Geology Reference
In-Depth Information
9.4. SLOW MASS-WASTING PROCESSES
9.4.1. Solifl uction
Solifl uction is regarded as one of the most widespread processes of soil movement in peri-
glacial environments. The term was fi rst used by J. G. Andersson (1906, p. 95) to describe
the “slow fl owing from higher to lower ground of masses of waste saturated with water”
that he observed in the cool, damp environment of the Falkland Islands. Since solifl uction,
so defi ned, is not necessarily confi ned to cold climates, the term “gelifl uction” has been
proposed to describe solifl uction associated with frozen ground (Washburn, 1979).
Intimately associated with solifl uction is frost creep. This is the ratchet-like downslope
movement of particles as the result of the frost heaving of the ground and the subsequent
settlement upon thawing, the heaving being predominantly normal to the slope and the
settling more nearly vertical (Jahn, 1975; Washburn, 1979). In the Russian literature, the
transliterated term “cryogenic deserption” is sometimes used for frost creep. When oper-
ating together, the two processes of gelifl uction and frost creep constitute the movement
that is generally termed solifl uction in the modern sense.
There are three components to solifl uction (Figure 9.7A): (i) potential frost creep
(PFC) (the horizontal component of creep following heave), (ii) the horizontal component
Figure 9.7.
The components of solifl uction. (A) Theoretical displacements of a soil particle due to
potential frost creep (PFC), gelifl uction (G), and retrograde movement (R). (B) Interpretation of
observed surface movement vector in a controlled large-scale laboratory simulation of gelifl uction
movement at CNRS, Caen, France. Data from Harris and Davies (2000).
