Transcript Unit 4 The importance of oceans

Unit 4 The importance of oceans
Unit 4
The importance of oceans
Unit 4 The importance of oceans
Where are the major oceans and seas?
 361 million km² of the earth’s surface is covered
by water.
Unit 4 The importance of oceans
Where are the major oceans and seas?
Oceans and seas
occupy 71% of the
earth’s surface.
Oceans are
unevenly distributed
over the earth’s
surface. Most of the
southern
hemisphere is
covered by oceans.
The four oceans are
the Pacific, the
Atlantic, the Indian
and the Arctic.
Unit 4 The importance of oceans
Where are the major oceans and seas?
N

Arctic Ocean
North Sea
Sea of Okhotsk
Baltic Sea
Black Sea
Mediterranean Sea
Red Sea
Atlantic
Ocean
Yellow Sea
Caspian Sea
The Gulf
Arabian
Bay of
Sea
Bengal
Sea of Japan
East
China
Sea
South
China
Sea
°N
Hudson Bay
Gulf of Mexico
Pacific Ocean
°N
Caribbean Sea
°
Indian Ocean
°S
km
Unit 4 The importance of oceans
Pacific Ocean
Pacific Ocean is the largest and deepest of the world’s four
oceans, covering more than a third of the earth’s surface.
The size of the Pacific Ocean is 165 000 000km², which is
bounded on the east by the North and South American
continents; on the north by Bering Strait; on the west by
Asia; and on the south by Antarctica.
The average depth of the ocean is about 4 282 m and the
greatest depth is 11 033 m in the Mariana Trench.
Much of the plant and animal life of the Pacific Ocean is
concentrated along its margins.
Unit 4 The importance of oceans
Atlantic Ocean
Atlantic Ocean is the second largest of the earth’s four
oceans and the most heavily travelled.
The Atlantic Ocean has a surface area of 82 000 000 km².
The Atlantic Ocean is an “S-shaped” north-south channel,
extending from the Arctic Ocean in the north to the
Antarctic continent in the south. It is situated between the
western coast of the American continents and the eastern
coasts of Europe and Africa.
The Atlantic Ocean has an average depth of 3 926 m. The
greatest depth is 8 742 m in the Puerto Rico Trench.
Unit 4 The importance of oceans
Indian Ocean
Indian Ocean is the third largest of the earth’s four oceans,
bounded on the west by Africa, on the north by Asia, on the
east by Australia, and on the south by Antarctica.
The total area of the Indian Ocean is 73 400 000 km². The
average depth is 4 210 m and the deepest point is 7 725 m,
off the southern coast of the Indonesian island of Java.
The Indian Ocean contains numerous islands, the largest of
which are Madagascar and Sri Lanka.
Tropical storms occur occasionally and the ocean is notable
for seasonal winds called monsoons.
Unit 4 The importance of oceans
Arctic Ocean
Arctic Ocean is the smallest of the four world oceans. The
Arctic Ocean extends south from the North Pole to the
shores of Europe, Asia and North America.
The total surface area of the Arctic Ocean is 14 000 000
km². The average depth is 1 500 m and the deepest point in
the Arctic Ocean is 5 450 m in the Pole Abyssal Plain near
the North Pole.
Sea ice is formed by the freezing of seawater which is the
most extensive form of ice in the Arctic Ocean.
In winter a permanent cap of sea ice covers all of the ocean
surface.
Unit 4 The importance of oceans
Why are oceans important?
Recreation
Most of us are familiar with
our beaches and seas as these
are places for recreation.
We go there for
swimming in the hot
summer season. They are
also places for surfing,
sailing and fishing.
Unit 4 The importance of oceans
Why are oceans important?
Trade and shipping
Oceans have been used
for transporting raw
materials and
manufactured products.
Sea transport is the
cheapest way of
sending products in
large quantity over a
long distance.
Unit 4 The importance of oceans
Why are oceans important?
Trade and shipping
Shipping routes link up industrial and
densely populated regions in the world.
Oceans are important as over 70% of
world trade is carried out by ships.
Unit 4 The importance of oceans
Major sea routes of the world
N

Arctic Ocean
°N
North
America
Asia
Europe
Atlantic Ocean
°N
Africa
Pacific Ocean
South
America
Indian Ocean
°
°S
Australasia
km
Sea route
Unit 4 The importance of oceans
Why are oceans important?
Fish for food
Oceans are rich in
animal life. There are
20 000 species of fish
in the oceans.
Unit 4 The importance of oceans
Why are oceans important?
Fish for food
Fish is a major source
of food, today fish
supplies almost 20%
of the world’s animal
protein.
Unit 4 The importance of oceans
Why are oceans important?
Fish for food
Fish caught are used for the making of
animal feed, fertilizer, soaps and other
commercial products.
Millions of people depend upon fishing
for their livelihood.
Unit 4 The importance of oceans
Why are oceans important?
Minerals
Oceans are rich in minerals.
Tin, gold, platinum and diamonds
are found in the sand and gravel
along the shore.
Unit 4 The importance of oceans
Why are oceans important?
Minerals
Sea water is an important source of salt and fresh water.
Unit 4 The importance of oceans
Why are oceans important?
Energy
Continental shelves are gently sloping plains beneath the sea
bordering the continentals. They are no more than 100
fathoms (180m) deep.
Land
Sea level
100 Fathoms
Continental shelf
Unit 4 The importance of oceans
Why are oceans important?
Energy
Oceans are a potential source
of renewable energy.
Modern technology has made
the mining of oil in the deep
sea possible.
It is possible to make use of sea
waves and tidal currents for the
generation of electricity.
Unit 4 The importance of oceans
Why are oceans important?
Ocean-atmosphere system
Oceans act as a store house for the
heat energy coming from the sun.
The stored heat is then radiated back
to the atmosphere thus keeping the
atmosphere warm.
Unit 4 The importance of oceans
The ocean-atmosphere system
Sun
More solar
energy
Less solar
energy
Ocean
Colder water
Arctic circle
66 1/2°N
Surface
Warmer water
Equator
0°
Cold current
Warm current
Atmosphere
Colder water
Antarctic circle
66 1/2°S
Ocean absorbs sun’s energy
Ocean warms the atmosphere and supplies it with moisture
Warmer water flows to colder sea forming warm ocean current
Colder water flows to warmer sea forming cold ocean current
Unit 4 The importance of oceans
Why are oceans important?
Ocean-atmosphere system
 Our oceans supply the atmosphere with moisture and
heat.
 The heat absorbed by the ocean is released to the
atmosphere when air comes into contact with the ocean
surface.
 The air also absorbs from the ocean its moisture.
 When this wet air blows onshore from ocean to land, it
brings rain to coastal areas.
Unit 4 The importance of oceans
Why are oceans important?
Ocean currents and climate
Difference in temperature leads to the different density of
water over various parts of the ocean. The result is warmer
water moves from tropical areas to polar areas while colder
water moves from polar areas to tropical areas.
Ocean currents influence the temperature of the coastal
regions they flow past. A warm current raises the temperature
of the coast while a cold current lowers it.
The effect of the movement of ocean currents is important to
our climate as it reduces the extremes in temperature of both
the oceans and the atmosphere.
Unit 4 The importance of oceans
Ocean currents of the world
N

Arctic Ocean
°N
North
America
Asia
Europe
°N
Africa
South Equatorial
Current
Pacific Ocean
North
Equatorial
Current
Indian Ocean
East
Australasia
Australian
West Australian
Current
Current
West Wind Drift
Cold current
Warm current
km
Atlantic Ocean
South
America
Peruvian
Current
°S
Unit 4 The importance of oceans
On-shore wind from ocean brings rain
Condensation to form
clouds and rain
Clouds
The air absorbs from the ocean its
moisture. When this wet air
blows on-shore from ocean to
land, it brings rain to coastal areas.
Rain
Wind moves up the
slope and cools
Wet on-shore wind
Ocean
Unit 4 The importance of oceans
Why are oceans important?
Fog and typhoons
In Hong Kong fog occurs in spring when warm air passes
over the cold sea surface.
Pacific Ocean
Hong Kong
South
China
Sea
Warm tropical air
moves northwards
Fog
N

Unit 4 The importance of oceans
Why are oceans important?
Fog and typhoons
We receive a lot of rain in summer as winds blow in from
the ocean.
Condensation forms fog
South China Sea
Sea surface still cool in spring
Unit 4 The importance of oceans
Why are oceans important?
Fog and typhoons
Typhoons affecting us in the summer season obtain their
moisture and heat from the ocean.
The heat produces an enormous amount of energy which
makes these storms very destructive.
Hong Kong
N

Pacific Ocean
Tropical sea supplies
typhoons with heat
and moisture
Routes of
typhoons
Unit 4 The importance of oceans
Terms to learn
Continental shelf (大陸架) -- a gently sloping plain
beneath the sea bordering a continent. It is no more
than 100 fathoms (180m) deep.
Renewable energy (再生能源) -- energy that will
never be used up. Sea waves and tidal currents are
examples.