Page 140 - SST Class 06

Did you know that 71 percent of the earth’s crust on one or more sides. Plateaus can be formed by
is covered by water, which consists of all the big the erosion of surrounding areas by rivers,
oceans of the world? All these oceans are inter- flooding and glacier activity. An uplift of land
connected; therefore, the level of water remains can occur from the pressure of a large magma
the same. This remaining 29 percent forms the chamber under layers of rock. Repeated lava
land surface or continents. How many oceans do flows can also form a plateau over a period of
you know? What are their names? How many of time. The collision of tectonic plates of the
them touch the coastline of India? earth’s crust can elevate a portion of land to

We have seven major continents. They are Asia, create a plateau.
Europe, Africa, North America, South America,
Australia and Antarctica. The largest part of the
landmass lies in the northern hemisphere, which
is called the land hemisphere. Most of the south-
ern hemisphere is covered by oceans and seas.
Therefore, this hemisphere is called the water
hemisphere. Can you name the oceans and their
points of contact with the Asian continent?

Over these continents land may be found as
different landforms, namely mountains, plateaus
and plains. These landforms are distinguished
Plateau
according to their heights.
Mountains are the highest in elevation and some Plains are the lowest features and are flat and
of them have steep slopes and high peaks. Most level regions. Most plains have been formed by
of them are found in ranges or chains. The alluvial soil brought by rivers and they are very
Himalayas of India belong to this category. The fertile. The plain formed by the river Ganga in
Aols of Europe and the Rockies of North India is one such example.
America are other well-known examples.

Plains
Mountains
The different landforms we have studied support
A plateau is a portion of land that is more or less
different kinds of plants and animals. This greatly
flat and level, elevated above the surrounding
influences the livelihood of people.
area. It may have steep slopes or vertical cliffs

Social Science-6 140