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 Patago´nico 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 /106 m3 of material. We interpret this event as a delayed paraglacial response to the retreat of Glaciar Calafate during the twentieth century.