tectonics Flashcards
what is a natural hazard?
it is a natural event that has had a huge social impact
what factors affect hazard risk?
urbanisation
poverty
climate change
farming
what is an earthquake and where do they occur?
sudden violent period of ground shaking. most commonly caused by a sudden movement of rocks within the earths crust. mainly happens at margins of tectonic plates where they move and release enormous pressure build up
what are other ways earth quakes can be caused?
underground mining, oil extraction or reservoir construction
what are two types of crust?
thin oceanic crust and less dense, thick continental crust
why do plates move?
due to convection currents from deep within the earth. gravitational pull may play a part
what happens at constructive plate margins?
plates move apart and new crust is formed as magma rises towards the surface
what happens at destructive margins?
plates move towards each other, the denser oceanic plate may sink (subduct) beneath a less dense continental plate, gravity pulls the oceanic plate into the mantle dragging the plate away from the constructive margin
what is a volcano and where do they happen?
a large conical-shape landform usually formed over a long time by a series of eruptions. majority occur in long belts that follow the plate margins e.g. pacific ring of fire or middle of atlantic ocean-mid-atlantic ridge including azores and iceland which are volcanic islands
what are the three main types of plate margin?
constructive-two plates moving apart
destructive-where two plates are moving towards one another
conservative(transform)-where two plates are sliding alongside eachother
what is an example of a constructive margin?
constructive margin in the mid-Atlantic, magma forces its way to surface along mid-atlantic ridge. as it breaks through the crust earth quakes occur on reaching the surface earthquakes are caused.
magma-hot and fluid flows long way before cooling, broad and flat shield volcanoes
what is an example of a destructive margin?
the oceanic nazca plate, subducted beneath less dense south americican plate, friction between plates causes strong earth quakes. oceanic plate melts as it moves down.
magma-less fluid than at a constructive margin, breaks through surface to form steep sided composite volcanoes eruptions are violent
two continental plates meeting means uplift of crust e.g. himalayas no volcanoes-no magma
what is an example of a conservative margin?
friction between plates causes earthquakes, san andreas fault, the faster moving pacific plate slides in the same direction nect to slower north-american plate. earthquakes happen along these margins as stress is built up over many years, close to earths surface so destructive released when plates slip and shift no volcanoes.
what happened in the earthquake in Chile?
27th feb 2010. 8.8 richter scale earthquake. just off the coast of central chile. nazca plate moving beneath sout american plate-destructive margin.
what happened in the earthquake in Nepal?
25th apr 2015. 7.9 richter scale earthquake. epicentre was 80km to the north-west of capital Kathmandu foothills of himilayas. indo-australian plate collides with eurasian plate, destructive margin. shallow quake 15km below surface
primary effects of earthquake in Chile…
. 500 killed, 20,000 injured, 80,000 affected
.200,000 homes, schools, ports, hospitals destroyed
.talcahuanao airport port badly damaged
.lost power, water supplies and communications
.$30 billion
secondary affects of earthquake in Chile…
.1500km road damaged
.coastal twons devastated by tsunami waves
.other pacific countries affected by tsunami waves
.fire at chemical plant near santiago
primary affects of earthquake in Nepal…
.9000 died, 20,000 injured, 8 million affected
.3 million left homeless
.electricity, water supplies, sanitation, communications affected
.1.4 million needed food, water, shelter
.7000 schools destroyed and busy hospitals
.congested airport for aid
.50% shops destroyed
.$5 billion
secondary affects of earthquake in Nepal…
.landslides and avalanches blocking roads and help
.avalanches on mout everest killed 19
.avalanche in langtang region left 250 missing
.landslide blocked kali gandaki river, evacuated many incase of floods
.on land no tsunami
what are immediate responses?
search and rescue and keeping survivors alive by providing medical care, food, water and shelter
what are long-term responses
re-building and reconstruction with the aim of returning peoples lives back to normal and reducing future risk
