(i) National Institute of Oceanography (NIO) was established on 1st January 1966.
(ii) The headquarters of NIO is located at Dona paule, Goa.
(iii) It conducts research and observations to understand Oceanic features, Ocean engineering, Marine Archaeology etc.,

(a) Isobath - An imaginary line on a map joining the points of equal depths.
(b) Isohaline - An imaginary line on a map joining the points of equal salinity in oceans.

(a) Water table is a level below the ground, where water is found collected beneath the Earth's surface.
(b) Aquifers are porous rock strata filled with water, found below the earth's surface.

(i) One of the most indispensable natural resources on earth is water.
(ii) The Earth is also called the Blue planet, as it holds water in abundance.
(iii) Thus stands unique among all other planets

(i) The earth consists of four spheres
(ii) They are a) Lithosphere,
b) Atmosphere,
c) Hydrosphere and
d) Biosphere

(i) The degree of concentration of salts in the sea water is called salinity.
(ii) It is usually expressed in terms of parts per thousand (ppt or %0).
(iii) Salinity varies both horizontally and vertically.
(iv) The influence of temperature on ocean salinity depends upon the heating up of the surface water, which varies from tropics to polar regions

(i) Of all the movements of the oceans, sea waves are considered to be the strongest.
(ii) Sea waves are ripples on water caused when winds blow over the sea.
(iii) The height of these waves depends on the speed of wind, its duration and the direction from which they blow.
(iv) Sometimes waves are also caused by tremors felt on the ocean floor.
(v) Such waves are quite destructive and called Tsunami

The factors that generate ocean currents are:
(i) Earth's rotation
(ii) Prevailing winds and
(iii) Differences in temperature and salinity of ocean water

The ocean basins are characterised by the following major relief features:
(i) Continental shelf
(ii) Continental slope
(iii) Continental rise
(iv) Deep sea plain or Abyssal plain
(v) Oceanic deep
(vi) Oceanic ridge

Hydrosphere consists of water in various forms found on the earth. It is held on land as glaciers, ice caps, ground water, river, lakes and also as the water vapour in air.

a) Continental Rise
(i) At the base of the continental slope is a gently sloping layer of sediments which merge into the deep-sea floor.
(ii) This underwater feature found between continental slope and abyssal plains is called the continental rise.
(iii) It consists of submarine fans which are similar to the alluvial fans found on land.
b) Oceanic Ridge
(i) Oceanic ridge is a continuous submarine mountain chain.
(ii) They are made of young basaltic rock formed when two tectonic plates moves apart.
(iii) The mid-ocean ridge is probably the most extensive single feature of the earth's topography.
(iv) Two of the most well known mid- ocean ridges are the Mid-Atlantic Ridge and the East Pacific Ridge.
(v) The Mid-Atlantic Ridge is the largest unbroken oceanic ridge.

(i) Rain water is considered to be the purest form of water, as it contains very less proportion of salts when compared to the oceans and seas.
(ii) Hence it is called fresh water.
(iii) A major part of fresh water is found in the frozen state in the form of ice caps and glaciers.
(iv) Around 0.5 to 1% of it, is found in the liquid state as rivers, streams, lakes, ponds etc.
(v) Surface water may also penetrate through porous rocks and gets collected beneath the Earth's surface.
(vi) This is called groundwater