Environmental Engineering Reference
In-Depth Information
Figure 13.3
Global morphogenetic regions, based on
morphoclimatic zones.
Source: After Tricart and Cailleux (1972).
applied to rock mass originate
internally
through volumetric changes associated with
heating, cooling, chemical reactions and the circulation of fluids (including air). They
determine
rock weathering
processes. Forces are also applied
externally
, through the
emplacement and/or removal of static (
in situ
) or dynamic (moving) loads of rock,
sediment, water, ice, wind or anthropogenic structures. This is the essence of erosion. The
latter include tectonic forces whose effects are represented by elastic strain, released in
earthquakes, deformation structures and continuing rock deformation. Resistance can be
measured as hardness, resisting
abrasion
, or as the sum of internal strength properties
capable of resisting
tensile stress
(pull apart),
compressive stress
(crushing) and
shear
stress
(sliding rupture) (Figure 13.4). Abrasion occurs when one rock scratches another
of lower hardness. It is a minor process in slope and glacial environments (
striation
) and
in-transit sediments, where
attrition
polishes grains jostled together. Some forms of
weathering establish internal tensile stress where individual minerals expand.
