Geology Reference
In-Depth Information
Figure 2.2
The rock cycle, the water cycle, and their interaction.
used more specifically as a synonym of
mass movement
,
which is the bulk transfer of bodies of rock debris down
slopes under the influence of gravity.
Erosion
, which is
derived from the Latin (
erodere
, to gnaw;
erosus
, eaten
away), is the sum of all destructive processes by which
weathering products are picked up (entrained) and car-
ried by transporting media - ice, water, and wind. Most
geomorphologists regard transport as an integral part of
erosion, although it could be argued, somewhat pedanti-
cally, that erosion is simply the acquisition of material by
mobile agencies and does not include transport. Water is
a widespread transporting agent, ice far less so. Moving
air may erode and carry sediments in all subaerial envi-
ronments. It is most effective where vegetation cover is
scanty or absent. Winds may carry sediments up slopes
and over large distances (see Simonson 1995). Dust-
sized particles may travel around the globe.
Denudation
,
which is derived from the Latin
denudare
, meaning 'to
regions where all its mineral characters are renewed. Thus, the
circulation of moisture through the air, is a prime mover, not only
in the annual succession of seasons, but in the great geological
cycle, by which the waste and reproduction of entire continents
is circumscribed.
(Playfair 1802, 128)
DENUDATION AND DEPOSITION
Weathering
is the decay of rocks by biological, chem-
ical, and mechanical agents with little or no transport.
It produces a mantle of rock waste. The
weathered man-
tle
may stay in place, or it may move down hillslopes,
down rivers, and down submarine slopes. This downs-
lope movement is caused by gravity and by fluid forces.
The term
mass wasting
is sometimes used to describe
all processes that lower the ground surface. It is also
