The symmetrical Licancabur stratovolcano was constructed primarily during the Holocene and contains one of the world's highest lakes in its 400-m-wide summit crater. The Pleistocene Juriques volcano is located immediately to the SE and is capped by a 1.5-km-wide summit crater. Archaeological ruins were found on the crater rim of the steep-sided volcano, which maintains constant 30 degree slopes. The shallow freshwater summit lake is 90 x 70 m wide and has a measured temperature of 6 degrees C, supporting growth of planktonic fauna at nearly 6000 m elevation. Young blocky andesitic lava flows with prominent levees extend up to 6 km down the NW-to-SW flanks; older flows reach up to 15 km from the summit crater and are covered by pyroclastic-flow deposits that extend 12 km. The most recent activity produced flank lava flows.