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Physical Geography > 3.1.5.3 - Volcanic Hazards > Flashcards

3.1.5.3 - Volcanic Hazards Flashcards

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1
Q

What are the characteristics of shield volcanoes?

A

Gentle slopes, wide base
Frequent eruptions, basic lava
High speed and low viscosity basaltic lava
Non-violent eruptions

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2
Q

Where are shield volcanoes found?

A

Constructive boundaries

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3
Q

What are the characteristics of composite volcanoes?

A 
Steep sides, cone shape
High with narrow base
Explosive eruptions
Layers of alternating ash and lava
Secondary/parasitic cones
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4
Q

Where are composite volcanoes found?

A

Destructive boundaries

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5
Q

What type of lava is rich in silica?

A

Slow flowing, viscous lava

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6
Q

What is generally erupted from volcanoes at destructive margins?

A

Lava bombs, ash, dust

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7
Q

What are primary effects?

A

Occur immediately along with the event, as a result of it

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8
Q

What are secondary effects?

A

Direct consequence of the event but not immediate

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9
Q

What are lava flows?

A

Streams of molten rock that pour or ooze from an erupting vent

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10
Q

What are the two types of lava?

A

Pahoehoe and A’a

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11
Q

What are the characteristics of pahoehoe lava?

A

Smooth, billowy surface, relatively thin

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12
Q

What are the characteristics of A’a lava?

A

Rough, jagged surface and thick lava

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13
Q

When lava solidifies, what does it form?

A

Igneous rock

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14
Q

How are gases released from magma?

A

As it rises to the surface and pressure decreases, gases are given off from the liquid portion

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15
Q

What are the main gases that lead to acid rain?

A

Carbon Dioxide and Sulphur Dioxide

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16
Q

How can acid raid impact the environment?

A

Polluting waterways and soil, killing plants and trees, dissolving rock

17
Q

What is ash made up of?

A

Fragments of pulverised rock, minerals and volcanic glass

18
Q

How is ash formed?

A

When dissolved gases in magma expand and escape violently into the atmosphere in explosive eruptions

19
Q

What impacts can ash have?

A

It can disrupt aviation, critical infrastructure eg electric power supply, and impact health

20
Q

What is a pyroclastic flow?

A

A high density mix of hot lava blocks, pumice, ash and volcanic gas

21
Q

How fast can pyroclastic flows move?

A

700km/h

22
Q

How do pyroclastic flows form?

A

Form collapse of an eruption column, colapse of lava domes, or ‘boiling over’

23
Q

Why are pyroclastic flows considered the most dangerous of volcanic hazards?

A

Their speed makes them inescapable, and due to high temperatures, it is impossible to survive one

24
Q

What is a lahar?

A

A moving mass of soils or mud made fluid by rain or snow moving down a steep slope

25
Q

What are lahars triggered by?

A

Heavy rain or large amounts of ground water flowing through rocks as it causes the top layer of soil to be removed

26
Q

What are tephras?

A

Rock fragments and particles thrown into the air by volcanic eruptions

27
Q

How can tephra lead to a pyroclastic flow?

A

If the rock fragments are hot enough to fuse together

28
Q

How can tephra cause a temperature drop?

A

If they reflect light and heat from the sun while in the atmosphere

29
Q

What are nuees ardentes?

A

Clouds of gas ash and lava fragments ejected from the volcano

30
Q

What can form part of a nuees ardentes?

A

Pyroclastic flow

31
Q

What are the main volcanic gases?

A

Sulphur Dioxide, Carbon Dioxide, Hydrogen Flouride, Hydrogen Chloride, water vapour

32
Q

How can volcanic gases have an impact?

A

Sulphur dioxide can cause acid rain and global cooling, Carbon Dioxide can cause global warming and Flourides can be lethal to animals

33
Q

What attempted control was used on Mauna Loa in 1935?

A

Bombing lava tubes

34
Q

How was Eldfell’s lava controlled on Heimay in 1973?

A

It was blasted with freezing sea water to cool it rapidly

35
Q

How was Mount Etna controlled in 1983?

A

Barriers of rock and ash were constructed to divert the lava

36
Q

How can volcanoes be monitored using geological observations?

A

A tiltmeter can be used to measure slope angle and bulges, and GPS to measure horizontal movements caused y expansion before an eruption

37
Q

How can volcanoes be monitored using seismic activity?

A

Seismographs measure earthquakes around a volcano as it prepares to erupt

38
Q

How can gas emissions be used to monitor volcanic activity?

A

As magma nears the surface and pressure decreases, gases escape. Sulphur dioxide is released as large amounts reach the surface, and concentrations can be measured

39
Q

What is the main disadvantage of monitoring volcanoes using seismic activity?

A

Most volcanoes are on plate boundaries, so it can be difficult to distinguish between volcanic earthquakes and routine tremors

Physical Geography (22 decks)

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