Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Mcgill Geology > week 3 > Flashcards

week 3 Flashcards

1
Q

what are the igneous environments based ob?

A

There are two categories, they are based on cooling locale

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are the two major categories of igneous environments

A

extrusive settings - cool at or near the surface (cool rapidly, chill too fast to grow big crystals)

  • intrusive settings: cool at depth (lose heat slowly, crystals grow slowly and large)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

how does extrusive lava flow cools

A

as blanckets that often stack vertically

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

which type of lava can flow long distances

A

low-viscosity lava (basalt) extrusive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

how does the lava flow exit the volcano (extrusive settings)

A

exit volcanic vents and spread outward

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

T or F lava cools as it flows

A

T it cools as it flows, eventually solidifying

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

example of an explosive ash eruption

A

Mt. St-Helens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

caracteristics of an explosive ash eruption (extrusive)

A
  • high- viscosity felsic magma erupts explosively
  • yield huge volumes of ash that can cover large regions
  • pyroclastic flow: volcanic ash and debris avalanche (races down the colcanic slope as a density current, often deadly)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Euuroptions of Mt. Ranier

A

pyroclastic flows are often augmented by glacial melt water debirs flows that can travel many km from volcano

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

whats special about Mt. Ranier

A

in the holocene (geological time) (the last 12 000 yrs) have produced ‘Lahars” that have flowed through the valleys all the way to seattle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what are lahars

A

mud and water flow that happens from major explosif volcanos

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Eruption of Mt. Mazama

A

7800 yrs ago, erupted explosively releasing 46-58 km^3 of rock/dust materials that spread continent wide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Eruption Mt. Mazama vs St helens

A

mazama was 40 X greater than st helens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what did the mazama eruption leave behind

A

left a collpase “caldera” that is about 9 km in diameter called now “ crater lake”

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what formed lake toba in indonesia

A

75 000 yrs ago, larger super-volcanic eruption (Mt. Toba caldera) almost caused extinction of humans

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

how does magma invades preexisting wall rock (intrusive settings)

A
  • magma invades preexisting wall rock by percolating upward between grains and forcing open cracks
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what does the wall rock reveal when in contact with magma- intrusive

A

high heat

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what does the wall rock reveal when in contact with metamorphism

A

changes mineral forms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what is the baked zone

A

rim of heat-altered wall rock

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what is the chill margin

A

rim of quenched magma at contact

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what does the magma initiate when it invades colder wall rock

A
  • thermal contact metamorphism and melting
  • inflation of fractures, wedging wall rock apart
  • detachment of large wall rock blocks (stoping)
  • incorporation of wall rock fragments (xenoliths)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what happens when the magma that doesn’t reach the surface (intrusive settings)

A

the magma freezes slowly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what are tabular intrusions

A
  • tend to have uniform thicknesses
  • often can be traced laterally
    -have to major subdivisions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what are the two major subdivisions of tabular intrusions

A
  • sill: injected parallels to rock layering
  • dike: cuts across rock layering
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what to dikes and sills modify

A

modify invaded country rock

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

how do dikes and sills modify invaded country rock

A
  • they cause the rock to expand and inflate
  • they thermally alter the counrty rock
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

dikes caracteristics

A
  • cut across preexisting layering (bedding or foliation)
  • spread rocks sideways
  • dominate in extensional settings
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

sill caracterisitcs

A
  • are injected parallel to preexisting layering
    -are usually intruded close to the surface
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

both dikes and sills exhibit wide variability in

A
  • size
  • thickness (or width)
  • lateral continuity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

where do dikes somtimes occur

A

in swarms

ex: three dikes radiate away from shiprock, new mexico volcano has been eroded away into volcanic neck

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

ex of sill

A

antarctica, intrusion lifted the entire landscape above

basalt bc it is dark

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

what are plutons

A

subsurface cooled magma chambers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

what do plutons amass into

A

a batholith

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

what are batholiths

A
  • immense volumes of intrusives
  • from above subduction zones
  • may add magma for tens of Ma
  • batholiths mark former subduction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

ex of batholiths

A

north shore mountains of vancouver are the result of eriosion of an immense granitic plutons, magmatic intrusions, not volcanoes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

T or F intrusive and extrusive rocks commonly co-occur

A

T

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

how do intrusive and extrusive rocks co-occur

A
  • magma chambers feed overlying volcanoes
  • magma chambers may cool to become plutons
  • many igneous geometries are possible
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

how did Mt. Royal form

A

the gabbroic core of mt royal formed as an intusion at depth (1.3km around 125 Ma). Magma (came from the mantle bc mafic) (and its gabbro) rose into sedimentary section which has since been unroofed.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

with erosion what progressively deeper features are exposed

A
  • vertical dikes
  • horizontal sills
  • mushroom-shaped laccoliths
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

what is the influence on the landscape of intrusive and extrusive co-occur

A
  • continued upllift and erosion exposes a plution: (intrusive rocks are more resistant to erosion, so they stand high on the landscape)
  • unroofing (erosion of covering geological units) takes long periods of geologic time
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

what is exhumation

A

erosion of covering geological units over long periods of geologic time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

ex of ingeous rock used as a building stone extensively

A

office buildings, kitchens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

why are igneous rocks used as building stones

A
  • durable (resist erosion)
  • beautiful
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

what are igneous rocks often called

A

granite but not always granite

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

what are the useful descriptions of igneous rock

A

color and texture

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

size, shape and arragnment of the minerals of igneous rock

A
  • crystalline: interlocking crystals fit like jigsaw puzzle
  • fragmental: pieces of [reexisting rocks, often shattered
  • glassy: made of solid glass or glass shards
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

what gives an igneous rock its texture

A

the magma’s history

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

fine- grained texture

A
  • rapid cooling
  • crystals do not have time to grow
  • extrusive
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

coarse- grained textrue

A
  • slow cooling
    -crystals have a long time to grow
  • intrusive
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

porphyritic texture

A

(mixture of coarse and fine cystals)

  • indicates a two- stage cooling history:
  • initial slow cooling create large phenocrysts
  • subsequent eruption cools remaining magma more rapidly
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

fragmental textures what are they made from

A

preexisting rocks that were shattered by eruption

after fragmentation the pieces fall and are cemented

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

glassy textures caracteristics

A
  • solid mass of glass or crystals surrounded by glass
  • fracture conchoidally
  • result from extremely rapid cooling of lava
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

what is the classigication based on

A

composition and texture

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

felsic examples of texture

A

fine: rhyolite
coarse: granite

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

intermediate examples of texture

A

fine: andesit
coarsed: diorite

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

mafic examples rock of textrue

A

fine: basalt
coarsed: gabbro

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

ultramafic example rock and textrues

A

fine: Komatite
coarsed: peridotite

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

pyroclastic are fragments of what

A

violent eruptions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

what is tuff

A

volcanic ash that has fallen on land

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

what is volcanic breccia

A

made of larger volcanic fragments cemented together

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

where does igneous activity occur

A

in four plate textonic settings

  • in established or newly fromed tectonic plate boundaries
    except: hot spots which are independent of plates
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

what are the four plate-tectonic settings

A
  • isolated hot spots
  • volcanic arcs bordering deep ocean trenches
  • mmid-ocean ridges
  • continental rifts
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

most subaerial volcanoes on earth reside where

A

in arcs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

what type of tectonic plate boundaries do volcanic arcs have

A

convergent :

  • depp oceanic trenches and accretionary prisms
  • subducting oceanic lithosphere adds valatiles (water)
  • rocks of the asthenosphere partially melt
  • magma rises and creates volcanoes on overriding plate
  • magma may differentiate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
64
Q

how do volcanic arcs converging tectonic plates form?

A
  • depp oceanic trenches and accretionary prisms
  • subducting oceanic lithosphere adds valatiles (water)
  • rocks of the asthenosphere partially melt
  • magma rises and creates volcanoes on overriding plate
  • magma may differentiate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
65
Q

what are some examples of volcanic arcs

A
  • aleutian islands
    -japan
    -java and sumatra
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
66
Q

how many mantle plume hot spot volcanoes exist

A

about 50-100

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
67
Q

what do the plate boundaries of hot pot volcanoes look like

A

independant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
68
Q

hot spot volcanoes may erupt through what kind of crust

A

oceanic or continetal
- oceanic molsty mafic magma
- continental : mafic and felsic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
69
Q

what type of magma do you get from eru[tong from coeanic/continental crust

A
  • oceanic molsty mafic magma
  • continental : mafic and felsic
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
70
Q

examples of hot spots volcanoes

A
  • hawaii, new england and mt royal
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
71
Q

how are hot pot track created

A

burn a volcano chian through overiding tectonic plates

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
72
Q

what is the large igneous provinces (LIP)

A

unsually large outpourings of magma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
73
Q

what time of magma is the LIP

A

mostly mafic, include som felsic examples

74
Q

how is LIP formed

A

mantle plume first reaches the base of the lithosphere
- erupts huge volumes of magic magma as glood basalts

75
Q

caracteristics of magma (LIP)

A
  • magic
  • low viscosity
  • can flow tens to hundreds of kms
  • accumulate in thick piles
76
Q

what are continental rifts

A

places where continental lithosphere is being stretched

77
Q

what does rifting do to the lithosphere and how `

A

thins it
- causes decompressional melting of mafic rock
- heat transfer melts crust, creating felsic magmas

78
Q

example of continental rift

A

east african rift valley

79
Q

most igneous activity takes place at what type of ridge

A

mid-ocean ridges

80
Q

mid ocean ridges have what type of tectonic boundaries

A

divergent

81
Q

how are mid-ocean rifts from

A

-fidting spreads plates leading to decompression melting
- basaltic magma wells up and fills magma chamber
- solidifies as grabbro at depth
- moves upward to form dikes or extrude as pillow basalt

82
Q

what is a volcano?

A
  • an erupting vent through which molten rock surfaces
  • a mountain built from magmatic eruptions
83
Q

the first rock masses on earth resulted from what

A

volcanoes

84
Q

volcanoes are a clear result of what

A

tectonic activity

85
Q

name some vulnerable cities volcanoes pose a threat to

A
  • mexico city
  • seattle
  • naples, italy
86
Q

mount vesuvius

A
  • 79 C.E
  • erupted violently
  • pyroclastic debris destroyed pompeii
    -killed 20 000
  • record of roman life was preserved under ash
87
Q

eruptions are often unpredicle, they can do what to a mountain

A
  • build large mountains
  • blow mountains to bits
88
Q

what can a volcanic eruption do to a civilization (good and bad)

A
  • provide highly productive soils to feed a civilization
  • extinguish a civilization in a matter of minutes
89
Q

can volnic eruptions affect climate and civilizations

A

yes

90
Q

name the three forms products of colcanic eurption come in

A
  • lava flows : molten rock that moves over the ground
  • pyroclastic debris: fragments blown out of a volcano
  • volcanic gases: expelled vapor and aerosols
91
Q

lava flows how can lava be

A

thin and runny or thick and sticky

92
Q

flow style of lava deponds on what

A

viscocity

93
Q

what does lava viscosity depend on

A
  • composition: high silica, high viscosity
  • temperature
  • gas content
    -crystal content
94
Q

caracteristics of basaltic lava flow

A
  • very hot
  • low silica
  • low viscosity
  • thin and fluid
95
Q

what type of lava flow can flow rapidly (up to 30 km/h) and for long distances (hundreds of km )

A

basaltic lava flow `

96
Q

long-distances lava flow is facilitated by what

A

lava tubes

97
Q

what is the hawaiian word describing basalt with a glassy and ropy texture

A

pahoehoe (pa-hoy-hoy)when

98
Q

when does pahoehoe form

A

when extremely hot basalt forms a skin
- with flow, the skin is rolled into ropy ridges and furrows

99
Q

what is the hawaiian word describing basalt that solidifies with a jagges, sharp, angular texture

A

a’a’ (ah-ah)

100
Q

what does a’a’ form

A

when hot flowing basalt cools and thickens
- with flow, lava crumbles unto shards and fragments

101
Q

solidified flows may contract with vertical fractures creating what

A

polygonal columns (ex: giant’s Causway)

102
Q

what is pillow basalt

A

round blobs of basalt cooled in water

103
Q

what are pillow basalt formed

A
  • the pillow surface is cracked, quenched glass
  • lava pressure ruptures a pillow to form the next blob
  • the process repeats to form a mound of pillow basalts
104
Q

when are pillow basalt common?

A

on the mid-ocean ridge

105
Q

what is andesitic lava flow

A

higher SiO2 content in lava

106
Q

caracteristics of andesitic lava flow

A
  • they do not flow rapidly
  • they mound around the vent and flow slowly
107
Q

what happens to the crust in andesitic lava

A

it fractures into rubble, called blocky lava

108
Q

T or F andesitic lava flows remain close to the vent

A

T

109
Q

rhyolitic lava flow is common or rare

A

rarely flows

110
Q

what is special about rhyolite lava flows

A

has the highest SiO2 and the most viscous lava

111
Q

what does the lava do with rhyolitic lava

A

lava plugs the vent as a lava dome, sometimes the lava domes are blown to pieces

112
Q

volcanoes often erupt in what type of quantities of fragments

A

large

113
Q

volcaniclastic deposits include

A
  • pyroclastic debris: lava fragments that freeze in air
  • preexisting rock: blasted apart by eruption
  • landslide debris: blocks that have rolled downslpe
  • lahars: transported as water-rich slurries
114
Q

what do the released gases eject (pyroclastic debris, baslatic eurption)

A

clots and dropts of molten magma

115
Q

what forms dramatic fountains of lava

A

basaltic eruptions

116
Q

types a fragments (basaltic eurption)

A

lapilli- pea-sized fragments
- pele’s tears - frozen droplets
- pele’s hair - thin glass strands
- blocks: large fragments

117
Q

T or F andesitic or rhyolictic eruptions have more volcanic gases? what does that due

A

T: make these volcanoes more prone to explode and generate huge volumes of debris

118
Q

what are the different forms of debris made by andesitic or rhyolitic eurptions

A
  • pumice: frothy volcanic glass
  • ash: fragments less than 2 mm in diameter
  • pumice lapilli: angular pumice gragments
  • accretion lapilli: clumps formed by falling through moist air
119
Q

what is campi flegrei

A

the phlegraen fields: the site of the city of naples, italy siths within a caldera of a super volcano

major euprtions:
- 39000 yrs ago
- 15000 years ago
-(vesuvius/pompeii) CE79`

120
Q

what is pyroclastic flow

A
  • avalanches of hot ash that race downslope (200 to 450 degrees)
  • incinerate all in their path (can go 300km/h)
  • deadly
    -examples: mount vesuvius, mount pelée, mount augustine
121
Q

what are tephra

A

deposits of pyroclastic debris of any size from andesitic or rhyolitic eruptions

122
Q

what is tuff

A

lithified ash, may or may not contain lapilli fromed by andesitic or rhyolitic eruptions
- air-fall tuff: accumulations of ash that fall like snow
- ignimbrite: tuff deposited while hot that welds together

123
Q

when do wetted debris that move downhill occur (volcanic debirs flow)

A

occur where volcanoes are covered with ice and snow or drenched in abundant rain

124
Q

what is lahar

A

water-rich debris flow of ash and blocks (cam move very fast)

125
Q

how much of magma can be gas and what is its composition

A

up to 9 %
- water (h2O) - the most abundant gas
- carbon dioxide (CO2) - second in abundance
- sulfur dioxide (o2) and hydrogen sulfide (H2S) - rotten egg smell

126
Q

when are gases expelled during volcanic gas

A

gases aer expelled as magma rises (when the Pressure drops)

127
Q

how is aerosol sulfuric acid

A

SO2 reacts with water

128
Q

the violence of the volcanic eruption is controled by the style of gas that escapes (what are these styles)

A

low viscosity (basalt): easy escape so mellow eruption

  • high viscosity (rhyolite): difficult escape so violent release
129
Q

what are gas bubbles in rocks called

A

vesicles

130
Q

name the characteristic features of a volcano

A
  • magma chamber
  • fissures and vents
  • craters
  • calderas
  • distinctive profiles
131
Q

what are the distinctive profiles

A
  • shield volcanoes
  • scoria cones (cinder cones)
  • stratovolcanoes (composite volcanoes)
132
Q

where are magma chambers located in the volcano

A

in the the upper crust:
- usually an open cavity or area of highly fractured rock
- may contain a large quantity of magma

133
Q

the magma that cools in the magma chambers from what type of rock

A

intrusive igneous rock

134
Q

the magma that rises from the magma chamber froms what

A

a volcano

135
Q

how does the magma rise from the magma chamber

A

via a conduit to the surface

136
Q

magma may erupt along a fissure. what is a fissure

A

a linear tear

137
Q

fissure eruptions display what

A

a curtain of fire

138
Q

what do fissure evolve into

A

discrete vents and craters

139
Q

what is a crater

A

a bowl-shaped depression atop a volcano

140
Q

what is the size of a cvrater

A

up to 500m across and 200m deep

141
Q

how are craters fromed

A

form as erupted lava piles up around the vent

142
Q

where is a summit eruption located

A

within the summit crater

143
Q

where is the flank eruption located

A

along the side of the volcano

144
Q

what is a caldera

A

is a gigantic volcanic depression
- much larger than a crater (km)
- usually exhibit steep sidewalls and flat floors

145
Q

how are caldera’s formed

A

a magma chamber empties and the volcano collapses in

146
Q

what are shield volcanoes

A

broad, slighty dome-shaped (like an inverted shield)
- have a low slope and cover large geopgraphic areas

147
Q

how are shield volcanoes constructed

A

by lateral flow of low-viscosity basaltic lava

148
Q

ex of shield volcanoes

A

mauna loa on hawaii

149
Q

what are scoria cones (also called cinder cones)

A

conical piles of tephra; the smallest type of volcano

  • often symmetrical, with deep summit crater
  • typically from a single eruption event
150
Q

what are scoria cones built off

A

built of ejected lapilli and blocks piled at a vent

151
Q

what human practice can scoria cones be used for

A

the cinders are often used in garden decoration

152
Q

what are stratovolcanoes (also called composite volcanoes)

A
  • large, coned-shaped volcanoes with steeper slopes
153
Q

what are stratovolcanoes made of

A

made of alternating layers of lava, tephra, and debris

154
Q

example of stratovolcanoes

A

mount fuji, mount rainier, mount vesuvius

155
Q

what are the two dominant styles of eruption

A

effusive eruptions: produce lava flows
explosive eruptions: blow up

156
Q

effusive eruptions caracteristics

A
  • lava flows stream away from vents
  • lava lakes can form near, or inside, the vent
  • can produce huge lava fountains
157
Q

what type of magma are effusive eruptions common with

A

mafic magma (basalt) bc very hot and low viscosity

158
Q

explosive eruptions release pressure catastrophically… characteriristics

A
  • high gas pressure is from more viscous SiO2 rich magma
  • create pyroclastic flows and cover the land with tephra
  • can eject many cubic km of debris skyward
159
Q

what type of magma are explosive eruptions common with

A

mostly andesitic and rhyolitic compositions

160
Q

the eruptive style is related to volcano type example

A
  • effusive eruptions form shield volcanoes (hawaii)
  • small pyroclastic eruptions form scoria cones
  • alternating effusive and pyroclastic eruptions result in stratovolcanoes (mount Etna, Silicy)
  • large explosive eruptions create caldera (yellowstone)
161
Q

eruptions to remener example

A
  • phlegraean fields (naples)
  • taupo volcano (new Zealand)
  • Yellowstone National Park is par of a caldera 72 km across
  • Mt. Toba (almost extincted humans)
162
Q

recent eruptions to remember example

A

mount st helens
- earthquake-triggered landslide released pressure
- an initial vertical blast led to a much stronger lateral blast

163
Q

19th century eruptions to remember example

A

krakatau
- continued erupting through june and july
- august 27th 1883, island was obliterated: magma chmaber was breached by the ocean, island was blown to pieces, tsunami wave killed people)

164
Q

convergent boundaries give what type of volcanism

A

most subaerial volcanoes:
- arc volcanoes develop on overriding plates
- continental arcs and oceanic island arcs are common

165
Q

what is the ring of fire

A

ring of volcanoes convergent boundaries

166
Q

continental rifts give what type of volcanoes

A

gives volcano types reflecting:
- parial melting of the mantle
- partial melting of the crust
- effusive and explosive eruptions

ex: mount kilimanjaro (stratovolcano)

167
Q

oceanic hot spot what type of boundary

A

a plume under an oceanic plate that penetrates the plate and successively froms hawaiian islands:
- thousands of thin basalt flows build up trhouhg time
- building above sea level, basalt can flow long distances
- lava builds upward and outward and the island grows
- submarine slumps remove large masses of the volcano

168
Q

what are flood basalts

A

voluminous alva eruption above a plume :
- when a mantle plum intersects base of rifting lithosphere
- lava spreads over large areas; great thicknesses stack up
- creates a large ingeous province (LIP) ex: columbia river plateau

169
Q

iceland

A

is a hot spot that straddles the mid-atlantic ridge
- lava has built the hot spot/ridge above sea level
- the island is being torn apart by a divergent boundary
- volcanoes trace the mid-ocean ridge rift valley

170
Q

what are the volcanic hazard

A
  • cause great harm to humans
  • many populated areas have active volcanoes
  • understanding volcanic bheavior is best defense
171
Q

what are the eruptive volcanoes hazards

A
  • lava flows can destroy immovable objecets
  • threat of falling ash and lapilli (tephra is heavy causes roof collapses and it is gritty it abrades car and airplane engines), floodwaters easily move tephra as deadly lahars
  • threat of pyroclastic flows - ash clouds
172
Q

volcanic hazard: blast

A

rare, it is an explosion sideways, most eruptions are vertical

173
Q

volcanic hazards: landslides

A
  • eruptions trigger landslides:
  • large masses of material are deposited rapidly near vent
  • earthquakes initiate failure of unstable slopes
174
Q

volcanic hazards: lahars

A

more dense than water, carries everything away ex: nevado del ruiz colombia burried town of armero in 5 m of ash and mud

175
Q

volcanic hazards: earthquakes

A

moving magma causes earthquakes
- usually small magniture, they are frequent , can cause slope failures and damage structures

176
Q

volcanic hazards: tsunamis

A

water explosions create giant waves

177
Q

volcanic hazards : threat of gas and aerosols

A
  • aerosols cause respiratory problems
178
Q

how do protect from volcanoes?

A
  • recurrence interval (average time between eruptions): active (erupting), dormant (hastn erupted in a while), exctinct (not capable of erupting)
  • tectonics can shut off magma then erosion takes over
  • warning signs (earthquake, heat flow, chagnes in shape, emission of gas increases)

cant predict the exact timing or style

179
Q

what are ways we mitigate volcanic hazards

A
  • evacuation
  • diverting flows (with explosives, heavy equipment, seawater)
180
Q

can volcanic eruptions alter climate?

A

yes if large enough:
- ash and aerosols injected into stratosphere
- particles remain in stratosphere
- reflects solar radiation, causing atmospheric cooling

181
Q

are there volcanoes on other plantets?

A

volcanic activity is evident on the moon and planets ex: jovian moon lo has active volcanoes

182
Q

when did volcanic magmas formed the first surface rock?

A

around 4.3 Ga

183
Q

what happened to original rocks?

A
  • mostly lost to our observation
    -erosion
    -subsequent rocks have been multiply cycled trhough tectonic processes
  • what is left? a series of layered sediments has overlain the original record.

Mcgill Geology (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions