool back from atmosphere after an explosive volcano erupts

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32
Q

Compositional classification of igneous rocks

A

based on silica % and vol. % of silicate minerals

ultramafic
mafic
intermediate
felsic

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33
Q

Ultramafic

A

mantle rocks
contains mostly Fe and Mg (and Ca), least amount of Silica
peridotic
Komatile

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34
Q

Peridoitic

A

intrusive ultramafic rocks
abundant in Fe and Mg rich minerals
Olivine and Pyroxene

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35
Q

Komatile

A

extrusive, ultramafic lava
only erupted in Earth’s early history
no longer forms anymore

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36
Q

Mafic Igneous Rocks

A

Abundance of ferromagnesian minerals and plagioclase feldspar
rich in Fe and Mg and Silica poor (less poor than ultramafic, less rich in Fe and Mg)
mostly made of pyroxene and olivine
Gabbro
Basalt

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37
Q

Gabbro

A

Intrusive Mafic
mafic minerals like pyroxene, mixed amount of plagioclase feldspar
below Basalt in ocean crust

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38
Q

Basalt

A

Extrusive Mafic
commonly vesicular and aphantic, darker colored
sometimes phenocrysts of olvine or plagioclase
Basalt is top of ocean crust

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39
Q

Intermeditate Igneous rocks

A

comp. b/w felsic and mafic
usually contains roughly equaled amount of light ad dark minerals
Diorite and Andesite

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40
Q

Diorite

A

intrusive Intermediate rock
mix of light and dark minerals
Dalmation like appearance of black hornblende and biotite wand plagioclase feldspar

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41
Q

Andesite

A

Extrusive intermediate igneous rock
commonly grey and porphyritic
with feldspar and amphibole crystals

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42
Q

Felsic Igneous Rocks

A

more silica, less amount of Fe and Mg
abundant light colored minerals like quartz and feldspar
Granite and Rhyolite

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43
Q

Granite

A

intrusive felsic rocks
coarse grained, quartz, and large amount of pink K-feldspar and white plagioclase feldspar

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44
Q

Rhyolite

A

Extrusive felsic rock
fine-grained
formed from viscous (thick) lava

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45
Q

Bowen’s Reaction Series

A

idealized model for crystallization order of silicate mienrals in a magmadic system
Illustrates relationship of silica minerals and temperature

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46
Q

What is first minerals to crystallize

A

Dark ferromagnenese
ultramafic- mafic- intermediate- felsic

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47
Q

Steps for formation of Igneous rocks

A

melting occurs and depth (40-150km) and accumulated and rises b/c less dense (partial/complete melting)

flow throug cracks/fractures and can accumulate in magma chambers

solidify at depth or erupts on surface

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48
Q

What do melts depend on

A

Temperautre and Pressure

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49
Q

Solidus Line

A

The Green line
to left of it- rock still solid
to right of it- starts to liquidify (melt)

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50
Q

Why do the rocks melt

A

Atoms bond to form crystal lattice- fortified by pressure
temp is energy, higher temp, more energy, atoms vibrate and bonds start to break
high temp, bonds break, but pressure supports the bonds
higher pressure conditions need higher temps to melt

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51
Q

3 ways to produce melt

A

Decompression melting
Flux melting
Heat-Induced Melting

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52
Q

Decompression Melting

A

Caused by LOWERING OF PRESSURE w/o change in temp of hot rising mantle material
Pressure decrease with temp the same- form melt
Lower are, higher pressure, as rise, pressure decrease
Occur at divergent boundaries- MOR, continetal rifting, Hot spots

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53
Q

Where does Decompression Melting Occur

A

Divergent Boundaries- MOR and Continental Rifting
(mantle upwelling)
At Hotspots

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54
Q

Flux Melting

A

Addition of VOLATILES- allow rocks to melt at lower temp than would without
NO change in Temp or Pres.
adding volatiles can break atomic bonds
Occur at Subduction zone convergence

55
Q

volatiles

A

Water vapor, CO2, etc.

56
Q

Where does Flux Melting Occur

A

Subduction Zone convergence
H2O bonds, increase temp and pressure cause slab minerals to release their volatiles
Addition of H2O to mienrals- partial melt

57
Q

What additoin to mantle causes temp to increase and melt to begin

A

H2O

58
Q

Heat Induced Melting

A

melting caused by INCREASE in TEMP
melting of surrounding rocks from magma intrustion or rising melting plume
Conduction

59
Q

Conduction

A

Magma forms at shallow-moderate depths

60
Q

Partial Melting

A

Most rocks made of many different minerwals, some minerals begin melting sooner than others- partial melting
Resulting melt tends to be less Fe, Mg, Ca, and more silica, Na, K, Al

Ultramafic, Mafic, Intermediate, Felsic

61
Q

What, out of 4 types of igenous rocks, melt the quickest

A

Felsic

62
Q

What magma will be produced from melting of Mantle rock

A

Mafic (mantle is ultramafic)

63
Q

What will a partial melt from mafic rock produce

A

intermediate magma

64
Q

Qhat partial melt from intermediate produce

A

Felsic Magma

65
Q

What would a complete melt of mafic rock create

A

mafic lava

66
Q

what influences initial melt composition

A

Source rock
How much the source rock melts

67
Q

Magma Differentiation

A

process that can change a magma’s chemistry towards a more felsic composition over time

68
Q

Two main methods of Magma Differentiation

A

Fractionation
Assimilation

69
Q

Fractional Crystallization (Fractionantion)

A

magma composition evolve as minerals crystallize out. Remaining melt becomes more Silica rich and felsic

As mafic minerals crystallize, silica % increase, while Fe,Mg,Ca % decrease- taken to form mafic crystals

Mafic-> felsic for magma

70
Q

Assimilation

A

incorporates the host rocks that magma is intruding in
pieces of surrounding block get added to melt, pieces partially/completely melt
Adds or changes the magma comp.
Magma mixing

71
Q

Magma mixing

A

two different comp. (magma0 mix, causing magma comp. to be b/w the two magmas

72
Q

Oceanic-Oceanic Subduction zone

A

Partial melt of mantle (flux melting)- mafic magma
heat transger melting- intruding melt, fissured, or magma chambers
partial melt of oceanic crust and crystallization as magma cools- mafic intermediate comp.

73
Q

Continental Ocean Subduction Zone

A

Flux melting- Mafic Melt
Heat transger melting- intruding melt, fissures, or magma chambers
Partial melt of continental crust, assimilation, magma mizing, crystallization as magma cools- INtermeditate- felsic comp.

74
Q

Continental Collision Convergence

A

end of subduction- stops melt formation
2 crustal plates- one wedged under a little bit- buried, can release some volatiles- LITTLE bit of melt forming- solidifies back into igneous rocks
Felsic-intermeditate crystal rocks partially melt- felsic melts

75
Q

Divergent MOR

A

upwelling mantle melts by decomposition melts
Ultramafic mantle partially met- magic magma near surface

76
Q

Divergent Continental Rifts

A

Upwelling mantle melts by Decompression melting
Ultramafic mantle partiall melt- mafic magma and rocks
Magma intrusions- heat transfer melting- magic near sirface
crystallization, magma, mixing, assimilation, partial melt of felsic crust
intermediate-felsic melt and rocks

77
Q

Hotspots- oceanic crust

A

Decompression melting AND Heat-induced melting
oceanic crust- mafic to intermediate rocks
Ocenaic- mantle pick pile up, melt lithosphere mantle above, contineu up, crust thinner, magma not have as much time to evovle-
oceanic island

78
Q

Hotspot Contienntal Crust

A

Decompression melting AND Heat-induced melting
Continental crust- Mafic to felsic rocks
2 Scenarios:
-melt evolves, produce felsic-intermediate rocks
-large, explosive volcanic eruptions (calderas)
- pluime rise, fast and wide fractures, magma to surface
quickly, massive, basalt flows

79
Q

Viscosity

A

Resistance to flow
Depends primary on magma comp and temp

80
Q

Lower Viscoity

A

lava spread out- higher temp and fewwer silica chains
thin, flowly magma
Mafic-Intermediate

81
Q

HIgher Viscosity

A

lava piles up, lower temp and abundant silica chains
Viscous- thick, sticky magma (felsic-intermediate)

82
Q

volcano

A

type of land formation created when lava solidifies into rock

83
Q

Interplate volcanoes

A

located at active plate bloundary created by volcanism at MOR’s, Subduction zones, and Continental rifts

INter- between

84
Q

Intraplate volcanoes

A

located within tectonic plates, far removed from plate boundaries
most created from hotspots

Intra- within

85
Q

MOR’s (volcanoes)

A

most volcanism occurs here
least observed and famout- very deep in ocean
eruptions are slow, gentle, and oozing
basaltic
pillow basalts
deep-sea hydrothermal- black smokers

86
Q

Where does most volcanism occur

A

MOR

87
Q

pillow basalts

A

when basaltic lava erupts underwate, emerges in small explosions and/or pillow shaped structure

88
Q

Black smokers

A

aka deep sea hydrothermal

enable ecosystems to thrive deep underwater- around tall vents emitting black, hot mineral rich water

89
Q

Subduction Zones (volcano)

A

second most commonly found location

occurs in volcanic arc- promotes partial melting and magma differentiation

flux melting

mafic magma into a more silica rich magma

90
Q

second most commonly found location of volcanoes

A

Subduction zones

91
Q

what place turns mafic magma into more silica rich magma

A

subduction zone

92
Q

which place does basaltic magma come out

A

MORs
Continental rifts

93
Q

Continental Rifts (volcano)

A

Crustal thinning caused by diverging lithospheric plates

lower crust or upper mantle rises through thinned crust, release pressure, undergoes decompression- induced partial melting

Erupting as basaltic lava- flood basalts, cinder cones, basaltic lava flows

94
Q

Hotspots (volcano)

A

main source of intraplate volcanism

continental plate- intermediate amgma or felsic volcano

95
Q

Effusive volcano

A

non-explosive
low gas content and low viscosity magma
lava dome and lava flows

96
Q

Explosive pyroclastic eruptions

A

favored by high fas content and high viscosity magma
lava fountaining, pyroclastic flow, eruption column + ash cloud, tephra deposits

97
Q

what decides how violent the eruption will be

A

Viscosity and gas content

98
Q

Dissolved gases in a melt

A

Mostly H2O, CO2, SO2
bubbles form when dissolved gases are released from the magma as pressure decreases
magma rises- volume of gas expands

99
Q

Ophiolites

A

sequence of igneous rocks that represent a slice of oceanic crust

100
Q

mountainout volcanoes with central vents

A

Cinder/Scoria cones
Shield Volcanoes
Stratovolcanoes (composite)
Lava domes

101
Q

NOn-mountainous and lack of central vent

A

Calderas
Flood-basalts

102
Q

Cinder/Scoria COnes

A

low viscous lava and gassy
smallest volcanoes
conical, steep, symmetric sides
made of pyroclastic gramgents ejected from central vent

103
Q

What is the lava for Cinder/Scoria COnes

A

mafic lava with high volatiles (gassy)
small explosive to effusive

104
Q

What is the eruption for Cinder/Scoria COnes

A

fire fountaining, basalt flow
localized eruption area
frothy gas rich lava erupts up to crack the cinder cone. Over time, magma eventaully degrades and produce lava flow

105
Q

Shield Volcanoes

A

low viscosity - mafic magma chambers
low andgles and broad flanks
small vents and craters on top
varies in size- could be largest volcanoes
associated with hotspots, MOR, continental rifts

106
Q

Type of eruption for Shield Volcano

A

localized, effusive

107
Q

lava for Shield Volcano

A

mafic composition- layered with miltiple low viscosity lava flows

108
Q

what could be the largest of volcanoes

A

Shield Volcano

109
Q

what could be the smallest of volcanoes

A

Cinder/scoria cones

110
Q

Eruption for Shield Volcano

A

fissure eruption fed by dikes
lava flow from central vent
pillow basalts: eruption into water

111
Q

Lava tubes

A

after edge cools down faster, creates crust, unsulate lava in it, flow out, leave hollow space

112
Q

Flood Basalts

A

eruption of large volume, low viscosity lava
multiple eruptive centers from fissures, dikes
source- mantle plumes
extensive basalt lava flows

113
Q

Flood Basalts of World

A

India- Decan Trapps- 1/3 of country- extincion of dinosaurs
Siberia- Siberia Trapps- largest- Great Dying- 95% life extinct
COlumbia River Flood Basalts- youngest and smallest

114
Q

Flood Basalts implications

A

release of SO2 gas- acid rain and flects sunlight leading to global cooling
Release of CO2 Gas- global warming
long lasting eruptions- millions of years, gas adds to atmosphere, result in global climate change and lead to extinctions

115
Q

Stratovolcanoes

A

high Silicon and high viscosity
distinct crater at top- rises high above landscape
snow capped- steep symmetric flanks
layered w/ multiple lava flows, pyroclastic flows, ash layers

116
Q

Magma for Stratovolcanoes

A

Intermediate felsic magma chamber

117
Q

Lava flows for Stratovolcanoes

A

alternative moderate to high viscosity lava flows

118
Q

Eruptions for Stratovolcanoes

A

explosive pyroclastic

119
Q

Lava Domes

A

High viscosity
DOme features- plugging vent due to viscosity
highly fractured solidified lava
small to moderate in size
Often form within summit craters of stratovolcanoes or in Calderas

120
Q

Explosion for Lava Domes

A

Effusive but explosive erruption if dome collapse

121
Q

Calderas

A

moderate to very large circular, steep-walled depressions
caused by collapse of a volcano into the underlying magma chamber
associated with hotspots in continents or stratovolcanoes in subduction zones

122
Q

Composition of lava for Calderas

A

intermediate to felsic compositions

123
Q

eruption for Calderas

A

massive explosive eruptions- pyroclastic

124
Q

Lava Flow

A

low Viscosity, low gas content- local
changes landscape and makes area unhabitable
low viscosity flows longer distances before cooling
not high risk- forecast and evacuate

125
Q

Lava fountaining (fire fountain)

A

Low viscosity, high gas content
rapid formation, expansion of gas bubbles in the molten rock
most material falls back near central vent

126
Q

Slow moving lava

A

high viscosity, low gas content

127
Q

Explosive eruptions

A

high viscosity, high gas content

128
Q

Volcanic Gases

A

Active volcano (errupting, non-errupting) emit hazardous gases
CO2, SO2, H2S, Hydrogen Halides (HF, HCl, HBr)

129
Q

Laki

A

fissures erption- iceland
poisonous gas contaminate soil
25% of island’s human population

130
Q

Tephra

A

Explosive erruptions produce tephra
ash (<2mm) wind carry long distances
large accumulation- collapse buildings
cause respiratory issues (Silicosis)
clogs engines

131
Q

Volcanic Explosive Index

A

Measures how much volcanic material is ejected, the height of the material thrown into the atmosphere and how long the erruptions last

132
Q

Pyroclastic flows

A

fast flow of lava blocks, pumice, ash, and hot gases b/w 400F-1300F

133
Q
A

Geology (6 decks)

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