Page 156 - SST Class 06

kind of environment—in mountains and deserts, weather and churn a kaleidoscope of life.
on plains and near seashores. Humans depend on these teeming waters for

Lakes vary greatly in size. Some measure only a comfort and survival, but global warming and
few square meters and are small enough to fit in overfishing threaten earth’s largest habitat.
your backyard. Such small lakes are often Geographers divide the ocean into five major
referred to as ponds. Other lakes are so big that basins— the Pacific , Atlantic , Indian, Arctic and
they are called seas. The Caspian Sea, in Europe Southern. Smaller ocean regions such as the
and Asia, is the world’s largest lake, with an area Mediterranean Sea, Gulf of Mexico and the Bay
of more than 370,000 square kilometers of Bengal are called seas, gulfs and bays. Inland
(143,000 square miles). bodies of saltwater such as the Caspian Sea and
OCEANS the Great Salt Lake are distinct from the world’s
The ocean is a continuous body of salt water that oceans.
covers more than 70 percent of the earth’s The four main oceans and their size and striking
surface. Ocean currents govern the world’s features are given below :

Ocean Area (sq. km.) Striking Features
The Pacific Ocean 1,66,000,000 Ringed by numerous volcanoes known as ring of fire.
The Atlantic Ocean 82,000,000 Mid-Atlantic Ridge, a chain of mountains in the ocean
runs its entire length.
The Indian Ocean 73,600,000 Mid-oceanic ridge extends from Asia to Antarctica, several
peaks form Islands.
The Arctic Ocean 14,000,000 Landlocked but connected to Pacific Ocean by Bering
Strait and to Atlantic Ocean by Greenland Sea and Davis
Strait.

Southern Ocean or Antarctic Ocean south of slope together with continental Shelf and the rise
50°S it is sometimes regarded as the fifth ocean that separates it from dry land is known as
of the world. The ocean receives waters from the Continental Margin.
Atlantic, Pacific and Indian Oceans. OCEAN-LAND RELIEF FEATURES
Oceans make two kinds of relief features – in The Ocean water is always on the move. This
relation to landmass of the continents and under movement of ocean water together with rivers
water relief. The under-water relief is called falling into oceans and winds shape many
Submarine Relief. Under the water of the ocean landforms on the sea coasts. Chief among these
there are mountains, plateaus, deep trenches or are delta, estuary, cliff and beaches. A delta is
cracks in ocean floors and plain surfaces. The formed near the mouth of a river where the sea is
Mariana Trench in the Pacific Ocean floors relatively calm. The rivers deposit their fine
(about 11,033 meters deep) is the deepest place sediments for a long distance. The ocean cur-
in the world. The edges of the continents pene- rents or tide generally do not disturb these
trate deep into ocean water. This submerged part deposits. The sea water raised by tides at the
of the continents is called Continental Shelf. The mouth of the river, shape the triangular landmass
steep slope that separates the continent from the called delta. The Ganga-Brahmaputra delta is the
ocean floor is known as Continental Slope. This largest in the world. In case the river’s current

Social Science-6 156