HYDROSPHERE-2.pptx

A hydrosphere is the total amount of water on a planet. The hydrosphere
includes water that is on the surface of the planet, underground, and in
the air.
A hydrosphere is the total amount of water on a planet. The hydrosphere
includes water that is on the surface of the planet, underground, and in
the air. A planet's hydrosphere can be liquid, vapour, or ice.
On Earth, liquid water exists on the surface in the form of oceans, lakes
and rivers. It also exists below ground—as groundwater, in wells
and aquifers. Water vapor is most visible as clouds and fog.
The frozen part of Earth's hydrosphere is made of ice: glaciers, ice caps
and icebergs. The frozen part of the hydrosphere has its own name,
the cryosphere.
Water moves through the hydrosphere in a cycle. Water collects in
clouds, then falls to Earth in the form of rain or snow. This water collects
in rivers, lakes and oceans.
Hydrosphere

Then it evaporates into the atmosphere to start the cycle all over
again. This is called the water cycle.
Water is a basic necessity of life. Since 2/3 of the Earth is covered
by water, the Earth is also called the blue planet and the watery
planet.The hydrosphere plays an important role in the existence of
the atmosphere in its present form. Oceans are important in this
regard.
Earth’s oceans contain 97% of the planet’s water, so just 3% is
fresh water, water with low concentrations of salts. Most fresh
water is trapped as ice in the vast glaciers and ice sheets of
Greenland. A storage location for water such as an ocean, glacier,
pond, or even the atmosphere is known as a reservoir. A water
molecule may pass through a reservoir very quickly or may remain
for much longer. The amount of time a molecule stays in a
reservoir is known as its residence time.

Tides are the periodic rise and fall of surface water
caused by the gravitational force of the moon and the
sun and by the rotation of the earth. As tides change,
large quantities of water move toward or away from
shore causing tidal currents.
Introduction of Tides

 Tides are formed by the gravitational pull of the moon and
to some extend by the pull of the sun, which is very far
from the earth.
 The moon though small is very close to the earth, it exerts a
strong gravitational pull on the earth.
 The earth’s water is very close to the moon and is pulled by
the gravitational force which is applied by the moon.
 The moon is directly overhead with the result of that the
water piles up to the water causing an ordinary high tide
there.
 There is piling of water on the other side of the earth.
Formation of Tides

• Tides move in a great wave around the
Earth by following the movement of the
moon.
• Tides always stripes the coast a interval
of 12 hrs 26 mins.
• Subsequently there is a fall in the water
for
about 6 hrs until it resets a low tide..
Pattern of the Tides

DIURNAL TIDE
Some areas, such as the Gulf of Mexico, have only one high and one low tide
each day. This is called a diurnal tide. An area has a diurnal tidal cycle if it
experiences one high and one low tide every lunar day.
SEMIDIURNAL TIDE
In general, most areas have two high tides and two low tides each day. When the
two highs and the two lows are about the same height, the pattern is called a
semi-daily or semidiurnal tide. Many areas on the eastern coast of North America
experience these tidal cycles.
Pattern of the Tides(cont.)
MIXED SEMIDIURNAL TIDE
An area has a mixed semidiurnal tidal cycle if it experiences two high and two
low tides of different size every lunar day. Many areas on the western coast of
North America experience these tidal cycles.

SPRING TIDES
When the sun and the moon are in line with each other, they pull the ocean’s
surface in the same direction. This causes higher high tides and lower low tides.
These tides are known as “spring tides”. These are of the greatest tidal range.
This occurs twice a month during full moon and new moon day.
NEAP TIDES
Seven days after a spring tide, the sun and moon are at right angles to each other.
When this happens, the bulge of the ocean caused by the sun partially cancels out
the bulge of the ocean caused by the moon. This produces moderate tides known
as neap tides, meaning that high tides are a little lower and low tides are a little
higher than average. Neap tides occur during the first and third quarter moon,
when the moon appears "half full."
Types of the Tides

INTRODUCTION
An ocean current is any more or less permanent or continuous
directed movement of ocean water that flows in one of the
Earth’s ocean.
The currents are generated from the forces acting upon the
water like the earth’s rotation, the wind, the temperature and
salinity differences and the gravitation of the moon.

An ocean current flows for great distances and together they
create the global conveyor belt, which plays a dominant role in
determining the climate of many earth’s regions. More
specifically, ocean current influence the temperature of the
regions through which they travel.

Circulation pattern
Gyres Surface water circulates in oceans in massive
circular patterns called gyres. The major surface currents
(eastern boundary, western boundary, and equatorial
current) in each ocean link to form a circle.
Gyres are clockwise in the northern hemisphere and
counter clock wise in the southern hemisphere.

The Currents of Atlantic ocean:
 The Gulf Stream is one of the strongest ocean currents.
It is 50-150km wide, 600m deep and has a velocity of 5km/h.
At 35oN, this current is deflected eastward s under the
combined effect of the Westerlies and the Coriolis force.
It reaches Europe as the North Atlantic Drift, flowing at a speed
of 15km/h, carrying warm Equatorial waters to the coast of
Europe. Part of the waters of this current flow southwards
along the Iberian coast as the cold Canaries Current.

 The cold Labrador Current flows between Greenland and the
Baffin Island to join the North Atlantic Drift at 50oN latitude.
 In the South Atlantic, the currents flow anticlockwise
to complete the circuit.

The Currents of Pacific ocean:
 The Kurioshio Current: The Counter Equatorial Current
flows in the opposite direction of the west flowing North
Equatorial Current. Its warm waters flow polewards as the
North Pacific Drift, keeping the Alaskan coast ice-free in
winter.
 The Oyashio Currents: The cold Alaskan or Bering Current
flows southwards and is joined by the cold Okhotsk current
and meets the warm Kuroshio or Japan Current as the cold
Oyoshio, off Hokkaido.
Kuroshio Current Oyashio Current
The Currents of Indian ocean:
 In the south Indian Ocean, the Equatorial Current turns south
off Malagasy as the Agulhas or Mozambique Current and merges
with the West Wind Drift.
 The north Indian Ocean shows a reversal of flow of the currents
in sync with the monsoon winds--- southwest and northwest
monsoons. During summer, when the southwest monsoon
predominates, the North Equatorial Current is replaced by an
easterly movement of water which gives off branches into the
Arabian Sea and the Bay of Bengal, producing clockwise circulation.
 In winter the North Equatorial Current flows westwards, south of Sri
Lanka. The northeast monsoons cause a general eastward and
northwards drift along the eastern shores of India and along the
Arabian coast.
During summer During winter

 Influence climate, by modifying the climatic conditiions of the coastal regions
along which they flow, e.g. the Gulf Drift.
 Winds blowing over warm currents pick moisture and bring rain while those
that pass over cold currents do not bring rain but make deserts colder and drier,
e.g. Kalahari Desert.
 Currents also influence routes of cyclonic streams.
 The dense fogs caused by the meeting of cold and warm currents are dangerous to
ships, e.g. in 1912, the Titanic struck on an iceberg due to poor visibility of the cold
Labrador Current and the warm Gulf Stream Drift.
 Ships can sail faster if they follow the direction of the current and the opposite
direction hinders speed.
 The mixing of cold and warm ocean currents causes plankton (fish food) to be found in
abundance.

HYDROSPHERE-2.pptx

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