L2: Volcanic hazards - The big picture

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How do geological hazards differ from other natural hazards?
The range of scales, nature of occurrence, effect on human activity, critical role on development of life on earth
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What are the different scales of geological hazards? (From smallest to biggest)
Local, landscape, regional, global, catastrophic
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What are the consequences of catastrophic scale hazards?
It changes life completely and causes severe long-term change
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How do geohazard and e.g. storms vary in terms of frequency and magnitude?
Geohazards are much more rare and of higher magnitude than e.g. storms
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How does occurrence and frequency of geohazards influence people?
It influences human activities e.g. the infrastructure we develop
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What can we can and cannot predict about geohazards?
Can generally predict where but not when or magnitude
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Are earthquakes and volcanoes evenly distributed around the world?
No
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What processes does sea-floor spreading produce?
Uplift of continental plates, subduction of plates, creation of oceanic crust
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Describe the inside of the earth
Solid rock which increased in terms of temperature and pressure with depth
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Where does magma form?
In lithosphere at locations where solid rock melts
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How do different subduction types (e.g. oceanic-continental and continental-continental) vary?
They occur at different depths and produce different features
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Is plate movement constant?
No
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What pattern can be seen among islands increasingly further away from hotspots?
They increase with age (volcanic arc)
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How does magma temperature influence movement?
Cooler magma sinks, hotter magma rises
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What happens to parts of plates that break off whilst being subducted?
They remain suspended in earth for millions of years
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How are circular volcanoes formed?
Magma erupts in different directions over millions of years - ends up circular
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How are triangular volcanoes formed?
Magma doming/tripple point formations:The nature of rigid materials means if you apply pressure and heat at one point it will likely split in three directions. Alternatively made by combination of fissure and statavolcano
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What volcanoes are the largest?
Shield - you only see a small part of them, rest underwater
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Describe shield volcanoes
Very large, composed mostly of Pilliow lavas, very unstable (frequent slumping and subsidence)
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Describe stratovolcanoes
Large, classic-shaped volcano, composed of interbedded lava flows and layers of pyroclastic debris
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What does volcano level of danger depend on?
Eruptive style and composition of magma
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What ways does material get erupted?
Lava flow, pyroclastic debris, volcanic gas
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Describe lava flows
Lava flows onto ground surface and cools
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Describe pyroclastic debris
Fragmented material gets thrown out of volcano and lands on ground in solid form
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Describe volcanic gas eruptions
Elements and compounds bubble out of magma or lava as gases
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What does lava viscosity depend on?
Composition (silica content), temperature, content of water and gases
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What volcano type is basalt associated with?
Shield volcanoes
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What shape volcanoes is andesite associated with?
Steep-sided volcanoes
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How does lava with high silica content and low temperatures move and what does it produce?
Moves little, produces steep-sided volcanoes
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Describe the mobility of lava with a low silica content and high temperature
Very runny
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Describe the mobility of lava with high temperatures and high amounts of silica
Has high resistance to flow (thick, sticky)
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Define pahoehoe
Basaltic lava forming smooth or ropy mass
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Describe AA flows
Slow moving, rough, jumble of sharp angular fragments
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What are the most dangerous volcanoes?
Rhyolitic lava domes (and just lava domes in general)
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What do Rhyolitic lava flows produce?
Lava domes and very steep volcanoes
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Other cards in this set

Card 2

Front

What are the different scales of geological hazards? (From smallest to biggest)

Back

Local, landscape, regional, global, catastrophic

Card 3

Front

What are the consequences of catastrophic scale hazards?

Back

Preview of the front of card 3

Card 4

Front

How do geohazard and e.g. storms vary in terms of frequency and magnitude?

Back

Preview of the front of card 4

Card 5

Front

How does occurrence and frequency of geohazards influence people?

Back

Preview of the front of card 5
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