Geography 3 Marks Question

It is estimated that 71 percent of the total surface area of the earth is covered by water. Therefore, the earth has an abundant supply of water on its surface. Hence, the earth is called the ‘Blue Planet’.

Salinity is the term used to define the total content of dissolved salts in sea water. It is calculated as the amount of salt (in grams) dissolved in 1000 grams of sea water. Salinity of 24.7% has been considered as the upper limit to demarcate brackish water.

The continental margin is the zone of the ocean floor that separates the thin oceanic crust from thick continental crust and occupied by relatively shallow seas and gulfs.

Thermocline is a boundary region, from where there is a rapid decrease of temperature of the ocean water. About 90 percent of the total volume of water is found below the thermocline in the deep ocean. It is also the second layer of ocean water from surface to the bottom.

As many as 57 deeps have been explored so far; of which 32 are in the Pacific Ocean.
The Mariana Trench with maximum-known depth of 10,994m is the deepest part of the Pacific Ocean as well as world's oceans.

1. The Puerto Rico Trench has a maximum depth of 8,648 meters and is the deepest point in the Atlantic Ocean.
2. The maximum depth of the Sunda or the Java Trench in the Indian Ocean is 7,725 meters.
3. The deepest point in the Arctic Ocean is Litke Deep in the Eurasian Basin, at 5,450m.
4. The Southern Ocean's deepest point is in the South Sandwich Trench at 7,235 meters sea level.