GLOSSARY - Physical Geography - page 151

Carbon footprint The amount of carbon that an individual or an
organisation uses over a given time period. It is often expressed in
terms of the equivalent amount of carbon dioxide.
Catchment area The area of land that drains to a given point on a

river or lake.
Cation exchange capacity A measure of a soil's ability to hold and
release certain elements, which is dependent on the net negative charge
of the clay minerals within it.
Chemosynthesis The use of energy from oxidation of chemicals to
manufacture carbohydrates for living organisms from water and carbon.
The process uses chemical nutrients to produce energy for carbohy-
drate production rather than the Sun's energy as used in

photosynthesis.
Cirques Basins carved into mountain sides by cirque glaciers. They
possess steep rock walls, a rock basin and terminal moraine.
Cohesion The attraction between molecules in a substance that holds
the substance together.
Col A hollow that forms in an arête from localised erosion, often pro-
viding a pass between mountain peaks.
Convection The molecular motion responsible for the transfer of
energy, such as heat, through a fluid.
Convergent plate boundary Where two tectonic plates collide, creat-
ing major physical features, such as mountains, and hazards such as
earthquakes and volcanoes.
Coriolis effect The rotation of the Earth on its axis causes a moving
object or fluid to be apparently deflected. Deflection occurs to the
right in the northern hemisphere and to the left in the southern hemi-
sphere and is stronger at higher latitudes.
Corries See cirques.
Crag and tail features Formed as a glacier slides over a resistant rock
mass ('crag') depositing sediment on the downstream side ('tail'), creat-
ing a streamlined feature.
Delta Large accumulation of sediment where a river enters the sea or a
lake creating a raised river mouth. Deltas often have many branching
channels that feed out from the main river.
Desertification The advancement of desert-like conditions due to
human action or climate change resulting in soils with organic matter
contents below 1.7 per cent.
Dew point The temperature at which a cooling air parcel becomes sat-
urated with water vapour, at which water vapour condenses to form
liquid water.