Competitive Exams: Ocean Science

The oceans cover 70.8 percent of the Earth's total surface area and hold 1.5 × 106 cubic kill of. Water. This water despite its abundance is not directly useful to human beings as it is not potable. The ocean water contain about 3.5 percent of dissolved salts, chlorine, sodium, magnesium, sulphur, calcium, potassium, bromine, strontium; and boron. A few quantities of carbon, silicon, aluminium, flourine and iodine are also found. The oceanic waters are always in motion owing to a variety of natural forces. The oceans, unlike the continents merge so naturally into one another that it is hard to separate them. The geographers have divided the oceanic area into four oceans namely:

  1. The Pacific

  2. The Atlantic

  3. The Indian

  4. The Arctic These oceans include the seas, bays, gulfs and other ocean inlets attached to them, The oceans have an average depth of 3.5 km but their depth varies from place-to-place. The deepest known point is the Challenger Deep, a part of the Mariana Trench in the Pacific Ocean, which is 12 km deep. The ocean floor consists of three main zones, i.e.. the continental shelf the continental slope and the abyss. The

Pacific Ocean

It is the largest and the oldest of the oceans. It occupies about 35 percent of the earth's area. It is 17 km at broadest and 11.5 km at the deepest. It has the greatest conglomeration of islands which fall into three broad groups viz.

  1. Micronesia

  2. Melanesia

  3. Polynesia.

The Atlantic Ocean

It is the second largest ocean covers 21 percent of the earth's area. Its greatest deep is 8.3 km (Milwankee Deep)

The Indian Ocean

It is the third largest ocean stretches from Cape Comorin in Indian to the Antarctic at the south poie. It takes up 14.6 percent of the Earth's total surface area. It greatest depth is 7.7 km (Planet Deep).

The Arctic Ocean

It is assumed as glaciers but not as an ocean. It is not navigable. It winds round the North Pole and is completely frozen in winter and covered with drifting ice from the rest of the year. It has separate existence and its area of over J. 3 × 106 square km is said to b~ called an ocean. Although we have only four oceans, there are seven oceans.