Dictionary of Physical Geography
By Students’ Academy
Copyright@2011Students’ Academy
Smashwords Edition
Chapter 1: A
A
Abiotic
Abiotic is the term not used for a-living thing. Usually refers to the physical and chemical components of an organism's environment. It is also called inorganic.
Ablation
Ablation refers to the removal of ice or snow from a glacier or snowfield by melting, sublimation, and/or calving.
Ablation Zone
Ablation Zone is the region in a glacier where there is a surface net removal of snow and/or ice by melting, sublimation, and/or calving.
Abrasion
Abrasion means the process of physical wearing and grinding of a surface through friction and impact by material carried in air, water, or ice.
Absolute Humidity
Absolute Humidity refers to the measurement of atmospheric humidity. Absolute humidity is the mass of water vapor in a given volume of air (this measurement is not influenced by the mass of the air). Normally expressed in grams of water vapor per cubic meter of atmosphere at a specific temperature.
Absolute Zero
Absolute Zero means the temperature of -273.15° Celsius. At this temperature atomic motion stops.
Absorption
(1)Absorption is the process of taking in and being made part of an existing amount of matter.
(2) Absorption also refers to the interception of electromagnetic radiation or sound.
Absorption (Atmospheric)
In terms of physical geography, Atmospheric Absorption is a process in which solar radiation is retained by a substance and converted into heat energy. The creation of heat energy also causes the substance to emit its own radiation. In general, the absorption of solar radiation by substances in the Earth's atmosphere results in temperatures that get no higher than 1800° Celsius. According to Wien's Law, bodies with temperatures at this level or lower would emit their radiation in the longwave band.
Abstract Space
Abstract Space is the geographic model or representation of the real world. For example, maps and globes are abstractions of the real world or concrete space.
Abyssal Fan
Abyssal Fan refers to a fan shaped accumulation of sediment from rivers that is deposited at the base of a submarine canyon within a ocean basin.
Abyssal Plain
Abyssal Plain is the geographical name for ocean floor.
Acclimation
Acclimation refers to the slow adjustment of an organism to new conditions in its environment.
Accretion
Accretion refers to the growth of the continental masses over geologic time via the addition of marine sediments. These sediments are added on to the edges of the continents through tectonic collision with other oceanic or continental plates.
Accumulation
Accumulation refers to the surface addition of snow to a glacier or snowfield.
Accumulation Zone
(1) Accumulation Zone refers to the region in a glacier where there is a surface net addition of snow.
(2)Accumulation Zone is the part of a hill slope that has a net gain of material leading to a progressive raising of the slope's surface.
Acid
(1) Acid is the substance which has a pH less than 7.
(2) Acid is the substance that releases hydrogen ions (H+).
Acid Deposition
Acid Deposition refers to the atmospheric deposition of acids in solid or liquid form on the Earth's surface. Also see acid precipitation
Acidic
Any substance with a pH below 7 is called Acidic.
Acidic Solution
Acidic Solution means any water solution that is acidic (pH less than 7) or has more hydrogen ions (H+) than hydroxide ions (OH-). Also see basic solution and neutral solution.
Acid Precipitation
Acid Precipitation refers to the atmospheric precipitation with a pH less than 5.6. Normal pH of precipitation is 5.6.
Acid Rain
Acid Rain is the rain with a pH less than 5.6. Normal pH of precipitation is 5.6.
Acid Shock
Acid Shock refers to a sudden acidification of runoff waters from the spring melting of accumulated snow in the middle latitudes because of the winter deposition of acidic precipitation.
Actinomycetes
Actinomycetes refers to a group of filamentous microorganisms that are intermediate between bacteria and fungi.
Active Layer
Active Layer means the upper zone of soil in higher latitude locations that experiences daily and seasonal freeze-thaw cycles.
Active Remote Sensing
Active Remote Sensing refers to the form of remote sensing where the sensor provides its own source of electromagnetic radiation to illuminate the object understudy. Radar is an example of an active remote sensing device.
Actual Evapotranspiration
Actual Evapotranspiration means the amount of water that is actually removed from a surface due to the processes of evaporation and transpiration.
Actual Mixing Ratio
Actual Mixing Ration is another term used to describe mixing ratio.
Adaptation
(1) Adaptation refers to the evolutionary adaptation - a genetically based characteristic expressed by a living organism. Particular adaptations found in populations become frequent and dominant if they enhance an individual's ability to survive in the environment.
(2) Adaptation refers to the physiological adaptation - change in an organism's physiology as a result of exposure to some environmental condition.
Adaptive Radiation
Adaptive Radiation refers to the evolution of a number of new species from one or a few ancestor species over many thousands or millions of years. Normally occurs after a mass extinction creates a number of vacant ecological niches or when a radical change in the environment produces new ecological niches.
Adiabatic
Adiabatic is a physical process in which heat does not enter or leave a system. In the atmospheric sciences, adiabatic processes are often used to model internal energy changes in rising and descending parcels of air in the atmosphere. When a parcel of air rises it expands because of a reduction in pressure. If no other non-adiabatic processes occur (like condensation, evaporation and radiation), expansion causes the parcel of air to cool at a set rate of 0.98° Celsius per 100 meters. The opposite occurs when a parcel of air descends in the atmosphere. The air in a descending parcel becomes compressed. Compression causes the temperature within the parcel to increase at a rate of 0.98° Celsius per 100 meters.
Adiabatic Cooling
Adiabatic cooling means the cooling of a rising parcel of air due to adiabatic processes.
Advection
Advection refers to the involvement of the transfer of heat energy by means of horizontal mass motions through a medium.
Advection Fog
Advection fog refers to the fog that is generated when winds flow over a surface with a different temperature. Two types of advection fog exist. When warm air flows over a cold surface it can produce fog through contact cooling. Cold air blowing over a warm moist surface produces a form of advection fog know as evaporation fog.
Aeolian
Aeolian is a geomorphic process involving wind. Alternative spelling eolian.
Aeolian Landform
Aeolian landform is a landform formed from the erosion or deposition of weathered surface materials by wind. This includes landforms with some of the following geomorphic features: sand dunes, deflation hollows, and desert pavement. Alternative spelling eolian landform.
Aerial Photography
Aerial Photography refers to the form of remote sensing that captures images of objects using photographic cameras and film from platforms in the atmosphere.
Aerobic
(1) Aerobic refers to the presence of molecular oxygen.
(2) Aerobic refers to an occurrence only in the presence of molecular oxygen.
(3) Aerobic refers to the growth in the presence of molecular oxygen.
Aftershock
Aftershock refers to the smaller earth tremors that occur seconds to weeks after a major earthquake event.
Aggradation
Aggradation means the readjustment of the stream profile where the stream channel is raised by the deposition of bed load.
Agronomy
Agronomy is the field of science that studies phenomena related to agriculture.
A Horizon
A-Horizon refers to the soil horizon which is normally found below the O horizon and above the B horizon. This layer is characterized by the following two features:
(1) It also refers to the layer in which humus and other organic materials are mixed with mineral particles.
(2) It also refers to the zone of translocation from which eluviation has removed finer particles and soluble substances.
Air Mass
Air Mass refers to a body of air whose temperature and humidity characteristics remain relatively constant over a horizontal distance of hundreds to thousands of kilometers. Air masses develop their climatic characteristics by remaining stationary over a source region for a number of days. Air masses are classified according to their temperature and humidity characteristics.
Air Pollution
Air Pollution means the toxification of the atmosphere through the addition of one or more harmful substances in the air. Substance must be in concentrations high enough to be hazardous to humans, other animals, vegetation, or materials. Also see primary pollutant and secondary pollutant.
Air Pressure
See atmospheric pressure.
Albedo
Albedo refers to the reflectivity of a surface.
Aleutian Low
Aleutian Low means sub polar low pressure system found near the Aleutian Islands. Most developed during the winter season. This large-scale pressure system spawns mid-latitude cyclones.
Alfisols
Alfisols refers to the soil order (type) of the United States Natural Resources Conservation Service Soil Classification System. Soil associated with forest vegetation. Upper layers of this soil are relatively rich in organic matter. Whitish layer found in the A horizon because of eluviation. Illuvial layer forms in the B horizon.
Algae
Algae is a simple photosynthetic plant that usually lives in moist or aquatic environments. The bodies of algae can be unicellular or multicellular is design.
Alien Species
Alien Species refers to the species which is not naturally found in a region.
Alkaline
(1) Having a pH greater than 7.
(2) Substance that releases hydroxyl ions (OH-).
Allele
Allele refers to alternative forms of a gene. Each form produces a unique inheritable characteristic.
Allelopathy
Allelopathy refers to a particular form of amensalism found in plants. In this interaction, one species produces and releases of chemical substances that inhibit the growth of another species.
Allogenic Succession
Allogenic Succession is the succession which is caused by a change in environmental conditions that is unrelated to the activities of the developing plant community.
Allopatric Speciation
Allopatric Speciation refers to the evolution of a new species because of the isolation of a small group of individuals from the other members of a population.
Allophane
Allophane refers to the hydrated aluminosilicate substance ordinarily found associated with clay minerals.
Alluvial Fan
Alluvial Fan is a large fan shaped terrestrial deposit of alluvial sediment on which a braided stream flows over. Form as stream load is deposited because of a reduction in the velocity of stream flow.
Alluvial Terraces
Alluvial terraces refers to the flat elevated benches composed of unconsolidated alluvium found either side of a stream channel. Formed when a stream down cuts into its floodplain.
Alluvium
Alluvium means the sediment that originates from a stream.
Alpha Particle
Alpha Particle is the particle of matter that is positively charged. This particle consists of two neutrons and two protons and is emitted as a form of radioactivity from the nuclei of some radioisotopes. Also see beta particle and gamma rays.
Alpine Glacier
Alpine Glacier is a small glacier that occupies a U-shaped valley on a mountain. Also called a mountain glacier.
Alpine Permafrost
Alpine Permafrost is the form of permafrost that exists at high altitudes in mountainous environments.
Alpine Tundra
Alpine Tundra is the high altitude biome dominated by a few species of dwarf shrubs, a few grasses, sedges, lichens, and mosses. Productivity is low in this biome because of the extremes of climate. Quite similar to tundra.
Alternative Hypothesis (H1)
Alternative Hypothesis is a hypothesis that has been suggested because it is believed to be false or because it is to be used as a starting point for scien 04/06/2010 12:19 ng to organize arguments.
Altitude
Altitude means the vertical distance above sea-level.
Altocumulus Clouds
Altocumulus Clouds refers to the middle altitude cloud that is colored from white to gray. This cloud is composed of a mixture of water droplets and ice crystals. It appears in the atmosphere as layers or patches that are well rounded and commonly wavelike. Found in an altitude range from 2,000 to 8,000 meters.
Altostratus Clouds
Gray-looking middle altitude cloud that is composed of water droplets and ice crystals. Appears in the atmosphere as dense sheet like layer. Can be recognized from stratus clouds by the fact that you can see the Sun through it. Found in an altitude range from 2,000 to 8,000 meters.
Amensalism
Amensalism means the interspecific interaction where one species suffers in terms of fitness, while the fitness of the other species does not change. See allelopathy.
Amino Acid
Amino Acid is the organic nitrogen containing acids which are used to construct proteins.
Ammonia
Ammonia is a chemical compound composed of nitrogen and hydrogen (NH3). Component of the nitrogen cycle. Immediately released from organic matter upon decomposition.
Ammonium
Ammonium is a chemical compound composed of nitrogen and hydrogen (NH4). Component of the nitrogen cycle. Product of organic matter decomposition. Can be fixed to clay minerals and later exchanged.
Amphibian
Amphibian refers to a group of vertebrate animals that can inhabit both terrestrial and aquatic habitats. This group of animals consists of frogs, newts, and salamanders. These organisms live at the land/water interface and spend most of their life in water. Descended from fish and ancestors to reptiles.
Amphibole
Amphibole refers to a group of double chained inosilicate minerals whose basic chemical unit is the tetrahedron (SiO 4 ). They are common rock forming minerals and are found in most igneous and metamorphic rocks. They form at low temperatures with the presence of water in the crystallization environment. There are about 60 recognized mineral types in this group.
Anaerobic
(1) Anaerobic means the absence of molecular oxygen.
(2) Anaerobic refers to the occurrence only in the absence of molecular oxygen.
(3)Anaerobic refers to the growth in the absence of molecular oxygen.
Andesite
Andesite is an extrusive igneous rock that develops from a magma that is chemically between felsic and mafic and whose mineral crystals are fine.
Andisols
Andisols refers to the soil order (type) of the United States Department of Agriculture Comprehensive Soil Classification System. These soils develop from parent materials that are volcanic in origin.
Anemometer
Anemometer is a mechanical instrument used to measure wind speed. These instruments commonly employee three methods to measure this phenomenon: 1) A device with three or four open cups attached to a rotating spinal. The speed of rotation is then converted into a measurement of wind speed; 2) A pressure plate that measures the force exerted by the moving wind at right angles; 3) An instrument consisting of a heated-wire where electrical resistance (temperature of the wire) is adjusted to account for heat lost by air flow. The faster the wind the greater the heat loss and thus the more energy that is required to keep the wire at a constant temperature. As a result, wind speed is measured through the drain of electrical current.
Aneroid Barometer
Aneroid Barometer is a barometer that measures atmospheric pressure via the expansion and contraction of a sealed hollow cell which is partially depleted of air.
Angiosperms
Angiosperms refers to a group of vascular plants who encase their seeds in a mature ovary or fruit.