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Absolute
humidity the amount of water vapour in the air in
grams per cubic metre.
Absorption the absorbing of
insolation to solids, liquids and gases on the
surface and in the atmosphere.
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.
Accessibility the level of difficulty associated with
getting to a location or feature within a larger area
measured in distance, time and/or cost.
Accretion growth of a natural feature by enlargement
due to the addition of more of the same material.
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.
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.
Acid
lava lavas containing high percentage of silica. Tend
to have high melting points and to be highly viscous.
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.
Acquired
immune deficiency syndrome a fatal syndrome caused by
HIV.
Main characteristic is a greatly reduced ability of the body
to fight infection. Victims usually die from other illnesses
they can no longer fight, rather than aids itself, which can
lead to underreporting.
Active
layer the upper few metres of soil in a
periglacial area which undergoes thawing in summer
and is prone to mass movement relative to the
permafrost layer below.
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.
Adret
slope a south-facing slope.
Adsorption physical or chemical bonding of solid
particles with liquids or gases.
Advection horizontal transfer of heat by a
horizontally moving air mass.
Aeolian
lit. of the wind. Refers to transportation, erosion
and deposition by wind action.
Afforestation planting of trees on previously
un-wooded land.
Aftershock ground tremors occurring after a major
earthquake but associated with the same
focus
point.
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.
Agglomeration the grouping together of businesses in
the same area to minimize costs through
linkages.
Aggradation
deposition of
load
within river channels.
Agribusiness corporations organized to provide
vertical linkages both below and above the farm itself.
Agriculture -
the science, art, and business
of cultivating the soil, producing crops, and raising
livestock; farming.
Agricultural chain every step in the process(es) that
lead to the consumption of food.
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.
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.
·
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.
Aids
see
acquired
immune deficiency syndrome
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.
Air
pressure the force of the atmosphere on the surface.
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.
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.
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.
Alluvium
river deposits found either on the
floodplain or historic
point-bars.
Alpha
index a measure of
connectivity in a
network.
Expresses the
cyclomatic number as a percentage of the maximum
possible circuits. A low percentage indicates low
connectivity.
Formula is: α = (e-v+1) x
100
2v-5
where e is
number of edges and v is number of vertices.
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.
Altitude
height above sea-level.
Anabatic
the movement of air up slopes due to convection.
Anaerobic lit. 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.
Antecedent drainage the maintenance of course by an
old river over more recent uplifting of the land surface.
Anticyclone a stable, generally subsiding air mass
producing high pressure, warming conditions. The resultant
fall in
relative
humidity leads to clear skies.
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.
Appropriate technology see
alternative technology. Appropriate technology might
more commonly be the term applied to alternative technology
originating externally.
Aquaculture highly managed use of water environments
to enhance food production e.g. fish farms.
Aquifer
a
permeable rock which stores and transfers water. Useful when
underlain by
impermeable rock to trap the water and allow it to be tapped.
Arable
cultivation of crops such as cereals, legumes, roots and
leaves.
Arch
when a cave in the side of a
headland
is eroded right through to the other side forming a
bridge-shaped landform.
Arctic
air an
air mass
originating over the Arctic Circle.
Area of
Outstanding Natural Beauty (AONB) in the UK, land
areas given special protection by act of parliament to
preserve their natural beauty. Local authorities maintain
strict control over permission for development within them.
England has 35, Wales has 4, 1 is astride the border, and N.
Ireland has 9.
Arκte
a sharp, steed-sided ridge in an upland area. Resultant of
enlargement of adjacent
corries.
Arid
climatic areas characterized by extreme dryness. Simple
definitions set maximum annual precipitation (up to 250mm
per year). More complex definitions recognize the importance
of
evapotranspiration (or
potential evapotranspiration) where precipitation is
very low).
Arroyo
approximate rectangular shaped valley cut in
floodplain
alluvium,
with a smaller stream in the base. Usually found in
semi-arid areas.
Asian
Tigers Hong Kong, Singapore, South Korea and Taiwan.
So named for their rapid economic growth from 1970s to crash
of 1997.
Aspect
direction in which a slope faces.
Asthenosphere layer of rock in the
mantle
approximately 80km deep and at a temperature of 1400°C.
Rocks here become much softer and more easily deformed than
in the
lithosphere above.
Atmosphere layer of gases surrounding earth and held
there by gravity. Nitrogen forms 78.09% by volume and Oxygen
20.95%. The remaining 0.96% is made up of a further 19
gases. The boundary of the atmosphere is 1000km above sea
level but 99% of the gases are held in the lower 40km. This
is split into three layers the
troposphere and the
stratosphere separated by the
tropopause. Carbon dioxide in the troposphere allows
photosynthesis and also holds long-wave radiation to give
warmth. Temperatures fall with altitude at a rate of
approximately 6.5°C per km to the tropopause where they are
stable. Ozone in the stratosphere traps ultraviolet
radiation and leads to an increase in temperature in this
layer.
Atmospheric particulates solids present in the
atmosphere. May be naturally occurring dusts and soils etc.
or human pollutants such as smoke.
Atoll
a ring-shaped
coral
reef.
Attrition a process of
erosion
where the collisions between parts of the
load
lead to
comminution.
Autonomy
the right of self-government. Exists at
nation-state and sub-national, regional levels.
Autotroph an organism that can produce nutritional
organic substances from simple inorganic substances. Thus,
plants grow by synthesizing carbon dioxide and water using
sunlight.
Avalanche rapid, down slope mass movement of ice
and/or snow due to a trigger overcoming reduced friction in
an unstable
accumulation.
Azonal
soil a soil which does not demonstrate much, if any,
evidence of soil-forming processes. Often little more than
regolith, they are controlled by
parent
material and
relief.
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