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Physical Geography > Vulcanicity- Content > Flashcards

Vulcanicity- Content Flashcards

1
Q

What is an example of flooding resulting from lava flows?

A

Spirit Lake rose 80m after the eruption of Mount St Helen’s

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2
Q

What are the benefits of volcanoes?

A
  • hot rocks allow the development of geothermal power
  • lava flows create new land
  • igneous rocks make good building materials
  • lava and ashes= fertile soils
  • tourist attractions e.g. geysers and hot springs
  • extinct = defensive sites
  • volcanic sulphur= pharmaceutical manufacturing processes
  • valuable mineral deposits
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3
Q

Example of geothermal power

A

Iceland

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4
Q

Example of extinct volcano as a defensive site

A

Edinburgh Castle

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5
Q

Example of valuable mineral deposits

A

Gold silver and diamonds in Java

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6
Q

What is the type of magma at constructive?

A

Basaltic magma

Above 1000 degrees C

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7
Q

What is the type of magma at destructive?

A

Andesitic/rhyolithic

Up to 1000 degrees C

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8
Q

What are the characteristics of magma at constructive?

A
  • low in silica
  • thin and runny (less viscous)
  • gas can escape
  • hotter
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9
Q

What are the characteristics of lava at destructive

A
  • high in silica
  • viscous and thick
  • traps gas
  • cooler
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10
Q

What is the type of eruption at constructive?

A

Low on VEI scale e.g. Hawaiian

not very explosive as gases are able to escape, lava

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11
Q

What is the type of eruption at destructive?

A

High on VEI e.g. Vulcanian, Plinian

can be extremely explosive with ash, dust and lava

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12
Q

What is the eruption height at constructive?

A

2km and less

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13
Q

What is the eruption height at destructive?

A

55km and below, can be way over 20km

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14
Q

What are the materials produced at constructive?

A

mainly lava

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15
Q

What are the materials erupted at destructive?

A
  • pyroclastic material
  • ash and dust
  • lava bombs
  • tephra
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16
Q

What is the frequency at constructive

A

Eruptions are regular but can be continuous

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17
Q

What is the frequency at destructive?

A

less frequent, often have long dormant periods

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18
Q

What is the form of volcano at constructive?

A
  • basic shield volcano or lava plateau

- made of only lava

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19
Q

What is the form of volcano at destructive?

A
  • composite cone or acid lava dome
  • layers of ash and lava
  • very viscous lava
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20
Q

What are the hazards of volcanoes?

A
  • ash falls ruin crops/machinery, disrupts transport, breathing
  • lava flows burn and bury crops
  • dust emissions create rainstorms; dangerous lahars
  • dust absorbs solar energy and lowers atmospheric temps
  • pyroclastic flows; life and property
  • flooding results from lava flows/debris blocking rivers
  • submarine eruptions= tsunamis
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21
Q

What are the two types of volcanic landforms?

A
  1. Extrusive igneous rock formation (volcano)

2. Intrusive igneous rock formation (not a volcano)

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22
Q

What happens to intrusive rock forms?

A
  • lava cools quickly when in contact with air
  • this creates crystals so rock is finer grained
  • e.g. basalt
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23
Q

What are the solid material coming from volcanoes?

A
  • dust
  • glassy cinders
  • ash
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24
Q

What are the gases released by volcanoes?

A
  • chlorine
  • carbon monoxide
  • hydrogen sulphide
  • sulphur dioxide
25
Q

What are the liquids released by a volcano?

A
  • surface lavas e.g. acid, basic
  • lava bombs e.g. tephra or pyroclasts; solidify in mid air e.g. Forming pumice, fine hairlike trails of magma called lapili
26
Q

What are the three types of lava?

A
  1. Basic lava
  2. Andesitic (intermediate) lava
  3. Rhyolithic lava (acidic) lava
27
Q

Characteristics of basic lava

A
  • upward movement of mantle material at constructive margins
  • along spreading ridges and hot spots
  • low in silica, mostly fluid lava which allows gas bubbles to expand and pop so it isn’t explosive
28
Q

Characteristics of andesitic lava

A
  • destructive plate margins
  • high in silica; very viscous (acidic)
  • often solidifies before reaching surface; build of pressure creates violent eruptions
  • gas can’t escape so eruptions are explosive
29
Q

Characteristics of rhyolithic

A
  • destructive and collision

- same characteristics as andesitic

30
Q

Why do intrusive volcanic landforms form?

A
  • magma intrudes into the crust and solidifies
  • can be exposed at the surface later due to lateral erosion
  • magma in the intrusive landforms crystallises and solidifies at plutonic depths
  • forms large crystals creating rocks e.g. granite, dolerite
  • more resistant than extrusive such as basalt because the cooling process is longer and the crystals have taken more time to grow
31
Q

Characteristics of batholiths

A
  • dome shaped, exposed by later erosion
  • several hundreds of km in diameter
  • when batholiths are exposed by weathering and erosion creates weathered pieces of rock e,g. Granite in hill areas called tors
32
Q

How are batholiths formed?

A
  • formed deep below the surface where large masses of magma cool and solidify
  • large crystals e.g. Granite form in the rock
  • the batholith can be altered by heat and pressure to form a metamorphic aureole e.g. limestone can be altered to marble
33
Q

What are characteristics of dykes?

A
  • ridges which can be eroded to form depressions
  • can be a few metres long to many kms long
  • can be a few centimetres to many metres wide
  • often occur in groups called dyke swarms
34
Q

How are dykes formed?

A
  • vertical intrusions of magma form by magma cooling with horizontal cooling cracks
  • the magma cuts across the bedding planes of rocks
  • erosion of surrounding less resistant rock can leave dykes exposed as ridges
35
Q

What are the characteristics of sills?

A
  • run along bedding planes
36
Q

How are sills formed?

A
  • magma cools along the lines of bedding planes as horizontal intrusions
  • vertical cooling cracks form along these intrusions
37
Q

Examples of dykes

A

On the Isle of Arran (Scotland), there are dyke swarms with 500 dykes across 20km that jut out from the East coast, made of quite basaltic rock. They form a wall like feature across the coast.

38
Q

What are are examples of sills?

A

The Great Whin Sill is an upstanding cliff like feature that forms cliffs, including the cliffs beneath Banburgh Castle in Northumberland. It cuts across the North of the country into the North Sea, and across the River Tease forming High Force waterfall. Hadrian’s Wall is built along it.

39
Q

What are examples of batholiths

A

In Bodmin Moor and Dartmoor, weathered batholiths form outcrops at the top of hills called tors that are exposed because of erosion.

40
Q

Describe a geyser q

A
  • intermittent forceful discharges of superheated water

- short lived features as ground water conditions may change and new geysers appear elsewhere

41
Q

How is a geyser formed?

A
  • rocks with fractures fill up with groundwater
  • magma chambers in the igneous rock heat the cold water
  • the water is pushed through a vent towards the surface
  • the water expands through build of pressure, and eventually forcefully escapes as steam and hot water
42
Q

Place examples of geysers

A

Old Faithful, Yellowstone National Park

Stokkur, Iceland (the name geyser originates from Iceland)

43
Q

How can geysers be of use to humans?

A

Geothermal energy, tourism

44
Q

Are geysers a hazard?

A

Yes because they are very hot and so can be dangerous

45
Q

Description of a fumerole

A
  • widespread low pressure outlets of steam and CO2 (can also be carbon monoxide and sulphur)
  • associated with active and dormant volcanoes
  • persist for thousands of years after a volcano has become extinct
  • called solfataras when sulphur
46
Q

How are fumeroles formed

A
  • superheated water turns to steam as it condenses on the surface
47
Q

Place examples for fumeroles

A
  • Mount Redoubt in Alaska
  • in April 2006 a fumerole killed three ski patrol workers in California
  • there are over 4000 fumeroles around Yellowstone
48
Q

Describe a hot spring and boiling mud

A
  • areas of superheated water at the surface which are not explosive
  • some are acidic and some alkali
  • can be radioactive if they have absorbed radon gas
  • can bubble queitly or erupt like a geyser
49
Q

Formation of hot springs and boiling mud

A
  • magma chambers heat water below the surface as it passes through igneous rocks
  • the superheated water is not being forced through a vent so does not explode at the surface like a geyser
  • if the water mixes with mud and minerals near the surface it forms boiling mud or possibly a mud volcano
50
Q

Place examples of hot springs/boiling mud

A
  • common in Iceland e.g. The Blue Lagoon

- Mammoth Hot Springs, USA

51
Q

In what ways can volcanoes be categorised?

A
  • form/shape
  • frequency of eruption
  • nature of opening
  • violence of eruption
52
Q

What are the different frequencies of eruption and examples?

A
  1. Dormant (erupted within historical record) e.g. Mt Rainier
  2. Extinct (haven’t erupted in 25,000 years) e.g. Edinburgh Castle
  3. Active (erupted in living memory) e.g. Stromboli/Mt Etna
53
Q

How many active volcanoes are there around the world?

A

1500

54
Q

What are the two natures of opening and examples?

A
  1. Vent e.g. Shield and cone volcanoes
  2. Fissure e.g. Mid Atlantic Ridge, African Rift Valley, Giant’s Causeway in Northern Ireland (columnar basalt forms a plateau)
55
Q

What are the different forms/shapes and examples?

A
  1. Basic shield e.g. Mauna Loa in Hawaii (largest volcano in world)
  2. Composite cone e.g. Mt Etna and Vesuvius in Italy
  3. Acid/dome volcanoes e.g. Puy region of Central France
  4. Calderas e.g. Krakatoa in Indonesia
  5. Ash and cinder cones e.g. Paricutin in Mexico
56
Q

What are the different types of vulcanicity human response?

A

Modify the loss, modify the vulnerability and modify the event

57
Q

What does modify the loss entail?

A
  • emergency services

- international aid

58
Q

What does modify the event entail?

A
  • environmental control e.g. water sprays, diversion techniques
59
Q

what does modify the vulnerability entail?

A
  • hazard resistant design e.g. Strengthen building roofs
  • community preparedness e.g. evacuation
  • prediction and warning

Physical Geography (12 decks)

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