Report on Villarrica (Chile) — August 1997
Bulletin of the Global Volcanism Network, vol. 22, no. 8 (August 1997)
Managing Editor: Richard Wunderman.
Villarrica (Chile) Explosions during March-June; crater glow in August
Please cite this report as:
Global Volcanism Program, 1997. Report on Villarrica (Chile). In: Wunderman, R. (ed.), Bulletin of the Global Volcanism Network, 22:8. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199708-357120.
39.42°S, 71.93°W; summit elev. 2847 m
All times are local (unless otherwise noted)
As reported by volcano guides on 17 February, two vents on the NE side of the crater floor had small Strombolian eruptions and extruded incandescent lava onto the crater floor (BGVN 22:04). On 24 February the guides reported that the crater floor had risen by several meters. Residents of Pucon (~17 km N) noted night glow on 2 March following several months of absence. Weak Strombolian explosions continued throughout the remainder of March.
The following describes visual observations made from April through August 1997 by members of the Villarrica Observation Project/Internet (POI) from Pucon. Table 2 presents observations since mid-October 1996.
|Date||Description of Activity|
|Mid-Oct to mid-Nov 1996||Notable rise of the magma column in the central crater pit.|
|Late Nov 1996||Subsidence of the magmatic column.|
|Dec 1996-03 Jan 1997||Strong vapor emissions.|
|04 Jan 1997||Inner crater pit completely visible without incandescent lava.|
|15-19 Jan 1997||Strong fumarolic activity.|
|21 Jan 1997||Two small ash emissions from the summit crater.|
|17-24 Feb 1997||Small Strombolian eruptions from two crater vents. Lava fountains actively filling the crater, raising the crater floor by several meters. Convection within the lava pond.|
|02 Mar 1997||Reappearance of night glow above the crater.|
|12 Mar 1997||Light dusting of ash seen on the snow-covered NE flank.|
|15 Mar-Apr 1997||Strombolian explosions from a crater vent.|
|Mid-May 1997||Incandescent bombs ejected over the crater.|
|22-31 May 1997||Small ash puffs from the summit crater.|
|June 1997||Small Strombolian explosions.|
|10 Jul 1997||Nocturnal red glow disappeared.|
|17-19 Jul 1997||No sign of fumarolic activity.|
|22 Jul 1997||Reappearance of weak fumarolic activity.|
|31 Jul 1997||Weak night glow over the summit after 21 days of absence, indicating infilling of the crater floor with incandescent lava.|
|19 Aug 1997||Glow over the summit without degassing.|
|25-29 Aug 1997||Glow and fumarolic activity disappeared.|
The lava pond in the crater interior continued with small Strombolian eruptions throughout April 1997 and could be observed during clear nights as a red glow above the summit crater. The parallel fumarolic activity was moderate and mainly consisted of vapor. In May the activity of the lava pond increased considerably with respect to degassing intensity and frequency. At night incandescent bombs could be seen every 5 minutes. On 22, 23, 24, 30, and 31 May small ash clouds were regularly emitted to ~200 m above the summit.
In June, due to the beginning of winter, few observations of the summit could be executed. Nevertheless short periods of clear weather made possible a view of the activity level of the crater indicating small Strombolian explosions every 2 minutes. On 10 July observers realized that the red nocturnal glow had disappeared, hinting at subsidence of the magma column. Between 17 and 19 July the summit showed no more signs of fumarolic activity. On 22 July small fumarolic emissions were registered again. On 31 July weak night glow reappeared over the summit after an absence of 21 days.
On 19 August the glow reached the same intensity as in June. The crater did not show any explosive activity, indicating slow uplift of basaltic lava with low gas contents. Observers confirmed that the magma column had subsided again on 25 August for the second time this year and that the fumarolic activity was interrupted.
Geologic Background. Glacier-clad Villarrica, one of Chile's most active volcanoes, rises above the lake and town of the same name. It is the westernmost of three large stratovolcanoes that trend perpendicular to the Andean chain. A 6-km-wide caldera formed during the late Pleistocene. A 2-km-wide caldera that formed about 3500 years ago is located at the base of the presently active, dominantly basaltic to basaltic-andesitic cone at the NW margin of the Pleistocene caldera. More than 30 scoria cones and fissure vents dot the flanks. Plinian eruptions and pyroclastic flows that have extended up to 20 km from the volcano were produced during the Holocene. Lava flows up to 18 km long have issued from summit and flank vents. Historical eruptions, documented since 1558, have consisted largely of mild-to-moderate explosive activity with occasional lava effusion. Glaciers cover 40 km2 of the volcano, and lahars have damaged towns on its flanks.
Information Contacts: Werner Keller, Proyecto de Observación Villarrica/Internet (POVI), Wiesenstr. 8, 86438 Kissing, Germany (URL: https://www.povi.cl/).