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A glacial erosion process of scraping produced by the impact of rock debris. |
Abyssal plain | Large zone of relatively low-relief sea-floor. |
Acid Precipitation | Acidic rain, snow or fog resulting from high level of oxides of sulfur and nitrogen in the air. |
Advection | The horizontal movement of material in the atmosphere. |
Aerosols | Tiny solid or liquid particles suspended in the atmosphere. |
Aggradation | The combination of processes that builds up the surface through the deposition of material that was removed from elsewhere through degradation. |
Alluvial fan | A fan-shaped deposit consisting of alluvial material located where a mountain stream emerges onto a plain; primarily a desert land-form. |
Alluvium | Sediment laid down by a stream on its valley floor; deposition occurs when the steam velocity decreases and the valley fills with a veneer of unconsolidated material. Since, soil particles washed from slopes in the drainage basin form a large part of these deposits, alluvial soils are usually fertile and productive. |
Antarctic Circle | The latitude 66.5 degree south marking the northern boundary of southern hemisphere portion of earth’s surface that receives a 24 hour period of sunlight at least once each year. |
Antarctic Ice Sheet | The continental glacier that covers almost all of Antarctica, enabling the study of what conditions were like elsewhere in the world during much of the late Cenozoic Ice Age. |
Anticline | An arc-like upfold with the limbs dipping away from its axis. |
Archipelago | A group of islands, often elongated tnto a chain. |
Arctic Circle | The latitude (66.5 degree north) marking the southern boundary of the Northern hemisphere portion of earth’s surface that receives a 24 hour sunlight at least once a year. |
AGN | Active Galactic Nucleus. The massive black hole in the core of an active galaxy. |
Active Galaxy | A galaxy with a central black hole which gives radiation. |
Antimatter | Matter composed of the antiparticles ot those that form normal matter. |
Aphelion | The farthest distance from the Sun in the elliptical orbit of a planet, comet or an asteroid. |
Apogee | The point in the orbit of a satellite at which it is farthest from Earth. |
Arc-minute | A unit of angular measure equal to 1/6 of a degree. The sun and the moon are 30 arc-minutes across. |
Arc-second | A unit of angular measure equal to 1/60 of an arc-minute. Jupiter measures 44 arc-seconds in respect of its width. |
Asteroid | Also called minor planet. It is a body which circles around the sun between the orbits of Mars and Jupiter. There are about 10 thousands of Asteroids. |
AU | Astronomical Unit. It is the mean difference between the Earth and the Sun. An AU is equal to 150 million Kilometer. |
Atmosphere | A layer of gases attached to a planet due to its gravity. |
Aurora | Beautiful lights seen in the northern and the southern skies. |
Axis | The imaginary line through the center of a planet, Sun or Galaxy around which it rotates. |
Ash (volcanic) | Solid cinder like lava fragments, smaller than volcanic bombs, that are exploded into the air during an eruption; most fall to the ground around the erupting volcano. |
B
Bay | A broad indentation into a coastline. |
Biome | The broadest justifiable subdivision of the plant and animal world, as assemblage and association of plants and animals that forms a regional ecological unit of Sub-continent dimensions. |
Breccia | In elastic sedimentary rocks when pebbles-sized fragments in a conglomerate are not rounded but angular and jagged. |
Biosphere | The zone of terrestrial life, habitat of all living things, and the part of soil layer below that hosts living organisms. |
Big-Bang | The event marked by a large explosion 13.7 billion years ago, which resulted in the birth of the Universe. |
Binary Star | Two Stars linked by mutual gravity and revolving around common center of gravity. |
Black Hole | A collapsed celestial body which is so dense that no light or radiation can escape it. |
Blue Giant |
A very big hot and luminous blue star. |
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Cadera | A steep walled, circular volcanic basin usually formed by the collapse of a volcano whose magma chamber emptied out; Can aslo result from a particularly powerful eruption that blows off the peak and crater of a volcano. |
Cartography | The science, art and technology of map making and map use |
Cenozoic | The era of the recent life on the geological time scale extending from 66 million years ago to the present. this period is subdivided into Tertiary and Quaternary period. |
Chinook | Name given to Foehn Winds that affect the leeward areas of mountains zones in the western plateaus of North America. |
Cinder Cone | Volcanic land-form consisting mainly of pyroclastics; often formed during brief periods of explosives activity, they normally remain quite small. |
Circum-Pacific Earthquake Belt | An aspect of the specific ring of fire, the lengthy belt of subduction zones that girdles the pacific basin; here occur the heaviest concentration of earthquake epicenters as well as active volcanoes on the world map. |
Cirque | An amphitheater-like basin, high up on a mountain, that is source area of a mountain glacier. |
Celestial Equator | An imaginary line encircling the sky midway between the celestial poles. |
Comet | A small celestial body compressed of ice and dust that orbits the Sun. |
Constellation | The recognized pattern of stars which divide the sky into sections e.g., Virgo, Sagittarius, etc. |
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Disc Galaxy | A galaxy with a flattened circular disc of stars. |
Dwarf Star | A star with less than average size. |
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Eclipse | The phenomenon when one celestial body passes in front of another. |
Ecliptic | The path of the Sun around a celestial sphere. It is equivalent to Earth’s orbital plane. |
Equator | Imaginary line which lies half way between the two poles of a celestial body. |
Escape Velocity | The minimum velocity which an object requires to leave the surface of planet for entering the space. |
Equinox | The moment when the Sun appears to stand directly above a planet’s equator. |
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