Natural disaster

Natural disaster

A natural disaster is the effect of a natural hazard (e.g., flood, tornado, hurricane, volcanic eruption, earthquake, heatwave, or landslide). It leads to financial, environmental or human losses. The resulting loss depends on the vulnerability of the affected population to resist the hazard, also called their resilience.[1] This understanding is concentrated in the formulation: "disasters occur when hazards meet vulnerability."[2] Thus a natural hazard will not result in a natural disaster in areas without vulnerability, e.g. strong earthquakes in uninhabited areas.[3] The term natural has consequently been disputed because the events simply are not hazards or disasters without human involvement.[4] A concrete example of the division between a natural hazard and a natural disaster is that the 1906 San Francisco earthquake was a disaster, whereas earthquakes are a hazard. This article gives an introduction to notable natural disasters, refer to the list of natural disasters for a comprehensive listing.


Geological disasters


Notable avalanches include:


An earthquake is a sudden shake of the Earth's crust caused by the tectonic plates colliding. The vibrations may vary in magnitude. The underground point of origin of the earthquake is called the "focus". The point directly above the focus on the surface is called the"epicenter". Earthquakes by themselves rarely kill people or wildlife. It is usually the secondary events that they trigger, such as building collapse, fires, tsunamis (seismic sea waves) and volcanoes, that are actually the human disaster. Many of these could possibly be avoided by better construction, safety systems, early warning and evacuation planning.Earthquakes are caused by the discharge of energy accumulated along geologic fault.

Some of the most significant earthquakes in recent times include:

Volcanic eruptions (S.C.S)

Volcanoes can cause widespread destruction and consequent disaster through several ways. The effects include the volcanic eruption itself that may cause harm following the explosion of the volcano or the fall of rock. Second, lava may be produced during the eruption of a volcano. As it leaves the volcano, the lava destroys many buildings and plants it encounters. Third, volcanic ash generally meaning the cooled ash - may form a cloud, and settle thickly in nearby locations. When mixed with water this forms a concrete-like material. In sufficient quantity ash may cause roofs to collapse under its weight but even small quantities will harm humans if inhaled. Since the ash has the consistency of ground glass it causes abrasion damage to moving parts such as engines. The main killer of humans in the immediate surroundings of a volcanic eruption is the pyroclastic flows, which consist of a cloud of hot volcanic ash which builds up in the air above the volcano and rushes down the slopes when the eruption no longer supports the lifting of the gases. It is believed that Pompeii was destroyed by a pyroclastic flow. A lahar is a volcanic mudflow or landslide. The 1953 Tangiwai disaster was caused by a lahar, as was the 1985 Armero tragedy in which the town of Armero was buried and an estimated 23,000 people were killed.

A specific type of volcano is the supervolcano. According to the Toba catastrophe theory 70 to 75 thousand years ago a super volcanic event at Lake Toba reduced the human population to 10,000 or even 1,000 breeding pairs creating a bottleneck in human evolution. It also killed three quarters of all plant life in the northern hemisphere. The main danger from a supervolcano is the immense cloud of ash which has a disastrous global effect on climate and temperature for many years.

Hydrological disasters


A flood is an overflow of an expanse of water that submerges land.[1] The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water.[2] In the sense of "flowing water", the word may also be applied to the inflow of the tide. Flooding may result from the volume of water within a body of water, such as a river or lake, which overflows or breaks levees, with the result that some of the water escapes its usual boundaries.[3] While the size of a lake or other body of water will vary with seasonal changes in precipitation and snow melt, it is not a significant flood unless such escapes of water endanger land areas used by man like a village, city or other inhabited area.

The Limpopo River, in southern Mozambique, during the 2000 Mozambique flood

Some of the most notable floods include:

  • The Huang He (Yellow River) in China floods particularly often. The Great Flood of 1931 caused between 800,000 and 4,000,000 deaths.
  • The Great Flood of 1993 was one of the most costly floods in United States history.
  • The 1998 Yangtze River Floods, in China, left 14 million people homeless.
  • The 2000 Mozambique flood covered much of the country for three weeks, resulting in thousands of deaths, and leaving the country devastated for years afterward.
  • The 2005 Mumbai floods which destroyed 1094 people.
  • The 2010 Pakistan floods, damaged crops and the infrastructure, while claiming many lives.

Tropical cyclones can result in extensive flooding and storm surge, as happened with:

Limnic eruptions

A cow suffocated by gases from Lake Nyos after a limnic eruption

A limnic eruption occurs when a gas, usually CO2, suddenly erupts from deep lake water, posing the threat of suffocating wildlife, livestock and humans. Such an eruption may also cause tsunamis in the lake as the rising gas displaces water. Scientists believe landslides, volcanic activity, or explosions can trigger such an eruption. To date, only two limnic eruptions have been observed and recorded:

  • In 1984, in Cameroon, a limnic eruption in Lake Monoun caused the deaths of 37 nearby residents.
  • At nearby Lake Nyos in 1986 a much larger eruption killed between 1,700 and 1,800 people by asphyxiation.


The tsunami caused by the December 26, 2004, earthquake strikes Ao Nang, Thailand.

Tsunamis can be caused by undersea earthquakes as the one caused in Ao Nang, Thailand, by the 2004 Indian Ocean Earthquake, or by landslides such as the one which occurred at Lituya Bay, Alaska.

Meteorological disasters

Young steer after a blizzard, March 1966


Blizzards are severe winter storms characterized by low temperature, strong winds, and heavy snow. The difference between a blizzard and a snow storm is the strength of the wind. To be a considered a blizzard, the storm must have winds in excess of 35 miles per hour, it should reduce the visibility to 1/4 miles, and must last for a prolonged period of 3 hours or more. Ground blizzards require high winds to stir up snow that has already fallen, rather than fresh snowfall. Blizzards have a negative impact on local economics and can terminate the visibility in regions where snowfall is rare.

Significant blizzards include:

Cyclonic storms

Cyclone, tropical cyclone, hurricane, and typhoon are different names for the same phenomenon a cyclonic storm system that forms over the oceans. The deadliest hurricane ever was the 1970 Bhola cyclone; the deadliest Atlantic hurricane was the Great Hurricane of 1780 which devastated Martinique, St. Eustatius and Barbados. Another notable hurricane is Hurricane Katrina which devastated the Gulf Coast of the United States in 2005.


Well-known historical droughts include:

  • 1900 India killing between 250,000 and 3.25 million.
  • 1921-22 Soviet Union in which over 5 million perished from starvation due to drought
  • 1928-30 northwest China resulting in over 3 million deaths by famine.
  • 1936 and 1941 Sichuan Province China resulting in 5 million and 2.5 million deaths respectively.
  • As of 2006, states of Australia including South Australia, Western Australia, New South Wales, Northern Territory and Queensland had been under drought conditions for five to ten years. The drought is beginning to affect urban area populations for the first time. With the majority of the country under water restrictions.
  • In 2006, Sichuan Province China experienced its worst drought in modern times with nearly 8 million people and over 7 million cattle facing water shortages.
  • 12-year drought that was devastating southwest Western Australia, southeast South Australia, Victoria and northern Tasmania was "very severe and without historical precedent".


Hailstorms are rain drops that have formed together into ice. A particularly damaging hailstorm hit Munich, Germany, on July 12, 1984, causing about 2 billion dollars in insurance claims.

Heat waves

The worst heat wave in recent history was the European Heat Wave of 2003.

A summer heat wave in Victoria, Australia, created conditions which fuelled the massive bushfires in 2009. Melbourne experienced three days in a row of temperatures exceeding 40°C with some regional areas sweltering through much higher temperatures. The bushfires, collectively known as "Black Saturday", were partly the act of arsonists.

The 2010 Northern Hemisphere summer resulted in severe heat waves, which killed over 2,000 people. It resulted in hundreds of wildfires which causing widespread air pollution, and burned thousands of square miles of forest.


A tornado (often referred to as a twister or, erroneously, a cyclone) is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. Tornadoes come in many shapes and sizes, but are typically in the form of a visible condensation funnel, whose narrow end touches the earth and is often encircled by a cloud of debris and dust. Most tornadoes have wind speeds less than 110 miles per hour (177 km/h), are approximately 250 feet (80 m) across, and travel a few miles (several kilometers) before dissipating. The most extreme can attain wind speeds of more than 300 mph (480 km/h), stretch more than two miles (3 km) across, and stay on the ground for dozens of miles (more than 100 km).[1][2][3]


Wildfires are an uncontrolled fire burning in wildland areas. Common causes include lightning and drought but wildfires may also be started by human negligence or arson. They can be a threat to those in rural areas and also wildlife.

Notable cases of wildfires were the 1871 Peshtigo Fire in the United States, which killed at least 1700 people, and the 2009 Victorian bushfires in Australia.

Health disasters


The A H5N1 virus, which causes Avian influenza

An epidemic is an outbreak of a contractible disease that spreads at a rapid rate through a human population. A pandemic is an epidemic whose spread is global. There have been many epidemics throughout history, such as Black Death. In the last hundred years, significant pandemics include:

  • The 1918 Spanish flu pandemic, killing an estimated 50 million people worldwide
  • The 1957-58 Asian flu pandemic, which killed an estimated 1 million people
  • The 1968-69 Hong Kong flu pandemic
  • The 2002-3 SARS pandemic
  • The AIDS pandemic, beginning in 1959
  • The H1N1 Influenza (Swine Flu) Pandemic 2009-2010

Other diseases that spread more slowly, but are still considered to be global health emergencies by the WHO include:

  • XDR TB, a strain of tuberculosis that is extensively resistant to drug treatments
  • Malaria, which kills an estimated 1.6 million people each year
  • Ebola hemorrhagic fever, which has claimed hundreds of victims in Africa in several outbreaks


In modern times, famine has hit Sub-Saharan Africa the hardest, although the number of victims of modern famines is much smaller than the number of people killed by the Asian famines of the 20th century.

Space disasters

Fallen trees caused by the Tunguska meteoroid of the Tunguska event in June 1908.

Impact events

One of the largest impact events in modern times was the Tunguska event in June 1908.

Solar flares

A solar flare is a phenomenon where the sun suddenly releases a great amount of solar radiation, much more than normal. Some known solar flares include:

  • An X20 event on August 16, 1989[6]
  • A similar flare on April 2, 2001[6]
  • The most powerful flare ever recorded, on November 4, 2003, estimated at between X40 and X45[7]
  • The most powerful flare in the past 500 years is believed to have occurred in September 1859[8]

Gamma ray burst

Gamma ray bursts are the most powerful explosions that occur in the universe. They release an enormous amount of energy in milliseconds or longing for ten seconds. They release the same energy that the Sun would have given in its whole life or even more than that. Gamma ray bursts are not rare events because they occur about once every day and are detected by telescopes both on Earth and in space. Mostly large masses of stars, bigger than the Sun, can produce a GRB. A GRB of distances nearer than 8000 light years may cause a concern to life on Earth. Mainly Wolf-Rayet stars WR 104 can produce GRB. Astronomers do believe that the Ordovician–Silurian extinction, the second most destructive extinction on Earth, might have been due to a GRB.

Protection by international law

International law, for example Geneva Conventions defines International Red Cross and Red Crescent Movement the Convention on the Rights of Persons with Disabilities, requires that "States shall take, in accordance with their obligations under international law, including international humanitarian law and international human rights law, all necessary measures to ensure the protection and safety of persons with disabilities in situations of risk, including the occurrence of natural disaster."[9] And further United Nations Office for the Coordination of Humanitarian Affairs is formed by General Assembly Resolution 44/182.

See also

SanFranHouses06.JPG Disasters portal


  1. ^ G. Bankoff, G. Frerks, D. Hilhorst (eds.) (2003). Mapping Vulnerability: Disasters, Development and People. ISBN ISBN 1-85383-964-7. 
  2. ^ B. Wisner, P. Blaikie, T. Cannon, and I. Davis (2004). At Risk - Natural hazards, people's vulnerability and disasters. Wiltshire: Routledge. ISBN ISBN 0-415-25216-4. 
  3. ^ Luis Flores Ballesteros. "What determines a disaster?" 54 Pesos Sep 2008:54 Pesos 11 Sep 2008. <>
  4. ^ D. Alexander (2002). Principles of Emergency planning and Management. Harpended: Terra publishing. ISBN ISBN 1-903544-10-6. 
  5. ^ ^ "USGS Earthquake Details". United States Geological Survey. Retrieved February 27, 2010
  6. ^ a b "Sun Unleashes Record Superflare, Earth Dodges Solar Bullet". ScienceDaily. April 4, 2011. Retrieved 2011-8-27. 
  7. ^ "Biggest Solar Flare ever recorded". National Association for Scientific and Cultural Appreciation. 2004. Retrieved 2011-8-27. 
  8. ^ "A Super Solar Flare". NASA. May 6, 2008. Retrieved 2011-8-27. 
  9. ^ Article 11 of the Convention on the Rights of Persons with Disabilities

External links

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