It is about the oceans ,its features,divisions and its salinity

1. THE
OCEANS

2. • Water in earth came in liquid form came into existence in
Haedean Eon(4540-4000 mys, temperature was
extremely hot and earth was molten).
• Over times, both temperature and atmospheric pressure
dropped , and water continues to stay as liquid in the
oceans.
• The science of oceans is called oceanography.
• The international oceanographic research center is the
international Council for the Exploration of the Sea
headquarter Copenhagen.
• The older echo-sounding techniques have been replaced
by radar sounding and electrical echo devices to find the
precise depths of ocean floor and map the relief of the
oceans.
• Deep sea core samples are obtained by boring for the
study of the oceanic deposits- the various kinds of oozes,
muds and clays.
• For the observation and measurement of current flow,
various kinds of current meters using propelles , vanes or
pendulums have been designed.

4. Reservoir Volume (Million of
the total cubic km)
Percentage
Oceans 1370 97.25
Ice caps and glaciers 29 2.05
Groundwater 9.5 0.68
Lakes 0.125 0.01
Soil moisture 0.065 0.005
Atmosphere 0.013 0.001
Streams and rivers 0.0017 0.0001

5. PACIFIC INDIAN ATLANTIC
ANTARTICA ARCTIC
OCEANS
 Pacific
 Atlantic
 Indian
 Antarctica
 Arctic

6. OCEANIC DEEP /TRENCHES
•The trenches are the deepest parts of the oceans and they
are relatively steep- sided , narrow basins.
•They are 3 -5 km deeper than the surrounding ocean floor.
•They occur at the bases of continental slopes and island
arcs.
•Associated with active volcanoes and severe earthquakes
•As of now 57 deeps have been explored
o32 in the pacific oceans
o19 in Atlantic ocean
o6 in Indian ocean

7. MINOR RELIEF FEATURES
1. Mid oceanic ridges –
• Is composed of two chains of mountains divided by a large
depression. Ex- Iceland
2. Seamount
• Is volcanic in origin with pointed summits and rising from the
seafloor that does not reach the surface of the ocean. Examp-
the emperor seamount.
3. Submarine canyons
• The submarine canyons are deep valleys. Sometimes they
found cutting across the continental shelves and slopes often
extending from mouth of river. Examp- hudson canyons
4. Atoll
• Atolls are low islands found in the tropical oceans consisting of
coral reefs surrounding a central depression.

8. THE CONTINENTAL SHELF
THE CONTINENTAL SLOPE
THE DEEP SEA PLAIN
THE OCEANIC DEEPS
Ocean Floor Division

9. SALINITY OF OCEAN WATER
•Defined as the total content of dissolved salts in seawater.
•Expressed as parts per thousand or ppt.
•Salinity of 24.7 ppt is upper limit to demarcate “brackish
water”.
•Increases with depth and there is distant zone called the
halocline.
•High salinity sinks below the lower salinity water. This leads
to stratification by salinity .

10. FACTORS AFFECTING OCEAN SALINITY
•Mainly on salinity , temperature and density of water
•Other factors are:-
Evaporation and precipitation
The fresh water flow from river
Wind also influences
The ocean current

12. MOVEMENT OF OCEAN WATER
1. Waves – Oscillatory movements that results in the rise and fall
of water surface. The raised part-crest. The lowest part –
trough.
2. Tides- periodic rise and fall of sea level. Occurs only one or
twice the day and caused by the combined efforts of
gravitational forces , extended by the position of sun , moon
and the rotation of earth. When the tides are channeled
between islands or into bays and estuaries they are called
tidal currents.
3. Ocean currents-the ocean currents are the horizontal flow of
mass of water in a defined direction over great distances. The
direction is influenced by the rotation of earth. represent the
regular volume of water. There are two sources :Primary and
Secondary. Primary forces intitate the movement of water,
Secondary foces influence the current to flow.

13. TYPES OF OCEAN CURRENTS
Based on depth ocean currents are divided into :
•Surface currents- they consititute of 10 percent of total ocean and
are 400 m of ocean.
•Deep water currents- they make up of 90 percent of the total
ocean and water moves around the ocean basins due to variation
in density and gravity.
• For example- Heavy surface water of meditterian sea sinks and
flow westward past Gibraltar as a sub surface current.
Based on tempertaure ocean currents are:
•Cold currents-cold water ocean currents occur when the cold
water at the poles sinks and slowly moves towards equator as a
sub surface flow.
•Warm currents- water currents travel out from the equator along
the surface , flowing towards the poles to replace sinking cold
water.