[2] Eruptions from this crater lake have ejected pyroclastic rocks and chilled liquid sulfur fragments.

[3] Copahue sits on a basement of sedimentary and volcanic rocks ranging in age from Eocene to Pliocene.

The modern volcano became active roughly 1.2 million years ago (Ma).

[2] The modern caldera formed 0.6 to 0.4 Ma, and produced large pyroclastic flows, extending up to 37 km from the volcano.

[1][3][4] On 27 May 2013, it was reported that a red alert had been issued and the evacuation of around 2,000 people was to begin.