(4) Global Catastrophes

MOST BRUTAL Natural Disasters - Video

Institute of World Ideas - Global Catastrophes and Trends. Next 50 years.

World Forum of Catastrophe Programmes

Global Catastrophic Risk Institute

GC3

Hazardous Earth

While earthquakes and volcanic eruptions are linked to how our planet functions geologically, other geophysical hazards are more dependent upon processes that operate in the Earth’s atmosphere.

Rather than by heat from the interior, our planet’s weather machine is driven by energy from the Sun. Our nearest star is the ultimate instigator – aided by the Earth’s rotation and the constant exchange of energy and water with the oceans – of the tropical cyclones and floods that exact an enormous toll on life and property, particularly in developing countries. Still other lethal natural phenomena have a composite origin and are less easy to pigeonhole. The giant sea waves known as tsunamis (or sometimes incorrectly as ‘tidal waves’), for example, can be formed in a number of different ways; most commonly by submarine earthquakes, but also by landslides into the ocean and by eruptions of coastal and island volcanoes.

Similarly, many landslides result from collusion between geology and meteorology, with torrential rainfall destabilizing already weak slopes. Although there remains an enormous amount to learn about natural hazards, their causes and characteristics, our current level of knowledge is truly encyclopedic – and if so desired you can indeed consult weighty and authoritative tomes focused entirely on specific hazards. Here, as a taster, my intention is to gallop you through the principal features of the major natural hazards at a pace that I hope is not too great, before placing their current and future impact on our society in some perspective.

At any single point and at any one time the Earth and its enclosing atmospheric envelope give the impression of being mundanely stable and benign. This is, however, an entirely misleading notion, with something like 1,400 earthquakes rocking the planet every day and a volcano erupting every week. Each year, the tropics are battered by up to 40 hurricanes, typhoons, and cyclones, while floods and landslides occur everywhere in numbers too great to keep track of.

In terms of the number of people affected – at least 100 million people a year – floods undoubtedly constitute the greatest of all natural hazards, a situation that is likely to continue given a future of rising sea levels and more extreme precipitation. River floods are respecters of neither wealth nor status, and both developed and developing countries have been severely afflicted in recent years, across every continent. Wherever rain is unusually torrential or persistent, it will not be long before river catchments fail to contain surface run-off and start to expand across their flood plains and beyond. In fact, the intensity of rainfall can be quite astonishing, with, in 1970, nearly 4 centimeters of rain falling in just 60 seconds on the French Caribbean island of Guadeloupe – a world record. On another French island, Réunion, in the Indian Ocean, a passing cyclone dropped close to 2 meters of rain during a single 24-hour period in March 1952.

As flood plains all over the world become more crowded, the loss of life and damage to property caused by swollen rivers has increased dramatically. In the spring of 1993, the Mississippi and Missouri rivers burst their banks, inundating nine Midwest states, destroying 50,000 homes and leaving damage totaling US$20 billion. Massive floods occurred in many parts of the UK in autumn 2000 as rain fell with a ferocity not seen for over 300 years, and much of central Europe was swamped beneath record floodwaters in the summer of 2002.

River flooding continues to pose a major threat in China, and has been responsible for over 5 million deaths over the last 150 years. Bangladesh has it even worse, with the country often finding two-thirds of its land area under water as a result either of floodwaters pouring down the great Ganges river system or of cyclone-related storm surges pouring inland from the Bay of Bengal. Coastal flooding due to storms probably takes more lives than any other natural hazard, with an estimated 300,000 losing their lives in Bangladesh in 1970 and 15,000 at Orissa, northeast India, in 1999.

Partly through their effectiveness at spawning floods, but also through the enormous wind speeds achieved, storms constitute one of the most destructive of all natural hazards. Furthermore, because they are particularly common in some of the world’s most affluent regions, they are responsible for some of the costliest natural disasters of all time. Every year, the Caribbean, the Gulf and southern states of the USA, and Japan are struck by tropical cyclones, while the UK and continental Europe suffer increasingly from severe and damaging winter storms. In 1992, Hurricane Andrew virtually obliterated southern Miami in one of the costliest natural disasters in US history, resulting in losses of US$32 billion. This epic storm brought to bear on the city wind speeds of up to 300 kilometers per hour, leaving 300,000 buildings damaged or destroyed and 150,000 homeless. The 2004 and 2005 Atlantic hurricane seasons were extraordinarily active, with the state of Florida being struck by six hurricanes over a twelve-month period.

The 2005 season also spawned Hurricane Katrina, which far exceeded Andrew in its destructiveness, killing thousands and leaving 80 per cent of the city of New Orleans awash in up to 7 meters of floodwater. Destructive windstorms are not only confined to the tropics, and hurricane-force winds also accompany low-pressure weather systems at mid-latitudes. Many residents of southern England will remember the Great Storm of October 1987 that felled millions of trees with winds whose average speeds were clocked at just below hurricane force. More recently, in 1999, France suffered a similar ordeal as winter storm Lothar blasted its way across the north of the country. On the other side of the ‘pond’ the US Midwest braces itself every year for a savage onslaught from tornadoes: rotating maelstroms of solid wind that form during thunderstorms in the contact zone between cold, dry air from the north and warm, moist air from the tropics. No man-made structures that suffer a direct hit can withstand the average wind speeds of up to 500 kilometers an hour, and damage along a tornado track is usually total. Although rarely as lethal as hurricanes, in just a few days in April 1974 almost 150 tornadoes claimed over 300 lives in Kentucky, Tennessee, Alabama, and adjacent states.

Of the so-called geological hazards – earthquakes, volcanic eruptions, and landslides – there is no question that earthquakes are by far the most devastating. Every year about 3,000 quakes reach magnitude 6 on the well-known Richter Scale, which is large enough to cause significant damage and loss of life, particularly when they strike poorly constructed and ill-prepared population centers in developing countries. As previously mentioned, most large earthquakes are confined to distinct zones that coincide with the margins of plates. In recent years, sudden movements of California’s San Andreas Fault have generated large earthquakes in San Francisco (1989) and southern California (1994), the latter causing damage totaling US$35 billion – the costliest natural disaster in US history. Just a year later, a magnitude 7.2 quake at the western margin of the Pacific plate devastated the Japanese city of Kobe, killing 6,000 and engendering economic losses totaling a staggering US$150 billion – the most expensive natural disaster of all time.

Four years after Kobe, the North Anatolian Fault slipped just to the east of Istanbul, generating a severe quake that flattened the town of Izmit and neighboring settlements and took over 17,000 lives. On 26 December 2003, a moderate (magnitude 6.6) earthquake flattened the historic city of Bam in southern Iran, taking 26,000 lives, while a year later to the day, a massive magnitude 9.15 quake off the west coast of Sumatra led to the Earth-shattering Asian tsunami. Large earthquakes can also occur, however, at locations remote from plate margins, and have been known in northern Europe and the eastern USA, which are not regions of high seismic risk. The last such intraplate quake devastated the Bhuj region of India’s Gujarat state in January 2001, completely destroying 400,000 buildings and killing perhaps as many as 100,000 people. There is a truism uttered by earthquake engineers: it is buildings not earthquakes that kill people. Without question this is the case, and both damage to property and loss of life could be drastically reduced if appropriate building codes were both applied and enforced.

Earthquakes, however, also prove lethal through the triggering of landslides as a result of ground shaking, and by the formation of tsunamis. The latter are generated when a quake instantaneously jerks upwards – perhaps by just a meter or so – a large area of the seabed, causing the displaced water above to hurtle outwards as a series of waves. When these enter shallow water they build in height – sometimes to 30 meters or more – and crash into coastal zones with extreme force. In 1998, Sissano and neighboring villages on the north coast of Papua New Guinea were wiped out and 3,000 of their inhabitants drowned or battered to death by 17 meter high tsunamis that struck within minutes of an offshore earthquake.

Estimates of the number of active volcanoes vary, but there are at least 1,500 and possibly over 3,000. Every year around 50 volcanoes erupt, some of which – like Kilauea on Hawaii or Stromboli in Italy – are almost constantly active. Others, however, may have been quiet for centuries or in some cases millennia and these tend to be the most destructive. The most violent volcanoes occur at destructive plate margins, where one plate is consuming another. Their outbursts rarely produce quiet flows of red lava and are more likely to launch enormous columns of ash and debris 20 kilometers or more into the atmosphere. Carried by the wind over huge areas, volcanic ash can be extremely disruptive, making travel difficult, damaging crops, poisoning livestock, and contaminating water supplies. Just 30 centimeters or so of wet ash is sufficient to cause roofs to collapse while the fine component of dry ash can cause respiratory problems and illnesses such as silicosis. Close to an erupting volcano the depth of accumulated ash can totals several meters, sufficient to bury single-storey structures. This was the fate of much of the town of Rabaul on the island of New Britain (Papua New Guinea), during the 1994 eruptions of its twin volcanoes Vulcan and Tavurvur. For years following the 1991 eruption of Pinatubo in the Philippines, thick deposits of volcanic debris provided a source for mudflows whenever a tropical cyclone passed overhead and dumped its load of rain. Almost a decade later, mud pouring off the volcano was still clogging rivers, inundating towns and agricultural land, and damaging fisheries and coral reefs. Somewhat surprisingly, mudflows also constitute one of the biggest killers at active volcanoes. In 1985 a small eruption through the ice and snow fields of Columbia’s Nevado del Ruiz volcano unleashed a torrent of mud out of all proportion to the size of the eruption, which poured down the valleys draining the volcano and buried the town of Armero and 23,000 of its inhabitants.

Even scarier and more destructive than volcanic mudflows are pyroclastic flows or glowing avalanches. These hurricane-force blasts of incandescent gas, molten lava fragments, and blocks and boulders sometimes as large as houses have the power to obliterate everything in their paths. In 1902, in the worst volcanic disaster of the twentieth century, pyroclastic flows from the Mont Pelée volcano on the Caribbean island of Martinique annihilated the town of St Pierre as effectively as a nuclear bomb; within a few minutes leaving only four survivors out of a population of close to 29,000. The threat from volcanoes does not end there: chunks of rock collapsing from their flanks can trigger huge tsunamis, while noxious fumes can and have locally killed thousands and their livestock. Volcanic gases carried into the stratosphere, and from there around the planet, have modified the climate and led to miserable weather, crop failures, and health problems half a world away. On the grandest scale, volcanic super-eruptions have the potential to affect us all, through plunging the planet into a frigid volcanic winter and devastating harvests worldwide.

Of all geological hazards, landslides are perhaps the most underestimated, probably because they are often triggered by some other hazard, such as an earthquake or deluge, and the resulting damage and loss of life is therefore subsumed within the tally of the primary event. Nevertheless, landslides can be highly destructive, both in isolation and in numbers. In 1556, a massive earthquake struck the Chinese province of Shensi, shaking the ground so vigorously that the roofs of countless cave dwellings collapsed, incarcerating (according to Imperial records) over 800,000 people.

In 1970, another quake caused the entire peak of the Nevados Huascaran Mountain in the Peruvian Andes to fall on the towns below, wiping out 18,000 people in just four minutes and erasing all signs of their existence from the face of the Earth. Heavy rainfall too can be particularly effective at triggering landslides, and when in 1998 Hurricane Mitch dumped up to 60 centimetres of rain on Central America in 36 hours, it mobilized more than a million landslides in Honduras alone, blocking roads, burying farmland, and destroying communities.

The final – and perhaps greatest – threat to life and limb comes not from within the Earth but from without. Although the near constant bombardment of our planet by large chunks of space debris ended billennia ago, the threat from asteroids and comets remains real and is treated increasingly seriously. Recent estimates suggest that around a thousand asteroids with diameters of 1 kilometer or more have orbits around the Sun that approach or cross the Earth’s, making collision possible at some point in the future: this population includes many objects 2 kilometers across and larger.

An object this large striking our planet would trigger a cosmic winter, due to dust lofted into the stratosphere blocking out solar radiation, perhaps wiping out a quarter or so of the human population as a consequence. The revival of interest in the impact threat has arisen as a result of two important scientific events during the last decade: first, the identification of a large impact crater at Chicxulub, off Mexico’s Yucatan Peninsula, which is now widely regarded as the ‘smoking gun’ responsible, ultimately, for global genocide at the end of the Cretaceous period: second, the eye-opening collisions in 1994 of the fragments of Comet Shoemaker-Levy with Jupiter. Images flashed around the world of resulting impact scars larger than our own planet were disconcerting to say the least and begged the question in many quarters – what if that were the Earth?

Natural hazards and us

If you were not already aware of the scale of the everyday threat from nature then I hope, by now, to have engendered a healthy respect for the destructive potential of the hazards that many of our fellow inhabitants of planet Earth have to face almost on a daily basis. The reinsurance company Munich Re., who, for obvious reasons, have a considerable interest in this sort of thing, estimate that up to 15 million people were killed by natural hazards in the last millennium, and over 3.5 million in the last century alone.

At the end of the second millennium ad, the cost to the global economy reached unprecedented levels, and in 1999 storms and floods in Europe, India, and South East Asia, together with severe earthquakes in Turkey and Taiwan and devastating landslides in Venezuela, contributed to a death toll of 75,000 and economic losses totaling US$100 billion. In 2004, the statistics were even more depressing, with the Indian Ocean tsunami, together with earthquakes in Morocco and Japan, record storms in the USA and Japan, and flooding across Asia contributing to a third of a million deaths and economic losses of US$145 billion.

The last three decades of the twentieth century each saw a billion or so people suffer due to natural disasters. Unhappily, there is little sign that hazard impacts on society have diminished as a consequence of improvements in forecasting and hazard mitigation, and the outcome of the battle against nature’s dark side remains far from a foregone conclusion. While we now know far more about natural hazards, the mechanisms that drive them, and their sometimes awful consequences, any benefits accruing from this knowledge have been at least partly negated by the increased vulnerability of large sections of the Earth’s population. This has arisen primarily as a result of the rapid rise in the size of the world’s population, which doubled between 1960 and 2000. The bulk of this rise has occurred in poor, developing countries, many of which are particularly susceptible to a whole spectrum of natural hazards.

Furthermore, the struggle for Lebensraum has ensured that marginal land, such as steep hillsides, flood plains, and coastal zones, has become increasingly utilized for farming and habitation. Such terrains are clearly high risk and can expect to succumb on a more frequent basis to, respectively, land sliding, flooding, storm surges, and tsunamis. Another major factor in raising vulnerability in recent years has been the move towards urbanization in the most hazard-prone regions of the developing world. In 2007, for the first time ever, more people will live in urban environments than in the countryside, many crammed into poorly sited and badly constructed megacities with populations in excess of 8 million people. Forty years ago New York and London topped the league table of cities, with populations, respectively, of 12 and 8.7 million.

In 2015, however, cities such as Mumbai (formerly Bombay, India), Dhaka (Bangladesh), Jakarta (Indonesia), and Mexico City will be firmly ensconced in the top ten: gigantic sprawling agglomerations of humanity with populations approaching or exceeding 20 million, and extremely vulnerable to storm, flood, and quake. A staggering 96 per cent of all deaths arising from natural hazards and environmental degradation occur in developing countries and there is currently no prospect of this falling. Indeed, the picture looks as if it might well deteriorate even further. With so many people shoehorned into ramshackle and dangerously exposed cities (many in coastal locations at risk from earthquakes, tsunamis, windstorms, and coastal floods) it can only be a matter of time before we see the first of a series of true mega disasters, with death tolls exceeding one million.

The picture I have painted is certainly bleak, but the reality may be even worse. Future rises in population and vulnerability will take place against a background of dramatic climate change, the like of which the planet has not experienced for maybe 10,000 years. The jury remains out on the precise hazard implications of the rapid warming expected over the next hundred years, but rises in sea level that may exceed 80 centimeters are forecast in the most recent (2001) report of the IPCC (Intergovernmental Panel on Climate Change). This will certainly increase the incidence and impact of storm surges and tsunamis and – in places – raise the level of coastal erosion. Other consequences of a temperature rise that could reach more than 6 degrees Celsius by the end of the century may include more extreme meteorological events such as hurricanes, tornadoes, and floods, greater numbers of landslides in mountainous terrain, and, eventually, even more volcanic eruptions.

So is the world as we know it about to end and, if so, how? A century from now will we be gasping for water in an increasingly roasting world or huddling around a few burning sticks, struggling to keep at bay the bitter cold of a cosmic winter?

Facts to contemplate

• During its earliest history, the Earth was covered in a magma ocean with temperatures – at 5,000 degrees Celsius – comparable with the surfaces of some of the cooler stars.

• Our planet’s great tectonic plates move at about the same rate that our fingernails grow.

• Around 1,400 earthquakes rock the planet every day.

• There may be 3,000 or more active or potentially active volcanoes, about 50 of which erupt every year.

• The tropics are battered each year by 40 or more hurricanes, typhoons, and cyclones.

• In 1556 a single earthquake in the Shensi province of China is estimated to have killed over 800,000 people.

• At least 15 million deaths in the last millennium are attributed to natural hazards.

• 96 per cent of all deaths from natural hazards and environmental degradation now occur in developing countries.

 

Most Populous Cities of the World

.

Rank

City*

Population

Year

1

Shanghai, China

17,836,133

2011c

2

Istanbul, Turkey

13,854,740

2012e

3

Karachi, Pakistan

12,991,000

2013c

4

Mumbai, India

12,478,447

2011c

5

Moscow, Russia

11,977,988

2013e

6

Manila, Philippines

11,953,140

2012c

7

São Paulo, Brazil

11,821,876

2013c

8

Beijing, China

11,716,000

2010c

9

Tianjin, China

11,090,314

2010c

10

Guangzhou, China

11,070,654

2010c

11

Delhi, India

11,007,835

2010c

12

Seoul, South Korea

10,442,426

2012c

13

Shenzhen, China

10,357,938

2010c

14

Jakarta, Indonesia

10,187,595

2012e

15

Tokyo, Japan

8,967,665

2010c

16

Mexico City, Mexico

8,873,017

2010c

17

Kinshasa, Democratic Republic of Congo

8,754,000

2010e

18

Bangalore, India

8,425,970

2011c

19

New York City, United States

8,336,697

2013e

20

London

8,308,369

2012e

 
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