Tectonics

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What is a tectonic hazard?
a perceived natural event formed by tectonic processes, with the potential to threaten both life and property.
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Name three features formed by tectonic processes.
Ocean trench, fold mountains, rift valley, plateau, hot spot volcano, mid-ocean ridge
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What is the benioff zone?
The zone where many deep earthquakes occur, at convergent destructive boundaries when an oceanic plate is subducted, caused by slab pull
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What is a batholith?
Where viscous lava cannot break through the crust.
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How and where are fold mountains formed?
At convergent collision boundaries, where sediments trapped between the two plates are pushed upwards into jagged, steep mountains.
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How do intra-plate earthquakes occur?
Collisions fracture crust away from boundaries too, earthquakes nearer the middle of plates are associated with ancient faults, e.g. Rhine Rift Valley
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What are the main differences between oceanic and continental plates?
Oceanic are denser, thinner, younger and composed of basaltic rock. Continental are less dense, thicker, older and made of granite rock.
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How do hot spot volcanoes form?
Volcanic activity near the centre of plates where a hot plume rises, breaks the crust, cools and forms a shield volcano, as the plate moves the volcano moves too but the hot plume does not so another hot spot volcano will form over the plume.
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What occurs at a mid-ocean ridge?
At divergent boundaries a gap forms where magma rises from the mantle, it cools into rock forming new land, can create fissure eruptions when lava erupts through gap.
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Describe the features of a convergent destructive plate boundary.
Where oceanic and oceanic or oceanic and continental plates collide, causes deep, high magnitude earthquakes, explosive eruptions, ocean trenches, fold mountains, volcanic islands and benioff zones.
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Describe the features of a convergent collision plate boundary.
Where two continental plates collide, creates shallow-medium depth, moderate magnitude earthquakes, little volcanic activity, creates fold mountains and plateaus.
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Describe the features of a divergent plate boundary.
Where two plates move away from each other, creates shallow, low magnitude earthquakes, effusive volcanic eruptions, ocean ridges and rift valleys
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Describe the features of a transform plate boundary.
When two plates move side by side/ parallel, creates shallow, moderate earthquakes, usually no volcanoes, creates ridges, scars.
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List the layers of the Earth.
Inner core, outer core, mesosphere, asthenosphere, lithosphere
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How are earthquakes caused?
Friction created by masses of rock trying to move past each other, sending seismic waves from the focus in all directions.
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What are p-waves and s-waves?
A p-wave arrives first, is longitudinal, can travel through solid and liquid and least damaging. A s-wave arrives second, is transverse, can only travel through solids and is more destructive.
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What are Rayleigh waves and love waves?
A Rayleigh wave has a rolling motion, travels on the Earth's surface and is very damaging. A love wave arrives last and moves side to side as it goes forwards, on the Earth's surface, most damaging.
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What secondary hazards can earthquakes cause?
Liquefaction, tsunamis, landslides
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What is liquefaction?
Water-saturated sediment loses strength and acts fluid, can cause building damage, destroy infrastructure and wash things away e.g. in Christchurch 2011
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What are landslides?
Earthquake loosens rock and material on steep slopes, which moves downwards due to gravity, may hit settlements, block roads and infrastructure e.g. Kashmir 2005 killed 87,300
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What are tsunamis?
Sequences of waves with deep troughs between them, more noticeable in shallow water due to shorter wave length, created by water column displacement due to a plate thrusting upwards/downwards, volcanic eruptions or landslides.
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What factors impact how destructive a tsunami may be?
Distance waves travel, shoreline gradient, coastal orientation, lowlands, land uses, ecosystem buffer, timing, warnings, population density...
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What are the three types of lava?
Basaltic: hottest, least viscous, low silica, from effusive eruptions. Andesitic: medium heat and viscosity, from pelean eruptions. Rhyolitic: coolest, most viscous, high silica, from plinian/vesuvian eruptions
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What are the three types of eruption?
Effusive: non-explosive, lava wells up and overflows, basaltic, e.g. Hawaii. Pelean: explosive, dome collapses, results in lots of tephra and a fast pyroclastic flow, andesitic. Plinian/Vesuvian: reach 2-45km high, long duration, rhyolitic lava.
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What secondary hazards can volcanoes cause?
Gas, tephra, pyroclastic flows, lahars, jokulhlaups
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What is a pyroclastic flow?
Dense mix of super-heated tephra and gas, moves fast (up to 700km/h), explosive eruptions, destroys all in path e.g. Montserrat 1997
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What is a Jokulhlaup?
Flood of melt-water from underneath an ice cap/glacier when a volcano erupts underneath, deposits material in lowlands, very fast and powerful e.g. EFJ eruption 2010
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What is lahar?
Water mixed with tephra, high speed, huge volume, can travel very far, bury towns, e.g. Amero 1985
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What is volcanic gas?
Water vapour which can cause heavy rainfall or sulphur dioxide which can cool Earth or cause acid rain.
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What is tephra?
Solid and molten rock, debris, ash can cause roof collapse, prevent flights, cause breathing problems and destroy machinery.
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Describe the convection current explanation for tectonic movement?
Created in the mantle as heat radiates outwards from inner core, hot material rises, spreads out below the crust, then sinks and cools.
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Describe the paleomagnetism explanation for tectonic movement?
Four times every million years Earth's magnetic field reverses, magma rises in mid-ocean ridges, magma cools into new crust which contains iron and so the magnetic direction can be identified, a alternate pattern of magnetism can be seen.
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Describe ridge push and slab pull.
Ridge push is where magma rises and convection current pull plates apart. Slab pull is the gravitational pull of the lithosphere as it is subducted at convergent destructive boundaries as the oceanic plate sinks under the continental plate.
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Describe any other explanations for tectonic movement?
Plates fit together, matching rock types, matching fossils, coal found in tropics, glaciation in Africa, hazards occur at boundaries.
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What is a tectonic disaster?
A hazard which causes a significant impact on a vulnerable population.
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What is a mega-disaster?
Large scale, serious problems, 2000+ dead/ 200,000 homeless/ 5% fall in GDP/ international aid for 1+ year.
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What are the three ways of measuring earthquakes?
Moment Magnitude: measures energy released. Richter Scale: uses arrival time of P and S waves, amplitude of S waves and distance from epicentre. Mercalli Scale: looks at effects on Earth's surface e.g. level of destruction (1-12)
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What scale is used to measure the intensity of volcanic eruptions?
Volcanic Explosivity Index: 0-8, each step is 10x greater.
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Other cards in this set

Card 2

Front

Name three features formed by tectonic processes.

Back

Ocean trench, fold mountains, rift valley, plateau, hot spot volcano, mid-ocean ridge

Card 3

Front

What is the benioff zone?

Back

Preview of the front of card 3

Card 4

Front

What is a batholith?

Back

Preview of the front of card 4

Card 5

Front

How and where are fold mountains formed?

Back

Preview of the front of card 5
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