Environmental Engineering Reference
In-Depth Information
Reflected wave
A wave which has rebounded from coastal features in its path into an
incoming wave.
Refracted wave
A wave front which has been diverted from its original path as it
encounters shallow water or a coastal current.
Refugia
Isolated geographical locations whose distinctive environments permit the
survival of formerly widespread plant and animal species during periods of adverse
environmental change; they may act as centres of dispersal in any subsequent
amelioration.
Reg
A stony desert surface or
desert pavement
.
Regelation
The refreezing of supercooled water by the reduction of glacier
overburden
pressure
, or of surface meltwater which has percolated into colder ice.
Regional metamorphism
The chemical and textural alteration of rock by widespread
compression and heating or burial in, for example, a
subduction zone
.
Regolith
A general term for the superficial layer of disaggregated Earth material at the
land surface, irrespective of its specific origins.
Regression
A seaward retreat of the coastline caused by a relative fall in sea level and its
stratigraphic expression in the advance of terrestrial sedimentation.
Rejuvenation
The stimulation of denudation processes to renewed activity, normally by
the increase in potential energy caused by tectonic or isostatic uplift; also regarded as
the impetus for the first stage of a new
denudation cycle
.
Release surface
A
planar discontinuity
in Earth materials along which slope failure has
occurred; it may act singly, in the case of
planar slides
, or with other release surfaces
in more complex failure.
Relic soil
A type of fossil soil currently at the surface, and therefore showing properties
formed by past and present
soil-forming processes
.
Remnant arc
An extinct
volcanic arc
abandoned by the migration of a
subduction zone
.
Residual soil
A soil whose parent material is solid bedrock.
Resistance
The sum of forces in Earth materials mobilized to resist shearing or other
forces.
Resistant residue
Soil minerals relatively resistant to
weathering
which therefore tend to
accumulate in soils (e.g. heavy minerals, quartz, feldspars).
Resorption
The process of crustal recycling whereby oceanic and other material is
partially or completely melted in the higher temperatures and pressures of a
subduction zone
.
Respiration
The breakdown of organic compounds, using oxygen to obtain energy for
metabolic processes.
Reverse weathering
A reversal of sea-floor chemical weathering which precipitates solid
phases of minerals previously taken into solution; includes the important biochemical
precipitation of calcium carbonate and silica.
Reynolds number
A value which distinguishes between
laminar
and
turbulent
stream
flow, dependent on the relative values of
hydraulic radius
, water velocity and
viscosity.
Rheologic property
The ability of an essentially solid material to deform and flow under
stress.
Rhourd
A pyramid sand dune formed in a variable wind field.
