Geoscience Reference
In-Depth Information
Seepage
slope
Interfluve
1
Convex
creep slope
2
3
0°-1°
model slope angles
2°-4°
Fall face
(minimum angle 45° normally over 65°)
4
Transportational midslope
(frequently occurring angles 26°-35°)
5
Colluvial
footslope
Alluvial
toeslope
Channel
wall
6
7
Channel
bed
8
9
?
0°-4°
Pedogenetic processes associated with vertical
subsurface soil water movement
Redeposition of material by mass movement and some
surface wash fan formation. Transportation of material,
creep, subsurface water action
1
6
Mechanical and chemical eluvation by lateral
subsurface water movement
2
7
Alluvial deposition, processes resulting from subsurface
water movement
3
Soil creep, terracette formation
8
Corrasion, slumping, fall
4
Fall, slide, chemical and physical
weathering
9
Transportation of material downvalley by surface water
action, periodic aggradation and corrasion
5
Transportation of material by mass movement
(flow, slide, slump, creep), terracette
formation, surface and subsurface water action
Indicates movement in a downvalley direction
Arrows indicate direction and relative intensity of
movement of weathered rock and soil materials by
dominant geomorphic processes
Source: After Dalrymple et al.(1968)
materials and so facilitating subsequent mass wasting and
erosion. Appreciation of the components and origins of
rock-mass strength is a prerequisite to understanding
how the environment mobilizes hydrothermal altera-
tion, mechanical processes and gravity to overcome rock
strength. Denudation, weathering and mass wasting
produce unstable and transient surface materials but
thereby also access to soil parent materials, nutrients and
economic mineral deposits vital to the biosphere and
human societies.
CONCLUSION
It seems scarcely appropriate to review rock destruction
so soon after its formation. Yet destruction commences as
soon as rock is elevated above sea level, or brought within
range of percolating water and air by the removal of
overlying rocks. In essence, a new set of environmental
conditions has replaced those in which the rock formed,
and its susceptibility is roughly proportional to the degree
of change. Weathering may be seen as a means to an end,
'softening up' and further reducing the strength of Earth
