Tectonics AS Geography WJEC

lab =

buffer zone between layers of crust

order from out to in of layers

lithosphere asthenosphere mantle outer core inner core

continental crust

old light thick doesn’t sink permanent e.g. granite

oceanic crust

young thin dense sinks renewable e.g. basalt

who created theory of pangea

alfred weneger

ocean trenches form due to

suction currents

hotspots are

openings in the crust where a mantle plume can rise leading to eruptions and causing islands to form

why are there gaps between hotspot islands

activity is not constant

convergent boundaries have

powerful subduction volcanoes

example for subduction zones

peru-chile trench up to 8000m deep

divergent boundaries have

rift volcanoes

continental divergent boundaries example

kilimanjaro where crust has thinned

example of conservative boundaries

san andreas fault california

conservative boundaries have

shallow earthquakes

fault scarps

vertical displacement

quasi-natural earthquakes are

generated by human activity

example of quasi natural earthquakes

1993 killari india caused by weight of water in new reservior

fissure volcanoes

lava ejected through linear fissures, constructive margins, eg 1973 eldfell iceland 2km long

shield volcanoes

basaltic low viscosity lava spreads, gentle sloping sides, oceanic diverging and hotspots, eg mauna loa hawaii

acid / dome volcanoes

lava quickly solidifies, steep sided and convex, rhyolitic magma forms spine, parasitic cones, eg mt pelee martinique

composite / strato volcanoes

alternating layers of lava and ash, converging plate margins, acidic lava flows slowly, explosive, eg mt etna vesuvius

caldera volcanoes

explosions remove summit or cauldron subsidence, craters flooded forming new cones in centre, eg yellowstone

ash and cinder cones

ash and cinders build up, highly permeable, occur in volcanic fields

primary hazards of volcanoes

pyroclastic flows, lava flows, airfall tephra, volcanic gases

pyroclastic flows

hot gases fragments and ash, up to 1000 degrees, eg cloud hit st pierre martinique 1902 killed 30,000

lava flows

up to 50 km/h, eg kilauea eruptions spread over 78km squared

airfall tephra

lava bombs, ash causes poisoned land, health issues, lahars, engines, and krakatoa caused global cooling for 1-2 years

volcanic gases

water vapour, hydrogen, carbon dioxide and monoxide, eg merapi released co2 140 dead

secondary volcanic hazards

lahars, landslides, jökulhaups

lahars

torrential rain from storms combines with melting snow and ice, eg nevado del ruiz 1985 killed 23,000

landslides

triggered by heavy rainfall, earthquakes and explosions, magma rising can cause excess sloping, eg mt st helens

jökulhaups

melted ice under glacier bursts and floods, eg grimsvotn 1996 caused $14m damage

scales for earthquakes

mercalli scale based on damage, richter scale based on amplitude, mm scale logarithmic moment magnitude scale

effusive category of volcano

icelandic

explosive category of volcano

plinian

VEI =

volcanic explosivity index

p-waves

longitudinal, travel through solid rock and oceans, fast

s-waves

transverse, slower, travel only through solids, destructive to surface

factors that affect severity

depth of focus, strength of shock, time of day, duration, predictability, development

primary hazards of earthquakes

shaking severs pipelines, buildings collapse

secondary hazards of earthquakes

liquefaction eg christchurch, landslides can block roads, tsunamis

warning signs for earthquakes

changing groundwater levels, change in animal behaviour, seismometers and lasers detect movement

warning signs for volcanoes

earthquakes, gas, thermal changes, ground movement from rising magma

how do we detect tsunamis

seismometers, tide gauges, detection buoys

mitigation for hazards

lava pathways changed, coastal defences mangroves and coral reefs, resistant buildings, community preparedness

hazard disaster management cycle

monitoring and warning, hazard, emergency rescue, short term recovery, long term recovery, prevention and mitigation, disaster free period

info on japanese earthquake

march 11 2011, focus close to coastline, mag 9, 70km off coast

social impacts of japanese earthquake

15853 dead, cholera, 100,000 children separated, 4000 roads affected

economic impacts of japanese earthquake

181 billion gbp, 25m tonnes of debris, 4 ports destroyed, 11 nuclear reactors shut down

environmental impacts of japanese earthquake

natural water supplies damaged, land salinity

short term responses to japanese earthquake

100,000 members of japanese defense force helped, search and rescue from nz aus sk usa, red cross, 20km evacuation zone from fukushima power plant

long term responses to japanese earthquake

190 billion budget for ten years, sendai airport runway restored march 29

haiti earthquake facts

january 12 2010, mag 7, epicentre near port au prince

social impacts of haiti earthquake

over 230,000 died, 1 million homeless, 2 million no water or food, crime rates, cholera, 4000 inmates escaped from prison

economic impacts of haiti earthquake

1/5 lost jobs, 30,000 commercial buildings lost

environmental impacts of haiti earthquake

oil and chemicals leaked, water pollution led to cholera

short term responses to haiti earthquake

20 mil from uk govt, 10,000 us troops, water and purification tablets given out

long term efffects of haiti earthquake

rebuilding of port, over 1 million still in temporary shelters 1 year after

info on mt merapi

26 oct - 30 nov 2010, composite volcano, ash 30km away

impacts of mt merapi

200,000 homeless, 353 dead, water contaminated, 210 evac centres, planes grounded in west aus, lahars

responses to mt merapi

2682 permanently relocated, money for farmers livestock, 200 temporary shelters, evac plans improved

nevado del ruiz info

13 november 1985, stratovolcano, 30km ash, water from glaciers

effects of nevado del ruiz

lahars 30m deep 12m per second, 3400 ha of agricultural land, 50 schools, 23,000 killed in lahars, 7.7 billion dollars

responses to nevado del ruiz

colombian red cross, new warning plan, colombian military search and rescue

how many died in mt st helens

57

effusive characteristics

divergent / hotspots, lower viscosity hotter lava, less gas, less violent

explosive characteristics

convergent boundaries, thick acidic lava with more silica, violent