Copahue

Copahue is a stratovolcano in the Andes on the border of Bío Bío Region, Chile and Neuquén Province, Argentina. There are nine volcanic craters along a 2 km (1.2 mi) line, the easternmost of which is historically the most active, and contains a 300 m (1000 ft) wide crater lake with a pH ranging between 0.18 and 0.30. Eruptions from this crater lake have ejected pyroclastic rocks and chilled liquid... (Wikipedia)