Geology Reference
In-Depth Information
Table 3.2 Mass movements and fluid movements
Main mechanism Water content
Very low Low
Moderate
High
Very high
Extremely high
Creep
Rock creep
Continuous creep
Flow
Dry flow Slow earthflow
Solifluction
Rapid
earthflow
Mudflow
Debris avalanche
(struzstrom)
Gelifluction
Rainwash
Slush
avalanche
Snow avalanche
(slab avalanche)
Debris flow Sheet wash
Ice flow
Sluff (small, loose
snow avalanche)
Rill wash
River flow
Lake currents
Slide
(translational)
Debris slide
Debris slide
Rapids (in part)
Earth slide
Earth slide
Ice sliding
Debris block slide
Debris block slide
Earth block slide
Earth block slide
Rockslide
Rock block slide
Slide
(rotational)
Rock slump
Debris slump
Earth slump
Heave
Soil creep
Talus creep
Fall
Rock fall
Waterfall
Debris fall (topple)
Ice fall
Earth fall (topple)
Subsidence
Cavity collapse
Settlement
Source:
From Huggett (1997b, 196), partly adapted from Varnes (1978)
3
Slides
are a widespread form of mass movement.
They take place along clear-cut shear planes and
are usually ten times longer than they are wide.
Two subtypes are translational slides and rotational
slides.
Translational slides
occur along planar shear
planes and include debris slides, earth slides, earth
block slides, rock slides, and rock block slides
(Figure 3.6b).
Rotational slides
, also called
slumps
,
occur along concave shear planes, normally under
conditions of low to moderate water content, and are
commonest on thick, uniform materials such as clays
(Figure 3.6c; Plate 3.1). They include rock slumps,
debris slumps, and earth slumps.
4
Heave
is produced by alternating phases of expan-
sion and contraction caused by heating and cooling,
wetting and drying, and by the burrowing activities
of animals. Material moves downslope during the
cycles because expansion lifts material at right-angles
to the slope but contraction drops it nearly vertically
under the influence of gravity. Heave is classed as
soil
