Page 24 - sst_class_06

2. The aTlanTiC oCean :

The Atlantic Ocean is the second largest ocean. It is ‘S’ shaped. It is surrounded by North
America and South America in the west and Europe and Africa in the east.

3. The indian oCean :

It is the only ocean that has been named after our
country India. The shape of this ocean is almost The Atlantic ocean was named after the
triangular. In the north, it is bound by Asia, in the Atlas mountains in north-western Africa.
west by Africa and in the east by Australia.

4. The arCTiC oCean :

Most of the Arctic Ocean is permanently covered with
a vast floating raft of sea ice. Here temperatures are Some scientists place

very low, averaging -30°C in winter and sometimes frozen water-glaciers,
dropping to -70°C. It is located within the Arctic ice caps and icebergs
Circle and surrounds the North Pole. It is connected in its own sphere called
with the Pacific Ocean by narrow stretch of shallow the “cryosphere.”
water known as Berring Strait. It is bounded by
northern coasts of North America and Eurasia.

3. atmoSPhere

The Earth is surrounded by a layer of gases called
the atmosphere. The atmosphere has many gases like
nitrogen, oxygen, carbon dioxide and other gases. Every
gas has its specific role in the nature and is essential
for the existence of life. For example—nitrogen gas

is used by plants as a fertilizer, carbon dioxide gas is
used by plants for making food, oxygen is necessary for
breathing for all living things, etc.
Composition of Air

About 78% nitrogen, 21% oxygen and 1% other gases are present in the atmosphere.

The atmosphere extends up to a height of about 1600 km. The atmosphere is divided into
five layers based on composition, temperature and other properties.
1. Troposphere (sea level - 10 km) 2. Stratosphere (10 km - 50 km)

3. Mesosphere (50 km - 80 km) 4. Thermosphere (80 km - 500 km)

5. Exosphere (above 500 km)
Stratosphere contains ozone layer that is called ‘Blanket of the Earth’ because it absorbs

ultraviolet rays of the sun which are harmful to us. Green House Gases absorb sunheat during
daytime and release during night-time, so temperature of the earth does not fall too much at
night.

24 Social Studies-6