Based on a pilot observation, the Buenos Aires VAAC reported that the top of an ash plume from Callaqui was at 3 km (10,000 ft) a.s.l. on 2 January. Ash was not detected in satellite imagery under clear skies.

Source: Buenos Aires Volcanic Ash Advisory Center (VAAC)

Geological Summary. The late-Pleistocene to Holocene Callaqui stratovolcano has a profile of an overturned canoe, due to its construction along an 11-km-long, SW-NE fissure above a 1.2-0.3 million year old Pleistocene edifice. The ice-capped, basaltic andesite volcano contains well-preserved cones and lava flows, which have traveled up to 14 km. Small craters 100-500 m in diameter are primarily found along a fissure extending down the SW flank. Intense solfataric or fumarolic activity occurs at the southern portion of the summit; in 1966 and 1978, red glow was observed in fumarolic areas (Moreno, 1985 pers. comm.). An explosive eruption was reported in 1751 CE, there were uncertain accounts of eruptions in 1864 and 1937, and a small phreatic ash emission was noted in 1980.