Page 191 - SST Class 08

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Disaster and its

Management

A disaster is a destructive event that occurs EARTHQUAKES
suddenly and involves loss of life and property. Sudden movements under the earth’s crust cause
It is a sudden accident or a natural catastrophe vibrations or shaking of a part of the earth’s
that causes great damage or loss of life. surface. These vibrations are known as earth-
TYPES OF DISASTERS quakes. The shaking movements sent out by an

Disasters can be of two types — natural and earthquake are called seismic waves. The study
man-made. of earthquakes is called seismology and the
Natural Disasters scientists who study earthquakes are called
seismologists.
Earthquakes, volcanic activity, tsunamis, floods,
cyclones, landslides, avalanches and droughts The place of origin of an earthquake is called its
are natural disasters and man has no control focus and the place which is directly above the
over them. They are a result of natural activities focus on the surface of the earth is called the
and hence known as natural disasters. epicenter. The effect of an earthquake is usually
felt the strongest near the epicenter.
Man-Made Disasters
The earth experiences about a million earth-
The man-made disasters are triggered by human
quakes every year. Most of them are minor
beings. Some of the man-made disasters are —
tremors and go unnoticed. The occurrence of an
bomb explosions, terrorism, war or civil war,
earthquake is detected by a sensitive instrument
leakage of poisonous chemicals, breach in dams,
called seismograph. The intensity of an earth-
air or water pollution, industrial accidents and
quake is measured with the help of an instrument
epidemics. They are known as man-made
known as the Richter Scale.
disasters because they occur due to human
actions and not natural forces. The Richter Scale, which ranges from zero to
nine, measures the total energy released during
an earthquake.
Natural Man-made
Disasters Disasters An increase in one point on the scale indicates
that the force of an earthquake is 10 times
greater than the previous number.
Meteorological Technological

Industrial
Tropgraphical
accidents
Security
Environmental
related

Social Science-8 191