Rock glaciers, Entremont, Valais, Switzerland
The Entremont area is 300 square km wide and located in the western part of the Swiss Alps between the Mont-Blanc Massif and the Valaisian Alps, slightly north of the main crest of the alpine range. Altitude varies between 4313 m above see level (asl) at the top of the Grand-Combin and 714 m asl for the outlet of the valleys system. The geological composition is essentially dominated by metamorphic rocks (gneiss, shale, quartzite), however some sedimentary layers (limestone, dolomite) are inserted. The mean annual air temperature is about 0 C at 2300 m asl and annual precipitation among ranges between 1000 and 1500 mm at 2000 m asl with a maximum value of about 2000 mm on the alpine crest (Grand-St-Bernard pass). Equilibrium line of glaciers is over 3000 m asl in the north-facing slopes, the timberline is at about 2100 m asl and permafrost creeping features exist between 2000 and 3000 m asl, what results in a great variety of mountain and morphological landscapes.
Aerial photographs analyses and field morphological observations have been performed during summer 1995 in order to inventory and map (1 to 25000) 321 well-developed to embryonic rock glaciers and protalus lobes (coexisting features have been separated) of total area 10.4 square. km. Rock glacier activity classification results from interpretation of both geomorphological and environmental signs. Some geophysics (BTS measurements and DC resistivity soundings) have been performed between 1995 and 1997 on a few rock glaciers in order to confirm the initial interpretation. Data described in this file on the CAPS Version 1.0 CD-ROM, June 1998, are-- 1. Location (X, Y)-- Swiss coordinates near the center of the feature. 2. Front elevation (Z)-- Elevation (m a.s.l.) at the foot of the front (accuracy: 10 m). 3. Length-- Maximal distance (m) between front and roots (accuracy: 10 - 20%). 4. Width-- Mean width (m) of the feature (accuracy: 10%). 5. Orientation-- Global exposition of the rock glacier. 6. Activity-- Interpretation by field indicators observation, only in a few cases by geophysics. 7. Surface (ha)-- Calculated by 1 to 25,000 numerical mapping (accuracy: 5 - 10%). 8. Origin-- Talus or moraine (debris) derived rock glacier ?
Other information such as lithology, spring temperature, vegetation cover, inclination, roots elevation are partly available, but not described in the present data set.
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Delaloye, R, E. Reynard, and L.Wenker. 1998. Rock glaciers, Entremont, Valais, Switzerland. [indicate subset used]. Boulder, Colorado USA: National Snow and Ice Data Center.