natural hazards Flashcards
Natural Hazard
A natural hazard is a process where it could cause death,injury or disruption to humans or property or possession.
Natural Disaster
A natural disaster is a natural hazard that has actually happened.
Geological Hazard
G.H caused by land and tectonic processes. Include volcanoes and earthquakes.
Meteorological Hazards
M.H caused by weather and climate + TROPICAL STORMS AND EXTREME WEATHER.
What are the 3 different hazard risks?
Vulnerability
Capacity to cope
Nature to Natural Hazards
Vunerablity
More people that in an area exposed to nat haz the greater the probability they will be affected by nat haz.
E.g area w high population on flood plain - flooding
Base of a volcano - volcanic eruptions.
Capacity to cope
Better pop can cope w extreme event the lower the risk of them being severely affected. E.g HICs better able to cope w flooding bc they can afford to build defenses and evacuate people.
Nature of Nat Haz
Type - risk from some haz are greater than others
E.g trop storm can be predicted and monitored to give people time to evacuate
Frequency - nat haz occur more often may carry higher risk.
Magnitude - more server nat haz tend to have greatest effects. E.g mag 9.0 earthquake that struck Japan in 2011 killed 15K
6.3 magnitude earthquake in Italy in 2009 killed 300.
how thick is continetal crust
continetal crust is 30-50km is thicker
How thick is oceanic crust
Oceanic crust is thinner (5-10km) and more dense.
What is the name of when plates are moving in the mantle?
Convection Currents
What is the name of the plates meet?
Plate margins or plate boundaries.
Destructive margins
Two plates are moving towards eachother
When an oceanic plate meets a contintetal plate the denser oceanic plate is sub-ducted and destroyed.
Volcanoes and ocean trenches occur here.
When 2 contential paltes meet, the ground is folded upwards + fold mountains.
Constructive margins
Where 2 plates are moving away from eachother. Magma rises from the mantle to fill the gap and cools + new crust.
Conservative Margins
Where 2 plates are moving sideaways past eachother or are moving in the same direction but at different speeds. Crust isnt created or destroyed.
Destructive margins - volcanoes
the desner oceanic plates moves down into the mantle where it melts. A pool of magma forms which then rises through cracks in the crust called vents. The magma erupts = volcano.
Constructive margins - volcanoes
the magma rises up into the gap created by the plates moving apart=volcano
Hotpsots
Some volcanoes that form over parts of the mantle that are really hot.
How do pyroclastic flows happen?
When a volcano erupts it emits lava and gases. Some volcanoes emit lots of ash which can cover land and block out the sun.
Destrcutive margins - earth
Tension builds when one plate gets stuck as it moves past the other
Constructive margins - earth
tension builds along cracks in the plates as they move away from eachotherc
conservative margin - earth
tension builds up when plates that are grinding past eachother get stuck.
Shock waves
Plates eventually jerk past eachother sending out shock waves. Vibrations = earthakes.
The SW spread out from the focus the point in the earth where the earthake starts. the waves are stronger near the focus and cause more damage.
Epicentre
the point on the earths surface straight above the focus.
Moment magnitude scale
measures the amount of energy released by an earthuake
it is a logarthimic scale so mag 7 would cause 10x more ground shaking then mag 6.
new zealand`
place - kaikoura new zealand
date - 14th nov 2016
plate boundary - destructive and conservative - the pacfic plate is subducting benath the australian place to the north and sliding past it to the south.
mag - 7.8 mmscale
new zealand - primary effect
2 people died and over 50 injured.
10ks homes + destroyed damaged
60 ppl = emergency housing
total cost of damage was around 8.5 billion dollars.
+200km road + over 190km of rail line + destoryed.
Communcations,water,sewage + power supplies + cut off.
NZ - secondary effects
earthake triggered up 100k landslides which blocked major road and rail routes
major landslide blocked the clarence river leading to flooding and evacution of 10 forms.
earthake generated a tsunami w waves of around 5m + leaving debris up to 250m land.
nz - immediate response
tsunami warning was issued fast + residents of coastal areas were told to move to higher ground.
100s of ppl housed in emergency shelters.
200 of most vulnerable ppl were evacuted from kaikoura by helicopter within 24 hrs of the earthuake.
power was restored to most places within a few hours.
temporary water supplies were set up.
international warships were sent to kaikoura with supplies + food,medicine + portable toilets.
nz- long term response
5.3 mil dollar funding provided by the kaikour district council to help w the rebuilding the town’s water systerms + harburs.
most road + rails routed were repaired + reopned within 2 yrs.
Kaikoura Mayoral Earthake Relief Fund set up to help residents who couldnt afford basic supplies + donations were recieved from around the world.
By march 2017, a permanet water main ad been laid in kk the new pipe was desgined to move with any future earthake so it wont break.
nepal
place - gorkha nepal
date - 25th april 2015
Plate boundary - destructive - the indo-australian plate is being subducted benath the eurasian plate.
mag - 7.8
Nep - pimary effects
around 9k died and 22k+ injured
estamiated 800k buildings damaged or destroyed
4mil ppl left homeless
cost of damage over 5.5bil
roads and bridges were destroyed
water tanks and pipes were destroyed leaving 2 mil people without access to clean water and sanitation.
Nep - immediate respon
india and china sent teams to help residents rescue people trapped by debris but lack of tools + machinery slowed down rescue efforts.
ppl tried to recover the dead and treat the injured but damaged roads made it hard for emergency workers aid to get through.
charites = oxfam provided medicine,food and temporary water supplies
red cross set up emergency sheleters for 130k families who had lost their families.
Nep - long term respon
world bank group financed 500 mil worth = projects to build earth ake resistant housing and repair roads an irrigation systems.
Some projects are still on going.
The road from nepal-tibet was reopened after 2 yrs after the earth ake many roads wre still damaged.
many heritage sites were reopened in june 2015 to encourage toursits back to the area.
water supply is being restored but 2 yrs after the event many people still didnt have access to clean water.
NGO’s are working w residents to increase their resilence to disasters for example providing alternatives energy sources.
why do people have risk and example
many people live close to volcanoes or in area vunerable to earth akes some peopel dont have a choice. e.g they may not be able to afford to move or they may not know the risks.
why do people choose to live in hazard earth ake
theyve always lived there - moving = leaving jobs or families.
in wealtheir countries effective monoitoring and evacuation plans can minimise risk.
the minerals from volcanoes from volcanic ash makes volcanic soil v. fertile - farers for e.g mineral rich soil around mount etna.
managment strategy - monotiring
earth akes
earth akes - seismometers and lasers monitor earth movements and can be used in early warning system to give a small but vital amount of warning before a large earth ake occurs.
managment strategies - prediction
earth ake
earth akes - cant be reliably predict but scientists can forecast where they may occur moinitoring the movement of tectonic plates.
managment strategies - protection
earth
earth akes - new buildings can use reinforced concerte that absorb an earth ake’s energy. existing buildings and bridges can be strengthened with steel frames so they’re less likely to collaspe. automatic shut off switches can turn off gas and electricty supplies to prevent fires.
mang start - planning both
future dev can avoid high risk areas
govt can plan evacution routes to get people away fast and safely.
management strats - monitoring
v.e
volcanic eruptions - scientists can monitor the tell - tale signs that come before an eruption = tiny earth ake escaping gas and changes in shape of a volcano.
mang strat - monitoring v.e
volcanic eruptions - can be predictied if scientists monitor volcanoes closely.
managment strategies - protection
v.e
v.e - buildings can be strengthened so that they’re less likely to collapse under the weight of ash. trenches and barriers have been used to try to divert lava away from settlements but w little success.
what does global atmospheric circulation mean
transfer of heat from the euator to the poles by the movement of air.
why does air move
air moves due to the diffrences in air pressure winds blow from high pressure areas to low pressure.
how is the global atmospheric circulation system divided into loops
each cell has warm rising air that creates a low pressure belt and cool sinking air that creates a high pressure belt.
describe atmospheric circulation system
1) the sun warms the earth at the euator causing the air to rise. this creates a low pressure belt
2) as the air rises it cools and moves away from the euator
3) 30 degrees north and south of the eator the cool air sinks creating a high rpessure belt
4) at the ground surface the cool air moves either back to the eator or towards the poles. these winds curve because of the earth’s rotation this is the coriolis effect.
5) 60 degrees north and south of the eator th ewarmer surface winds meet colder air from the poles , the warmer air rises creating low pressure.
6) some of the air moves back towards the eator and the rest moves towards the poles.
7) at the poles the cool air sinks creating high pressure the high pressure air is then drawn back towards the eator.
Global atmospheric circulation influences weather and climate
at the eator sun is directly overhead - earth’s surface recieves a lot of solar radiation so its hot. warm moist air rises and forms clouds = rains
by the time it reaches 30 N and S of the eator releases most of its moisture as rain. dry air = few clouds + little rainfall so deserts are often found at this latitude.
UK lies close to low pressure zone @ 60 N. warm rising air brings lots of cloud cover and rainfall often as low pressure systems carried from the atlantic by westerly winds.
tropical storms develop..
between 5-30 degrees north and south of the eator when
- sea temp is 27 degrees celusis or higher
- wind shear between the higher and lower parts of atmposheric is low.
how do trop storms develop over warm water?
- the warm surface water evaporates,rises and condenses into clouds. this releases and condenses into clouds huge amounts of energy , producing powerful storms. the rising air creates an area of low pressure which increases surface winds. Low wind shear prevents clouds breaking up as they rise so the storm stays intact.
- easterly winds near the eator more trop storms towards the west.
- the storms spin bc of the corralis effect.
- as the storms moves over the ocean the energy from the warm water strengthens the storm so wind speeds increase. Storms lose strength when they move over land or cooler water bc the energy supply from the warm water.
- majority of storms occur in the nothern hemisphere from aug - oct while in he southern hemisphere most storms occur from dec - april.
Features and strucute of a trop storm - centre of the storm
eye - up to 50 km across and is caused by descending air . theres v low pressure,light winds, no clouds,no rain and a high temperature in the eye.
Features and strucute of a trop storm -
they eye is surrounded by
eye wall - where theres spiralling rising air very strong winds storm clouds torriental rain and a low temperature.
Features and strucute of a trop storm -
towards the edges of the storm
the wind speed falls, the cloud become smaller and more scattered, the rain becomes less intense and the temperature increases.
