Report on Lascar (Chile) — April 1988
Scientific Event Alert Network Bulletin, vol. 13, no. 4 (April 1988)
Managing Editor: Lindsay McClelland.
Lascar (Chile) Continuing minor ash emission
Please cite this report as:
Global Volcanism Program, 1988. Report on Lascar (Chile) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 13:4. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198804-355100.
23.37°S, 67.73°W; summit elev. 5592 m
All times are local (unless otherwise noted)
During intermittent observations by geologists 11-30 March, ash emission was semi-continuous. Some periods of stronger activity were noted. On 11 March at about 0930, an ash-laden plume rose ~1,500 m above the active crater. Plumes reached 2,500-3,000 m above the volcano between 0700 and 1030 on 18 March; individual emissions lasting ~1 minute occurred every 3-5 minutes. The volcano generally appeared more active during the morning and low-level emissions were most noticeable before noon, a pattern assumed by the observers to be related to daily cycles of atmospheric conditions. No recent ash deposits were found. There were no signs of renewed magmatic activity, and the geologists suggested that the low-level explosions were probably due to slumping of crater walls into the conduit, with the resulting blockage being occasionally cleared after slight accumulation of gas pressure.
Geologists 32.5 km NW of Lascar (at the MINSAL Co. in Toconao) reported that similar activity had continued for several months. Between more active periods, steam and fume could usually be seen rising above the crater.
Geologic Background. Láscar is the most active volcano of the northern Chilean Andes. The andesitic-to-dacitic stratovolcano contains six overlapping summit craters. Prominent lava flows descend its NW flanks. An older, higher stratovolcano 5 km E, Volcán Aguas Calientes, displays a well-developed summit crater and a probable Holocene lava flow near its summit (de Silva and Francis, 1991). Láscar consists of two major edifices; activity began at the eastern volcano and then shifted to the western cone. The largest eruption took place about 26,500 years ago, and following the eruption of the Tumbres scoria flow about 9000 years ago, activity shifted back to the eastern edifice, where three overlapping craters were formed. Frequent small-to-moderate explosive eruptions have been recorded since the mid-19th century, along with periodic larger eruptions that produced ashfall hundreds of kilometers away. The largest historical eruption took place in 1993, producing pyroclastic flows to 8.5 km NW of the summit and ashfall in Buenos Aires.
Information Contacts: M. Gardeweg and C. Ramirez, SERNAGEOMIN, Santiago; P. Francis and S. De Silva, Lunar and Planetary Institute, Houston; S. Self, Univ of Texas, Arlington, TX.