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AS Geography > Volcanic Hazards > Flashcards

Volcanic Hazards Flashcards

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1
Q

How are volcanoes formed at destructive boundaries?

A
  • Denser O plate is subducted and material melts
  • Molten material is less dense and rises in the mantle and erupts at the surface
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2
Q

How are volcanoes formed at constructive boundaries?

A
  • Plate diverge leaving a gap in the crust
  • Magma rises due to low pressure and erupts
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3
Q

What are volcanoes at destructive boundaries like?

A
  • Eruption of andesitic lava (high viscosity)
  • Eruption of tephra
  • Explosive eruptions (gas doesn’t escape as easily from the lava)
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4
Q

What are volcanoes at constructive boundaries like?

A
  • Eruption of basaltic lava (low viscosity)
  • Lava flows longs distances
  • Effusive eruptions (gas escapes easily from the lava)
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5
Q

What are the primary hazards of a volcanic eruption?

A
  • Tephra
  • Pyroclastic flow
  • Lava flow
  • Volcanic gases
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6
Q

What is tephra?

A

Large fragments of ash and rock (volcanic bombs) ejected into the atmosphere

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7
Q

What is pyroclastic flow?

A

Gas and tephra collapses down the slopes of a volcano at up to 700 km/h

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8
Q

What are lava flows?

A

Lava pours from an erupting vent at constructive boundaries

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9
Q

What are volcanic gases?

A

Gases such as CO2, CO and SO2 escape during an eruption

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10
Q

What are the secondary hazards of a volcanic eruption?

A
  • Lahars (mudflows)
  • Flooding (jokulhlaup)
  • Acid rain
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11
Q

What are lahars?

A

Volcanic material is mobilised by melting ice and snow and moves at up to 60 km/h

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12
Q

What is a jokulhlaup?

A

Serious flooding when an eruption takes place beneath glaciers and ice caps

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13
Q

What is acid rain?

A

SO2 combined with atmospheric moisture to produce acidic precipitation

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14
Q

What is the distribution of volcanoes?

A
  • Plate boundaries and hotspots
  • The Pacific Ring of Fire (high volcanic and seismic activity)
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15
Q

How can eruptions be defined?

A
  • Explosive (high VEI)
  • Effusive (low VEI)
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16
Q

How is eruption magnitude measured?

A

VEI - Volcanic Explosivity Index (logarithmic scale from 0-8)

17
Q

What is VEI determined by?

A

Volume of ejected material (tephra)

18
Q

How is eruption frequency determined?

A
  • Volcanoes are classified as active, dormant or extinct
  • Effusive eruptions are more frequent than explosive ones
19
Q

Are volcanic eruptions regular?

A

Mostly when on the same plate boundary - can be irregular though

20
Q

How can volcanoes be monitored?

A
  • Gas emissions
  • Seismic activity
  • Ground deformation
  • Thermal monitoring
21
Q

How can gas emissions predict an eruption?

A
  • SO2 release
  • Gas levels drop rapidly just before an eruption
22
Q

How can ground deformation predict an eruption?

A
  • Magma movement in the lithosphere can deform the ground above
  • Volcanoes swell prior to an eruption as magma gathers
23
Q

How can seismic activity predict an eruption?

A
  • Increased frequency and intensity of seismic activity can signal an eruption
  • Harmonic tremors (magma pushes against rock and creates a humming effect)
24
Q

What are the social impacts of volcanic events?

A
  • Loss of life
  • Homelessness
  • Trauma/PTSD
  • Fires break out
25
Q

What are the economic impacts of volcanic events?

A
  • Travel disruption
  • Businesses destroyed
  • Impact on tourism
  • Loss of jobs
26
Q

What are the environmental impacts of volcanic events?

A
  • Habitat destruction
  • Acid rain
  • Release of greenhouse gases
  • Wildlife killed
27
Q

What are the political impacts of volcanic events?

A
  • Government buildings destroyed
  • Conflict over food security and insurance payouts
28
Q

What are the short-term responses to a volcanic event?

A
  • Call for international aid
  • Evacuations/exclusion zones
  • Food and water distribution
  • Temporary infrastructure such as shelters for the homeless
29
Q

What are the long-term responses to a volcanic event?

A
  • Improvements to the local economy
  • Relocation
  • Resilience education
  • Rebuilding infrastructure
30
Q

How can volcanic hazards be prevented?

A

They cannot - risk can be prevented by not allowing building near volcanoes

31
Q

How can volcanic hazards be mitigated?

A
  • Construct lava flow diversion channels
  • Strengthen existing buildings
  • Drain lakes in craters to reduce risk of lahars
32
Q

How can society adapt to volcanic hazards?

A
  • Move away from high risk areas
  • Capitalise on tourism opportunities
33
Q

What do volcanoes at destructive boundaries look like?

A

Steep-sided/composite volcanoes

33
Q

What do volcanoes at constructive boundaries look like?

A

Gentle-sloped/shield volcanoes

AS Geography (33 decks)

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