There are various forms of disasters
from which every human being is aware. All disaster are quite enough to
threaten the humans or societies and had there impact on from one decade to
another.
Disasters
can be classified into 1) Natural Disasters like Volcano,Tsunami
Earthquake;landslides)
2)Human
Made Disasters
3)Human
Induced Disaster
EARTHQUAKE
l Earthquack is a violent shaking, rolling or
sudden shock on surface of earth'crust,sending out a series of shock waves in
all directions from its placeof origin which is called as EPICENTRE.
l Eathquake constitue one of the worst natural
disasters which often turn into disaster causing widespread destruction and
loss to human life or societies.
CAUSES
OF EARTHQUAKE:
l Earthquake are caused by sudden release of
energy in rocks.Tectonic plates which are present in the form of rocks are
moving very slowly.It is usually caused when underground rocks suddenly breaks
down or grind and scrap against each other along FAULT LINE.This lead to the
generation of seismic waves or called as earthquake waves,leads to the shaking
of earth surface.
l The points at which earthquake originates
called as FOCUS or HYPOCENTRE,point on earth surface above this is called as
EPICENTRE.
u
PLATE TECTONIC THEORY:
There are various theories which are
explaining the causes of earthquake,but the most satisfactory answer is given
by PLATE TECTONICS THEORY.This is the most accepting and one of scientific
theory which deals with the factors causing earthquake.
The
outer surface of earth is made up of tectonic plates which are about 100 km
thick and are constantly moving like an objects sometime moving towards,away
from each other.
u Earth release its internal heat by CONVECTIVE
MECHANISM,just like a pot of pudding boil on stove gas.Hot asthenospheric
mantle rises to the surface and spread laterally,transporting oceans and
continents as on slow conveyor belt and speed of this movement is very slow,a
few centimeters per years.
u Earthquake occur only in outer,brittle portions
of these plates,where temperature of rocks is very low.Deep in earth interior
convections of rocks caused by temperature variations in earth induces stresses
that results in movement of overlying plates.This stress from convection
release huge amount of heat which stress can deform the brittle portions of
overlying plates.If accumulating stress exceeds the strength of rocks
comprising these brittles zones,the rocks can break suddenly releasing the stored
elastic energy as an earthquake.
u There
are three types of plate boundaries which are called
Spreading,Convergent,or Transform,depending on whether the plates move away
from,toward,or laterally past one another respectively.Subduction occurs when
one plates converges toward another,move beneath it and plunges as much as
several hundred kilometres into earth interior.The JUAN DE FUCA PLATE off coast
of Washington and Oregon is subducting beneath North America.
u Most of the earthquake occurs on boundaries
between the plates,where one plate is forced under another such as it happens
off islands chains as of Japan,Indonesia or another one occurs in California
and New Zealand.
u
HAZARDS OF EARTHQUAKE:
u Earth
really pose direct danger to a person.the main and effective danger of
earthquake is EFFECT OF GROUND SHAKING.buildings can be damaged by shaking
itself or by ground beneath them settling to a different level than it was before earthquake.
u It may
lead to the GROUND DISPLACEMENT along fault,which can seriously damage that
buildings.
u FLOODING may occur due to break of dams
or levees along river.water from river would flooded the area,damaging the
buildings, may be away the people also.
u FIRE
can be started by broken gas lines and power line.
SAFETY
MEASURES FROM EARTHQUAKE:
We can
not stop earthquake from happening and we get warning as to when they will
occur.Then what are the ways through which we can had least effect of that
disaster.
u In earthquake prone regions the
buildings can be reinforced and designs to prevent likelihood of collapse
during an earthquake.
u The population can be educated about what to do
in event of earthquake and rescueplans can be drawan up in advance to minimize
the chaos when earthquake happen.
TSUNAMI
Tsunami
is a Japanese word which stand as tsu means harbour and nami means wave.this
phenomena related with earthquake or volcanis eruptions or landslides or
adjacents to oceans and results in sudden movement on water column.the passage
of tsunami involves the movement of water from surface to seafloor which means
it is directly related to depth of water bodies i.e deeper the ocean higher is
the movement of water.as a result of this,as wave approaches land and reaches
increasingly shallow water, it gets slow down. however the water column still
in deeper water is moving slightly faster and catches upward,resulting into
wave bunching up and becoming much more higher.Tsunami is a series of waves and
first may not necessarily be largest.
Tsunami is a violent
disturbances deep below the ocean surface causing under water earthquake and subduction zones.
CAUSES
OF TSUNAMI:
When
an oceanic plates hits the continental plate,these plates press together and
build the pressure.Eventually the heavier oceanic plate slips under the lighter
continental plate and causes earthquake which lifts up ocean and drops other
parts down,this happening on ocean floor is mirror on surface of water
above.The gravity acts fast to even out
of water surface.The seismic energy created that huge wave and it does not just
disappear.
Tsunami extends thousands of feet deep
into ocean which carries lot of water and energy so they can travel very far.
HAZARDS
OF TSUNAMI:
They
can directly causing the loss of humans and infrastructure.directle wasshing
away the properties,pets.
SAFETY
MEASURES:
Pack
some clothes,some food some cooking stuffs,flashlights,sleeping bags.Be ready
to get yourself,stuffs,family and animals out of house and on higher ground.
Listen tsunami warning carefully and take
it seriously.
VOLCANO
A
volcano is a kind of vent or chimney which transfer molten rocks called as
Magma from depth to earth surface.magma eruption from volcano known as lava, it
is a material which builds up the cone.
The explosiveness of volcano eruptions
depend on how easily magma can flow and amount gas trapped within magma.large
amount of water and carbon dioxides are dissolved in magma.as magma quickly
rises through earth crust gas bubbles form and expands upto 1000 times of their
original size.
TYPES
OF VOLCANO:
§
Shield
Volcano
§
Composite
Volcano
§
Caldera
Volcano.
The
form of volcano is determind by types and sizes of its eruptions which is controlled
by characterstics and composition of magma.
PLATE
TECTONIC THEORY:
Our
earth has three main layers the crust,the mantle,and the core.The crust is made
up of solid rocks and varies in their thickness which is more than 60 km thick
under mountain chains like Alps and Himalayas,but just 5 km under oceans.The
mantle is thick layers of molten rocks called as MAGMA and core is made up of
an outer liquid layer and a solid centre.
Temperature
present inside earth interior is very high about 5000 degree celsius in core
surrounded by a few kilometres of relatively cool,hard rocks called as crust.
A Volcano erupts when magma escapes from
inside the earth.As magma is escaping from a confined space,huge amount of
energy is release with it,as happens with any explosion so because of this many
time eruptions also produce huge quantitiesof gas and dust.Magma sometimes
rises under enormous pressure,so it not only finds cracks in earth crust, it
can also create them.When magma reaches earth surface it is called as LAVA.
TECTONIC
PLATES AND VOLCANOS
§
The
earth crust is its thinnest layers which is broken into various pieces
called as plates.These plates is above
the hot liquid magma.
§
Each
plate contains some continental crust and some oceanic crust.
§
Huge
currents of molten rocks circulates deep in mantle, causing plates to move
about very slowly on earth surface.
§
Many
of world volcanos occur along edges of boundaries of plates.
§
Plate
boundaries are among most active geologically active place on earth.Here new
rocks has been created and destroyed,so this is where the most important
volcanic activity occurs.
§
THE
PACIFIC RING OF FIRE:
§
More
than half of world volcanos are found in RING OF FIRE.This area forms a circle
stetching down the eastern side of Pacific ocean,from Alaska in North, through
Rocky mountains of Canada and USA,to Andes mountain of South America,it loops
back around the western side of Pacific,up through New Zealand,Indonesia and
Japan.
§
HAZARDS
OF VOLCANIC ERUPTION:
This
includes explosions,lava flows,bombs,mudflows,landslides,earthquakes,ground
deformation,tsunami,air shocks,lightning,poisonous gas, glacial outburst
flooding.Each volcanic eruptions has a different consequences,although not all
occur in all eruptions or in associated with all volcanos.
§
MEASUREMENT
OF VOLCANO:
This
is measued using a simple descriptive index called as VOLCANO EXPLOSIVITY INDEX
which ranges from zero to eight.this index includes volume of material ejected
with height of an eruption column and duration of eruptions.
CYCLONES
§
A
Cyclone can ve termed as atmospheric
system of low barometric pressure
accompanied by strongs winds that rotate counter-clockwise in northern
hemisphere and clockwise direction in
southern hemisphere.It
is known by its different name at different place such as cyclone in Indian
Ocean and Southern Pacific Ocean, called as hurricane in western Atlantic and
Eastern Pacific and typhoon in western Pacific.As generally we can called
cyclone as a violent rotating windstorm.
CAUSES
OF CYCLONES:
The
main source of energy for tropical cyclones is the warm ocean in tropical
regions.To initiate a tropical cyclone the sea surface temperature needs to be
around 26*C or above.However,existing cyclones often persist as they move over
cooler water.
The development of tropical cyclones also
realise on favourable broad scale regions and can persist for several days with
many following quite erratic paths.They lose their source of energy when they
move over land surface or colder oceans causing them to dissipate.Weakening may
also occur if cyclone moves into an unfavourable wind regions which disrupts
the structure of wind system.Sometimes a decaying tropical cyclone may interact
with weather system in higher latitudes to cause impact far from tropics.
FORMATION
OF CYCLONE:
§
Cyclone
can form only over warm ocean waters near equator.
§
To
form a cyclone,warm, moist air over ocean rises upward fromnear the surface.As
this air moves up and away from ocean surface,it leaves it less air near the
surface.
§
Air
from surrounding area with higher air pressure pushes into low pressure
area,then this new cool air become warm and moist and rises to and give birth to cyclones.
§
As
warmed moist air rises and cool the water in air forms clouds.The whole system
of clouds and winds spins and move,fed by ocean heat and water evaporating from
ocean surface.
§
As
storm system rotates faster and faster,an eye form in centre,which is calm and
clear with very low pressure.Higher pressure air from above flows down into the
eye.
§
IMPACT
OF CYCLONE:
Tropical
cyclonescan cause significant phenomena which can adversly affect,and sometimes
favourably impact on communities and enviroment.The most common impact is heavy
rainfall and strong winds that can lead to flooding.In some parts of world
Australia tornados have been reported during cyclones.Storm surge or coastal inundation by sea
water,is also seen during cyclones.
SAFETY
MEASURES:
§
Keep
watch on weather and listen to
radio,tv,newspapers.
§
Get
to know nearest cyclone shelter or safe house and safest route to reach their.
§
Do
not listen rumours.
§
Check
the roof and cover it with net or bamboo.
§
Chech
the walls,pillars doors,and windowsto see if they are secure.
NAME:DEEPTI
RAWAL
Posts
No comments:
Post a Comment