Lake Epulafquén, long, is the southern arm of the lake. A complex of volcanoes, the Huanquihue Group, in elevation, rise above its southern shore. About 1800 CE, a lava flow from one of the volcanic cones reached the southern shore of the lake causing a rocky, distorted delta. A short, turbulent stream brings the waters of two additional lakes, Lake Curruhué, long, and Green Lake, long, into Lake Epulafquén. Another short stream feeds into Lake Epulafquén from Lake Carilafquén, long. Hot springs and thermal baths are located near the shores of this lake.