Environmental Engineering Reference
In-Depth Information
Eustatic
Relating to global sea-level oscillation caused by absolute changes in sea-water
volume.
Eutrophication
The process of making an environment (e.g. water or soil) well supplied
with nutrients ('eutrophic') and therefore highly productive biologically.
Evaporation pan
An open water tank used to measure evaporation; sizes vary between
different countries.
Evaporite
A mineral or sedimentary rock precipitated from a saline solution as a result of
evaporation.
Evorsion
The corrosion of stream channel
potholes
by pebbles swirled around by
vortices and eddies.
Exchangeable cations
Cations which are held on exchange sites on soil colloids and
which are able to exchange with cations in the soil solution.
Exchangeable sodium percentage
(
ESP
) The percentage of the
cation exchange
capacity
occupied by exchangeable sodium ions; used as an index of soil alkalinity.
Exfoliation
Mechanical or physical weathering which proceeds by the disintegration and
removal of successive layers of rock mass.
Exogenetic
Energy derived from outside Earth. The vast majority of such energy is from
the sun.
Explosive
Extrusive igneous activity characterized by violent eruptions of
felsic
material
through volcanic vents.
Extending flow
A zone of accelerated flow within a glacier which creates tensile stress,
lateral crevassing and thinning.
Extrusive
A description of molten igneous material which erupts at Earth's surface
before cooling.
Facilitation model
A model of plant
succession
in which a habitat is modified by a
species in such a manner as to favour its replacement by other species.
Factor of safety (F
s
) A measure of the balance between shear stress and shear strength in
a slope; a state of
limiting equilibrium
exists when shearing forces equal resisting
forces in a slope and F
s
= 1.
Facultative relationships
Relationships which exist under various conditions.
Fall velocity
The specific velocity below which a moving fluid is unable to sustain a
given particle size in suspension; or the rate at which suspended particles settle
through a fluid.
Fall wind
Any wind characterized by its descent of leeward mountain slopes, irrespective
of its thermal character and origins.
Falling limb
The expression on a
hydrograph
of the subsiding
quickflow
component of
stream discharge.
Fatigue
The progressive weakening of a material through cyclic application and removal
of sub-critical stress which leads to its eventual failure.
Fault
A line or zone along which
faulting
has occurred in rock mass.
Fault breccia
Angular rock rubble lining a fault and formed by shearing and crushing of
a wider zone of rock mass bounding the fault during movement.
Faulting
The process of fracture or brittle failure of rock with displacement of adjacent
parts on either side of the
fault
.
