Environmental Engineering Reference
In-Depth Information
Glossary
A-subduction
See
Ampferer subduction
.
Abandoned meander core
Ground encircled by the course of a former river meander but
now isolated by cut-off across the meander neck by subsequent channel straightening;
the core may be a substantial hill in an incised valley.
Ablation till
A supraglacial coarse-grained sediment or
till
, accumulating as the
subjacent ice melts and drains away and finally let down on to the exhumed subglacial
surface.
Abnormal soils
A class of soils in Dokuchaiev's classification denoting young or
azonal
soils, e.g. peat, alluvial soils, raw sands.
Abrasion
Mechanical wear and tear brought about by the movement of harder rock
fragments, ice pellets or organic debris against softer rocks or rock fragments.
Absolute zero
The temperature at which atoms and molecules possess the minimum
amount of energy and no thermal motion. It corresponds to −273·15° on the Celsius
scale.
Absorption
The conversion of
radiation
to another form of energy.
Abyssal plain
The profound, almost level, largest single component of the deep ocean,
lying 4-6 km deep between mid-ocean ridges and trenches.
Accretionary prism
A wedge-shaped rock mass of sediment and
ophiolite
transferred
during subduction from descending oceanic plate to the adjacent continental plate.
Acid
A substance capable of liberating hydrogen ions in water, measured by a
pH
of less
than 7·0; acids have corrosive properties and are important agents of
rock weathering
.
Active layer
The superficial layer of a
permafrost
land surface which experiences
seasonal melt and refreezing and is, consequently, the site and cause of considerable
ground disturbance.
Actual evapotranspiration
The amount of moisture evaporated from the ground surface
and transpired by plants into the atmosphere.
Adrèt
A mountain slope whose orientation maximizes the receipt of sunlight.
Adsorption
The accumulation of ions at the surfaces of clay minerals and humic colloids
in soils.
Aeolian
Said of the processes, Earth materials and landforms involving the role of the
wind.
Aerenchyma
Air-filled spaces in the roots and stems of hydrophytic plants.
Aggradation
A rise in ground level caused by the accumulation of sediments.
Aggregates
Soil structural units of various shapes, composed of mineral and organic
material; formed by natural processes, and having a range of stabilities.
Aiguille
A steep, frost-shattered rock pinnacle.
