Geoscience Reference
In-Depth Information
either downward- or upward-moving water enriched in
calcium.
Calcifuge
Plant which requires a calcium-free soil with
an acid
pH
value.
Caldera
A major land surface depression containing one
or more volcanic vents and forming by large-scale
subsidence as the parent
magma
chamber or
diapir
gradually cools and contracts.
Calving
The detachment of
icebergs
from a glacier or ice
shelf which terminates in water into the receiving lake or
marine basin.
Cambering
Tensile fracture and gravitational sliding or
sagging of strong, brittle rocks where they are undermined
by the failure of underlying weaker, more ductile rocks on
hill slopes.
Capillary
Said of the connected pores or fine 'tubes' in
soil which are capable of retaining and moving water
against gravity by surface tension or suction, and said of
the water itself.
Capillary water
Water held within the capillary pores of
soils; mostly available to plants.
Carbonation
The solution of carbon dioxide in water,
forming weak carbonic acid which enhances its
'aggressivity' or solution potential; a key preliminary stage
in the solution of limestones.
Carnivores
Organisms which are flesh-eating and
therefore occupy the third or higher
trophic level
in
ecosystems
.
Cascading system
A system composed of a chain of
subsystems which have both spatial magnitude and
geographical location, and which are linked by a cascade
of mass or energy.
Catchment
A three-dimensional landsystem or
drainage
basin
which converts precipitation and groundwater
inputs to stream flow and whose components are assessed
in terms of their influence on these processes.
Catena
The sequence of soils which occupy a slope
transect, from the topographic divide to the bottom of the
adjacent valley.
Cation
An atom which has lost one or more negatively
charged electrons and is thus itself positively charged.
Cation exchange
The process whereby cations in the soil
solution exchange with those adsorbed on soil colloids.
Cation exchange capacity
(CEC) The total amount of
exchangeable cations which a soil can adsorb on its
colloidal surfaces.
Cavitation
The implosion of bubbles or cavities against
a channel wall during rapid, turbulent stream flow and its
enhancement of fluid shear stress.
Cenozoic
The 'most recent' era of geological time,
commencing c. 65 Ma ago. It comprises the formerly
Black body
An ideal radiating substance which emits
and absorbs all the radiation appropriate to its absolute
temperature.
Black box
A system which is treated as a unit without
any understanding of its internal relationships. Only the
inputs and outputs are identified.
Blockfield
Mountain-top debris dominated by large
angular blocks and representing a residual product of
frost shattering
, from which fine debris has been flushed
out by wind or water; also known as
felsenmeer
.
Blocky
A type of soil structure which is cube-like and
consists of sides with angular or sub-angular corners.
Blow-out
A
deflation
depression, eroded by wind from
the face of a vegetated dune.
Bomb
Unconsolidated, blocky
pyroclastic
material,
larger than 64 mm in diameter, ejected by volcanic activity.
Bora
A dry, cold air drainage which penetrates the
Adriatic basin from the European mainland to the north,
especially in winter.
Bore
The leading edge of a
tidal wave
which rises as it
moves landward in constricted estuaries.
Boundary shear stress
The shear stress exerted by the
movement of water over a stream bed.
BP
Years
B
efore the
P
resent, based on radiometric dating
of a past event and counting back from the base year of
AD
1950.
Breaker coefficient
A relationship between wave height,
wavelength and beach slope which determines the inshore
limit of breaking waves.
Breaking wave
A sea surface wave whose oversteepened
crest outruns its base once it begins to
shoal
.
Brickearth
A lithified deposit of reworked
loess
.
Brine
Sea water, distinguished from fresh water by its
relatively high concentration of dissolved salts.
Brittle failure
The deformation of rock mass by fracture,
including
faulting
, which usually occurs abruptly when
the strain rate exceeds the ability of the rock to deform
plastically.
Bulk density
The weight of
soil per unit volume,
including all air spaces.
Buried channel
The bedrock channel of a former river
infilled now with sediment.
Buried soil
A type of fossil soil buried beneath sediment
and no longer at the surface.
Butte
An isolated,
scree
-fringed rock pinnacle in a desert
environment representing a remnant of formerly extensive
horizontally bedded rocks.
Calcicole
Plant which requires a soil containing calcium
ions and with an alkaline
pH
value.
Calcification
Formation of a horizon containing
calcium carbonate (CaCO
3
) in soil by deposition from
