Recent natural disasters

Earthquakes
2004: Indian Ocean earthquake. The second largest earthquake in recorded history, registering a magnitude of 9.3.
2005: Kashmir earthquake. Magnitude 7.6-7.7, which cost 79,000 lives in Pakistan.
2008: Sichuan, China earthquake. Magnitude 7.9, death toll at over 61,150.

Hurricanes
2005: Hurricane Katrina. Devastated the Gulf Coast, USA.

Drought
2006: Sichuan, China. Its worst drought with nearly 8 million suffering water shortage.

Wildfire
2009: Australia bushfires

Epidemics
2002: SARS
2009: Swine Flu

Famine
2005: Malawi
2008: North Korea
2008: Afghanistan
2008: Bangladesh
2009: Kenya

Gamma Ray bursts
2003: Closest one to Earth
2008: Most luminous
2008: Most energetic
2009: Most distant object in the Universe


Solar Flare
2003: Most powerful ever recorded


Supernovae
2006: Largest ever supernova


The charity Oxfam stated that the number of people hit by natural disasters is expected to rise by about 50%, to reach 375 million a year by 2015.

Space disasters

Gamma ray bursts

Gamma-ray bursts are flashes associated with extremely energetic explosions in distant galaxies. They are the most luminous events in the universe since the Big Bang. Bursts can last from milliseconds to nearly an hour, although a typical burst lasts a few seconds.

The sources of most GRBs are billions of light years away from Earth, implying that the explosions are both extremely energetic (a typical burst releases as much energy in a few seconds as the Sun will in its entire 10 billion year lifetime) and extremely rare (a few per galaxy per million years. It has been thought that a gamma-ray burst in our galaxy could cause a mass extinction on Earth.

Gamma-ray bursts are very bright as observed from Earth despite typical immense distances. An average long GRB is comparable to a bright Galactic star despite a distance of billions of light years (compared to a few tens of light years for most stars). Because their energy is strongly beamed, the gamma rays emitted by most bursts are expected to miss the Earth and never be detected. When a gamma-ray burst is pointed towards Earth, the focusing of its energy along a relatively narrow beam causes the burst to appear much brighter than it would have been were its energy emitted spherically.

Impact events

An impact event is the collision of a large meteorite, asteroid, comet, or other object with the Earth or another planet. Small objects frequently impact Earth.

Asteroids with a 1 km diameter impact the Earth every 500,000 years on average. Large collisions with five kilometer objects happen approximately once every ten million years. The last known impact of an object of 10 km or more in diameter was the dinosoar extiction event 65 million years ago.

The Earth has gone through periods of abrupt change, some due to the impact of large asteroids and comets on the planet. A few of these impacts may have caused massive climate change and the extinction of large numbers of plant and animal species. The Moon is widely attributed to be the result of a huge impact early in Earth's history.

Impact events even earlier in the history of Earth have been credited with creative as well as destructive events; it has been proposed that the water in the Earth's oceans was delivered by impacting comets, and some have suggested that the origins of life may have been influenced by impacting objects bringing organic chemicals or lifeforms to the Earth's surface.

Solar flare

A solar flare is a phenomenon where the sun suddenly releases a great amount of solar radiation, much more than normal. The frequency of occurrence of solar flares varies, from several per day when the Sun is particularly "active" to less than one each week when the Sun is "quiet". Large flares are less frequent than smaller ones. Solar activity varies with an 11-year cycle. At the peak of the cycle there are typically more sunspots on the Sun, and hence more solar flares.

Solar flares strongly influence the local (space weather) of Earth. They produce streams of highly energetic particles in the solar wind that can present radiation hazards to spacecraft and astronauts. Current methods of flare prediction are problematic, and there is no certain indication that an active region on the Sun will produce a flare. However, many properties of sunspots and active regions correlate with flaring.

Supernova

A supernova (pl. supernovae) is a star explosion. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months. During this short interval, a supernova can radiate as much energy as the Sun could emit over its life span. On average, supernovae occur about once every 50 years in a galaxy the size of the Milky Way.

Several kinds of supernovae exist and form. After the core of an aging massive star ceases to generate energy, it may undergo sudden collapse into a neutron star or black hole. Alternatively, a white dwarf star may collect enough material from another star to raise its core temperature enough to ignite carbon fusion, at which point it undergoes nuclear fusion, completely disrupting itself.

A near-Earth supernova is an explosion resulting from the death of a star that occurs close enough to the Earth (roughly fewer than 100 light-years away) to have noticeable effects. Gamma rays from a supernova induce a chemical reaction in the upper atmosphere, converting nitrogen into nitrogen oxides, depleting the ozone layer enough to expose the surface to harmful solar and cosmic radiation.

Health and disease disasters

Epidemics

An epidemic is an outbreak of a contractible disease that spreads at a rapid rate through a human population. Defining an epidemic can be difficult, depending on what is "expected". An epidemic may be restricted to one locale (an outbreak), more general (an "epidemic") or even global (pandemic). Because it is based on what is thought normal, a few cases of a very rare disease may be classified as an "epidemic," while many cases of a common disease (such as the common cold) would not.

Factors that have been described by to stimulate the rise of new epidemics include:

• Changes in agricultural practices and land use
  
• Changes in society
  
• Poor population health
  
• Hospitals and medical procedures
  
• Contamination of water supplies and food sources
  
• International travel
  
• Failure of public health programs
  
• International trade

Famine

A famine is a widespread shortage of food. The failure of a harvest or the change in conditions, such as drought, can create a situation whereby large numbers of people live where the carrying capacity of the land has temporarily dropped radically. Famine is often associated with subsistence agriculture, that is, where most farming is aimed at producing enough food energy to survive.

Disasters, whether natural or man-made, have been associated with conditions of famine ever since humankind has been keeping written records. War, in particular, was associated with famine, particularly in those times and places where warfare included attacks on land, by burning or salting fields, or on those who tilled the soil. In recent decades, famine has always a problem of food distribution and/or poverty, as there has been sufficient food to feed the whole population of the world. Lack of market economy has been blamed for both poverty and problems of food distribution.

Supporting farmers in areas of food insecurity, through such measures as free fertilizers and seeds, increases food harvest and reduces food prices. For example, in Malawi, almost five million of its 13 million people needed emergency food aid. Then, however, deep fertilizer subsidies and lesser ones for seed, abetted by good rains, helped farmers produce record-breaking corn harvests in 2006 and 2007, according to government crop estimates.

Fire disasters

Wildfire

Fires start when an ignition source is brought into contact with a combustible material (e.g. peat, shrub, trees) that is subjected to sufficient heat and has an adequate supply of oxygen from the ambient air. A wildfire is any uncontrolled fire that occurs in the wilderness, wildland, or bush. Other names such as wildland fire, forest fire, brush fire, vegetation fire, grass fire, peat fire, bushfire, and hill fire are commonly used. Fires in forested areas can move at speeds of 10.8 kilometres per hour (7 mph), while grass fires have been recorded at up to 22 kilometres per hour (14 mph).

Nine out of ten wildfires are reportedly caused by some human interaction, like arson; others are caused by natural events such as lightning strikes, volcanic discharges, etc. Wildfires differ from other fires only by their extensive size; the speed at which it spreads out from its original source; its ability to change direction unexpectedly; and to jump gaps, such as roads, rivers and fire breaks.

Weather patterns such as heat waves, droughts, and climate changes can also dramatically increase the risk and alter the behavior of wildfires. Years of precipitation followed by warm periods have encouraged more widespread fires and longer fire seasons.

Fire intensity also increases during daytime hours. Burn rates of smoldering logs are up to five times greater during the day due to lower humidity, increased temperatures, and increased wind speeds. Sunlight warms the ground during the day and causes air currents to travel uphill, and downhill during the night as the land cools.

Weather disasters

Blizzards

A blizzard is a severe winter storm condition characterized by low temperatures, strong winds, and heavy blowing snow. Blizzards are formed when a high pressure system, also known as a ridge, interacts with a low pressure system.

According to Environment Canada, a winter storm must have winds of 40 km/h or more, have snow or blowing snow, visibility less than 500 ft, a wind chill of less than −25 °C, and that all of these conditions must last for 4 hours or more before the storm can be properly called a blizzard.

Like all severe weather events, blizzards can be disruptive to local economies. In cities that do not have snow removal equipment, traffic and commerce can be brought to a stand still for days, and in some cases weeks. The economic impact ranges across industries, from lost productivity in companies because people cannot get to work, parents must stay home with children due to school closings, airport closures, product delivery delays and the actual cost of snow removal.

Cyclones

Cyclone, tropical cyclone, hurricane, and typhoon are different names for the same phenomenon of a cyclonic storm system that forms over the oceans.

A cyclone refers to an area of closed, circular fluid motion rotating in the same direction as the Earth. This is usually characterized by inward spiraling winds that rotate counter clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.

Large-scale cyclonic circulations are almost always centred on areas of low atmospheric pressure. Warm-core cyclones such as tropical cyclones, lie within a smaller scale. Subtropical cyclones are of intermediate size. Cyclones have also been seen on other planets outside of the Earth, such as Mars and Neptune.

Droughts

A drought is an extended period of months or years when a region has a deficiency in its water supply. It can have a substantial impact on the 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.

Generally, rainfall is related to the amount of water vapor in the atmosphere, combined with the upward forcing of the air mass containing that water vapor. If either of these are reduced,the result is a drought. Periods of drought can have significant environmental, agricultural, health, economic and social consequences. The effect varies according to vulnerability. For example, farmers are more likely to migrate during drought because they do not have alternative food sources.

Some effects of drought are:

• Diminished crop growth or yield productions and carrying capacity for livestock
  
• Dust storms, when drought hits an area suffering from desertification and erosion
• Famine due to lack of water
  
• Habitat damage, affecting both terrestrial and aquatic wildlife
  
• Reduced electricity production due to insufficient available coolant for power stations and reduced water flow through hydroelectric dams
  
• Shortages of water for industrial users
  
• Snakes migration and increases in snakebites
  
• Social unrest
  
• War over natural resources, including water and food
  
• Wildfires, such as Australian bushfires, are more common during times of drought

As a drought persists, the conditions surrounding it gradually worsen and its impact on the local population gradually increases.

Tornados

A tornado is a violent, dangerous, rotating column of air which is in contact with the surface of the earth. Tornadoes come in many sizes but are typically in the form of a visible condensation funnel, whose narrow end touches the earth and is often encircled by a cloud of debris and dust.

A tornado is not necessarily visible; however, the intense low pressure caused by the high wind speeds and rapid rotation usually causes water vapor in the air to become visible as a funnel cloud or condensation funnel.

There are different types of tornado. Here is a list of types and brief descriptions:

• A multiple vortex tornado: is a type of tornado in which two or more columns of spinning air rotate around a common center.
  
• A satellite tornado: is a term for a weaker tornado which forms very near a large, strong tornado.
  
• A waterspout: is defined simply as a tornado over water.
  
• A landspout: is a tornado which the name stems from their characterization as essentially a "waterspout on land".
  
• A dust devil: resembles a tornado in that it is a vertical swirling column of air.
  
• A fire whirl: tornado-like circulations occasionally occur near large, intense wildfires
  
• A steam devil: is a term describing a rotating updraft that involves steam or smoke.
  

Most tornadoes take on the appearance of a narrow funnel, a few hundred yards (a few hundred meters) across, with a small cloud of debris near the ground. There is an extremely wide range of tornado sizes, even for typical tornadoes. Weak tornadoes, can be exceedingly narrow, sometimes only a few feet across. On the other end of the spectrum, wedge tornadoes can have a damage path a mile (1.6 km) wide or more. Tornadoes can have a wide range of colors, depending on the environment in which they form. Those which form in a dry environment can be nearly invisible, marked only by swirling debris at the base of the funnel. Condensation funnels which pick up little or no debris can be gray to white. While traveling over a body of water as a waterspout, they can turn very white or even blue. Tornadoes in the Great Plains can turn red because of the reddish tint of the soil, and tornadoes in mountainous areas can travel over snow-covered ground, turning brilliantly white.

Water disasters

Floods

A flood is an overflow or accumulation of an expanse of water that submerges land, a deluge. Flooding may result from water within a body of water, such as a river or lake, which overflows, with the result that some of the water escapes its boundaries. While the size of a lake or other body of water will vary with seasonal changes, it is not a significant flood unless water endangers land areas used by man like a village, city or other inhabited area.

There are many effects of floods; the main one being people and livestock die due to drowning. Other effects include contamination of water, unhygenic conditions, shortage of crops and economical conditions, due to lack of tourism, building costs, and food shortage leading to price increase.

In many countries across the world, rivers prone to floods are often carefully managed. Defences such as reservoirs are used to prevent rivers from bursting their banks. When these defences fail, emergency measures such as sandbags or portable inflatable tubes are used. Coastal flooding has been addressed in Europe and the Americas with coastal defences, such as sea walls and barrier islands.

There are many disruptive effects of flooding on human settlements and economic activities. However, flooding can bring benefits, such as making soil more fertile and providing nutrients in which it is deficient.

Limnic eruptions

A limnic eruption is where CO2 suddenly erupts from deep lake water, however these eruptions are very rare.

Scientists believe landslides, volcanic activity, or explosions can trigger these eruptions. Lakes in which such activity occurs may be known as limnically active lakes or exploding lakes. Some features of limnically active lakes include:

• CO2-saturated water
  
• A cool lake bottom


• An upper and lower thermal layer with differing CO2 saturations


• Close to areas with volcanic activity

To date, this has been knowingly observed only twice. The first was in Cameroon at Lake Monoun in 1984, causing the death of 37 people living nearby. A second, deadlier eruption happened at neighbouring Lake Nyos in 1986, this time releasing over 80 million cubic meters of CO2 and killing between 1,700 and 1,800 people.

Once an eruption occurs, a large CO2 cloud forms above the lake and expands to the neighbouring region. Because CO2 is denser than air, it has a tendency to sink to the ground while pushing breathable air up. As a result, life forms that need to breathe oxygen suffocate once the CO2 cloud reaches them, as there is no breathable air.

Tsunamis

A tsunami is a series of water waves that is caused when a large volume of a body of water, such as an ocean, is rapidly displaced.

Earthquakes, volcanic eruptions and other underwater explosions, landslides and other mass movements and disturbances above or below water all have the potential to generate a tsunami. Due to the immense volumes of water and energy involved, the effects of tsunamis can be devastating.

There is often no advance warning of an approaching tsunami. If the first part of a tsunami to reach land is a draw back rather than a crest of the wave, the water along the shoreline may recede dramatically, exposing areas that are normally always submerged. This can serve as an advance warning of the approaching tsunami. If people are in a coastal area where the sea suddenly draws back (many survivors report an accompanying sucking sound), their only real chance of survival is to run for high ground or seek the high floors of high rise buildings.

Tsunami are not rare, with at least 25 tsunami occurring in the last century. Of these, many were recorded in the Asia–Pacific region—particularly Japan. The 2004 Indian Ocean Tsunami caused approximately 350,000 deaths and many more injuries.

Land movement disasters

Avalanches




An avalanche is a rapid flow of snow down a slope, from either natural triggers or human activity. Typically occurring in mountainous terrain, powerful avalanches have the capability to entrain ice, rocks, trees, and other material on the slope; however avalanches are mainly composed of snow.

Avalanches are always caused by an external stress on the snow pack, they are not random events. Natural triggers of avalanches include heating, rock fall, ice fall, and other sudden impacts; however, even a snow pack held at a constant temperature, pressure, and humidity will evolve over time and develop stresses. Human triggers of avalanches include skiers, snowmobiles, and controlled explosive work.


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.


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.



Earthquakes


An Earthquake is a sudden shake of the Earth's crust.The vibrations may vary in magnitude. Earthquakes are mainly sudden releases of energy caused by but also by volcanic activity, landslides, mine blasts, and nuclear experiments. An earthquakes power is measured on the Richter scale, with 1 being a small tremor and 10 causing serious damage.


Below is a list of Richter scale levels, their damage levels and frequency.

• Less than 2: Not felt, about 8000 happen every day


• 2-2.9: Not felt, but recorded, about 1000 happen every day


• 3-3.9: Often felt, but rarely cause damage, about 49,000 happen per year


• 4-4.9: Noticble shaking, but damage unlikly, about 6,200 per year


• 5-5.9: Can cause major damage to poor construtions, about 800 per year


• 6-6.9: Can be destructive in populated areas, about 120 per year
  

• 7-7.9: Can cause serious damage over larger areas, about 18 per year

• 8-8.9: Can cause serious damage in areas of several hundred miles, about 1 per year
  
• 9-9.9: Devastating, about 1 per 20 years
  
• 10+: Never recording, extremely rare
  

There are three main types of fault that may cause an earthquake: normal, reverse (thrust) and strike-slip. Normal and reverse are examples of displacement, where plates in the earths crust dip. Strike-slip is where the two plates slip (hence the name) past each other.

Volcanic eruptions

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.

Volcanos that regularly erupt are classed as "Active". There is no real critera on how to define an "active" volcano. 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. A "Dormant" volcano is a volcano that has erupted in previous times, but have not erupted for a while. Extinct volcanos are volcanos that are deemed never to erupt again because they contain no more lava.

It is difficult to distinguish an extinct volcano from a dormant one. Volcanoes are often considered to be extinct if there are no written records of its activity. Nevertheless volcanoes may remain dormant for a long period of time, and it is not uncommon for a so-called "extinct" volcano to erupt again. Vesuvius was thought to be extinct before its famous eruption of AD 79, which destroyed the town of Pompeii.