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paper 3 > 14.2 > Flashcards

14.2 Flashcards

1
Q

what are the two classifications for volcanoes?

A

shape
type of eruption

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2
Q

lava plateaux/ fissure eruptions

A

shield volcanoes may erupt along lines of fissures rather than a central vent spilling liquid lava in successive layers

form broad plateaux such as the Colombia plateaux - often cut by deep canyons that expose the layers of rock - Grand Canyon

extensive lava flow are basaltic in nature so they can they can flow great distances

flat and featureless

macrofeature

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3
Q

basic/shield volcano

A

3-4 miles wide and 1500-2000m tall

eg Mauna Loa

built up slowly by accreation of thousands of flows of highly fluid basaltic

low silica so spreads over wide areas

cools as thins forming gently dipping sheets

lava erupts form rift vents along fractures that develops on the flanks of the cone

magma has low gas content and is low in silica allowing it to flow over wide distances

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4
Q

acid/ dome volcanoes

A

craggy, steep sloped convex sides covered with rock debris

typically found near large composite volcanoes

made of layers of lava

formed by repeated violent eruptions and slow moving lava flows which gives layered structure

magma is made of higher silica and high gas pressure making magma slow moving and explosive

eg Puy region of central france

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5
Q

ash-cinder cones

A

formed from ash, cinders and volcanic bombs ejected from crater

sides are steep and symmetrical

eg Patricutun, Mexico

may occur as single volcanoes or secondary volcanoes on the sides of stratovolcanoes or shield volcanoes

tephra ejected

lava cools and builds up around the vent forming crater

build up over time

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6
Q

composite volcano/ stratovolcano

A

tall and conical

built up from many layers of hardened lava, tephra, pumice and volcanic ash

steep profiles

periodically explosive and quiet eruptions

lava typically cools before spreading due to high viscocity

layered structure built up of sequential outpourings of eruptive materials

increase in temp causes dome to expand while its outer lava cools, causes newly hardened surface to splinter causing loose debris to fall from its sides

eg Mt Etna

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7
Q

caldera

A

bowl shaped depression formed when volcano collapses into void left by empty magma chamber

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8
Q

crater lake caldera

A

results from stratovolcano collapsing into its magma chamber during a violent eruption

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9
Q

basalstic caldera

A

concentric ring pattern resulting from a series of gradual collapses
often found at summit of shield volcanoes such as the craters at the top of Mauna Loa

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10
Q

resurgent calderas

A

largest volcanic structure
result from catastrophic eruptions that dwarf eruptions recorded by humans
Yellowstone Caldera

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11
Q

lava type explosive volcano

A

rhyolite anderite

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12
Q

lava type effusive volano

A

basalt

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13
Q

lava characteristics explosive

A

acid high % silica
high viscocity
lower temp @ eruption

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14
Q

lava characteristics effusive

A

low % silica
low viscocity
high temp @ eruption

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15
Q

style of eruption explosive

A

violent bursting of bubbles when magma reaches surfacr

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16
Q

style of eruption effusive

A

limited explosive force

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17
Q

materials erupted explosive

A

ash, dust, lava bombs, tephra

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18
Q

materials erupted effusive

A

gas, lava flows

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19
Q

frequency of eruption explosive

A

long periods with no acitivity

20
Q

frequency of eruption effusive

A

more frequent

21
Q

shape of volcano explosive

A

steep sided strato volcanoes
caldera

22
Q

shape of volcano effusive

A

gently sloping sides
shield volcanoes
lava plataux

23
Q

strato volcanoes

A

made up of layers of ash and acid lava
concave symmetrical profiles
complex internal networks of lava flows which form minor igneous features such as sills and dykes

24
Q

caldera

A

volcanic craters
2km in diameter
eruption destroys cone and underlying magma chamber is emptied - sides collapse
eg Krakatoa

25
Q

archipelago

A

closely grouped cluster of islands
Indonesia

26
Q

icelandic lava eruptions

A

large persistent fissure eruption
large quantities of basaltic lava

27
Q

hawaiian eruption

A

runny basaltic lava
travels down sides of volcano in lava flows
gases escape

28
Q

strombolian eruption

A

frequent gas explosions
large quantities of pyroclastic rock thrown out

29
Q

vulcanian eruption

A

blasts out of plugs fo sticky or cooled lava
fragments build up into cones of ash and pumice
viscous lava
large quantities of ash

30
Q

vesuvian eruption

A

powerful blasts of gas pushing ash clouds high into the sky
violent
ash covers surrounding areas

31
Q

plinian eruption

A

gas rushed up through sticky lava
ash and fragments
clouds of gas and volcanic debris - kilometres thick

32
Q

lava plateaux

A

magma erupts from multiple fissures
vast areas covered by free flowing lava
- flood basalts
millions of years of denudation create varied relief
eg Columbia plateaux covers 130,000km2

33
Q

shield volcanoes

A

effusive eruptions found at divergent plate boundaries
mostly occur at mid ocean ridges
successive flows accumulate forming huge volcanoes
eg Skjadbreidur, Iceland - example of above ground one

34
Q

eruptions at hot spot

A

fixed area of volcanic activity where magma from a rising mantle plume reaches the Earth’s surface
magma rises and forms island arc, and as plates move, island moves further away from hotspot and new island forms above hotspot
creates chain of islands
eg Hawaiian chain, pacific plate moves NW

35
Q

super volcanoes

A

volcano that erupts more than 1000km3 of material on a single eruption event
exist as giant calderas
eg Yellowstone last erupted 70,000 years ago

36
Q

what two factors need to be considered when assessing volcanic acitivity?

A

magnitude - amount of material erupted
intensity- the speed at which material is erupted

37
Q

Volcanic Explosivity Index

A

combines magnitude and intensity into a single number on a scale 0-8
not good for effusive

38
Q

what factors are taken into consideration when assessing explosivity of the eruption?

A

volume of erupted material
height ejected material reaches
time duration

39
Q

lava flows

A

PRIMARY
impacts dependent on type of lava
basaltic lava is free flowing and can cover significant distances
eg Hawaii 2015, covered 20km
acidic lava is thicker and bulldozes everything in its path

40
Q

pycrolastic flows

A

PRIMARY
combination of hot gases (500+ degrees), ash and rock fragments travelling at high speeds 100km/h
follow contours of ground
inhaling these gases causes instant death
eg Pompeii

41
Q

tephra

A

any material ejected from a volcano into the air
ranges in size from very fine- Pele’s hair, Pele’s tears to ballistic material - lava bombs, Lapilli
buries farmland in layers of ash
weight of accumulated ash causes buildings to collapse and people with respitory issues are at risk
eg, eruption of Eyjafjallajokul 2010 caused cancellation of 100,000 flights

42
Q

toxic gases

A

PRIMARY
eruptions emit CO2, carbon monoxide and sulfur dioxide
deadly threat to human and livestock populations
can causes acid rain
also can cause limnic eruptions eg Lake Nyos killed over 1000 people

43
Q

lahars

A

SECONDARY
mud flow with consistency of concrete
snow and ice melt and mix with mud and flow rapidly down cone
travel at 50km/h
bury and destroy everything in their path
eg Nevado de Ruiz, Columbia, 23,000 killed

44
Q

floods

A

SECONDARY
eruptions beneath an ice field or glacier cause rapid melting
vast quantities of water accumulate until they find an exit from under the ice
aka jokulhlaup

45
Q

tsunami

A

violent eruptions of island volcanoes can cause massive displacement of ocean water and waves travleling at 600km/h
eg Krakotoa, killed 36,000

46
Q
A

paper 3 (13 decks)

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