A glacial lake outburst flood associated with recent mountain glacier retreat, Patagonian Andes

Geomorphological mapping, sedimentology, lichenometry and dendrochronology were used to assess the nature and timing of glacier recession, moraine development and catastrophic mass movements in a tributary of the Leones valley, east of the Hielo Patagonico Norte, Chile. We show that during the 'Little Ice Age' Glaciar Calafate advanced downvalley to produce a terminal moraine. Recession of the glacier from this position occurred in the 1870s and produced a moraine dammed lake. In late 2000 a large rockfall into the lake breached the moraine and triggered a glacial lake outburst flood ( GLOF) that entrained and subsequently deposited some 2 x 10(6) m(3) of material. We interpret this event as a delayed paraglacial response to the retreat of Glaciar Calafate during the twentieth century.