tectonic hazards - natural hazards

Question 1

oceanic crust

Answer 1

heavy, thin, young, high density

Question 2

continental crust

Answer 2

thick, old, light, low density

Question 3

convection currents

Answer 3

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

Question 4

ridge push

Answer 4

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.

Question 5

slab pull

Answer 5

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

Question 6

constructive margin

Answer 6

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.

Question 7

example of constructive margin

Answer 7

Mid-atlantic ridge between North American & Eurasian plates

Question 8

conservative margin

Answer 8

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.

Question 9

conservative margin example

Answer 9

San Andreas Fault

Question 10

destructive margin

Answer 10

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.

Question 11

destructive margin example

Answer 11

Nazca & South American

Question 12

collision margin

Answer 12

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.

Question 13

collision margin example

Answer 13

Himalayas, Mt. Everest

Question 14

crust meaning

Answer 14

outer layer of earth

Question 15

mantle meaning

Answer 15

layer of molten rock between core & crust

Question 16

magma meaning

Answer 16

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

Question 17

sea-floor spreading

Answer 17

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

Question 18

rift valleys

Answer 18

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

Question 19

shield volcano

Answer 19

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

Question 20

composite volcano

Answer 20

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

Question 21

volcanic primary hazards (5)

Answer 21

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

Question 22

volcanic secondary hazard (5)

Answer 22

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

Question 23

volcanic immediate effects (4)

Answer 23

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

Question 24

volcanic long-term effects

Answer 24

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

Question 25

earthquake meaning

Answer 25

sudden shaking of ground caused by sudden release of pressure creating seismic waves

Question 26

Benefits of Mercalli scale

Answer 26

-more useful for aid
-specific about damage cause
-cheaper

Question 27

benefits of Richter scale

Answer 27

-objective, accurate
-quick results
-good for comparison, prediction
-universally used

Question 28

4 disadvantages of Mercalli scale

Answer 28

-can be disputed, subjective
-takes time/resources
-can’t be used for comparisons
-dangerous?

Question 29

disadvantages of Richter scale

Answer 29

-ignores amount of damage caused
-needs equipment
-can be hard to understand

Question 30

factors affecting earthquakes (12)

Answer 30

epicentre, focus, population density, building standards, prediction, geology, development, magnitude, timing, prep, location, government

Question 31

epicentre meaning

Answer 31

point on earth’s surface vertically above focus

Question 32

focus meaning

Answer 32

origin of earthquake within crust

Question 33

immediate responses of earthquakes (6)

Answer 33

-evacuation
-volunteers search for survivors
-rescue teams deployed
-medical tents set up
-money donated to buy supplies
-tents given out

Question 34

long-term responses of earthquakes (6)

Answer 34

-building regulations improved
-investment focussed on rebuilding
-homes rebuilt
-ppl move permanently
-new jobs in construction
-schools/hospitals rebuilt

Question 35

monitoring + preparing for earthquakes (5)

Answer 35

-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

Question 36

protection for earthquakes + example
(3)

Answer 36

-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

Question 37

planning for earthquakes
(5)

Answer 37

-fasten down furniture
-know how to turn off gas, water, electricity
-prepare emergency supplies
-create plans for evacuation
-educate - earthquake drills

Question 38

monitoring & prediction of volcanoes (4)

Answer 38

-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

Question 39

protection for volcanoes (4)

Answer 39

-difficult bc buildings don’t withstand lava, lahars, ash
-dig trenches
-dump concrete blocks in lava flows (etna)
-artificial barriers (hawaii)

Question 40

planning for volcanoes (4)

Answer 40

-risk maps, evacuate
-exclusions zones
-educating
-emergency shelters