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Geography paper 3: hazardous earth > 14.2 Types of volcanic eruption > Flashcards

14.2 Types of volcanic eruption Flashcards

(50 cards)

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1
Q

What is viscosity?

A

An indication of how well a substance flows

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2
Q

What causes volcanic eruptions to produce diverse landforms?

A
  • Where the eruption occurs
  • The type of lava
  • Variety of materials produced eg ash, gases
  • How the eruption takes place
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3
Q

What are the two types of volcanic eruption?

A

Effusive and explosive

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4
Q

Effusive eruptions: where do they occur?

A

Divergent plate boundaries

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5
Q

Effusive eruptions: what type of lava?

A

Basalt

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6
Q

Effusive eruptions: characteristics of the lava?

A

Basic (low % silica), low viscosity, higher temperature at eruption

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7
Q

Effusive eruptions: style of eruption?

A

Gas bubbles expand freely, limited explosive force

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8
Q

Effusive eruptions: materials erupted?

A

Gas, lava flows

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9
Q

Effusive eruptions: frequency?

A

Tend to be more frequent and can continue for many months

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10
Q

Effusive eruptions: shape of volcano?

A

Gently sloping sides, shield volcanoes

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11
Q

Explosive eruptions: where do they occur?

A

Convergent plate boundaries

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12
Q

Explosive eruptions: type of lava?

A

Rhyolite (more acid), andesite (less acid)

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13
Q

Explosive eruptions: characteristics of the lava?

A

Acid (high % silica), high viscosity, lower temperature at eruption

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14
Q

Explosive eruptions: style of eruption?

A

Violent bursting of gas bubbles when magma reaches the surface, highly explosive, vent and top of cone often shattered

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15
Q

Explosive eruptions: materials erupted?

A

Gas, dust, ash, lava bombs, tephra

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16
Q

Explosive eruptions: frequency of eruption?

A

Long periods with no activity

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17
Q

Explosive eruptions: shape of volcano?

A

Steep-sided stratovolcanoes, caldera

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18
Q

What type of eruptions does Iceland owe itself to?

A

Effusive eruptions

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19
Q

Two products of explosive eruptions?

A

Calderas and stratovolcanoes

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20
Q

What are stratovolcanoes?

A

Also known as composite cone volcanoes – made up of layers of ash and acid lava with concave symmetrical profiles – associated with explosive eruptions

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21
Q

What are the complex internal networks of lava called inside a stratovolcano?

Study These Flashcards
A

Sills and dykes

22
Q

What is the difference between a sill and a dyke?

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A 
Sill = horizontal protrusion of magma into surrounding older rocks
Dyke = vertical protrusion of magma into surrounding older rocks
23
Q

What are the vents like in stratovolcanoes + why + what can this lead to?

Study These Flashcards
A

The vents are often filled with a mass of solidified magma because acid magma does not flow easily = build-up of pressure causing explosive eruption

24
Q

What is a caldera?

Study These Flashcards
A

A large-scale volcanic crater formed because of an explosive eruption which emptied the magma chamber causing the volcano sides to subside

25
Example of a caldera:
1883 eruption of Krakatoa in Indonesia left a 7km wide caldera
26
What do convergent plate boundaries and explosive eruptions often give rise to?
Chains of stratovolcanoes eg Indonesia has 130 active stratovolcanoes along its archipelago
27
Two products of effusive eruptions:
Lava plateaux and shield volcanoes
28
How do lava plateaux form?
When basic magma erupts from multiple fissures, vast areas can be covered by free-flowing lava – flood basalts
29
Example of a flood basalt?
Deccan Plateau in central India covers more than 500,000 km2
30
What is a shield volcano?
A volcano with a broad base and gently sloping sides
31
How did the Hawaiian chain of islands form?
Due to the formation of a hotspot, thousands of kilometres from the nearest plate boundary
32
What is a hotspot?
A fixed area of intense volcanic activity where magma from a rising mantle plume reaches the Earth’s surface
33
Two examples of places with a hotspot:
Hawaii and East African Rift Valley
34
Most common type of volcano formed at a hotspot:
Shield volcano
35
Why do volcanoes of Hawaii become extinct?
Over millions of years the pacific plate moves northwest away from the hotspot, so the volcanoes lose their source of magma eg Kauai
36
How quickly does the Pacific plate move over the Hawaiian hotspot?
Moves northwest at a rate of 10cm/year
37
Two examples of active volcanic peaks in Hawaii:
Mauna Loa and Mauna Kea = both reach over 4000m above sea level
38
What Hawaiian volcano is currently rising?
Loihi is directly over the hotspot and is currently 970km below sea level
39
How long is the rift valley running through East Africa?
4000 km long
40
How have active volcanoes been created in East Africa?
As a result of rifting – magma has forced its way to the surface
41
Example of a volcano formed through rifting:
Mount Kilimanjaro
42
What is a super-volcano + what do they exist as?
A volcano that erupts more than 1000km3 of material in a single eruption They exist as giant calderas
43
Example of a super volcano:
The Yellowstone super volcano in Wyoming has a caldera measure 75km in diameter
44
When was the most recent super-volcano eruption?
27,000 years ago – Taupo, North Island, New Zealand
45
When did volcanic activity start in Yellowstone?
2 million years ago – when the giant caldera formed
46
When did Yellowstone last erupt?
70,000 years ago
47
What two key factors need to be considered when measuring and assessing a volcano?
- Magnitude = amount of material erupted | - Intensity = speed at which the material is erupted
48
What scale are volcanoes measured on?
Volcanic Explosivity Index Scale is 0-8 Combines magnitude and intensity
49
What factors are considered when measuring explosivity?
Volume of erupted material, heigh of ejected material, duration
50
What VEI was Eyjafjallajökull in 2010?
VEI of 4

Geography paper 3: hazardous earth (14 decks)

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