Tectonic Hazards

List the primary hazards of earthquakes.
Crustal fracturing, ground shaking
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What is crustal fracturing?
When the pressure of tectonic strain exceeds the breaking stress of the rock and so the crust breaks.
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What is ground shaking?
The large amounts of energy released in an earthquake are radiated away through waves which causes shaking of the crust.
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List the secondary hazards of earthquakes.
Liquefaction, landslides
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What is liquefaction?
When water saturated material loses its strength and acts as a liquid under intense shaking.
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What are landslides?
Rocks on slopes which are loosened by shaking and fall, generally during higher magnitude earthquakes.
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What are P waves?
Primary waves caused by compression which move at 8km/s and move through liquids.
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What are S waves?
Secondary waves which have a lower speed of 4km/s. They cannot move through liquids but have a higher amplitude and so are more destructive than P waves.
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What are L waves?
Love waves are surface waves that have an high amplitude (so are dangerous) and vibrate in the horizontal plane.
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List the primary hazards of volcanic eruptions.
Lava flows, pyroclastic flows, ash falls, gas eruptions
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Why are lava flows a hazard?
Lava can flow very quickly, which makes it dangerous. On steep slopes it can move up to 15m/s. The viscosity (and so the speed) is determined by the amount of silicon dioxide it contains.
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Why are pyroclastic flows a hazard?
Pyroclastic flows result from the frothing of molten material at the vent. The bubbles burst and eject hot gases. The clouds can be 1000°C and move very quickly and so this is the most dangerous primary hazard.
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Why are ash falls a hazard?
Tephra is volcanic rock and ash that is ejected during an eruption, large rocks can cause injury or deaths. Ash is fine tephra which can travel further. It clogs engines and reduces visibility.
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Why are gas eruptions a hazard?
Water vapour, sulphur dioxide, hydrogen and carbon dioxide are emitted from volcanoes and are spread around the atmosphere by high level winds. Carbon dioxide (poisonous) is colour and odour less and can accumulate in valleys without notice.
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List the secondary hazards of volcanic eruptions.
Lahars, jokulhlaups
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Why are lahars a hazard?
Heavy rainfall combined with fine sane and silt (tephra) combine to form lahars, volcanic mudflows, which can detroy buildings and fill rivers. The severity depends on slope, volume and size of particles.
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Why are jokulhlaups a hazard?
They release massive amounts of melt water in a glacial outburst flood following a breach in the ice or moraine dam.
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Other cards in this set

Card 2


What is crustal fracturing?


When the pressure of tectonic strain exceeds the breaking stress of the rock and so the crust breaks.

Card 3


What is ground shaking?


Preview of the front of card 3

Card 4


List the secondary hazards of earthquakes.


Preview of the front of card 4

Card 5


What is liquefaction?


Preview of the front of card 5
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