A natural disaster is a major adverse event
resulting from natural processes of the Earth;
examples are floods, hurricanes, tornadoes,
volcanic eruptions, earthquakes, tsunamis,
and other geologic processes.
A natural disaster can cause loss of life
or damage property, and typically leaves some
economic damage in its wake, the severity
of which depends on the affected population's
resilience, or ability to recover and also
on the infrastructure available.An adverse
event will not rise to the level of a disaster
if it occurs in an area without vulnerable
population.
In a vulnerable area, however, such as Nepal
during the 2015 earthquake, an earthquake
can have disastrous consequences and leave
lasting damage, which can require years to
repair.
== Geological disasters ==
=== 
Avalanches and landslides ===
A landslide is described as an outward and
downward slope movement of an abundance of
slope-forming materials including rock, soil,
artificial, or even a combination of these
things.During World War I, an estimated 40,000
to 80,000 soldiers died as a result of avalanches
during the mountain campaign in the Alps at
the Austrian-Italian front.
Many of the avalanches were caused by artillery
fire.
=== Earthquakes ===
An earthquake is the result of a sudden release
of energy in the Earth's crust that creates
seismic waves.
At the Earth's surface, earthquakes manifest
themselves by vibration, shaking, and sometimes
displacement of the ground.
Earthquakes are caused by slippage within
geological faults.
The underground point of origin of the earthquake
is called the seismic focus.
The point directly above the focus on the
surface is called the epicenter.
Earthquakes by themselves rarely kill people
or wildlife.
It is usually the secondary events that they
trigger such as building collapse, fires,
tsunamis (seismic sea waves) and volcanoes.
Many of these could possibly be avoided by
better construction, safety systems, early
warning and planning.
=== Sinkholes ===
When natural erosion, human mining or underground
excavation makes the ground too weak to support
the structures built on it, the ground can
collapse and produce a sinkhole.
For example, the 2010 Guatemala City sinkhole
which killed fifteen people was caused when
heavy rain from Tropical Storm Agatha, diverted
by leaking pipes into a pumice bedrock, led
to the sudden collapse of the ground beneath
a factory building.
=== Volcanic eruptions ===
Volcanoes can cause widespread destruction
and consequent disaster in several ways.
The effects include the volcanic eruption
itself that may cause harm following the explosion
of the volcano or falling rocks.
Secondly, lava may be produced during the
eruption of a volcano, and so as it leaves
the volcano the lava destroys many buildings,
plants and animals due to its extreme heat.
Thirdly, volcanic ash, generally meaning the
cooled ash, may form a cloud, and settle thickly
in nearby locations.
When mixed with water this forms a concrete-like
material.
In sufficient quantities, ash may cause roofs
to collapse under its weight but even small
quantities will harm humans if inhaled.
Since the ash has the consistency of ground
glass it causes abrasion damage to moving
parts such as engines.
The main killer of humans in the immediate
surroundings of a volcanic eruption is the
pyroclastic flows, which consist of a cloud
of hot volcanic ash which builds up in the
air above the volcano and rushes down the
slopes when the eruption no longer supports
the lifting of the gases.
It is believed that Pompeii was destroyed
by a pyroclastic flow.
A lahar is a volcanic mudflow or landslide.
The 1953 Tangiwai disaster was caused by a
lahar, as was the 1985 Armero tragedy in which
the town of Armero was buried and an estimated
23,000 people were killed.
Volcanoes rated at 8 (the highest level) on
the Volcanic Explosivity Index are known as
supervolcanoes.
According to the Toba catastrophe theory,
75,000 to 80,000 years ago a supervolcanic
eruption at what is now Lake Toba in Sumatra
reduced the human population to 10,000 or
even 1,000 breeding pairs, creating a bottleneck
in human evolution, and killed three-quarters
of all plant life in the northern hemisphere.
However, there is considerable debate regarding
the veracity of this theory.
The main danger from a supervolcano is the
immense cloud of ash, which has a disastrous
global effect on climate and temperature for
many years.
== Hydrological disasters ==
A violent, sudden and destructive change either
in the quality of Earth's water or in the
distribution or movement of water on land
below the surface or in the atmosphere.
=== Floods ===
A flood is an overflow of water that 'submerges'
land.
The EU Floods Directive defines a flood as
a temporary covering the land with water which
is usually not covered by water.
In the sense of 'flowing water', the word
may also be applied to the inflow of the tides.
Flooding may result from the volume of water
within a body of water, such as a river or
lake, which overflows, causing some of the
water to escape its usual boundaries.
While the size of a lake or other body of
water will vary with seasonal changes in precipitation
and snow melt, it is not a significant flood
unless the water covers land used by man,
like a village, city or other inhabited area,
roads, expanses of farmland, etc.
=== Tsunami ===
A 
tsunami (plural: tsunamis or tsunami; from
Japanese: 津波, lit.
"harbour wave"; English pronunciation: /tsuːˈnɑːmi/),
also known as a seismic sea wave or as a tidal
wave, is a series of waves in a water body
caused by the displacement of a large volume
of water, generally in an ocean or a large
lake.
Tsunamis can be caused by undersea earthquakes
such as the 2004 Boxing Day tsunami, or by
landslides such as the one in 1958 at Lituya
Bay, Alaska, or by volcanic eruptions such
as the ancient eruption of Santorini.
On March 11, 2011, a tsunami occurred near
Fukushima, Japan and spread through the Pacific
Ocean.
=== Limnic eruptions ===
A limnic eruption occurs when a gas, usually
CO2, suddenly erupts from deep lake water,
posing the threat of suffocating wildlife,
livestock and humans.
Such an eruption may also cause tsunamis in
the lake as the rising gas displaces water.
Scientists believe landslides, volcanic activity,
or explosions can trigger such an eruption.
To date, only two limnic eruptions have been
observed and recorded.
In 1984, in Cameroon, a limnic eruption in
Lake Monoun caused the deaths of 37 nearby
residents, and at nearby Lake Nyos in 1986
a much larger eruption killed between 1,700
and 1,800 people by asphyxiation.
== Meteorological disasters ==
=== 
Cyclonic storms ===
Cyclone, tropical cyclone, hurricane, and
typhoon are different names for the same phenomenon,
which is a cyclonic storm system that forms
over the oceans.
The determining factor on which term is used
is based on where they originate.
In the Atlantic and Northeast Pacific, the
term "hurricane" is used; in the Northwest
Pacific it is referred to as a "typhoon" and
"cyclones" occur in the South Pacific and
Indian Ocean.
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.
=== Blizzards ===
Blizzards are severe winter storms characterized
by heavy snow and strong winds.
When high winds stir up snow that has already
fallen, it is known as a ground blizzard.
Blizzards can impact local economic activities,
especially in regions where snowfall is rare.
The Great Blizzard of 1888 affected the United
States, when many tons of wheat crops were
destroyed, and in Asia, 2008 Afghanistan blizzard
and the 1972 Iran blizzard were also significant
events.
The 1993 Superstorm originated in the Gulf
of Mexico and traveled north, causing damage
in 26 states as well as Canada and leading
to more than 300 deaths.
=== Hailstorms ===
Hailstorms are precipitation in the form of
ice, with the ice not melting before it hits
the ground.
Hailstones usually measure between 0.2 inch
(5 millimetres) and 6 inches (15 centimetres)
in diameter.
A particularly damaging hailstorm hit Munich,
Germany, on July 12, 1984, causing about $2
billion in insurance claims.
=== Ice storms ===
An ice storm is a type of winter storm characterized
by freezing rain.
The U.S. National Weather Service defines
an ice storm as a storm which results in the
accumulation of at least 0.25 inch (6.4 mm)
of ice on exposed surfaces.
=== Cold waves ===
A cold wave (known in some regions as a cold
snap or cold spell) is a weather phenomenon
that is distinguished by a cooling of the
air.
Specifically, as used by the U.S. National
Weather Service, a cold wave is a rapid fall
in temperature within a 24-hour period requiring
substantially increased protection to agriculture,
industry, commerce, and social activities.
The precise criterion for a cold wave is determined
by the rate at which the temperature falls,
and the minimum to which it falls.
This minimum temperature is dependent on the
geographical region and time of year.
=== Heat waves ===
A heat wave is a period of unusually and excessively
hot weather.
The worst heat wave in recent history was
the European Heat Wave of 2003.
A summer heat wave in Victoria, Australia,
created conditions which fuelled the massive
bushfires in 2009.
Melbourne experienced three days in a row
of temperatures exceeding 40 °C (104 °F)
with some regional areas sweltering through
much higher temperatures.
The bushfires, collectively known as "Black
Saturday", were partly the act of arsonists.
The 2010 Northern Hemisphere summer resulted
in severe heat waves, which killed over 2,000
people.
It resulted in hundreds of wildfires which
caused widespread air pollution, and burned
thousands of square miles of forest.
=== Droughts ===
Drought is the unusual dryness of soil caused
by levels of rainfall significantly below
average over a prolonged period.
Hot dry winds, shortage of water, high temperatures
and consequent evaporation of moisture from
the ground can also contribute to conditions
of drought.
Droughts result in crop failure and shortages
of water.
Well-known historical droughts include the
1997–2009 Millennium Drought in Australia
led to a water supply crisis across much of
the country.
As a result, many desalination plants were
built for the first time (see list).
In 2011, the State of Texas lived under a
drought emergency declaration for the entire
calendar year and severe economic losses.
The drought caused the Bastrop fires.
=== Thunderstorms ===
Severe storms, dust clouds, and volcanic eruptions
can generate lightning.
Apart from the damage typically associated
with storms, such as winds, hail, and flooding,
the lightning itself can damage buildings,
ignite fires and kill by direct contact.
Especially deadly lightning incidents include
a 2007 strike in Ushari Dara, a remote mountain
village in northwestern Pakistan, that killed
30 people, the crash of LANSA Flight 508 which
killed 91 people, and a fuel explosion in
Dronka, Egypt caused by lightning in 1994
which killed 469.
Most lightning deaths occur in the poor countries
of America and Asia, where lightning is common
and adobe mud brick housing provides little
protection.
=== Tornadoes ===
A tornado is a violent and dangerous rotating
column of air that is in contact with both
the surface of the Earth and a cumulonimbus
cloud, or the base of a cumulus cloud in rare
cases.
It is also referred to as a twister or a cyclone,
although the word cyclone is used in meteorology
in a wider sense, to refer to any closed low
pressure circulation.
Tornadoes come in many shapes and sizes, but
are typically in the form of a visible condensation
funnel, whose narrow end touches the Earth
and is often encircled by a cloud of debris
and dust.
Most tornadoes have wind speeds less than
110 miles per hour (177 km/h), are approximately
250 feet (80 m) across, and travel a few miles
(several kilometers) before dissipating.
The most extreme tornadoes can attain wind
speeds of more than 300 mph (480 km/h), stretch
more than two miles (3 km) across, and stay
on the ground for dozens of miles (perhaps
more than 100 km).
== Wildfires ==
Wildfires are large fires which often start
in wildland areas.
Common causes include lightning and drought
but wildfires may also be started by human
negligence or arson.
They can spread to populated areas and can
thus be a threat to humans and property, as
well as wildlife.
Notable cases of wildfires were the 1871 Peshtigo
Fire in the United States, which killed at
least 1700 people, and the 2009 Victorian
bushfires in Australia.
== Space disasters ==
=== Impact events and airburst ===
Asteroids that impact the Earth have led to
several major extinction events, including
one which created the Chicxulub crater 64.9
million years ago and which is associated
with the demise of the dinosaurs.
Scientists estimate that the likelihood of
death for a living human from a global impact
event is comparable to the probability of
death from an airliner crash.
No human death has been definitively attributed
to an impact event, but the 1490 Ch'ing-yang
event in which over 10,000 people may have
died has been linked to a meteor shower.
Even asteroids and comets that burn up in
the atmosphere can cause significant destruction
on the ground due to the air burst explosion:
notable air bursts include the Tunguska event
in June 1908, which devastated large areas
of Siberian countryside, and the Chelyabinsk
meteor on 15 February 2013, which caused widespread
property damage in the city of Chelyabinsk
and injured 1,491.
=== Solar flare ===
A solar flare is a phenomenon where the Sun
suddenly releases a great amount of solar
radiation, much more than normal.
Solar flares are unlikely to cause any direct
injury, but can destroy electrical equipment.
The potential of solar storms to cause disaster
was seen during the 1859 Carrington event,
which disrupted the telegraph network, and
the March 1989 geomagnetic storm which blacked
out Quebec.
Some major known solar flares include the
X20 event on August 16, 1989, and a similar
flare on April 2, 2001.
The most powerful flare ever recorded occurred
on November 4, 2003 (estimated at between
X40 and X45).
== Protection by international law ==
International law, for example Geneva Conventions
defines International Red Cross and Red Crescent
Movement the Convention on the Rights of Persons
with Disabilities, requires that "States shall
take, in accordance with their obligations
under international law, including international
humanitarian law and international human rights
law, all necessary measures to ensure the
protection and safety of persons with disabilities
in situations of risk, including the occurrence
of natural disaster."
And further United Nations Office for the
Coordination of Humanitarian Affairs is formed
by General Assembly Resolution 44/182.
People displaced due to natural disasters
are currently protected under international
law (Guiding Principles of International Displacement,
Campala Convention of 2009).
== Location ==
According to the UN, Asia-Pacific is the world's
most disaster prone region.
According to ReliefWeb, a person in Asia-Pacific
is five times more likely to be hit by a natural
disaster than someone living in other regions.
== Political consequences ==
Natural disasters can also affect political
relations with countries and vice versa.
Violent conflicts within states can exacerbate
the impact of natural disasters by weakening
the ability of states, communities and individuals
to provide disaster relief.
Natural disasters can also worsen ongoing
conflicts within states by weakening the capacity
of states to fight rebels.
In developed countries like the US, studies
find that incumbents lose votes when the electorate
perceives them as responsible for a poor disaster
response.
In Chinese and Japanese history, it has been
routine for era names and/or capital cities
and palaces of emperors to be changed after
a major natural disaster, chiefly for political
reasons such as association with hardships
by the populace and fear of upheaveal.
(i.e. in East asian government chronicles,
such fears were recorded in a low profile
way as an unlucky name or place requiring
change.)
Disasters and responses can dictate political
careers; the once popular President Benigno
Aquino III of Philippines, following a weak
and confused response to Typhoon Yolanda which
killed over 6,000 people and survivors were
largely left to fend for themselves, this
widely accepted sentiment carried over and
the President never recovered his popularity,
his hand picked successor Mar Roxas lost the
subsequent election to a rival party in a
landslide vote.
Post-disaster mishandling can spread despair
as bad news travels fast and far, and contribute
to the appeal of electing a strongman out
of sheer desperation.
== Recent history ==
Between 1995 and 2015, according to the UN’s
disaster-monitoring system, the greatest number
of natural disasters occurred in America,
China and India.In 2012, there were 905 natural
disasters worldwide, 93% of which were weather-related
disasters.
Overall costs were US$170 billion and insured
losses $70 billion.
2012 was a moderate year.
45% were meteorological (storms), 36% were
hydrological (floods), 12% were climatological
(heat waves, cold waves, droughts, wildfires)
and 7% were geophysical events (earthquakes
and volcanic eruptions).
Between 1980 and 2011 geophysical events accounted
for 14% of all natural catastrophes.Studies
on natural events require complete historical
records and strategies related to obtaining
and storing reliable records, allowing for
both critical interpretation and validation
of the sources.
Under this point of view the irreplaceable
role of traditional repositories (archives)
can be supplemented by the use of such web
sources as eBay.
== See also ==
Act of God
Civil defense
Disaster risk reduction
Emergency management
Emergency sanitation
Environmental disaster
Environmental emergency
List of countries by natural disaster risk
List of environmental disasters
List of natural disasters by death toll
World Conference on Disaster Risk Reduction
