Steam plumes rise from abundant solfataras lining the shores of the acid crater lake
where the eruptive activity took place at Tupungatito during the 1960s.
Photo by Alejo Contreras (courtesy of Oscar González-Ferrán, University of Chile).

Tupungato, one of the highest mountains in South America, 6.570 m asl, is a massive stratovolcano dating to
Pleistocene times. It lies on the border between the Chilean Metropolitan Region and the province of Mendoza,
Argentina, near a major international highway about 80 km (50 mi) east of Santiago, Chile.

It is located about 100 km (62 mi) south of Monte Aconcagua, the highest peak of the American continent.
Immediately to its southwest lies the active Tupungatito volcano, which last erupted in 1987.

12/1987 Increased summit thermal activity, small ash eruption in January 1986

On 29 November 1987, an avalanche in the Estero del Parraguirre, a stream in a small valley 20 km NW of Tupungatito,
generated a mudflow that killed 41 people and caused major damage along the valley of the Río Colorado,
which pases through Chile's capital, Santiago. Initial reports suggested a possible linkage with increased activity at
Tupungatito, a linkage that was disputed by other geologists.

Reactivation of one of the NW craters with a weak emission of black ash occurred 20 January 1986 at 1030.
The activity was observed by the pilot of a Chilean Air Force C-130 and reported directly by radio-telephone.
The volcano had been under observation since the last pyroclastic eruption occurred 10 January 1980
. After the M 7.8 earthquake that affected the Santiago region on 3 March 1985, vertical aerial photographic
coverage was carried out at a scale of 1:20,000 on 25 March 1985.

No increased activity was observed within the caldera, which has a diameter of ~5 km and is covered with ice and snow. Glaciers descend from it toward the W. The group of cones and craters with historic activity, in the extreme NW
of the caldera, have only a thin covering of snow. Observations on 24 November 1987 show ice partially covered
by 20 January 1986 ash, and intense solfataric activity in the same crater.

On 4 December, new aerial photographic coverage of the Tupungatito volcanic region was taken by the Air Force Aerophotogrammetric Service at the request of the author and the National Emergency Office.

Analysis of the airphotos revealed a notable increase in snowmelt inside Tupungatito's active craters and an important
increase in fumarolic activity without showing a direct relation with the 29 November lahar.

The volcano remains under observation. If it produced an eruptive reactivation of some magnitude it could: affect
the glacier covering the caldera; cause lahars larger than the one that occurred 29 November; and seriously damage
the S sector of Santiago, Chile and Mendoza, Argentina."