GCSE Geography - Hazards

what is a natural hazard

naturally occurring event that is a threat to the population and can cause loss of life or damage to important infrastructure

example of natural hazards

• Earthquake in nepal on April 2015

• killed 9000 people

• injured thousands and destroyed many homes

• huge negative social impact

difference between a hazard and an event

a natural event can only be classes as a natural hazard if there is a threat to people.

types of natural hazards

• geological hazards: hazards caused by processes on land

  volcanoes, earthquakes, landslides, mudflows

• hydrological hazards: hazards caused by the movement of water on the land

  flooding

• atmospheric hazards: hazards cused by the weather

  tropical storms, tornadoes, droughts

what is a hazard risk

the probability that a natural hazard will actually affect a population

what can increase hazard risk

• being more exposed to hazards (living next to an active volcano or ocean)

• high population density

• lack of preparation to hazards (poor access to healthcare)

hazard risk is affected by different factors

• uranisation: urban areas are packed with infrastructure and housing which will collapse

• population growth: as population increases, demand for housing is exceeding th supply so many people live in cheaper informal houses which will not withstand natural hazards and some are built on slopes.

• wealth: poverty can force populations to live in unsafe unsafe housing with less access to healthcare. wealthier countries can put more investments into defences for hazards (flood defences, earthquake proofing buildings)

• land use: many floodplains are very fertile so they are good for farming so people live there

• climate change: effects of climate change exposed more people to natural hazards. sea levels rise and changes in precipitation increased flooding, tropical storms becoming more intense, intense long droughts

layers of the earth

crust, mantle, outer core, inner core

plates and their physical properties

• continental crust: makes up land, old, less dense, thick

• oceanic crust: makes up ocean floor, younger but still very old, dense, thin

Plate tectonics theory- how convection currents work

• the core heats up the magma in the mantle

• the hot maga is less dense than its surroundings, so it rises upwards

• when it reaches the top, it cools

• it becomes more dense, and therefore sinks back down to the bottom

• it is heated up again, and the cycle continues

• the plates, which lie on top are pushes and pulled by the convection currents in the magma

Name the plates

1 - north american plate

2 - pacific plate

3 - nazca plate

4 - south american plate

5 - cocos plate

6 - caribbean plate

7 - african plate

8 - eursasian plate

9 - arabian plate

10 - indian plate

11 - australian plate

12 - philippine plate

13 - antarctic plate

supercontinent name

pangaea

theory of continental drift

fossils have made it possible to reconstruct the past movements of continents

where do tectonic hazards occur

• plate margins (west of north america and south america, atlantic ocean between africa and south america)

• ring of fire (pacific ocean)

why do volcano erruptions occur

when the magma from the magma chamber builds up and slowly feeds the volcano, this magma slowly pushes to the surface and erupts. the hotspot I where it erupts

why do earthquakes occur at plate margins

plate movements cause vibrations

where can volcanoes also occur

middle of the pacific plate where magma breaks through the middle of the plate and travels up to the surface which is knows as a hotspot. e.g. hawaii

← → plate

• constructive, move away from eachother

• when plates are pulled apart, magma rises in between the gap left by the two seperating plates. lava then pours out onto the surface

• volcanoes forms as the lava pours out. Lava is usually runny and free- flowing which creates shield volcanoes

• earthquakes can also occur here as the plates shake and vibrate when they move apart

• when new land is formed on the ocean floor it is knon as sea floor spreading

• when lava cools it forms rock, overtime, this rock builds up and form islands e.g. iceland as iceland sits on the mid atlantic ridge which is where the lava pours out from

→ ← plate

destructive, plates move towards each other

• the denser oceanic crust is subducted below the continental crust

• the plate that is subducting leaves a deep ocean trench

• friction between the two plates causes strong, deep earthquakes

• the oceanic crust is melted as it is pulled deeper into the mantle creating magma

• this magma causes pressure to build up under the crust

• eventually the magma pushes out through weaknesses in the crust, creating explosive volcanoes

destructive plate between two oceanic

the denser plate will sink below and islands in the ocean can form e.g. mariana trench

destructive plate between two continental plates

neither plate can subduct below the other. Instead the crust crumple upwards by the pressure building between the two plates, creating fold mountains e.g. Himalayas formed from indian and eurasian plate

sliding past eachother plate

conservative

• the plates move at different speeds. when these plates move past each other

• friction builds between the plates over many years and eventually the pressure becomes so large that the plates eventually move in a sudden jolt

• this releases a lot of energy which sends vibrations through the ground (earthquake)

• on oceanic crusts this movement can displace a lot of water which causes large waves called tsunamis

• on continental crust, fault lines can occur where the ground is cracked by the movement.

• there are no volcanoes on conservative, no magma is generated

primary effects

effects that are directly caused by the natural hazard itself. e.g. people killed or buildings destroyed

secondary effects

the effect that are a result of the primary effect e.g. homelessness due to homes being destroyed, tsunami or landslide caused by original earthquake

effects of tectonic hazards (primary: secondary)

eqarthquake: tsunamis, mudflows, avalanches, landslides

electricity, water, communications damages: fires from ruptured pipes, spread of disease due to poor hygeine, contaminated water

infrastructure and homes destroyed: social disorder or conflicts, conflicts

injuries or people killed from damage buildings, hot ash and gas from volcano: trauma, stress and other mental health issues after event, loss of incone as peoples livelihoods destroyed

responses to tectonic hazards meaning

how local community or government react to a hazard to effect can be reduced

immediate responses to tectonic hazards

actions taken as soon as tectonic hazard happens which usually aim to reduce loss of life and provide vital aid and resources.

examples of immediate responses

• searching for people under rubber

• emergency aid

• providing food and water

• setting up shelters

• cleaning roads to gain access to isolated areas and allow rescue services entry

long-term response meaning

taken after the immediate responses when the effects of the hazard have been minimised. aim to restore normality and reduce risk in the future

long term response examples

• investments and developments into hazard management, such as warning systems

• housing/infrastructure reconstruction

• insurance payouts

• making infrastructure safer

• reopening of tourist attractions to boost economy

why do people live in hazadous places stats

in 2015, 2.7 billion people live in seismically active areas and more than 400 million people live near one of the 220 most dangerous volcanoes

benefits that tectonic hazards bring

• when volcanoes erupt they emit lots of ash and material in the air which contain lots of nutrients and eventually settles on the ground. These nutrients find their way into soils and make the soil fertile. volcanic soils is the most fertile soil in the world

  e.g. mayon volcano

• hazardous areas can also have a well developed tourism industry which means they may choose to live there for work.

hazards are monitored and managed

• warning signs

• large earthquakes in the ocean can be monitored to tell people when there will be a tsunami

• many people live in hazadous areas as they know the risk will be reduced by warning systems

• better building design so people are less at risk.

  e.g. in japan where earthquakes are frequent, many buildings have carbon fibre ‘curtain’ to minimise the effects of shaking

infrequency of tectonic events

many people decide it is not worth giving up their area’s lifestyle and culture when tectonic hazards appear so infrequently

poverty and education

some people don’t have a choice as they can’t afford to move away. in less wealthy countries, the top priority is to have an income, food and necessities. so risk of hazard is a less pressuring issue

hazard management

• fewer effects

• monitoring: detecting and recording phyiscal changed and warningsigns

• predicting: using monitoring as well as historical trends and computer based modelling to predict when a textonic event may occur

• protecting: increasing the resistance of a population to tectonic hazards by physically designing things that will withstand tectonic hazards

• planning: having systems in place, such as evacuation routes, so that if an event does occur, the population is prepared in advance

monitoring

• earthquakes are difficult to monitor but scientists measure the small treamors and ground deformation and changes in groundwater.

• volcano: monitor ground deformation (buldges in the ground can indicate the movement of magma), gases (certain gases indicate rising magma, such as sulfurous gases), changes in heat (temperature differences also indicate processes beneath the surface), vibrations underground (small earthquakes can indicate changes underground), smaller eruptions of smoke and steam ( indication of a larger eruption coming)

• you can use satellites and sensors for volcanoes

predicting

scientists can predict that an earthquake can happen as one hasn’t happened for a while and it will be bigger as energy has been building up for a long time

protection

lessen the effects of hazards through building designs.

volcanoes: concrete blocks and explosives are dometimes used to divert or slow lava flows but this is only to redirect the flow from one place to another away from densly populated areas

eqarthquakes: buildings are constructed to be resistant to intense shaking. foundations can be built deep into the ground to reduce th risk of it collapsing

planning

• hazard mapping, diving different hazedous areas into different levels of risk and changing the land use accordingly, important buildings such as schools, hospitals are built further away.

• evacuation plans and safety protocols can be developed so the populations knows what to do if there is a hazedous event. earthquake drills are often practiced in areas where there are earthquakes often.

global atmospheric circulation

• movement of ai around the globe influences the temperature and humidity

• its a layer of air surrounding the earth’s surface and extends for hundreds of km high

• the air is constantly moving in different directions because of the sun’s energy, differences in pressure and the rotation of our earth

atmospheric circulation model

hadley cell - at the equator, hot moist air rises, moves to higher latitudes (30degrees) and sinks

ferrel cell - at around 60 degrees either side of the equator, moist air rises and travels to lower at around 30 degrees where it sinks, along with air travelling from the equator

polar cell: at 60 degrees north or south of the equator, moist air rises and travels to the poles (90 degrees) where it sinks

pressure belts

these create different areas of pressure

when air rises, it creates an area of low pressure underneath and when air sinks it creates an area of high pressure

• there are lower pressure at the equator and at 60 degrees either side due to the air rising here due to the heat from the sun being most concentrated along the equator

• high pressre at the poles and 30 degrees either side of the equator due to air sinking as its cold because its further away from the sun so it is heated less

wind

• created when air particles move, air particles will always move from area of high pressure to low pressure

how does wind move

wind is deflected in different directions because the earth is spinning, so wind will travel in a curved direction (coriolis effect). so the wind is deflected right in northern hemisphere and left in the southern hemisphere

Climate at the equator

• near the equator the sun shines directly on there.

• Hot moist air rises = area of low pressure. when moist air rises, it conenses to form rain clouds.

• causes the climate at the equator to be humid and very rainy. Tropical rainforets are found here due to warm and wet weather

climate at the subtropics

• dry air sinks at subtropics = area of high pressure

• clouds do not form here because air isnt rising so it is very dry.

• deserts

• very hot because of intense sunlight but very cold at night because there are no clouds to retain heat

climate at subpolar latitudes

• around 60 degrees north or south of the equator there is a low pressure belt causing the climate to be cloudy and wet

• the climate is not as warm as the sun shines less directly than the equator

tropical storms

• very large spinning storm that forms in the tropics and they have high winds and torrential rain and usually affects small islands and coastal regions

name for tropical storms around the world

hurricane - usa, latin america, caribbean

cyclone - australia, madagascar

typhoon - india, japan and philippines

causes of tropical storms

• form between 5-30 degrees north or south of the equator

• temperature: ocean temps must be around 26-27 degrees and at least 50 metres deep as the warm water provides the storm with energy

• air pressure: unstable air pressure (where low and high pressures meet so warm air rises and clouds can form

• wind shear: winds must be present for swirling motion to form but not too strong or the system will be ripped apart in its early stages

• rotation: will only form if there is coriolis effect

tropical storm formation

• warm moist air rises, leaving an area of low pressure below which causes the surrounding warm air to move into the low pressure area and rise.

• as the air rises it coolds so the air will condensate an form large thunderstrom clouds

• the system is spinning due to coriolis effect. in northern it spins anticlockwise, southern it spins clockwise

• constant additions of energy from warm air causes the storm to spin faster, generating higher wind speeds.

• storm develops an eye in the centre which is an area of etremely low pressure where cool, dry air descends. weather in the ey is relatively calm and cloud free

• surrounding the eye is eyewall which is the most intense and powerful area of th storm, warm, moist air rapidly rises with extreely high winds and torrential rain

• when the storm reaches a coast, low pressure and high winds will cause a large amount of sea water to be puhed onto the coast which is storm surge. when storm reaches land it has no more energy supply and the eye will collapse and the storm dissipates