3.1.2:Volcanoes, processes,hazards,impacts Flashcards

1
Q

VEI

A

Volcano explosivity index
-volume of ejected product
-duration of main eruption
scale from 0 - 8

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2
Q

Limitations of VEI

A
  • all types of ejected material are treated alike

- no account of emissions eg: SO2 so impact on climate change hard to measure

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3
Q

Recurrance

A

how often an event occurs

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4
Q

Inverse relationship

A

The larger the event the less likely it is to occur regularly

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5
Q

Areal extent

A

Area covered by the tectonic event

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6
Q

Duration

A

Length of time the hazard exists for

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7
Q

Speed of onset

A

Amount of warning that event may occur

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8
Q

Predictability of occurrence

A

Earthquakes and volcanoes both have random temporal distribution which can add to their potential impacts

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9
Q

Gap theory

A

Length of time between past events

Can help prepare communities

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10
Q

Types of volcanic eruptions

6

A
  • Fissure
  • Shield
  • Acid/dome
  • Composite/strato
  • Ash/cinder
  • Calderas
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11
Q

Pyroclastic flows and surges

primary volcanic hazard

A

Bubbles in the magma burst and eject a mix of gases and material, the bursts surge downhill

  • results of frothing magma in the volcano vent
  • responsible for most volcanic deaths (to date)
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12
Q

Lava flows
2 types
(primary volcanic hazard)

A

more threat to property than human life

  • A’a
  • Pahoehoe
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13
Q

lava flows: Pahoehoe

A

Most liquid lava, wrinkled surface, moves quickly downhill

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14
Q

lava flows: A’a

A

Lava tends to form blocks, rough surface, moves slowly downhill

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15
Q

Airfall Tephra

primary volcanic hazard

A

Composed of fragmented material ejected by the volcano which then falls to the ground
-ash falls/clouds

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16
Q

Volcanic gases

primary volcanic hazard

A

Complex gas mixture:

  • water vapour
  • hydrogen
  • carbon monoxide/ dioxide
  • hydrogen sulphate
  • sulphur dioxide
  • chlorine
  • hydrogen chloride
17
Q

more on volcanic gases

A

CO causes deaths as its toxic

most deaths from CO2

18
Q

Primary volcanic hazards

4

A
  • pyroclastic flows+surges
  • lava flows
  • airfall tephra/ash falls
  • volcanic gases
19
Q

Secondary volcanic hazards

3

A
  • Lahars
  • volcanic landslides
  • Jokulhlaups
20
Q

Lahars

secondary volcanic hazard

A

Volcanic mud flows composed mainly of silt-sized sediments

  • 2nd biggest volcanic risk to human life
  • consist of ash, rock and torrential rain
  • dense, viscous
  • occur on steep volcanic flanks in tropical,humid or monsoon climates
21
Q

Volcanic landslides

secondary volcanic hazard

A

Landslides and debris avalanches
Gravity driven slides of masses of rock+volcanic material
occur during an eruption

22
Q

Ground deformation

A

Rising magma deforms volcanic slopes by bulging and triggering instability + landslides
pre eruption

23
Q

Jokulhlaups

secondary volcanic hazard

A

Water produced by melting ice is trapped in a lake between volcano + overlying glacier then water is released = violent flood
-in most sub-glacial eruptions