Puyehue Lake is an Andean piedmont lake located in the border of Los Lagos Region with Los Ríos Region of Chile. Puyehue is a lake of glacial origins, several times during the pleistocene glaciations the lake depression was occupyed by a large glacier lobe of the Patagonian Ice Sheet forming thus a series of moraines along its western shores. The lake have an east-west elongated shapewith Fresia Island in the middle and two minor peninsulas pointing toward the island, one from the north and one from the south. The lake have remarkbly smooth coastes with only one inlet of significance; the Futacullín Bay on the south.
As most other lakes of southern Chile Pueyehue Lake acts as a sediment trap for material from the Andes. Sediment cores taken from Puyehue Lake in 2001 and 2002 have been intrepreted as supporting the existence of the Little Ice Age in the Southern Hemisphere .