CH. 4 Flashcards
(133 cards)
1
Q
What is the bulk of Earth’s crust
A
Igneous Rocks
2
Q
How are igneous rocks formed
A
cooling anf solidifaction of magma- minerals crystallize
3
Q
Two different types of igneous rocks
A
extrusive and intrusive
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
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
6
Q
Pluton types
A
Igneous Sikes
Igneous Sills
Laccoliths
Stocks
Batholiths
7
Q
Igneous dikes
A
Intrusion that cuts across layers (vertical)
8
Q
Igneous Sills
A
Intrusion that runs parallel to layers (horizontal)
9
Q
Laccoliths
A
Lens shape, causes surface doming
10
Q
Stocks
A
<100 Km^2, irregular shaped
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
12
Q
Irregular plutons
A
stocks
Columnar joints
Batholiths
13
Q
Columnar Joints
A
way it cools, cracks form, cool outward to inward
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
15
Q
Order of how silica mineral crystalize from melt associated with what
A
melt temp and composition
16
Q
CHaractersitics of how to classify rock
A
Texture and composition
17
Q
texture
A
crystal grain size and others
Cooling rate influence texture
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)
19
Q
Various sizes of minerals classification
A
Pegmatitic
Phanerititic
medium grained
APHANITIC
glassy
Poryphitic
20
Q
Pegmatitic
A
Huge crystals
VERY slow crystallization
greater than 71 cm
21
Q
Phanerititic
A
Coarse grained- slow crystallization, large crystals
22
Q
medium grained
A
still big- below ground- but not quite at phanerititic yet
23
Q
Aphanitic
A
faster cooling, no large minierals
fine-grained
24
Q
Glassy
A
instant cooling, no minerals
obsidian
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Poryphitic
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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Different textures
Vesocles
Pyroclastic
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Vesicles
preserved gas bubble
vesicular basalt
scoria
pumice
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scoria
basalltic, grade, small volcanoes that burst
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Pumice
volatile-rick lava, very quickly quenched
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Pyroclastic texture
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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tephra
the materials that cool back from atmosphere after an explosive volcano erupts
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Compositional classification of igneous rocks
based on silica % and vol. % of silicate minerals
ultramafic
mafic
intermediate
felsic
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Ultramafic
mantle rocks
contains mostly Fe and Mg (and Ca), least amount of Silica
peridotic
Komatile
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Peridoitic
intrusive ultramafic rocks
abundant in Fe and Mg rich minerals
Olivine and Pyroxene
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Komatile
extrusive, ultramafic lava
only erupted in Earth's early history
no longer forms anymore
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Mafic Igneous Rocks
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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Gabbro
Intrusive Mafic
mafic minerals like pyroxene, mixed amount of plagioclase feldspar
below Basalt in ocean crust
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Basalt
Extrusive Mafic
commonly vesicular and aphantic, darker colored
sometimes phenocrysts of olvine or plagioclase
Basalt is top of ocean crust
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Intermeditate Igneous rocks
comp. b/w felsic and mafic
usually contains roughly equaled amount of light ad dark minerals
Diorite and Andesite
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Diorite
intrusive Intermediate rock
mix of light and dark minerals
Dalmation like appearance of black hornblende and biotite wand plagioclase feldspar
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Andesite
Extrusive intermediate igneous rock
commonly grey and porphyritic
with feldspar and amphibole crystals
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Felsic Igneous Rocks
more silica, less amount of Fe and Mg
abundant light colored minerals like quartz and feldspar
Granite and Rhyolite
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Granite
intrusive felsic rocks
coarse grained, quartz, and large amount of pink K-feldspar and white plagioclase feldspar
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Rhyolite
Extrusive felsic rock
fine-grained
formed from viscous (thick) lava
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Bowen's Reaction Series
idealized model for crystallization order of silicate mienrals in a magmadic system
Illustrates relationship of silica minerals and temperature
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What is first minerals to crystallize
Dark ferromagnenese
ultramafic- mafic- intermediate- felsic
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Steps for formation of Igneous rocks
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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What do melts depend on
Temperautre and Pressure
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Solidus Line
The Green line
to left of it- rock still solid
to right of it- starts to liquidify (melt)
50
Why do the rocks melt
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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3 ways to produce melt
Decompression melting
Flux melting
Heat-Induced Melting
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Decompression Melting
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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Where does Decompression Melting Occur
Divergent Boundaries- MOR and Continental Rifting
(mantle upwelling)
At Hotspots
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Flux Melting
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
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volatiles
Water vapor, CO2, etc.
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Where does Flux Melting Occur
Subduction Zone convergence
H2O bonds, increase temp and pressure cause slab minerals to release their volatiles
Addition of H2O to mienrals- partial melt
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What additoin to mantle causes temp to increase and melt to begin
H2O
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Heat Induced Melting
melting caused by INCREASE in TEMP
melting of surrounding rocks from magma intrustion or rising melting plume
Conduction
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Conduction
Magma forms at shallow-moderate depths
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Partial Melting
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
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What, out of 4 types of igenous rocks, melt the quickest
Felsic
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What magma will be produced from melting of Mantle rock
Mafic (mantle is ultramafic)
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What will a partial melt from mafic rock produce
intermediate magma
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Qhat partial melt from intermediate produce
Felsic Magma
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What would a complete melt of mafic rock create
mafic lava
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what influences initial melt composition
Source rock
How much the source rock melts
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Magma Differentiation
process that can change a magma's chemistry towards a more felsic composition over time
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Two main methods of Magma Differentiation
Fractionation
Assimilation
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Fractional Crystallization (Fractionantion)
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
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Assimilation
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
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Magma mixing
two different comp. (magma0 mix, causing magma comp. to be b/w the two magmas
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Oceanic-Oceanic Subduction zone
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
Continental Ocean Subduction Zone
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.
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Continental Collision Convergence
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
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Divergent MOR
upwelling mantle melts by decomposition melts
Ultramafic mantle partially met- magic magma near surface
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Divergent Continental Rifts
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
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Hotspots- oceanic crust
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
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Hotspot Contienntal Crust
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
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Viscosity
Resistance to flow
Depends primary on magma comp and temp
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Lower Viscoity
lava spread out- higher temp and fewwer silica chains
thin, flowly magma
Mafic-Intermediate
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HIgher Viscosity
lava piles up, lower temp and abundant silica chains
Viscous- thick, sticky magma (felsic-intermediate)
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volcano
type of land formation created when lava solidifies into rock
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Interplate volcanoes
located at active plate bloundary created by volcanism at MOR's, Subduction zones, and Continental rifts
INter- between
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Intraplate volcanoes
located within tectonic plates, far removed from plate boundaries
most created from hotspots
Intra- within
85
MOR's (volcanoes)
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
Where does most volcanism occur
MOR
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pillow basalts
when basaltic lava erupts underwate, emerges in small explosions and/or pillow shaped structure
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Black smokers
aka deep sea hydrothermal
enable ecosystems to thrive deep underwater- around tall vents emitting black, hot mineral rich water
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Subduction Zones (volcano)
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
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second most commonly found location of volcanoes
Subduction zones
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what place turns mafic magma into more silica rich magma
subduction zone
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which place does basaltic magma come out
MORs
Continental rifts
93
Continental Rifts (volcano)
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
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Hotspots (volcano)
main source of intraplate volcanism
continental plate- intermediate amgma or felsic volcano
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Effusive volcano
non-explosive
low gas content and low viscosity magma
lava dome and lava flows
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Explosive pyroclastic eruptions
favored by high fas content and high viscosity magma
lava fountaining, pyroclastic flow, eruption column + ash cloud, tephra deposits
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what decides how violent the eruption will be
Viscosity and gas content
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Dissolved gases in a melt
Mostly H2O, CO2, SO2
bubbles form when dissolved gases are released from the magma as pressure decreases
magma rises- volume of gas expands
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Ophiolites
sequence of igneous rocks that represent a slice of oceanic crust
100
mountainout volcanoes with central vents
Cinder/Scoria cones
Shield Volcanoes
Stratovolcanoes (composite)
Lava domes
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NOn-mountainous and lack of central vent
Calderas
Flood-basalts
102
Cinder/Scoria COnes
low viscous lava and gassy
smallest volcanoes
conical, steep, symmetric sides
made of pyroclastic gramgents ejected from central vent
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What is the lava for Cinder/Scoria COnes
mafic lava with high volatiles (gassy)
small explosive to effusive
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What is the eruption for Cinder/Scoria COnes
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
Shield Volcanoes
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
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Type of eruption for Shield Volcano
localized, effusive
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lava for Shield Volcano
mafic composition- layered with miltiple low viscosity lava flows
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what could be the largest of volcanoes
Shield Volcano
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what could be the smallest of volcanoes
Cinder/scoria cones
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Eruption for Shield Volcano
fissure eruption fed by dikes
lava flow from central vent
pillow basalts: eruption into water
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Lava tubes
after edge cools down faster, creates crust, unsulate lava in it, flow out, leave hollow space
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Flood Basalts
eruption of large volume, low viscosity lava
multiple eruptive centers from fissures, dikes
source- mantle plumes
extensive basalt lava flows
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Flood Basalts of World
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
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Flood Basalts implications
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
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Stratovolcanoes
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
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Magma for Stratovolcanoes
Intermediate felsic magma chamber
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Lava flows for Stratovolcanoes
alternative moderate to high viscosity lava flows
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Eruptions for Stratovolcanoes
explosive pyroclastic
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Lava Domes
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
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Explosion for Lava Domes
Effusive but explosive erruption if dome collapse
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Calderas
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
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Composition of lava for Calderas
intermediate to felsic compositions
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eruption for Calderas
massive explosive eruptions- pyroclastic
124
Lava Flow
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
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Lava fountaining (fire fountain)
Low viscosity, high gas content
rapid formation, expansion of gas bubbles in the molten rock
most material falls back near central vent
126
Slow moving lava
high viscosity, low gas content
127
Explosive eruptions
high viscosity, high gas content
128
Volcanic Gases
Active volcano (errupting, non-errupting) emit hazardous gases
CO2, SO2, H2S, Hydrogen Halides (HF, HCl, HBr)
129
Laki
fissures erption- iceland
poisonous gas contaminate soil
25% of island's human population
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Tephra
Explosive erruptions produce tephra
ash (<2mm) wind carry long distances
large accumulation- collapse buildings
cause respiratory issues (Silicosis)
clogs engines
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Volcanic Explosive Index
Measures how much volcanic material is ejected, the height of the material thrown into the atmosphere and how long the erruptions last
132
Pyroclastic flows
fast flow of lava blocks, pumice, ash, and hot gases b/w 400F-1300F
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