Important Hydrosphere Notes
The earth is called the blue planet. More than 71 percent of the earth is covered with water and 29 percent is with land. Hydrosphere consists of water in all its forms. As running water in oceans and rivers and in lakes, ice in glaciers, underground water and the water vapour in atmosphere, all comprise the hydrosphere.
Hydrography is the science that measures and describes the physical features of the navigable portion of the Earth’s surface and adjoining coastal areas.
OCEAN
An ocean is a body of saline water that composes much of a planet’s hydrosphere.On Earth, an ocean is one of the major conventional divisions of the World Ocean. These are, in descending order by area, the Pacific, Atlantic, Indian, Southern (Antarctic), and Arctic Oceans.
MAJOR OCEANS
| Oceans | Salient Features |
| Pacific Ocean |
The Pacific Ocean is by far the world’s largest ocean at 55,557,000 sq km.It covers 28% of the Earth and is equal in size to nearly all of the land area on the Earth. The Pacific Ocean is located between the Southern Ocean, Asia, and Australia in the Western Hemisphere. It has an average depth of 13,215 feet (4,028 meters) but its deepest point is the Challenger Deep within the Mariana Trench near Japan. This area is also the deepest point in the world at -35,840 feet (-10,924 meters).
|
| Atlantic Ocean |
The Atlantic Ocean is the second largest of the world’s oceans, with an area of about 106,460,000 square kilometers. It covers approximately 20 percent of the Earth’s surface and about 29 percent of its water surface area.
|
| Indian Ocean |
The Indian Ocean is the only ocean named after a country, that is, India. The shape of ocean is almost triangular. In the north, it is bound by Asia, in the west by Africa and in the east by Australia.
|
| Southern Ocean |
The Southern Ocean, also known as the Antarctic Ocean or the Austral Ocean, comprises the southernmost waters of the World Ocean, generally taken to be south of 60° S latitude and encircling Antarctica.
|
| Arctic Ocean |
The Arctic Ocean is located within the Arctic Circle
and surrounds the North Pole. It is connected with the Pacific Ocean by a narrow stretch of shallow water known as Berring strait. It is bound by northern coasts of North America and Eurasia. |
OCEAN TRENCHES
Ocean trenches are steep depressions in the deepest parts of the ocean [where old ocean crust from one tectonic plate is pushed beneath another plate, raising mountains, causing earthquakes, and forming volcanoes on the seafloor and on land.
OCEANIC RIDGES
A mid-ocean ridge or mid-oceanic ridge is an underwater mountain range, formed by plate tectonics. This uplifting of the ocean floor occurs when convection currents rise in the mantle beneath the oceanic crust and create magma where two tectonic plates meet at a divergent boundary.
SEAMOUNT
A seamount is a mountain rising from the ocean seafloor that does not reach to the water’s surface, and thus is not an island, islet or cliff-rock.
SUBMARINE CANYONS
Submarine canyon is steep-sided, V-shaped valley that is formed at outer edge of continental shelf and continue across the slope. Meanwhile at its lower end usually leads
to an abyssal fan (submarine fan), a fan-shaped, big pile of sediment lying on the sea floor.
IMPORTANT OCEANIC CURRENTS
| Ocean | Current | Type |
|---|---|---|
| Atlantic Ocean - Northern hemisphere | North Equatorial Current | Warm Current |
| Antilles Current | Warm Current | |
| Florida Current | Warm Current | |
| Gulf Stream | Warm Current | |
| Artic Ocean | Labrador Current | Cold Current |
| East Greenland Current | Cold Current | |
| Atlantic Ocean | North Atlantic Drift | Warm Current |
| Norwegian Current | Warm Current | |
| Canaries Current | Cold Current | |
| Atlantic Ocean: Southern Hemisphere | South Equatorial Current | Warm Current |
| Falkland Current | Cold Current | |
| Brazil Current | Warm Current | |
| South Atlantic Current | Cold Current | |
| Benguela Current | Cold Current |
| Ocean | Current | Type |
|---|---|---|
| Atlantic Ocean - Northern hemisphere | North Equatorial Current | Warm Current |
| Antilles Current | Warm Current | |
| Florida Current | Warm Current | |
| Gulf Stream | Warm Current | |
| Artic Ocean | Labrador Current | Cold Current |
| East Greenland Current | Cold Current | |
| Atlantic Ocean | North Atlantic Drift | Warm Current |
| Norwegian Current | Warm Current | |
| Canaries Current | Cold Current | |
| Atlantic Ocean: Southern Hemisphere | South Equatorial Current | Warm Current |
| Falkland Current | Cold Current | |
| Brazil Current | Warm Current | |
| South Atlantic Current | Cold Current | |
| Benguela Current | Cold Current |
| Ocean | Current | Type |
|---|---|---|
| Indian Ocean Northern Hemisphere during winter | North East Monsoon Drift | Warm Current |
| Summer | South West Monsoon Drift | Warm Current |
| Indian Ocean: Southern Hemisphere | Mozambique Current | Warm Current |
| Agulhas Current | Warm Current | |
| West Australian Current | Cold Current | |
| Equatorial Counter Current | Warm Current | |
| South Equatorial Current | Warm Current | |
| West Wind Drift | Cold Current |
CORAL REEFS
Coral reefs are important marine ecosystems that are found in clear, shallow, tropical waters around the world. They provide habitat for diverse communities of plants and animals. Coral reefs exists where necessary environmental factors prevail. Major reefs are found around Caribbean and indo-pacific regions. The largest among them is the great Barrier Reef located off the east coast of Australia.
Coral Bleaching occurs when poor water quality kills coral, leaving behind a colourless skeleton.
SALINITY LEVELS
courtesy: Salinity Level Chart – Wikipedia
The oceanic salinity not only affects the marine organisms and plant community but it also affects the physical properties of the oceans such as temperature, density, pressure, waves and currents etc. The freezing point of ocean water also depends on salinity e.g., more saline water freezes slowly in comparison to less saline water.
WORLD GEOGRAPHY COMPLETE NOTES