|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
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.
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.