global hazards ed excel as revision

8/6/2019 Global Hazards Ed Excel as Revision

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Unit 1: World at RiskGlobal hazards

Name: Toby Butterworth

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Geography @ Okehampton Collegewww.greatgeography.blogspot.com

Geography Department now available on
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Keywords

Context hazard: Widespread (global) threat due to environmental factors such asclimate changeGeophysical hazard: A hazard formed by tectonic/geological processes(earthquakes, volcanoes and tsunamis)Hazard: A perceived natural event which has the potential to threaten both life andpropertyHydro-meteorological hazard: A hazard formed by hydrological (floods) andatmospheric (storms and droughts) processesVulnerability: A high risk combined with an inability of individuals and communitiesof copeDisaster: A hazard becoming reality in an event that causes deaths and damage togoods/property and the environmentRisk: The probability of a hazard event occurring and creating loss of lives andlivelihoodsAlbedo: How much solar radiation a surface reflectsClimate change: Any long term trend or shift in climate (average weather over 30

years) detected by a sustained shift in the average value for any climatic element(e.g. rainfall, drought, storminess)Enhanced greenhouse effect: This occurs when the levels of greenhouse gases inthe atmosphere increase owing to human activity.Fossil fuels: Energy sources that are rich in carbon and which release carbon dioxidewhen burnt (eg coal)Global warming: A recently measured rise in the average surface temperature ofthe planetGreenhouse effect: The warming of the Earths atmosphere due to the trapping ofheat that would otherwise be radiated back into space it enabled the survival of lifeon Earth.

Tipping point: The point at which a system switches from one state to anotherFeedback mechanism: Where the output of a system acts to amplify (positive) orreduce (negative) further output (e.g. the melting of Arctic permafrost leads to therelease of trapped methane which leads to further global warming)Frequency: How often an event of a certain size (magnitude) occurs.Magnitude: The size of the event (e.g. size of an earthquake on the Richter Scale)Asthenosphere: A semi-molten zone of rock underlying the Earths crustConservative boundary: A boundary between plates where the movement of theplates is parallel to the plate margin and the plates slide past each other.Constructive boundary: A boundary between plates where the plates are diverging

or moving apartDestructive boundary: A boundary between plates where the plates are converging(moving together)Lithosphere: The crust of the Earth, around 80-90km thickMagma: Molten material that rises towards the Earths surface when hotspots withinthe asthenosphere generate convection currentsNatural hazard: a natural event or process which affects people eg causing loss of lifeor injury, economic damage, disruption to peoples lives or environmental degradationPlates: Rigid, less dense slabs of rock floating on the asthenosphereHotspot: A localised area of the Earths crust with an unusually high temperaturePlume: An upwelling of abnormally hot rock within the Earths mantle

Inter-tropical convergence zone: A zone of low atmospheric pressure near theequator. This migrates seasonally.

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The nature of hazardA natural event such as a tsunami only becomes a hazard if it threatens humans.

There are many different types of hazard. Environmental hazards are specific eventslike earthquakes or floods, usually classified into

Natural processes: where the hazard results from an extreme geophysical orhydro-meteorological event, such as a flood or volcanic eruption

Natural-technological disasters: where natural hazards trigger technologicaldisaster (e.g. flooding causes a dam to burst)

Technological accidents: such as Chernobyl nuclear power plant explodingEnvironmental hazards are related in varying degrees to context hazards whichoperate at a global or continental scale.

Chronic hazards such as globalwarming and the El Nino-La Ninacycle may increase the threatfrom environmental hazards; forexample, a sea level riseincreases the risk of coastal

floods.

Some key features of environmental hazards makethem a huge threat:

The warning time is normally short and onset is rapid (apart from droughts)

Humans are exposed to hazards because people live in hazardous areasthrough perceived economic advantage or over-confidence about safety.

Most direct losses to life or property occur within days or weeks of the event,unless there is a secondary hazard.

The resulting disaster often justifies an emergency response, sometimes on thescale of international humanitarian aid.

Some socioeconomic characteristics, such as a high population density, high povertylevel or corrupt and inefficient government increase peoples vulnerability and amplifythe risks, particularly of death,from environmental hazards.

Types of natural hazard Geophysical hazards

result from geological or

geomorphologicalprocesses (e.g.volcanoes, earthquakesand tsunamis). Theseare of two types,internal earth processesof tectonic origin (e.g.earthquakes, tsunamiand volcanic activity)and external earthprocesses of

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geomorphological origin involving mass movements (e.g. landslides, rockslides,rock falls)

Hydro-meteorological hazards result from atmospheric or hydrological processes(eg floods, storms and droughts). Hydro-meteorological hazards are thosecaused by running water and its processes (hydro) and those associated with orcaused by weather patterns (meteorological). They include floods, debris andmud flows, hurricanes, coastal storm surges, thunder and hailstorms, rain andwind storms (including tornadoes), blizzards and other severe storms, drought,bushfires, temperature extremes, sand and dust storms.

What are disasters?When does a natural hazard become adisaster?Dreggs model of defining disasters showshow some kind of overlap is required beforea hazard becomes a disaster. A disaster isa matter of scale; it is simply bigger than anatural hazard. However, it is difficult to

define precisely. Insurance companies who do a lot of research into global hazards attempt to define disasters. In 1990,Swiss Re defined a disaster as an event inwhich at least 20 people died, or insured damage of over US$16 million value wascaused.

Disasters and vulnerable populationsWhether a hazard becomes a disaster or not can depend on how vulnerable thepeople who are exposed to it are. An increasing proportion of the worlds populationlives in areas which are exposed to hazards. Examples include:

People in Bangladesh who are threatened by floods and cyclones

People who live on steep slopes where landslides may be common, such as thefavelas (shanty towns) in many Brazilian cities.

Who studies hazards?People study hazards from different perspectives, such as:

Scientists, e.g. geomorphologists (who study landform processes), geologists(rocks) and hydrologists (water)

Those who study societies e.g. economists, sociologists and psychologists

Applied scientists e.g. civil, structural and hydrological engineers

Private companies e.g. insurers Public bodes e.g. national and local governments

Cultural organisations and individuals e.g. writers, photographers and evenmusicians

Investigating the worlds worst hazardsWhich are the worlds worst hazards? The answer depends on the year, 2004-5 wasbad for disasters, beginning just before the new year with the 2004 Boxing Daytsunami. Between December 2004 and December 2005, 300 000 deaths occurredglobally one of the worst 12 months on record. On average, 77 000 people were

killed annually in natural disasters between 2000 and 2005, although that figure islower if the 2004 tsunami is removed from the calculation. Care should be taken

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when comparing years directly, because the total number of deaths can be hugelyaffected by a single major disaster like this. Most deaths from disasters occur in Asia.

Which hazards have the worst impacts?Floods and windstorms may be greatest in number, but do they cause the mostdeaths or create the most damage? The data are complex but patterns do stand out:

Earthquakes cause occasional major damage, but there is no upward trend.

Damaging floods are increasing, but not consistently so Damaging windstorms are also increasing, though again not always

consistently.

Why are floods and windstorms increasing?The media almost always say that it is due to global warming. The theory is that the

Increased warming of the earth causes warm air to rise, creating convectioncells which form hurricanes

Increasing temperatures increase evaporation, which in turn leads to increasingrainfall and therefore greater flooding.

Or is this part of a natural cycle? Research shows that the Atlantic Ocean wheremany windstorms begin appear to work in a cycle of peaks and troughs. The periodaround 1930-1935 showed increased storm activity, with major falls and increasesoccurring in cycles since then. So, although there has been an increase in hurricaneactivity since the mid 1990s, there were previous increases in the 1950s and 1970s.

How significant are natural hazards?There are no data for deaths from hazard events globally, only for those events whichare large enough to be called disasters. Although numbers vary considerably fromyear to year, on average fewer than 100 000 deaths are recorded each year from

natural disasters worldwide. This is: 30 times fewer than the number who die from HIV/AIDS

35 times fewer than the number of road deaths

50 times fewer than the number of smoking-related deaths

The risk of disasterA hazard event can become a disaster, especially when it occurs in areas whereenvironments and people are vulnerable. The types of risk from global hazards are:Hazards to people death and severe injury, disease, stressHazards to goods economic losses, infrastructure damage and property damageHazards to the environment pollution, loss of flora and fauna, loss of amenity

Why do people remain exposed to hazards?Changing risks: It is difficult to predict when or where an event may occur or whatthe magnitude will be. Natural hazards vary in space as well as time because ofchanging human activities and changing physical factors, such as tectonic platemovements. The rise in sea level means that low-lying coastal plains that were oncesafe places to live are now more prone to storm surge and flood. Deforestation ofwatersheds leads to less interception of rain and more flashy hydrographs, increasingthe frequency and magnitude of flood events.Lack of alternatives: Often the worlds poorest, most vulnerable people are forced

to live in unsafe locations such as hillsides or floodplains, or regions subject todrought, owing to shortage of land or lack of knowledge or better alternatives.

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happen without warning, unlike cyclones, which can be monitored and to some extentpredicted and planned for.

Investigating the risk equation further, it is apparent that not all of the earthsinhabitants are at equal risk from natural hazards. For example, whilst theoretically itis possible for nearly any location on earth to experience an earthquake, they arelikely to be far more powerful in places that are located at or near the boundaries ofthe tectonic plates. The chances are that people who live along plate boundarieswould be far more likely to experience an earthquake of a large magnitude than thosewho do not. In effect, this makes these people and their communities morevulnerable (V) to earthquakes.

The concept of vulnerability is quite easy to extend to other hazards; if you do not livein close proximity to a volcano, then you are not likely to be threatened by lava flows.However, that is not to say that your location may not be affected by clouds ofvolcanic ash, which can significantly alter the climate of places many miles, evencontinents, away from their point of origin. It is important to note that vulnerabilitycan also be increased by other factors such as poverty.

Capacity (C) refers to the ability of a community to absorb, and ultimately recoverfrom, the effects of a natural hazard. We have already noted that people in Japanincrease their capacity to cope with the effects of an earthquake by regularlypractising how to respond to a major quake. In theory, this will mean that theircommunity will have a better chance of coping with a large earthquake than if theyhad not practised these procedures. Compare this to the capacity to cope thatcurrently exists in a sprawling slum in the less developed world, where dwellings havebeen hastily constructed from poor quality materials, and where there is neither thetime nor resources to commit to a large-scale community training programme. Theeffects of this lower capacity increase the risk that this community faces from these

hazards.

As our knowledge of natural hazards has steadily grown, so too has our preparednessfor these events and our ability to cope with, and recover from, them. That said, therisk equation shows us that millions of people are still at the mercy of the naturalenvironment, and that their ability to survive is largely determined by factors that arebeyond their control.

Frequency or magnitude of hazard is increasingUse of fossil fuels is warming the planet. The resulting change in climate is increasing

the frequency and severity of weather-related hazards (e.g. floods, droughts,windstorms) and expanding the range of disease carriers.

It is clear that the number of reported natural disasters is increasing with eachpassing year. Some argue that this is due to improvements in technology that alloweven the smaller-scale and more isolated disasters to be recorded. Others suggestthat with international monitoring agencies like the Belgium-based Centre forResearch on the Epidemiology of Disasters (CRED) in operation, people areencouraged to report the occurrence of natural hazards more than in the past thusthe numbers go up because of better recording rather than any other trend.

Decreasing numbers of deathsWhat is interesting about the increase in the reported number of natural disasters isthe fact that there has been a decrease in the number of reported deaths due to

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these disasters. During the period from 1900 to 1940, approximately 500,000 peoplewere reported to have been killed by natural disasters each year. After 1940,however, this annual death toll rapidly decreased, to the point where in the early partof this century, the number of people killed by natural disasters each year is less than50,000.

This falling toll due to natural hazards reflects the ability of humankind to understandnatural hazards better, including improvements in our ability to predict theiroccurrence and to take the appropriate precautions (such as evacuation). For thoseliving in the developed world, this knowledge also encourages the construction ofhouses that are more likely to withstand the effects of most natural disasters. Sadly,this is not always the case in the less developed world.

Increasing numbers of people affected and economic costsWhile fewer people die each year as a result of natural hazards, these events areaffecting more people than ever before. At the same time, they are taking a greatereconomic toll than in the past. Since 1980, the average annual economic cost ofnatural hazards has risen from less than $20 billion to more than $160 billion. In the

same period, the number of people reported as being affected has risen from anannual average of 100 million to more than 200 million.

The year 2005, in which Hurricane Katrina struck the Gulf Coast of the USA, wasclearly an above average year. In 2005, the number of people who were reported tobe affected by natural disasters was more than 650 million.

CapacityThere is an increase in our capacity to cope with disaster. Logic would say that inmodern times we should be less at risk from natural hazards, because we haveincreased our capacity to understand and manage the effects of disasters. Disaster

warning systems and emergency responses are better now than at any stage inhuman history. The preparedness of governments to respond appropriately in theface of crises has improved dramatically in the last few decades, with the globalcommunity being able to provide relief within hours. Scientists and engineers haveprovided us with the latest in disaster-proof building materials and governments haveincreasingly strengthened building regulations through appropriate codes ofconstruction in disaster-prone areas.

VulnerabilityWe are experiencing a simultaneous increase in our vulnerability to natural hazards.

While there have been improvements in our capacity, in the later half of the 20th

century, we have significantly increased our vulnerability to natural hazards through acombination of economic, social-demographic and technological factors. Thesefactors far outweigh the gains made in terms of capacity.

Economic factors of vulnerability: exploitation of natural resourcesAs we continue to degrade our environment by exploiting natural resources in pursuitof economic progress, we are making ourselves more vulnerable to natural hazards.Changes that humans make to the physical environment remove many of the naturalbuffers that exist between our communities and natural hazards. Clearing ofvegetation from hillsides or sloping land, in order to allow for development, is a well-

recognised example. Although this practice is known to increase the risk oflandslides, it continues to be carried out in a variety of global settings to create moreuseable land for agriculture or in the pursuit of profits from forestry. In a similar way,

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the draining and filling of wetlands to create land for housing or industry is equallyrisky. This practice can significantly alter drainage patterns within this naturalenvironment and expose the new development to flooding.

Socio-demographic factors of vulnerability: population growth andurbanisation

The rapid growth of the human population has meant that there are more people onthe planet, and therefore a greater number of people at potential risk from naturalhazards. Urbanisation has also continued at a great pace. More of us now live inurban areas than ever before. Additionally, most urban centres are located in coastalareas, and these are the parts of the world which are most exposed to the hydro-meteorological hazards such as cyclones for floods.

The net result of urbanisation is the concentration of people and infrastructure. Eventhough natural hazards have a low probability of occurring, when they strike in highlyurbanised areas, they do so with a high cost. The greatest economic cost of a naturaldisaster clearly lies in replacing lost infrastructure. The hidden costs of a disaster canalso include the cost of taxpayer-funded disaster relief programmes, tax breaks to

assist communities to rebuild, and the inevitable increase in the price of goods andservices as businesses re-establish themselves after a disaster.

As the need for more land for urban centres has continued to grow, the opening up ofmarginal areas which are at higher risk of natural hazards, such as floods hasoccurred. Insurers have responded by charging higher premiums to those whooccupy these areas. Whilst this seems appropriate in the developed world, there areno such guarantees of overage in the less developed parts of the world.

An ageing populationIn a demographic sense, the ageing population of the developed world has, in effect,

made our communities more susceptible to natural hazards. Older people (65+) arethe least mobile in a community and have less capacity to take action either before orafter a natural disaster. In an interesting contrast, it is the mobility of the rest of thepopulation who are now freer to move between locations for work or family reasonsthat at any other stage in human history that has broken down what demographersrefer to as our community memory. In the past, when people were less mobile,communities built up a strong local knowledge about natural hazards and their likelyeffect on local places. This was an effective reminder to people about the places thatwere worst affected by natural hazards and helped to prevent, or at least discourage,development in the riskier parts of the local environment. Sadly, with our increased

mobility during our working lifetimes, this community memory has diminished.

Technological factors of vulnerability: dependence on technologyHow has development been allowed to take place in areas that are in effect moreexposed to the risks associated with natural hazards? Our belief that we are able topredict and control the natural environment and its processes are partly responsible.

This belief has led us to develop areas for human habitation which previously may nothave been considered safe or viable. We have developed a reliance on technology forour salvation from the hazards of the natural world. This includes the early warningdetection systems that allow us to prepare for the onset of a natural hazard, such as acyclone, flood, tsunami or earthquake. It also includes physical barriers, such as levee

banks and flood control systems that help to contain or divert floodwaters away frommajor urban centres. A flood control network is used on the River Thames to protect

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London. This has helped the city to expand and develop to a tremendous size,despite the fact that much of it rests on the flood plain of one of Britains main rivers.

We are more dependent now on our systems of water, power, communication andtransport than ever before. When these systems collapse under the onslaught of anatural hazard, we are unable to fend for ourselves, Many of us would struggle tocope with a power cut for a few hours, let alone for the days or weeks that mightfollow a severe natural disaster. Even the infrastructure designed to protect us fromnatural hazards can in effect make us more vulnerable, especially if it ages and is notreplaced. Worse still, it may not be designed to withstand the intensity of the hazardthat we might experience. Of course, this will not be evident until it is too late, aswhen Hurricane Katrina struck New Orleans in 2005.

Level of vulnerability is increasingHazards become disasters only when people get in the way. Unsustainabledevelopment involves poor land use (e.g. building on floodplains, unstable slopes andcoasts) and environmental degradation (e.g. bleaching of coral reefs, destruction ofcoastal mangroves, deforestation of water catchments). This is increasing the

vulnerability of millions of people.

Capacity to cope is decreasingCommunities need skills, tools and money to cope with the effects of climate change.However, debt repayments, unfair trade arrangements, selective foreign investment,and rich countries directing aid funds towards politically strategic regions rather thanthe most needy mean that the poorest and most vulnerable communities lack theseresources. Rural-urban migration is also undermining traditional coping strategies.

The futureThe most affected areas will be the poorest countries and communities in the world,

particularly in sub-Saharan Africa, parts of south-east Asia, and many of the smallisland developing states. The future risk equation emphasises how the developmentgap between rich and poor countries is actually widening.

Hazard trendsThe term hazard and disaster are often used interchangeably, in spite of therebeing a clear distinction between a hazard as a potentially threatening event, and adisaster as the realisation of a hazard event.

How good are disaster statistics?

Disaster statistics are reported by governments to UN agencies. They are only asgood as the methods used to collect them. There are several reasons to question thedata obtained:

There is no universally agreed numerical threshold for designating an event as adisaster, such as 25 or 100 deaths, or 1% of the population affected, or 1% ofannual GDP lost, or a combination of these.

Reporting of disaster death numbers depends on whether direct (primary)deaths only or indirect (secondary) deaths from subsequent hazards orassociated diseases are counted.

Location is significant. Events in remote places away from the media spotlightare frequently under-recorded. Around 10% of all data from the last 10 years

are missing.

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Declaration of disaster deaths and casualties may be subject to politicalinfluences. The impact of the 2004 tsunami in Myanmar (Burma) was ignoredby its government, but in Thailand, where many foreign tourists were killed, theimpact was initially overstated and then played down to conserve the Thaitourist industry.

Statistics on major disasters are complex to collect, especially in remote ruralareas of developing countries or densely populated squatter settlements where

statistics on population are inaccurate. Time-trend analysis, which involves interpreting historical data to produce

trends, can be difficult. Much depends on the intervals selected and whetherthe means of data collection have remained constant. Trends can be upset by acluster of mega disasters, as in 2005-2006.

Analysis of hazard trendsIn a globalised world more disasters will be reported as a result of improved access toinformation technology. Equally, with a world population of over 6 billion and rising,there will be increasing numbers of vulnerable people living in poverty, especially inAfrica. However, these facts alone do not account for the rising trends. The

occurrence of hydro-meteorological hazards has increased dramatically since the1960s, with a knock-on effect on the overall rising trend. In contrast, the number ofgeophysical disasters (earthquakes, volcanoes and tsunamis) shows fluctuations(known as timescale variations) but no overall rising trend.

Magnitude and frequencyMagnitude is the size of a natural hazard event so represents the amount of workdone (eg the energy given off during a volcanic eruption). Magnitude scalescategorise events according to size/energy and enable people to understand theprocesses and to model the likely impacts. Scales include:

Hurricanes: Saffir-Simpson scale (1-5) Earthquakes: Richer Scale (1-10 log scale)

Tornadoes: TORRO or Fujita intensity scales

Volcanic eruptions: explosivity indexLower magnitude events, such as an earth tremor of Richter Scale 2.5, have lessimpact on people than high-magnitude events, such as the earthquake which causedthe 2004 south Asia tsunami, measuring 9.1 on the Richter Scale.

Frequency s the number of events of a given magnitude hat occur over a period oftime. Low magnitude events are likely to have a more frequency recurrence level,and therefore to present more frequent but less devastating risks.

Contrasting trendsFor geophysical hazards, the variations over time can be accounted for by theclustering of events along mobile (usually destructive) plate boundaries. There havebeen a number of earthquakes off the coast of Indonesia, where the Indian plate isbeing subducted beneath the Burma plate. Other mobile active zones include Iranand Turkey. However, there is no solid evidence that the frequency or magnitude ofearthquakes or volcanic eruptions is increasing. Nevertheless, geophysical activityremains a huge killer.

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In

contrast, the number of reported hydro-meteorological events is definitely on theincrease. This is likely to be associated with climate change. It is predicted thatglobal warming will increase the frequency, magnitude and impact of hydro-meteorological disasters. Another explanation of the increased frequency of suchdisasters lies in the context hazard of increased environmental degradation caused bypopulation pressure. Deforestation and other loss of land cover, for example, aspeople cut down trees for firewood or clear forest to grow crops, can lead to flashflooding. Ecosystems undamaged by human impact provide protection againstnatural disasters (e.g. mangroves protect coasts against tsunamis). We cannot besure that damage to the environment causes disasters, but it is clear that it makesthe impacts of natural hazards worse. Short term fluctuations in climate caused by ElNino Southern Oscillation also have an impact on hydro-meteorological disasters.

Human factors in disastersPhysical factors such as ENSO contribute to the growth in hazards, but humanbehaviour plays a part too because it leads to increased vulnerability.

Rapid population growthGrowing world population means

Pressure on land which leads to people living in high risk areas, such as low-lying flood-prone land in Bangladesh

Growing numbers of very elderly people, e.g. there are concerns about thevulnerable elderly in hazardous areas of the world such as Japan (prone toearthquakes) and Florida (hurricanes)

A growing proportion of the very young in developing countries who are alsovulnerable in the event of a disaster

Deforestation and land degradationPressure on land from growing populations also leads to:

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Pressure on land to gain farmland, which can cause flooding and soil erosionand contributes to climate change.

Destruction of mangroves as coastal areas are developed, which leads tocoastal erosion and flooding

Farming in marginal areas and deforestation for firewood, which leads todesertification

UrbanisationRural-urban migration and rapid uncontrolled growth of cities lead to:

The development of squatter settlements on areas at risk of landslides orflooding

Informal housing like this is also vulnerable to earthquakes.

Poverty and politicsDisasters tend to have a greater impact in poorer countries:

Earthquakes have much higher death tolls in less developed countries whichcannot afford the technology to build earthquake proof buildings

Developing countries may not be able to afford to prepare for emergencies (egBangladesh relies on foreign aid to provide flood and cyclone shelters)

If populations are poorly educated and have little access to communicationstechnology it is harder to prepare them for disasters

It is difficult to get aid to remote areas with poor infrastructure such as roadsand bridges

Corrupt governments may misuse resources, making disasters worse or preventinternational aid reaching their populations

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Trends in human costs of disastersReported deaths

The number of people reported killed by disasters fell dramatically in the 20th century

because better prediction techniques and protection measures were developed. Thedeath rate has levelled off in recent years in spite of better disaster management.

This is largely because of increasing numbers of hydrometeorological hazards eventswhich became disasters. There is a fluctuating but steady rate of around 25,000-40,000 deaths per year. However, some years are exceptions. Several hugedisasters made 2004-05 unforgettable, the south Asia tsunami which killed anestimates 250,000, two record hurricane seasons, and the Kashmir earthquake whichclaimed 75,000 lives.

Number of people affectedThe number of people affected by hazards and disasters shows an overall rising trendsince 1991. Being affected means surviving the disaster but losing your home, cropsand animals, livelihood or health for a designated period. On average, 188 millionpeople per year are affected by disasters six times as many as are affected annuallyby conflicts.

There is a clear relationship between the numbers affected and the level of social andeconomic development in a country. The vast majority of people affected are indeveloping and least developed countries.

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Economic lossesEconomic losses from disasters have grown exponentially, nearly tripling between1980-89 and 1990-99. This is far greater rate than the growth in the number ofdisasters. Insured losses have increased less dramatically than total economic losses.It is far too simple to say that developing countries suffer the greatest number ofdeaths and developed countries the greatest economic impact of disasters. Theeconomic losses appear greater in richer countries because of the value of their

economies and the cost of making good the damage. For example, the insurancecosts of repairing a house damaged by flood in the UK may be great, but inBangladesh it is not uncommon for people to lose their crops, houses, and all theirpossessions in a flood, none of which will have been insured. Many developingcountries depend on cash crops or tourism for their income, and both of these can bedevastated by a natural disaster. Economic losses in poorer countries may be smallerin actual figures but far greater as a proportion of their annual GDP. Economic lossesare increasing faster than a number of disasters, larges because of the growingeconomies of many recently and newly industrialised countries, especially in Asia.

Global disaster trends: a summary

Natural disasters are more common in countries with a low and medium level ofdevelopment. Many of these countries are in tropical areas which have monsoonrainfall or hurricanes. Disasters cause more death and disruption in poor countries,

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which lack the resources and funds to develop high-tech prevention and predictionsystems. Damage in absolute economic terms remains highest in high-incomecountries but in relative terms it is much more devastating for poorer countries.

Global hazard patterns

The distribution of geophysical hazards The three main geophysical hazards are earthquakes, volcanoes and tsunamis.Knowledge of plate tectonics is fundamental to understanding the occurrence ofgeophysical hazards.

EarthquakesThe main earthquake zones are clustered along plate boundaries. The most powerfulearthquakes are associated with destructive and conservative boundaries.

Plate tectonics

According to plate tectonics theory the lithosphere or Earths crust is dividedinto seven major sections or plates, and a number of smaller ones. Some platesare oceanic (e.g. the Pacific plate), others continental. These plates float on theunderlying semi-molten mantle known as the asthenosphere. There are threemajor types of plate boundary constructive, destructive and conservative each of which has particular geophysical hazards associated with it.

Hotspots from within the asthenosphere generate thermal convection currentswhich cause magma (molten material) to ruse towards the Earths surface. Thiscontinuous process forms new crust along the line of constructive boundaries,where the plates are diverging.

At the same time, older crust being destroyed at destructive boundaries, whereplates converge. The type of activity here depends on whether both plates arecontinental, both plates are oceanic or an oceanic plate is being subducted ordragged down beneath a lighter continental plate.

At conservative boundaries, two plates slide past each other and there is nocreation or destruction of crust.

The type of movement and the degree of activity at the plate margins almosttotally controls the distribution, frequency and magnitude of earthquakes andvolcanic eruptions.

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Destructive plate boundaries

Destructive boundaries where oceanic crust is being subducted beneath acontinental plate, or where two oceanic plates collide, produce a full range ofearthquake types (shallow, intermediate and deep). The force of compressionas the plates meet causes stresses in the crust, and when the pressure is

suddenly released, the ground surface immediately above shakes violently. The point at which pressure release occurs within the crust is known as the

earthquake focus, and the point immediately above that at the Earths surfaceis the epicentre.

At the destructive boundaries where two continental plates are colliding toproduce fold mountains shallow, highly damaging earthquakes occur. Thesepresent a hazard risk over a wide area in countries such as India and Iran.

Constructive plate boundariesConstructive plate boundaries (where oceanic plates are moving apart) are associated

with large numbers of shallow, low magnitude earthquakes as magma rises. Most aresubmarine (except in places like Iceland) and so pose little hazard to people.

Conservative plate boundariesConservative boundaries, where there is lateral crust movement, produce frequentshallow earthquakes, sometimes of high magnitude: for example, along the SanAndreas fault system of the western USA.

Other earthquakesA small minority of earthquakes occur within plates, usually involving the reactivationof ancient fault lines. Occasionally, earthquakes can result from human actions such

as dam and reservoir building, which increase the weight and therefore stress on theland. These occur where there is no record of earthquakes.

Earthquake hazards

Primary hazards result from ground movement and ground shaking. Surfaceseismic waves can cause buildings and other infrastructure (e.g. pipes for waterand gas supply) to collapse.

Secondary hazards include soil liquefaction, landslides, avalanches, tsunamisand exposure to adverse weather. These can add significantly to the death toll.

Most of the injuries and deaths that occur in an earthquake are a result of peoplebeing hit by falling roofs or being trapped in collapsed buildings. In the moredeveloped world, and especially those parts that are prone to earthquakes, buildings

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may be designed and engineered to withstand the vibrations of an earthquake. Sadly,in less developed parts of the world, where buildings may be less rigidly constructedor made from cheaper, readily available materials (including mud, bricks or stone),the death toll from earthquakes can be significantly higher.

Volcanic eruptionsThe worlds active volcanoes are found in three tectonics situations: at constructiveand destructive plate boundaries, and at hotspots. The type of tectonic situationdetermines the composition of the magma and therefore the degree of explosivity ofthe eruption, which is a key factor in the degree of hazard risk. Hazard risk can comefrom dormant volcanoes which have not erupted in living memory (e.g. Mt St Helens).

The materials ejected from volcanoes can include magma (molten rock, which whenexposed above ground, is referred to as lava), volcanic gases (such as hydrogensulphide), ash and dust. An active volcano is one which is in the process of eruptingor showing signs that an eruption is imminent.

The rocks that are extruded from volcanoes tend to be rich in minerals and nutrients,

and are highly sought after by miners and farmers alike. This in part explains why throughout history so many settlements have been built next to or near volcanoes.Even in this modern age, this trend continues. Around the Bay of Naples in Italy, 3million people live within 20km radius of Vesuvius, one of Europes most notoriousvolcanoes. It is also important to bear in mind that lava flows actually help to createnew land. The small island of Iceland, in the Northern Atlantic, was created byvolcanic activity, and continues to grow in size as the years pass. Today, Iceland ishome to almost 300,000 people, who live alongside the islands volcanoes.

Constructive plate boundaries

Most of the magma that reaches the Earths surface wells up at oceanic ridges suchas the mid-Atlantic. These volcanoes are mostly on the sea floor and do not representa major hazard to people except where they emerge above sea level to form islands

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such as Iceland. Rift valleys occur where the continental crust is being stretched.The East African rift valley has a line of 14 active volcanoes, some of which canreduce dangerous eruptions (Mt Nyragongo in DR of Congo, 2002).

Destructive plate boundariesSome 80% of the worlds active volcanoes occur along destructive boundaries.Soufriere Hills in Montserrat, West Indies is an example of a volcano formed wheretwo ocean plates collide. When oceanic plates are subducted beneath continentalplates, explosive volcanoes such as Mt St Helens are formed. The ring of fire aroundthe Pacific has many such volcanoes.

HotspotsHotspots are localised areas of the lithosphere which have an unusually high heatflow, and where magma rises to the surface as a plume. Hawaii is an example. As alithosphere plate moves over the hotspot, a chain of volcanoes is created.

Volcanic hazardsApart from the local impacts of lava flows the most catastrophic impacts of volcanoes

are pyroclastic flows, ash falls, tsunamis and mudflows.

The distribution of slidesSlides include a variety of rapid mass movements, such as rock slides, debris flows,snow avalanches, and rainfall, and earthquake induced landslides.

Landslides

Landslides are the seventh biggest killer with over 1,400 deaths per year,ranking above both volcanoes and drought. Most areas affected aremountainous, and experience landslides after abnormally heavy rain and/or

seismic activity.

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Human factors also play a part. Deforestation of hillsides in southeast Asia andbuilding on hill slopes in Hong Kong have both led to widespread slides followingrain.

We associate landslides with high rainfall areas such as those located within theearths tropics. Here, where hurricanes and monsoons can dump large amountsof rainfall in a matter of hours, soil can very quickly become saturated.

Snow avalanches Snow avalanches are concentrated in high mountainous areas such as the

Southern Alps of New Zealand or the Rockies of North America. Avalanchestend to occur on slopes steeper than 35.

An average of 40 deaths a year in Europe and over 100 in North America arecaused by avalanches. Recent research has suggested that global warmingmay be increasing avalanche occurrence, although trends in deaths haveslowed because of effective management.

The distribution of hydro-meteorological hazards These extreme weather hazards are widespread in their distribution, growing in

frequency and increasingly unpredictable in their locations.

DroughtDrought has a dispersed pattern over one-third of the worlds land surface has somelevel of drought exposure. This includes 70% of the worlds people and agriculturalvalue, which means that drought has an effect on global food security.

A

drought is an extended period of lower than average precipitation which causes watershortage. Droughts can extend for as little as one year, during which the rainfall thatis received is noticeably lower than in average years. More often, however, a droughtis a dry period that extends over two or more growing seasons for years. Droughtscan be localised, occurring in relatively small regions (approximately the size of acountry or state), or they can be much larger, affecting, at their worst, entire

continents. Some parts of the world are more drought-prone than others, due to thevariability of rainfall from one season to the next. This includes large parts ofNorthern Africa, Central Asia and most of Australia.

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Reduced levels of rainfall in just one or two seasons can often be coped with becauseof the existing supplies of water that are held in storage such as rivers, lakes, damsand reservoirs. The careful rationing of water use will usually help a communitymanage its water needs until the rains come again. However, when surface waterstorages are not recharged and replenished for a number of consecutive seasons, thesituation can become desperate. In these circumstances, all non-essential uses ofwater tend to be the first to be completely restricted (in more developed parts of theworld this might include watering gardens and washing cars). After this, the situationbecomes extremely serious indeed, because it may no longer be possible to irrigatecrops and water animals, as dwindling water supplies are prioritised for human use,At this point the ability of a community to feed itself is places under threat.Eventually, and in the worst case, a severely drought affected community may not beable to meet its own water needs for purposes such as drinking and sanitation. Thiscan lead to the rapid spread of both dehydration and disease, resulting in widespreaddeath.

Causes of drought

The causes of drought include the following: Variations in the movement of the inter-tropical convergence zone (ITCZ). As

the ITCZ moves north and south through Africa, it brings a band of seasonalrain. In some years, high pressure zones expand and block the rain-bearingwinds. In southern Ethiopia and Somalia, where farmers depend for food onrain-fed agriculture, famines may result if the summer rains never arrive.

El Nino can bring major changes to rainfall patterns. In particular, it can bringdrought conditions to Indonesia and Australia.

Changes in mid-latitude depression tracks. In temperate regions, depressionsbring large amounts of rainfall. However, if blocking anticyclones form andpersist, depressions are forced to track further north, leading to very dryconditions. Droughts in the UK and France (1976, 1989-92, 1995, 2003 and2006) as well as in the US Midwest in the 1930s were all related to this cause.

Drought hazardsDrought leads to failure of crops and loss of livestock, wildfires, dust storms andfamine. It has economic impacts on agriculture and water-related businesses indeveloped countries.

FloodingFlooding is a frequent hazard and is evident in some 33% of the worlds area, which is

inhabited by over 80% of its population. Regional scale, high magnitude floods arefrequent events in India/Bangladesh and China.

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flood occurs when land that is usually dry becomes inundated. In most cases, floodsoccur after a prolonged period of rainfall, which causes water course to burst theirbanks and overflow. Sometimes, floods occur because the systems that have beendesigned to cope with average levels of rainfall, such as storm water drains and leveebanks, simply fail to work properly because of a blockage or a structural weakness.Floods can even occur in regions that have experienced no recent rainfall themselves.Floods can even occur in regions that have experienced no recent rainfall themselves.

This is especially true of regions that lie downstream of regions with heavy rainfall orvast amounts of melt water.

Some areas are more prone to flooding than others. For example, the relatively low-lying nation of Bangladesh is regularly inundated by melt waters that originate in themountainous regions of its neighbours India and Nepal.

Causes of flooding

By far the most common cause is excessive rainfall related to atmosphericprocesses, including monsoon rainfall and cyclones. In temperate climates, aseries of depressions sometimes brings prolonged high rainfall.

Intense rainfall sometimes associated with thunderstorms can lead to localisedflash flooding. These sudden floods can have a devastating impact.

The El Nino Southern Oscillation can bring devastating floods, as in Mozambiquein 1997 and 2006.

Rapid snowmelt can add water to an already swollen river system.

Flooding hazardsIn developing countries flooding may lead to deaths by drowning and disease,destruction of food crops and infrastructure and loss of homes. In developedcountries it disrupts transport and infrastructure, damages livelihoods and createshigh insurance costs.

Storms Storms include tropical cyclones, mid-latitude storms and tornadoes. Tropical

cyclones are violent storms between 200 and 700km in diameter. They occur in

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the latitudes 5-20 north and south of the equator. Once generated, cyclonestend to move westward and are at their height of destruction.

Tropical cyclones or hurricanes will only occur over warm ocean (over 26C) ofat least 70m depth at least 5N or 5S of the equator in order that the Corioliseffect (very weak at the equator) can bring about rotation of air.

CyclonesThe term cyclone can be applied to any area of low atmospheric pressure that iscreated when air rises from the surface of the earth. As the air rises into theatmosphere, it is cooled and condensation occurs. This may result in the formation of

clouds and eventually precipitation, both of which often characterise low pressuresystems. As he rising air is relatively unstable, cyclone can also bring windyconditions and are often associated with storms. Tropical cyclones, also commonlyknown as hurricanes and typhoons, are fuelled and formed by warm ocean water.

Temperate cyclones are formed when air of different characteristics converges andrises, drawn upwards by an accelerating jet stream.

The most intense cyclones are those that develop over the warm waters of the earthstropics. Here, the warmth of the tropical ocean rapidly heats the air lying just aboveits surface. As the air rises into the atmosphere, condensation is rapid and cloudformation occurs quickly. The tropical cyclones that result from this process are oftenvery large, and their behaviour can be extremely hard to predict. Tropical cyclonesthat begin life in the Atlantic Ocean are often referred to as hurricanes. Those thatbegin in the Pacific Ocean are sometimes called typhoons (Asia) or cyclones(Australia).

Tropical cyclones can continue to grow in size and strength while they remain over awarm ocean. Usually, the point at which a cyclone crosses a coastline will be thepoint of greatest destruction. For those living in small island communities, such asthose found throughout Polynesia in the Pacific Ocean, a tropical cyclone can spellpotential devastation for an entire island. Once cyclones cross from sea to land, they

tend to lose their strength rapidly, as they are no longer fed by the warmth andmoisture of the oceans. Often, they end up as much less violent rain-bearing

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depressions which can bring large amounts of much-needed rainfall to relatively dryinland areas.

Tropical storm hazardsStorms cause damage in several ways, including heavy rain (leading to floods andmudslides), high wind velocity and very low central pressure (leading to storm surgesand coastal flooding). They can be devastating (e.g. Hurricane Katrina).

Disaster hotspotsIdentifying and defining hazard hotspots

In 2001 the World Banks DisasterManagement Facility, togetherwith the Center of Hazard andRisk Management at ColumbiaUniversity began a project toidentify disaster hotspots, notonly at a country level but withina country. These hotspots are

multiple hazard zones. Theproject assessed the risk of deathand damage. The level of riskwas estimated by combiningexposure to the six major naturalhazards (earthquakes, volcanoes,landslides, floods, drought and

storms). Historical vulnerability (from data from the last 30 years) was combined withpotential vulnerability based on size, density and poverty of the population (asmeasures of mortality) and GDP per unit area (as a measure of potential economicdamage).

The World Banks global risk analysis was noteworthy for its use of geographicinformation systems techniques. Grid squares of 2.5 minutes latitude and longitudewere used as a base for various estimates of hazard probability, occurrence andextent, and these were then related to the economic value of the land, its populationand population density, and vulnerability profiles. As the aim was to identify disasteras opposed to hazard hotspots, only cells with a minimum population of 105 ordensities or above 5 per km were entered on the database of around 4 million cells.

Managing a hazard hotspot

The identification of multiple hazard zones has major implications for developmentand investment planning, and for disaster preparedness and loss prevention.However, many hazard-prone areas have long lists of priorities more immediate thanrisk management, such as poverty reduction, or fighting HIV/AIDS, and may be unableto afford the technology required to cope with multiple hazards. Most countries facesome kind of hazard, but six countries stand out as being the most hazard-prone inthe world: the Philippines, Japan, India, Bangladesh, China and Indonesia.

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DISASTER HOTSPOTS: THE PHILIPPINESThe Philippines, an island arc in southeast Asia,consists of over 7,000 islands, many verysmall, concentrated at latitudes between 5 and20N of the equator. It lies in a belt of tropicalcyclones (typhoons) and astride an active plateboundary. The dense oceanic Philippines plate

is being subducted beneath the Eurasian plate.The country experiences a tropical monsoonclimate and is subject to heavy rainfall.Flooding can lead to landslides because of thedeforestation of many hillsides.

The Philippines is a lower-middle incomecountry which is developing fast. With arapidly increasing young population, averagepopulation densities for the whole country are

high at 240 people per km with up to 2,000people per km in the megacity of Manila.Many of these people are very poor and live onthe coast, making them vulnerable to locallygenerated tsunamis and typhoon generatedstorm surges. On average, about ten typhoonsoccur each season, especially in Luzon.

In response, the government has established several organisations to carry outforecasting, warning, hazard risk assessment, disaster training and education. Theseinclude the National Disaster Co-ordinating Council; Philippine Atmospheric,

Geophysical and Astronomical Services; and the Philippine Institute of Volcanologyand Seismology, Land use planning and building regulation, and structural

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programmes of defences help people to survive the huge range of hazards facingthem.

It sits across a major plate boundary, so it faces significant risks from volcanoesand earthquakes

Its northern and eastern coasts face the Pacific, the worlds most tsunami-proneocean.

It lies within south-east Asias major typhoon belts. In most years, it is affectedby 15 typhoons and struck by 5 or 6 of them.

Landslides are common in mountain districts

Area: the Philippines consists of about 7000 islands, and is 25% bigger than the UKPopulation: 91 million in 2007Wealth: GDP in 2006 was US$5000 per capita; a middle income country according tothe World BankLandscape: mostly mountainous, with coastal lowlands, many people live and work onsteeply sloping land

Mount Pinatubos volcanic eruption in June 1991Mount Pinatubos eruption was the biggest the world had seen for over 50 years. Thevolcano showed signs of eruption in April 1991, with steam explosions and minorearthquakes. A 10km exclusion zone was set up around Pinatubo by governmentadvisers, who eventually extended the zone to 30km evacuating more people eachtime it was extended. Two weeks before the blast, they produced a video outliningthe risks of pyroclastic flows and lahars.

By 9 June 1991, 58 000 had been evacuated reaching 200 000 by 12 June (when thefirst eruption sent a cloud of ash 20km into the atmosphere, spreading over South-

East Asia within three days). The second eruption, on 15 June, was cataclysmic, adome on the side of the volcano collapsed, creating a pyroclastic blast and causinghuge lahars. However, effective monitoring and management reduced Pinatubosdeath and injury toll to just over 4300 people.

350 people died, including 77 in the lahars that occurred.

Some evacuees died in camps, where they were exposed to disease

80 000 hectares of farmland were buried beneath ash, disrupting the livelihoodsof 500 000 farmers and their family members

Economic losses were US$710 million mainly agriculture and property.

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The Philippines lies on the boundary between two tectonic plates, the Philippine andEurasian. The Eurasian Plate is forced beneath the Philippine, creating the deepManila Ocean Trench, to the west. The plates move in a series of jerks, producing anearthquake each time they do so.

Other hazard risksSome hazard risks in the Philippines are complex because they have multiple effects.One earthquake in 2006:

Killed 15 people, injured 100 and damaged or destroyed 800 buildings

Generated a local tsunami 3 metres high

Triggered landslides which breached the crater wall of Parker Volcano, and thenfell into Maughan Lake...

...creating a flood which washed away houses

The Guinsaugon landslideGuinsaugon was a village in the central Philippines. In February 2006, a mudslidecompletely engulfed the village and its land, covering 3km and killing about 1150people. It was not unusual a series of storms in December 2004 killed 1800 people

in the north-eastern Philippines. In 2003, 200 people were killed in landslides.Typhoons and storms kill several thousand people there every decade.

Thephysical causes were:

There was unseasonable torrential rain; 2000mm of rain fell in 10 days inFebruary normally the dry season

La Nina a cyclic ocean and wind current affecting South East Asia wasprobably the cause of the rainfall.

A 2.6 magnitude earthquake struck just before the slide and may have triggeredit

The human causes included:

Deforestation of native forest cover protecting the soil. In 50 years, logging hasreduced several million hectares of forest to about 600 000 today

Replacement of native forest by shallow rooted trees, such as coconuts, furtherreducing soil protection.

DISASTER HOTSPOTS: THECALIFORNIA COAST

The state of California contains nearly 40million people and has an economy thesize of a high-income country. However,it suffers from a vast range of hazards,including high risks from geophysicalhazards (especially earthquakes) as wellas a range of atmospheric hazards suchas fog, drought and associated wildfires,and major impacts from the El NinoSouthern Oscillation. The hazardouszone is concentrated along the SanAndreas Fault, which runs parallel to the

coast.

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California is home to the megacity of Los Angeles, San Francisco and San Diego.Much of the coastline is crowded as various land uses compete for prime space. Thehuman-physical interface increases the danger from hazards, and only sophisticatedmanagement prevents California from becoming a disaster zone (recent major eventssuch as the Loma Prieta earthquake of 1989 led to very few deaths). NeverthelessCalifornia contains an underclass of around 3.5 million people, many of them semi-legal migrants, a large proportion of whom live in hazardous locations.

Ever since 1849, when gold was discovered, California has been one of the mostdesirable places to live in the USA. It is wealthy; its economy is the worlds sixthlargest, bigger than France or Italy. 25 Californian counties have per capita incomesof over US$65 000 (about 35 000) per year, making them amongst the worldswealthiest places. Yet the risk map above, showing the likelihood of hazardoccurrences, identifies California as the USAs most hazardous state. There are tworeasons for this: plate tectonics and climatic patterns, particularly those related to ElNino and La Nina.

Plate tectonics and California

San Francisco seems like a city living on the brink of disaster. Its residents know thatit lies along the San Andreas fault, where the Pacific Plate moves north-westwardspast the North American Plate. The two move in the same direction but the PacificPlate moves move more quickly, thus creating friction. This is called a conservativeplate boundary. The San Andreas fault is the fracture or fault line between them.It runs along the Californian coast from Los Angeles north to San Francisco. Otherfault lines run parallel to the major fault; San Francisco is built over two of them.

These faults move regularly, causing earthquakes. In 1906, San Francisco wasdestroyed in an earthquake measuring 8.2 on the Richter Scale. It fractured gas pipes(which caused explosions and fires) and water mains (which could have prevented the

spread of the fires). A further earthquake, of magnitude 7.1, occurred in 1989. Withis epicentre at Loma Prieta, it caused major damage and deaths. Some buildingscollapsed, while others were badly shaken. Five years later, a further earthquakeshook Northridge in Los Angeles.

The 1989 Loma Prieta earthquake in San Francisco

Date and time: 5.04pm, 17 October 1989

Magnitude and location: 7.1; epicentre Loma Prieta in the Santa Cruz mountains

A magnitude 5.2 aftershock struck the region 37 minutes after the mainearthquake

63 people died and 13 757 were injured (most were killed when a freewaycollapsed)

1018 homes were destroyed and 23 408 damaged

366 businesses were destroyed and 3530 damaged

The damage cost US$6 billion

The 1994 Northridge earthquake in Los Angeles

Date and time: 4.31am, 17 January 1994

Magnitude and location: 6.7; striking the densely populated San Fernando Valleyin northern Los Angeles

There were many thousands of aftershocks (mostly in magnitude 4.0-5.0) duringthe following weeks, causing further damage

57 people died and over 1500 were seriously injured

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12 500 buildings were damaged; 25% suffered severe-to-moderate damage

9000 homes and businesses were without electricity for several days (20 000without gas), and 48 500 people were without water

There was damage to several freeways serving Los Angeles choking traffic for30km.

Dealing with earthquake threats

What if there was another major earthquake? The panels above show that inwealthier countries the economic damage can be great, whereas the impacts indeveloping economies tend to affect people. To protect themselves, mostCalifornians insure their property against earthquake damage. After the Loma Prietaand Northridge earthquakes, demand for insurance rose sharply. But, by 1996, it haddropped to below 1989 levels, and has declined further since. Many people avoid thecost of taking out insurance.

Climatic patterns and CaliforniaCalifornia has a reputation as a state where the weather is always perfect, but itsuffers periodic changes which can be hazardous. Sometimes drought occurs and

forest fires threaten, while at other times floods and landslides provide headline news.Flood risks in California vary, but they coincide with El Nino; forest fires and droughtcoincide with La Nina.

The Boxing Day tsunami, 2004Tsunamis occur where:

Earthquakes measure more than 6.5 on the Richter Scale

The earthquakes focus is shallow beneath the Earths surface

The focus is also beneath the ocean

The earthquake that caused the Boxing Day tsunami was estimated at between 9.0and 9.3 on the Richter scale, and was over 100 times stronger than the one whichcaused the Kobe earthquake in 1995. The thrust heaved the floor of the Indian Oceantowards Indonesia by about 15 metres, and, in so doing, sent out shock waves. Oncestarted, these radiated out in a series of ripples, moving almost unnoticed acrossoceans until they hit land. The longer and shallower the costal approach, the morethe ripples built up in height. The waves that struck the shallow coastline near BandaAceh (only 15 minutes from their origin), and parts of Sri Lanka were nearly 17 metreshigh on impact.

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Sri Lanka who died in the 2004 tsunami?

Sri Lanka was the second most seriously affected country after Indonesia, with over30 000 deaths, 5 700 people missing and 861 000 people displaced. One surveycarried out in Ampara (an eastern coastal district of Sri Lanka) found that the mostvulnerable people had suffered the most. This area had previously experienced rapidcoastal urbanisation. Its economy is also based on tourism and subsistence fishing,which left it vulnerable to the tsunami.

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In this part of Ampara, out of a population of3533 (living in 859 households), 12.9% died.Of these:

Most deaths occurred during andimmediately after the disaster

More than double the number ofwomen died, compared to men

56% of victims were children The elderly and disabled were more

likely to die than young, healthyadults; 15% of deaths were of peopleaged over 50

Other factors which increased peoplesvulnerability were:

Whether they were indoors at the timeof the tsunami (13.8% of casualties).Women and children were more likely

to be inside on the morning of thetsunami. Even compared with thoseon the beach or in the sea, people athome were more likely to die.

The quality of the building they were in, either in terms of its structure or itslocation and exposure to the full force of the waves. 14% of deaths occurred inbuildings that held up well or withstood the initial impact.

Whether they belonged to a fishing family (15% of deaths)

Whether they had lower educational qualifications. Those with highereducational qualifications were 20% less likely to die if educated to secondary

level, and 60% less likely if educated to university level. Uniersity educatedpeople earn more and could afford to live away from high-risk locations.

Whether they earned lower incomes. In Ampara, 15 000 rupees (US$150) permonth is a high wage. Most deaths occurred in households earning 1-2999 and3000-5999 rupees, with few deaths in the highest earnings category.

Environmental change and the tsunamiOne clear factor has emerged from several countries affected by the tsunami thecountries which suffered most were those where the tourism industry has grownrapidly in recent years. Many coastal areas of Thailand and Sri Lanka have beencleared of coastal mangrove swamps to make way for hotels and resorts. Mangrovesact as a natural barrier, absorbing wave power and creating a natural coastal bufferzone. Damage from the tsunami was noticeably reduced in coastal areas which hadmaintained their mangrove swamps, beach forest and coral reefs.

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What? Where? When? Why? Who?GEOPHYSICAL HAZARDS

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DISCLAIMERAll of the text to create this revision document has been taken in its unedited formfrom the three textbooks released for the Edexcel AS specification. Likewise, the

diagrams and maps have been scanned from these sources. This is purely to createone comprehensive document to support the course.

References

Digby et al (2008) AS Geography for Edexcel Oxford University Press Oxford

global hazards ed excel as revision

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