Grunder's field assistant, Maximino Burotto Huerta, said he had seen similar behavior on 1 September. Ordinarily, either a white wisp of steam or nothing is seen emanating from the peak. Grunder was in the area for 31 days between 24 August and 5 December 1995, though typically not in sight of the volcano. She observed no plumes on 27 November and 1-5 December 1995. These observations suggested that the activity consisted of modest phreatic eruptions.
Available literature lacks clear documentation of any historical Irruputuncu eruptions.
Irruputuncu sits within the collapse scarp related to a Holocene debris avalanche. There are two summit craters, the southernmost of which has been fumarolically active.