Water Bodies

The continuous interchange of water between the oceans, atmosphere and land is called Hydrological cycle or Water cycle. It connects all the three realms of the earth: lithosphere, hydrosphere and atmosphere.

The differential heating of the earth by the sun causes water to evaporate. The atmospheric blanket around the earth does not allow water vapour to escape. When the water vapour comes in contact with the cooler layers of atmosphere, it condenses to form clouds and falls back on the earth in the form of rain, snow or hail. This water flows into rivers or goes underground or back into the oceans. This circulation of water in different forms is called water cycle.

Two characteristic features of the Atlantic Ocean are:

1. It is the second largest ocean of the world.
2. It is the saltiest major ocean.

Oceans are of great importance to man directly or indirectly. Following are the importance of ocean:

1. Source of water — Ocean is the major source of water to mankind through water cycle.
2. Climate — Oceans affect the climate of the places near them by maintaining their temperature, humidity, rain etc.
3. Food Resources — The oceans provide fish and other marine food and thus are an important food resource.
4. Mineral and chemical resource — They have a variety of dissolved salts like sodium chloride, magnesium chloride, potassium chloride etc.
5. Ocean and oil — A large part of world's oil and gas production comes from off shore fields.
6. Ocean and energy — They help to generate tidal energy. Countries like France, UK, USA are generating energy from tides.
7. Trade and transport — Oceans provide the cheapest mode of transportation for international trade. They are very useful for transportation of bulky products like coal, iron, machinery etc.

A Marginal sea is a division of an ocean, partially enclosed by islands, archipelagos or peninsulas, adjacent to the open ocean at the surface, or bounded by the submarine ridges on the sea floor. Two Marginal seas are:

1. Bering Sea
2. Arabian Sea

Two causes of pollution of water bodies are:

1. Urbanisation — Rapid urbanisation in India during the recent decades has given rise to a number of environmental problems such as water supply, waste water generation and its collection, treatment and disposal. For example, pollution in major rivers.
2. Oil spills — Waste oil from city drains, tankers and leakage from oil wells cause the oil to seep into the sea and pollute water. Massive oil spills at sea by huge oil tankers severely pollute the oceans.

The oceans account for 71% of the earth.

The Pacific Ocean has a string of volcanoes along the coastal margins of the continents.

Arctic Ocean remains perpetually frozen.

The salt concentration in Dead Sea is around 250 parts per thousand.

Lakes are larger and deeper than ponds.

Southern Ocean is not navigable because it remains frozen for the most part of the year.

Atlantic ocean is bounded by North and South Americas in the west and Africa and Europe in the east. It connects two of the most developed regions of the world, North America and Europe. Most of the world's great ports lie on its coast. This makes it a great commercial highway.

Bering Sea

India

Egypt

Indian Ocean

North Sea

Mauritius island

Lake Titicaca

estuary

deltas

Sea level

Bering Strait

watershed

Arctic Ocean

Atlantic Ocean