Located at ~54°S in the Island of Tierra del Fuego, Argentina/Chile, Lago Fagnano is the biggest (~110 km long), southernmost non-ice covered lake in the world outside Antarctica. In addition to its tectonic origin, the lake evolved under the reach of past Andean glaciations. Therefore, its sediments contain a unique record of past tectonic and climatic events. The combination of seismic reflection profiling and detailed analyses of long sedimentary cores allowed to address questions regarding past regional environmental changes. The geophysical data from the lacustrine basin with existing geomorphological data around the lake allowed identifying and assigning a seismic sequence to subaquatic moraines within Lago Fagnano. The laminated sequences are occasionally interrupted by homogenous beds several tens of cm thick interpreted as resulting from simultaneously-triggered basin-wide lateral slope failures and thus, fingerprinting paleo-seismicity along the MFT fault zone. Their temporal distribution revealed an 800-1000 years recurrence of slope failure providing unique data about the frequency and plausible magnitude of Holocene earthquakes in Tierra del Fuego.