SURFACE MOVEMENT AND LICHEN-COVER STUDIES AT THE ACTIVE ROCK GLACIER NEAR THE GRUBENGLETSCHER, WALLIS, SWISS-ALPS

The stress field within the rock glacier must have been changed during the Neoglacial advances of the Grubengletscher at its southern margin. The interaction of permafrost and ground-water is important for the behavior of the rock glacier as well as for the evolution of marginal glacier lakes in similar cases. The ecological conditions for the growth of lichens at the rock-glacier surface vary extremely in space and time. Lecidea promiscens occurs most frequently and in all exposures. Rhizocarpon geographicum and Sporastatia testudinea lichens generally are very rare and even absent within the limits of the 1850 advance of the Grubengletscher. The maximum snow-cover duration that still allows lichen growth may be of the order of 46 weeks per year for Lecidea promiscens and 40 weeks for Rhizocarpon geographicum.-from Authors