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Acid Rain : The name given to rain,
snow or sleet contaminated with
acid substances so that its acidity is greater than the
limit expected by
normal concentrations of carbondioxide dissolved in the rain
to give carbonic
acid. The increased acidity is caused by larger
concentrations of a number
of contaminants, particularly the strong acids, nitric and
sulphuric which
arise from industrial effluents containing oxides, nitrogen
and sulphur.
Alluvium : Sedimentary matter deposited by rivers. It makes
the soil fertile.
Antipodes : It is a region or place on the opposite side of
the earth.
Aphelion : The position of the earth or of any other planet
or comet in
its orbit when it is at its greatest distance from the sun.
Archipelago : A group of islands, such as Malaysian
Archipelago.
Asteroid : A limp of rock or metal in orbit around the sun.
Atoll : It is a coral reef of the shape of a horse-shoe or
ring with a lagoon
in the centre.
Biosphere : The organic life on earth both animate and
inanimate
including plants, vegetables, animals, birds and men.
Bore : A tidal wave which breaks in the estuaries of some
rivers and
being impelled by the narrowing channel rises in the form of
tide, and
courses along with great force and noise.
Chromosphere : A shell of hot gas about 1600-4800 km thick
encircling
the visible surface of the sun.
Comet : A body of gas and dust traveling in an elongated
orbit around the sun.
Cape : The point of termination or a neck of land extending
into the sea.
Confluence : Meeting place of two or more rivers as at Allahabad where
the Ganga, Yamuna and Saraswati meet.
Cosmis Rays : Atomic particles from spare whim travel close to
the speed of light.
Continental Shelf : Apart of land which is submerged under
the sea
and whose depth is not more than 600 ft.
Contours : Lines connecting parts of the same Altitudes above
sea level.
Date line (or International date line) : It is situated 180.
meridian from
Greenwich, a ship while crossing the line eastwards goes
forward a day,
while westward it goes back a day.
Delta : An alluvial deposit shaped like the Greek letter
formed at the
mouth of river. The Nile Delta is well-known.
Earthquake : It is shaking of earth's crust sometimes
accompanied by
permanent elevations or depression, but often no lasting
effect is visible on
the surface, except the damage done by shaking.
El Nino : A phenomenon noticed in the Pacific Ocean near
the Chilean Coast.
It is now believed that it has a major impact on the onset
of monsoon's in India.
Equinox : March 21 and September 23, when days and nights are
of
equal durations throughout the globe.
Fog : When moist air meets cold surface of earth, some of the
water
'ours condense on the particles of dust in air. This cloud
of condensed
vapour is called fog.
Glacier : A vast accumulation of ice and snow, which
moves slowly, till
it melts and forms a river is caned glacier.
Geyser : It is a fountain of hot water issuing from a hole
which extends
deep into earth's crust. The chief geysers of the world are
found in Iceland,
New Zealand and Yellow Stone National Park (USA).
Gulf Stream : It is a warm ocean current, which flows along
the eastern
coast of North America and drifts towards the western coast
of Europe.
Iceberg : A large mass of ice, detached from a glacier and
floating in the
sea, is called an iceberg.
Igloo : It is the dome-shaped hut of snow in which Eskimos
live,
Lagoon : A shallow lake formed at the :mouth of a river or
near the sea
but separated from it by a sand mound.
Meteor : A particle from space which burns up by friction in
the Earth's
atmosphere.
Midnight Sun : In the Arctic region, the sun is visible even
at midnight
in summer. Norway is called the land of midnight sun.
Milky way : A band of stars, gas and dust across the night
sky.
Ocean Currents : These are great circulatory movements of
ocean
either warm or cold and are caused by (i) permanent winds,
i.e., trade and westernly winds; and (ii) by difference in density of sea
water.
Oceans : 71% of the total area of the earth is covered by
water. In the
ancient times, these oceans were regarded as great hindrance
in the
development of relations between different countries. But
now these have
become great highways for transportation.
Orbit : The path of the earth or any other planet round the
sun is called its orbit.
Photosphere : The bright surface layer of gases on the sun.
Pampas : Dreary expanse of treeless grassy plains between the
Andes
and the Atlantic ocean.
Prairies : Extensive treeless tracts, covered with tall
coarse grass,
situated ill Central and North America.
Rainbow : It is an arch in the sky, caused by the reflection and refraction
of breaking up of the rays of the sun by tiny droplets of
rain
suspended in air.
Satellite : Natural satellites also called :moons are small
planets which
revolve round the larger ones.
Savannas : Land covered with natural grass in the tropical
region from
5° N and 5°C of equator to 23° N and 30° S.
Selvas : The plains covered with thick forests near the
river Amazon
(Brazil) in South America.
Tides : Tides are the alternate rise and fall of the sea
water. The tides are
caused by the gravitational pull of the moon and to a lesser
degree of the sun.
Volcano : It is large conical hillock having a funnel-shaped
opening from
which lava comes out. Cotapaxi is a lofty active volcano in
South America.
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