Glossary - Fundamentals of the Physical Environment - page 913

plate collisions in one area as a result of sea-floor spreading in another; also known as
the Wilson cycle (after J. T. Wilson).
Surf zone The turbulent water from breaking waves which lies between the breaker and
swash zones in the nearshore environment.
Surging glacier A glacier enjoying a transient phase of very rapid, extending and
thinning flow which exceeds the glacier's mass balance capacity and either leads to
the runaway collapse of the glacier or a quiescent period of recovery.
Suspect terrane A crustal fragment or displaced terrane among a collage of such
fragments forming continental crust, whose external and even internal common
geographical origins are in doubt, or 'suspect', by virtue of the endless mobility which
characterizes plate boundaries.
Suture The linear, convergent boundary at which two continental plates are welded
together and marked by compression structures and remnants of the ocean which
formerly separated them.
Swash A forward pulse of water released by a breaking wave after it has broken, capable
of moving sand up a beach.
Swelling clay A clay capable of absorbing very large quantities of water and greatly
increasing in volume which may contribute to mechanical weathering by creating
tensile stress in a rock mass.
Symbiotic fixation Conversion of atmospheric nitrogen into organic nitrogen compounds
by Rhizobium bacteria living in nodules on the roots of leguminous plants.
Syndepositional sedimentary structure A structure formed during the final settlement
of a soft sediment, reflecting, for example, slumping or faulting on contraction as
water is expelled, or flowage of more saturated components.
Synecology The ecology of organisms living as a community.
Syngenesis Minor, non-destructive changes in the mechanical or chemical properties of
rock during its emplacement, which act as early stages in its lithification .
System A network of variables (objects, phenomena or components) which are linked by
relationships and which interact to behave as a unified whole.
Systems analysis The study of systems , for example hydrological systems, atmospheric
systems and ecosystems in physical geography.
Talik A pocket of unfrozen ground, other than the active layer , within the boundary of an
otherwise frozen permafrost environment.
Talus An alternative name for scree .
Talus cone A cone of coarse, angular rock debris or scree accumulated at the base of a
rock chute .
Tectonic cycle Cycle of ocean and continental expansion and contraction, synonymous
with a supercontinental or Wilson cycle .
Temperate glacier A warm-based glacier, at or near pressure-melting point throughout
and generally typical of alpine valley glaciers or the lower portions of outlet glaciers .
Temperate stage A period of Earth history marked by the expansion of mid-latitude
temperate belts at the expense of cold climates and ice sheets. Equivalent to the term
'interglacial' in the Quaternary period, when they occur as brief ( c . 10 kyr) interludes
between more prolonged ( c . 100 kyr) cold stages .
Tensile stress A stress tending to stretch, pull apart and fracture rock mass.