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IMPORTANT GEOPHYSICAL PHENOMENA(EARTHQUAKE,TS
UNAMI,VOLCANO,CYCLONES)
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 fro
m one decade to another.
Disasters can be classified into 1) Natural Disasters like Volcano,Tsunami Earthquake;l
andslides)
2)Human Made Disasters
3)Human Induced Disaster
EARTHQUAKE
 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.
 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:

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.
 The points at which earthquake originates called as FOCUS or
HYPOCENTRE,point on earth surface above this is called as EPICENTRE.
 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 a
ccepting 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 an
d are constantly moving like an objects sometime moving towards,away from each othe
r.
 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.
 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.
 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.
 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.
 HAZARDS OF EARTHQUAKE:

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.
 It may lead to the GROUND DISPLACEMENT along fault,which can seriously
damage that buildings.

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.
 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 oc
cur.Then what are the ways through which we can had least effect of that disaster.

In earthquake prone regions the buildings can be reinforced and designs to
prevent likelihood of collapse during an earthquake.
 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.thi
s 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 involve
s the movement of water from surface to seafloor which means it is directly related to de
pth of water bodies i.e deeper the ocean higher is the movement of water.as a result of t
his,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 up
ward,resulting into wave bunching up and becoming much more higher.Tsunami is a ser
ies of waves and first may not necessarily be largest.
Tsunami is a violent disturbances deep below the ocean surface causing unde
r water earthquake and subduction zones.
CAUSES OF TSUNAMI:
When an oceanic plates hits the continental plate,these plates press together and build th
e pressure.Eventually the heavier oceanic plate slips under the lighter continental plate a
nd 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 wat
er 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 en
ergy 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 fr
om 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 a
mount gas trapped within magma.large amount of water and carbon dioxides are dissolv
ed 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 mountai
n 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 so
lid 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 expl
osion so because of this many time eruptions also produce huge quantitiesof gas and dus
t.Magma sometimes rises under enormous pressure,so it not only finds cracks in earth cr
ust, it can also create them.When magma reaches earth surface it is called as LAVA.
TECTONIC PLATES AND VOLCANOS
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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 def
ormation,tsunami,air shocks,lightning,poisonous gas, glacial outburst flooding.Each vol
canic eruptions has a different consequences,although not all occur in all eruptions or in
associated with all volcanos.
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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
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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.T
o initiate a tropical cyclone the sea surface temperature needs to be around 26*C or abo
ve.However,existing cyclones often persist as they move over cooler water.
The development of tropical cyclones also realise on favourable broad scale regions a
nd can persist for several days with many following quite erratic paths.They lose their s
ource of energy when they move over land surface or colder oceans causing them to dis
sipate.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:
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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 someti
mes favourably impact on communities and enviroment.The most common impact is he
avy rainfall and strong winds that can lead to flooding.In some parts of world Australia t
ornados have been reported during cyclones.Storm surge or coastal inundation by sea
water,is also seen during cyclones.
SAFETY MEASURES:
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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
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www.ga.gov.au/hazards/earthquakes-basics/causes.html
http://crack.seismo.unr.edu/ftp/pub/louie/class/100/plate-tectonics.html
vulcan.wr.usgs.gov/Glossary/seismicity
www.geo.mtu.edu/UPSeis/hazards.html
www.sciencelearn.org.nz/Contexts/volcanos
http://m.businessdictionary.com/definition/cyclone.html
https://www.vocabulary.com/dictionary/cyclone
 https://sites.google.com/site/disasterportal/cyclone
 http://www.classle.net/.../cyclone safety