Page 54 - Fundamentals of Geomorphology

THE GEOMORPHIC SYSTEM 37

Figure 2.2 The rock cycle, the water cycle, and their interaction.

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