Rock glacier, push-moraine, historical glacier forefield
Elevation : 2640-2900m - Massif: Valais Alps (Sasseneire-Tsaté) - Commune: Anniviers (VS)
As a part of the periglacial landscape of the Réchy Valley – Pas de Lona (Swiss Geotope n°216, VS) the body of unconsolidated sediments of Lona can be considered as a vast push moraine morphologically resembling a rock glacier, which owes its existence to the advance of the former Sasseneire glacier during the Little Ice Age. Only the edges of the zone formerly covered by the glacier are subject to permafrost conditions and contain ice, even in places remains of glacier ice covered by debris. First researches in periglacial geomorphology at this site were performed at the end of the 1980s (thesis of Emmanuel Gerber). Subsequently, some measurements (geophysical, thermal, geodetic) were undertaken from time to time, all of which showing a more or less pronounced tendency of permafrost degradation over the last decades.
Measurements and observations
Thermal (soil surface temperature : BTS)
Geophysics (electrical resistivity, refraction seismic)
Presence/Absence of permafrost (locally debris-covered glacier) based on electrical resistivity measurements (data: 1990, 2002).
Measured horizontal flow field (mean annual velocity).
Delaloye, R. (2004). Contribution à l’étude du pergélisol de montagne en zone marginale. PhD thesis, Fac. Sciences, Univ. Fribourg, GeoFocus 10 (pdf)
Delaloye, R., Lambiel, C., Reynard E. & Lugon R. (2003). Réponse du pergélisol à l’avancée glaciaire du petit âge glaciaire : quelques exemples alpins et pyrénéens. Environnements Périglaciaires 10.
Delaloye, R., Métrailler, S. & Lugon, R. (2003). Evolution du pergélisol dans les complexes glaciers/glaciers rocheux des Becs-de-Bosson et de Lona (Nax, St-Martin, VS). Bulletin de la Murithienne, 2003, no.121, p.7-20