Natural disasters are events caused by natural hazards like floods, earthquakes, volcanoes, etc. that lead to damage and losses. The impact of a natural hazard depends on the vulnerability of the affected population - their ability to resist the hazard. While hazards exist naturally, it is human settlement and involvement that transforms them into disasters. Several types of natural hazards are described in detail, including earthquakes, landslides, tsunamis, volcanoes, floods, and thunderstorms. Common causes and effects of each hazard are summarized.

2. A natural disaster is the effect of the earth's natural
hazards, for example flood, tornado, hurricane, volcanic
eruption, earthquake, heatwave, or landslide. They can
lead to financial, environmental or human losses. The
resulting loss depends on the vulnerability of the
affected population to resist the hazard, also called their
resilience. If these disasters continue it would be a great
danger for the earth.[1] This understanding is
concentrated in the formulation: "disasters occur when
hazards meet vulnerability."[2] Thus a natural hazard will
not result in a natural disaster in areas without
vulnerability, e.g. strong earthquakes in uninhabited
areas.[3] The term natural has consequently been
disputed because the events simply are not hazards or
disasters without human involvement.[4] A concrete
example of the division between a natural hazard and a
natural disaster is that the 1906 San Francisco
earthquake was a disaster, whereas earthquakes are a
hazard. This article gives an introduction to notable
natural disasters, refer to the list of natural disasters for
a comprehensive listing.

4. 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. The vibrations may vary in
magnitude. Earthquakes are caused mostly by slippage within
geological faults, but also by other events such as volcanic
activity, landslides, mine blasts, and nuclear tests. The underground
point of origin of the earthquake is called the 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, that are
actually the human disaster. Many of these could possibly be
avoided by better construction, safety systems, early warning and
evacuation planning.

8. A landslide or landslip is a geological phenomenon which includes a wide range of
ground movement, such as rockfalls, 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 subsurface conditions that make the area/slope prone to failure, whereas the actual landslide
often requires a trigger before being released.
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 slope
earthquake-caused liquefaction destabilizing slopes
volcanic eruptions

11. A tsunami (plural: tsunamis or tsunami; from Japanese: 津波, lit. "harbor wave";[1] English
pronunciation: /suːː
nɑːmi soo-NAH-mee or /tsuːː
/
nɑːmi tsoo-NAH-mee[2]) is a series of
/
water waves caused by the displacement of a large volume of a body of water, typically an ocea
or a large lake. Earthquakes, volcanic eruptions and other underwater explosions (including
detonations of underwater nuclear devices), landslides, glacier calvings, meteorite impacts an
other disturbances above or below water all have the potential to generate a tsunami.
Tsunami waves do not resemble normal sea waves, because their wavelength is far longer.
Rather than appearing as a breaking wave, a tsunami may instead initially resemble a
rapidly rising tide, and for this reason they are often referred to as tidal waves. Tsunamis
generally consist of a series of waves with periods ranging from minutes to hours, arriving
in a so-called "wave train".[4] Wave heights of tens of metres can be generated by large
events. Although the impact of tsunamis is limited to coastal areas, their destructive power
can be enormous and they can affect entire ocean basins; the 2004 Indian Ocean tsunami
was among the deadliest natural disasters in human history with over 230,000 people killed
in 14 countries bordering the Indian Ocean.

15. A volcano is an opening, or rupture, in a planet's surface or crust, which
allows hot magma, volcanic ash and gases to escape from below the surface.
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. Volcanoes can also form where
there is stretching and thinning of the Earth's crust in the interiors of plates,
e.g., in the East African Rift, the Wells Gray-Clearwater volcanic field and the
Rio Grande Rift in North America. This type of volcanism falls under the
umbrella of "Plate hypothesis" volcanism.[1] Volcanism away from plate
boundaries has also been explained as mantle plumes. These so-called
"hotspots", for example Hawaii, are postulated to arise from upwelling diapirs
with magma from the core-mantle boundary, 3,000 km deep in the Earth.

18. A flood is an overflow of an expanse of water that submerges land.[1] The European Union
(EU) Floods Directive defines 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 result from the volume of water within a body of water, such as a
river or lake, which overflows or breaks levees, with the result that some of the water
escapes 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 such escapes of water
endanger land areas used by man like a village, city or other inhabited area.
Floods can also occur in rivers, when flow exceeds the capacity of the river
channel, particularly at bends or meanders. Floods often cause damage to homes and
businesses if they are placed in natural flood plains of rivers. While flood damage can be
virtually eliminated by moving away from rivers and other bodies of water, since time out of
mind, people have lived and worked by the water to seek sustenance and capitalize on the
gains of cheap and easy travel and commerce by being near water

21. A thunderstorm, also known as an electrical storm, a lightning
storm, thundershower or simply a storm is a form of weather characterized by the
presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder.[1]
The meteorologically assigned cloud type associated with the thunderstorm is the
cumulonimbus. Thunderstorms are usually accompanied by strong winds, heavy rain and
sometimes snow, sleet, hail, or no precipitation at all. Those that cause hail to fall are called
hailstorms. Thunderstorms may line up in a series or rainband, known as a squall line.
Strong or severe thunderstorms may rotate, known as supercells. While most
thunderstorms move with the mean wind flow through the layer of the troposphere that
they occupy, vertical wind shear causes a deviation in their course at a right angle to the
wind shear direction.
Thunderstorms result from the rapid upward movement of warm, moist air. They can occur
inside warm, moist air masses and at fronts. As the warm, moist air moves upward, it
cools, condenses, and forms cumulonimbus clouds that can reach heights of over 20 km. As
the rising air reaches its dew point, water droplets and ice form and begin falling the long
distance through the clouds towards the Earth's surface. As the droplets fall, they collide
with other droplets and become larger. The falling droplets create a downdraft of air that
spreads out at the Earth's surface and causes strong winds associated commonly with
thunderstorms.

24. Thanks a lot for listening carefully
and I hope that you have enjoyed and
benefited from the presentation
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Paras gang