Natural hazards such as earthquakes,floods, hurricanes, droughts and

volcanic eruptions are rarely out of thenews. Every year they are responsiblefor many deaths and serious injuries,they destroy livelihoods and damage

economies. Scientists predict thatclimate change will affect the frequency

and severity of some natural hazards.

Most natural hazards cannot beprevented but by understanding howand where they occur, what causes

them, and what circumstances increasetheir ferocity, we can develop effective

strategies to reduce the damagethey cause.

The Natural Environment ResearchCouncil (NERC) is the UK’s leading

environmental research organisation.NERC scientists advise the UK

government on ways to minimise therisk of natural hazards.

In this briefing note we look at somemajor natural hazards and what risksthey pose to life, the economy and the

environment.

w EarthquakesEarthquakes can occur anywhere but major earthquakestend to happen along fault lines in the Earth’s crust.

Although there are thousands of earthquakes each year onlya few damage towns or cities.

The British Geological Surveyregisters 200-300 smallearthquakes a year in the UK.

There is still no reliable way topredict earthquakes despite 40years of research, but statisticsand geological knowledge canindicate where largeearthquakes are likely and whattheir effects will be.

Many major earthquake zonessuch as California and Japanare extremely well monitored.Recently, scientists havedeveloped systems to transmitwarnings immediately after an earthquake that will givedistant cities time to shut down critical facilities.

A few months before the Indian Ocean earthquake in 2004,some seismologists warned that a large earthquake couldstrike the coast of Sumatra. There was no way to convert thisinformation into practical measures at the time.

Collapsing buildings cause most deaths during anearthquake. Engineers can design homes and offices towithstand earthquake shaking.

Japan is one of the most seismically active countries on theplanet and geologists know there will be a major earthquakenear Tokyo in the future - possibly soon.

w Volcanoes One in ten of the world’s population live close to active orpotentially active volcanoes.

On average 50-60 volcanoes are active each year. Around 1,500volcanoes have been active in the last 10,000 years.

Volcanoes rarely erupt without warning, but scientists monitoronly a few of the world’s volcanoes.

Constant monitoring greatly reduces the death toll when avolcano erupts as exclusion zones are usually very accurate.

The main hazards associated with volcanoes are: lava flows,pyroclastic flows (fast moving hot rocks and debris), explosionsand mudflows. Secondary hazards include tsunamis andchanges to regional and global climates causing temperaturedrops, famine and disease.

Fine volcanic ash can stop a jet engine.

In 1988 scientists suggested there would be an increase involcanic activity on the Caribbean island of Montserratsometime in the mid-1990s. The volcano erupted in 1995 butgood monitoring procedures meant fatalities were few, thoughdamage to the surrounding area was extensive.

Volcanic eruptions have far reaching effects on regional andglobal climate. All eruptions throw huge clouds of sulphurdioxide gas into the atmosphere. When Pinatubo in thePhilippines erupted in 1991 a plume of gas spiraled into theatmosphere and enveloped the planet, lowering temperaturesby about 0.25 degrees centigrade for a few weeks.

Volcanic activity is not entirely random. It is often seasonal,suggesting that environmental factors such as weather, climateand sea level influence volcanoes. The volcano on Montserratseems to have a tendency for large eruptions in summer, maybebecause of increased rainfall.

Volcanic plumes deplete ozone in the upper atmosphere.

Eruptions can go undetected when clouds shroudvolcanoes. NERC scientists have developed a sensor tomonitor volcanoes, even through dense cloud.

Super-eruptions, large enough to cause a global disaster,occur on average every 100,000 years. The last super-eruption was 74,000 years ago in Toba, Indonesia.

Natural disasters waiting to happen In 2005, the Natural Hazard Working Group in the UK identified a number of major environmental hazards thatcould either physically affect the entire planet or have a knock-on effect on the global economy.

Natural hazard Place Impact

Earthquake Tokyo, Japan O

Earthquake and tsunami South east Asia Millions of people affected

Magnitude 9 earthquake Pacific coast, United States Huge cost to the insurance industry

Volcano and tsunami Cumbre Vieja volcano, Canary Islands Major tsunami threat to the Atlantic, a

Catastrophic failure of the Sarez Tajikistan This dam threatens millions of people l

Major volcanic eruption 1,500 volcanoes worldwide O

Asteroid impact Anywhere A

Wds

Hurricane Katrina was the worst natural disaster in US historywith damages expected to top $100 billion.

An earthquake reduced the townof Bam in Iran to rubble in 2003.

DougW

ebb/Alamy

The system used to measure the size of anearthquake is known as the Richter Scale. It is alogarithmic scale which means that an earthquakeof magnitude nine (M9) is ten times greater than anearthquake of magnitude eight.

appen r of major environmental hazards that

c on the global economy.

Impact

Over £1.8 trillion

Millions of people affected

Huge cost to the insurance industry

Major tsunami threat to the Atlantic, according to some scientists

This dam threatens millions of people lake natural dam

One in ten people worldwide live close to a potentially dangerous volcano

A direct impact could destroy a city

w Rising sea levels Global sea level rose on average by 1-2cm a decade during the20th century. Sea level is predicted to rise by 10-90cm thiscentury.

More than 300 million people live withinone metre of average sea level and onethird of the world's population live near thecoast.

Many heavily populated areas, for example,

Worst naturaldisasterssince 1970

Bangladesh, the Netherlands and cities such as New Orleans,are near or below sea level and require dams to keep the sea atbay.

The main cause of sea level rise is thermal expansion of theoceans: as water heats up its volume increases. Another causeis melting glaciers and ice sheets.

If Greenland’s ice sheet melted completely, sea level would riseby seven metres, although this would take many centuries.

Much of Bangladesh is on the flood plains of three major rivers.

Hurricane Katrina. A record-breaking 27 tropicalstorms formed in the Caribbean in 2005.N

ASA

w Landslides Landslides kill and injure many people throughout the worldevery year.

The processes that cause landslides are well understood,including erosion, saturated soil and deforestation.

More storms with heavy rainfall, as predicted by climatechange models, will make some types of landslide morecommon in the UK.

NERC’s British Geological Survey (BGS) has recorded morelandslides across the UK in recent years.

BGS has used its understanding of landslides and geologicaldata to make maps of likely landslide hazards.

These maps help land managers to keep land stable andprotect life and property.

w Storm surgesWhen hurricane Katrina hit New Orleans in August 2005 theaccompanying storm surge broke through the sea defences andswamped the city, causing more damage than the strong winds.

Britain’s worst recent storm surge occurred in 1953. Itdevastated much of the east coast of England and killed 304people in the UK.

Since the storm the Thames Barrier was built, along with 36additional tidal barriers and 200 miles of flood walls.

Use of the Thames Barrier has increased from once every twoyears in the 1980s to an average of six times a year over thepast five years. The decision to raise or lower the ThamesBarrier is based on data from NERC’s Proudman OceanographicLaboratory. The cost of getting this wrong and London floodingwould run in to billions of pounds.

Storm surges were responsible for the deaths of 300,000 peoplein Bangladesh in 1970 and a further 200,000 in the 1980s.

Climate change could result in more hurricanes, increasing thefrequency of large storm surges.

Scientists can normally accurately predict storm surges severaldays before they happen.

w FloodsIn the last few decades flooding has killed morepeople than any other natural hazard.

Between 1975 and 2001 the annual number offlash floods across Europe increased.

Five million people in England and Wales are at risk fromflooding every year.

UK assets worth £132.2 billion are at risk from coastal floods.

Climate change scientists say that while summer rainfall inBritain will reduce, the storms that come will be more severe,causing more flooding.

Better land management reduces flood risk.

The Flood Estimation Handbook, produced by scientists atNERC’s Centre for Ecology & Hydrology, gives guidance onrainfall and flood frequency, which are predicted to becomemore common in the UK.

Maps produced by NERC’s BritishGeological Survey show the extentof floodplains and coastal areas atrisk of flooding, aiding floodprediction and management.

NERC’s Flood Risk from ExtremeEvents programme is addressingenvironmental problems associatedwith flood risk including thosecaused by climate change.

w TsunamisTsunamis are usually caused by undersea earthquakes,volcanic eruptions or landslides.

Eighty percent of all recorded tsunamis occur in the PacificOcean – the most seismically active region of the planet.

Tsunamis in the Atlantic are rare but not impossible. Anearthquake off the coast of Portugal in 1755 caused a 12 metrehigh tsunami that destroyed the city and left over 60,000 dead.

Some scientists believe that a volcano on La Palma in theCanaries could collapse causing an enormous landslide into thesea. This might create a tsunami 50 metres high that wouldsweep around the Atlantic devastating the Canary Islands, thewest coast of Africa and the eastern coast of the United States.Other scientists believe that a major tsunami is unlikely as thelandslide would slip gradually into the sea.

A tsunami early warning system has been operating in thePacific since 1965.

An Indian Ocean early warning system willbegin operations in 2006 followed by an AtlanticOcean system in 2007.

The Indian Ocean tsunami,Boxing Day 2004.

hree major rivers.

Landslides destroy infrastructure.

w Tropical stormsOf all natural hazards tropical storms are probably theeasiest to monitor and predict. Warnings are givensometimes days in advance and forecasters canaccurately determine their strength and direction, yet theycan still cause havoc.

The UK does not have a tropical climate so hurricanes inthe strict sense do not hit our shores, but hurricane-forcewinds do sometimes strike.

Climate models predict more ferocious storms in a warmerworld. Recent research suggests that wind speedsincrease by three percent when sea-surface temperaturesrise by half a degree centigrade. Global averagetemperatures have risen by around 0.7°C since 1860.

w DroughtCracked earth and dry riverbeds signal the onset ofdrought. In developing countries crop failures and untoldhuman suffering usually follow.

Worldwide, the ten hottest years on record have alloccurred since 1990. Computer models predict that someregions of Africa will become even drier in the future.

Improved seasonal weather forecasting can preparecommunities for drought, helping to mitigate its effects.NERC scientists are investigating how regional weatherconditions are connected. For example, we knowunseasonal European weather, and El Niño in the Pacific,can weaken Indian monsoons. And high surfacetemperatures in the Atlantic Ocean may have caused the2005 Amazonian drought.

The West African monsoon is under close scrutiny fromNERC scientists and African and European colleagues.

In the UK the economic implications of prolonged dryperiods are huge. Some types of clay shrink dramaticallywhen they dry out causing serious subsidence. In the last30 years insurance claims for subsidence as a result ofshrinking clay soils have cost the UK economy over £8.2 billion.

British Geological Survey scientists have made mapsshowing areas of shrinkable clay hazard in Great Britain.House builders can use these maps to built houses withsubsidence-resistant foundations in affected areas.

w Near Earth ObjectsMany scientists believe that a huge crater beneath the Yucatanpeninsula in the Gulf of Mexico is proof that an asteroid collidedwith Earth 65 million years ago, wiping out the dinosaurs andmuch other life on this planet.

Scientists take the threat of another devastating impact veryseriously. An asteroid one kilometre in diameter could kill onebillion people. The last asteroid of this size collided with Earth900,000 years ago.

Asteroids of 100-250 metres across are more frequent and adirect impact could destroy a city. A 100-metre rock strikes onaverage every 50 years, a 250-metre rock every 3,000 years.

Scientists can precisely predict the time and location of potentialimpacts and there is a realistic chance that disaster could beaverted by deflecting the rock away from a collision course.

The Near Earth Objects Information Centre in Leicester, UK, ismonitoring asteroids and comets large enough to causesubstantial damage to planet Earth.

w Space weatherSolar flares cause power blackouts and can disruptcommunication systems and navigational aids.

The insurance, telecommunications and aerospace industriesneed better space-weather forecasts to protect expensivespacecraft.

NERC’s British Geological Survey is helping to monitor solaractivity and advising power companies on mitigation strategies.

NERC’s British Antarctic Survey has set up instruments acrossAntarctica to improve space-weather prediction.

When a tropical storm’s wind speedexceeds 118 kilometres an hour itbecomes known as a typhoon in thenorthwest Pacific, a cyclone in theIndian Ocean and around Australia,or a hurricane in the Atlantic.

This briefing note draws on NERC-funded work and reports such as: The Role of Science in Physical NaturalHazard Assessment (the Natural Hazard Working Group, 2005), Sparks, S. & Self. S. et al., 2005: Super-eruptions: global effects and future threats: (The Geological Society of London), Hazard and Risk ScienceReview 2005 (Benfield Hazard Research Centre).

w ContactsFor more information about NERC research on naturalhazards contact:

Natural Environment Research CouncilTel: 01793 411500 www.nerc.ac.uk

British Antarctic SurveyTel: 01223 221400 www.antarctica.ac.uk

British Geological SurveyTel: 0115 9363100 www.bgs.ac.uk

w What are we doing?NERC scientists were actively involved in scientificinvestigations following the devastating earthquake off thecoast of Sumatra, Boxing Day 2004. This work included:mapping the sea floor, advice on rebuilding towns andreducing freshwater contamination, helping create an earlywarning system and assessing future tsunami hazards.

NERC manages Britain’s Earth observation budget and fundssatellite technology to increase knowledge of natural hazards.

NERC’s British Geological Survey monitors earthquakes andvolcanoes worldwide reducing uncertainties and improvingpredictions.

NERC’s British Antarctic Survey scientists are traininginstruments on the skies above Antarctica to monitor violentsolar flares that can destroy satellites.

NERC’s Proudman Oceanographic Laboratory (POL) hosts thePermanent Service for Mean Sea Level – the global data bankfor information on sea level change. The decision to raise andlower the Thames Barrier is based on POL data.

NERC’s Centre for Ecology & Hydrology is working on flood anddrought forecasts and their ecological impacts.

In 2005, the UK government created the Natural HazardWorking Group. A number of NERC scientists sat on this group.In their report, published in June 2005, they highlighted theneed for an international panel to advise governments onpotential natural hazards and recommended governments builda coordinated warning system for the major natural hazards.

For information on natural hazard monitoring systems visitwww.nerc.ac.uk

Centre for Ecology & HydrologyTel: 01487 772400 www.ceh.ac.uk

NERC Centre for the Observation and Modelling ofEarthquakes and Tectonics (COMET)Tel: 01865 272000 http://comet.nerc.ac.uk

National Oceanography Centre, SouthamptonTel: 023 8059 6666 www.noc.soton.ac.uk

Proudman Oceanographic LaboratoryTel: 0151 795 4800 www.pol.ac.uk

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