tectonic hazards - natural hazards Flashcards

volcanoes, earthquakes, plates

1
Q

oceanic crust

A

heavy, thin, young, high density

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2
Q

continental crust

A

thick, old, light, low density

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3
Q

convection currents

A

hot, less dense mantle rises & cools, becoming more dense. so sinks to bottom & is heated. causing movements of plates

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4
Q

ridge push

A

at constructive margins ocean ridges form. mantle is hot & rises, pushing crust apart causing rocks to fracture & fault. molten magma pushes through cracks forcing plates to move apart. as new crustal material cools, it becomes denser & slides down, away from the ridge.

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5
Q

slab pull

A

at destructive margins dense oceanic plate sinks into mantle under influence of gravity, which pulls rest of plate along behind.

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6
Q

constructive margin

A

plates move away from each other due to convection currents dragging plates apart. ridge push contributes. upper part of mantle melts & hot magma wells up to surface, forcing plates apart. magma cools forming solid rock this can create new crust/shield volcanoes. movement + fracturing can cause earthquakes.

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7
Q

example of constructive margin

A

Mid-atlantic ridge between North American & Eurasian plates

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8
Q

conservative margin

A

plates move past in each other opp. directions/diff. speeds. friction occurs & plates become stuck. pressure builds. when released sends out energy causing earthquake. no volcanoes.

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9
Q

conservative margin example

A

San Andreas Fault

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10
Q

destructive margin

A

oceanic & continental crust move towards one another. pressure builds leading to fracturing rocks which can cause earthquakes. oceanic is forced beneath continental - subduction. sinking plate melts to form magma. pressure of magma builds & escapes through weaknesses in rock. rises as composite volcano.

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11
Q

destructive margin example

A

Nazca & South American

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12
Q

collision margin

A

2 continental plates are forced together resulting in large fold mountains. same density so crash together making folds in rock strata & some faults. when crust buckles & breaks earthquakes occur.

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13
Q

collision margin example

A

Himalayas, Mt. Everest

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14
Q

crust meaning

A

outer layer of earth

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15
Q

mantle meaning

A

layer of molten rock between core & crust

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16
Q

magma meaning

A

heat from core’s hot enough to melt rock in mantle, molten rock on surface is called lava

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17
Q

sea-floor spreading

A

when 2 oceanic plates pull apart at constructive margin, magma rises & creates new ocean floor

18
Q

rift valleys

A

2 continental plates pull apart, narrow steep sided valley is created

19
Q

shield volcano

A

-constructive margin
-wide base, gentle slopes
-only lava
-regular & calm eruptions
-e.g. Hekla & Surtsey, Iceland

20
Q

composite volcano

A

-destructive margin
-tall cone, narrow base, steep sides
-alternate layers of lava + ash
-irregular, violent explosions
-e.g. Etna & Vesuvius, Italy

21
Q

volcanic primary hazards (5)

A

-lava flows
-volcanic bombs
-gas cloud
-pyroclastic flow
-ash falls

22
Q

volcanic secondary hazard (5)

A

-tsunami
-landslides
-glacier bursts
-lahars
-climate change

23
Q

volcanic immediate effects (4)

A

-ppl killed & injured
-farmland & buildings destroyed
-communications damaged/disrupted
-water, gas, electricity disrupted

24
Q

volcanic long-term effects (5)

A

-spread of disease due to lack of clean water & broken sewers
-hospitals overwhelmed
-lack food, water, shelter & medicine
-loss income & food
-economic impact

25
earthquake meaning
sudden shaking of ground caused by sudden release of pressure creating seismic waves
26
Benefits of Mercalli scale
-more useful for aid -specific about damage cause -cheaper
27
benefits of Richter scale
-objective, accurate -quick results -good for comparison, prediction -universally used
28
4 disadvantages of Mercalli scale
-can be disputed, subjective -takes time/resources -can't be used for comparisons -dangerous?
29
disadvantages of Richter scale
-ignores amount of damage caused -needs equipment -can be hard to understand
30
factors affecting earthquakes (12)
epicentre, focus, population density, building standards, prediction, geology, development, magnitude, timing, prep, location, government
31
epicentre meaning
point on earth's surface vertically above focus
32
focus meaning
origin of earthquake within crust
33
immediate responses of earthquakes (6)
-evacuation -volunteers search for survivors -rescue teams deployed -medical tents set up -money donated to buy supplies -tents given out
34
long-term responses of earthquakes (6)
-building regulations improved -investment focussed on rebuilding -homes rebuilt -ppl move permanently -new jobs in construction -schools/hospitals rebuilt
35
monitoring + preparing for earthquakes (5)
-use radon detection devices measure radon gas in soil & groundwater -sensitive seismometers measure tremors/foreshocks -locations & times mapped to see patterns -unusual animal behaviour -phones have GPS receivers & accelerators that detect ground motion
36
protection for earthquakes + example (3)
-rubber shock absorbers = prevent shaking causing collapse -rolling weights on roof =counteract shockwaves -reinforced lift shafts with tensioned cables = saves any trapped inside -e.g. Transamerica building
37
planning for earthquakes (5)
-fasten down furniture -know how to turn off gas, water, electricity -prepare emergency supplies -create plans for evacuation -educate - earthquake drills
38
monitoring & prediction of volcanoes (4)
-satellites & tiltmeters monitor ground deformation & bulges on v -seismometers measure small earthquakes & tremors -thermal sensors detect temp changes on surface -gas-trapping bottles measure radon & sulfur gases released
39
protection for volcanoes (4)
-difficult bc buildings don't withstand lava, lahars, ash -dig trenches -dump concrete blocks in lava flows (etna) -artificial barriers (hawaii)
40
planning for volcanoes (4)
-risk maps, evacuate -exclusions zones -educating -emergency shelters