Natural Disaster
A natural disaster is a major adverse event resulting
from natural processes of the Earth;
examples are floods, hurricanes, tornadoes, volcanic eruptions, earthquakes, tsunamis, storms, 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 (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.
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.
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.
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.
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,[14] 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,[17] 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).
0 Comments