geographia - Studia

O. POP, J. - C. THOURET, V. SURDEANU
The end of the glacial morphologic system has brought changes in the erosion
processes. During the Holocene period it seems that the landsliding was one of the major
geomorphologic processes in Sancy. In this study, we have focused on the morphologic and
morphometric analysis of three of the most important landslides that affected the slopes of
the ancient glacial valleys.
Fig. 1. Localization of the Sancy stratovolcano.
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2. GEOMORPHOLOGICAL SETTING
In the studied area (fig 2), the landslides affect Pliocene-Quaternary trachyandesite
lava flows, tuffites, pyroclastic, hydroclastic, moraine and periglacial deposits, overlapping a
fractured Hercynian granitic basement. The glacial activity left traces that are still
present: cirques, moraine deposits, steep slopes in some areas of the glacial valleys.
In the eastern glacial valley of Sancy (Vallée de Chaudefour), two lakes have been
formed after the retreat of glaciers as a result of the two landslides produced at different
times during the Holocene. The ages of these two landslides were obtained by Macaire et
al. (1992) using C 14 method:
a) the Montagne de la Plate landslide (8.29 ka B.P.) has determined a dam effect
and the formation of a lake, now filled by sediments (fig. 4);