A natural hazard^[1] is a threat of a naturally Nature, in the broadest sense, is equivalent to the natural world, physical world, or material world. "Nature" refers to the phenomena of the physical world, and also to life in general. It ranges in scale from the subatomic to the cosmic occurring event that will have a negative effect on people or the environment. Many natural hazards are interrelated, e.g. earthquakes An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time. Earthquakes are measured with a seismometer; a device which also records is known as a seismograph. The can cause tsunamis A tsunami (Japanese: 津波 [tsɯnami], lit. 'harbor wave'; English pronunciation: /suːˈnɑːmi/ (t)soo-NAH-mee) or tidal wave is a series of water waves (called a tsunami wave train) caused by the displacement of a large volume of a body of water, usually an ocean, but can occur in large lakes. Tsunamis are a frequent occurrence in Japan; and drought 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, can lead directly to famine A famine is a widespread scarcity of food that may apply to any faunal species. This phenomenon is usually accompanied by regional malnutrition, starvation, epidemic, and increased mortality. A concrete example of the division between a natural hazard and a natural disaster is that the 1906 San Francisco earthquake The San Francisco earthquake of 1906 was a major earthquake that struck San Francisco, California, and the coast of Northern California at 5:12 a.m. on Wednesday, April 18, 1906. The most widely accepted estimate for the magnitude of the earthquake is a moment magnitude of 7.9; however, other values have been proposed, from 7.7 to as high as 8.25 was a disaster, whereas earthquakes are a hazard. A natural hazard becomes a natural disaster A natural disaster is the effect of a natural hazard that affects the environment, and leads to financial, environmental and/or human losses. The resulting loss depends on the capacity of the population to support or resist the disaster, and their resilience. This understanding is concentrated in the formulation: "disasters occur when hazards when it affects people, officially causing more than 10 deaths, injuring more than 100 people, and/or causing US$16,000,000 of damage.^{[citation needed]}

Geological hazards

Avalanche

An avalanche An avalanche is a rapid flow of snow down a slope, from either natural triggers or human activity. Typically occurring in mountainous terrain, an avalanche can mix air and water with the descending snow. Powerful avalanches have the capability to entrain ice, rocks, trees, and other material on the slope. Avalanches are primarily composed of is a geophysical hazard a slide of a large snow (or rock) mass down a mountainside, caused when a buildup of snow is released down a slope, it is one of the major dangers faced in the mountains in winter. An avalanche is an example of a gravity current consisting of granular material. In an avalanche, lots of material or mixtures of different types of material fall or slide rapidly under the force of gravity. Avalanches are often classified by what they are made of.

Earthquake

An earthquake An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time. Earthquakes are measured with a seismometer; a device which also records is known as a seismograph. The is a phenomenon A phenomenon , plural phenomena or phenomenons, is any observable occurrence. In popular usage, a phenomenon often refers to an extraordinary event. In scientific usage, a phenomenon is any event that is observable, however commonplace it might be, even if it requires the use of instrumentation to observe it. For example, in physics, a phenomenon that results from a sudden release of stored energy that radiates seismic waves Seismic waves are waves of force that travel through the Earth or other elastic bodies, for example as a result of an earthquake, explosion, or some other process that imparts forces. Seismic waves are studied by seismologists, and measured by a seismograph, which records the output of a seismometer, or geophone. For seismic studies of oil. At the Earth Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets. It is sometimes referred to as the World, the Blue Planet,[note 6] or by its Latin name, Terra.[note 7]'s surface, earthquakes may manifest themselves by a shaking or displacement of the ground and sometimes tsunamis A tsunami (Japanese: 津波 [tsɯnami], lit. 'harbor wave'; English pronunciation: /suːˈnɑːmi/ (t)soo-NAH-mee) or tidal wave is a series of water waves (called a tsunami wave train) caused by the displacement of a large volume of a body of water, usually an ocean, but can occur in large lakes. Tsunamis are a frequent occurrence in Japan;. 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 The north-eastern side is a divergent boundary with the Explorer Plate, the Juan de Fuca Plate and the Gorda Plate forming respectively the Explorer Ridge, the Juan de Fuca Ridge and the Gorda Ridge. In the middle of the eastern side is a transform boundary with the North American Plate along the San Andreas Fault, and a boundary with the Cocos. Many earthquakes happen each day, few of which are large enough to cause significant damage.

Lahar

A lahar A lahar is a type of mudflow or landslide composed of pyroclastic material and water that flows down from a volcano, typically along a river valley. The term "lahar" originated in the Javanese language of Indonesia is a type of natural disaster closely related to a volcanic eruption During a volcanic eruption, lava, tephra , and various gases are expelled from a volcanic vent or fissure, and involves a large amount of material, including mud, rock In geology, rock is a naturally occurring solid aggregate of minerals and/or mineraloids, and ash Volcanic ash consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions, less than 2 millimetres in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact with water causing phreatomagmatic sliding down the side of the volcano A volcano is an opening, or rupture, in a planet's surface or crust, which allows hot magma, ash and gases to escape from below the surface at a rapid pace. These flows can destroy entire towns in seconds and kill thousands of people.

Landslides and mudflows

A landslide A landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rock falls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments. Although the action of gravity is the primary driving force for a landslide to occur, there are other contributing is a disaster closely related to an avalanche An avalanche is a rapid flow of snow down a slope, from either natural triggers or human activity. Typically occurring in mountainous terrain, an avalanche can mix air and water with the descending snow. Powerful avalanches have the capability to entrain ice, rocks, trees, and other material on the slope. Avalanches are primarily composed of, but instead of occurring with snow Snow is a type of precipitation within the Earth's atmosphere in the form of crystalline water ice, consisting of a multitude of snowflakes that fall from clouds. Since snow is composed of small ice particles, it is a granular material. It has an open and therefore soft structure, unless packed by external pressure. Snowflakes come in a variety of, it occurs involving actual elements of the ground, including rocks , trees A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to 6 m; some authors set a minimum of 10 cm trunk diameter, parts of houses, and anything else which may happen to be swept up. Landslides can be caused by earthquakes An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time. Earthquakes are measured with a seismometer; a device which also records is known as a seismograph. The, volcanic eruptions During a volcanic eruption, lava, tephra , and various gases are expelled from a volcanic vent or fissure, or general instability in the surrounding land. Mudslides A mudslide is the most rapid and fluid type of downhill mass wasting. It is a rapid movement of a large mass of mud formed from loose soil and water. Similar terms are mudflow, mud stream, debris flow (e.g. in high mountains), jökulhlaup, and lahar (from volcanoes, see also pyroclastic flow), or mudflows, are a special case of landslides, in which heavy rainfall causes loose soil on steep terrain to collapse and slide downwards (see also lahar A lahar is a type of mudflow or landslide composed of pyroclastic material and water that flows down from a volcano, typically along a river valley. The term "lahar" originated in the Javanese language of Indonesia).

Sinkholes

A sinkhole A sinkhole, also known as a sink, shake hole, swallow hole, swallet, doline or cenote, is a natural depression or hole in the Earth's surface caused by karst processes - the chemical dissolution of carbonate rocks or suffosion processes f.e. in sandstone. Sinkholes may vary in size from less than 1 to 600 meters both in diameter and depth, and is localized depression in the surface topography, usually caused by the collapse of a subterranean structure, such as a cave A cave or cavern is a natural underground space large enough for a human to enter. Some people[who?] suggest that the term cave should only apply to cavities that have some part that does not receive daylight; however, in popular usage, the term includes smaller spaces like sea caves, rock shelters, and grottos. 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 During a volcanic eruption, lava, tephra , and various gases are expelled from a volcanic vent or fissure is the point in which a volcano A volcano is an opening, or rupture, in a planet's surface or crust, which allows hot magma, ash and gases to escape from below the surface 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 Kīlauea is an active volcano in the Hawaiian Islands, one of five shield volcanoes that together form the island of Hawaiʻi. It is the most recent of a series of volcanoes that have created the Hawaiian archipelago, as the Pacific Plate moves over the Hawaii hotspot. Kīlauea means "spewing" or "much spreading" in the in Hawaii The state encompasses nearly the entire volcanic Hawaiian Island chain, which comprises hundreds of islands spread over 1,500 miles . At the southeastern end of the archipelago, the eight "main islands" are (from the northwest to southeast) Niʻihau, Kauaʻi, Oʻahu, Molokaʻi, Lānaʻi, Kahoʻolawe, Maui, and Hawaiʻi. The last is by, or extremely infrequent super volcano A supervolcano is a volcano capable of producing a volcanic eruption with ejecta greater than 1,000 cubic kilometers . This is thousands of times larger than most historic volcanic eruptions. Supervolcanoes can occur when magma in the Earth rises into the crust from a hotspot but is unable to break through the crust. Pressure builds in a large and eruptions (where the volcano expels at least 1,000 cubic kilometers of material) in places like Lake Taupo Lake Taupo is a lake situated in the North Island of New Zealand. With a surface area of 616 square kilometres , it is the largest lake by surface area in New Zealand, and the largest freshwater lake by surface area in Oceania, 26,500 years ago, or Yellowstone Caldera The Yellowstone Caldera is the volcanic caldera located in Yellowstone National Park in the United States, sometimes referred to as the Yellowstone Supervolcano. The caldera is located in the northwest corner of Wyoming, in which the vast majority of the park is contained. The major features of the caldera measure about 34 miles by 45 miles (72 km), which has the potential to become a super volcano in the near geological future. Some eruptions form pyroclastic flows A pyroclastic flow is a common and devastating result of certain explosive volcanic eruptions. The flows are fast-moving currents of hot gas and rock (collectively known as tephra), which travel away from the volcano at speeds generally as great as 700 km/h (450 mph). The gas can reach temperatures of about 1,000 °C (1,830 °F). The 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 The Toba supereruption occurred between 69,000 and 77,000 years ago at Lake Toba (Sumatra, Indonesia), and it is recognized as one of Earth's largest known eruptions. The related catastrophe theory holds that this supervolcanic event plunged the planet into a 6 to 10 year volcanic winter, which resulted in the world's human population being, 70 to 75 thousand years ago, a super volcanic A supervolcano is a volcano capable of producing a volcanic eruption with ejecta greater than 1,000 cubic kilometers . This is thousands of times larger than most historic volcanic eruptions. Supervolcanoes can occur when magma in the Earth rises into the crust from a hotspot but is unable to break through the crust. Pressure builds in a large and event at Lake Toba Lake Toba is a lake and supervolcano, 100 kilometres long and 30 kilometres wide, and 505 metres (1,666 ft) at its deepest point. Located in the middle of the northern part of the Indonesian island of Sumatra with a surface elevation of about 900 metres (2,953 ft), the lake stretches from 2°53′N 98°31′E / 2.88°N 98.52°E to 2°21′N 9 reduced the human population to 10,000 or even 1,000 breeding pairs, creating a bottleneck in human evolution Human evolution, or anthropogenesis, is the origin and evolution of Homo sapiens as a distinct species from other hominids, great apes and placental mammals. The study of human evolution encompasses many scientific disciplines, including physical anthropology, primatology, archaeology, linguistics and genetics.

Hydrological hazards

Flood

Floods A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Flooding may result from the volume of water within a body of water, are the result of prolonged rainfall from a storm 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,, including thunderstorms A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically-assigned cloud type associated with the thunderstorm is the cumulonimbus. Thunderstorms are, rapid melting of large amounts of snow Snow is a type of precipitation within the Earth's atmosphere in the form of crystalline water ice, consisting of a multitude of snowflakes that fall from clouds. Since snow is composed of small ice particles, it is a granular material. It has an open and therefore soft structure, unless packed by external pressure. Snowflakes come in a variety of, or rivers A river is a natural watercourse, usually freshwater, flowing toward an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including stream, creek, brook, rivulet, and rill; there is no which swell from excess precipitation upstream and cause widespread damage to areas downstream, or less frequently the bursting of man-made dams or levees A levee, levée, dike , embankment, floodbank or stopbank is a natural or artificial slope or wall to regulate water levels. It is usually earthen and often parallel to the course of a river or the coast. Tropical cyclones can result in extensive flooding and storm surge.

Limnic eruption

Also referred to as a 'lake overturn', a limnic eruption is a rare type of natural disaster in which CO₂ suddenly erupts from deep lake water, posing the threat of suffocating wildlife, livestock and humans. Such an eruption may also cause tsunamis in the lake as the rising CO₂ displaces water. Scientists believe landslides, volcanic activity, or explosions can trigger such an eruption.

Whirlpool

A whirlpool is a swirling body of water usually produced by ocean tides. The vast majority of whirlpools are not very powerful. More powerful ones are more properly termed maelstroms. Vortex is the proper term for any whirlpool that has a downdraft. (Technically, these approximate to a 'free vortex', in which the tangential velocity (v) increases as the centre line is approached, so that the angular momentum (rv) is constant). Very small whirlpools can easily be seen when a bath or a sink is draining, but these are produced in a very different manner from those in nature. Smaller whirlpools also appear at the base of many waterfalls. In the case of powerful waterfalls, like Niagara Falls, these whirlpools can be quite strong. The most powerful whirlpools are created in narrow shallow straits with fast flowing water.

Maelstrom

Maelstroms are 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 20–40 km/h.

Seiche

A seiche is a standing wave in an enclosed or partially enclosed body of water. Seiches and seiche-related phenomena have been observed on lakes, reservoirs, bays and seas. The key requirement for formation of a seiche is that the body of water be at least partially bounded.

Tsunami

A tsunami is a wave of water caused by the displacement of a body of water. The word comes from Japanese words "tsu" meaning harbor and "nami" meaning wave (tsu+nami=harbor wave). 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. 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 9, 1958,in Lituya Bay,Alaska.

Climatic and atmospheric hazards

Blizzard

A blizzard is a severe winter storm icy and windy conditions characterized by low temperatures, strong winds, and heavy snow.

Drought

Drought is defined as an acute shortage of water and crop failure that results when the average rainfall is very less than the normal. A drought is an abnormally dry period when there is not enough water to support agricultural, urban or environmental water needs. Extended droughts can result in deaths by starvation or disease, and can result in wildfires. Scientists warn that global warming may result in more extensive droughts in coming years.

Hailstorm

A hailstorm is a natural hazard where a thunderstorm produces numerous hailstones which damage the location in which they fall. Hailstorms can be especially devastating to farm fields, ruining crops and damaging equipment.

Heat wave

A heat wave is a hazard characterized by heat which is considered extreme and unusual in the area in which it occurs. Heat waves are rare and require specific combinations of weather events to take place, and may include temperature inversions, katabatic winds, or other phenomena. There is potential for longer term events causing global warming, including stadial events (the opposite to glacial 'ice age' events), or through human induced climatic warming.

Cyclonic storms

Hurricane, tropical cyclone, and typhoon are different names for the same phenomenon: a cyclonic storm system that forms over the oceans. It is caused by evaporated water that comes off of the ocean and becomes a storm. The Coriolis Effect causes the storms to spin, and a hurricane is declared when this spinning mass of storms attains a wind speed greater than 74 mph (119 km/h). Hurricane is used for these phenomena in the Atlantic and eastern Pacific Oceans, tropical cyclone in the Indian, typhoon in the western Pacific.

Ice storm

An ice storm is a particular weather event in which precipitation falls as ice, due to atmosphere conditions.

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