1. Ablation - Ablation is removal of material from the surface of an object by vaporization, chipping, or other erosive processes. Examples of ablative materials are described below, and include spacecraft material for ascent and atmospheric reentry, ice and snow in glaciology, biological tissues in medicine and passive fire protection materials.
The net loss of water from a glacier through melting, calving, evaporation, sublimation or wind transport. Is dominant to accumulation over space and time when the glacier enters warmer conditions.
2. Abiotic - It is not from living things. In physical geography, used to describe non-living components of an environment such as rock or water. Non-living thing. Usually refers to the physical and chemical components of an organism's environment. Also called inorganic.
3. Abrasion - Degradation of the land through the scouring action of materials being carried by an agent of erosion. Rates vary according to amount of material carried, energy of the agent and hardness of materials involved. Physical wearing and grinding of a surface through friction and impact by material carried in air, water, or ice.
4. Absolute humidity - The amount of water vapour in the air in grams per cubic metre. 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.
5. Absorption - The absorbing of isolation to solids, liquids and gases on the surface and in the atmosphere. Process of taking in and being made part of an existing amount of matter. Or Interception of electromagnetic radiation or sound.
6. Abstract Space - Geographic model or representation of the real world. For example, maps and globes are abstractions of the real world or concrete space.
7. Abyssal plain - Large, relatively flat areas of ocean floor found at 5,000-6,000m below sea level. If sediments are discharged from a river and deposit relatively quickly onto the plain they may form an abyssal fan. Fan shaped accumulation of sediment from rivers that is deposited at the base of a submarine canyon within a ocean basin.
8. Accessibility - The level of difficulty associated with getting to a location or feature within a larger area measured in distance, time and/or cost.
9. Accretion - Growth of a natural feature by enlargement due to the addition of more of the same material. 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.
10. Accumulation - The net gain in ice mass by precipitation of snow, arrival of snow from avalanche, arrival of snow by wind transport or refreezing of melt water. Is dominant to ablation over space and time when the glacier enters colder conditions. Surface addition of snow to a glacier or snowfield.
11. Acidification - The increase in acidity in an environment due to the development of a particular biome or due to human pollution causing unnaturally high levels of acid rain.
12. Acid lava - Lavas containing high percentage of silica. Tend to have high melting points and to be highly viscous.
13. Acidophilous - An organism which prefers acid conditions.
14. Acid rain - Refers to the unnatural increase, through human pollution, in the acidity of water precipitation. Most commonly sulphuric and nitric acids formed from by-products of fossil-fuel burning and metal smelting.
15. Active layer - The upper few meters of soil in a periglacial area which undergoes thawing in summer and is prone to mass movement relative to the permafrost layer below.
16. Adiabatic - Change in temperature due to expansion or contraction of a parcel of air which thus change the pressure and therefore the temperature. No heat transfer between the air parcel and the surrounding air.
17. Adret slope - A south-facing slope.
18. Adsorption - Physical or chemical bonding of solid particles with liquids or gases.
19. Advection - Horizontal transfer of heat by a horizontally moving air mass.
20. Afforestation - Planting of trees on previously un-wooded land.
21. Aftershock - Ground tremors occurring after a major earthquake but associated with the same focus point.
22. Agent of erosion - The direct source of movement that can cause erosion through the transfer of energy or transport of rock material: water (rivers and waves), wind and ice.
23. Agglomeration - The grouping together of businesses in the same area to minimize costs through linkages.
24. Aggradation - Deposition of load within river channels.
25. Agribusiness - Corporations organized to provide vertical linkages both below and above the farm itself.
26. Agriculture - The science, art, and business of cultivating the soil, producing crops, and raising livestock; farming.
27. Agricultural chain - Every step in the process(es) that lead to the consumption of food.
28. Agricultural revolution - A period of fundamental changes to agricultural systems which tend to concentrate land and production into fewer hands while increasing yields. Changes may be organizational and technological.
29. Aid - Transfer of resources from a donor to a recipient. May be undertaken at a variety of scales usually under the following conditions: bilaterally between national governments. The donor will usually attach specific conditions both economic and political. Multilaterally where donors contribute to an agency (e.g. World Bank) which then distributes to recipients again imposing political and economic conditions but at a system level.
30. Voluntary aid - Charitable, non-governmental organizations (NGOs) generate income from collection campaigns in the donor country for use in smaller-scale often community level schemes in recipient countries. Usually not tied.
31. Air mass - Large body of air with shared temperature and humidity characteristics associated with its area of origin e.g. maritime or continental; tropical or polar.
32. Air pressure - The force of the atmosphere on the surface.
33. Albedo - The amount of insolation reflected from the atmosphere and surface back to space. Darker, heavily vegetated surfaces have low albedo, snow and ice have high albedo. Angle of sun causes variation over time of albedo of water surfaces.
34. Algae - Collective name for a group of chlorophyll-containing plants, ranging in size from single cells to stems, including seaweeds and freshwater forms.
35. Algal bloom - Rapid growth of phytoplankton in water bodies usually in the surface layers. May be hazardous both through the production of toxins and through the blocking of insolation to lower layers.
36. Allochthonous sediment - One in which the major components have formed in situ.
37. Allogenic - when an external environmental factor causes a process to occur.
38. Alluvial cone - An alluvial fan with highly steep slopes usually found where mountain streams exit narrow valleys.
39. Alluvial fan - A fan-shaped deposit of river load where energy has been lost due to the river exiting abruptly from a narrow upland valley to a lowland plain.
40. Alluviation - The process of depositing alluvium.
41. Alluvium - River deposits found either on the floodplain or historic point-bars.
42. Alternative technology - (Usually interchangeable with appropriate or intermediate technology) The use of low-cost, often labour-intensive, technology, based on local resources, that is appropriate to Economically Less Developed Countries. May originate internally or externally.
43. Altitude - Height above sea-level.
44. Anabatic - The movement of air up slopes due to convection.
45. Anaerobic - Literally without free oxygen. In geography, applied to waterlogged soils which will then experience reduction of ferric compounds to ferrous compounds and turn from red to blue colourings.
46. Antecedent drainage - The maintenance of course by an old river over more recent uplifting of the land surface.
47. Anticyclone - A stable, generally subsiding air mass producing high pressure, warming conditions. The resultant fall in relative humidity leads to clear skies.
48. Anvil clouds - Rapidly rising column of air in a convectional thunderstorm will soon reach the tropopause and be forced to spread in its upper portion to form an anvil shape.
49. Appropriate technology - See alternative technology. Appropriate technology might more commonly be the term applied to alternative technology originating externally.
50. Aquaculture - Highly managed use of water environments to enhance food production.
e.g. fish farms.