Impacts géomorphologiques des chutes de blocs de glace sur les versants du nord de la Gaspésie (Québec, Canada).

The displacement of surface material, caused by the spring collapse of rockwall icings that had formed on some rock faces during the winter, was quantified on three detrital talus slopes in Northern Gaspésie. The volumes of ice accumulated on the cliffs vary between 1000 and 4000 m3. One of the collapses triggered an avalanche of snow loaded with ice blocks. The avalanche reached a distance of more than 250 m from the rock face and the volume of the deposit, essentially ice (>80%) and snow, was estimated at 5000 m3. The debris displaced by the ice blocks at the surface of the talus was monitored using 297 passive integrated transponders (PIT tags) glued onto pebbles. Iron rods were inserted under the surface of the talus to measure erosion and accumulation on the talus surface. Mean displacements of 21 m were observed, and a maximum displacement of 232 m was measured at one of the sites. In general, erosion was observed over almost the entire length of the talus except at the base of the slopes where significant accumulations were recorded. The sediment displacement pattern concords with the ice block displacement mode on the slopes. Even if it was not possible to isolate the impact from all the active processes on the study slopes, it was evident that the collapse of the ice crusts is the dominant geomorphological process on the slopes studied. [Journal translation] [ABSTRACT FROM AUTHOR]