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WATER (OCEANS) 101 Table 12.1 : Components and Processes Southern ocean and the Arctic. The various of the Water Cycle seas, bays, gulfs and other inlets are parts of Components Processes these four large oceans. A major portion of the ocean floor is found Water storage Evaporation between 3-6 km below the sea level. The ‘land’ in oceans Evapotranspiration under the waters of the oceans, that is, the Sublimation ocean floor exhibits complex and varied Water in the Condensation atmosphere Precipitation features as those observed over the land (Figure 12.2). The floors of the oceans are Water storage in Snowmelt runoff rugged with the world’s largest mountain ice and snow to streams ranges,deepesttrenchesandthelargestplains. Surface runoff Stream flow freshwater These features are formed, like those of the storage infiltration continents, by the factors of tectonic, volcanic Groundwater storage Groundwater and depositional processes. discharge springs Divisions of the Ocean Floors atmosphere, landsurface and subsurface and the organisms. The ocean floors can be divided into four major divisions: (i) the Continental Shelf; (ii) About 91 per cent of the planetary water is the Continental Slope; (iii) the Deep Sea Plain; found in the oceans. The remaining is held as (iv) the Oceanic Deeps. Besides, these divisions freshwater in glaciers and icecaps, groundwater sources, lakes, soil moisture, there are also major and minor relief features in the ocean floors like ridges, hills, sea atmosphere, streams and within life. Nearly mounts, guyots, trenches, canyons, etc. 59 per cent of the water that falls on land returns to the atmosphere through Continental Shelf evaporation from over the oceans as well as The continental shelf is the extended margin from other places. The remainder runs-off on of each continent occupied by relatively the surface, infiltrates into the ground or a partshallow seas and gulfs. It is the shallowest of it becomes glacier. part of the ocean showing an average gradient It is to be noted that the renewable water of 1° or even less. The shelf typically ends at on the earth is constant while the demand is a very steep slope, called the shelf break. increasing tremendously. This leads to water The width of the continental shelves vary crisis in different parts of the world — spatially from one ocean to another. The average width and temporally. The pollution of river waters of continental shelves is about 80 km. The has further aggravated the crisis. How can shelves are almost absent or very narrow along you intervene in improving the water quality and augmenting the available quantity of some of the margins like the coasts of Chile, thewestcoastofSumatra,etc.Onthecontrary, water? the Siberian shelf in the Arctic Ocean, the largest in the world, stretches to 1,500 km in R ELIEF OF THE O CEAN F LOOR width. The depth of the shelves also varies. It The oceans are confined to the great may be as shallow as 30 m in some areas depressions of the earth’s outer layer. In this while in some areas it is as deep as 600 m. section, we shall see the nature of the ocean The continental shelves are covered with basins of the earth and their topography. The variable thicknesses of sediments brought oceans, unlike the continents, merge so down by rivers, glaciers, wind, from the land naturally into one another that it is hard to and distributed by waves and currents. demarcatethem.Thegeographershavedivided Massive sedimentary deposits received over a the oceanic part of the earth into five oceans, long time by the continental shelves, become namely the Pacific, the Atlantic, the Indian, the source of fossil fuels. Reprint 2026-27