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2. NATURAL
DISASTERS
A natural disaster is the effect of a natural
hazard(e.g flood, tornado, volcanoes,
earthquake,landslide,hurricanes,forest
fire,cyclone,famine,tsunamis) 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 meet vulnerability." A natural
hazard will hence never result in a
natural disaster in areas without
vulnerability, e.g. strong earthquakes in
uninhabited areas.

4. An Earthquake is a sudden shake of the Earth's crust.The vibrations may
vary in magnitude.The magnitude of an earthquake is measured on the
richter scale. The underground point of origin of the earthquake is called
the "focus". The point directly above the focus on the surface is called
the"epicentre". Siesmologists are earthquake scientists,measure the
strength of an earthquake by estimating the amount of energy released at
the focus. 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, that are actually the
human disaster. As many of these could be avoided by better
construction, safety systems, early warning and evaluation planning.
Seismic waves are detected, recorded and measured by seismographs.
Earthquakes are caused by the discharge of accumulated along geologic
faults.

5. Earthquake Disasters
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.
 The 7.9 magnitude May 12, 2008 Sichuan earthquake
in Sichuan Province, China. Death toll at over 61,150
as of May 27, 2008

7. TORNADO
• Some of the most violent tornadoes develop
from supercell thunderstorms. A supercell
thunderstorm is a long-lived thunderstorm
possessing within its structure a continuously
rotating updraft of air. These storms have the
greatest tendency to produce tornadoes,
some of the huge wedge shape. The supercell
thunderstorm has a low-hanging, rotating layer
of cloud known as a “wall cloud.” It looks
somewhat like a layer of a layer cake that
hangs below the broader cloud base. One
side of the wall cloud is often rain-free, while
the other is neighbored by dense shafts of
rain. The rotating updraft of the supercell is
seen on radar as a “mesocyclone.”
• The tornadoes that accompany supercell
thunderstorms are more likely to remain in
contact with the ground for long periods of
time—an hour or more—than other tornadoes,
and are more likely to be violent, with winds
exceeding 200 mph.

9. LANDSLiDES
 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 factors
affecting the original slope
stability. Typically, pre-conditional
factors build up specific sub-
surface conditions that make the
area/slope prone to failure,
whereas the actual landslide often
requires a trigger before being
released.

10. CAUSES OF LANDSLIDES
Landslides occur when the stability of a slope changes from a
stable to an unstable condition. A change in the stability of a
slope can be caused by a number of factors, acting together or
alone. Natural causes of landslides include:-
 groundwater (porewater) pressure acting to destabilize the slope
 Loss or absence of vertical vegetative structure, soil nutrients,
and soil structure (e.g. after a wildfire)
 erosion of the toe of a slope by rivers or ocean waves
 weakening of a slope through saturation by snowmelt, glaciers
melting, or heavy rains
 earthquakes adding loads to barely-stable slopes
 earthquake-caused liquefaction destabilizing slopes volcanic
eruptions

12. volcanoes
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. The word volcano is
derived from the name of Vulcano island off Sicily
which in turn, was named after Vulcan, the Roman god
of fire.
Volcanoes are generally found where tectonic plates are
diverging or converging. 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.
Mount Bromo, East Java, Indonesia. Irazú Volcano, Costa Rica.

13. HOW VOLCANOES
OCCUR?
As the magma chamber fills with the gas-filled magma, pressure
builds up. Weight from the solid rock surrounding the area
contributes to the force of this pressure. When the magma
pushes its way up to the sur face, it breaks or weakens
fractures in the surrounding solid rock. As the magma reaches
the sur face, gas is released and the magma blasts an opening
through the ear th's sur face. The material that is pushed up
helps to create the mountain that surrounds a volcano. Not all
the magma or materials that are pushed up the magma
chamber are expelled from the opening. Instead of reaching
the sur face it may escape through channels or remain

15. FLOODS
A flood is an overflow of water that
submerges land, producing
measurable property damage or
forcing evacuation of people and
vital resources. Floods develop
slowly as rivers swell during an
extended period of rain, or during a
warming trend following a heavy
snow. Even a very small stream or
dry creek bed can overflow and
create flooding.
A flood occurs when water overflows or
inundates land that's normally dry.
This can happen in a multitude of
ways. Most common is when rivers or
streams overflow their banks.
Excessive rain, a ruptured dam or
levee, rapid ice melting in the
mountains, or even an unfortunately
placed beaver dam can overwhelm a
river and send it spreading over the
adjacent land, called a floodplain.
Coastal flooding occurs when a large
storm or tsunami causes the sea to
surge inland.

17. 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, intense
drought can cause significant damage and
harm the local economy.

18. EFFECTS OF DROUGHT
 Rise in Temperature
Droughts may be linked to a rise in temperature
which may bring insects like locusts and
mosquitoes.
 Hunger and famine
In a drought there may be not enough water to grow
crops, or enough grass and rich can buy. If there is
no food people go hungry, and grain to feed
animals. Food prices will go up and only the if the
drought goes for a long time there may be famine,
when people die.
 Thirst
Humans, animals and plants and trees all need
water to survive. Humans can only live a few days
without water.
 Disease
If there is no water for drinking, bathing or even
flushing toilets, there can be a wide range of
dangerous diseases.
 Land Degradation
If there is no water the plants holding down the soil
will die, and winds can quickly strip the land of
topsoil. The natural habitat of native animals is
damaged and some may not survive. Wetlands and
lakes may dry up.
 Bushfires
When there is no water everything dries up,
including the forests and bush. Lightning strikes or
carelessness often starts huge bushfires that burn
animals, houses and property. Humans are also
killed in bushfires.

20. HURRICANES
A hurricane is a powerful, spiraling storm that begins over a warm sea,
near the equator. A storm is classified as a hurricane when the speed
of wind reaches 74 miles (119 kilometers) per hour. Hurricane storms
usually start over warm sea (near the equator) and are accompanied
by fierce winds, flash floods, mudslides and huge waves.
Their source of energy is water vapor which is evaporated from the ocean
surface. Water vapor is the "fuel" for the hurricanes because it
releases the "latent heat of condensation" when it condenses to form
clouds and rain, warming the surrounding air. (This heat energy was
absorbed by the water vapor when it was evaporated from the warm
ocean surface, cooling the ocean in the process.) Usually, the heat
released in this way in tropical thunderstorms is carried away by wind
shear, which blows the top off the thunderstorms. But when there is
little wind shear, this heat can build up, causing low pressure to form.
The low pressure causes wind to begin to spiral inward toward the
center of the low. These winds help to evaporate even more water
vapor from the ocean, spiraling inward toward the center, feeding
more showers and thunderstorms, and warming the upper
atmosphere still more. The showers and thunderstorms where all of
this energy is released are usually organized into bands (sometimes
called "rain bands" or "feeder bands"), as well as into an "eye wall"
encircling the center of the storm. The eye wall is where the strongest
winds occur, which encircle the warmest air, in the eye of the
hurricane. This warmth in the eye is produced by sinking air, which
sinks in response to rising air in the thunderstorms. The winds
diminish rapidly moving from the eye wall to the inside of the
relatively cloud-free eye, where calm winds can exist.

22. Famine has af flicted societies since the beginning of histor y. It may be
defined as a persistent failure in food supplies over a prolonged
period. It is something experienced by society, whereas star vation is
something that af fects individuals. During famines more people are
likely to die of famine related diseases than from star vation. The
causes are complex. Adver se weather conditions (drought, excessive
rain, intense cold) at crucial times, ef fects of war (scorched ear th
policies, the provisioning of armies, disruption of trade), pestilence
and disease: all these individually or in combination may be to blame.

24. TSUNAMI
A tsunami is a series of waves generated when a body of water, such
as a lake or ocean is rapidly displaced on a massive scale.
Earthquakes, landslides, volcanic eruptions and large meteorite
impacts all have the potential to generate a tsunami. The effects
of a tsunami can range from unnoticeable to devastating.
DISASTER CAUSED BY TSUNAMIS-
• The highest Tsunami was 85m on April 24th, 1771, Japan.
• The 2004 Indian Ocean Earthquake ranks as the deadliest
tsunami in recorded history
• In 1964, an Alaskan earthquake generated a tsunami with waves
between 10 and 20 feet high along parts of the California,
Oregon and Washington coasts.
• In 1946, a tsunami with waves of 20 to 32 feet crashed into Hilo,
Hawaii, flooding the downtown area.

26. FOREST FIRE
Forest fires are the uncontrolled
destruction of forested lands caused
by natural or human-made wild
fire. The probability of a wildfire in
any one locality on a particular day
depends on fuel conditions,
topography, the time of year, wind
direction and speed, the past and
present weather conditions, and
the activities (debris burning, land
clearing, camping, etc.) that are or
will be taking place. Controlled
burns are also conducted because
the fire cycle is an important aspect
of management for many
ecosystems. These are not
considered hazards unless they
were to get out of control.

28. CYCLONES
Cyclone, atmospheric pressure distribution in which there is a
low central pressure relative to the surrounding pressure.
The resulting pressure gradient, combined with the
Coriolis effect, causes air to circulate about the core of
lowest pressure in a counterclockwise direction in the
Northern Hemisphere and in a clockwise direction in the
Southern Hemisphere. Near the surface of the earth, the
frictional drag on the air moving over land or water causes
it to spiral gradually inward toward lower pressures. This
inward movement of air is compensated for by rising
currents near the center, which are cooled by expansion
when they reach the lower pressures of higher altitudes.
The cooling, in turn, greatly increases the relative humidity
of the air, so that "lows" are generally characterized by
cloudiness and high humidity; they are thus often referred
to simply as storms.

29. FORMATION OF CYCLONES
Cyclones form af ter the ocean water warms up
past 27 deg C (80 deg F). Warm water
evaporates faster than cold water, so the air
above has high amounts of water vapor.
Water vapor that condenses to form cloud
droplets gives of f heat into the air. This heat
is added to the tropical air that is already
warm. This causes a large pulse of heat to
rise high into the atmosphere. If sur face
winds and atmospheric winds are traveling in
the same direction, the warm air is
concentrated in one spot, this then forms
bands of spiraling thunder storms. As they
spin they blow inward toward the center, rain
is ver y heavy in these bands, but between
the bands it is raining lightly or not at all.
The most violent band with the heaviest rain
is the eyewall, which surrounds the eye or
center of the cyclone. The average size of the
eye is about 24 km (15 miles) in diameter. All
the updraf ts of the thunder storms spread out
when they hit the stratosphere forming a
continuous cloud shield above the storm.
Barometric pressure in the middle of the
mass drops, causing the wind speed to
increase. This wind whips the ocean into a