DISCONTINUOUS PROCESSES IN ROCK GLACIER GENESIS AND EVOLUTION

Rock glacier is a geomorphological term proposed by Capps (1910) to define a debris body characterised by a surficial blocky cover, displaying fluidal structures. Most Authors consider rock glaciers as the main indicator of permafrost occurrence in high mountain areas. Some of them interpret the rock glacier as a continuous mass transportation system, in which the overload in the upper area is continuosly supplied by frost wedging induced scree production from the surrounding rock walls. Basing on this assumption, the measurements of creep velocity have been used to determine the age of the rock glaciers. With this paper we want to stress that rock glacier are generally made up of different kinds of deposits, related to different depositional events including also discontinous phenomena, such as rapid mass movements (e.g. rock avalanches, debris avalanches or debris flows). At least in some cases, these processes may be definitely considered as the main source for the deposition of the upper blocky layer. This latter, once deposited, may also induce changes in the thermal conditions of the ground, favouring permafrost aggradation in the underlying debris mass.