Post-eruption evolution of maar lakes and potential instability: The Lake Pavin case study, French Massif Central

Few studies have focused on the post-eruption evolution of maar craters and associated lake level changes, although breaching crater rim poses mass-flow flood hazards long after initial eruption. Lake Pavin is a in French Massif central formed by an eruption c. 6700 years ago. The perched edge glacially-shaped valley overlooks surrounding subdued landscape. breached to north overflow channel, south has cut into flank Montchal scoria cone lava flows. Incision outlet led growth alluvial fan that pushed Couze River towards side Gelat valley. Two terraces within are used determine stages lake. highstand Stage 1 terrace +18 m above current indicates surface volume was 15% 38% larger than present-day lake, respectively, prior 5-7th Century CE. poorly preserved 2 bench, +4.35 west natural dam, incision paused between achievement present (Stage 3) before 18th Century. Four units streamflow deposits (c. 0.087 km2 area 0.14–0.18 km3 volume) at mouth been 14C dated 9th 16th From sedimentology, we infer dropped slowly Stages 2, when down through saddle. drop accelerated 3 14th Century, inducing small debris latter may resulted from heavy rainstorms, but there no evidence for catastrophic events. Stepwise downcutting saddle also governed contrasted properties forming dam. stable since least early long-term stability dam risk.