OCEANS AND SEAS FACTS

 Oceans and seas cover the about 70 percent of the earth's surface and account for about 97 percent of its total water. These Oceans and seas play a crucial role in regulating temperature variation and determining climate. Their waters absorbs heat from the Sun, especially in tropical regions, and the surface currents distribute it around the Earth, warming overlying air masses and neighboring 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 blowing over the oceans. All currents and deflected- to the right in the Northern Hemisphere, to the left in the Southern hemisphere- as a result of the Earths rotation. This deflective factor is known as the Coriolis force. A current that begins on the surface is immediately deflected. This current in turn generates a current in the layer of water beneath, which is also deflected. As the movement is transmitted downloads, 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 (Spring tides) occur at full and new Moon, the lowest tides (neap tides) occur at first and last quarter. 


In addition, the Ocean floor consist of two sections, 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 ocean. sloping quite gently to a depth of about 140 meters, the continental shelf s covered in sandy deposits shaped by waves and tidal currents. At the edge of the continental shelf, the sea bed slopes down to the abyssal plain, which lies at an average depth of about 3,800 meters. On this deep ocean floor is a layer of sediment made up of clays, fine oozes formed from the remains of tiny sea creatures, and occasional minerals-rich deposits. Echo- sounding and remote sensing from satellites has revealed that the abyssal plain is divided by a system of mountain ranges, far bigger than any on land- the mind ocean ridge. Here, magma well up from the Earth's interior and solidifies, widening the ocean floor. As the ocean floor spreads, valcones that have formed over hot spots in the crust move away from their magma source, they become extinct and are increasingly submerged and eroded. volcanoes eroded below sea level remain as seamounts. In warm waters, a volcano that projects above the ocean surface often acquires a fringing coral reef, which may develop into an atoll as the volcano become submerged. 

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