190
Climatic Geomorphology
Figure 8.20. Rock glaciers. Clot de Claror, Aranser Valley, Eastern Pyrenees. Photo: A. G6mez-Ortiz.
than 1, and the spatulate rock glaciers similar to the lobate rock glaciers with a broader
lower part (Wahrhaftig and Cox, 1959; Barsch, 1996) (Figure 8.22). The complex rock
glaciers are those formed by the aggregation of several individual rock glaciers
(Washburn, 1979; Barsch, 1996).
The width of the majority of rock glaciers range between 100 and 500 m and the length
may exceed 1 km. Regarding the texture of the detrital material, the rock glaciers are formed
by a 2 to 5 m thick upper bouldery layer underlain by a fine-grained ice supersaturated sandy
and silty material (Barsch, 1996). The total thickness may reach more than 50 m. Rock
glaciers show steep fronts, with inclinations between 35 and 45 ~ (Barsch, 1988). The side
slopes are also steep and the upper bouldery surface has a microrelief of ridges and furrows
which are bent downvalley (Figure 8.20 and Figure 8.23). The volume transported in a rock
glacier generally exceeds one million cubic meters, 40 to 50% correspond to detrital
material and the 50 to 60% to interstitial ice and ice lenses. The displacement of the rock
glaciers results from the plastic or creep deformation of the ice and is largely controlled
by factors like the slope, ice content, temperature, or grain size of the inner clasts. The
velocity of active rock glaciers, commonly higher in summer than in winter, varies from
a few centimetres per year (Barsch and Hell, 1975) (Figure 8.24) to 5 m/yr. The highest
values have been measured in the Obergurl rock glacier (Austrian Alps) at abrupt
changes in slope. The movement of the rock glaciers is quicker than in the glaciers and
slower than in the slope deposits affected by gelifluction.
Discharge of active rock glaciers is controlled by strong seasonal and diurnal
variations. Snowmelt water and summer storms water are released in a very rapid way,
provoking flooding events. The discharge of glaciers is very similar to that one of active
Climatic Geomorphology
Figure 8.20. Rock glaciers. Clot de Claror, Aranser Valley, Eastern Pyrenees. Photo: A. G6mez-Ortiz.
than 1, and the spatulate rock glaciers similar to the lobate rock glaciers with a broader
lower part (Wahrhaftig and Cox, 1959; Barsch, 1996) (Figure 8.22). The complex rock
glaciers are those formed by the aggregation of several individual rock glaciers
(Washburn, 1979; Barsch, 1996).
The width of the majority of rock glaciers range between 100 and 500 m and the length
may exceed 1 km. Regarding the texture of the detrital material, the rock glaciers are formed
by a 2 to 5 m thick upper bouldery layer underlain by a fine-grained ice supersaturated sandy
and silty material (Barsch, 1996). The total thickness may reach more than 50 m. Rock
glaciers show steep fronts, with inclinations between 35 and 45 ~ (Barsch, 1988). The side
slopes are also steep and the upper bouldery surface has a microrelief of ridges and furrows
which are bent downvalley (Figure 8.20 and Figure 8.23). The volume transported in a rock
glacier generally exceeds one million cubic meters, 40 to 50% correspond to detrital
material and the 50 to 60% to interstitial ice and ice lenses. The displacement of the rock
glaciers results from the plastic or creep deformation of the ice and is largely controlled
by factors like the slope, ice content, temperature, or grain size of the inner clasts. The
velocity of active rock glaciers, commonly higher in summer than in winter, varies from
a few centimetres per year (Barsch and Hell, 1975) (Figure 8.24) to 5 m/yr. The highest
values have been measured in the Obergurl rock glacier (Austrian Alps) at abrupt
changes in slope. The movement of the rock glaciers is quicker than in the glaciers and
slower than in the slope deposits affected by gelifluction.
Discharge of active rock glaciers is controlled by strong seasonal and diurnal
variations. Snowmelt water and summer storms water are released in a very rapid way,
provoking flooding events. The discharge of glaciers is very similar to that one of active