Natural and Man - made Hazards
Natural Hazards :
When hazards occur due to natural forces they are called natural hazards,
over which man has hardly any control.
Man-made hazards :
When the disasters are due to carelessness of human or mishandling of
dangerous equipment’s they are called man-made hazards.
Natural and Man - made Hazards
• Momentary Natural Geological Events e.g. earthquake, volcanic
eruption, landslides
• Meteorological Events such as cyclones, lightening, fires, drought,
avalanche etc.
• Oceanographic Events such as Tsunami
• Hydrological Events such as floods
• Biological Event such as epidemic
• Technological Event such as explosion, structural collapse, release of
toxic materials, global warming, pollution
• Social/anthropogenic events such as terrorism, political conflict, war
etc.
Natural Hazards
Earthquake, fire, floods, cyclones, avalanche
classification and their
characteristics,
causes and effects.
Earthquake
Ground movement caused by the sudden release of seismic energy due to tectonic forces.
The earth is primarily composed
of three layers:
1. The outer crust,
2. The middle mantle, and
3. The inner core
The Earth’s outer layer or crust is
made up of a number of zig-saw
pieces like structures that interlock
into one another. These pieces are
called tectonic plates. These
plates are in continuous motion
over the mantle. When these plates
contact each others, stress arise on
the crust ,which is known as
tectonic movements.
http://www.slideshare.net/kamalbrar/natural-hazards-and-disastertypesmitigation-and-management
http://www.biologydiscussion.com/essay/natural-and-man-made-disaster-and-their-impact-on-environment/7134
Earthquake
These stresses can be classified according to the type of movement along the plate’s boundaries :
a) Pulling away from each other
b) Pushing against one another and
c) Sliding sideways relative to each other.
a b c
When the stress on the rocks exceeds certain limits, the rocks rupture and form a fault along which
the rocks are displaced during tectonic movements. This sudden rupture of the rocks releases energy
in the form of earthquake waves called seismic waves.
Earthquake
Measuring earthquakes
Earthquakes can be described by the use of two distinctively different scales :
Earthquake magnitude: to measure the amount of energy released. Instrument records seismic waves
is called seismograph
Earthquake intensity : to measure the effects of an earthquake where it occur. The Richter scale is
used to measure the intensity of earthquakes.
http://www.biologydiscussion.com/essay/natural-and-man-made-disaster-and-their-impact-on-environment/7134
Earthquake
Seismic zone
Most
vulnerable
zone
Earthquake
Impact of Earthquake on the Environment:
Shaking of the ground and surface rupture:
This is the main cause of destruction in which buildings, bridges, roads, canals and other
structures are damaged.
Liquefaction:
Earthquakes make sands and silts to transform from a solid to liquid state. This also results in
building collapse.
Landslides:
Earthquakes of high intensity often trigger many landslides in the hilly regions.
Fires:
It is a major hazard associated with earthquakes. The shakings of the ground and building
damage often break the gas pipes and electric lines that cause fires.
Changes in the land elevation:
The surface topography of a region and groundwater conditions are altered after an
earthquake.
http://www.biologydiscussion.com/essay/natural-and-man-made-disaster-and-their-impact-on-environment/7134
Earthquake
Impact of Earthquake on the Environment:
Pyne Gould Guinness Building: collapsed at Christchurch
Earthquake
Impact of Earthquake on the Environment:
Chile Earthquake, 27 February 2010 Magnitude 8.8
Earthquake
Impact of Earthquake on the Environment:
Gujarat Earthquake 2001
Earthquake
Impact of Earthquake on the Environment:
Kashmir Earthquake October 2005
Earthquake
Impact of Earthquake on the Environment:
Floods
Floods
Flood is a state of high water level along a river channel or on the coast that leads to
inundation of land ,which is not usually submerged.
Floods occur due to heavy rainfall within a short duration of time in a particular region
which causes the rivers and streams to overflow.
Causes of floods
Floods
Types of floods :
1) Flash floods- Flash floods give the least amount of warning time. They are characterized
as a rapid and significant rise in water level due to a sudden and intense heavy rainfall
event. These floods occur when rainfall rates are so high that the ground cannot absorb the
water quickly enough to prevent significant runoff and are especially common in areas with
steep slopes.
Uttarakhand flash floods
June 2013
The multi-day cloudburst in the hill state of Uttarakhand triggered flash
floods and massive landslides.
Floods
Types of floods :
2) River floods- They are caused when water runoff collects in rivers and streams and
eventually reaches levels that overflow the banks. When this occurs, the flood can cover an
enormous area and affect downstream areas even if they didn’t receive much rain
themselves.
Mississippi River flood,
2008
Floods
Types of floods :
3) Coastal floods- These floods occur when ocean water is pushed inland. Hurricanes and
tropical storms can cause large waves and actually raise the sea level, creating storm
surge along beaches.
Flooding in Visakhapatnam, 2012
file:///C:/Users/Pari/Downloads/Types%20of%20Floods.pdf
Floods
Types of floods :
4) Urban floods- Urban floods can be caused by flash, river or coastal flooding but most
commonly, it is caused by high rainfall rates over developed areas that do not have the
ability to absorb the water.
Mumbai floods, 2011 Chennai floods, 2015
Floods
Impact on the Environment:
Though the lives lost in floods may not be as high as in case of earthquakes or cyclones,
the damage to the environment is immense. The problem is further aggravated if the
floods last for a longer duration of time.
Floods not only damage property and endanger if lives of humans and animals, but
have other effects as well, such as:
1. Floods cause the spread of many epidemic diseases.
2. Rapid runoff causes soil erosion.
3. Wildlife habitat and forests are often destroyed.
4. Manmade structures like buildings, bridges, roads, sewer lines, power lines, etc. are
damaged.
5. Floods cause widespread damage to the standing crops and degrade the agricultural
land.
6. Flood affected areas are faced with acute shortage of food and drinking water.
http://www.biologydiscussion.com/essay/natural-and-man-made-disaster-and-their-impact-on-environment/7134
Floods
Impact on the Environment:
http://www.biologydiscussion.com/essay/natural-and-man-made-disaster-and-their-impact-on-environment/7134
Tsunami
Tsunami
Tsunami is a series of huge waves which originate by rapid displacement of water from the
sea either by seismic activity , landslide , volcanic eruptions or large meteoric impacts.
Whatever the cause may be, sea water is displaced with a violent motion and swell up,
ultimately surging over land with great destructive power.
http://www.slideshare.net/ebinsanty/tsunami-a-natural-disater
Tsunami
Tsunami have a small amplitude ( wave height) offshore, and a very long wavelength (often
hundred of km long), which is why they generally pass unnoticed at sea, forming only a
slight swell usually about 300 mm above the normal sea surface. They grow in height when
they reach shallower water, in a wave shoaling process. A tsunami can occur in any tidal
state and even at low tide can still inundate coastal areas.
http://www.slideshare.net/ebinsanty/tsunami-a-natural-disater
Tsunami
Causes of Tsunami
http://www.slideshare.net/ebinsanty/tsunami-a-natural-disater
Tsunami
Causes of Tsunami
http://www.biologydiscussion.com/essay/natural-and-man-made-disaster-and-their-impact-on-environment/7134
Tsunami
Causes of Tsunami
http://www.biologydiscussion.com/essay/natural-and-man-made-disaster-and-their-impact-on-environment/7134
Tsunami
Effects of Tsunami
http://www.slideshare.net/sannidhisandeep/effects-of-earthquake-and-tsunami
Tsunami
http://www.slideshare.net/sciencepowerpointcom/tsunami-earth-science-lesson-powerpoint
Tsunami
http://www.slideshare.net/sciencepowerpointcom/tsunami-earth-science-lesson-powerpoint
Tsunami
Tsunami in Chennai , 2004
Tsunami
http://www.slideshare.net/sciencepowerpointcom/tsunami-earth-science-lesson-powerpoint
Cyclones
Cyclones
Cyclone is an area of low atmospheric
pressure surrounded by a wind system
blowing in anti-clockwise direction, formed in
the northern hemisphere and in clockwise
direction in Southern Hemisphere. They
occur mainly in the tropical and temperate
regions of the world
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Cyclones
Formation of Tropical Cyclones
http://www.slideshare.net/breannej35/the-physical-characteristics-of-tropical-cyclones
Cyclones
Formation of Tropical Cyclones
• Tropical cyclones form
only over warm ocean
waters near the equator.
• To form a cyclone, warm,
moist air over the ocean
rises upward from near the
surface. As this air moves
up and away from the
ocean surface, it leaves is
less air near the surface.
So basically as the warm
air rises, it causes an
area of lower air pressure
below
• Air from surrounding areas with higher air pressure pushes in to the low pressure area.
Then this new “cool” air becomes warm and moist and rises, too. And the cycle continues..
• As the warmed, moist air rises and cools the water in the air forms clouds. The whole system of
clouds and wind spins and grows, fed by the ocean’s heat and water evaporating from the ocean
surface.
• As the storm system rotates faster and faster, an eye forms in the centre. It is very calm and
clear in the eye, with very low air pressure. Higher pressure air from above flows down into the eye.
https://sites.google.com/site/disasterportal/stroms_cyclones/cyclone-formation
Cyclones
Tropical Cyclones categories
http://www.biologydiscussion.com/essay/natural-and-man-made-disaster-and-their-impact-on-environment/7134
Cyclones
The impact on the environment
The coastal low lying areas are most affected.
2. The affected areas are inundated both with rainfall and the surge of seawater.
3. Devastation is also increased due to the accompanying high velocity winds.
4. Widespread damage in the form of uprooted trees, blown-off roof tops, standing
crops, injuries and death to humans and animals.
5. Many shipwrecks occur during cyclonic storms.
6. The affected areas are impoverished and are followed by spread of epidemic and
diseases.
Cyclones
http://www.slideshare.net/breannej35/the-physical-characteristics-of-tropical-cyclones
Cyclones
http://www.slideshare.net/breannej35/the-physical-characteristics-of-tropical-cyclones
Cyclones
Orissa cyclone , 1999
Cyclones
Japan
Cyclones
http://www.biologydiscussion.com/essay/natural-and-man-made-disaster-and-their-impact-on-environment/7134
Landslides
Landslides
The term landslides includes all varieties of mass movement of hill slopes and can be
defined as the downward and outward movement of slope forming materials composed of
rocks , soils, artificial fills or combination of all these materials along surfaces of separation
by falling , sliding and flowing either slowly or quickly from one place to another.
Although the landslides are primarily associated with mountainous terrains, these can also occur in areas
where an activity such as surface excavations for highways , buildings and open pit mines takes place.
Landslides
Common types of landslides- Types of rapid mass movement
http://www.slideshare.net/ctlachu/14-landslide
Landslides
Common types of Landslides
1. Slides -
Landslides
Common types of Landslides
2. Lateral spreading 3. Debris Flow
Landslides
Common types of Landslides
4. Rock Fall 5. Rock toppling
http://www.slideshare.net/surendra_slide/landslide-15656985
Landslides
Common types of landslides
6. Creep – Slow , steady down slope movement of soil or rock , often indicated by curved
tree trunks , bent fences or retaining walls , tilted poles or fences.
http://www.slideshare.net/ctlachu/14-landslide
Landslides
Causes of landslides
A) Natural factors
1. Gravity – Gravity works more effectively on steeper slopes.
2. Geological Factors- Geology setting that places permeable sands and gravels above
impermeable layers of silts and clay or bedrock
3. Heavy and prolonged rainfall: Slides occur often with intense rain by creating zones of
weakness , also water tables rise with heavy rain makes some slopes unstable.
4. Earthquake: Ground vibrations created during earthquakes .
http://www.slideshare.net/surendra_slide/landslide-15656985
Landslides
Causes of landslides
5. Waves : Wave action can erode the
beach or the toe of a cliff , cutting into
the slope , and setting the stage for
future slides.
6. Volcanoes : Volcanic ash
deposits are prone to
erosion and subjected to
mud flow due to intense
rainfall.
7. Fluctuation of water : due
to the tidal action.
http://www.slideshare.net/surendra_slide/landslide-15656985
Landslides
Causes of landslides
B) Anthropogenic Factors
http://www.slideshare.net/surendra_slide/landslide-15656985
Landslides
Causes of landslides
Landslides
Causes of landslides
http://www.slideshare.net/surendra_slide/landslide-15656985
Landslides
Effects and losses due to Landslides
Landslides
Effects and losses due to Landslides
Landslides
Some of the major landslide in last one decade
Landslides
Some of the major landslide in last one decade
Uttarkashi
Landslides
Some of the major landslide in last one decade
South Korea
Avalanche
Avalanche
Avalanche
http://www.slideshare.net/georgedumitrache399/geography-year-9-avalanches
Avalanche
Avalanche
Avalanche
Everest climbers were killed due to avalanche in Nepal
Avalanche
Everest climbers were killed due to avalanche in Nepal
Man made disasters
Nuclear disaster , chemical disaster,
fire disaster, deforestation.
Terrorism, pollution
Man made disasters
Man made disasters
Reasons for man made disasters
Man made disasters
http://www.slideshare.net/Hareem_syed/man-made-disasters-29200696
Man made disasters
http://www.slideshare.net/Hareem_syed/man-made-disasters-29200696
Man made disasters
http://www.slideshare.net/Hareem_syed/man-made-disasters-29200696
Man made disasters
Bhopal Gas tragedy - On December 3, 1984 a chemical escaped from its tank (at least 27 tons). This
chemical was methyl isocyanate or also called MIC. It is very reactive and toxic.
Man made disasters
http://www.slideshare.net/Hareem_syed/man-made-disasters-29200696
Man made disasters
California
Man made disasters
Deforestation
http://www.slideshare.net/Hareem_syed/man-made-disasters-29200696
Man made disasters
http://www.slideshare.net/Hareem_syed/man-made-disasters-29200696
Man made disasters
Pollution
Man made disasters
Pollution
Man made disasters
Man made disasters
Man made disasters
Mumbai terror attack
Man made disasters
Paris terror attack
Man made disasters
California terror attack
Man made disasters
Pathankot terror attack
So we ….
