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AQA A Level Geography - PHYSICAL > ✅HAZARDS 3.1.5.3 - Volcanic Hazards > Flashcards

✅HAZARDS 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

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17
Q

What is ash made up of?

A

Fragments of pulverised rock, minerals and volcanic glass

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18
Q

How is ash formed?

A

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

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19
Q

What impacts can ash have?

A

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

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20
Q

What is a pyroclastic flow?

A

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

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21
Q

How fast can pyroclastic flows move?

A

700km/h

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22
Q

How do pyroclastic flows form?

A

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

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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

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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

40
Q

Magma type: Basaltic

A

Silica content: less than 50% (low viscosity/ very runny)
Forms Basalt

41
Q

Magma Type: Andesitic

A

Silica: 50-70% (medium viscosity)
Forms Granite

42
Q

Magma type: Rhyolitic

A

Silica: over 70% (high viscosity, not runny)
Forms Granite

43
Q

Plinian/ Vesuvian Eruption Features, example

A

Mt. St. Helens 1980
High silica content (makes eruptions long, up to days, and less frequent)
Rhyolitic
Explosive
Big plume
Fast Lava

44
Q

Vulcanian Eruption Features

A

All types of magma
Violent gas explosions
Very viscous lava
Clearing of a blocked vent, releases lots of ash
Katmai, Alaska

45
Q

Icelandic/ Fissure Eruption Features

A

Lots of basaltic, from a fissure
At constructive boundaries
Such as Deccan Plateaux, India

46
Q

Hawaiian Eruption Features

A

Basaltic, Lava very runny. Can form shield volcanoes when solidifies
Constructive
Generally not explosive

47
Q

Strombolian Eruption Features

A

Basaltic magma
But viscous lava due to silica
Short bursts of thick lava
Constructive
Mt Etna (used to have vulcanian but change in pressure makes them strombolian now)

48
Q

Stratovolcano (composite) Volcano features

A

Made of layers of ash and andesitic lava
Destructive margins
Explosive

49
Q

Basic Shield Volcano

A

Gently sloping cone of basaltic Lava
constructive margins
Gentle Eruptions
Mauna Loa, Hawaii

50
Q

Acid Dome Volcano

A

Steep- sided cone formed from Rhyolitic lava which can’t travel far solidifies in vents making explosive unpredictable eruptions
Destructive margins
Mt Pelee

51
Q

Caldera volcano

A

Cauldron-shaped summit, can fill with water. E.g., Lake Nyos, Cameroon
Formed by gases built up beneath blocked vent
Big eruptions
Destructive margins

52
Q

Fissure Volcano

A

Elongated spit
Basaltic Lava
Constructive margins, ocean ridges
Creates lots of plateaus due to fast flowing lava solidifying
Heimaey, Iceland

53
Q

Active Volcano definition

A

Has had an Eruption in the last 10,000 years
Could still be dormant

54
Q

Extinct Volcano definition

A

Hasn’t erupted in the last 10,000 years & isn’t expected to in comparable time scale

55
Q

Features of Block lava flow

A

High acidity so doesn’t flow well. Forms block shapes

56
Q

Features of A’a lava flows

A

More basaltic than block lava flows, so not as rough
Slow
Irregular

57
Q

Features of Pahoehoe lava flows

A

Lower viscosity, flows further
Can form lava tubes/ caves due to far distance
When cools down becomes more viscous, can become A’a

58
Q

Pillow Lava flows

A

Flows under water that have become solid rock, spherical shape.

AQA A Level Geography - PHYSICAL (35 decks)

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