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EOSC 114 > Volcanoes 4 > Flashcards

Volcanoes 4 Flashcards

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

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

are hawaiian explosive eruptions safe?

A

yes

21
Q

Strombolian explosive eruptions

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

are Strombolian explosive eruptions safe?

A

still safe yeah

23
Q

which explosive eruption has a pulsatory/cyclical nature?

A

Strombolian

24
Q

vulcanian explosive eruptions

A
  • andesitic/rhyolite magma
  • super explosive
  • sustained explosions of ash (plume & fallout)
  • bombs / fragmentation
25
Q

are vulcanian explosive eruptions safe?

A

nope
can be lethal :<

26
Q

which explosive eruption can transition from effusive to explosive in seconds?

A

vulcanian

27
Q

plinian explosive eruptions

A
  • andesitic/rhyolite ash
  • violently explosive!
  • pyroclastic flows
  • large sustained ash column + fallout
28
Q

are plinian explosive eruptions safe?

A

nope super dangerous T^T

29
Q

phreatomagmatic explosive eruptions

A
  • contact btwn water and magma
  • violently explosive
  • water vapour cloud
  • crater and water
  • compressed ash
30
Q

a resurgent dome in a lake (of a crater) might explode in what style?

A

phreatomagmatic

31
Q

are phreatomagmatic explosive eruptions safe?

A

nope they super dangerous and exploooosive

32
Q

what condition might turn an unexplosive volcano to a super explosive and dangerous one?

A

water around the conduit

33
Q

pelean explosive eruptions

A

dome collapse

  • violently explosive!
  • ash fallouts
34
Q

rank the types of eruptions from mafic to felsic

A

(low viscosity & gas = safe)

hawaiian
strombolian
vulcanian
pelean
plinian

(high viscosity & gas = danger)

35
Q

eruption column height of hawaiian explosion

A

< 2km

36
Q

eruption column height of Strombolian explosion

A

< 10 km

37
Q

eruption column height of vulcanian explosion

A

< 20km

38
Q

eruption column height of plinian explosion

A

< 55km

39
Q

which is more explosive, vulcanian or plinian?

A

vulcanian :O

«go slides for chart: day 4»

40
Q

3 characteristics that define the VEI scale

A
  1. volume of ash produced
  2. height of eruption cloud above vent
  3. duration of eruption
41
Q

VEI

A

volcanic explosivity index
- describes size of an explosive eruption
- logarithmic
- mainly depends on total volume erupted explosively

(0 - 8)

42
Q

Hawaiian explosion would mostly be categorized as what VEI?

A

VEI 1

43
Q

vulcanian explosion would mostly be categorized as what VEI?

A

VEI 3

44
Q

plinian explosion would mostly be categorized as what VEI?

A

VEI 5

45
Q

example of ultraplinian eruption

A

VEI 6
Mt Pinatubo in 1991
- caused global temp to decrease cuz lots of SO2

EOSC 114 (30 decks)

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