This ppt will help you know a few things about natural disasters

2. NATURAL DISASTERS
A natural disaster is a major adverse event resulting
from natural processes of the Earth; examples
include floods volcanic eruptions,
earthquakes, tsunamis, and other geologic processes.
A natural disaster can cause loss of life or property
damage, and typically leaves some economic damage
in its wake, the severity of which depends on the
affected population's resilience, or ability to recover.

3. SOME NATURAL DISASTERS
 TSUNAMI
 EARTHQUAKE
 FLOOD
 LANDSLIDES
 VOLCANIC ERUPTION
 AVALANCHE
 BLIZZARD
 HURRICANE
 DROUGHT

4.  SANDSTORM
 THUNDERSTORM
 SEASTORM
 TORNADO
 ACID RAIN
 FOREST FIRE
 FAMINE
 HAILSTORM

5. TSUNAMI
A tsunami . "harbour wave”, 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. Earthquakes volcanic
eruptions and other underwater explosions (including
detonations of underwater nuclear devices, landslides, glacier
, meteorite impacts and other disturbances above or below
water all have the potential to generate a tsunami. In being
generated by the displacement of water, a tsunami contrasts
both with a normal ocean wave generated by wind and
with tides, which are generated by the gravitational pull of
the Moon and the Sun on bodies of water.

6. CHARACTERISTICS
Tsunamis cause damage by two mechanisms: the
smashing force of a wall of water travelling at high
speed, and the destructive power of a large volume of
water draining off the land and carrying a large
amount of debris with it, even with waves that do not
appear to be large. While everyday wind waves have
a wavelength of about 100 metres (330 ft) and a height
of roughly 2 metres (6.6 ft), a tsunami in the deep
ocean has a much larger wavelength of up to 200
kilometres (120 mi). Such a wave travels at well over
800 kilometres per hour (500 mph),

10. TSUNAMI RISK ZONES

11. EARTHQUAKE
 An earthquake is the perceptible shaking of the surface
of the Earth, which can be violent enough to destroy
major buildings and kill thousands of people. The
severity of the shaking can range from barely felt to
violent enough to toss people around. Earthquakes have
destroyed whole cities. They result from the 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.

12. Earthquakes are measured using observations
from seismometers. The moment magnitude is the most
common scale on which earthquakes larger than
approximately 5 are reported for the entire globe. The more
numerous earthquakes smaller than magnitude 5 reported by
national seismological observatories are measured mostly on
the local magnitude scale, also referred to as the Richter
magnitude scale. These two scales are numerically similar
over their range of validity. Magnitude 3 or lower
earthquakes are mostly almost imperceptible or weak and
magnitude 7 and over potentially cause serious damage over
larger areas, depending on their depth.

13. AFTERSHOCKS
An aftershock is an earthquake that occurs after a
previous earthquake, the main shock. An aftershock is in
the same region of the main shock but always of a
smaller magnitude. If an aftershock is larger than the
main shock, the aftershock is redesignated as the main
shock and the original main shock is redesignated as
a foreshock. Aftershocks are formed as the crust around
the displaced fault plane adjusts to the effects of the main
shock.

17. FLOOD
A flood is an overflow of water that submerges land which is
usually dry. A flood as a covering by water of land not
normally covered by water.[2 In the sense of "flowing water",
the word may also be applied to the inflow of the tide
. Flooding may occur as an overflow of water from water
bodies, such as a river or lake, in which the water overtops ,
resulting in some of that water escaping its usual boundaries,
or it may occur due to an accumulation of rainwater on
saturated ground in an areal flood. While the size of a lake or
other body of water will vary with seasonal changes
in precipitation and snow melt, these changes in size are
unlikely to be considered significant unless they
flood property or drown domestic animals.

18. The primary effects of flooding include loss of life, damage to buildings and other
structures, including bridges, sewerage systems, roadways, and canals.
Floods also frequently damage power transmission and sometimes power
generation, which then has knock-on effects caused by the loss of power. This
includes loss of drinking water treatment and water supply, which may result in
loss of drinking water or severe water contamination. It may also cause the loss of
sewage disposal facilities. Lack of clean water combined with human sewage in the
flood waters raises the risk of waterborne diseases, which can
include typhoid, cholera and many other diseases depending upon the location of
the flood.
Damage to roads and transport infrastructure may make it difficult to mobilize aid
to those affected or to provide emergency health treatment.
Flood waters typically inundate farm land, making the land unworkable and
preventing crops from being planted or harvested, which can lead to shortages of
food both for humans and farm animals. Entire harvests for a country can be lost
in extreme flood circumstances. Some tree species may not survive prolonged
flooding of their root systems

19. BENIFITS
Floods can also bring many benefits, such as
recharging ground water, making soil more fertile and
increasing nutrients in some soils. Flood waters provide much
needed water resources in arid and semi-arid regions where
precipitation can be very unevenly distributed throughout the
year and kills pests in the farming land. Freshwater floods
particularly play an important role in
maintaining ecosystems in river corridors and are a key factor
in maintaining floodplain bio diversity. Flooding can spread
nutrients to lakes and rivers, which can lead to
increased biomass and improved fisheries for a few years.
For some fish species, an inundated floodplain may form a
highly suitable location for spawning with few predators and
enhanced levels of nutrients or food.

22. LANDSLIDES
A landslide, also known as a landslip, is a geological
phenomenon that includes a wide range of ground
movements. Rockfalls, deep failure of slopes and
shallow debris flows were common. Landslides 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.

23. Landslides occur when the stability of the 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 (pore water) pressure acting to destabilize the slope
Loss or absence of vertical vegetative structure, soil nutrients, and soil
structure (e.g. after a wildfire - a fire in forests lasting for 3–4 days)
erosion of the toe of a slope by rivers or ocean waves
weakening of a slope through saturation by snow
melt, glaciers melting, or heavy rains
earthquakes adding loads to barely stable slope
earthquake-caused liquefaction destabilizing slopes
volcanic eruptions