Geography- Natural Hazards

natural hazards ocr syllabus b

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  • Created by: georgia s
  • Created on: 27-04-12 15:14

What is a Natural Hazard?

  • An extreme natural event or process that causes loss of life and/or extreme damage to property and creates severe disruption to human activities. They include earthquakes, tsunamis, volcanic eruptions, tropical storms, floods and drough.
  • Tectonic Hazards-These are natural hazards caused by the movement of tectonic plates e.g. volcanoes and earthquakes
  • Climatic Hazards-These are caused by the weather, they include tropical storms and drought.
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Constructive/Divergent Boundaries

  • Places where plates are moving apart are called divergent boundaries. When the crust it pulled apart, it typically breaks along parallel faults that tilt slightly outward from each other.As the plates separate along the boundary, the block between the faults cracks and drops down into the soft, mantle. The sinking of the block forms a central valley called a rift. Magma seeps upward to fill the cracks. In this way, new crust is formed along the boundary.Earthquakes occur along the faults, and volcanoes form where the magma reaches the surface.

EXAMPLE- the Eurasian plate and the North American Plate are moving apart at the mid-Atlantic ridge.(

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Destructive Boundaries

  • These are where two plates collide with each other.
  • When an oceanic plate collides with a continental plate the oceanic plate is forced downwards into the mantle forming a subduction zone (the area of a destructive plate boundary where one plate descends beneath another)
  • This forms a deep trench in the ocean, the edge of the continental plate is folded upwards into a mountain range. Intensive folding and bending makes rock in both plates break and slip causing earthquakes. 
  • As the edge of the oceanic plate descends into the mantle, some of the rock in it melts.The melted rock rises up through the continental plate, causing more earthquakes on its way up, and forming volcanic eruptions where it finally reaches the surface.

Example:Where the oceanic Nazca Plate is crashing into the continent of South America. This crash formed the Andes Mountains, the longs string of volcanoes along the mountain crest, and the deep trench off the coast in the Pacific Ocean.

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Conservative/Transform Boundaries

  • This is when plates slide past each other, or are moving in the same direction
  • They don't slide past each other smoothly, they often get stuck. Pressure builds up until suddenly the plates jump forward, sending out shock waves that cause an earthquake.

Example: The San Andreas Fault. The area of California to the wet of the fault is slowly moving north relative to the rest of California

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Global Distribution of Drought


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1)Evaporation for the surface of the ocean, because of unusually high ocean temperatures of 27 degrees or higher.

2)Fast-rising, warm, moist air rises creating an area of very low pressure- the eye of the storm- which sucks in air.

3)The coriolis effect (earths spinning) starts spinning the air 

4)The rotating winds cause low pressure close to the equator and absorb the moisture from the oceans, creating hurricaines, cyclones or typhoons. Features

  • Sea temp must exceed 27 degree to be at least 60m deep
  • Depth of water is 60m at 27 degrees
  • Time of year- May to November in the Northern Hemisphere, November to April in southern hemisphere
  • Typical size is 700km in diameter and can exceed 13km in height
  • Anti-Clockwise wind rotation in northern hemisphere
  • Clockwise wind rotation in southern hemisphere 
  • Areas of the world- Caribbean, central america, south east asia, indian subcontinents
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Hurricane/Cyclone 3


  • Ocean Temp= Must exceed 27 degrees to be at least 60m deep
  • Depth of water= 27 degrees equals 60m
  • Time of year= may to november in northern hemisphere, november to april in southern hemisphere
  • Typical Size= 700km in diameter and can exceed 13km in height
  • Direction of wind rotation= northern hemisphere is anti-clockwise, southern hemisphere is clockwise
  • Areas of the world- Caribbean and central America, south east asia and Indian subcontinents
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How Tropical Storms Affect People and Places?

Tropical Storms can damage buildings, power, cables and crops. Flooding can be caused by the heavy rainfall brought by a tropical sotrm and also through storm surges 

Storm Surge-A rising of the sea as a result of atmospheric pressure changes and wind associated with a storm.

An MEDC is better placed to deal with the effects of tropical storms. They have technology, such as weather satellites, to enable them to monitor and predict storms and have well-equipped infrastructure to deal with them when they do strike.

Often in LEDC's people don't have the means to move inland away from the storm and therefore the impact is usually greater.

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Primary Effects of A Hurricane/Cyclone


  • Buildings and bridges are destroyed
  • Rivers and coastal areas flood.
  • People drown, or they're injured killed by debris that's blown around
  • Roads, railways, ports and airports are damaged
  • Electricity cables are damaged, cutting off supplies
  • Telephone poles and cables are destroyed
  • Sewage overflows due to flooding, the sewage often contaminates water supplies
  • Crops are damaged and livestock is killed
  • Heavy rain makes hill unstable,causing landslides
  • Beaches are eroded and coastal habitats are damaged.
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Secondary Effects of a Hurricane/Cyclone


  • People are left homeless
  • There's a shortage of clean water and a lack of proper sanitiation- this makes it easier for diseases to spread
  • Roads are blocked or destroyed so aid and emergency vehicles can't get through
  • Businesses are damaged or destroyed causing unemployment
  • There's a shortage of food because crops are damaged and livestock has died
  • People may suffer psychological problems if they lost people close to them
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Human Activities on Drought

Humans have made the impacts of drought worse:

  • Overgrazing reduces vegetation in an area. This makes the soil erosion caused by drought even worse-with fewer plants, the soil isn't held together as strongly so it's eroded more easily 
  • Excessive Irrigation- Irrigation is where water is artificially supplied from rivers or lakes to farmland to increase crop production. However, excessive irrigation depletes rivers and lakes, which increases the impact of drought because there's less water. Also when irrigation water evaporates, salts are left in the soil (salinisation). Crops don't grow as well in salty soil, therefore increasing the impact of drought.
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Case Study-Cyclone Nargis, Myanmar 2009 LEDC


  • date of cyclone: 2nd May 2008
  • cost of damage: around $4 billion
  • Myanmar is an LEDC with a population of 55 million
  • It is one of the poorest countries in South East Asia
  • It has restricted development mainly due to issues with the ruling military government and a desire to be isolated from the world.
  • GDP per capita of £1900

Environmental Impacts

  • Over 75 years Myanmar has destroyed 85% of its mangrove swamps, these should have served as a natural barrier to stop storm surges
  • 2nd May, the storm's winds reached speeds of over 217 kph and it hit the vast delta of the irrawaday river is Myanmar, bringing torrential rain and storm surges to low lying and agircultural delta
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Case Study-Cyclone Nargis, Myanmar 2009 LEDC 2

Social Impacts

  • UN estimated 1.5 million people were affected 
  • estimated 130,000 death toll
  • some reports suggest 95% of buildings destroyed, and all suffered significant damage, including roofs being ripped off
  • sewerage systems were overwhelmed causing leaking which contaminated rice fields and caused disease
  • Electricity lines were also destroyed
  • roads swept away 
  • dirty water encourage vast numbers of mosquitoes to breed
  • many people drowned
  • development put back by years
  • stagnant water caused mosquitoes to breed causing malaria

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Case Study-Cyclone Nargis, Myanmar 2009 LEDC 3

Secondary Impacts

  • 2-3 million people were made homeless
  • over 70% of households didn't have access to clean water
  • more mosquitoes, leaking sewerage so more disease
  • Myanmar relies heavily on exports of things like oil, lack of roads and railways mean that the country has been unable to exploit its natural wealth

Reasons for Severity of Impacts

  • Indian and Thai weather agencies warned the Burmese gov that cyclone Nargis was likely to hit the country, but the Burmese forecasters reported there was little or no risk. This increased the death toll because people weren't evacuated in time
  • There were no emergency or evacuation plans.
  • Burma's Government initially refused to accept foreign aid, aid workers were only allowed in 3 weeks after the disaster occurred, this increased the numbers killed because help came too late for some.
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  • A drought occurs when there is less than normal rainfall over a set period of time also when evaporation is higher than perspiration
  • Water supplies e.g. lakes are depleted during a drought because people keep using them but they aren't replenished by rainfall. Also droughts are often accompanied by high temperatures which increase the rate of evaporation, so water supplies are depleted faster.

Climatic Conditions

  • Droughts are caused when changes in atmospheric circulation mean it doesn't rain much in an area for years
  • Changes in atmospheric circulation can also make the annual rains fail
  • Droughts are also caused when anticyclones (high pressure weather systems) block depressions (weather systems that cause rain)

Areas that are most at risk from drought are north-eastern Africa, the Sahel, southern Africa, the Middle East, Australia and parts of eastern South America and Indonesia. 

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Factor Affecting the Severity of Drought

Social- The number of people affected has an impact on the amount of water needed. Demand is greater in developed countries.

Economics- Wealth of people coping with low rainfall e.g. whether they can afford to build new resevoirs, wells etc.

Climate- Areas of low rainfall are more susceptible to drought; temperatures affect evaporation.

Use and Users- In an LEDC subsistence community people use less water, but only a small reduction in water supply can have devastating effects on the quality of life. Luxury users in an MEDC will not usually suffer life-threatening impacts during periods of drought. Use affects the sustainability of water supply

Environment- Different types of rock allow water to be sotred or run across the surface; different land users affect runoff rates.

Technology- Levels of technology have an impact on the efficiency of water storage and new ways to supply water

Politics- Wars and civil war affect people's access to water. In developed countries it is easier to implement laws to control use of water.

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Primary&Secondary Impacts of a Drought


  • Vegetation dies
  • People and animals die from dehydration
  • Aquatic Animals die because lakes and rivers dry up
  • Soil dries out and is easily eroded by the wind and rain

Secondary Impacts

  • Animals die from starvation because there's no vegetation.
  • There's a shortage of food because crops have failed and livestock has died, so people die from starvation
  • Soil erosion is increased because there's less vegetation to hold it together, this causes desertification
  • There are conflicts over water supplies
  • People move out of an area to find water
  • Farms close, causing unemployment.
  • People may suffer psychological problems.
  • dried out vegetation can be easily ignited e.g. by lightening causing wildfires
  • winds pick up dry soil, causing dust storms.
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Human Activities on Drought

Humans have made the impacts of drought worse:

  • Overgrazing reduces vegetation in an area. This makes the soil erosion caused by drought even worse-with fewer plants, the soil isn't held together as strongly so it's eroded more easily 
  • Excessive Irrigation- Irrigation is where water is artificially supplied from rivers or lakes to farmland to increase crop production. However, excessive irrigation depletes rivers and lakes, which increases the impact of drought because there's less water. Also when irrigation water evaporates, salts are left in the soil (salinisation). Crops don't grow as well in salty soil, therefore increasing the impact of drought.
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Impacts of Droughts in LEDC's

The impact of droughts are more severe in LEDC's:

  • More people in LEDCs depend on farming. If crops and livestock die lots of people will lose their livelihoods and some might starve
  • LEDCs have less money to prepare for droughts or respond to them e.g. they can't afford to build reservoirs, so the imapacts of a drought are more severe
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Case Study- Australia 2005 to 2006 drought in an M

Australia is the world's driest inhabited continent and often sufferes from droughts. The drought of 2005-06 took its toll on the lives and livelihoods of farmers as well as livestock and crops. The 2005 winter was the fourth driest for more than a century. Reservoirs emptied and there were severe water restrictions in the populated coastal areas of Queensland.

What caused the drought?

A strong El Nino effect in 2002 caused a reversal in the normal winter ocean-current patterns in the Pacific Ocean.

Normally there is warm water in the western ocean off the coast of Australia and cooler water in the east of Peru and Chile.

Strong trade winds carry moist air across the ocean and convection currents form above the warm water and result in heavy rain and thunderstorms along the Australian Coast.

Ocassionally this situation is reversed and the cooler water occurs off this stretch of coast. The trade Winds are weaker and this results in drought conditions.

El Nino- large climatic disturbances in the southern pacific ocean that occur every 3-7years.

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Case Study- Australia 2005 to 2006 drought in an M

  • crops failed meant loss of income for farmers, potential unemployment and lack of food
  • Cattle and sheep dies of starvation or thirst meaning shortage of food, loss of income or maybe unemployment for farmers
  • Bushfires cause loss of vegetation and crops, animal habitats destroyed meaning large areas of land destroyed, homes damage/destoryed, animal habitats ruined.
  • Cost of living increases because insurance increase meaning food prices and water prices increase, they have to buy more bottled water which is more expensive
  • Soil erosions dues to severe loss of vegetation due to drought meaning crops can't grow and land value decreases
  • Duststorms cause soil erosion meaning fertile soil is blown away, visibility decreases on roads.
  • Higher personal debt due to costs for damamges, farmers having to lend money, cost of living increasing
  • National debt increase due to the GDP decreasing, money spent of helping farmers, government have to spend money importing food and water
  • gardens and pars will be ruined as land will dry up meaning tourism will suffer so money will be lost
  • water quality with decline because of the formation of toxic algae
  • Health will decline due to psychological problems such as stress, dehydration, and the failure of crops causing less balanced diet.
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Case Study- Australia 2005 to 2006 drought in an M

Can Australia be drought-proofed?-Drought regulations in Queensland

  • Clean buildings and equipment at any time
  • Do not water lawn
  • Do not clean hard surfaces
  • clean vehicles at any time
  • Saturday 4-4:30 pm odd number plates on vehicles can wash cars, sunday 4-4:30pm even number plates 
  • Top up pool, tues thurs and sat4-7pm (even). Wed, Fri and Sun:4-7 (odd)
  • Water gardens any day 4-8pm
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Coping with Drought: LEDCs and MEDCs

How does drought affect LEDCs?

Each drought that occurs in the semi-arid lands of LEDCs  results in less grazing land and fewer crops in areas where there are some of the highest birth rates in the world.

Over 900 million people are affected by the process of land degradation or desertification that is occurring in areas of unreliable rainfall across the world. The main cause is the human mismanagement of a very fragile environment that was previously productive land. 

Population increase and poor agricultural practices result in the soil losing its protexctive vegetation cover. The land then becomes at risk from soil erosion as it become exposed to the wind and the occasional heavy rainstorm.

How does drought affect MEDCs?

Compared with LEDC's, the impact of droughts and people in MEDC's is relatively small.

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Coping with drought

Long term

Long term responses are those that result in permanent water management measures, whcih are designed to secure more water for everyday use. Strategies include:

  • Dams
  • Irrigation Systems-Irrigation is the artificial application of water to the land or soil. It is used to assist in the growing of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall.

In developed countries they will often carry water from areas of surplus to areas of demand. These strategies are expensive, and do not usually include any measures that will improve efficiency.

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Coping with drought 2

Short Term

Short term responses include the more temporary methods used by people to overcome specific drought events. They concentrate of reducin water demand and include water rationing, cash and/or food aid to the affected areas. These are generally less sustainable than the long term measures and do not help people to be better prepared for the next drought.

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Case Study- Australia 2005 to 2006 drought in an M

Drought Management

  • Grey Water- Tanks collect rain water to be used for cleaning cars, fishing, toliet, watering plants etc.
  • Water Recycling- Recycle water from factories, storm water. Can be recycle enough to be able to drink
  • Reducing Useage- Hose pipe ban, showers not baths, not using swimming pools etc.
  • De-salination plants- Purifys salt water from sea (removes salt)
  • Water transfer scheme- Transfer water from areas of high water levels to low water levels. Need to build dams, aquaducts, lots of piping
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Case Study- Australia 2005 to 2006 drought in an M

Future water sources for Australia

Desalination- this is a process which removes dissolved salts and other impurities from sea water or brackish water to create high quality drinking water. Reverse osmosis is the most common process for desalination and is being used ast the SEQ (gold coast0 desalination facility at Tugun. 

Cloud Seeding- This injects clouds with particles of silver iodide or dry ice to provide nuclei around which ice crystals or water droplets can condense. These will eventually fall to provide nuclei around which ice crystals or water droplets can condense. These will eventually fall to the ground as rain. The plan would be to trap the clounds coming from the Darling Downs and western Queensland and then send planes to distribute the 'seeds'

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Reducing the Impact of Drought


  • Droughts can be predicted a short time before they happen by monitoring rainfall, soil moistures and river levels
  • When a drought is predicted things can be done to reduce the impacts e.g. banning hosepipes, rationing water or moving people out of areas that will be worst affected

Water Conservation

  • People can conserve water by reducing the amount they use in their homes, e.g. by installing low volume flush toilets.
  • People can also install water butts at home to collect rainwater and use it to wash their car or water their garden
  • These reduce the demand on water supplies, so more water is avaliable during a drought

Increase Water Supplies

  • Reservoirs and wells can be built to increase water supplies
  • These make more water available during a drought, reducing deaths from dehydration, reducing conflicts over supplies and making food production more reliable
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Reducing the Impact of Drought 2


  • Aid can help reduce the impacts of drought in more than one way:
  • Emergency aid (like food or water) can stop people dying from dehydration or starvation
  • Aid can be used to fund development projects e.g. building wells or water pipes, to make more water available during droughts.

Farming Techniques

  • Drought resistant crops can be grown e.g. millet, sorghum and olives
  • More efficient methods of irrigation can be used. For example, drip irrigation delivers small volumes of water directly to crop roots reducing the amount lost by evaporation
  • These techniques reduce the demand on water supplies and make food production more reliable
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Case Study: Hurricane Katrina, USA 2005

23 August: Tropical depression forms off the south eastern Bahamas

24 August: Upgraded to tropical storm and given name Katrina

25 August: Strengthened to become a hurricane and made landfall in the morning north of Aventura in Florida

26 August: Storm intensified as it crossed the warm waters of the Gulf of Mevico reaching category 2 status

27 August: Storm has doubled in size and reaches in category 3 intensity as it crosses the gulf toward mexico.

28 August: reaches its peak strength of category 5, with maximum winds of 282 kph and a central pressure of 902mb. Turns north and approaches the US coast.

29 August: Makes its second landfall at 6:10 am at the eastern edge of New Orleans. Hurricane force winds extend outwars for 193km from the centre

30 August: Hurricaine follows the course of the Mississippi, being downgraded to a tropical depression near Clarksville, Tennessee

31 August: Remnants of the storm reach the great lakes, causing heavy rain and high winds.

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Case Study: Hurricane Katrina, USA 2005 2

Weren't there any warnings?

On 27 August the National Hurricane Center ordered a hurricane watch along the Gulf coast states of the USA. The United states coast guards began to gather resources in areas outside the expected impact zone and called up more than 400 reserve members. 

Aircraft from the aviation training centre were recalled to their base in mobile so that they could take part in rescue operations. 

President Bush declared a state of emergency in areas of Louisiana, Mississippi and Alabama on Saturday 27 August but he did not include any of Louisiana's coastal parishes.The director of the NHC expressed concern that a storm surge produced by the hurricane might over top New Orleans' levees and flood walls. On Sunday 28 August the National Weather Service issued a bulletin predicting that the New Orleans area would be 'uninhabitable for weeks' after 'devastating damage' caused by Katrina.

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Case Study: Hurricane Katrina, USA 2005 3

Primary Impacts 

  • The levees and flood wall that protected New Orleans were breached in 52 different places, allowing water to flood the city up to 3m deep
  • Flooding was made worse by the heavy rain (250mm during the storm). It is estimated that over 80% of the city was under water
  • Deaths totalled 1836- many drowned in the floodwaters and lay in the streets or floated in the water for days before their bodies were recovered. 
  •  Houses torn down- made of wood
  • Most of the roads in and out of the city were damaged and two major roads collapsed
  • Secondary Impacts 
  • Over 10,000 people were made homeless. Most of these were from the poor inner city areas of St Bernard's Parish and the lower ninth ward
  • Over 3 million people were without electricity
  • Most of the roads in and out the city were damaged and two major road bridges collapsed
  • People were stranded in the flooded city during a summer of record temperatures reaching 85 degrees Fahrenheit during the day. People struggled to get to safe havens such as the Superdome
  • There was shortage of food and no access to a clean water supply for survivors, which raised problems of contaminated water and health risks.
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Earthquakes occur at all three types of plate margin. They are caused by pressure that builds up at all three types of plate margin or by the upwelling of magma during a volcanic eruption. The plates eventually jerk past each other, sending out shock waves.

The shock waves spread out from the focus. The epicentre is the point on the Earth's surface straight above the focus. Near the epicentre the shock waves are stronger and cause more damage.

The amount of energy released by an earthquake (its magnitude) is measured using the Richter scale. The scale doesn't have an upper limit and its logarithmic (this means an earthquake with a magnitude is ten times more powerful than one with a magnitude of 4)

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Impacts of Earthquakes

Primary Impacts:

  • Buildings and bridges collapse
  • People are injured or killed by buildings and bridges collapsing
  • Roads, railways, ports and airports are damaged
  • Electricity cables are damaged, cutting off supplies
  • Gas pipes are broked, causing leaks and cutting off supplies
  • Telephone poles and cables are destroyed
  • Underground water and sewage pipes are broken, causing leaks and cutting off supplies.

Secondary Impacts:

  • Earthqaukes can trigger landslides and tsunamis- these destory more buildings and cause more injuries and deaths
  • Leaking gas can be ignited, starting fires
  • People are left homeless
  • People may suffer psychological problems if they know people who diesd or if they lose their home etc.
  • There's a shortage of clean water and a lack of proper sanitation-this makes it easier for diseases to spread.
  • Roads or blocked or destroyed so aid and emergency vehicles can't get through 
  • Businesses are damaged or destroyed causing unemployment
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Impacts of Earthquakes in LEDC

The impacts of earthquakes are more severe in LEDCs. Why:

  • There's more poor quality housing in LEDCs. Poor quality houses are less stable, so they're destroyed more easily by earthquakes.
  • The infrastructure is often poorer in LEDCs. Poor quality roads make it harder for emergency services to reach injured people, which leads to more deaths
  • LEDCs don't have much money to protect against earthquakes, e.g. by making building earthquakes proof. They also don't have enough money or resources to react straight away to earthquakes, so more people are affected by secondary impacts
  • Healthcare is often worse in LEDCs don't have enough supplies to deal with the large numbers of casualties after an earthquake, so more people die from treatable injuries.
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Why do people live in areas where earthquakes happ

  • They've always lived there- moving away would mean leaving friends and family
  • They're emploued in the area, if people move they would have to find new jobs
  • They're confident of support from their government after an earthquake, e.g. to help rebuild houses
  • Some people think that severe earthquakes won't happen again in the area, so it's safe to live there.
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Reducing the Impacts of Earthquakes


  • If you could predict earthquakes, it would give people time to evacuate- this would reduce the number of injuries and deaths
  • There can be clues that an earthquake can happen e.g. lots of small tremors, cracks appearing in rocks and strange animal behaviour (rats abandoning nests)
  • It's possible to predict  where future earthquakes may happen using data from past earthquakes, e.g. mapping where earthquakes have happened shows which places are likely to be affected.

Building Techniques 

  • Buildings can be designed to withstand earthquakes e.g. by using materials like reinforced concrete or building special foundations that absorb an earthquakes energy
  • Constructing earthquake proof buildings reduces the number of buildings destroyed by an earthquake. so fewer people will be killed, injured, made homeless and made unemployed

Aid: LEDCs that have been affected by earthquakes can receive aid from governments or organisations- it can be things like food, water, money or people  Aid helps to reduce the impacts e.g. money aid is used to rebuild homes.

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Sustainable Earthquake Strategies

Predicting earthquakes is not an effective strategy so it's not sustainable.

The other strategies above are sustainable- they're all effective and environmentally friendly, but some are more sustainable than others. 

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Effects of an Earthquake

Ground Shaking  :This is the main hazard created by earthquakes. Its severity at any one point depends upon a range of factors, including the strength of the earthquake, the distance from the epicentre and local geological conditions. The longer the shaking the more damage will be caused.

Landslides, rock and snow avalanches  :Occur in mountainous areas where slopes are weakened by strong shaking and eventually give way. Landslides blocked the roads and filled the reservoirs in the Sichuan earthquake in China in 2008 

Tsunamis  :Seismic sea waves that result when earthquakes occur beneath the sea. They can travel with enormous speed and cause devastation along the coast. The tsunami caused by in the Indian ocean earthquake in December 2005 led to a tidal wave that killed more than 200,000 people

Liquefaction: The shock waves cause groundwater to rise to the surface, turning soft ground to mud. Any building built on clay for example, sink into the mud and collapse. 

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Case Study: Sichuan, China 2009 -an earthquake in

Monday, 12th May 2009 at 2.28pm, an earthquake measuring 7.9 on the Richter scale struck the province of Sichuan in southern China. It lasted 2 minutes and killed 69,180 people.


  • 69,172 dead
  • 374,159 injured
  • 17,420 missing
  • 45.61 million affected
  • 15 million relocated
  • 5.46 million homes destroyed
  • 21.0 million homes damaged
  • 7000 schools destroyed

Agricultural Damage

  • Irrigation systems for 100,000 hectares of paddy fields wrecked.
  • >50,000 greenhouses destroyed
  • 7.3 million meters squared of livestock barns collapses

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Case Study: Sichuan, China 2009 -an earthquake in

Infrastructure Damage

  • 15,000,000 buildings collapsed
  • 5000km of pipes damaged 
  • 839 water tanks collapsed
  • 1300 water treatment works destroyed

Tangjiashan (10th June)

Soldiers were mobilized to dig a spillway for the drainage of the quake-formed lake, discharging of half of its water

Shifang 12th May

2 chemical factories destroyed, spilling 80 tons of toxic liquid ammonia

It occured on the Longmenshan Fault (the High tibetan plateau plate and Sichuan Basin) the plates were moving towards each other.

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Case Study: Sichuan, China 2009 -an earthquake in

Quake Lakes

The Sichuan earthquake caused huge landslides across the affected region. Some of these landslides fell into riverbeds and dammed the water - forming what are called "quake lakes." Quake lakes are extremely dangerous for two reasons: first, because the lake they create behind the landslide will severely flood nearby cities and farmland, and secondly because the landslide dam will usually fail after damming up a large amount of water, sending a huge wave of water downstream that will destroy anything in its path.

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Case Study: Northridge, California 1994- an earthq

Structural Damage

  • Most casualties and damage occurred in multi-storey wood frame buildings. In particular, buildings with a weak first floor performed poorly
  • The Northridge earthquake caused extensive damage to parking structures and freeway overpasses
  • The Northridge earthquake triggered landslides in surrounding mountain areas. These landslides blocked roads and damaged water lines and also damaged homes, particularly in Pacific Palisades area
  • Numerous fires were also caused by broken gas pipes damaged by houses shifting off foundations or by unsecured water heaters falling over. A fire devastated an area of trailor homes in the San Fernando Valley. Several underground gas and water mains were severed.
  • The scoreboard at Anaheim Stadium collapsed onto several hundred seats. Fortunately, the stadium was empty at the time, due to the time of day the earthquake occurred. 
  • Liquefaction occurred amongst some alluvium in the upper San Fernando Valley.

The area was declared a federal disaster by President Clinton and workers from FEMA were deployed to southern California to help the communities recover. More than 600,000 individuals applied for state and federal disaster assistance, and FEMA spent millions of federal money helping the area recover.

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Case Study: Northridge, California 1994- an earthq

Predicting and Earthquake

Researchers in 2009 predicted that Southern California was much more likely to suffer an earthquake the size of the Northridge one than Northern California by 2028. The problem is that they cannot predict when or where the earthquake will happen. 

The United States Geological Survey (USGS) have been investigating whether is it possible to predict earthquakes for over 30 years. Scientists analyse data to worko out the likelihood of fault movements in specific areas using new information about prehistoric earthquakes, location of hidden faults, and an increasing database of satellite-based GPS data of the Earth's crust movement.

The Parkfield Experiment

The town of Parkfield is located right on the San Andreas Fault. Scientists have set up instruments to record all ground shaking in the area and will use the data to attempt to understand what actually happens on the fault and in the surrounding region before, during and after an earthquake. Eventually scientists hope to better understand the earthquake process and, if possible, to provide a scientific bases for earthquake prediction.

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How Can People Prepare for Earthquakes?

  • Earthquake Proof Buildings: most deaths in cities in earthquake prone areas are caused when people are crushed inside collapsing buildings. Scientists can test how different building material survive. They can also design stronger buildings to an earthquake. Another major danger is the risk of fire from severed power lines and ruptured gas pipes (as seen in the Northridge case study). When buildings are constructed they can provide more flexible pipes to cut down this risk.
  • Education: government agencies and the media provide extensive guidance in earthquake prone areas to help people prepare for the period before, during and after a tremor. In the USA this is available on the internet: Earthquake Information from the USGS. In Japan, 1 September in Disaster Day, the anniversary of the devastating Tokyo earthquake of 1923 that killed 155,000 people. The day is a public holiday when Japanese people practice earthquake drill.
  • Emergency Services: governments must plan carefully to make sure that the emergency services are prepared for possible earthquakes and that relief supplies are ready. If an earthquake is detected as soon as it starts, then better precautions can be taken: for example, power stations can be shut down so that there is less danger of fires from ruptured power lines, hospital generators started, and the emergency services can be alerted. Good communication with earthquake monitoring stations can also save lives. Predicting earthquakes can be expensive, because lots of special scientific equipment is needed. Poorer countries and regions will not be able to afford such equipment.
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Can Earthquakes be Predicted?

If scientists can predict when and where an earthquake will happen, people can be warned and lives could be saved, so scientists monitor active zones.

  • Sensitive instruments measure earth movements and check the stress building up in rocks. Maps can then be produced of the probability of earthquakes occurring. They can also use instruments to give early warning of tsunamis. 
  • Several Earthquakes can occur in a short space of time. Foreshocks occur before some large earthquakes, so scientists can predict the chances of a major shock following.
  • The number of recent earthquakes can be plotted to show of a major earthquake can be expected.

If a prediction is wrong then there can be consequences. Many people cannot afford to stop working, even for a few days. In 1986, 56,000 people were evacuated from the towns of Lucca and Modena in Italy. Shops and businesses closed for two days. No earthquake happened and local people were angry about the loss of business and the inconvenience of the evacuation. The mayor was forced to resign.

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Does It Matter How Rich You Are?

In developing world countries, many people still live in rural areas. Even in those countries that are experiencing rapid economic growth, it is often the people who live in the countryside that are the last to see the benefits of increased wealth. This is often particularly so for remote or inaccessible rural regions. The Sichuan area of China has been largely neglected and untouched by China's economic rise and there is a widening gap between the prosperous urban dweller and struggling rural people. Additional problems brought by inaccessible locations include:

  • Villages are built in precarious locations that suffer badly in earthquakes. In the Afghanistan earthquake of 1998, 25 villages were completely destroyed.
  • The scale of damage to villages and the number of casualties is often not known for several days
  • Local health care is poor
  • People often have little or no health insurance
  • Water supply and sanitation is often poor and there is a great risk of disease after the event
  • The majority of the buildings are poorly constructed and do not stand up to strong shaking
  • Damage is often worsened by other events such as landslides, which hinder rescue attempts and cause damming of rivers.
  • Relief can take days to arrive and desperate survivors take matters into their own hands. Widespread looting of homes and shops can occur.
  • There are often no accurate maps of the area to help rescuers locate settlements and other areas where survivors might be.
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Does It Matter How Rich You Are? 2

  • There often no plans for dealing with the impacts of the earthquake and people are not well prepared.

Buying Protection?

In more developed countries people are more prepared for an earthquake and they know what to do when one occurs.  The major economic impacts of earthquakes result from damage to buildings and to the infrastructure that are essential to the operation of the economic activities in the affected areas. Infrastructure systems are extremely vulnerable and their failure can result in delays in rescuing survivors as well as in restoring quality of life for those affected.

Many businesses will have been dependent on transport and communications for workers, customers, supplies shipment, water electricity, gas, telephone and other services. Some areas such as ports are particularly vulnerable because they are located next to harbours, often built on soft soils and land fill. Major ports are centre of commerce and handle regional and international trade. They are linked with other sectors such as transport, finance, banking and insurance. Some businesses will even find an increase in their activity because of demands placed on them by the disaster. Businesses that may benefit are ones for which there is an increased demand for their products or services for relief, clearing and removing debris, repair and restoration, and reconstruction. However, all these activities have a cost and economically developing countries will find it difficult to fund such a large-scale development.

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Mr A Gibson

48 cards rammed with information - get these on your mobile device if you want or print them out to help you prepare thoroughly for this topic.

FilthyFrank-chin chin realm

Who knows how to install mods on minecraft?

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