Glossary - Fundamentals of the Physical Environment - page 908

Salt weathering The granular disintegration of rock caused by salt efflorescence which
acts as an important mechanical weathering agent through its generation of high
tensile stress.
Saltation The movement of sediment particles by turbulent entrainment in water, wind or
by grain ballistics , followed by short jumps or bounces along the bed.
Sand wave A large wave- or dune-like sand bed form formed by fluid motion normal to
its axis.
Sandur An outwash plain forming the superficial land surface in piedmont or coastal
zones beyond glacier margins.
Saprolite A soft in situ residue of chemically decomposed rock.
Saturated overland flow Surface water discharge in sheet rather than channel form,
generated where the soil water table breaks the land surface.
Scattering The process whereby radiation is dispersed in all directions by particles. The
particles can be from the size of molecules upwards. Meteorologically, radiation
which has been scattered is known as diffuse radiation.
Schistosity A rock texture in coarse-grained material with close, sub-parallel planes
formed by the arrangement of platy minerals; a rather coarser form of cleavage .
Scree Angular rock debris or talus which accumulates on slopes below the rock wall
from which it was weathered; it may be partially gravity-sorted and maintains a slope
angle dependent on its friction strength.
Sea - floor spreading The lateral spread of the sea floor generated by mantle convection
and consequential formation of new ocean crust at a mid-ocean ridge; the driving
mechanism of plate tectonics .
Sea ice Floating ice formed by the freezing of sea water; not to be confused with floating
glacier ice.
Sea level The mean surface elevation of the sea, normally excluding transient changes
induced by tides, atmospheric pressure, upwelling and water influx.
Seamount A wholly submerged, submarine mountain; many are former sea-floor
volcanoes.
Secondary ( S ) wave A slower-moving earthquake wave which oscillates at right-angles
to its direction of travel and can only pass through rock (see also primary wave ).
Second - stage community A community occupying the second stage of a succession .
Sediment balance The volumetric input, storage and output of sediment which
constitutes the sediment budget of a drainage basin per unit of time, usually a calendar
year.
Sedimentary The description of a major group of both unconsolidated and lithified rocks
formed by the eventual accumulation of rock and organic debris after a period of
transport, suspension or solution.
Sedimentary basin A geographical area in which sediments accumulate, generally in the
form of a continental or marine depression which acts as a gravitational 'sump'.
Sedimentary environment A general location in which groups of genetically related
sedimentary facies are deposited, such as a fluvial or marine environment.
Sedimentary facies A parcel of sediment with distinct internal characteristics reflecting a
particular depositional event or location within a broader sedimentary environment .
Segregated ice lens A type of ground ice formed by the migration of pore water to a
freezing plane and displacing unconsolidated soil particles to form a discrete ice lens.