Environmental Engineering Reference
In-Depth Information
Duricrust
A hard, crystalline crust found on tropical land surfaces formed by
evaporite
minerals brought there in solution by
capillary
action from underlying soil and rock.
Dyke
A columnar igneous
intrusion
which cuts discordantly through existing rock
structures.
Dynamic equilibrium
A form of self-regulation in a system which maintains a similar
type of system.
Dynamic viscosity
The resistance to flow of a fluid.
Eccentricity of the orbit
The changing shape of Earth's orbit around the sun from a
more circular to a more elliptical path. It varies over a cycle of almost 100,000 years.
Ecological amplitude
The overall range in which an organism can function; the sum
total of all individual tolerance ranges for a particular species.
Ecological niche
The position of an individual species within an ecosystem, in terms of
function, space and time.
Ecological optimum
That part of the range of a plant species where the plant's vigour is
greatest.
Ecological status
The position of a
plant community
within the hierarchy of seral and
climax communities.
Ecosphere
The biologically inhabited part of the Earth, oceans and atmosphere.
Ecosystem
Open system comprising plants, animals and their environments which is
involved in the flow of energy and the circulation of matter.
Ecosystem stability
The behaviour of the entire system in response to an external
perturbation; can be defined by several indicators, including resistance and resilience.
Ecotone
A zone of transition, and hence competition, between two contiguous
plant
communities
.
Edaphic climax
Climax vegetation maintained by soil conditions (e.g. wetness,
chemistry).
Eddy diffusion
The mixing of atmospheric matter and properties which is brought about
by eddies.
Eddy viscosity
The resistance to flow of a fluid caused by friction between individual
strands of the flow.
Edge wave
A wave moving approximately at right-angles to the shore and breaking
waves, as a result of the need to drain water being pushed onshore which cannot easily
escape through the
swash
.
Eemian stage
The penultimate global
temperate stage
, known as the Ipswichian in
Britain and as the Sangamon in North America, extending from
c
. 135, 000 to 115,000
years BP.
Effusive
Extrusive igneous activity characterized by a steady outflow of basaltic material
from a fissure (cf.
explosive
).
El Niño
The appearance of unusually warm water off the South American Pacific coast
when the westward-driven equatorial ocean current periodically falters, owing to a
reduction in trade-wind strength in the equatorial Pacific Ocean. This, in turn,
suppresses
upwelling
cold, deep water induced by these atmospheric and ocean
currents; ocean-atmosphere coupling further disturbs pressure and precipitation
systems throughout the region (the 'Southern Oscillation'). The effect occurs every
few years, commencing around Christmas time - hence its Hispanic allusion to the
Christ child.
