Natural Hazards Flashcards
(33 cards)
definition of a natural hazard
extreme natural events that can cause loss of life, extreme property damage and disrupt human activities
what is a METEOROLOGICAL natural hazard
atmospheric, eg tropical storms
what is a GEOMORPHIC natural hazard
occur on the Earth’s surface, eg. flooding
what is a TECTONIC natural hazard
Involves movement of tectonic plates in the earths crust, eg, earthquakes or tsunamis
what is a BIOLOGICAL natural hazard
involves living organisms eg. forest fires
how does MAGNITUDE affect risk?
(strength) size affects impact
how does FREQUENCY affect risk?
How often hazard occurs. more often = more prepared, adjust buildings and lives
how does DEVELOPMENT affect risk?
money available to prepare and respond to event. HICs better (more money/ tech, planning)
how does POPULATION DENSITY affect risk?
no. of people in area. more people = increased potential for disaster
how does EDUCATION affect risk?
people can be educated on how to survive NHs. saves many lives
how does NATURAL FACTORS affect risk?
e. g rock type in eq, shape of coastline.
- gently sloping coastline = increased damage in hurricane
- soft rock = larger and longer eq. more likely to collapse
how does MANAGEMENT affect risk?
some are easier to predict/ prepare for
describe the OCEANIC CRUST
- thinner and denser (5-10 km)
- basaltic rock
- SINKS when meets continental plates
- less than 200 mill years old (young)
describe the CONTINENTAL CRUST
- thicker (20-200km)
- granite rock
- up to 3.8 bill years old
CONVECTION CURRENTS
- magma rises in mantle.
- as it rises further from core, it cools and sinks.
- creates a current which moves plates with it.
what is ridge push?
- at constructive margins, ocean ridges form.
- beneath, mantle melts.
- molten magma rises as plates move apart and cool to form new plate material.
- as lithosphere cools = denser and slides down away from ridge causing plates to move away from each other = ridge push.
what is slab pull?
at destructive margins denser plate sinks back into mantle under gravity. pulls rest of plate with it = SLAB PULL
what happens at a CONSTRUCTIVE MARGIN?
- upper part of mantle melts and hot molten magma rises
- tectonic plates are moved away from each other. releases pressure and molten magma rises between
- it cools to form a solid rock. as the rich cools it becomes denser and sinks, causing tectonic plates to move further (ridge push)
- in a few places magma erupts onto surface producing runny kava that spreads out before solidifying, over many eruptions a shield volcano is formed
what happens at a conservative margin?
- occurs when plates move parallel to each other
- the 2 plates can move side by side, either :
- in the same direction but different speeds
- in opposite directions - earthquakes are found because pressure builds up as a result of friction between plates. eventually rock fractures and pressure is released = eq
what happens at a DESTRUCTIVE MARGIN?
- occurs when tectonic plates move towards each other and collide
- if 2 continental plates collide, they are both buoyant and cannot sink into the mantle therefore form mountains
- if oceanic + continental collide the denser oceanic plate is SUBDUCTED and sinks under continental plate
- as the plates converge pressure builds up. the rocks eventually fracture causing an earthquake. when the oceanic plate subdues, it pulls the rest of the plate along, causing a deep ocean trench on the surface
- as the oceanic plate sinks deeper into the mantle, it causes part of the mantle to melt. eventually it erupts, forming composite volcanoes
what were the PRIMARY IMPACTS of the Nepal EQ?
- buildings collapsed
- 8800 dead and 16800 injured
- 26 hospitals and 50% of schools destroyed
- 1.5 mil needed food and water
what were the SECONDARY IMPACTS of the Nepal EQ?
- avalanches
- death toll 9000
- landslides, nearly 400,000 cut off from outside assist
- fall in tourist no. = less money, tourism 10% of GDP
- EQ happened before monsoon. rice seeds destroyed = affecting harvest
- 3% more pushed into poverty
what was the RESPONSE of the Nepal EQ?
- international aid and search and rescue teams
- medical supplies and field hospital
- 9 helicopters rescued people from Everest
- $274 mill aid pledged by EU japan Us
- money spent on rebuilding, repairing and clearing roads
- heritage sites reopened encouraging tourists
why were the impacts of the Nepal EQ so bad?
LIC, cannot afford protection eg, eq safe houses
- can’t afford to rebuild
- tourism affected
- food supplies destroyed
