Download GEOGRAPHY OCEAN The oceans and seas occupy about 71 per

GEOGRAPHY
OCEAN
The oceans and seas occupy about 71 per cent of the total earth surface which means
that about 29 percent of the earth’s surface is occupied by the land. The study of the oceans.
The water in the oceans, the movement of water and the economic significance of the ocean is
called oceanography. The ocean basins of the world are large depressions on the earth’s
surface which are filled by a great mass of salt water.
1.
2.
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4.
5.
TYPES OF OCEANS
There are four major types of oceans in the world and the rest constitution the seas
Pacific ocean which occupies 165 mill km2
Atlantic ocean which occupies 82 mill km2
Indian ocean which occupies 74 mill km2
Arctic ocean which occupies 14 mill km2
The seas which occupies 25 mill km2
Economics Importance of Oceans to Man
1.
Means of transportation
2.
Provision of food
3.
Provision of employment
4.
Tourism
5.
Development of seaports
6.
Promotion of economic activities
7.
Extraction of salts
8.
Sources of minerals
9.
Provision of industrial products
10.
Educational research
11.
Influence climate adjoining the coastlands
12.
Source of sea weeds
Relief of the ocean floor
1.
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Continental Shelf
These are areas of shallow water which surround the continent. The continental shelves
are wider in some areas of the world such as the edges of the Arctic ocean.
It is a continuation into the sea of the coastal plain
It forms a gentle sloping flat form extending from the sea level to an average depth of
about 200m
It is of varying widths which contain shallow water
It forms 7% of the total area of the ocean
It is found in Labrador
Importance of Continental Shelf
1.
It is a good fishing ground
2.
Development of natural harbour
3.
Facilitates exploration of petroleum
4.
they are tourist centres
2.
Continental Slope
Is the continuation of continental shelf into the ocean floor
Characteristics
The continental slope links the continental shelf with the deep sea plain or ocean
floor
It is narrow and deep
-
It drops in depth to about 400 metres
3.
Ocean Ridge
The ocean ridges take the form of either a ridge on a plateau
Characteristics
1.
Ocean ridge takes the form of either a ridge or a plateau
2.
It rises up from the deep sea plain
3.
Some rise above the surface to form oceanic islands
4.
Deep Sea Plain
These are wide, gently undulating or fairly level surfaces which have a depth of between
2000m and 3000m
Characteristics
This is a wide gently, undulating or fairly level surface
It has a depth of between 2000m and 2000m
2
It occupies
of the ocean floor
3
It is also called the Abyssal plain
OCEAN DEEP
These are very deep trenches in the floor of the ocean
Characteristics
These are the long, narrow trenches that plung as great ocean deeps
They are of about 9000 metres in depth Manana trench
Materials, mainly deposited on the ocean floor include
i. oozes
ii. Clay
iii. Muds
DIAGRAM
Diagram should be provided by the teacher
Salinity of the Ocean
Salinity is defined as the degree of saltiness or concentration of salt solution in oceans
and seas.
The degree of salinity varies from ocean to ocean and it is measured in percentage or
per thousand.
Factors Affecting Salinity of Ocean
The salinity of ocean is determined by the following factors.
1.
The amount of fresh water added to the ocean. Fresh water is derives from rain, rivers,
streams and melting ice. The more the volume of water added to the ocean, the lower
the degree of saltiness and vice versa.
2.
The degree of water mixing with ocean currents: within the enclosed water bodies such
as the red sea the salinity is very high because of the absence of ocean current mixing
with it. Whereas in seas that are not enclosed the degree of their mixing with ocean
current is very high therefore there is reduction in salinity.
3.
The rate of evaporation: The higher the rate of evaporation the higher the salinity of the
ocean and vice versa. In tropics the higher the rate of evaporation in the ocean water
the higher the salinity whereas in the arctic the lower the evaporation of the ocean water
the lower the salinity.
Ocean currents
Ocean currents simply refer to the regular movement of large masses of surface water
from one part of ocean to another.
Types of Ocean Current
Ocean currents can be grouped into two main types
1.
Warm ocean currents
2.
Cold ocean currents
1.
Warm Ocean Currents: are those that flow from the equatorial regions towards the
poles with a relatively high surface temperature
2.
Cold Ocean Currents: are those current that flow from the poles towards the equatorial
region with a relatively low temperature
Causes of Ocean Currents
1.
2.
3.
4.
5.
The rotation of the earth
Planetary winds
The temperature differences
Salinity
The slope of the landmass
Effects of Ocean Currents on Adjacent Coastlands
1.
Ocean currents modify the climate of an area by raising the temperature when cold and
warm
2.
The various warm currents of the ocean bring regular rainfall to their coastland
3.
Cold currents bring about coastal fogs instead of actual rain and this is responsible for
poor visibility which passes danger to sailors on the high sea and aeroplane.
4.
Cold currents bring about reduction in temperature through the formation of coastal fogs
5.
Cold currents and aridity of the landmass which they blow across
6.
In polar regions, warm currents enhance ports to be free from ice
7.
The meeting of warm and cold currents encourages the formation of plankton which is
an essential food for fish
Distribution of Ocean Currents according to their Hemisphere
1.
Northern hemisphere
1.
The main warm ocean currents are
(a)
Atlantic ocean
Cayen current
Florida current
Culf stream current
North Atlantic Drift
(Guinea current)
Pacific Ocean
-
Kuroshio current
Oyashio – Bering current
North pacific drift
The main cold ocean current are:
2.
(a)
Atlantic Ocean
Labrador current
Irminger current
Canaries current
(b)
Pacific Ocean
California current
Okhotsk current
Southern Hemisphere
i.
The main warm ocean currents are:
Atlantic ocean
-
Braziham current
-
South Atlantic Drift
Pacific Ocean
-
East Australian Current
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South Pacific Drift
Indian Ocean
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Mozambique current
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South Indian Ocean Drift
The Main Cold Ocean Current
Atlantic Ocean
-
Benguella current
-
Falkland current
Indian Ocean
- West Australian current
Pacific Ocean
- Peruvian current