Glossary - Fundamentals of the Physical Environment - page 907

Ria A marine inlet formed by the flooding of a coastal river valley by eustatic rise in sea
level or isostatic depression.
Ridge push A component of sea-floor spreading driven by gravity-sliding away from the
elevated mid-ocean ridge .
Riegel An abraded, cross-valley rock barrier in a glaciated valley.
Riffle A stream bed accumulation of coarse alluvium linked with the scour of an
upstream pool .
Rift valley A valley formed by crustal downfaulting, normally between two parallel
faults; it gives a topographic expression to a graben .
Rill The smallest and most transient of stream channels, eroded during intermittent
surface flow and liable to collapse or infill between precipitation events.
Rip current A narrow and intermittent current, fed by longshore currents and draining
seaward through the nearshore zone, where it may be vigorous enough to cut a rip
channel in the sea bed.
Rising limb The component of a hydrograph which marks the increase in stream
discharge during the time of rise to the peak discharge , in response to a precipitation
event.
Roche moutonnée A valley-floor glaciated bedrock hump with a streamlined, abraded
uphill face inclined gently upvalley and a steep, quarried downhill face.
Rock cycle The global geological cycling of lithospheric and crustal rocks from their
igneous origins through all or any stages of alteration, deformation , resorption and
reformation.
Rock debris The initial angular fragments produced by weathering of a rock face.
Rock flour Fine debris produced by subglacial abrasion and usually flushed out as
suspended sediment in meltwater.
Rock glacier A slow-moving mass of angular rock debris with sufficient interstitial or
subjacent ice for it to flow like a glacier, usually found in arid cold climates.
Rock platform A wave-cut platform across a rock surface in the intertidal zone.
Rock weathering See weathering .
Rockfall A free fall of rock debris .
Rotor A small, overturning turbulent eddy in the air stream downwind of a mountain
range; it may generate a rotor cloud if the rising and falling limbs pass through a
condensation level.
Rubefaction Reddening of soils caused by the release of iron oxides in chemical
weathering.
Sabkha A salt-encrusted plain marked by the accumulation of evaporite rocks, usually
on tidal flats ; also used to describe an inland salt pan or playa .
Salina A general term used for a surface depression of periodic flooding and evaporation
which leads to the accumulation of evaporite rocks.
Salinity The mass of total dissolved salts present in sea water, measured in g kg −1 (‰).
Salt efflorescence A precipitation and growth of salt crystals from a fluid in rock or soil
voids.
Salt marsh A halophytic plant community occupying intertidal mudflats, exhibiting a
weak progression in diversity and productivity shorewards as the frequency of tidal
inundation falls; its surface is flooded and drained through a series of tidal creeks.