hazards geography aqa alevel

whats a hazard

a potential threat to human life and property caused by an event:

CRED - states that a hazard becomes a disaster when 10+died, 100+ injured

characteristics of a hazard

- clear orgin

- short warning period

- type of exposure to risk

- long term effect

- require emergency response

whats a disaster

event or process which does cause damage to life and/or property

whats a risk

the probability of a hazard event occurring and creating loss or lives and livelihood

how do we put ourselves at risk

- building poor quality houses ( e,g rio)

- living on active fault lines (e.g Christchurch)

- urbanising in volcanic zones ( e.g naples)

- inhabitat in low lying coastal areas ( Thailand )

why do people put themselves at risk

- hazard events are unpredictable

- lack of alternatives- it is not easy for people to move homes because of economic and many other reasons.

- Perception (fatalism)

- changing levels of risk ( deforestation)

- cost benefits

hazard perceptions change due to

- mobility ( limit access)

- wealth

- religion + beliefs

- education

- experience

whats vulnerability

defined as the characteristic and circumstances of a country's environment and people that make it susceptible to the damaging effect of a hazard event, can change overtime

social factors the effect vulnerability

- age ( 75% that died in hurricane Katina where over 60)

-gender

- proximity

- technology

- population density

-socio economic income

- inequality of access to education

- environmental degradation ( mangroves saved lives in 2004 tsunami disaster)

what are plate tectonics

mechanism by which the continent more around the surface of the earth

- America moving further from Europe

- Pacific is getting smaller

- Himalayas are going up

continental drift

Alfred Wegener 1912

- proposed continents moved apart from being one big super continent ( Pangea)

evidence

- fossils ( same in South America and africa)

- jigsaw

- geology, matching rock formations

this theory was dismissed due to inadequate explanation of the force responsible

Sea floor spreading theory

Harry Hess

- argued that oceans were shallower in the middle, where the were mid ocean ridges raised upwards and the deepest parts were closer to continent margins

- he believed oceans grew from their centres

-seafloor spread away from the middle ridge in both directions

palaeomagnetism

vine + matthew

- approximately every 400000years the earths magnetic field switches polarity causing the magnetic north + south poles to swap

-magnetic from lava cools and aligns with the magnetic orientation at the time

- they discovered the north and south facing magnet running parallel to the North Atlantic ridge showing that a new ocean floor was created

convection current theory

- earths mantle is hottest closest to the core, so lower parts of the atmosphere heat up, become less dense and slowly rise

- as they move to the top they cool down become more dense and slowly sink

- circular movements create drag on the base of the tectonic plates causing them to move

ridge push

new oceanic crust is formed at mid ocean ridges. it stands 2-3km above ocean floor, as the crust moves away it cools and becomes denser and thicker, causes the lithosphere to slope away from the ridge and gravity pulls it down the slope

slab pull

subduction zone is formed when two plates move towards each other. heavier denser oceanic plate subjects under lighter less denser plate, as the plate sinks gravity pulls the plate down the mantle

fold mountains

found a destructive collisions, movement is connection currents

trenches

found at destructive subduction zones, link to slab pull

island chains

created by plates drifting over hot spots

ridges

found at constructive plate margins, movement is seafloor spreading due to connection currents and ridge rush

land forms ; plate boundary - destructive

- continental = earthquakes, fold mountains

- oceanic = ocean trenches, island arc, volcanoes, earthquakes

- contiental and oceanic = volcanos, fold mountains and earthquakes

land forms ; plate boundary - constructive

- continental = rift valleys, earthquakes, volcano

- oceanic - volcano, ocean ridges, earthquakes

land forms ; plate boundary - conservative

- earthquake

human response to hazard

hazard management such as prediction, prevention, protection

risk sharing

prearranged measures that aim to reduce the loss and property damage through a variety of measures

how's the community not Bangladeshi risk sharing

- evacuation procedures

- 76000 volunteers for wide evacuation

- emergency supplies and shelters

evaluation management

- engineers success fully diverted a potentially hazardous lava from MT Etna

- concrete seawalls, breakwaters and coastal structures constituting 40% of japans 22000 mile coastline

Park Model (Disaster response curve)

a model graph to show the effects of a hazard on quality of life over a sequence of time and expected stages from pre-event to eventual recovery

-pre disaster( normal quality of life)

- relief (during and immediately after disaster

- rehabilitation ( thinking about longer term problems)

- reconstruction

Hazard management cycle

model that shows the attempt by emergency planners to minimise the loses

- preparedness ( uses data from previous events to plan)

- responses ( save people)

- recovery( post disaster reconstruction )

- mitigation (steps taken to minimise impacts)

features of hazard management cycle

- steps taken before hazard are taken into account to minimise impact

- considers hazards are connected

- focus of management rather than impact

- model speeds up recovery

- no time scale

features of the park model

-speed on return to normality helps us under stand how prepared a community was

- could be used to directly compare two events

- allows us to compare the significance of event to normality

- doesn't specify steps before event

features of both models

- doesn't take into account the complexity of secondary impacts

- over simplistic compared to reality

- helps to follow stages of disaster

Earth Structure and composition

consists of core, mantle, and crust

inner core

A dense sphere of solid iron and nickel at the centre of Earth. (5000degrees)

outer core

A layer of molten iron and nickel that surrounds the inner core of Earth ( liquid)

Mantle

semi liquid, containing low density material, 2900km thick, upper part is known as the asthenosphere

Crust

solid and divided into two main types of crust; oceanic + continental

- varies between 6-70km

lithosphere

lowest part of the crust

oceanic crust

- 6-10km thick

- age 200m

- density 3

- composition basalt

continental crust

- 30-70km

- age 1500m

- density 2.6

- compassion granite

earths internal energy store

primordial heat left over from the earths formation, radiogenic heat produced by the decay of radioactive isotopes such as uranium

Inge Lehmann

discovered that the inner core must be solid due to P-wave acceleration

classification of types of lava

- basalt ( 48-52 silica content- so less viscous) ( high temp 1160)

- andesite ( 52-63 silica content)(1000 temp)

- rhyolite ( 68-77 silica content - more viscous)( 900 temp)

Viscousity

How runny something is. Highly viscous = very thick, low viscosity = liquidy

frequency

frequency depends on type of volcano

- constructive volcanos are more frequent the destructive volcanos

destructive volcano lava

more viscous lava, cooler lava, composite volcano

e.g Yellowstone caldera erupts 3x in last 2million Years

constructive volcano lava

less viscous lava, hotter lava, shield volcano

e.g Kilauea is an active shield volcano

pyroclastic flows ( nuee ardente)PRIMARY

mixture of superheated gas ash and volcanic rock

- travel high speed 80km/h

- flows a long way 10-15km

- widespread death and destruction

lava flow PRIMARY

- destroys anything in its path

- low viscous lava flows 10km/h

volcanic gas PRIMARY

- contain co2 and sulphur dioxide and released in eruptions

- harmful when breathed

Tephra PRIMARY

rock fragments and particles ejected by a volcanic eruption.

can fall on people and kill them

Ash fallout PRIMARY

thick layer of ash that settles down, after being ejected from a volcano

Lahar ( mudflow) SECONDARY

occur when volcanic material mixes with water

- flow 80km/h

- destroy habitats

flooding SECONDARY

grimtotm volcano causes regular glacier outburst caused by geothermal + volcanic activity causing ice to melt and abrupt;y release

landslide SECONDARY

a slide of a large mass of dirt and rock down a mountain or cliff

- travels at a speed of 1,072

Tsunami SECONDARY

large wave of water eruption triggered by landslide

-anak krakatau tsunami killed hundreds

acid rain SECONDARY

volcanic gases react with water vapour in atmosphere - falls as acid rain

- damage eco system

climate change SECONDARY

gases + dust particles can cause temporary cooling by shading incoming solar radiation, if particles are launched high enough into the atmosphere

- 1816 ' year without summer' mount tambra triggered

impacts of volcanic eruptions social

- pyroclastic flows + lava can start fires = destroy

- people are killed, infrastructure destroyed

impacts of volcanic eruptions economic

- eruptions can destroy businesses

- air clouds can prevent aircrafts and crops

-eruptions can boost tourism economy

impacts of volcanic eruptions environmental

- flows and fallouts of volcanic material destroy ecosystem

- reduces sunlight

- decrease temperature

- enhance greenhouse effect

impacts of volcanic eruptions political

- governments spend money on repair

- damage to agriculture can lead to food shortages

mount nyrignongo risk managment

- threat of co2 pools

- change pressure of magma chambers

- practice drills

- gas measurements

- lava chemical make up

- infra red sound recording

Global Distribution

- 500 active ground around the world

- 50 erupt a year

- pacific ring of fire

Volcano Classification

active, dormant ( may erupt ), extinct

what makes a volcano dangerous

- what is exploded out ( lava, gas,rock)

- how often it erupts

- how fast the lava flows

- how explosive it is

magnitude of volcanic eruptions

- using a logarithmic scale 0-8, called the volcanic explosively index ( VEI)

Constructive margin description

- basaltic lava

- lava is hot

- lava has low viscosity

- eruptions are frequent

- eruptions last long

- create ocean ridges if underwater

- eruptions aren't violent- little pressure

- shield volcano

destructive margin descriptions

- andesitic + rhyolitic lava

- lava is cooler

- lava has high viscosity

- eruptions are intermittent

- eruptions are short lived

- fold mountains conform parallel to volcanoes

- eruptions are violent due to viscous lava forming blockage vents

- composite volcanoes

does hazard percpetion affect impact

e,g in murapi there is a fatalist perception on hazards therefore loads of the population stayed in their homes and accepted their fate and developed rituals and practices ti come to terms with it

in contrast

e.g richer countries can be comp.acent and underestimate the risk in japan and New Zealand tourists where taking selfies as the volcano was exploding

volcanic risk management - preparedness

happens before an eruption to minimise risk of vulnerability

- monitoring system to predict

- authorities can stop people entering certain areas

- make evacuation plan

- emergency shelter and kits

- rescue teams

volcanic risk management - mitigation

physical actions taken to reduce the impact

- mount Etna - divert lava through trenches

- hawian isalnds - barrier protects settlements from lava

volcanic risk management - prevention

not possible to prevent volcanic eruptions, but possible to prevent it from posing risk

- canary islands - 7000 leave their homes ( forced by gov)

- exclusive zones made so people cant live there

sesmic hazards - earthquake

and earthquake is a sudden violent shaking of the ground

- tectonic plates move and becomes located together causing stress and pressure build up

- stress becomes so great so rocks fracture and pressure releases

- causing intense ground shaking

what makes a strong earthquake

- shallow depth

The depth of earthquakes affects the strength of shaking felt at the surface, with deeper earthquakes resulting in weaker shaking.

Global Distribution of earthquakes

- nearly all earthquakes(95%) found along plate margins

- 70% found in the ring of fire in the Pacific Ocean

- most powerful earthquakes are on destructive plate boundaries

what does intraplate mean

means the earthquake occurs on the interior of the tectonic plate e.g england

what does interpolate mean

occurs at the plate boundaries e.g the ring of fire

how to measure earthquakes

- moment magnitude scale ( monitude and energy released )

- modified mercali scale ( measure impact on location)

- seismometer ( produce seismograms)

primary wave type

- push and pull the group d

- travel away from the earthquake

- fractured rocks due to compressing and expanding

- travel through solids and liquids

- longitudinal

secondary wave type

- shake ground side to side

- travel slower, only travel through solids

- transverse

love or surface wave type

- move ground side to side

- p+S waves reach surface they turn into surface/love waves and move back and forth

responding to a seismic hazard - adaption

- move away from the risk area

- capitalise on the opportunity

- get insurance

responding to a seismic hazard - preparedness

- have plans and kits and shelters ready

- do evacuation drills e.g japans disaster prevention day on September 1st

responding to a seismic hazard - prediction - radon gas

measure it from leaking out the cracks, radon gas levels also influenced by temperature and air humidity

responding to a seismic hazard - prediction - foreshock

seismometer indicates large earthquake

responding to a seismic hazard - prediction - animals

todds lead before Italy 2009 earthquake

responding to a seismic hazard - prediction - role of scientist

- 5 men found guilty of man slaughter as they didnt predict an earthquake

responding to a seismic hazard - prediction - seismic gaps

if theres no or little movement at the plate margin there should be one soon e.g istanbul

responding to a seismic hazard - mitigation

- tsunami = 15m wall

- hazard resistant structures = wellington central police station exterior wall has cross bracing

- early warning systems = Japan has early earthquake warning systems on TVs

responding to a seismic hazard - prevention

- fault lubrication = injecting water into faults

- seismic wave shielding = altering soil properly around buildings reflects waves

- seismic cloaking = concrete pillar

what are tropical storms

- intense low pressure systems

- rising air

- uk gets depressions not tropical storms

where do tropical storms occur

- Tropic of Cancer and Capricorn, where the sea temperature is 27 oC or above

- in the summer it is near the equator and found in low latitudes ( often between 5-30)

- they dont occur at at 0-5 latitude due to the coils effect not being strong enough

factors effecting the formation of tropical storms- coriolois effect

rotation of the earth causes the air to move around the centre of the eye in a circular motion

factors effecting the formation of tropical storms- oceans + high temp

tropical storms gain moisture from oceans, oceans also need to be over 27degrees to provide sufficient energy to power the storm

factors effecting the formation of tropical storms- low wind shear

low wind shear is a change in direction of wind speed with height

- if its not too high it can disrupt the organisation of the storm and prevent it from strengthening

hazards of tropical storms

- highwind = damage trees, life and builidngs-Haiyan 300km/h

- intense rainfall= leads to flash flood- Haiyan 450m rainfall

- storm surges = large volume of water forced inland by low pressure

- flooding = triggered by storm surges and heavy rainfall

- landslides = triggered because soil becomes saturated for floods ( venzula killed 10,000 people)

measuring tropical storms

Saffir-Simpson Scale - rate storms from category 1 ( weak) to 5 (strong)

- tropical storms are considered major when they reach category 3 and have wind speeds over 11miles per hour

why is the saffir Simpson scale bad

as it measures windspeed and that's not the only factor that determines severity

- 90% of deaths from tropical storms are not the result of wind but water

How to we gather data to predict tropical storms

- collect data from satellites, weather balloons, radon and ocean buoys

- data collected includes - atmospheric pressure, windspeed, direction, humidity, sea surface, temperature, ocean current