EOSC 114 > Volcanoes 4 > Flashcards

Volcanoes 4 Flashcards

(45 cards)

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1
Q

Mafic explosivity characteristics

A

low gas content and low viscosity
= quiet effusive eruptions

  • gas escapes cuz low viscosity, pressure released
    = safe
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2
Q

felsic explosivity characteristics

A

high gas content + gooey
= explosive eruptions

gas kept under increasing pressure cuz high viscosity
= dangerous

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3
Q

is mafic or felsic eruptions dangerous? Why?

A

felsic
- gas kept under increasing pressure cuz high viscosity

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4
Q

which conditions most favour explosive eruptions?

A
  • high viscosity
  • high gas content
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5
Q

gas escapes easily from ___ magma

A

mafic

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6
Q

gas escapes more difficultly from ___ magma

A

felsic

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7
Q

why do bubbles form when magma rises?

A

exsolve gases

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8
Q

which factors are important in determining eruption style?

A

viscosity and gas content

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9
Q

what happens as magma rises?

A

pressure decreases so bubbles form

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10
Q

viscosity (helps/fights) bubble growth

A

fights

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11
Q

fragmentation occurs when ___

A

pressure rises inside bubbles until they overcome the strength of the magma

= pyroclastic material is produced

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12
Q

what is tephra

A

pyroclastic material

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13
Q

name the four parts of volcanic conduit

A
  • disrupted magma (gas jet of pyroclastic material)
  • fragmentation surface
  • resolution interval (bubbly magma)
  • saturation surface
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14
Q

how does pyroclastic material form?

A
  1. rising magma (w/ dissolved gas) decompresses fast
  2. gas bubbles expand and blow up magma foam
  3. magma particles freeze in flight
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15
Q

what controls viscosity?

A

temperature

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16
Q

___ contents are important for explosivity

A

silica and volatile (gas) content
-> also temp controls viscosity!

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17
Q

what magma property is least important for explosivity?

A

density

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18
Q

what are the 5 styles of explosive volcanic eruptions?

A
  • hawaiian
  • strombolian
  • volcanian
  • plinian
  • phreatomagmatic
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19
Q

hawaiian explosive eruptions

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A
  • low viscosity
  • basaltic magma
  • effusive
  • lava flows
  • fire fountaining
  • lava lake
20
Q

are hawaiian explosive eruptions safe?

21
Q

Strombolian explosive eruptions

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A
  • basaltic/andesitic magma
  • mildly explosive
  • lava flows
  • fire fountaining
  • bombs
22
Q

are Strombolian explosive eruptions safe?

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A

still safe yeah

23
Q

which explosive eruption has a pulsatory/cyclical nature?

24
Q

vulcanian explosive eruptions

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A
  • andesitic/rhyolite magma
  • super explosive
  • sustained explosions of ash (plume & fallout)
  • bombs / fragmentation
25
are vulcanian explosive eruptions safe?
nope can be lethal :<
26
which explosive eruption can transition from effusive to explosive in seconds?
vulcanian
27
plinian explosive eruptions
- andesitic/rhyolite ash - violently explosive! - pyroclastic flows - large sustained ash column + fallout
28
are plinian explosive eruptions safe?
nope super dangerous T^T
29
phreatomagmatic explosive eruptions
- contact btwn water and magma - violently explosive - water vapour cloud - crater and water - compressed ash
30
a resurgent dome in a lake (of a crater) might explode in what style?
phreatomagmatic
31
are phreatomagmatic explosive eruptions safe?
nope they super dangerous and exploooosive
32
what condition might turn an unexplosive volcano to a super explosive and dangerous one?
water around the conduit
33
pelean explosive eruptions
dome collapse - violently explosive! - ash fallouts
34
rank the types of eruptions from mafic to felsic
(low viscosity & gas = safe) hawaiian strombolian vulcanian pelean plinian (high viscosity & gas = danger)
35
eruption column height of hawaiian explosion
< 2km
36
eruption column height of Strombolian explosion
< 10 km
37
eruption column height of vulcanian explosion
< 20km
38
eruption column height of plinian explosion
< 55km
39
which is more explosive, vulcanian or plinian?
vulcanian :O <>
40
3 characteristics that define the VEI scale
1. volume of ash produced 2. height of eruption cloud above vent 3. duration of eruption
41
VEI
volcanic explosivity index - describes size of an explosive eruption - logarithmic - mainly depends on total volume erupted explosively (0 - 8)
42
Hawaiian explosion would mostly be categorized as what VEI?
VEI 1
43
vulcanian explosion would mostly be categorized as what VEI?
VEI 3
44
plinian explosion would mostly be categorized as what VEI?
VEI 5
45
example of ultraplinian eruption
VEI 6 Mt Pinatubo in 1991 - caused global temp to decrease cuz lots of SO2
EOSC 114
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