Answer the
following questions.
(i) What is
precipitation?
(ii) What is water
cycle?
(iii) What are the
factors affecting the height of the waves?
(iv) Which factors
affect the movement of ocean water?
(v) What are tides and
how are they caused?
(vi) What are ocean
currents?
Answer the following questions.
(i) What is precipitation?
(ii) What is water cycle?
(iii) What are the factors affecting the height of the waves?
(iv) Which factors affect the movement of ocean water?
(v) What are tides and how are they caused?
(vi) What are ocean currents?
(i)
Sun’s heat causes water to evaporate. When the water vapour
rises, it begins cooling. The condensing water vapour forms droplets
of water. Masses of such water droplets form clouds and float in air.
When these droplets become too heavy to float in air, they fall upon
land or sea in the form of rain, snow or sleet. This is known as
precipitation.
(ii)
The water present on the Earth’s surface (on land and in water
bodies) gets evaporated by the Sun’s heat. The water vapours
rise, condense and form clouds. When the clouds become heavy, the
condensed water vapours fall back upon land or sea in the form of
rain, snow or sleet. The processes of evaporation, condensation and
precipitation continue in a cyclical manner. This way, water
continually changes its form and circulates between oceans,
atmosphere and land. This continuous circulation of water is known as
the water cycle.
(iii)
Waves are formed when winds scrape across the ocean surface. Winds
blowing at very high speed form huge waves. An earthquake, a volcanic
eruption and underwater landslides also affect the height of waves.
Such phenomena can shift large amounts of ocean water, thereby
causing huge waves to be formed.
(iv)
The movements that occur in oceans are broadly categorised as waves,
tides and currents.
The
factors affecting these movements of ocean water are as follows:
(a)
Waves are formed as a result of winds,
earthquakes,
volcanic
eruptions
and underwater landslides.
(b)
Tides are caused by the strong
gravitational pull exerted by the Sun and the Moon
on the Earth’s surface.
(c)
Another factor affecting the movement of ocean water is temperature.
Ocean currents are formed because of the temperature differences
between the ocean water present at different latitudes.
(v)
Tides are the rhythmic rise and fall of ocean water twice in a day. A
high tide occurs when ocean water covers much of the shore by rising
to its highest level. When ocean water falls to its lowest level and
recedes from the shore, it is referred to as a low tide. Tides are
caused by the strong gravitational pull exerted by the Sun and the
Moon on the Earth’s surface.
Formation
of high and low tides:
The
water of the Earth closer to the Moon gets pulled under the influence
of Moon’s gravitational force, thereby causing a
rise of ocean water towards the Moon. At the same time, the ocean
water at the opposite side of the Earth bulges away from the moon.
These bulges (or rises in the height of ocean water) are called high
tides. When ocean water falls back, low tides occur. Say, point I
is a point on Earth that faces the Moon and point IV
is at the opposite end of the Earth. Under the gravitational pull of
the Moon, the ocean water at point I
moves towards the pulling force. At the same time, the ocean water at
point IV
moves away from the pulling force. Both these movements are high
tides as the ocean water rises to its highest level at both these
points. Due to the Earth’s rotation on its axis and the Moon’s
revolution in its orbit, after a certain time period, the ocean water
at both points I
and IV
recedes to its lowest level, thereby causing low tides. When the moon
is directly above point IV,
the entire process is repeated, with points I
and IV
first experiencing high tides, and then, low tides. Hence, in a day,
both points I
and IV
experience two high tides and two low tides.
Formation
of spring and neap tides:
When
the Sun, the Moon and the Earth are in the same line, the combined
gravitational pulls of both the Sun and the
Moon cause the highest high tides, i.e., high tides are the highest.
These tides are called spring tides.
When
the gravitational pull of the Moon on the Earth is perpendicular to
the gravitational pull of the Sun on the Earth, the gravitational
forces counteract, thereby causing the formation of the lowest low
tides, i.e., low tides are the lowest. These tides are called neap
tides.
(vi)
Ocean currents are streams of water flowing constantly on the ocean
surface in definite directions. Ocean currents are formed because of
the temperature differences between the ocean water present at
different latitudes. The further one travels from the Equator, the
colder the ocean water generally becomes. Due to convection, the warm
currents that originate near the Equator move towards the Poles. The
cold currents carry ocean water from the Polar or higher latitudes to
the tropical or lower latitudes.
(i) Sun’s heat causes water to evaporate. When the water vapour rises, it begins cooling. The condensing water vapour forms droplets of water. Masses of such water droplets form clouds and float in air. When these droplets become too heavy to float in air, they fall upon land or sea in the form of rain, snow or sleet. This is known as precipitation.
(ii) The water present on the Earth’s surface (on land and in water bodies) gets evaporated by the Sun’s heat. The water vapours rise, condense and form clouds. When the clouds become heavy, the condensed water vapours fall back upon land or sea in the form of rain, snow or sleet. The processes of evaporation, condensation and precipitation continue in a cyclical manner. This way, water continually changes its form and circulates between oceans, atmosphere and land. This continuous circulation of water is known as the water cycle.
(iii) Waves are formed when winds scrape across the ocean surface. Winds blowing at very high speed form huge waves. An earthquake, a volcanic eruption and underwater landslides also affect the height of waves. Such phenomena can shift large amounts of ocean water, thereby causing huge waves to be formed.
(iv) The movements that occur in oceans are broadly categorised as waves, tides and currents.
The factors affecting these movements of ocean water are as follows:
(a) Waves are formed as a result of winds, earthquakes, volcanic eruptions and underwater landslides.
(b) Tides are caused by the strong gravitational pull exerted by the Sun and the Moon on the Earth’s surface.
(c) Another factor affecting the movement of ocean water is temperature. Ocean currents are formed because of the temperature differences between the ocean water present at different latitudes.
(v) Tides are the rhythmic rise and fall of ocean water twice in a day. A high tide occurs when ocean water covers much of the shore by rising to its highest level. When ocean water falls to its lowest level and recedes from the shore, it is referred to as a low tide. Tides are caused by the strong gravitational pull exerted by the Sun and the Moon on the Earth’s surface.
Formation of high and low tides:
The water of the Earth closer to the Moon gets pulled under the influence of Moon’s gravitational force, thereby causing a rise of ocean water towards the Moon. At the same time, the ocean water at the opposite side of the Earth bulges away from the moon. These bulges (or rises in the height of ocean water) are called high tides. When ocean water falls back, low tides occur. Say, point I is a point on Earth that faces the Moon and point IV is at the opposite end of the Earth. Under the gravitational pull of the Moon, the ocean water at point I moves towards the pulling force. At the same time, the ocean water at point IV moves away from the pulling force. Both these movements are high tides as the ocean water rises to its highest level at both these points. Due to the Earth’s rotation on its axis and the Moon’s revolution in its orbit, after a certain time period, the ocean water at both points I and IV recedes to its lowest level, thereby causing low tides. When the moon is directly above point IV, the entire process is repeated, with points I and IV first experiencing high tides, and then, low tides. Hence, in a day, both points I and IV experience two high tides and two low tides.
Formation of spring and neap tides:
When the Sun, the Moon and the Earth are in the same line, the combined gravitational pulls of both the Sun and the Moon cause the highest high tides, i.e., high tides are the highest. These tides are called spring tides.
When the gravitational pull of the Moon on the Earth is perpendicular to the gravitational pull of the Sun on the Earth, the gravitational forces counteract, thereby causing the formation of the lowest low tides, i.e., low tides are the lowest. These tides are called neap tides.
(vi) Ocean currents are streams of water flowing constantly on the ocean surface in definite directions. Ocean currents are formed because of the temperature differences between the ocean water present at different latitudes. The further one travels from the Equator, the colder the ocean water generally becomes. Due to convection, the warm currents that originate near the Equator move towards the Poles. The cold currents carry ocean water from the Polar or higher latitudes to the tropical or lower latitudes.
