Natural hazard
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A natural hazard[1] is a threat of a naturally occurring event that will have a negative effect on people or the environment. Many natural hazards are interrelated, e.g. earthquakes can cause tsunamis and drought can lead directly to famine. 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.
Geological hazards
Avalanche
An avalanche is a geophysical hazard a slide of a large snow (or rock) mass down a mountainside, caused when a buildup of snow is released down a slope, it is one of the major dangers faced in the mountains in winter. An avalanche is an example of a gravity current consisting of granular material. In an avalanche, lots of material or mixtures of different types of material fall or slide rapidly under the force of gravity. Avalanches are often classified by what they are made of.
Earthquake
An earthquake is a phenomenon that results from a sudden release of stored energy that radiates seismic waves. At the Earth's surface, earthquakes may manifest themselves by a shaking or displacement of the ground and sometimes tsunamis. Most of the world's earthquakes (90%, and 81% of the largest) take place in the 40,000-km-long, horseshoe-shaped zone called the circum-Pacific seismic belt, also known as the Pacific Ring of Fire, which for the most part bounds the Pacific Plate. Many earthquakes happen each day, few of which are large enough to cause significant damage.
Lahar
A lahar is a type of natural disaster closely related to a volcanic eruption, and involves a large amount of material, including mud, rock, and ash sliding down the side of the volcano at a rapid pace. These flows can destroy entire towns in seconds and kill thousands of people.
Sinkholes
A sinkhole is localized depression in the surface topography, usually caused by the collapse of a subterranean structure, such as a cave. Although rare, large sinkholes that develop suddenly in populated areas can lead to the collapse of buildings and other structures.
Volcanic eruption
A volcanic eruption is the point in which a volcano is active and releases its power, and the eruptions come in many forms. They range from daily small eruptions which occur in places like Kilauea in Hawaii, to megacolossal eruptions (where the volcano expels at least 1,000 cubic kilometers of material)] from supervolcanoes like Lake Taupo (26,500 years ago) and Yellowstone Caldera. 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. Some eruptions form pyroclastic flows, which are high-temperature clouds of ash and steam that can trial down mountainsides at speed exceeding an airliner.
Hydrological hazards
Flood
Floods are the result of prolonged rainfall from a storm, including thunderstorms, rapid melting of large amounts of snow, or rivers which swell from excess precipitation upstream and cause widespread damage to areas downstream, or less frequently the bursting of man-made dams or levees. Tropical cyclones can result in extensive flooding and storm surge.
Limnic eruption
Also referred to as a 'lake overturn', a limnic eruption is a rare type of natural disaster in which 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 CO2 displaces water. Scientists believe landslides, volcanic activity, or explosions can trigger such an eruption.
Whirlpool
A whirlpool is a swirling body of water usually produced by ocean tides. The vast majority of whirlpools are not very powerful. More powerful ones are more properly termed maelstroms. Vortex is the proper term for any whirlpool that has a downdraft. (Technically, these approximate to a 'free vortex', in which the tangential velocity (v) increases as the centre line is approached, so that the angular momentum (rv) is constant). Very small whirlpools can easily be seen when a bath or a sink is draining, but these are produced in a very different manner from those in nature. Smaller whirlpools also appear at the base of many waterfalls. In the case of powerful waterfalls, like Niagara Falls, these whirlpools can be quite strong. The most powerful whirlpools are created in narrow shallow straits with fast flowing water.
Maelstrom
Maelstroms are large tidal whirlpools. The largest known maelstrom is Moskstraumen off the Lofoten islands in Norway. Powerful whirlpools have killed unlucky seafarers, but their power tends to be exaggerated in fiction. Maelstroms can reach speeds of 20–40 km/h.
Seiche
A seiche is a standing wave in an enclosed or partially enclosed body of water. Seiches and seiche-related phenomena have been observed on lakes, reservoirs, bays and seas. The key requirement for formation of a seiche is that the body of water be at least partially bounded.
Tsunami
A tsunami is a wave of water caused by the displacement of a body of water. The word comes from Japanese words "tsu" meaning harbor and "nami" meaning wave (tsu+nami=harbor wave).
Tsunamis can be caused by submarine earthquakes as in the 2004 Indian Ocean earthquake (pictured), or by landslides such as the one which occurred at Lituya Bay, Alaska, or by two tectonic plates vibrating to cause a wave.
Meteotsunamis are caused by meteorological phenomena. A megatsunami is an informal term used to describe very large tsunamis. The largest waves are caused by very large landslides, such as a collapsing island, into a body of water. The highest tsunami ever recorded was estimated to be of 524 m (1742 ft) vertical run-up on July 9, 1958, in Lituya Bay, Alaska.
Climatic and atmospheric hazards
Blizzard
A blizzard is a severe winter storm icy and windy conditions characterized by low temperatures, strong winds, and heavy snow.
Drought
Drought is defined as an acute shortage of water and crop failure that results when the average rainfall is very less than the normal. A drought is an abnormally dry period when there is not enough water to support agricultural, urban or environmental water needs. Extended droughts can result in deaths by starvation or disease, and can result in wildfires. Scientists warn that global warming may result in more extensive droughts in coming years.
Hailstorm
A hailstorm is a natural hazard where a thunderstorm produces numerous hailstones which damage the location in which they fall. Hailstorms can be especially devastating to farm fields, ruining crops and damaging equipment.
Heat wave
A heat wave is a hazard characterized by heat which is considered extreme and unusual in the area in which it occurs. Heat waves are rare and require specific combinations of weather events to take place, and may include temperature inversions, katabatic winds, or other phenomena. There is potential for longer term events causing global warming, including stadial events (the opposite to glacial 'ice age' events), or through human induced climatic warming.
Cyclonic storms
Hurricane, tropical cyclone, and typhoon are different names for the same phenomenon: a cyclonic storm system that forms over the oceans. It is caused by evaporated water that comes off of the ocean and becomes a storm. The Coriolis Effect causes the storms to spin, and a hurricane is declared when this spinning mass of storms attains a wind speed greater than 74 mph (119 km/h). Hurricane is used for these phenomena in the Atlantic and eastern Pacific Oceans, tropical cyclone in the Indian, typhoon in the western Pacific.
Ice storm
An ice storm is a particular weather event in which precipitation falls as ice, due to atmosphere conditions.
Tornado
A tornado is a natural disaster resulting from a thunderstorm. Tornadoes are violent, rotating columns of air which can blow at speeds between 50 mph (80 km/h) and 300 mph (480 km/h), and possibly higher. Tornadoes can occur one at a time, or can occur in large tornado outbreaks associated with supercells or in other large areas of thunderstorm development. Waterspouts are tornadoes occurring over tropical waters in light rain conditions.
Climate change
Climate change is a long-term hazard which can increase or decrease the risk of other weather hazards, and also directly endangers property due to sea level rise and biological organisms due to habitat destruction.
Geomagnetic storm
Geomagnetic storms can disrupt or damage technological infrastructure, and disorient species with magnetoception.
Wildfire hazard
A wildfire is 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. Wildfires can also produce ember attacks, where floating embers set fire to buildings at a distance from the fire itself.
Disease
Disease is a natural hazard that can be enhanced by human factors such as urbanization or poor sanitation. Disease affecting multiple people can be termed an outbreak or epidemic.
In some cases, a hazard exists in that a man-made defense against disease could fail, for example through antibiotic resistance.
International campaigns
In 2000, the United Nations launched the International Early Warning Programme to address the underlying causes of vulnerability and to build disaster-resilient communities by promoting increased awareness of the importance of Disaster Risk Reduction as an integral component of sustainable development, with the goal of reducing human, economic and environmental losses due to hazards of all kinds (UN/ISDR, 2000). The 2006-2007 United Nations International Disaster Reduction Day theme is “Disaster reduction education begins in school”. The Foundation of Public Safety Professionals has launched an international campaign giving everybody a chance to have their say, thought their international open essay or documentary competition “Disaster Risk Reduction Education Begins at School”.
See also
- Act of God
- Risks to civilization, humans and planet Earth
- List of environmental disasters
- Ten Threats identified by the United Nations
- Emergency management
- Geohazard
- Civil defense
- Disaster relief
- Disaster risk reduction
- Standardized Natural Hazards Disclosure Statement
- Social vulnerability