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Chapter 5 Our CHAnGinG EArtH

You may not believe it, but the earth also changes
constantly like any other living or non-living being
that exists on it. New mountains, lakes and rivers
are formed and old ones disappears. Sometimes
the changes are so fast that it moves at tremendous
speeds, covering or destroying whatever comes in its
path whereas sometimes the changes are so slow that
it is unnoticeable to the human eye.
lithosphEriC platEs The Earth’s Major Plates

The lithosphere is broken into a number of plates known as the Lithospheric plates. A
lithospheric plate is a massive, irregularly shaped piece of solid rock, generally composed
of both continental and oceanic lithosphere.

There are seven major and several minor lithospheric plates on the lithosphere.
Earth movEmEnts

On the basis of the forces, the earth movements are divided as under :
• Endogenic forces : These forces act in the interior of the earth and are known as
endogenic forces; e.g.— earthquakes and volcanoes.

• Exogenic forces : The forces, which work on the surface of the earth, are known as
exogenic forces e.g.— the erosional and depositional activities of wind, ice and river.
Earth Movements

Endogenic Forces Exogenic Forces

Erosional and Depositional
Sudden Forces Diostrophic Forces

River Wind Sea-waves Glaciers
Building mountains

Earthquakes Volcanoes Landslides
suddEn movEmEnts

Sudden movements in lithospheric plates bring abrupt changes on the earth’s surface. These
movements cause earthquakes, volcanoes and landslides. They cause extreme destruction
on the earth’s surface.

28 Social Studies-7