Dictionary of Physical Geography

Catastrophism: Sudden and quick radical changes in the physical and biological components of the biosphere is called Catastrophism.
Climate: The generalization of weather-related conditions during a long period (31years) of any place or region is called climate OR long-term average (31 years) of weather in an area is called climate.
Denudation chronology: The historical sequence of denudation (weathering and erosion) in any region is called denudation chronology. Reconstruction of the erosional history of the earth’s surface.
Denudational Processes: Processes that create, affect, and modify landforms through weathering, erosion and deposition are collectively called the processes of denudation or denudation processes.
Life layer: The circle that maintains the existence of living beings around the earth is called life layer. This life layer extends into the atmosphere, hydrosphere, and lithosphere to the extent that the elements necessary for the survival of living beings become accessible.
Meteorology: The science that studies the physical conditions of the lower atmosphere is called meteorology.
Weather: The short-term variations of atmospheric conditions, such as temperature, air pressure, wind circulation, humidity, rainfall, visibility etc. in a particular place within a certain time, is called weather. It varies from one place to another and from one time to another. Thus, the state of atmosphere at a specific place and time is called weather.
Aerology: The science that studies the atmosphere above surface layer is called aerology or it is the study of air.
Biogeography: The science that studies the biosphere is called biogeography. It includes the study of physical environment, soil, animals, and plants and related ecosystems.
Binary hypothesis: The concept of the origin of the planets and the earth by the combination of two stars is called binary hypothesis.
Cambrian period: This is a geological period of the Paleozoic Era, stretching from 600 to 500 million years ago. This period is named after the place of Cambria in Wales, United Kingdom.
Carboniferous period: This is a geological period of the Paleozoic Era, which began 350 million years ago and ended 270 million years ago. It is named after the predominance of carbon in the sedimentary deposits of that period.
Cretaceous period: This is a geologic period of the Mesozoic Era, stretching from 135 to 70 million years before present. This period is named after the predominance of chalk in the deposits of that period. The word Cretaceous is derived from the Latin word ‘Creta’ which means chalk.
Devonian period: This is a geological period of the Palaeozoic Era, stretching from 400 to 350 million years before present. This period is named after the place and region of Devonshire in the United Kingdom.
Dualistic concept: The concept of origin of planets including earth with the help of two or more stars is called dualistic concept. For example: Tidal hypothesis of James Jeans.
Eocene period: This is a geological period of the Cenozoic Era, stretching from 70 to 40 million years before present. This period is named after ‘Eos’, which means ‘day break’.
Filament: A group of cigar-shaped substances is called a filament. The meaning of filament here is from the substances that released from the Sun.
Holocene period: It is the most recent geological period of the Neozoic Era, stretching from 10 thousand years ago to present day. This period has seen the development of agriculture and domestication of plants and animals.
Inner planets: The four small-sized planets near the Sun are called inner planets. They include planets Mercury, Venus, Earth, and Mars respectively.
Jurassic period: This is a geological period of the Mesozoic Era, stretching from 180 to 135 million years before present. This period named after the Jura Mountains of Switzerland.
Miocene period: This is a geological period of the Cenozoic Era stretching from 25 to 11 million years before present. This period is named after the German word ‘Meion’, which means small.
Law of conservation of angular momentum: According to this law, the gross angular momentum of an isolated system remains constant.
Monistic concept: In the context of the origin of planets and the earth, the concept of their origin from a single star is known as monistic concept. For example- Nebula hypothesis of Kant (1753 A.D.).
Nebula: The body of gas and dust emitted from the stars in the universe is called nebula OR diffuse cloud of dust and gases.
Oligocene: This is the geological period of the Cenozoic Era; stretching from 40 to 25 million years before the present.
Ordovician period: This is a geological period of the Palaeozoic Era, which lasted from 500 to 440 million years before the present. The period is named after a tribe called the Ardovisus of North Wales, United Kingdom.
Outer planets: The large 4 planets (Jupiter, Saturn, Uranus, Neptune) located in the outer part of the solar system are called outer planets.
Permian period: This is a geological period of the Paleozoic Era, stretching from 270 to 225 million years before the present. It is named after the Perm province of former Soviet Russia.
Planetesimals: Chamberlin gave the name planetesimals to the numerous small particles ejected from the surface of the Sun by the gravitational force of a star approaching the Sun.
Pleistocene period: It is a geological period of the Neozoic Era, stretching from 1 million to 10 thousand years before the present.
Pliocene period: This was the last geological period of the Cenozoic Era, stretching from 11 to 1 million years before the present. It is named after the German word ‘Pleion’ which means greater.
Silurian period: This is a geological period of the Palaeozoic Era, which lasted from 440 to 400 million years before the present. The period is named after a British tribe called the ‘Silutars’ of southern Wales.
Triassic period: There is a geological period of the Mesozoic Era, stretching from 225 to 180 million years before the present. This period is named after the three-layered (threefold) deposits in Germany.
Asthenosphere: A zone below the lithosphere from 80 to 200 kilometres in which the rocks are comparatively less rigid than the upper and lower parts. Seismic velocities are significantly lower in the asthenosphere than in the upper and lower parts of the Earth’s interior. Therefore, the material in this zone is soft and subject to plastic flow.
Core: The inner part of the earth below 2900 km. is known as the earth’s core.
Crust: The part of the earth up to a depth of 30 km (maximum 100 km) below the Earth’s surface is called the crust.
Epicenter: The place on the earth’s surface lies directly above the focus of an earthquake.
Focus: The place from where an earthquake starts below the earth’s surface is called Focus.
Gutenberg discontinuity: The boundary between the lower mantle and the outer core (at a depth of 2900 km) is called the Gutenberg discontinuity. Below that there is a sudden change in density (from 5.0 to 10.0). There is also a sudden increase in P-wave velocity (13.6 km per second). This discontinuity is also called the Weichert discontinuity.
Inner core: The innermost part from 5150 to 6371 km (up to the centre) below the surface of the earth is called the inner core. It is in a solid state and its density is 13.6 and the speed of the P wave is 11.23 km per second.
Mainshock: The tremor that comes after the primary and secondary tremors is called the main tremor. It is of long duration.
Mantle: The inner part of the earth between the Crust and the Core with a thickness of 2900 km is called the mantle. This layer has two parts,
(1) The upper mantle (the part up to a depth of 700 km from the lower limit of the crust. The separating boundary of the crust and the upper mantle is called Moho-discontinuity. It is named after A. Mohorovicic who floored this discontinuity.
(2) The part from 700 to 2900 km is called the lower mantle. It has an average density of 3.3 g/cm3 and 68 per cent of Earth’s mass. dd>
Nife: Suess has named the innermost layer of the earth as Nife (Nickel + Ferrum) based on its mineralogical composition. The presence of iron in this layer suggests that the earth’s core has magnetic power.
Outer Core: The inner part of the earth between 2900 to 5150 km (lower mantle and inner core) is called the outer core. ‘S’ seismic waves cannot pass through the mantle, which proves that the outer core is in a liquid state.
Primary waves: Primary or longitudinal waves are those seismic waves which are like a sound waves and the movement of particles (molecules) is in the direction of the line of the wave. These are also called compressional waves. They move with the highest speed in both solid and liquid parts.
Secondary waves / Transverse waves: Transverse or secondary seismic waves are like water waves or light waves in which the movement of particles (molecules) is at right angles to the direction of the wave. In short, these are called S waves. They usually disappear in the liquid.
Seismology: Seismology is the science in which seismic waves are studied by marking them with a seismograph OR the scientific study and interpretation of earthquakes known as seismology.
Sial: Edward Suess called the earth’s crust (upper layer) as Sial because of the predominance of silica (silica-Si) and aluminium(aluminium-Al).
Sima: Edward Suess has named the second layer of the earth located below Sial as Seema (Si+Ma) because of the predominance of silica and magnesium.
Surface waves: These waves usually affect only the upper part of the earth. They are highly effective although they have the lowest speed. They are denoted by the letter L.
Weichert discontinuity: The dividing boundary of the lower mantle and outermost (core) is called Gutenberg discontinuity or Weichert discontinuity. It occurs at a depth of 2900 km below the Earth’s surface. There is a sudden increase in density at this boundary. The density of the lower mantle increases from 5.5 to 10 due to which there is a sudden increase in the speed of seismic waves (13.6 km per second).
Zone of low velocity: In the upper mantle (100 to 700 km), the speed of seismic waves slows down (7.8 km per second), due to which this part is called the low-velocity zone.
Antipodal situation: The position of land opposite to water and the position of water opposite to land is called an antipodal situation.
Constructive plate boundary: Boundaries, where two plates move apart, are called constructive plate boundaries or divergent plate boundaries. At an oceanic ridge where two plates are moving apart; magma flows up and outward and new crust is formed. Therefore, these boundaries are known as constructive boundaries.
Conservative plate boundary: The boundary where plates move parallel to the margin is called the conservative boundary. The San Andreas Fault in California is an example of a conservative boundary where the pacific plate to the west of the fault moves northwards to the south-moving North American Plate on the continental side.
Destructive plate boundary: The zone where two plates move towards each other and the oceanic crust is being destroyed by subduction is called a destructive plate boundary.
Eugeosyncline: A geosyncline situated seaward from the continent and characterized by heavy deposits of volcanic material and sediments deposited by turbidity currents.
Isochrone: Line joining places of an equal journey time to the same location is called Isochrone.
Land hemisphere: Because of the abundance of land parts, the northern hemisphere is called the land hemisphere.
Palaeomagnetism: The study of the magnetic properties (residues) preserved in the rocks formed in different geological periods of the earth is called paleomagnetism. It includes the study of changes in the position of poles and magnetic pole reversal in the geological past.
Plate: The broad part or segment of the lithosphere that floats on the asthenosphere and moves independently of other plates is called a plate.
Plate tectonics: The study of the nature of different plates of the earth, their dynamics and all the tectonic activities related to them is called plate tectonics.
Sea-floor spreading: The spreading of the ocean floor or formation of the new lithosphere on both sides of mid-oceanic ridges is called sea-floor spreading. All this happens along constructive plate boundaries where two plates move apart from each other and magma flows up and outward.
Sphere: A sphere is a geometric figure whose volume is greater than its surface area.
Tetrahedron: A tetrahedron is a geometric figure with four faces whose volume is the minimum relative to its surface area.
Geo isostasy: The condition of physical or mechanical stability between the upstanding parts (mountains, plateaus, plains etc.) and low-lying basins (lakes, oceans etc.) on a rotating earth is known as geo isostasy.
Iceberg: A large mass of floating ice in the sea water is called an iceberg.
Level of compensation: The plane below the surface of the earth, on which all the uplifted parts (mountain, plateau, plains etc.) have equal mass. Different parts of the crust have different densities above the level of compensation. According to Archdeacon Pratt, the bigger the column, the lesser the density and the smaller the column, the greater the density. For example, mountains have a lower density than Plateaus and Plains.
Bedding plane: The connecting plane between two consecutive layers (beds) of sedimentary rocks is called the bedding plane.
Breccia: The mixture of small and large particles of volcanic materials after deposition is called breccia or agglomerate.
Butte: Small size mesa is called Buti. It is formed when the mesa get eroded from all sides.
Carbonaceous rocks (Carbon-dominated rocks): Sedimentary rocks containing organic elements formed by the accumulation and consolidation of remains of vegetation are called carbonaceous rocks, e.g., Coal.
Calcareous rock: The calcareous sedimentary rock formed by the accumulation and consolidation of the skeletons of calcareous marine animals and remains of vegetation is called calcareous rock, e.g., Limestone, Dolomite, Kharia, chalk etc.
Contact metamorphism: When the rock comes in contact with hot and liquid magma is metamorphosed due to extreme heat is called contact or thermal metamorphism, e.g., a transformation of limestone rock into marble.
Cuesta: Asymmetrical ridges formed by the erosion of the steep side of the rock with dipping beds are called cuesta and have a steep slope on one side and a gentle slope on the other
Dyke: When the magma solidified perpendicular to the beds of sedimentary rocks within the earth’s surface, then the resultant wall-like formation is called a dyke.
Dynamic metamorphism: When sedimentary rocks are altered over a wide area due to intense pressure and heat it is called dynamic metamorphism. This type of metamorphosis takes place during mountain building.
Foliation: The parallel arrangement of particles (crystals or grains) in the form of layers in metamorphic rocks is called foliation. Foliation is found in metamorphic rocks like slate and gneiss.
Glacial drift: Mixed materials containing boulders, pebbles, sand particles, clay etc. transported by glaciers are called glacial drifts.
Glassy basalt: The basalt igneous rock without grains or with very fine grains is called glassy basalt, e.g., Obsidian, Pitchstone, Pumice and Perlite.
Ground moraines: The moraines deposited in the beds of glaciers are called ground moraines.
Hogback: The long, thin and steep sloped ranges or ridges with hard rocks formed after erosion are called hogbacks. It should be remembered that both the dip and the slope of Hogback are vertical while the dip and slope of Questa are inclined.
Igneous rock: The rock formed by the cooling and solidification of hot and liquid magma and lava is called igneous rock. The word igneous is derived from the Latin word ‘ignis’, which means fire.
Lacolith: A laccolith is a form of intrusive hypabyssal igneous rock with a dome-shaped or convex summit and planar base and formed due to the cooling and solidification of magma along horizontally bedded planes of the sedimentary rocks. When lava erupts, the upper part of the stratified sedimentary rocks is transformed into a convex arch or a dome shape structure by the force of ascending gases. Then, the space forms between the upper convex arc and the lower horizontal layers is filled with magma and volcanic ash, gas, lava, etc. As a result of this laccolith form.
Lapilli: Pea-size rock fragments of volcanic materials are called lapilli.
Lateral moraines: An accumulation of till deposited along the side margins of a glacier are called lateral moraines.
Lava flow: When magma erupts from a volcano and flows slowly in the form of lava on the earth’s surface, then such a flow is called a lava flow.
Lithosphere: The rigid part of the earth’s crust, which includes the oceanic crust, continental crust, and part of the mantle above the asthenosphere is called the lithosphere.
Lopolith: The word Lopolith has been derived from the German word ‘lopas’, which means a shallow basin. When the magma solidified in a concave shape shallow basin inside the earth, then the resultant form of igneous rocks is called lopolith.
Medial moraines: A ridge of till formed on the inner edges (in the middle of the glacier) of two glaciers where they converge is called medial moraines.
Mesa: A flat-topped and steep-sided highland covered with basalt lava or capped with resistant rock are called Mesa. It is larger than a butte and smaller than a plateau.
Metamorphic rock: Metamorphic rocks are formed due to changes in the composition of either sedimentary or igneous rocks, e.g., slate, marble, etc.
Phacolith: Phacoliths formed when magma cooled and solidified along the anticline and syncline in the areas of folded mountains.
Sedimentary rock: Sedimentary rocks formed through lithification and cementation of the sediments deposited in water bodies or by the accumulation of fossils, e.g., limestone, sandstone, etc.
Siliceous rock: Sedimentary rock containing a high amount of silica is called Siliceous rock.
Sill: Sills are formed when magma entered and solidified in between layers of sedimentary rocks. The sills are generally laid down parallel to the layers of sedimentary rock. The thick layer of magma is called ‘sill’ and the thin bed is called ‘sheet’. The thickness of the sill varies from a few centimeters to several meters. The sill is much harder than the surrounding rocks and exposed when the adjacent rocks get eroded.
Terminal moraines: A ridge of till deposited by a glacier at the line of maximum advance of the glacier or near the mouth of the glacier is called a terminal glacier.
Unconformity: Irregularity or discontinuity in the sequence of rocks, containing a gap in a geological period is called an unconformity. For example, there may be a sequence of inclined layers on top of parallel and horizontal layers (this is called angular discontinuity), or there may be deposits of boulders on top of fine-grained layers, etc.
Anaerobic Stage of Soil: The stage at which soil is completely saturated but least aerated is called the anaerobic stage or those conditions where the amount of oxygen used by the organism present in the soil exceeds the amount of oxygen diffused into the soil. The soil at this stage is also known as poorly aerated soil.
Azonal soil: The soil with poorly developed horizons or without soil horizons is called azonal soil e.g., Alluvium and Sand dunes. There is complete uniformity in the structure and properties of the soil from the upper layer to the lower layer.
Capillary action: The action by which a liquid such as water is drawn upward (towards the earth’s surface) into small openings like pores in a rock because of surface tension is called capillary action. It works against gravity.
Cutans: A coating of various substances is found around peds or individual soil particles. Peds with such coatings are called Cutans e.g., clay cutan, iron oxide cutan, manganese oxide cutan, etc.
Edaphons: The organisms living in the soil are called edaphon. Their size varies from 20 cm to 20 micrometers.
Eluviation: The downward movement of dissolved minerals and fine particles in the water from the upper horizon of the soil to the lower is called eluviation or leaching. The process takes place due to water infiltration.
Field capacity stage: When 50 percent of pores in the soil are filled with water and the remaining 50 percent are occupied by air, that state of soil is called the field capacity stage. At this stage air and water in the soil are considered to be ideal for agriculture or growing crops. It is the amount of water that is held in the soil by hydrogen bonding against gravity.
Illuviation: The deposition of various minerals like clay, alumina, iron, humus, etc., from the upper layer (horizon A)of the soil to the lower layer (horizon B) because of the downward movement of water in the soil profile is called illuviation.
Illuviation zone: The B horizon of the soil profile is called the illuviation zone because this layer is characterized by the deposition of clay minerals and organic matter.
Mineral horizon: The layer located below the uppermost organic horizon of the soil profile is called the mineral horizon. It consists of two types of minerals Skelton minerals like quartz and clay minerals.
Organic horizon: The uppermost layer in the soil profile is called the organic horizon. It is characterized by the wealth of living as well dead organisms.
Parent materials: The solid rock below the soil profile is called the parent material. It is known as parent material because all the horizons or layers in the soil profile located above are formed from the weathering materials of the basal or parent rock.
Ped: A naturally formed aggregate of small soil particles is called a ped. When the soil is plowed, these peds break down into small pieces. These are called clad or lump.
Regolith: The weathered material of the parent rock is called regolith. It represents the lower C layer in the soil profile.
Root osmosis: The process by which plants obtain nutrients present in the soil from their roots is called root osmosis.
Saturated stage of soil: When all the holes and voids in the soil are filled with water, then this state is called the saturated stage of the soil.
Soil: The loose and unorganized earth materials produced by the disintegration and decomposition of rocks are called soil. Soils are made up of living and dead organic matter, minerals, water, and air.
Soil Enrichment: Under the process of soil enrichment, all those activities and processes are included which are helpful in the increase of organic and mineral substances in the soil.
Soil Profile: The vertical horizons of the entire soil layer located in the middle of the base rock below the upper surface of the soil are collectively called soil profile or soil lateral.
Wilting stage: When there is complete lack of water in the soil after all the water has been absorbed by evaporation and by the roots of the plants, that condition of the soil is called wilting stage.
Zonal soils: The soils formed under well aerated and well drained conditions are called zonal soils.
Badlands: It refers to arid lands, usually devoid of vegetation and cut into a maze of ravines and sharp crested hills. This type of terrain develops in areas with weakly consolidated sediments.
Badlands topography: In arid and semi-arid regions, a topography with a bumpy surface resulting from the formation of gullies and ravines by water erosion is called Badlands topography.
Bajada: In arid and semi-arid regions, a gentle sloping plain that lies between pediment and the playa is called bajada. Bajada is formed when alluvial fans merge along a mountain front or foothills.
Barkhan: Arc-shaped or crescent-shaped transverse sand dunes formed by the deposition of sand by wind in hot dry desert areas are called Barkhan.
Deflation: The process of blowing away unorganized and loose materials, especially sand, from hot dry deserts is called deflation.
Demoiselles (Land Pillars): Due to the vertical formation of hard and soft rocks in hot dry desert parts, due to the erosion of the soft rock between the hard rocks, hard rock pillars are formed which are called land pillars.
Desert Varnish: Dark red or black colored coating of iron oxide, silica etc. on the outer surfaces of boulders, pebbles and other types of boulders scattered on the rocky surface of hot dry desert parts is called desert varnish.
Driekanter (Dry Kanter): Blocks with 3 faces eroded by wind on the naked surface of stony hot deserts are called Drykanter.
Erg (Arg): Hot deserts with mobile sands are called Reg. The area of an average sized Reg is 1,88,000/- sq km while the world’s largest erg is Rabkhali Erg of Arabia which has an area of 5,60,000 sq km. Is.
Inselberg (Inselberg): At the end of the erosion cycle in desert areas, small hills and dunes left over from erosion on the desert surface are called Inselberg. They are also called Bornheit after the name of a scholar named Bornheit. Generally inselbergs are like open domes of granite and gneiss rock.
Loess: Layer less loose deposits formed by the deposition of fine sediments blown by the wind are called loess.
Anthropogenic weathering: At present, with the help of human state-of-the-art technology, various economic activities (such as mineral mining, road construction and blasting of hills with dynamite for mineral extraction, etc.) break down many times faster than natural processes in rocks. – explodes. In this way, breaking of rocks by man is called anthropogenic weathering.
Biochemical weathering: The weathering of rocks by organic substances (both plants and animals) and disintegration i.e. chemical weathering is called biochemical weathering.
Block disintegration: The process of fragmentation of rocks into large blocks because of repetitive contraction and expansion of rocks due to temperature changes is called block disintegration.
Cambering: The reduction of pressure caused by the removal of the overlying rock mass causes the rock below to collapse. Due to expansion in it, the action of cracking with the help of vertical joints is called cambering.
Carbonation: Carbonate rocks coming in contact with water containing carbon dioxide gasThe process of dissolving (limestone, dolomite etc.) is called carbonation.
Chemical weathering: Water containing atmospheric carbon dioxide becomes an active solvent. The chemical changes that take place in the rocks containing soluble elements coming in contact with it are called chemical weathering. Example: Oxidation, Carbonation, Hydration etc.
Desilication (separation of silica): process of separation of silica from silica-rich rocks is called desilication or separation of silica. Exfoliation: After the upper rocks have been eroded by erosion, when the granite rocks buried below come out, due to the release of pressure and temperature, thin layers start peeling off from such rocks. This process is called weathering or onion weathering.
Granular disintegration (disintegration of rocks into fine particles): Due to high diurnal temperature difference in hot dry parts, due to expansion (in day) and contraction (at night) in the upper layers of the rocks respectively, the rocks crack due to which the upper surface is covered with small particles. I ‘break’ and fall apart. In this way, the disintegration of rocks into small parts due to temperature is called granular disintegration.
Hydration: When rocks swell after absorbing water, they crack due to expansion in volume and shrinkage when water dries up. This action is called hydration.
Mechanical Weathering: The process of disintegration of rocks by sunlight, frost and wind is called mechanical weathering.
Oxidation: The process of rusting of rocks containing iron minerals in contact with water mixed with atmospheric oxygen is called oxidation
Shattering: The process of cracking of upper thin layers of rocks heated by insolation due to light splashes of rain is called shattering.
Weathering: The static process of disintegration and disintegration of rocks in their original place by different factors in different ways is called weathering.
Cloud: A visible, dense mass of suspended water droplets or ice crystals suspended in the air is called a cloud. Clouds usually form when air is forced to rise such as at a front, over mountains, or because of convection.
Dew: Moisture that condenses from the air onto the surface, generally on plant leaves. Dew forms during cool nights when there is light wind. The heat that the ground absorbed during the day is radiated away from the earth’s surface. This produces a layer of cool air near the surface. If the air is chilled sufficiently for its relative humidity to exceed 100 percent, moisture will condense onto surfaces, which is dew.
Fog: Fog is a cloud that occurs at the Earth’s surface. It forms when air is cooled below its dew point and water vapor condenses around small particles of dust or other particles in the air. This usually occurs when two air masses of differing temperature meet, but can also occur when warm air passes over a cooler surface. The density of the fog depends upon the number of minute water droplets present. Visibility in fog is below 1 km or 0.6 miles.
Precipitation: Falling of moisture from the air on the earth’s surface in the form of rain, hail, snowfall, sleet, etc. is called precipitation. Precipitation began within clouds by the Bergeron- Findeisen process, by the coalescence process, or by a combination of both operating together. For precipitation to reach the ground some other conditions must be satisfied. The droplet or ice crystal produced by one of the above mechanisms must be sufficiently heavy to overcome upward vertical motion and large enough to withstand evaporation beneath the cloud base. Thus, some clouds can be seen to be giving precipitation that does not reach the ground.
Wilting Point: That point in the soil moisture balance when only hygroscopic water and some bound capillary water remain. Plants wilt and eventually die after prolonged stress from a lack of available water.
Wind: The horizontal movement of air relative to the surface of the earth is called wind. The wind is produced because of the air pressure differences from place to place and it is influenced by the Coriolis force and surface friction.
Wind Abrasion: Mechanical wearing action of wind-driven mineral particles striking exposed rock surfaces.
Cyclogenesis: The formation of cyclones, especially mid-latitude depressions (also known as frontal wave depressions). Cyclogenesis occurs in specific areas, such as the western North Atlantic, western North Pacific, and the Mediterranean Sea, and is favored where thermal contrasts between air masses are greatest. Cyclogenesis is primarily the result of the convergence of air masses.
Cyclone: Cyclone is a weather system having low pressure in the center around which winds blow counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. It is also known as depression. One should not to be confused with a tornado, which is a much smaller weather phenomenon associated with severe thunderstorms.
Cyclone wave: The wave-like distortion of flow in the middle and upper troposphere associated with a mid-latitude depression.
Cheyenne fog: Upslope fogs in the south-eastern Wyoming of the USA are called Cheyenne fogs. it is named after a place Cheyenne.
Cloud droplets: The deposition of moisture after condensation around large hygroscopic nuclei is called a cloud droplet.
Cloud seeding: Cloud seeding is an artificial means of injection of seedable materials (e.g., iodine compounds, solid carbon dioxide, dry ice, iodide, etc.) in the supercooled precipitable clouds to induce precipitation by man.
Dew point: The temperature at which the given air is saturated i.e., the humidity holding capacity and absolute humidity of a given volume of air at a given temperature and point of time become equal, is called the dew point.
Drizzle: Drizzle is defined as the fall of numerous tiny water droplets having a diameter of less than 0.5mm.
Freezing rains: Freezing rains or freezing drizzles are formed when the drizzles or very light rains occur below 0°C temperature, they are frozen before reaching the ground surface and hence are called freezing rains or freezing drizzles. They are also called as crachins.
Hail: Hail consists of large pellets or spheres (balls) of ice. Hail is a form of solid precipitation wherein small balls or pieces of ice, known as hailstones, having a diameter of 5mm to 50 mm fall downward known as hailstorms.
Inversion of rainfall: The decrease of rainfall with increasing height along a mountain slope because of a marked reduction in moisture content upward is called inversion of rainfall.
Leeward slope: The opposite side slope of the hills or mountains through which the wind descends and is warmed adiabatically resulting in very low rainfall is called the leeward slope and rain shadow region.
Man-induced precipitation: Man-induced precipitation refers to the artificial nucleation of ice crystals in supercooled clouds through the injection of dry ice, silver iodide, finely ground salt, solid carbon dioxide, iodine compounds, etc. to augment, the condensation process to yield precipitation.
Pea-soup: The urban smog over London city is locally called pea-soup.
Pogonip: The fogs comprising numerous ice crystals and supercooled water droplets are locally known as pogonip in the mountains of the USA.
Rainfall regime: The rainfall regime refers to the seasonal distribution and variation of rainfall.
Rime: Rime is an opaque coating of tiny, white, granular ice particles, caused by the rapid freezing of supercooled water droplets on impact with an object.
Saturated air: The air having cent percent relative humidity is called saturated air. In other words, saturated air is that in which absolute humidity and moisture retaining capacity are equal.
Sleet: Sleet refers to a mixture of snow and rain but in American terminology, sleet means falling of small pellets of transparent or translucent ice having a diameter of 5mm or less.
Virga: Virga refers to such type of precipitation which after occurring from cumulus clouds in summer is evaporated before reaching the ground surface.
Lapilli: Pea-size rock fragments of volcanic materials are called lapilli.
Lateral moraines: An accumulation of till deposited along the side margins of a glacier are called lateral moraines.
Lava Flow: When magma erupts from a volcano and flows slowly in the form of lava on the earth’s surface, then such a flow is called a lava flow.
Lithosphere: The rigid part of the earth’s crust, which includes the oceanic crust, continental crust, and part of the mantle above the asthenosphere is called the lithosphere.