Glossary - Fundamentals of the Physical Environment - page 909

Seif dune A large, sinuous linear dune drawn out parallel to the wind direction.
Seismic activity The sudden release of accumulated stress in rocks subjected to tectonic
and other deformation and the Earth shock waves or earthquakes which it propagates.
Seismic sea wave A travelling ocean surface wave caused by seismovolcanic activity
which grows in height as it enters shallow coastal waters and frequently causes
damage and loss of life; often mistakenly confused with a tidal wave .
Seismovolcanic The close association between volcanic and earthquake activity whereby
either may trigger the other, and their mutual concentration at plate boundaries.
Sensible heat The heat we can feel and measure with a thermometer.
Sensitive clay A clay whose undisturbed strength is four to eight times greater than its
disturbed strength and is therefore particularly prone to failure.
Sequestration Literally meaning the process of 'isolating' or 'confiscating', and used in
climate change science of the processes, in the global carbon cycle, whereby carbon is
'locked up' in soils, vegetation and sedimentary carbonates.
Seral stage A stage in a sere when the area is occupied by a community which creates
conditions more and more favourable for a succeeding community.
Sere An alternative term for succession .
Set - down The local, minor fall in water level experienced in the surf zone when edge
waves and incoming waves are out of phase.
Set - up The local, minor rise in water level experienced in the surf zone when edge waves
and incoming waves coincide.
Severn bore The bore which marks the leading edge of incoming tides at the head of the
Bristol Channel, Britain's largest marine inlet experiencing one of Earth's highest tidal
ranges.
Shape of soil structure The morphology of the individual peds which make up the soil
structure.
Shear strength The sum of internal forces in a rock or soil capable of resisting shear
which determines the maximum shear stress the material can endure without failing.
Shear stress The tangential stress which acts on a unit of Earth material and may lead to
shearing.
Sheet flow Surface water flowing as a thin, continuous film rather than concentrated in a
channel.
Sheeting structure A fracture or other planar discontinuity formed or exhumed in rock
mass by the removal of overlying material accompanied by elastic strain release .
Shield The crystalline or high-grade metamorphic core of stable continental crust or
craton .
Shoaling The alteration of wave height, form and velocity through sea-bed friction as it
enters shallow water, transforming it into a breaking wave .
Shoaling wave An incoming wave experiencing sea-bed effects or shoaling .
Shore - normal Moving at right-angles to the shore, i.e. directly landwards or seawards.
Short - wave radiation The radiant energy emitted by the sun at wavelengths below 3
µm.
Sichelwanne A crescent-shaped scar on a glaciated bedrock surface marking the removal
of a flake by an abrading rock or by high-pressure meltwater.
Sierra A high mountain range or cordillera characterized by jagged, saw-tooth peaks.