Glossary - Fundamentals of the Physical Environment - page 876

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 landwards 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.
Calcification The accumulation of calcium carbonate in soil horizons.
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.