OCEANS AND SEAS COVER ABOUT 70 PER CENT of the Earth”s surface and around for about 97 per cent of its total water. These oceans and seas plays a crucial role in regulating temperature variations and determining climate. WATER ABSORB HEAT FROM THE SUN Their waters absorb heat from the sun,especially in tropical regions, and the surface currents distribute it around the Earth,warming overlying air masses and neighbouring land in winter and cooling them in summer. The oceans are never still.Differences in temperature and salinity drive deep current systems,while surface currents are generated by winds blowings over the oceans. All currents are deflected to the right in the Northern hemisphere, to the left in Souther Hemisphere-as a result of earth Rotation. CONSTANT EBB AND FLOW OF TIDES A current that begins on the surface is immediately deflected.This current in turn generates a currents in the layer of water beneath,which is also deflected.As the movement is transmitted downwards,the deflections form an Ekman spiral.The waters of the oceans and seas are also moved by the constant ebb and flow of tides.These are caused by the gravitational pull of the moon and sun.The highest tides occur at full and new Moon the lowest tides occur at first and last quarter. THE OCEANS FLOOR COMPRISES TWO SEACTIONS The continental shelf and slope,and the deep ocean floor.the continental shelf and slope are part of the continental crust,but may extend far into the oceans. sloping quite gently to a depth of about 140 metres,the continental shelf is covered in sandy deposits shaped by waves and tidal currents.