MONITORING OF PERIGLACIAL SLOPE PROCESSES IN THE SWISS ALPS - THE FIRST 2 YEARS OF FROST SHATTERING, HEAVE AND CREEP

A synthetic monitoring system was developed in an attempt to evaluate geomorphic processes acting on periglacial rock and debris slopes in t he Swiss Alps. The measured parameters include rock joint widening, so il heave and creep, and associated variables. Data loggers provide yea r-round records of these parameters. Observations for the first two ye ars highlight rock weathering and soil movement caused by frost action . Rock temperature data demonstrate that the southern exposures and no rth-facing ridges experience multiple diurnal freeze-thaw cycles, whil e north-facing rockwalls are dominated by the seasonal freeze-thaw act ion. This contrast may account for the spatial variability in the size of rock debris released from rockwalls. Considerable amounts of joint widening were recorded at the onset of seasonal thawing, when meltwat er percolated downward into the frozen bedrock. This observation empha sizes that moisture availability controls to a large degree the magnit ude of frost action. Diurnal frost heave and creep prevail on crest de bris slopes, while basal debris slopes experience large frost heave du ring seasonal freezing and thawing. Such a variation in the type of so il movement corresponds to the landform transition from small sorted s tripes that predominate on the crest slopes to solifluction lobes on t he basal slopes. (C) 1997 by John Wiley & Sons, Ltd.