1.3 Hazardous Earth

Question 1

describe the crust

Answer 1

upper layer/surface of the earth; two types: continental, oceanic; solid; continental: 30-50 km thick; oceanic: 6-8km

Question 2

describe the lithosphere

Answer 2

uppermost layer of earth; includes crust (32°C) and very top of mantle (500°C) ; solid - cool and brittle; low density (2.7-3.3 g/cm³)

Question 3

describe the asthenosphere

Answer 3

underneath the lithosphere; partially molten rock, partially solid rock; low-medium density (3.4 - 4.4 g/cm³); 900-1600 °C; lubricating layer

Question 4

describe the lower mantle

Answer 4

solid; 1600-4000 °C; medium density (4.4-5.6 g/cm³)

Question 5

describe the mantle

Answer 5

above outer core and below crust; includes asthenosphere, lower mantle and lower part of the lithosphere; thickness: 2900km (lower mantle: 2200km; upper mantle: 665km)

Question 6

describe the core

Answer 6

below the lower mantle to the centre of earth; includes the inner and outer core; 3500 km thick

Question 7

describe the outer core

Answer 7

liquid; 4000-5000°C; high density (9.9-12.2 g/cm³); 2370 km thick

Question 8

describe the inner core

Answer 8

solid; 1100 km thick

Question 9

describe the continental crust

Answer 9

forms the land; 30-50 km; mostly made igneous rock (granite); low(er) density - 2.7 g/cm³; permanent

Question 10

describe the oceanic crust

Answer 10

under the ocean; 6-8 km; made of igneous rock (basalt); high(er) density - 3.3 g/cm³; created and destroyed

Question 11

where do earthquakes and volcanoes form?

Answer 11

often form together in bands

Question 12

describe what happens at a divergent plate boundary?

Answer 12

two plates move apart; small earthquakes form as plates jolt apart; as two plates move apart, magma rises to fill the gap - causes volcanoes, but as magma easily, eruptions tend to be less violent

Question 13

describe what happens at a conservative plate boundary?

Answer 13

two plates slide sideways relative to each other, either in opposite directions or same directions but at different speeds; movements causes build of friction and pressure until plates slip and large earthquakes are caused; no volcanic eruptions occur

Question 14

describe what happens at a convergent (subduction) plate boundary?

Answer 14

oceanic plate pushes against a continental plate; friction between the plates can result in slippage and large earthquakes; the oceanic plate is subducted below the continental plate as its denser; it moves into the mantle and melts; newly created magma forces through continental plate, causing violent volcanic eruptions

Question 15

describe what happens at a convergent (collision) plate boundary?

Answer 15

two continental plates move towards each other; this causes material between them to buckle, fold and be forced upwards to create mountains ranges; the plates colliding causes large earthquakes; no volcanic eruptions

Question 16

what are the characteristics of hotspots?

Answer 16

when volcanoes form away from plate boundaries; a plume of superheated rock rises v slowly through the mantle; once it reaches the upper mantle, it causes the asthenosphere and lithosphere to melt; magma produced then rises through weakness in the crust

Question 17

how do tectonic plates move?

Answer 17

heat due to radioactive decay creating geothermal heat rises from the core and convection currents are created in the outer core and mantles; these vast mantle convection currents are strong enough to move the plates

Question 18

describe the characteristics of shield volcanoes

Answer 18

occur at hotspots and divergent plate boundaries; has basaltic magma - low viscosity; very large, gently sloping shapes; very low silica and low gas content; made of basalt; very wide layers of lava only; relatively low explosivity

Question 19

describe the characteristics of composite volcanoes

Answer 19

occur at convergent (subduction) plate boundaries; has andesitic magma - high viscosity; steep-sided shapes; distinctive layers of ash and lava; more silica and dissolved gases; conical shape; large and high explosivity

Question 20

why are composite volcanoes more explosive than shield volcanoes?

Answer 20

andesitic magma = more silica, so more viscous and more likely to explode when reaches the surface as more difficult for gas to escape; vent also often becomes blocked w solidified lava after eruption so more pressure builds up until next explosion

Question 21

why do shield volcanoes have sloping sides?

Answer 21

fluid magma causes frequent eruptions, can flow long distances before cooling, and are under less pressure

Question 22

why do composite volcanoes have steep sides?

Answer 22

material is blown out of the top bc of viscous magma, it is also under high pressure, and there are layers due to lava cooling quickly and ash from eruption settling after

Question 23

where do the highest magnitude earthquakes happen? why?

Answer 23

convergent (subduction) boundaries; more pressure and friction

Question 24

how do tsunamis form?

Answer 24

oceanic plate moves towards continental plate, friction stresses and bends c. plate downwards; plates slip and o. plate is subducted, massive amounts of energy is released and c. plate rebounds up; energy displaces water at surface, raising it about normal sea level; gravity pulls it back down, energy ripples out horizontally; when far from shore, tsunami is small as it moves through entire depth of water; closer to shore, there is less water to move through so energy is compressed, wave speed decreases and wave height increases, aka wave shoaling

Question 25

what factors impact the effects of earthquakes?

Answer 25

magnitude; depth of focus; secondary hazards; wealth/economic development; pop. density; time of day/week/year; accessibility

Question 26

what were the impacts of the nepal earthquake in 2015?

Answer 26

death toll 8,500+; no. injured: 2200; no. of homes destroyed: 160000; no. of homeless: 3.5m; no. of people affected: 8m; costs: $10 billion; 160000 buildings destroyed, 500000 damaged; magnitude of 7.8M

Question 27

what were the primary impacts of the nepal earthquake?

Answer 27

destruction in the Kathmandu valley: roads blocked; homes and buildings destroyed; ancient monuments e.g. Durbar Square, collapsed - social and cultural roots of country affected; water pipes burst - polluted water

Question 28

what were the primary impacts of the nepal earthquake?

Answer 28

avalanche: destruction in Langtang caused by collapse of ice ridge; caused 19 deaths; over 200 people trapped on Mt Everest; base camp destroyed; numerous injuries; glaciers changed
landslides: caused by earthquake shaking; half a mile of hill side hit the valley; countless buildings flattened - all houses and 55 small hotels; 1000+ death toll - everyone died; village buried

Question 29

what was the immediate response and relief efforts to the nepal earthquake?

Answer 29

all climbers were rescued by helicopters; temporary camps were made for the homeless; there was international aid relief - search and rescue, medical; stabilisation of buildings; army and volunteers helping

Question 30

what was the long term response and relief efforts to the nepal earthquake?

Answer 30

rebuilding of homes and transport infrastructure; restoration of ancient monuments; international aid donations - UK £50m from gov., £33m from public donation

Question 31

what were the key impacts of the japan earthquake in 2011?

Answer 31

15891 confirmed deaths; 2562 no. of people missing; 127300 buildings completely destroyed; 1m partially destroyed; $300b costs; magnitude of 9.0M

Question 32

what were the primary impacts of the japan earthquake in 2011?

Answer 32

all railway services in tokyo were suspended - 20000 people left stranded at major stations; some buildings destroyed; around 700 people killed (5% of total)

Question 33

what were the secondary impacts of the japan earthquake in 2011?

Answer 33

tsunami damage: heights of up to 39m, travelling inland as far as 10km in Sendai; flooded 560 sq km in Japan; first hit less than one hour after first quake; destroyed protective tsunami seawalls; killed 90% of total people killed; flooded Sendai Airport and damaged major ports; 4.4m houses left wo electricity and 1.5 wo water; 340000 people displaced in the Tohoku region
radiation threat: cooling system failures; 300 tons of radioactive water continues to leak into pacific ocean every day; traces of radioactive materials found along north american coast

Question 34

what was the immediate response and relief efforts to the japan earthquake?

Answer 34

planning, prediction and prep: sea walls - but not for such large magnitude; minute warning before shaking hit city; stringent seismic building codes and early warning system stopped deaths by stopping high speed trains and factory assembly lines; texts and tsunami one min warning allowed evacuation
international aid; temporary accommodation structures for homeless; over 50% of people managed to head for higher ground; japan’s self-defence force assisted in search, rescue and recovery

Question 35

what was the long term response and relief efforts to the japan earthquake?

Answer 35

newly installed, upgraded tsunami warning system; earthquake engineers examined damage to find ways to build buildings more resistant to quakes and tsunamis; about 250000 still in temporary housing 4 years later; stricter seismic safety standards for nuclear power stations

Question 36

how can social media be used to access earthquake impact?

Answer 36

can be used to locate people and areas to identify which geolocations need aid

Question 37

why are impacts of earthquakes different?

Answer 37

bc of: quake magnitude; scale of secondary hazards; relief (shape of land); quality of response and planning; wealth; building quality and prep; pop. density

Question 38

how does japan plan for earthquakes?

Answer 38

quake drills are held every year to educate people on how to respond; emergency services are trained in quake search and rescue in order to minimise casualties; people keep emergency kits at home cont. water, food, a torch, a radio, to ensure survival and receive safety advice after quake

Question 39

how does japan prep for earthquakes (building features)?

Answer 39

shock absorbers built into cross braces; cross bracing stops floors collapsing; damper in roof reduces sway; strong, flexible steel frame stops cracking; very deep foundations to prevent collapse; strong double glazed windows stop broken glass shattering down

Question 40

how does nepal prep for earthquakes (building features)?

Answer 40

concrete rings ties walls to foundations; cross-braced wood/bamboo frame; lightweight thatched roof; walls made of mud and straw packed between wooden slats; simple steel rod foundations; overall does little to protect, but it’s low cost