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Geography- Hazards > Volcanic Hazards > Flashcards

Volcanic Hazards Flashcards

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1
Q

Shield volcano boundary

A

Constructive (and hotspots)

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2
Q

Formation of shield volcanoes

A 
Plates move apart
Magma rises to surface, cools = new crust
Sea floor spreading
Layers built by eruptions 
Sea floor spreading = plates move apart
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3
Q

Shield volcano example

A

Eyjafjallajokull, Iceland

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4
Q

Shield volcano characteristics

A

Gentle sloping sides
Wide base
Low viscosity lava - BASALTIC
Frequent, basic lava eruptions

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5
Q

Shield volcano explosivity

A

Low, as magma under little pressure

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6
Q

Composite volcano boundary

A

Destructive

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7
Q

Formation of composite volcanoes

A 
Plates move towards eachother 
Oceanic, denser, subducts 
Beinoff Zone
Less dense molten material rises
Layers of ash and lava build
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8
Q

Composite volcano example

A

Montserrat

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9
Q

Composite volcano characteristics

A

Steep sided
Layers of ash, dust, lava
Viscous lava - RHYOLITIC
Long dormant periods

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10
Q

Composite volcano explosivity

A

High, as magma rises in plumes through fissures in buckled continental plate- high pressure

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11
Q

Volcanoes in rift valleys formation

A 
Rising magma 
Brittle continental crust buckles and fractures
= Fault lines
Plates move further apart  
Crust between parallel faults drops down
= Rift Valley
Thin crust 
Magma forces its' way to the surface
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12
Q

Volcanoes at hotspots formation

A

Concentration of radioactive elements below crust
Plume of magma rises
Breaks through surface

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13
Q

Why do extinct volcanoes subside at hotspots?

A

As they have put so much pressure on the crust

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14
Q

VEI

A

Volcanic Explosivity Index

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15
Q

VEI meaning

A 
Logarithmic scale (0-8) 
Measures height of eruption column and volume of tephra erupted
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16
Q

Disadvantages of VEI

A

Doesn’t consider climate impact

Ash, lava and lava bombs all treated alike

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17
Q

Icelandic Eruption

A

Basaltic lava flows gently from fissures

18
Q

Highest and Lowest Categories on VEI?

A 
Icelandic = lowest
Plinian = highest
19
Q

Plinian Eruption

A

Highly explosive and violent, with tephra and pyroclastic fall out

20
Q

Tephra Meaning

A

Solid material (ash-bombs) ejected into the atmosphere

21
Q

Pyroclastic Flow / Nuees Ardentes Meaning

A

Fast moving current of hot gas and tephra
Up to 1000°c
Little warning = death and destruction

22
Q

What are the secondary effects of pyroclastic flows?

A

Snow melt

Damming streams

23
Q

What are the secondary effects of tephra?

A

Grounding air traffic
Destroy vegetation- famine
Improve soil fertility

24
Q

What 4 factors affect the distance tephra travels?

A

Height of eruption column
Temperature of air
Wind speed
Wind direction

25
Q

What 4 things are lava flows affected by?

A

Land steepness
Extrusion rate
Silica content
Flow temperature

26
Q

What temperatures are lava flows between?

A

550°c - 1400°c

27
Q

Why are lava flows not a big hazard?

A

Because of their slow speeds

28
Q

Mudflow / Lahar Meaning

A

Volcanic material + water (rainfall or ice melt)

29
Q

What’s the difference between mudflows and lahars?

A

Lahars set like concrete

30
Q

Name some of the gases released by a volcano

A

Water vapour
Carbon dioxide
Sulphur dioxide- acid rain

31
Q

Where does CO2 seep through the volcano and kill plants?

A

Mammoth Mountain

32
Q

Why are tiltmeters and GPS used to monitor volcanoes?

A

Measure slope angles

Indicates expanding magma chamber

33
Q

Why are seismometers and seismographs used to monitor volcanoes?

A

Microquakes

Rising magma fractures overlying rock

34
Q

Why are magnetometers used to monitor volcanoes?

A

Changing magnetism indicates rising iron-rich magma

35
Q

Protection- Land Use Planning

A

Build houses away from high risk areas

36
Q

Preparation- Why should there be good communication systems?

A

To alert and update people

37
Q

Preparation- There should be suitable ____ put aside to deal with an emergency

A

Funds

38
Q

Preparation- Residents in high risk areas…

A

Need evacuating

39
Q

Preparation- What should an emergency supply kit contain? Where should it be placed?

A 
Tinned food
Battery radio
Torch
Cash
Breathing mask
IN A CAR
40
Q

Preparation- What should be included in a family emergency plan?

A

How to contact eachother
How to meet
What you will do in an emergency

41
Q

East African Rift Valley

A

African plate
Splitting into Somali and Nubian
Created Kilimanjaro

Geography- Hazards (13 decks)

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