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Geography Form 2 Term 3 > Hazards - Volcanoes > Flashcards

Hazards - Volcanoes Flashcards

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1
Q

At what 4 places is volcanic activity found?

A

Oceanic ridges
Rift Valleys
Subduction Zones
Hot spots

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2
Q

How are the 2 different types of volcano?

A

Shield

Composite

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3
Q

What are shield volcanoes?

A

Big volcanoes made from layers of solidified balsatic lava with gently sloping sides

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4
Q

What are composite volcanoes?

A

Smaller volcanoes made of alternating layers of andesitic lava and ash with steep slopes above 10 degrees

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5
Q

What types of volcanoes form at destructive boundaries?

A

Composite

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6
Q

Where do shield volcanoes form?

A

At constructive boundaries or hot spots

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7
Q

What kind of eruptions do composite volcanoes do?

A

Explosive

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8
Q

What kind of eruptions do shield volcanoes do?

A

Effusive

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9
Q

What is a volcano?

A

An opening in the crust of the Earth connected underground to a magma chamber from which molten lava, gases, steam and pyroclastic material are ejected.

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10
Q

What impacts the shape and form and type of eruption of a volcano?

A

Its lava

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11
Q

What is the difference between effusive and explosive eruptions?

A

Explosive is arbourne

Effusive is landbound

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12
Q

What is tephra?

A

Explosive material under 64mm

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13
Q

What is a volcanic bomb?

A

Explosive material over 64mm

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14
Q

What is the Benioff zone?

A

Part of the subduction zone where oceanic plate melt into magma

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15
Q

How do volcanoes form in rift valleys?

A

The crust in rift valleys is much thinner than in neighbouring areas. Magma forces its way to the surface through the thinning crust

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16
Q

What are hot spots?

A

Small areas of the Earth’s crust where an unusually high heat flow leads to volcanic activity

17
Q

How do volcanoes form over hot spots?

A

Column of upwelling magma melts the overlying crust and molten magma is forced through the crust. The plate moves over the hotspot, forming a succession of volcanoes.

18
Q

How can volcanoes that are not directly above hot spots still erupt?

A

As the plate moves it drags the head of the magma plume with it

19
Q

What is the main method of measuring the magnitude of volcanic eruptions?

A

Volcanic explosivity index

20
Q

What percentage of volcanoes lie on plate margins?

A

95%

21
Q

What are active volcanoes?

A

Volcanoes that have erupted in the last 2,000 years

22
Q

What are dormant volcanoes?

A

Volcanoes that haven’t erupted in the last 10,000 years

23
Q

What are extinct volcanoes?

A

Volcanoes that aren’t going to erupt again

24
Q

What percentage of the Earth’s surface is made of silica?

A

95%

25
Q

What are the primary hazards of volcanoes?

A 
Tephra
Pyroclastic flows
Nuee ardentes
Lava flows
Volcanic gases
26
Q

What are the secondary hazards of volcanoes?

A 
Lahars
Acid rain
Flooding
TSunamis
Volcanic landslides
Climate change
27
Q

What are pyroclastic flows?

A

Very hot gas charged high velocity flows made up of a mixture of gas and tephra that flow down the sides of the volcano

28
Q

What are lahars?

A

Mud flows formed by the combination of melted snow and ice and volcanic gases, which quickly move down the course of river valleys

29
Q

How do volcanic eruptions cause flooding?

A

Eruptions melt glacier and ice caps

30
Q

How do volcanic eruptions cause acid rain?

A

Eruptions emit sulphur dioxide which combines with atmospheric moisture to form acid rain

31
Q

What type of lava do shield volcanoes have?

A

Basic, non-viscous

32
Q

What type of lava do composite volcanoes have?

A

Acidic, viscous

33
Q

Are shield or composite volcanoes hotter?

A

Shield

34
Q

What percentage of silica is basic lava?

A

45%

35
Q

What percentage of silica is acidic lava?

A

66%

Geography Form 2 Term 3 (21 decks)

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