Huge Disasters

Most Common Disasters

Floods

A flood is an overflow of an expanse of water that submerges land, a deluge. In the sense of "flowing water", the word is applied to the inflow of the tide, as opposed to the outflow or "ebb".
It is usually due to the volume of water within a body of water, such as a river or lake, exceeding the total capacity of the body, and as a result some of the water flows or sits outside of the normal perimeter of the body. It can also occur in rivers, when the strength of the river is so high it flows right out of the river channel , usually at corners or meanders. These of course, are not applicable in such instances as sea flooding.
The word comes from the Old English flod, a word common to Teutonic languages, compare German Flut, Dutch vloed from the same root as is seen in flow, float.
The term "The Flood" usually refers to the great Universal Deluge described in Genesis and is treated at Deluge.

Causes
Floods from the sea can cause overflow or overtopping of flood defences like dikes as well as flattening of dunes or bluffs. Land behind the coastal defence may be inundated or experience damage. A flood from sea may be caused by a heavy storm (storm surge), a high tide, a tsunami, or a combination thereof. As many urban communities are located near the coast this is a major threat around the world. Many rivers flow over relatively flat land border on broad flood plains. When heavy the deposition of silt on the rich farmlands and can result in their eventual depletion. The annual cycle of flood and farming was of great significance to many early farming cultures, most famously to the ancient Egyptians of the Nile river and to the Mesopotamians of the Tigris and Euphrates rivers.
A flood occurs when an area of land, usually low-lying, is covered with water. The worst floods usually occur when a river overflows its banks. An example of this is the January 1999 Queensland floods, which swamped south-eastern Queensland. Floods happen when soil and vegetation cannot absorb all the water. The water then runs off the land in quantities that cannot be carried in stream channels or kept in natural ponds or man-made reservoirs.
Periodic floods occur naturally on many rivers, forming an area known as the flood plain. These river floods usually result from heavy rain, sometimes combined with melting snow, which causes the rivers to overflow their banks. A flood that rises and falls rapidly with little or no advance warning is called a flash flood. Flash floods usually result from intense rainfall over a relatively small area, as happened in 2007 with the Sudan floods. Coastal areas are occasionally flooded by high tides caused by severe winds on ocean surfaces, or by tsunami waves caused by undersea earthquakes. There are often many causes for a flood.
Monsoon rainfalls can cause disastrous flooding in some equatorial countries, such as Bangladesh; Hurricanes have a number of different features which, together, can cause devastating flooding. One is the storm surge (sea flooding as much as 8 metres high) caused by the leading edge of the hurricane when it moves from sea to land. Another is the large amounts of precipitation associated with hurricanes. The eye of a hurricane has extremely low pressure, so sea level may rise a few metres in the eye of the storm. This type of coastal flooding occurs regularly in Bangladesh. In Europe floods from sea may occur as a result from heavy Atlantic storms, pushing the water to the coast. Especially in combination with high tide this can be damaging.
Under some rare conditions associated with heat waves, flash floods from quickly melting mountain snow have caused loss of property and life.
Undersea earthquakes, eruptions of island volcanos that form a caldera, (such as Thera or Krakatau) and marine landslips on continental shelves may all engender a tidal wave called a tsunami that causes destruction to coastal areas. See the tsunami article for full details of these marine floods.
Floods are the most frequent type of disaster worldwide. Thus, it is often difficult or impossible to obtain insurance policies which cover destruction of property due to flooding, since floods are a relatively predictable risk. A flood can also be caused by blocked sewage pipes and waterways, such as the Jakarta flood.

Typical effects

Primary effects
Physical damage- Structures such as buildings get damaged due to flood water. Landslides can also take place.
Casualties- People and livestock die due to drowning. It can also lead to epidemics and diseases.

Secondary effects
Water supplies- Contamination of water. Clean drinking water becomes scarce.
Diseases- Unhygienic conditions. Spread of water-bourne diseases
Crops and food supplies- Shortage of food crops can be caused due to loss of entire harvest.

Tertiary/long-term effects
Economic- Economic hardship, due to e.g. temporary decline in tourism, rebuilding costs, food shortage leading to price increase etc, especially to the poor.

Flood defences, planning, and management
In western countries, rivers prone to floods are often carefully managed. Defences such as levees, bunds, reservoirs, and weirs are used to prevent rivers from bursting their banks. Coastal flooding has been addressed in Europe with coastal defences, such as sea walls and beach nourishment.
London is protected from flooding by a huge mechanical barrier across the River Thames, which is raised when the water level reaches a certain point (see Thames Barrier).
Venice has a similar arrangement, although it is already unable to cope with very high tides. The defenses of both London and Venice will be rendered inadequate if sea levels continue to rise.
The largest and most elaborate flood defenses can be found in the Netherlands, where they are referred to as Delta Works with the Oosterscheldedam as its crowning achievement. These works were built in response to the North Sea flood of 1953 of the south western part of the Netherlands. The Dutch had already built one of the worlds largest dams in the north of the country: the Afsluitdijk (closing occurred in 1932).
Currently the Saint Petersburg Flood Prevention Facility Complex is to be finished by 2008, in Russia, to protect Saint Petersburg from storm surges. It also has a main traffic function, as it completes a ring road around St Petersburg. 11 dams extend for 25.4 kilometres and stand eight metres above water level.
The New Orleans Metropolitan Area, 35% of which sits below sea level, is protected by hundreds of miles of levees and flood gates. This system failed catastrophically during Hurricane Katrina in the City Proper and in eastern sections of the Metro Area, resulting in the innundation of approximately 50% of the Metropolitan area, ranging from a few inches to twenty feet in coastal communities.
In an act of successful flood prevention, the Federal Government of the United States offered to buy out flood-prone properties in the United States in order to prevent repeated disasters after the 1993 flood across the Midwest. Several communities accepted and the government, in partnership with the state, bought back 25,000 properties which the converted into wetlands. These wetlands act as a sponge in storms and in 1995, when the floods returned, the government didn't have to spend a dime in those areas.

Earthquakes

An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. Earthquakes are recorded with a seismometer, also known as a seismograph. The moment magnitude of an earthquake is conventionally reported, or the related and mostly obsolete Richter magnitude, with magnitude 3 or lower earthquakes being mostly imperceptible and magnitude 7 causing serious damage over large areas. Intensity of shaking is measured on the modified Mercalli scale.
At the Earth's surface, earthquakes manifest themselves by a shaking and sometimes displacement of the ground. When a large earthquake epicenter is located offshore, the seabed sometimes suffers sufficient displacement to cause a tsunami. The shaking in earthquakes can also trigger landslides and occasionally volcanic activity.
In its most generic sense, the word earthquake is used to describe any seismic event-whether a natural phenomenon or an event caused by humans-that generates seismic waves. Earthquakes are caused mostly by rupture of geological faults, but also by volcanic activity, landslides, mine blasts, and nuclear experiments.
An earthquake's point of initial rupture is called its focus or hypocenter. The term epicenter means the point at ground level directly above this.

Naturally occurring earthquakes
Most naturally occurring earthquakes are related to the tectonic nature of the Earth. Such earthquakes are called tectonic earthquakes. The Earth's lithosphere is a patchwork of plates in slow but constant motion caused by the release to space of the heat in the Earth's mantle and core. The heat causes the rock in the Earth to flow on geological timescales, so that the plates move slowly but surely. Plate boundaries lock as the plates move past each other, creating frictional stress. When the frictional stress exceeds a critical value, called local strength, a sudden failure occurs. The boundary of tectonic plates along which failure occurs is called the fault plane. When the failure at the fault plane results in a violent displacement of the Earth's crust, energy is released as a combination of radiated elastic strain seismic waves, frictional heating of the fault surface, and cracking of the rock, thus causing an earthquake. This process of gradual build-up of strain and stress punctuated by occasional sudden earthquake failure is referred to as the Elastic-rebound theory. It is estimated that only 10 percent or less of an earthquake's total energy is radiated as seismic energy. Most of the earthquake's energy is used to power the earthquake fracture growth or is converted into heat generated by friction. Therefore, earthquakes lower the Earth's available elastic potential energy and raise its temperature, though these changes are negligible compared to the conductive and convective flow of heat out from the Earth's deep interior.
The majority of tectonic earthquakes originate at depths not exceeding tens of kilometers. In subduction zones, where older and colder oceanic crust descends beneath another tectonic plate, Deep focus earthquakes may occur at much greater depths (up to seven hundred kilometers). These seismically active areas of subduction are known as Wadati-Benioff zones. These are earthquakes that occur at a depth at which the subducted lithosphere should no longer be brittle, due to the high temperature and pressure. A possible mechanism for the generation of deep focus earthquakes is faulting caused by olivine undergoing a phase transition into a spinel structure.
Earthquakes also often occur in volcanic regions and are caused there, both by tectonic faults and by the movement of magma in volcanoes. Such earthquakes can serve as an early warning of volcanic eruptions.
Sometimes a series of earthquakes occur in a sort of earthquake storm, where the earthquakes strike a fault in clusters, each triggered by the shaking or stress redistribution of the previous earthquakes. Similar to aftershocks but on adjacent segments of fault, these storms occur over the course of years, and with some of the later earthquakes as damaging as the early ones. Such a pattern was observed in the sequence of about a dozen earthquakes that struck the North Anatolian Fault in Turkey in the 20th century, the half dozen large earthquakes in New Madrid in 1811-1812, and has been inferred for older anomalous clusters of large earthquakes in the Middle East and in the Mojave Desert.

Size and frequency of occurrence
Small earthquakes occur nearly constantly around the world in places like California and Alaska in the U.S., as well as in Chile, Peru, Indonesia, Iran, the Azores in Portugal, New Zealand, Greece and Japan. Large earthquakes occur less frequently, the relationship being exponential; for example, roughly ten times as many earthquakes larger than magnitude 4 occur in a particular time period than earthquakes larger than magnitude 5. In the (low seismicity) United Kingdom, for example, it has been calculated that the average recurrences are:
an earthquake of 3.7 - 4.6 every year
an earthquake of 4.7 - 5.5 every 10 years
an earthquake of 5.6 or larger every 100 years.
The number of seismic stations has increased from about 350 in 1931 to many thousands today. As a result, many more earthquakes are reported than in the past because of the vast improvement in instrumentation (not because the number of earthquakes has increased). The USGS estimates that, since 1900, there have been an average of 18 major earthquakes (magnitude 7.0-7.9) and one great earthquake (magnitude 8.0 or greater) per year, and that this average has been relatively stable. In fact, in recent years, the number of major earthquakes per year has actually decreased, although this is likely a statistical fluctuation. More detailed statistics on the size and frequency of earthquakes is available from the USGS.
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. Massive earthquakes tend to occur along other plate boundaries, too, such as along the Himalayan Mountains.

Effects/impacts of earthquakes
There are many effects of earthquakes including, but not limited to the following:

Shaking and ground rupture
Shaking and ground rupture are the main effects created by earthquakes, principally resulting in more or less severe damage to buildings or other rigid structures. The severity of the local effects depends on the complex combination of the earthquake magnitude, the distance from epicenter, and the local geological and geomorphological conditions, which may amplify or reduce wave propagation. The ground-shaking is measured by ground acceleration.
Specific local geological, geomorphological, and geostructural features can induce high levels of shaking on the ground surface even from low-intensity earthquakes. This effect is called site or local amplification. It is principally due to the transfer of the seismic motion from hard deep soils to soft superficial soils and to effects of seismic energy focalization owing to typical geometrical setting of the deposits.
Ground rupture is a visible breaking and displacement of the earth's surface along the trace of the fault, which may be of the order of few metres in the case of major earthquakes. Ground rupture is a major risk for large engineering structures such as dams, bridges and nuclear power stations and requires careful mapping of existing faults to identify any likely to break the ground surface within the life of the structure.

Landslides and avalanches
Earthquakes can cause landslides and avalanches, which may cause damage in hilly and mountainous areas.

Fires
Following an earthquake, fires can be generated by break of the electrical power or gas lines. In the event of water mains rupturing and a loss of pressure, it may also become difficult to stop the spread of a fire once it has started.

Soil liquefaction
Soil liquefaction occurs when, because of the shaking, water-saturated granular material temporarily loses its strength and transforms from a solid to a liquid. Soil liquefaction may cause rigid structures, as buildings or bridges, to tilt or sink into the liquefied deposits.

Tsunamis
Undersea earthquakes and earthquake-triggered landslides into the sea, can cause Tsunamis. See, for example, the 2004 Indian Ocean earthquake.

Human impacts
Earthquakes may result in disease, lack of basic necessities, loss of life, higher insurance premiums, general property damage, road and bridge damage, and collapse of buildings or destabilization of the base of buildings which may lead to collapse in future earthquakes.

Preparation for earthquakes
Earthquake preparedness
Household seismic safety
HurriQuake nail (for resisting hurricanes and earthquakes)
Seismic retrofit
Seismic hazard
Mitigation of seismic motion
Earthquake prediction

Specific fault articles

Major earthquakes

Pre-20th century
Pompeii (62).
Aleppo Earthquake (1138).
Basel earthquake (1356). Major earthquake that struck Central Europe in 1356.
Carniola earthquake (1511). A major earthquake that shook a large portion of South-Central Europe. Its epicenter was around the town of Idrija, in today's Slovenia. It caused great damage to structures all over Carniola, including Ljubljana, and minor damage in Venice, among other cities.
Shaanxi Earthquake (1556). Deadliest known earthquake in history, estimated to have killed 830,000 in China.
Dover Straits earthquake of 1580 (1580).
Dubrovnik earthquake (1667). Disastrous earthquake in Dubrovnik, Croatia killed about 3/5 of the population.
The great Sicilian earthquake (1693). As many as 100,000 may have died.
Cascadia Earthquake (1700).
Kamchatka earthquakes (1737 and 1952).
Lisbon earthquake (1755), one of the most destructive and deadly earthquakes in history, killing between 60,000 and 100,000 people and causing a major tsunami that affected parts of Europe, North Africa and the Caribbean.
Calabria earthquake (1783). Series of 6 earthquakes in Calabria, Italy killed 50,000.
New Madrid Earthquake (1811), and another tremor (1812) that also struck the small Missouri town, was reportedly the strongest ever in North America and made the Mississippi River temporarily change its direction and permanently altered its course in the region.
Fort Tejon Earthquake (1857). Estimated Richter Scale above 8, said the strongest earthquake in Southern California history.
1872 Lone Pine earthquake (1872). Might been strongest ever measured in California with an estimated Richter Scale of 8.1 said seismologists.
Charleston earthquake (1886). Largest earthquake in the southeastern United States, killed 100.
Ljubljana earthquake (14. IV. 1895), a series of powerful quakes that ultimately had a vital impact on the city of Ljubljana, being a catalyst of its urban renewal.
Assam earthquake of 1897 (1897). Large earthquake that destroyed all masonry structures, measuring more than 8 on the Richter scale.

20th century
San Francisco Earthquake (1906). Between 7.7 and 8.3 magnitudes; killed approximately 3,000 people and caused around $400 million in damage; most devastating earthquake in California and U.S. history.
Messina Earthquake (1908). Killed about 60,000 people.
Gansu earthquake (1920). Killed 200,000 in Gansu province, China.
Great Kant? earthquake (1923). On the Japanese island of Honsh?, killing over 140,000 in Tokyo and environs.
1931 Hawke's Bay earthquake. Occurred in the Hawkes Bay in the North Island of New Zealand leaving 256 dead.
1933 Long Beach earthquake
1935 Balochistan earthquake at Quetta, Pakistan measuring 7.7 on the Richter scale. Anywhere from 30,000 to 60,000 people died
1939 Erzincan earthquake at Erzincan, Turkey measuring 7.9 on the Richter scale.
Ashgabat earthquake (1948). Earthquake in Ashgabat, Soviet Union measuring 7.3 on the Richter scale killed over 110,000 (2/3 the population of the city).
Assam earthquake of 1950 (1950). Earthquake in Assam, India measures 8.6M.
Kamchatka earthquakes (1952 and 1737), measuring >9.0.
Great Kern County earthquake (1952). This was second strongest tremor in Southern California history, epicentered 60 miles North of Los Angeles. Major damage in Bakersfield, California and Kern County, California, while it shook the Los Angeles area.
Quake Lake (1959) Formed a lake in southern Montana, USA
Great Chilean Earthquake (1960). Biggest earthquake ever recorded, 9.5 on Moment magnitude scale, and generated tsunamis throughout the Pacific ocean.
1960 Agadir earthquake, Morocco with around 15,000 casualties.
1963 Skopje earthquake, measuring 6.1 on the Richter scale kills 1,800 people, leaves another 120,000 homeless, and destroys 80% of the city.
Good Friday Earthquake (1964) In Alaska, it was the second biggest earthquake recorded, measuring 9.2M. and generated tsunamis throughout the Pacific ocean.
Ancash earthquake (1970). Caused a landslide that buried the town of Yungay, Peru; killed over 40,000 people.
Sylmar earthquake (1971). Caused great and unexpected destruction of freeway bridges and flyways in the San Fernando Valley, leading to the first major seismic retrofits of these types of structures, but not at a sufficient pace to avoid the next California freeway collapse in 1989.
Managua earthquake (1972), which killed more than 10,000 people and destroyed 90% of the city. The earthquake took place on December 23, 1972 at midnight.
Friuli earthquake (1976), Which killed more than 2.000 people in Northeastern Italy on the 6th of May
Tangshan earthquake (1976). The most destructive earthquake of modern times. The official death toll was 255,000, but many experts believe that two or three times that number died.
Guatemala 1976 earthquake (1976). Causing 23,000 deaths, 77,000 injuries and the destruction of more than 250,000 homes.
Coalinga, California earthquake (1983). 6.5 on the Richter scale on a section of the San Andreas Fault. Six people killed, downtown Coalinga, California devastated and oil field blazes.
Great Mexican Earthquake (1985). Killed over 6,500 people, according to official Mexican government reports, but as many as 30,000 people are thought to have been killed (they disappeared and never reappeared after the initial Earthquakes).
Great San Salvador Earthquake (October 10, 1986). Killed over 1,500 people.
Whittier Narrows earthquake (1987).
Newcastle, NSW Australia earthquake 1989 {FLEMO}
Armenian earthquake (1988). Killed over 25,000.
Loma Prieta earthquake (1989). Severely affecting Santa Cruz, San Francisco, San Jose and Oakland in California. This is also called the World Series Earthquake. It struck as Game 3 of the 1989 World Series was just getting underway at Candlestick Park in San Francisco. Revealed necessity of accelerated seismic retrofit of road and bridge structures.
Iran Earthquake (1990). 7.7 on the Richter scale. Killed over 35,000 in Gilan Province, southwest of Caspian sea.
Luzon Earthquake (1990). On 16 July 1990, an earthquake measuring 7.7 on the Richter scale struck the island of Luzon, Philippines.
Landers, California earthquake (1992). Serious damage in the small town of Yucca Valley, California and was felt across 10 states in Western U.S. Another tremor measured 6.4 struck 3 hours later and felt across Southern California.
August 1993 Guam Earthquake, measuring 8.2 on the Richter scale and lasting 60 seconds.
Northridge, California earthquake (1994). Damage showed seismic resistance deficiencies in modern low-rise apartment construction.
Sakhalin earthquake (1995). Measuring 7.6 on the Richter scale, killing over 2,000 people in Sakhalin, Russia.
Great Hanshin earthquake (1995). Killed over 6,400 people in and around Kobe, Japan.
Afghanistan earthquake (1998). 6.9 on the Richter scale. Some 125 villages were damaged and 4000 people killed.
Athens earthquake (1999). 5.9 on the Richter scale, it hit Athens on September 7. Epicentered 10 miles north of the Greek capital, it claimed 143 lives.
Chi-Chi earthquake (1999) Also called the 921 earthquake. Struck Taiwan on September 21, 1999. Over 2,000 people killed, destroyed or damaged over ten thousand buildings. Caused world computer prices to rise sharply.
Armenia, Colombia (1999) 6.2 on the Richter scale, Killed over 2,000 in the Colombian Coffee Grown Zone.
1999 ?zmit earthquake measuring 7.4 on the Richter scale and killed over 17,000 in northwestern Turkey.
Hector Mine earthquake (1999). 7.1 on the Richter scale, epicentered 30 miles east of Barstow, California, widely felt in California and Nevada.
1999 D?zce earthquake at D?zce, Turkey measuring 7.2 on the Richter scale.
Baku earthquake (2000).

21st century
Nisqually Earthquake (2001).
El Salvador earthquakes (2001). 7.9 (13 January) and 6.6 (13 February) magnitudes, killed more than 1,100 people.
Gujarat Earthquake (26 January 2001).
Hindu Kush earthquakes (2002). Over 1.100 killed.
Molise earthquake (2002) 26 killed.
Bam Earthquake (2003). Over 40,000 people are reported dead.
Parkfield, California earthquake (2004). Not large (6.0), but the most anticipated and intensely instrumented earthquake ever recorded and likely to offer insights into predicting future earthquakes elsewhere on similar slip-strike fault structures.
Ch?etsu earthquake (2004).
Sumatra-Andaman Earthquake (26 December 2004). By some estimates, the second largest earthquake in recorded history (estimates of magnitude vary between 9.1 and 9.3). Epicentered off the coast of the Indonesian island of Sumatra, this massive earthquake triggered a series of gigantic tsunamis that smashed onto the shores of a number of nations, causing 230,000 fatalities.
Sumatran (Nias) Earthquake (2005).
Fukuoka earthquake (2005).
Northern Chile Earthquake (2005). 7.9 (13 June). Killed only 15 people, but left many poor families homeless.
Kashmir earthquake (2005) (also known as the Great Pakistan earthquake). Killed over 79,000 people; and many more injured.
Lake Tanganyika earthquake (2005).
May 2006 Java earthquake (2006).
July 2006 7.7 magnitude Java earthquake which triggered tsunamis (2006).
October 2006 6.6 magnitude Kona, Hawaii earthquake (2006).
November 2006 8.1 magnitude north of Japan (2006).
December 26, 2006, 7.2 magnitude, southwest of Taiwan (2006).
Sumatra Earthquakes March 06, 2007, 6.4 and 6.3 magnitude, Sumatra, Indonesia (2007).
March 25, 2007, 6.9 magnitude, off the west coast of Honsh?, Japan (2007).
April 1, 2007, 8.1 magnitude, Solomon Islands (2007).
2007 Guatemala Earthquake 6.7 magnitude (2007)
July 16, 2007, 6.6 magnitude, Niigata prefecture, Japan (2007)
2007 Peru earthquake 8.0 magnitude, August 15 (2007)
September 2007 Sumatra earthquakes 8.0 magnitude September 12 (2007)
November 14, 2007, 7.7 magnitude, Antofagasta, Chile (2007).
November 29, 2007, 7.4 magnitude,Caribbean Sea (2007)
2007 Gisborne Earthquake December 20, 2007 6.8magnitude, Gisborne, New Zealand

Earthquakes in mythology and religion
In Norse mythology, earthquakes were explained as the violent struggling of the god Loki. When Loki, god of mischief and strife, murdered Baldr, god of beauty and light, he was punished by being bound in a cave with a poisonous serpent placed above his head dripping venom. Loki's wife Sigyn stood by him with a bowl to catch the poison, but whenever she had to empty the bowl the poison would drip on Loki's face, forcing him to jerk his head away and thrash against his bonds, causing the earth to tremble.
In Greek mythology, Poseidon was the god of earthquakes.
In Christian mythology, certain saints were invoked as patrons against earthquakes, including Saint Gregory Thaumaturgus, Saint Agatha, Saint Francis Borgia, and Saint Emygdius.

Wind storms

A storm is any disturbed state of an astronomical body's atmosphere, especially affecting its surface, and strongly implying severe weather. It may be marked by strong wind, thunder and lightning (a thunderstorm), heavy precipitation, such as ice (ice storm), or wind transporting some substance through the atmosphere (as in a dust storm, snowstorm, hailstorm, etc).

Formation
Storms are created when a center of low pressure develops, with a system of high pressure surrounding it. This combination of opposing forces can create winds and result in the formation of storm clouds, such as the cumulonimbus. Small, localized areas of low pressure can form from hot air rising off hot ground, resulting in smaller disturbances such as dust devils and whirlwinds.

Types
There are many varieties and names for storms.
Ice Storm - Ice storms are one of the most dangerous forms of winter weather. When surface temperatures are below freezing, but a thick layer of above freezing air remains aloft above ground level, rain can fall into the freezing layer and freeze upon impact into a glaze. In general, 8 millimeters (1/4 in) of accumulation is all that is required, especially in combination with breezy conditions, to start downing power lines as well as tree limbs. Ice storms also make unheated road surfaces too slick to drive upon. Ice storms can vary in time range from hours to days and can cripple both small towns and large urban centers alike.
Blizzard - There are varying definitions for blizzards, both over time and by location. In general, a blizzard is accompanied by gale-force winds, heavy snow (accumulating at a rate of at least 5 centimeters (2 in) per hour), and very cold conditions (below approximately -10 degrees Celsius or 14 F). As of late, the temperature criteria has fallen out of the definition across the United States
Snowstorm - A heavy fall of snow accumulating at a rate of more than 5 centimeters (2 in) per hour that lasts several hours. Snow storms, especially ones with a high liquid equivalent and breezy conditions, can down tree limbs, cut off power, and paralyze travel over a large region.
Ocean Storm - Storm conditions out at sea are defined as having sustained winds of 48 knots (55 mph or 90 km/h) or greater. Usually just referred to as a storm, these systems can sink vessels of all types and sizes out at sea.
Firestorm - Firestorms are conflagrations which attain such intensity that they create and sustain their own wind systems. It is most commonly a natural phenomenon, created during some of the largest bushfires, forest fires, and wildfires. The Peshtigo Fire is one example of a firestorm. Firestorms can also be deliberate effects of targeted explosives such as occurred as a result of the aerial bombings of Dresden and Tokyo during World War II. Nuclear detonations almost invariably generate firestorms
Dust devil - a small, localized updraft of rising air.
Windstorm - a severe weather condition indicated by high winds and with little or no rain, like European windstorm.
Squall - sudden onset of wind increase of at least 16 knots (30 km/h) or greater sustained for at least one minute.
Gale - An extratropical storm with sustained winds between 34-48 knots (39-55 mph or 63-90 km/h).
Thunderstorm - A thunderstorm is a type of storm that generates lightning and the attendant thunder. It is normally accompanied by heavy precipitation. Thunderstorms occur throughout the world, with the highest frequency in tropical rainforest regions where there are conditions of high humidity and temperature along with atmospheric instability. These storms occur when high levels of condensation form in a volume of unstable air that generates deep, rapid, upward motion in the atmosphere. The heat energy creates powerful rising air currents that swirl upwards to the tropopause. Cool descending air currents produce strong downdraughts below the storm. After the storm has spent its energy, the rising currents die away and downdraughts break up the cloud. Individual storm clouds can measure 2-10 km across.
Tropical Cyclone - A tropical cyclone is a storm system with a closed circulation around a centre of low pressure, fueled by the heat released when moist air rises and condenses. The name underscores its origin in the tropics and their cyclonic nature. Tropical cyclones are distinguished from other cyclonic storms such as nor'easters and polar lows by the heat mechanism that fuels them, which makes them "warm core" storm systems.
Tropical cyclones form in the oceans if the conditions in the area are favorable, and depending on their strength and location, there are various terms by which they are called, such as tropical depression, tropical storm, hurricane and typhoon.
Hailstorm - a type of storm that precipitates chunks of ice. Hailstorms usually occur during regular thunder storms. While most of the hail that precipitates from the clouds is fairly small and virtually harmless, there have been cases of hail greater than 2 inches diameter that caused much damage and injuries.
Tornado - A tornado is a violent, destructive wind storm occurring on land. Usually its appearance is that of a dark, funnel-shaped cyclone. Often tornadoes are preceded by a thunderstorm and a wall cloud. They are often called the most destructive of storms, and while they form all over the world, the interior of the United States the most prone area, especially throughout Tornado Alley.

Classification
A strict meteorological definition of a terrestrial storm is a wind measuring 10 or higher on the Beaufort scale, meaning a wind speed of 24.5 m/s (89 km/h, 55 mph) or more; however, popular usage is not so restrictive. Storms can last anywhere from 12 to 200 hours, depending on season and geography. The east and northeast storms are noted for the most frequent repeatability and duration, especially during the cold period. Big terrestrial storms alter the oceanographic conditions that in turn may affect food abundance and distribution: strong currents, strong tides, increased siltation, change in water temperatures, overturn in the water column, etc.

Extraterrestrial storms
Storms are not unique to Earth; other heavenly bodies with a sufficient atmosphere (gas giants in particular) also undergo stormy weather. A famous example is the Great Red Spot on Jupiter. Though technically a hurricane, it is larger than the earth and has been raging for at least 340 years, when it was observed by astronomer Galileo Galilei. Neptune also had its own lesser known Great Dark Spot.
In September 1994 Hubble telescope using Wide Field Planetary Camera 2 imaged the storms on Saturn, generated by upwelling of warmer air, similar to a terrestrial thunderhead. The east-west extent of the same-year storm was equal to the diameter of Earth. The storm was observed earlier in September 1990 and acquired the name Dragon Storm.

Notable storms in art and culture
According to the Bible, a giant storm sent by God flooded the Earth. Noah and his family and the animals entered the Ark, and "the same day were all the fountains of the great deep broken up, and the windows of heaven were opened, and the rain was upon the earth forty days and forty nights." The flood covered even the highest mountains to a depth of more than twenty feet, and all creatures died; only Noah and those with him on the Ark were left alive.
In Greek mythology there were several gods of storms: Briareos, the god of sea storms; Aigaios, a god of the violent sea storms; and Aiolos, keeper of storm-winds, squalls and tempests.
William Shakespeare's play The Tempest (1611) was based on the following incident. Sir Thomas Gates, future governor of Virginia, was on his way to England from Jamestown, Virginia. On Saint James Day while between Cuba and the Bahamas a hurricane raged for nearly two days. Though one of the small vessels in the fleet sank to the bottom of the Florida Straits, seven of the remaining vessels reached Virginia within several days after the storm. The flagship of the fleet, known as Sea Adventure, disappeared and was presumed lost. A small bit of fortune befell the ship and her crew when they made landfall on Bermuda. The vessel was damaged on a surrounding coral reef, but all aboard survived for nearly a year on the island. The British colonists claimed the island and quickly settled Bermuda. In May 1610, they set forth for Jamestown, this time arriving at their destination.
The Romantic seascape painters J. M. W. Turner and Ivan Aivazovsky created some of the most lasting impressions of the sublime and stormy seas that are firmly imprinted on the popular mind. Turner's representations of powerful natural forces reinvented the traditional seascape during the first half of the nineteenth century. Upon his travels to Holland, he took note of the familiar large rolling waves of the English seashore transforming into the sharper, choppy waves of a Dutch storm. A characteristic example of Turner's dramatic seascape is The Slave Ship of 1840. Aivazovsky left several thousand turbulent canvases in which he increasingly eliminated human figures and historical background to focus on such essential elements as light, sea, and sky. His grandiose Ninth Wave (1850) is an ode to human daring in the face of the elements.

Forest / scrub fires

Wildfires are common in many places around the world, including much of the vegetated areas of Australia as well as the veld in the interior and the fynbos in the Western Cape of South Africa. The forested areas of the United States and Canada are also susceptible to wildfires. The climates are sufficiently moist to allow the growth of trees, but feature extended dry, hot periods. Fires are particularly prevalent in the summer and fall, and during droughts when fallen branches, leaves, and other material can dry out and become highly flammable. Some suggest that global warming has been increasing the intensity and frequency of droughts in many areas, creating more intense and frequent wildfires. Wildfires are also common in grasslands and scrublands.
Wildfires tend to be most common and severe during years of drought and occur on days of strong winds. With extensive urbanization of wildlands, these fires often involve destruction of suburban homes located in the wildland urban interface, a zone of transition between developed areas and undeveloped wildland.
Today it is generally accepted that wildfires are a natural part of the ecosystem of numerous wildlands, where some plants have evolved to survive fires by a variety of strategies (from possessing reserve shoots that sprout after a fire, to fire-resistant seeds), or even encourage fire (for example eucalypts contain flammable oils in their leaves) as a way to eliminate competition from less fire-tolerant species. Smoke, charred wood, and head are common fire cues that stimulate the germination of seeds (Keeley and Fotheringham 1997). In 2004, researchers discovered that exposure to smoke from burning plants actually promotes germination in other types of plants by inducing the production of the orange butenolide.
However, many ecosystems are suffering from too much fire such as the chaparral in southern California and lower elevation deserts in the American Southwest. The increased fire frequency in these areas has caused the elimination of native plant communities and have replaced them with non-native weeds (Keeley 1995, Zedler 1995). These weeds create a positive feedback loop, increasing fire frequency even more (Brooks, et al. 2004).
On occasions, wildfires have caused large-scale damage to private or public property, destroying many homes and causing deaths, particularly when they have reached urban-fringe communities. Wildfires are extremely dangerous, but some are purposely caused.

Designations and terminology
In the U.S., there are a number of specific terms that are applicable to such fires. A Wildland fire is "any non-structure fire, that occurs in the wildland", and there are three distinct types of wildland fire which are defined:
Wildfire is "an unplanned, unwanted wildland fire, including unauthorized human-caused fires, escaped wildland fire use events, escaped prescribed fire projects and all other wildland fires where the objective is to put the fire out."
Wildland fire use is "the application of the appropriate management response to naturally ignited wildland fires to accomplish specific resource management objectives in predefined designated areas outlined in Fire Management Plans."
Prescribed fire is "any fire ignited by management actions to meet specific objectives."

Behavior
The evaporation of water in plants is balanced by water absorbed from the soil. Below this threshold, the plants dry out and under stress release the flammable gas ethylene. A consequence of a long hot and dry period is therefore that the air contains flammable essences and plants are drier and highly flammable.
The propagation of the fire has three mechanisms:
"crawling" fire: the fire spreads via low level vegetation (e.g., bushes)
"crown" fire: a fire that "crowns" (spreads to the top branches of trees) can spread at an incredible pace through the top of a forest. Crown fires can be extremely dangerous to all inhabitants underneath, as they may spread faster than they can be outrun, particularly on windy days. (see Firestorm)
"jumping" or "spotting" fire: burning branches and leaves are carried by the wind and start distant fires; the fire can thus "jump" over a road, river, or even a firebreak. In Australian bushfires, spot fires have been documented "up to 10 km [aprox. 6 miles] ahead of the fire front" (Billing 1983).
The Nevada Bureau of Land Management identifies several different wildfire behaviors. For example, extreme fire behavior includes wide rates of spread, prolific crowning and/or spotting, the presence of fire whirls, or a strong convection column. Extreme wildfires behave erratically and unpredictably.
In southern California, under the influence of Santa Ana winds, wildfires can move at tremendous speeds, up to 40 miles (60 km) in a single day, consuming up to 1,000 acres (4 km?) per hour. Dense clouds of burning embers push relentlessly ahead of the flames crossing firebreaks without pause.
The powerful updraft caused by a large wildfire will draw in air from surrounding areas. These self-generated winds can lead to a phenomenon known as a firestorm.
French models of wildfires dictate that a fire's front line will take on the characteristic shape of a pear; the major axis being aligned with the wind. In the case of the fires in southeastern France, the speed of the fire is estimated to be 3% to 8% of the speed of the wind, depending on the conditions (density and type of vegetation, slope). Other models predict an elliptical shape when the ground is flat and the vegetation is homogeneous...
Another type of wildfire is the smouldering fire. It involves the slow combustion of surface fuels without generating flame, spreading slowly and steadily. It can linger for days or weeks after flaming has ceased, resulting in potential large quantities of fuel consumed and becoming a global source of emissions to the atmosphere. It heats the duff and mineral layers, affecting the roots, seeds and plant stems at the ground.
Since 1997, in Kalimantan and East Sumatra, Indonesia, there is a type of continuous smouldering fire on the peat bogs that burns underground for years without any supply of oxygen. The underground fire ignited new forest fire each year during dry season.

Prevention
For many decades the policy of the United States Forest Service was to suppress all fires. This policy was epitomized by the mascot Smokey Bear and was also the basis of parts of the movie Bambi. The policy began to be questioned in the 1960s, when it was realized that no new Giant Sequoia had been grown in the forests of California, because fire is an essential part of their life cycle. This produced the policy of controlled burns to reduce underbrush. This clears much of the undergrowth through forest and woodland areas, making travel and hunting much easier while reducing the risk of dangerous high-intensity fires caused by many years of fuel buildup.
The previous policy of absolute fire suppression in the United States has resulted in the buildup of fuel in some ecosystems such as dry ponderosa pine forests. However, this concept has been misapplied in a "one-size-fits-all" application to other ecosystems such as California chaparral. Fire suppression in southern California has had very little impact over the past century. The amount of land burned in 6 southern California counties has been relatively unchanged. In fact, fire frequency has been increasing dramatically over the past century in lock step with population growth. Urbanization can also result in fuel buildup and devastating fires, such as those in Los Alamos, New Mexico, East Bay Hills, within the California cities of Oakland and Berkeley between October 19 and 22, 1991, all over Colorado in 2002, and throughout southern California in October 2003. Homes designed without considering the fire prone environment in which they are built have been the primary reason for the catastrophic losses experienced in wildfires.
On average, wildfires burn 4.3 million acres (17,000 km?) in the United States annually. In recent years the federal government has spent $1 billion a year on fire suppression. 2002 was a record year for fires with major fires in Arizona, California, Colorado, and Oregon.
The risk of major wildfires can be reduced partly by a reduction or alteration of fuel present. In wild land, reduction can be accomplished by either conducting controlled burns, deliberately setting areas ablaze under less dangerous weather when conditions are less volatile or physical fuel removal by removing some trees as is conducted in many American forests. Alteration of fuels, which involves reducing the structure of fuel ladders, can be accomplished by hand crews with chain saws or by large mastication equipment that shreds trees and vegetation to a mulch. Such techniques are best used within the wild land/urban interface where communities connect with wild open space. Prescribed burns in the back country, away from human habitations, are not particularly effective in preventing large fires. All the large catastrophic fires in the United States have been wind driven events where the amount of fuel (trees, shrubs, etc.) has not been the most important factor in fire spread.
People living in fire-prone areas typically take a variety of precautions, including building their homes out of flame-resistant materials, reducing the amount of fuel near the home or property (including firebreaks, their own miniature control lines, in effect), and investing in their own firefighting equipment.
Rural farming communities are rarely threatened directly by wildfire. These types of communities are usually located in large areas of cleared, usually grazed, land, and in the drought conditions present in wildfire years there is often very little grass left on such grazed areas. Hence the risk is minimized. However, urban fringes have spread into forested areas, for example in Sydney and Melbourne, and communities have literally built themselves in the middle of highly flammable forests. In Cape Town, the city lies on the fringe of the Table Mountain National Park. These communities are at high risk of destruction in bush fires, and should take extra precautions.
There are quite a few US states, Canadian provinces and many countries around the world that still use Fire lookouts as a means of early detection of forest fires. Some nations still using this system besides the US and Canada include: Australia, Israel, Latvia, Poland, France, Germany, Italy, Spain, Portugal, Brazil, Uruguay.

Wildfire detection
Fast and effective detection is a key factor in wildfire fighting. Recently, there have been significant efforts to create automatic solutions for early wildfire detection. An integrated approach is best, based on a practical combination of different detection systems depending on wildfire risk and the size of the area.
A careful GIS data analysis will suggest how to divide the area in sub-categories based on different risk level and human presence (which imply a higher wildfire risk and a need for earlier intervention).
A small high risk area (thick vegetation, strong human presence or close to critical urban area) could be monitored using a local sensor network.
Although it is a relatively new approach, it seems to be the only solution able to penetrate thick vegetation and guarantee early detection without false alarms, as well as detecting crawling wildfires. The main limitation of this technology is its high cost which at this time limit its application to small areas.
A larger medium risk area could be monitored by infrared scanning towers.
These have a disadvantage in that they are "blind" to obstacles like thick vegetation, therefore they can miss crawling wildfires for a long time and have still frequent false alarms, but are the best approach to wider areas. Smoke and hot-air-column scanners have the advantage of "looking higher", making them able to locate a wildfire of any size, but do not perform well during strong wind (which is, ironically, the riskiest situation).
Satellite and aero monitoring can provide a wider view and may be sufficient to monitor very large and low risk areas.
Many studies have been done in this field, some producing interesting results. Limitations include the long distance to satellites in geostationary orbits and the short window of observation time for satellites in polar orbits.

Fire suppression
The vast majority of wildfires are suppressed before they grow out of control. In 2004, firefighters contained more than 99% of all new wildfires during initial action. That record was achieved despite the volatile conditions that prevailed in much of that year's fire season. However, the wildfires that escaped initial actions and grew above 300 acres (1.2 km?) accounted for the bulk of acres burned, and nearly 75% of all suppression expenditures.
Wildland fire suppression is a unique aspect of firefighting. Most fire-prone areas have large firefighter services to help control bushfires. As well as the water-spraying fire apparatus most commonly used in urban firefighting, bushfire services use a variety of alternative techniques. Typically, forest fire fighting organizations will use large crews of 20 or more people who travel in trucks to the fire. These crews use heavier equipment to construct firebreaks, and are the mainstay of most firefighting efforts. Other personnel are organized into fast attack teams typically consisting of 5-8 people. These fast attack teams are helicoptered into smaller fires or hard to reach areas as a preemptive strike force. They use portable pumps to douse small fires and chainsaws to construct firebreaks or helicopter landing pads if more resources are required. Hand tools are commonly used to construct firebreaks and remove fuels around the perimeter of the fire to halt its spread, including shovels, rakes, and the pulaski, a tool unique to wildland firefighting. In the eastern United States, portable leaf blowers are sometimes used. In the western United States, large fires often become extended campaigns, and temporary fire camps are constructed to provide food, showers, and rest to fire crews. These large fires are often handled by 20 person hand crews, sometimes known as hotshot crews, specially organized to travel to large fires.
Fast attack teams, such as the Boise District BLM Helitack crew, are often considered the elite of firefighting forces, as they sometimes deploy in unusual ways. If the fire is on a particularly steep hill or in a densely wooded area, they may rappel or fast-rope down from helicopters. If the fire is extremely remote, firefighters known as smokejumpers may parachute into site from fixed-wing aircraft. In addition to the aircraft used for deploying ground personnel, firefighting outfits often possess helicopters and water bombers specially equipped for use in aerial firefighting. These aircraft can douse areas that are inaccessible to ground crews and deliver greater quantities of water and/or flame retardant chemicals. Managing all of these various resources over such a large area in often very rugged terrain is extremely challenging, and often the Incident Command System is used. As such, each fire will have a designated Incident Commander who oversees and coordinates all the operations on the fire. This Incident Commander is ultimately responsible for the safety of the firefighters and for the success of firefighting efforts.
Large fires are of such a size that no conceivable firefighting service could attempt to douse the whole fire directly, and so alternative techniques are used. In alternative approaches, firefighters attempt to control the fire by controlling the area that it can spread to, by creating "control lines", which are areas that contain no combustible material. These control lines can be produced by physically removing fuel (for instance, with a bulldozer), or by "backfiring", in which small, low-intensity fires are started, using a device such as the driptorch, or pyrotechnic flares known as "fusees", to burn the flammable material in a (hopefully) controlled way. These may then be extinguished by firefighters or, ideally, directed in such a way that they meet the main fire front, at which point both fires run out of flammable material and are thus extinguished.
Unfortunately, such methods can fail in the face of wind shifts causing fires to miss control lines or to jump straight over them (for instance, because a burning tree falls across a line, burning embers are carried by the wind over the line, or burning tumbleweeds cross the line).
The actual goals of firefighters vary. Protection of life (those of both the firefighters and "civilians") is given top priority, then private property according to economic and social value and also to its "defendibility" (for example, more effort will be expended on saving a house with a tile roof than one with a wooden-shake roof). In very severe, large fires, this is sometimes the only possible action. Protecting houses is regarded as more important than, say, farming machinery sheds, although firefighters, if possible, try to keep fires off farmland to protect stock and fences (steel fences are destroyed by the passage of fire, as the wire is irreversibly stretched and weakened by it). Preventing the burning of publicly owned forested areas is generally of least priority, and, indeed, it is quite common (in Australia, at least) for firefighters to simply observe a fire burn towards control lines through forest rather than attempt to put it out more quickly; it is, after all, a natural process. On any incident, ensuring the safety of firefighters takes priority over fire suppression. When arriving on a scene a fire crew will establish a safety zone(s), escape routes, and designate lookouts (known by the acronym LCES, for lookouts, communications, escape routes, safety zones). This allows the firefighters to engage a fire with options for a retreat should their current situation become unsafe. In addition all fire suppression activities are based from an "anchor point" (such as lake, rock slide or road). From an anchor point firefighters can work to contain a wild land fire without the fire outflanking them. As a last resort, all wild land firefighters carry a fire shelter. In an unescapable burnover situation the shelter will provide limited protection from radiant and convective heat, as well as superheated air. As such a greater emphasis is placed on safety and preventing entrapment, and is reinforced with a list of 10 fire orders and 18 "watch out situations" for firefighters to be aware of, which warn of potentially dangerous conditions.
In North America, the belief that fire suppression has substantially reduced the average annual area burned is widely held by resource managers and is often thought to be self-evident. However, this belief has been the focus of vocal debate in the scientific literature.
A new material called "gel" (made from super-absorbent polymer) is used in California, USA for fighting forest fire. Water is soaked up by the gel and stored in layers of tiny bubbles. The gel can protect tree/house for longer time than ordinary water, because it gets boiled by the fire one layer at a time.

Atmospheric effects
Most of the Earth's weather and air pollution reside in the troposphere, the part of the atmosphere that extends from the surface of the planet to a height of between 8 and 13 kilometers. A severe thunderstorm or pyrocumulonimbus in the area of a large wildfire can have its vertical lift enhanced to boost smoke, soot and other particles as high as the lower stratosphere (Wang, 2003).
Previously, it was thought that most particles in the stratosphere came from volcanoes or were generated by high-flying aircraft. Collection of air samples from the stratosphere in 2003 led to detection of carbon monoxide and other gases related to combustion at a level 30 times higher than can be accounted for by commercial aircraft.
Satellite observation of smoke plumes from wildfires revealed that the plumes could be traced intact for distances exceeding 5,000 kilometers. This observation suggests that the plumes were in the stratosphere above weather conditions that would have brought the plume back to earth.
Atmospheric models suggest that these concentrations of sooty particles could increase absorption of incoming solar radiation during winter months by as much as 15% (Baumgardner, et al., 2003).
The massive forest fire in Indonesia (1997/1998) released approx. 2.57 gigatonnes of Carbon Dioxide into the atmosphere (source: Nature magazine, November 2002). During 1997-1998, the total amount of Carbon Dioxide released to the atmosphere was 6 gigatonnes. Most of the Carbon Dioxide gas is released by the continuous underground smouldering fire on the peat bogs.
After the end of a wildfire, houses sometimes experience an ember attack - an onslaught of burning twigs or branches that can ignite a fire in the house.

Wildfires can also be beneficial
Fire is sometimes essential for forest regeneration, or provides tangible benefits for local communities. In other cases it destroys forests and has dire social and economic consequences.
Forest fires are a natural part of ecosystems in many, but not all, forest types: in boreal and dry tropical forests for example they are a frequent and expected feature, while in tropical moist forests they would naturally be absent or at least rare enough to play a negligible role in ecology.

Statistics
Every year, the burnt surface represents about:
France: 211 km?, 52,140 acres, 0.04% of the territory
Portugal:
1991 : 1,820 km?, 449,732 acres, i.e. 2% of the territory
2003 : 4,249 km?, 1.05 million acres, i.e. 4.6% of the territory; 20 deaths ;
2004 : 1,205 km?, 297,836 acres, i.e. 1.3% of the territory
2005 : 2,864 km?, 707,668 acres, i.e. 3.1% of the territory; 17 deaths;
2006 : 724 km?, 178,904 acres, i.e. 0.8% of the territory; 10 deaths;
United States: 17,400 km?, 4.3 million acres i.e. 0.18% of the territory
Indonesia. Sources: before 1997 from Indonesian Environmental Impact Management Agency (BAPEDAL) and Canadian International Development Agency (CIDA) - Collaborative Environmental Project in Indonesia (CEPI). 1997/1998 from Asian Development Bank (ADB). From 1999: Indonesian Ministry of Forestry.
1982 and 1983: 36,000 km? (8.9 million acres)
1987: 492 km? (121,880 acres).
1991: 1,189 km? (293,761 acres).
1994: 1,618 km? (399,812 acres).
1997 and 1998: 97,550 km? (24.1 million acres) - from ADB.
1999: 440.90 km? (108,949 acres).
2000: 82.55 km? ( 20,399 acres).
2001: 143.51 km? ( 35,462 acres).
2002: 366.91 km? ( 90,665 acres).
2003: 37.45 km? ( 9,254 acres).
2004: 139.91 km? ( 34,573 acres).
2005: 133.28 km? ( 32,934 acres).

Notable wildfires
Kursha-2, a wildfire killed 1,200 in the Soviet Union
The Milford Flat Fire which burned in 2007 in Utah is statistically the largest fire burning in Utah's history. At the time, Governor Jon Huntsman, Jr. stated that it is the biggest fire burning in the world. This fire burned 363,052 acres before it was fully contained.
The 2003 Okanagan Mountain Park Fire was started by a lightning strike near Rattlesnake Island in Okanagan Mountain Park in British Columbia, Canada, during one of the driest summers in the past decade. The final size of the firestorm was over 250 square kilometres (61,776 acres). 60 fire departments, 1,400 armed forces troops and 1,000 forest fire fighters took part in controlling the fire, but were largely helpless in stopping the disaster.
The Yellowstone National Park Fire of 1988 burned well over 793,880 acres (321,271 ha) before the winter snows put out the flames. (See: Yellowstone fires of 1988)
One of the largest known wild fires, was the Great Fire of 1910, that burned in Montana and Idaho.
The Zaca Fire burned Los Padres NF, CA. It burned 240,207 acres. It is the 2nd largest recorded fire in California.
Siege of 1987 Refers to a complex of fires in northern California and southern Oregon that burned a total of about 650,000 acres. These fires were started by a large lightning storm in late August. The storm started roughly 1600 new fires, most caused by dry lightning. Firefighting efforts continued into October, before the majority of the fires were controlled.
McNally Fire Sequoia NF burned roughly 151,000 acres in 2002, and is the largest wildfire recorded in the forest's history.
The 2003 Canberra bushfires infringed on the Australian capital itself. A firestorm raced through Canberra suburbs on January 18, 2003 and damaged or destroyed 431 homes.
In 2004, approximately 6.5 million acres burned in Alaska, in the state's largest recorded fire season. Over 500,000 acres burned in the Boundary Fire north of Fairbanks.
The 2007 Greek fires were some of the deadliest in world history, killing at least 64 people in Peloponnese and Evia.
The 2007 Southern California wildfires, burning an estimated 500,000 acres of land (in the San Diego and Malibu areas), with almost 900,000 people evacuated from the area.

Non-natural disasters

Man-made disasters
Disasters having an element of human intent, negligence, error or the ones involving the failure of a system are called man-made disasters. Man-made hazards are in turn categorised as technological or sociological. Technological hazards are results of failure of technology, such as engineering failures, transport accidents or environmental disasters. Sociological hazards have a strong human motive, such as crime, stampedes, riots and war.

Disaster Risk Reduction (DRR) is a term used for a large and growing body of work, bridging amongst many others the humanitarian relief, development aid sectors, risk management, and climate change.

Definition
Disaster risk reduction refer to a wide sector of work on disaster management including: mitigation, prevention, risk reduction, preparedness, and vulnerabilities. The common definition of the UNISDR & UNDP for disaster risk reduction is:

Context
Only 4% of the estimated $10 billion in annual humanitarian assistance is devoted to prevention and yet every dollar spent on risk reduction saves between $5 and $10 in economic losses from disasters.

Major International Conferences & Workshops
The World Conference on Disaster Reduction (WCDR) was held in Kobe, Japan in January 2005, only days after the 2004 Indian Ocean earthquake. The Conference was to take stock of progress in disaster risk reduction accomplished since the Yokohama Conference of 1994 and to make plans for the next ten years. The key outcome of this conference was the Hyogo Framework for Action.
The International Disaster Reduction Conference (IDRC) was held in Davos, Switzerland in August 2006.
The UNISDR Global Platform for Disaster Risk Reduction held its first session from 5-7 June 2007 in Geneva, Switzerland.

Major International Agreements & Funding Loci
The key outcome of the WCDR was the Hyogo Framework for Action : building the resilience of nations and communities to disasters (HFA).
The UNISDR Global Facility for Disaster Reduction and Recovery (GFDRR) is a major initiative launched in September 2006 through a partnership between the World Bank and ISDR to support national, regional and global capacities in reducing disaster risk, particularly in low and middle-income countries. A progress report on GFDRR accomplishments to date in support of the implementation of Hyogo Framework for Action is now available here.

Sector leaders
Some of the leaders in the sector include:
UNISDR, formerly IDNDR - Terry Jeggle
ProVention Consortium - Margaret Arnold
The International Federation of Red Cross and Red Crescent Societies - Antony Spalton
The Emergency Capacity Building (ECB) Project .
UNDP - Joanne Burke (CADRI), Andrew Maskrey, Maxx Dilley, & Fenella Frost (BCPR)
The World Bank - Saroj Jha (GFDRR-Global Facility for Disaster Reduction and Recovery)
The BOND UK DRR Working Group
The InterAction Risk Reduction Working Group - Susan Romanski Mercy Corps & Rebecca Schurer (American Red Cross)
Tearfund - Marcus Oxley
ActionAid - Roger Yates & Yasmin McDonnell
Department for International Development (DFID), UK - Olivia Coghlan
Global Risk Identification Program (GRIP) - Carlos Villacis

Droughts

A drought is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average precipitation. It can have a substantial impact on the ecosystem and agriculture of the affected region. Although droughts can persist for several years, even a short, intense drought can cause significant damage and harm the local economy.

Implications
Drought is a normal, recurring feature of the climate in most parts of the world. Having adequate drought mitigation strategies in place can greatly reduce the impact. Recurring or long-term drought can bring about desertification. Recurring droughts in the Horn of Africa have created grave ecological catastrophes, prompting massive food shortages, still recurring. To the north-west of the Horn, the Darfur conflict in neighboring Sudan, also affecting Chad, was fueled by decades of drought; combination of drought, desertification and overpopulation are among the causes of the Darfur conflict, because the Arab Baggara nomads searching for water have to take their livestock further south, to land mainly occupied by non-Arab farming peoples.
According to a UN climate report, the Himalayan glaciers that are the sources of Asia's biggest rivers - Ganges, Indus, Brahmaputra, Yangtze, Mekong, Salween and Yellow - could disappear by 2035 as temperatures rise. Approximately 2.4 billion people live in the drainage basin of the Himalayan rivers. India, China, Pakistan, Bangladesh, Nepal and Myanmar could experience floods followed by droughts in coming decades. Drought in India affecting the Ganges is of particular concern, as it provides drinking water and agricultural irrigation for more than 500 million people.
In 2005, parts of the Amazon basin experienced the worst drought in 100 years. A 23 July 2006 article reported Woods Hole Research Center results showing that the forest in its present form could survive only three years of drought. Scientists at the Brazilian National Institute of Amazonian Research argue in the article that this drought response, coupled with the effects of deforestation on regional climate, are pushing the rainforest towards a "tipping point" where it would irreversibly start to die. It concludes that the rainforest is on the brink of being turned into savanna or desert, with catastrophic consequences for the world's climate. According to the WWF, the combination of climate change and deforestation increases the drying effect of dead trees that fuels forest fires.
Paradoxically, some proposed short-term solutions to global warming also carry with them increased chances of drought.

Causes
Generally, rainfall is related to the amount of water vapour in the atmosphere, combined with the upward forcing of the air mass containing that water vapour. If either of these are reduced, the result is drought.
Factors include:
Above average prevalence of high pressure systems
Winds carrying continental, rather than oceanic air masses (ie. reduced water content)
El Nino (and other oceanic temperature cycles)
Deforestation
Some speculate that global warming will have a substantial impact on agriculture throughout the world, and especially in developing nations.

Consequences
Periods of drought can have significant environmental, economic and social consequences. The most common consequences include:
Death of livestock.
Reduced crop yields.
Wildfires, such as Australian bushfires, are more common during times of drought.
Shortages of water for industrial users.
Desertification
Dust storms, when drought hits an area suffering from desertification and erosion
Malnutrition, dehydration and related diseases.
Famine due to lack of water for irrigation.
Social unrest.
Mass migration, resulting in internal displacement and international refugees.
War over natural resources, including water and food.
Reduced electricity production due to insufficient available coolant
Snakes have been known to emerge and snakebites become more common.
The effect varies according to vulnerability. For example, subsistence farmers are more likely to migrate during drought because they do not have alternative food sources. Areas with populations that depend on subsistence farming as a major food source are more vulnerable to drought-triggered famine. Drought is rarely if ever the sole cause of famine; socio-political factors such as extreme widespread poverty play a major role. Drought can also reduce water quality, because lower water flows reduce dilution of pollutants and increase contamination of remaining water sources.

Stages of drought
As a drought persists, the conditions surrounding it gradually worsen and its impact on the local population gradually increases. Droughts go through three stages before their ultimate cessation :
Meteorological drought is brought about when there is a prolonged period with less than average precipitation. Meteorological drought usually precedes the other kinds of drought.
Agricultural droughts are droughts that affect crop production or the ecology of the range. This condition can also arise independently from any change in precipitation levels when soil conditions and erosion triggered by poorly planned agricultural endeavors cause a shortfall in water available to the crops. However, in a traditional drought, it is caused by an extended period of below average precipitation.
Hydrological drought is brought about when the water reserves available in sources such as aquifers, lakes and reservoirs falls below the statistical average. Like an agricultural drought, this can be triggered by more than just a loss of rainfall. For instance, Kazakhstan was recently awarded a large amount of money by the World Bank to restore water that had been diverted to other nations from the Aral Sea under Soviet rule . Similar circumstances also place their largest lake, Balkhash, at risk of completely drying out.

Drought mitigation strategies
Desalination of sea water for irrigation or consumption.
Drought monitoring - Continuous observation of rainfall levels and comparisons with current usage levels can help prevent man-made drought. For instance, analysis of water usage in Yemen has revealed that their water table (underground water level) is put at grave risk by over-use to fertilize their Khat crop. Careful monitoring of moisture levels can also help predict increased risk for wildfires, using such metrics as the Keetch-Byram Drought Index or Palmer Drought Index.
Land use - Carefully planned crop rotation can help to minimize erosion and allow farmers to plant less water-dependent crops in drier years.
Rainwater harvesting - Collection and storage of rainwater from roofs or other suitable catchments.
Recycled water - Former wastewater (sewage) that has been treated and purified for reuse.
Transvasement - Building canals or redirecting rivers as massive attempts at irrigation in drought-prone areas.
Water restrictions - Water use may be regulated (particularly outdoors). This may involve regulating the use of sprinklers, hoses or buckets on outdoor plants, the washing of motor vehicles or other outdoor hard surfaces (including roofs and paths), topping up of swimming pools, and also the fitting of water conservation devices inside the home (including shower heads, taps and dual flush toilets).
Cloud seeding - an artificial technique to induce rainfall.

Extreme temperatures

Temperature extremes are the highest and lowest temperatures recorded in specific regions. Normally the instrumentation in place would be inadequate to measure the extreme accurately, but discussion of media hypes is a popular hobby.
There are various weather record events on earth for various categories. Only outdoor climatic temperatures are recorded; temperatures recorded inside forest fires, for example, would not be included. Additionally, only temperatures recorded four feet (1.2 metres) or higher above the ground, and in the shade, are admissible, as ground temperatures in many areas are much hotter than air temperatures. One inch above the ground, temperatures can exceed 90 degrees Celsius (194 degrees Fahrenheit) in the deserts. The extreme, naturally occurring, temperature is probably inside lightning, where 28,000 degreeC is exceeded.
The Z machine at Sandia National Laboratories has reached temperatures in excess of 2 gigakelvins.
Large parts of the Sahara, the Middle East and India have had temperatures above 50 degreeC, as well as Mexicali in Mexico and in the Australian Desert (50.6).

Current extremes
The world's temperature extremes are:
The hottest temperature measured reliably was 56.7 degreeC (134 degreeF) in Death Valley, California. The record temperature of 57.7 degreeC (135.9 degreeF), recorded in Al 'Aziziyah, Libya on 13 September 1922, has been discredited and the 56.7 degreeC recorded at the Death valley was recorded without a proper shelter and the instrument was too close to the ground.
-89.2 degreeC (-128.5 degreeF), recorded on 21 July 1983 in Vostok, a Russian Antarctic research station located at the center of the East Antarctic Ice Sheet. Vostok Station is located within the Australian Antarctic Territory

Avalanches / landslides

An avalanche is a high-velocity flow of snow down a mountainside. Avalanches are among the biggest dangers in the mountains for both life and property.
Many factors contribute to avalanches. Loose snow avalanches occur when the weight of the snowpack exceeds the shear strength within it, and are most common on steeper terrain. In fresh, loose snow the release is usually at a point and the avalanche then gradually widens down the slope as more snow is entrained, usually forming a teardrop appearance. This is in contrast to a slab avalanche. Slab avalanches account for around 90% of avalanche-related fatalities, and occur when there is a strong, stiff layer of snow known as a slab. These are usually formed when snow is deposited by the wind on a lee slope. When the slab fails, the fracture, in a weak layer, very rapidly propagates so that a large area, that can be hundreds of metres in extent and several metres thick, starts moving almost instantaneously. The third starting type is a slush avalanche which occurs when the snowpack becomes saturated by water. These tend to also start and spread out from a point.
As avalanches move down the slope they may entrain snow from the snowpack and grow in size. The snow may also mix with the air and form a powder cloud. An avalanche with a powder cloud is known as a powder snow avalanche. The powder cloud is a turbulent suspension of snow particles that flows as a gravity current. Powder snow avalanches are the largest avalanches and can exceed 300 km/h and 10,000,000 tonnes of snow, they can flow for long distance along flat valley bottoms and even up hill for short distances.

Causes
Snow avalanches occur when the load on the upper snow layers exceeds the bonding forces of a mass of snow (bonding to layer beneath, horizontal internal stability, support from anchors such as rocks and trees, stress support from top or bottom of slope). A low timber line will exacerbate the threat because trees help hold snow in place and slow it down once it begins moving.

Contributing factors
All avalanches are caused by an over-burden of material, typically snowpack, that is too massive and unstable for the slope that supports it. Determining the critical load, the amount of over-burden which is likely to cause an avalanche, is a complex task involving the evaluation of a number of factors. These factors include:
Terrain
Slopes flatter than 25 degrees or steeper than 60 degrees typically have a low risk of avalanche. Snow does not accumulate significantly on steep slopes; also, snow does not flow easily on flat slopes. Human triggered avalanches have the greatest incidence when the snow's angle of repose is between 35 and 45 degrees; the critical angle, the angle at which the human incidence of avalanches is greatest, is 38 degrees. The rule of thumb is: A slope that is flat enough to hold snow but steep enough to ski has the potential to generate an avalanche, regardless of the angle. However, avalanche risk increases with use; that is, the more a slope is disturbed by skiers, the more likely it is that an avalanche will occur.
The four variables that influence snowpack evolution and composition are temperature, precipitation, solar radiation, and wind. In the mid-latitudes of the Northern Hemisphere, more avalanches occur on shady slopes with northern and north-eastern exposures. However, when the human triggered incidence of avalanches are normalized to mid-latitude rates of recreational use, no significant difference in hazard for a given exposure direction can be found. The snowpack on slopes with southern exposures are strongly influenced by sunshine; daily cycles of surface thawing and refreezing create a crust that may tend to stabilize an otherwise unstable snowpack, but the crust, once it has been fractured, may detach itself from the underlying layers of snow, slide, and promote the generation of an avalanche. Slopes in the lee of a ridge or other wind obstacle accumulate more snow and are more likely to include pockets of abnormally deep snow, windslabs, and cornices, all of which, when disturbed, may trigger an avalanche.
Convex slopes are more dangerous than concave slopes. The primary factor contributing to the increased avalanche danger on convex slopes is a disparity between the tensile strength of snow layers and their compressive strength.
Another factor affecting the incidence of avalanches is the nature of the ground surface underneath the snow cover. Full-depth avalanches (avalanches that sweep a slope virtually clean of snow cover) are more common on slopes with smooth ground cover, such as grass or rock slabs. Vegetation plays an important role in anchoring a snowpack; however, in certain instances, boulders or vegetation may actually create weak areas deep within the snowpack.
Snow structure and characteristics
The structure of the snowpack is a strong predictor of avalanche danger. For an avalanche to occur, it is necessary that a snowpack have a weak layer (or instability) below the surface and an overlying slab of snow. Unfortunately, the relationship between easily-observed properties of snow layers (strength, grain size, grain type, temperature, etc.) and avalanche danger are extraordinarily complex; consequently, this is an area that is not yet fully understood. Furthermore, snow cover and stability often vary widely within relatively small areas, and a risk assessment of a given slope is unlikely to remain valid, accurate, or useful for very long.
Various snow composition and deposition characteristics also influence the likelihood of an avalanche. Newly-fallen snow requires time to bond with the snow layers beneath it, especially if the new snow is light and powdery. Snow that lies above boulders or certain types of plants has little to help anchor it to the slope. Larger snow crystals, generally speaking, are less likely to bond together to form strong structures than smaller crystals are. Consolidated snow is less likely to slough than light powdery layers; however, well-consolidated snow is more likely to generate unstable slabs.
Weather
Weather also influences the evolution of snowpack formation. The most important factors are heating by the sun, radiational cooling, vertical temperature gradients in standing snow, snowfall amounts, and snow types.
If the temperature is high enough for gentle freeze-thaw cycles to take place, the melting and refreezing of water in the snow strengthens the snowpack during the freezing phase and weakens it during the thawing phase. A rapid rise in temperature, to a point significantly above the freezing point, may cause a slope to avalanche, especially in spring. Persistent cold temperatures prevent the snow from stabilizing; long cold spells may contribute to the formation of depth hoar, a condition where there is a pronounced temperature gradient, from top to bottom, within the snow. When the temperature gradient becomes sufficiently strong, thin layers of "faceted grains" may form above or below embedded crusts, allowing slippage to occur.
Any wind stronger than a light breeze can contribute to a rapid accumulation of snow on sheltered slopes downwind. Wind pressure at a favorable angle can stabilize other slopes. A "wind slab" is a particularly fragile and brittle structure which is heavily-loaded and poorly-bonded to its underlayment. Even on a clear day, wind can quickly shift the snow load on a slope. This can occur in two ways: by top-loading and by cross-loading. Top-loading occurs when wind deposits snow perpendicular to the fall-line on a slope; cross-loading occurs when wind deposits snow parallel to the fall-line. When a wind blows over the top of a mountain, the leeward, or downwind, side of the mountain experiences top-loading, from the top to the bottom of that lee slope. When the wind blows across a ridge that leads up the mountain, the leeward side of the ridge is subject to cross-loading. Cross-loaded wind-slabs are usually difficult to identify visually.
Snowstorms and rainstorms are important contributors to avalanche danger. Heavy snowfall may cause instability in the existing snowpack, both because of the additional weight and because the new snow has insufficient time to bond to underlying snow layers. Rain has a similar effect. In the short-term, rain causes instability because, like a heavy snowfall, it imposes an additional load on the snowpack; and, once rainwater seeps down through the snow, it acts as a lubricant, reducing the natural friction between snow layers that holds the snowpack together. Most avalanches happen during or soon after a storm.
Daytime exposure to sunlight can rapidly destabilize the upper layers of a snowpack. Sunlight reduces the sintering, or necking, between snow grains. During clear nights, the snowpack can strengthen, or tighten, through the process of long-wave radiative cooling. When the night air is significantly cooler than the snowpack, the heat stored in the snow is re-radiated into the atmosphere.

Avalanche avoidance
Due to the complexity of the subject, winter travelling in the backcountry (off-piste) is never 100% safe. Good avalanche safety is a continuous process, including route selection and examination of the snowpack, weather conditions, and human factors. Several well-known good habits can also minimize the risk. If local authorities issue avalanche risk reports, they should be considered and all warnings heeded. Never follow in the tracks of others without your own evaluations; snow conditions are almost certain to have changed since they were made. Observe the terrain and note obvious avalanche paths where vegetation is missing or damaged, where there are few surface anchors, and below cornices or ice formations. Avoid traveling below others who might trigger an avalanche.

Prevention
There are several ways to prevent avalanches and lessen their power and destruction. They are employed in areas where avalanches pose a significant threat to people, such as ski resorts and mountain towns, roads and railways. Explosives are used extensively to prevent avalanches, especially at ski resorts where other methods are often impractical. Explosive charges are used to trigger small avalanches before enough snow can build up to cause a large avalanche. Snow fences and light walls can be used to direct the placement of snow. Snow builds up around the fence, especially the side that faces the prevailing winds. Downwind of the fence, snow buildup is lessened. This is caused by the loss of snow at the fence that would have been deposited and the pickup of the snow that is already there by the wind, which was depleted of snow at the fence. When there is a sufficient density of trees, they can greatly reduce the strength of avalanches. They hold snow in place and when there is an avalanche, the impact of the snow against the trees slows it down. Trees can either be planted or they can be conserved, such as in the building of a ski resort, to reduce the strength of avalanches.
Artificial barriers can be very effective in reducing avalanche damage. There are several types. One kind of barrier (snow net) uses a net strung between poles that are anchored by guy wires in addition to their foundations. These barriers are similar to those used for rockslides. Another type of barrier is a rigid fence like structure (snow fence) and may be constructed of steel, wood or pre-stressed concrete. They usually have gaps between the beams and are built perpendicular to the slope, with reinforcing beams on the downhill side. Rigid barriers are often considered unsightly, especially when many rows must be built. They are also expensive and vulnerable to damage from falling rocks in the warmer months. Finally, there are barriers that stop or deflect avalanches with their weight and strength. These barriers are made out of concrete, rocks or earth. They are usually placed right above the structure, road or railway that they are trying to protect, although they can also be used to channel avalanches into other barriers. Occasionally, earth mounds are placed in the avalanche's path to slow it down.

Safety in avalanche terrain
Terrain management - Terrain management involves reducing the exposure of an individual to the risks of traveling in avalanche terrain by carefully selecting what areas of slopes to travel on. Features to be cognizant of include not under cutting slopes (removing the physical support of the snow pack), not traveling over convex rolls (areas where the snow pack is under tension), staying away from weaknesses like exposed rock, and avoiding areas of slopes that expose one to terrain traps (gulleys that can be filled in, cliffs over which one can be swept, or heavy timber into which one can be carried).
Group management - Group management is the practice of reducing the risk of having a member of a group, or a whole group involved in an avalanche. Minimize the number of people on the slope, and maintain separation. Ideally one person should pass over the slope into an area protected from the avalanche hazard before the next one leaves protective cover. Route selection should also consider what dangers lie above and below the route, and the consequences of an unexpected avalanche (i.e., unlikely to occur, but deadly if it does). Stop or camp only in safe locations. Wear warm gear to delay hypothermia if buried. Plan escape routes. Most important of all practice good communication with in a group including clearly communicating the decisions about safe locations, escape routes, and slope choices, and having a clear understanding of every members skills in snow travel, avalanche rescue, and route finding.
Group size - Group size must balance the hazard of not having enough people to effectively carry out a rescue with the risk of having too many members of the group to safely manage the risks. It is generally recommended not to travel alone. There will be no-one to witness your burial and start the rescue.
Leadership - Leadership in avalanche terrain requires well defined decision making protocols, which are being taught in a growing number of courses provided by national avalanche resource centers in Europe and North America. Fundamental to leadership in avalanche terrain is an honest attempt at assessing ones blind spots (what information am I ignoring?) There is a growing body of research into the psychological behaviors and group dynamics that lead to avalanche involvement.

Human survival and avalanche rescue
Even small avalanches are a serious danger to life, even with properly trained and equipped companions who avoid the avalanche. Between 55 and 65 percent of victims buried in the open are killed, and only 80 percent of the victims remaining on the surface survive. (McClung, p.177).
Research carried out in Italy based on 422 buried skiers indicates how the chances of survival drop:
very rapidly from 92 percent within 15 minutes to only 30 percent after 35 minutes (victims die of suffocation)
near zero after two hours (victims die of injuries or hypothermia)
(Historically, the chances of survival were estimated at 85% percent within 15 minutes, 50% within 30 minutes, 20% within one hour).
Consequently it is vital that everyone surviving an avalanche is used in an immediate search and rescue operation, rather than waiting for help to arrive. Additional help can be called once it can be determined if anyone is seriously injured or still remains unaccountable after the immediate search (i.e., after at least 30 minutes of searching). Even in a well equipped country such as France, it typically takes 45 minutes for a helicopter rescue team to arrive, by which time most of the victims are likely to have died.
In some cases avalanche victims are not located until spring thaw melts the snow, or even years later when objects emerge from a glacier.

Search and rescue equipment
Chances of a buried victim being found alive and rescued are increased when everyone in a group is carrying and using standard avalanche equipment, and have trained in how to use it. However, like a seat belt in a vehicle, using the right equipment does not justify exposing yourself to unnecessary risks with the hope that the equipment might save your life when it is needed.
Avalanche cords
Using an avalanche cord is the oldest form of equipment - mainly used before beacons became available. The principle is simple. An approximately 10 meter long red cord (similar to parachute cord) is attached to the person in question's belt. While skiing, snowboarding, or walking the cord is dragged along behind the person. If the person gets buried in an avalanche, the light cord stays on top of the snow. Due to the color the cord is easily visible for rescue personnel. Typically the cord has iron markings every one meter that indicate the direction and length to the victim.
Beacons
Beacons - known as "beepers", peeps (pieps), ARVAs (Appareil de Recherche de Victimes en Avalanche, in French), LVS (Lawinen-Versch?tteten-Suchger?t, Swiss German), avalanche transceivers, or various other trade names, are important for every member of the party. They emit a "beep" via 457 kHz radio signal in normal use, but may be switched to receive mode to locate a buried victim up to 80 meters away. Analog receivers provide audible beeps that rescuers interpret to estimate distance to a victim. To be effective, beacons require regular practice. Some older models of beepers operated on a different frequency (2.275 kHz ) and a group leader should ensure these are no longer in use.
Recent digital models also attempt to give visual indications of direction and distance to victims and require less practice to be useful. There are also passive transponder devices that can be inserted into equipment, but they require specialized search equipment that might only be found near an organized sports area.
Probes
Portable (collapsible) probes can be extended to probe into the snow to locate the exact location of a victim at several yards / metres in depth. When multiple victims are buried, probes should be used to decide the order of rescue, with the shallowest being dug out first since they have the greatest chance of survival.
Probing can be a very time-consuming process if a thorough search is undertaken for a victim without a beacon. In the U.S., 86% of the 140 victims found (since 1950) by probing were already dead. Survival/rescue more than 2 m deep is relatively rare (about 4%). Probes should be used immediately after a visual search for surface clues, in coordination with the beacon search.
Shovels
When an avalanche stops, the deceleration normally compresses the snow to a hard mass. Shovels are essential for digging through the snow to the victim, as the deposit is often too dense to dig with hands or skis. A large scoop and sturdy handle are important. Shovels are also useful for digging snow pits as part of evaluating the snow pack for hidden hazards, such as weak layers supporting large loads.
Other devices
More back-country adventurers are also carrying Emergency Position-Indicating Radio Beacon (EPIRB) containing the Global Positioning System (GPS). This device can quickly notify search and rescue of an emergency and the general location (within 100 yards), but only if the person with the EPIRB has survived the avalanche and can activate the device. Alternatively, survivors may use a mobile phone to notify emergency personnel of their location obtained from a GPS without EPIRB capability.
Technology to summon outside help is to be used with the knowledge that those responding will likely be performing a body recovery. Only on-site rescuers are in position to render assistance during the brief interval that the victim is most likely to survive.
Other rescue devices are proposed, developed and used, such as avalanche balls, vests and airbags, based on statistics that most deaths are due to suffocation.
Although inefficient, some rescue equipment can be improvised by unprepared parties: ski poles can become short probes, skis or snowboards can be used as shovels. A first aid kit and equipment is useful for assisting survivors who may have cuts, broken bones, or other injuries, in addition to hypothermia.

Witnesses as rescuers
Survival time is short, if a victim is buried. There is no time to waste before starting a search, and many people have died because the surviving witnesses failed to do even the simplest search.
Witnesses to an avalanche that engulfs people are frequently limited to those in the party involved in the avalanche. Those not caught should try to note the locations where the avalanched person or people were seen. This is such an important priority it should be discussed before initially entering an avalanche area. Once the avalanche has stopped, and there is no danger of secondary slides, these points should be marked with objects for reference. Survivors should then be counted to see who may be lost. If the area is safe to enter, a visual search of the likely burial areas should begin (along a downslope trajectory from the marked points last seen). Some victims are buried partially or shallowly and can be located quickly by making a visual scan of the avalanche debris and pulling out any clothing or equipment found. It may be attached to someone buried.
Alert others if a radio is available, especially if help is nearby, but do NOT waste valuable resources by sending a searcher for help at this point. Switch transceivers to receive mode and check them. Select likely burial areas and search them, listening for beeps (or voices), expanding to other areas of the avalanche, always looking and listening for other clues (movement, equipment, body parts). Probe randomly in probable burial areas. Mark any points where signal was received or equipment found. Only after the first 15 minutes of searching should consideration be given to sending someone for help. Continue scanning and probing near marked clues and other likely burial areas. After 30-60 minutes, consider sending a searcher to get more help, as it is more likely than not that any remaining victims have not survived.
Line probes are arranged in most likely burial areas and marked as searched. Continue searching and probing the area until it is no longer feasible or reasonable to continue. Avoid contaminating the scent of the avalanche area with urine, food, spit, blood, etc, in case search dogs arrive.
The areas where buried victims are most likely to be found are: below the marked point last seen, along the line of flow of the avalanche, around trees and rocks or other obstacles, near the bottom runout of the debris, along edges of the avalanche track, and in low spots where the snow may collect (gullies, crevasses, creeks, ditches along roads, etc). Although less likely, other areas should not be ignored if initial searches are not fruitful.
Once a buried victim is found and his or her head is freed, perform first aid (airway, breathing, circulation/pulse, arterial bleeding, spinal injuries, fractures, shock, hypothermia, internal injuries, etc), according to local law and custom.

Victims
Victims caught in an avalanche are advised to try to ski or board toward the side of the avalanche until they fall, then to jettison their equipment and attempt swimming motions. As the snow comes to rest an attempt should be made to preserve an air-space in front of the mouth, and try to thrust an arm, leg or object above the surface, assuming you are still conscious. If it is possible to move once the snow stops, enlarge the air space, but minimize movement to maximize the oxygen supply. Warm breath may soon cause a mask of ice to glaze over the snow in your face, sealing it against further air.

Myths About Avalanches
Myth: Avalanches can be triggered by shouting - Avalanches cannot be triggered by sound as the forces exerted by the pressures in sound waves are far too low. The very large shockwaves produced by explosions can trigger avalanches, however, if they are close enough to the surface.
Myth: There is an air blast in front of an avalanche - Avalanches travel much slower than the speed of sound and therefore there are no shock waves. The pressure in front of an avalanche is exactly the same as in front of any object moving at a similar speed and increases smoothly as the avalanche approaches.

Notable avalanches
A large avalanche in Montroc, France, in 1999, 300,000 cubic metres of snow slid on a 30 degree slope, achieving a speed of 100 km/h (60 mph). It killed 12 people in their chalets under 100,000 tons of snow, 5 meters (15 feet) deep. The mayor of Chamonix was convicted of second-degree murder for not evacuating the area, but received a suspended sentence.
On May 31, 1970 the Ancash earthquake caused a large avalanche from Huascaran, resulting in the destruction of the town of Yungay, Peru and the death of at least 18,000 people.
During World War I, approximately 50,000 soldiers died as a result of avalanches during the mountain campaign in the Alps at the Austrian-Italian front, many of which were caused by artillery fire. However, it is very doubtful avalanches were used deliberately at the strategic level as weapons; more likely they were simply a side effect to shelling enemy troops, occasionally adding to the toll taken by the artillery. Avalanche prediction is nearly impossible; forecasters can only assert the conditions, terrain and relative likelihood of slides with the help of detailed weather reports and from localized snowpack observation. It would be almost impossible to predict avalanche conditions many miles behind enemy lines, making it impossible to intentionally target a slope at risk for avalanches. Also, high priority targets received continual shelling and would be unable to build up enough unstable snow to form devastating avalanches, effectively imitating the avalanche prevention programs at ski resorts.

European avalanche risk table
In Europe, the avalanche risk is widely rated on the following scale, which was adopted in April 1993 to replace the earlier non-standard national schemes. Descriptions were last updated in May 2003 to enhance uniformity.
In France, most avalanche deaths occur at risk levels 3 and 4. In Switzerland most occur at levels 2 and 3. It is thought that this may be due to national differences of interpretation when assessing the risks.
Stability:
Generally described in more detail in the avalanche bulletin (regarding the altitude, aspect, type of terrain etc.)
additional load:
heavy: two or more skiers or boarders without spacing between them, a single hiker or climber, a grooming machine, avalanche blasting.
light: a single skier or snowboarder smoothly linking turns and without falling, a group of skiers or snowboarders with a minimum 10 m gap between each person, a single person on snowshoes.
Gradient:
gentle slopes: with an incline below about 30 degree.
steep slopes: with an incline over 30 degree.
very steep slopes: with an incline over 35 degree.
extremely steep slopes: extreme in terms of the incline (over 40 degree), the terrain profile, proximity of the ridge, smoothness of underlying ground.

European avalanche size table
Avalanche size:

North American Avalanche Danger Scale
In the United States and Canada, the following avalanche danger scale is used.

Volcanoes

A volcano is an opening, or rupture, in a planet's surface or crust, which allows hot, molten rock, ash and gases to escape from below the surface. Volcanic activity involving the extrusion of rock tends to form mountains or features like mountains over a period of time.
Volcanoes are generally found where tectonic plates are pulled apart or come together. A mid-oceanic ridge, for example the Mid-Atlantic Ridge, has examples of volcanoes caused by "divergent tectonic plates" pulling apart; the Pacific Ring of Fire has examples of volcanoes caused by "convergent tectonic plates" coming together. By contrast, volcanoes are usually not created where two tectonic plates slide past one another. Volcanoes can also form where there is stretching and thinning of the Earth's crust (called "non-hotspot intraplate volcanism"), such as in the African Rift Valley, the Wells Gray-Clearwater Volcanic Field and the Rio Grande Rift in North America and the European Rhine Graben with its Eifel volcanoes.
Volcanoes can be caused by "mantle plumes". These so-called "hotspots" , for example at Hawaii, can occur far from plate boundaries. Hotspot volcanoes are also found elsewhere in the solar system, especially on rocky planets and moons.

Plate tectonics and hotspots

Divergent plate boundaries
At the mid-oceanic ridges, two tectonic plates diverge from one another. New oceanic crust is being formed by hot molten rock slowly cooling and solidifying. The crust is very thin at mid-oceanic ridges due to the pull of the tectonic plates. The release of pressure due to the thinning of the crust leads to adiabatic expansion, and the partial melting of the mantle. This melt causes the volcanism and makes the new oceanic crust. Most divergent plate boundaries are at the bottom of the oceans, therefore most volcanic activity is submarine, forming new seafloor. Black smokers or deep sea vents are an example of this kind of volcanic activity. Where the mid-oceanic ridge is above sea-level, volcanic islands are formed, for example, Iceland.

Convergent plate boundaries
Subduction zones are places where two plates, usually an oceanic plate and a continental plate, collide. In this case, the oceanic plate subducts, or submerges under the continental plate forming a deep ocean trench just offshore. The crust is then melted by the heat from the mantle and becomes magma. This is due to the water content lowering the melting temperature. The magma created here tends to be very viscous due to its high silica content, so often does not reach the surface and cools at depth. When it does reach the surface, a volcano is formed. Typical examples for this kind of volcano are Mount Etna and the volcanoes in the Pacific Ring of Fire.

Hotspots
Hotspots are not usually located on the ridges of tectonic plates, but above mantle plumes, where the convection of Earth's mantle creates a column of hot material that rises until it reaches the crust, which tends to be thinner than in other areas of the Earth. The temperature of the plume causes the crust to melt and form pipes, which can vent magma. Because the tectonic plates move whereas the mantle plume remains in the same place, each volcano becomes dormant after a while and a new volcano is then formed as the plate shifts over the hotspot. The Hawaiian Islands are thought to be formed in such a manner, as well as the Snake River Plain, with the Yellowstone Caldera being the part of the North American plate currently above the hotspot.

Volcanic features
The most common perception of a volcano is of a conical mountain, spewing lava and poisonous gases from a crater at its summit. This describes just one of many types of volcano, and the features of volcanoes are much more complicated. The structure and behavior of volcanoes depends on a number of factors. Some volcanoes have rugged peaks formed by lava domes rather than a summit crater, whereas others present landscape features such as massive plateaus. Vents that issue volcanic material (lava, which is what magma is called once it has escaped to the surface, and ash) and gases (mainly steam and magmatic gases) can be located anywhere on the landform. Many of these vents give rise to smaller cones such as on a flank of Hawaii's K?lauea.
Other types of volcano include cryovolcanoes (or ice volcanoes), particularly on some moons of Jupiter, Saturn and Neptune; and mud volcanoes, which are formations often not associated with known magmatic activity. Active mud volcanoes tend to involve temperatures much lower than those of igneous volcanoes, except when a mud volcano is actually a vent of an igneous volcano.

Shield volcanoes
Hawaii and Iceland are examples of places where volcanoes extrude huge quantities of Lava in that gradually build a wide mountain with a shield-like profile.

Cinder cones
Volcanic cones or cinder cones result from eruptions that erupt mostly small pieces of scoria and pyroclastics (both resemble cinders, hence the name of this volcano type) that build up around the vent. These can be relatively short-lived eruptions that produce a cone-shaped hill perhaps 30 to 400 meters high. Most cinder cones erupt only once. Cinder cones may form as flank vents on larger volcanoes, or occur on their own. Par?cutin in Mexico and Sunset Crater in Arizona are examples of cinder cones.

Stratovolcanoes (composite volcano)
Stratovolcanoes are tall conical mountains composed of lava flows and other ejecta in alternate layers, the strata that give rise to the name. Stratovolcanoes are also known as composite volcanoes. Strato/composite volcanoes are made of cinders, ash and lava. The volcanoes are made by another volcano. Cinders and ash pile on top of each other, then lava flows on top and dries and then the process begins again. Classic examples include Mt. Fuji in Japan, Mount Mayon in the Philippines, and Mount Vesuvius and Stromboli in Italy.

Supervolcanoes
Supervolcano is the popular term for a large volcano that usually has a large caldera and can potentially produce devastation on an enormous, sometimes continental, scale. Such eruptions would be able to cause severe cooling of global temperatures for many years afterwards because of the huge volumes of sulfur and ash erupted. They are the most dangerous type of volcano. Examples include Yellowstone Caldera in Yellowstone National Park of western USA, Lake Taupo in New Zealand and Lake Toba in Sumatra, Indonesia. Supervolcanoes are hard to identify centuries later, given the enormous areas they cover. Large igneous provinces are also considered supervolcanoes because of the vast amount of basalt lava erupted.

Submarine volcanoes
Submarine volcanoes are common features on the ocean floor. Some are active and, in shallow water, disclose their presence by blasting steam and rocky debris high above the surface of the sea. Many others lie at such great depths that the tremendous weight of the water above them prevents the explosive release of steam and gases, although they can be detected by hydrophones and discoloration of water because of volcanic gases. Pumice rafts may also appear. Even large submarine eruptions may not disturb the ocean surface. Because of the rapid cooling effect of water as compared to air, and increased buoyancy, submarine volcanoes often form rather steep pillars over their volcanic vents as compared to above-surface volcanoes. They may become so large that they break the ocean surface as new islands. Pillow lava is a common eruptive product of submarine volcanoes.

Subglacial volcanoes
Subglacial volcanoes develop underneath icecaps. They are made up of flat lava flows atop extensive pillow lavas and palagonite. When the icecap melts, the lavas on the top collapse leaving a flat-topped mountain. Then, the pillow lavas also collapse, giving an angle of 37.5 degrees. These volcanoes are also called table mountains, tuyas or (uncommonly) mobergs. Very good examples of this type of volcano can be seen in Iceland, however, there are also tuyas in British Columbia. The origin of the term comes from Tuya Butte, which is one of the several tuyas in the area of the Tuya River and Tuya Range in northern British Columbia. Tuya Butte was the first such landform analyzed and so its name has entered the geological literature for this kind of volcanic formation. The Tuya Mountains Provincial Park was recently established to protect this unusual landscape, which lies north of Tuya Lake and south of the Jennings River near the boundary with the Yukon Territory.
Antarctica eruption
In January, 2008, the British Antarctic Survey (Bas) scientists led by Hugh Corr and David Vaughan, reported (in the journal Nature Geoscience) that 2,200 years ago, a volcano erupted under Antarctica ice sheet (based on airborne survey with radar images). The biggest eruption in the last 10,000 years, the volcanic ash was found deposited on the ice surface under the Hudson Mountains, close to Pine Island Glacier.

Erupted material

Lava composition
Another way of classifying volcanoes is by the composition of material erupted (lava), since this affects the shape of the volcano. Lava can be broadly classified into 4 different compositions (Cas & Wright, 1987):
If the erupted magma contains a high percentage (>63%) of silica, the lava is called felsic.
Felsic lavas (or rhyolites) tend to be highly viscous (not very fluid) and are erupted as domes or short, stubby flows. Viscous lavas tend to form stratovolcanoes or lava domes. Lassen Peak in California is an example of a volcano formed from felsic lava and is actually a large lava dome.
Because siliceous magmas are so viscous, they tend to trap volatiles (gases) that are present, which cause the magma to erupt catastrophically, eventually forming stratovolcanoes. Pyroclastic flows (ignimbrites) are highly hazardous products of such volcanoes, since they are composed of molten volcanic ash too heavy to go up into the atmosphere, so they hug the volcano's slopes and travel far from their vents during large eruptions. Temperatures as high as 1,200 degreeC are known to occur in pyroclastic flows, which will incinerate everything flammable in their path and thick layers of hot pyroclastic flow deposits can be laid down, often up to many meters thick. Alaska's Valley of Ten Thousand Smokes, formed by the eruption of Novarupta near Katmai in 1912, is an example of a thick pyroclastic flow or ignimbrite deposit. Volcanic ash that is light enough to be erupted high into the Earth's atmosphere may travel many kilometres before it falls back to ground as a tuff.
If the erupted magma contains 52-63% silica, the lava is of intermediate composition.
These "andesitic" volcanoes generally only occur above subduction zones (e.g. Mount Merapi in Indonesia).
If the erupted magma contains <52% and >45% silica, the lava is called mafic (because it contains higher percentages of magnesium (Mg) and iron (Fe)) or basaltic. These lavas are usually much less viscous than rhyolitic lavas, depending on their eruption temperature; they also tend to be hotter than felsic lavas. Mafic lavas occur in a wide range of settings:
At mid-ocean ridges, where two oceanic plates are pulling apart, basaltic lava erupts as pillows to fill the gap;
Shield volcanoes (e.g. the Hawaiian Islands, including Mauna Loa and Kilauea), on both oceanic and continental crust;
As continental flood basalts.
Some erupted magmas contain <=45% silica and produce ultramafic lava. Ultramafic flows, also known as komatiites, are very rare; indeed, very few have been erupted at the Earth's surface since the Proterozoic, when the planet's heat flow was higher. They are (or were) the hottest lavas, and probably more fluid than common mafic lavas.

Lava texture
Two types of lava are named according to the surface texture: ?A?a (pronounced [?a?a]) and p?hoehoe (pronounced IPA: pa?hoehoe), both words having Hawaiian origins. ?A?a is characterized by a rough, clinkery surface and is what most viscous and hot lava flows look like. However, even basaltic or mafic flows can be erupted as ?a?a flows, particularly if the eruption rate is high and the slope is steep. P?hoehoe is characterized by its smooth and often ropey or wrinkly surface and is generally formed from more fluid lava flows. Usually, only mafic flows will erupt as p?hoehoe, since they often erupt at higher temperatures or have the proper chemical make-up to allow them to flow at a higher fluidity.

Volcanic activity
A popular way of classifying magmatic volcanoes is by their frequency of eruption, with those that erupt regularly called active, those that have erupted in historical times but are now quiet called dormant, and those that have not erupted in historical times called extinct. However, these popular classifications-extinct in particular-are practically meaningless to scientists. They use classifications which refer to a particular volcano's formative and eruptive processes and resulting shapes, which was explained above.
There is no real consensus among volcanologists on how to define an "active" volcano. The lifespan of a volcano can vary from months to several million years, making such a distinction sometimes meaningless when compared to the lifespans of humans or even civilizations. For example, many of Earth's volcanoes have erupted dozens of times in the past few thousand years but are not currently showing signs of eruption. Given the long lifespan of such volcanoes, they are very active. By human lifespans, however, they are not.
Scientists usually consider a volcano to be active if it is currently erupting or showing signs of unrest, such as unusual earthquake activity or significant new gas emissions. Many scientists also consider a volcano active if it has erupted in historic time. It is important to note that the span of recorded history differs from region to region; in the Mediterranean, recorded history reaches back more than 3,000 years but in the Pacific Northwest of the United States, it reaches back less than 300 years, and in Hawaii, little more than 200 years. The Smithsonian Global Volcanism Program's definition of 'active' is having erupted within the last 10,000 years.
Dormant volcanoes are those that are not currently active (as defined above), but could become restless or erupt again. Confusion however, can arise because many volcanoes which scientists consider to be active are referred to as dormant by laypersons or in the media.
Extinct volcanoes are those that scientists consider unlikely to erupt again. Whether a volcano is truly extinct is often difficult to determine. Since "supervolcano" calderas can have eruptive lifespans sometimes measured in millions of years, a caldera that has not produced an eruption in tens of thousands of years is likely to be considered dormant instead of extinct. For example, the Yellowstone Caldera in Yellowstone National Park is at least 2 million years old and hasn't erupted violently for approximately 640,000 years, although there has been some minor activity relatively recently, with hydrothermal eruptions less than 10,000 years ago and lava flows about 70,000 years ago. For this reason, scientists do not consider the Yellowstone Caldera extinct. In fact, because the caldera has frequent earthquakes, a very active geothermal system (i.e. the entirety of the geothermal activity found in Yellowstone National Park), and rapid rates of ground uplift, many scientists consider it to be an active volcano.

Notable volcanoes
The 16 current Decade Volcanoes are:

Effects of volcanoes
There are many different kinds of volcanic activity and eruptions: phreatic eruptions (steam-generated eruptions), explosive eruption of high-silica lava (e.g., rhyolite), effusive eruption of low-silica lava (e.g., basalt), pyroclastic flows, lahars (debris flow) and carbon dioxide emission. All of these activities can pose a hazard to humans. Earthquakes, hot springs, fumaroles, mud pots and geysers often accompany volcanic activity.
The concentrations of different volcanic gases can vary considerably from one volcano to the next. Water vapor is typically the most abundant volcanic gas, followed by carbon dioxide and sulfur dioxide. Other principal volcanic gases include hydrogen sulfide, hydrogen chloride, and hydrogen fluoride. A large number of minor and trace gases are also found in volcanic emissions, for example hydrogen, carbon monoxide, halocarbons, organic compounds, and volatile metal chlorides.
Large, explosive volcanic eruptions inject water vapor (H2O), carbon dioxide (CO2), sulfur dioxide (SO2), hydrogen chloride (HCl), hydrogen fluoride (HF) and ash (pulverized rock and pumice) into the stratosphere to heights of 16-32 kilometres (10-20 mi) above the Earth's surface. The most significant impacts from these injections come from the conversion of sulfur dioxide to sulfuric acid (H2SO4), which condenses rapidly in the stratosphere to form fine sulfate aerosols. The aerosols increase the Earth's albedo-its reflection of radiation from the Sun back into space - and thus cool the Earth's lower atmosphere or troposphere; however, they also absorb heat radiated up from the Earth, thereby warming the stratosphere. Several eruptions during the past century have caused a decline in the average temperature at the Earth's surface of up to half a degree (Fahrenheit scale) for periods of one to three years. The sulfate aerosols also promote complex chemical reactions on their surfaces that alter chlorine and nitrogen chemical species in the stratosphere. This effect, together with increased stratospheric chlorine levels from chlorofluorocarbon pollution, generates chlorine monoxide (ClO), which destroys ozone (O3). As the aerosols grow and coagulate, they settle down into the upper troposphere where they serve as nuclei for cirrus clouds and further modify the Earth's radiation balance. Most of the hydrogen chloride (HCl) and hydrogen fluoride (HF) are dissolved in water droplets in the eruption cloud and quickly fall to the ground as acid rain. The injected ash also falls rapidly from the stratosphere; most of it is removed within several days to a few weeks. Finally, explosive volcanic eruptions release the greenhouse gas carbon dioxide and thus provide a deep source of carbon for biogeochemical cycles.
Gas emissions from volcanoes are a natural contributor to acid rain. Volcanic activity releases about 130 to 230 teragrams (145 million to 255 million short tons) of carbon dioxide each year. Volcanic eruptions may inject aerosols into the Earth's atmosphere. Large injections may cause visual effects such as unusually colorful sunsets and affect global climate mainly by cooling it. Volcanic eruptions also provide the benefit of adding nutrients to soil through the weathering process of volcanic rocks. These fertile soils assist the growth of plants and various crops. Volcanic eruptions can also create new islands, as the magma cools and solidifies upon contact with the water.

Volcanoes on other planetary bodies
The Earth's Moon has no large volcanoes and no current volcanic activity, although recent evidence suggests it may still possess a partially molten core. However, the Moon does have many volcanic features such as maria (the darker patches seen on the moon), rilles and domes.
The planet Venus has a surface that is 90% basalt, indicating that volcanism played a major role in shaping its surface. The planet may have had a major global resurfacing event about 500 million years ago, from what scientists can tell from the density of impact craters on the surface. Lava flows are widespread and forms of volcanism not present on Earth occur as well. Changes in the planet's atmosphere and observations of lightning, have been attributed to ongoing volcanic eruptions, although there is no confirmation of whether or not Venus is still volcanically active. However, radar sounding by the Magellan probe revealed evidence for comparatively recent volcanic activity at Venus's highest volcano Maat Mons, in the form of ash flows near the summit and on the northern flank.
There are several extinct volcanoes on Mars, four of which are vast shield volcanoes far bigger than any on Earth. They include Arsia Mons, Ascraeus Mons, Hecates Tholus, Olympus Mons, and Pavonis Mons. These volcanoes have been extinct for many millions of years, but the European Mars Express spacecraft has found evidence that volcanic activity may have occurred on Mars in the recent past as well.
Jupiter's moon Io is the most volcanically active object in the solar system because of tidal interaction with Jupiter. It is covered with volcanoes that erupt sulfur, sulfur dioxide and silicate rock, and as a result, Io is constantly being resurfaced. Its lavas are the hottest known anywhere in the solar system, with temperatures exceeding 1,800 K (1,500 degreeC). In February 2001, the largest recorded volcanic eruptions in the solar system occurred on Io. Europa, the smallest of Jupiter's Galilean moons, also appears to have an active volcanic system, except that its volcanic activity is entirely in the form of water, which freezes into ice on the frigid surface. This process is known as cryovolcanism, and is apparently most common on the moons of the outer planets of the solar system.
In 1989 the Voyager 2 spacecraft observed cryovolcanoes (ice volcanoes) on Triton, a moon of Neptune, and in 2005 the Cassini-Huygens probe photographed fountains of frozen particles erupting from Enceladus, a moon of Saturn. The ejecta may be composed of water, liquid nitrogen, dust, or methane compounds. Cassini-Huygens also found evidence of a methane-spewing cryovolcano on the Saturnian moon Titan, which is believed to be a significant source of the methane found in its atmosphere. It is theorized that cryovolcanism may also be present on the Kuiper Belt Object Quaoar.

Etymology
Volcano is thought to derive from Vulcano, a volcanic island in the Aeolian Islands of Italy whose name in turn originates from Vulcan, the name of a god of fire in Roman mythology. The study of volcanoes is called volcanology, sometimes spelled vulcanology.
The Roman name for the island Vulcano has contributed the word for volcano in most modern European languages.

In culture

Past beliefs
Many ancient accounts ascribe volcanic eruptions to supernatural causes, such as the actions of gods or demigods. To the ancient Greeks, volcanoes' capricious power could only be explained as acts of the gods, while 16th/17th-century German astronomer Johannes Kepler believed they were ducts for the Earth's tears. One early idea counter to this was proposed by Jesuit Athanasius Kircher (1602-1680), who witnessed eruptions of Mount Etna and Stromboli, then visited the crater of Vesuvius and published his view of an Earth with a central fire connected to numerous others caused by the burning of sulfur, bitumen and coal.
Various explanations were proposed for volcano behavior before the modern understanding of the Earth's mantle structure as a semisolid material was developed. For decades after awareness that compression and radioactive materials may be heat sources, their contributions were specifically discounted. Volcanic action was often attributed to chemical reactions and a thin layer of molten rock near the surface.

Heraldry
Volcanoes appear as a charge in heraldry.

Panoramas

Other natural disasters

A natural disaster is the consequence of a natural hazard (e.g. volcanic eruption, earthquake,and landslide) which moves from potential in to an active phase, and as a result affects human activities. Human vulnerability, exacerbated by the lack of planning or lack of appropriate emergency management, leads to financial, structural, and human losses. The resulting loss depends on the capacity of the population to support or resist the disaster, their resilience. This understanding is concentrated in the formulation: "disasters occur when hazards meet vulnerability". A natural hazard will hence never result in a natural disaster in areas without vulnerability, e.g. strong earthquakes in uninhabited areas. The term natural has consequently been disputed because the events simply are not hazards or disasters without human involvement. The degree of potential loss can also depend on the nature of the hazard itself, ranging from a single lightning strike, which threatens a very small area, to impact events, which have the potential to end civilization. For lists of natural disasters, see the list of disasters or the list of deadliest natural disasters.

Natural hazards
A natural hazard is a situation which has the potential to create an event that has an effect on people. They result from natural processes in the environment and some natural hazards are related - earthquakes can result in tsunamis, drought can lead directly to famine and disease, and so on.

Geological
Avalanche
An avalanche is a geophysical hazard involving 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. Notable avalanches include:
The 1910 Wellington avalanche
The 1954 Blons avalanches
The 1970 Ancash earthquake
The 1999 Galt?r Avalanche
The 2002 Kolka-Karmadon rock ice slide
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. 90% of all earthquakes - and 81% of the largest - occur around the 40,000km long Pacific Ring of Fire, which roughly bounds the Pacific Plate. Many earthquakes happen each day, few of which are large enough to cause significant damage. Some of the most significant earthquakes in recent times include:
The 2004 Indian Ocean earthquake, the second largest earthquake in recorded history, registering a moment magnitude of 9.3. The huge tsunamis triggered by this earthquake cost the lives of at least 229,000 people.
The 7.6-7.7 2005 Kashmir earthquake, which cost 79,000 lives in Pakistan.
The 7.7 magnitude July 2006 Java earthquake, which also triggered tsunamis.
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. The Tangiwai disaster is an excellent example, as is the one which killed an estimated 23,000 people in Armero, Colombia, during the 1985 eruption of Nevado del Ruiz.
Landslides and Mudflows
A landslide is a disaster closely related to an avalanche, but instead of occurring with snow, it occurs involving actual elements of the ground, including rocks, trees, parts of houses, and anything else which may happen to be swept up. Landslides can be caused by earthquakes, volcanic eruptions, or general instability in the surrounding land. Mudslides, or mud flows, are a special case of landslides, in which heavy rainfall causes loose soil on steep terrain to collapse and slide downwards (see also Lahar); these occur with some regularity in parts of California after periods of heavy rain.
Sinkholes
A 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, or extremely infrequent supervolcano eruptions (where the volcano expels at least 1,000 cubic kilometers of material) in places like Lake Taupo, 26,500 years ago, or Yellowstone Caldera, which has the potenetial to become a supervolcano in the near geological future. Some eruptions form pyroclastic flows, which are high-temperature clouds of ash and steam that can trial down mountainsides at speed exceeding an airliner. 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.

Hydrological
Flood
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.
The Huang Ho (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 US history.
The 1998 Yangtze River Floods, also 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.
Tropical cyclones can result in extensive flooding, as happened with:
Bhola Cyclone, striking East Pakistan (now Bangladesh) in 1970,
Typhoon Nina, striking China in 1975,
Tropical Storm Allison, which struck Houston, Texas in 2001 and
Hurricane Katrina, which left most of New Orleans under water in the year 2005.
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.
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.
Maelstrom
A large tidal whirlpool. 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 20-40km/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, allowing natural phenomena to form a standing wave.
Tsunami
A tsunami is a wave of water caused by the displacement of a body of water. The word comes from Japanese words meaning harbor and wave. Tsunami can be caused by undersea earthquakes as in the 2004 Indian Ocean Earthquake, or by landslides such as the one which occurred at Lituya Bay, Alaska. Meteotsunamis are caused by meteorological phenomena. A megatsunami is an informal term used to describe very large tsunamis. They are a highly local effect, either occurring on shores extremely close to the origin of a tsunami, or in deep, narrow inlets. 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 524m (1742 ft.) vertical run-up on July 10, 1958,in Lituya Bay,Alaska.

Climatic
Blizzard
A severe winter storm condition characterized by low temperatures, strong winds, and heavy blowing snow. Significant blizzards in the United States include:
The Great Blizzard of 1888
The Schoolhouse Blizzard earlier the same year
The Armistice Day Blizzard in 1940
The Storm of the Century in 1993
Drought
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. 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, Western Australia, New South Wales, Victoria and Queensland (all states of Australia) have been under drought conditions for five to ten years. The drought is beginning to affect urban populations for the first time. Also 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.
Scientists warn that global warming may result in more extensive drought in coming years.
Hailstorm
A hailstorm is a natural disaster 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. A particularly damaging hailstorm hit Munich, Germany on August 31, 1986, felling thousands of trees and causing millions of dollars in insurance claims.
Heat wave
A heat wave is a disaster 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. The worst heat wave in recent history was the European Heat Wave of 2003. There is also the potential for longer term events causing global warming, including stadial events (the opposite to glacial 'ice age' events), or through human induced climatic warming.
Hurricanes, Tropical cyclones, and Typhoons
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. Hurricane is used for these phenomena in the Atlantic and eastern Pacific Oceans, tropical cyclone in the Indian, typhoon in the western Pacific. 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.
Ice age (Glacial Event)
An ice age is a geologic period, but could also be viewed in the light of a catastrophic natural disaster, since in an ice age, the climate all over the world would change and places which were once considered habitable would then be too cold to permanently inhabit. A side effect of an ice age could possibly be a famine, caused by a worldwide drought.
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 and 300 mph, and possibly higher. Tornadoes can occur one at a time, or can occur in large tornado outbreaks along squall lines or in other large areas of thunderstorm development. Waterspouts are tornadoes occurring over tropical waters in light rain conditions.

Fire
Wildfire
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.

Health and disease
Epidemic
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 epidemic, beginning in 1959
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 1.5 million people each year
Ebola hemorrhagic fever, which has claimed hundreds of victims in Africa in several outbreaks
Famine
A social and economic crisis that is commonly accompanied by widespread malnutrition, starvation, epidemic disease and increased mortality. Although some famines occur - or are aggravated - by natural factors, it can and often is a result of economic or military policy that deprives people of the food that they require to survive.
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
Impact event
An impact event is a natural disaster in which an extraterrestrial piece of rock or other material collides with the Earth. The exact consequences of a direct Earth impact would vary greatly with size of the colliding object, although in cases of medium to large impacts short-term climate change and a general failure of agriculture. An example would be the Tunguska event.
Solar flare
A solar flare is a phenomenon where the sun suddenly releases a great amount of solar radiation, much more than normal. It is theorized that these releases of radiation could cause a widespread failure of communications technology across the globe. The exact implications of such a failure are unknown. Further studies are being carried out. Some known solar flares include:
An X20 event on August 16, 1989
A similar flare on April 2, 2001
The most powerful flare ever recorded, on November 4, 2003, estimated at between X40 and X45
The most powerful flare in the past 500 years is believed to have occurred in September 1859

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 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".

Disasters

• Floods
• Earthquakes
• Wind storms
• Forest / scrub fires
• Non-natural disasters
• Droughts
• Extreme temperatures
• Avalanches / landslides
• Volcanoes
• Other natural disasters

Disasters2

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