- Hydrosphere is the name given ho the mass of water that covers about 71% of the Earth's surface.
- The average depth 4000 m. Of oceans is about your oceans largest Ocean is pacific ocean, Atlantic ocean, Indian ocean, and Artic ocean.
Ocean Floor :-
- It is very irregular as the surface of the Continents.
- Four major units of oceans floor are :-
Continental Shelf :-
- It is the coastal part of the ocean which is not very deep and the slope of the bottom is very gentle.
- Extends to a depth of 100 fathoms (1 fathom = 1.8 m ).
- In regions where the mountains extends along the cost, the shelf is narrower.
- About 20% petrol and gas found here. They also provide the richest fishing groiGr in the world. Marine life exits entirely here.
- They occupied about 7% of the total ocean area.
Continental Slope :-
- Extends seaward from the Continental Shelf. The continents blocks are supposed to end at the site of continental slope.
- The boundary between shelf and slope is known as Andesite line, named after and slope is known for Andesite line, named after the Andesite rock.
- Depth is up to 2000 fathoms.
- They cover about 8.5 % of the total ocean area.
Continental Rise :-
- At the foot of slope is found an area slightly Rising due to the accumulation of debris transported over the slope.
- Oil deposit occurs here.
Abyssal or the Deep Sea Plains :-
- It is the deepest and the most extensive part of the ocean floor and account for about 40% of the total ocean floor.
- Ridges are the raised areas in sea. E.g. Mid- Atlantic ridges ( S - shaped), Indian ocean ridges (inverted Y-shape).
- Parts of the abyssal plains are occupied by raised ridges or submarine mountains and by very deep trenches or canyons.
- A ridges rising more than 1000 m above the ocean floor is called Seamount. Flat topped Seamount are called Guyots (maximum In pacific ocean).
- Some parts of the ridges and form island (E.g. Hawaii Island).
Trenches :-
- Trenches are narrow and step sided depression. They occur where two plates of the Earth crust are moving together and one is being pushed down below and other. Deepest is Challenger Deep, a part of Mariana Trenches in the Pacific ocean, near Philippines, is more than 11033 m. deep. Submaromc canyons are the deep gorges on the ocean floor and are restrictited on the Continental shelves, slopes, and rise.
Salinity :-
- The proportion of dissolved salts to pure water is called Salinity. The average salinity in the oceans and sea is 35%, i.e. 35 grams of salt is one liter of water.
- Salinity is decrease order is ; Nacl, MgCl, CaSo4, KSO4, etc chlorine is most abundant element.
- Max salinity : Lake Van (Turkey) - 330%. Then Dead sea - 240%. Most saline sea is Res sea - 220%.
- The main source of salinity is dissolution of the rocks of oceanic crust, which contains salts.
- It is maximum at the tropics, because here temperature is high. Equatorial region come second because although they have high temperature, they have high rainfall also. Poles have minimum salinity because of additional of fresh water in the form of iceberg and excessive snowfall.
- It causes vertical circulation of water.
