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volcano number: 1508-02= (according to Volcanoes
of the World, 1994 edition)
summit elevation: 2003 m
location: 41.326°S, 72.614°W
The north of Calbuco volcano, shows strongly
dissected older edifice to the right and active part of the volcano on the
left. The historically active crater lies in the smooth, snow-covered area
to the left. One of the 1961 lava flows (with distinct levees) extends down
from the central part of the volcano, where the younger part of the edifice
abuts against the older part.
Although less frequently active than Villarrica
and Llaima to the north, Calbuco is one of Chile's most notable volcanoes, due
to the violence of its eruptions and to the formation of large lahars
during its eruptions. Based on the fact that Calbuco
erupts once about every 30 years, and on a recent increase of its fumarolic activity, the volcano might be expected to be
the most likely candidate for Chile's next large
eruption.
Calbuco has grown during at least two stages, of
which an older, strongly dissected edifice in the W part of the volcano and
a younger one containing the active crater give testimony. The summit area
is occupied by a plateau-like feature about 1.5 km in diameter with the
active crater in its NE part. This plateau is covered with thick snow and
glacial ice all year round, thus the main hazard from the volcano in the
case of renewed activity is from snowmelt with the resulting formation of
lahars and meltwater floods. All historical
eruptions have produced lahars, causing damage in this area which, until
the time of the most recent eruption, in 1961, has been little inhabited.
Eruptions from Calbuco are both explosive and
effusive, and both types of activity are very likely to produce lahars
during future eruptions. Another hazard is that from airborne tephra that may reach great distances from the volcano
in the case of strong explosive activity (like in 1893) and may threaten
aircraft flying near the volcano. (...)
Eruptive History
The
record of Calbuco eruptions is very short,
starting only in the late 19th century. A 1837-38
eruption listed in older compilations has recently been re-attributed to Osorno.
The first historically documented eruption began on 7 January 1893 and lasted until
mid-January 1894. The initial phase of this eruption was violently
explosive and led to the generation of destructive lahars. During the later
stages of the activity, the volcano may have extruded lava although this is
not certain.
Minor eruptions occurred in 1895, 1906, on 22 April 1907, in March 1909,
and in 1911-1912; none of these events produced lava flows or lahars.
A significant eruption occurred again in April 1917 when a lava dome began
to fill the crater left by the 1893-94 eruption, and overflowing lava
melted part of the summit icecap. Resulting lahars caused damage along the
main rivers draining the volcano.
Another
major eruption occurred in January 1929. The exact dates of the beginning
and end of this event are not known, but the photo above was taken on 6
January, reportedly on the day "after a large explosive
eruption". Eyewitness accounts speak of "total darkness" in
the area of Lago Todos
los Santos whose west shore lies about 25 km
from the volcano's summit. The activity lasted only four days and produced
lava flows, glowing avalanches, and the resulting lahars caused devastation
in valleys around the volcano. Evidence for glowing avalanches was found by
Stone (1935) who reports that "brush and small trees (...) were
slightly charred, killed, and partly buried by some furious wind or blast
of ash that swept with devastating effect down the [Rio Blanco]
valley" and "some cattle were killed [in the same area],
seemingly burned to death by hot ash".
Ash emission from two vents, 1961
Aerial
view of Calbuco from SW, showing Somma-like rim of older edifice with highest summit in
the foreground and the active crater in eruption. Two boccas
are emitting dark ash plumes, the near one being the more active. Date of
photograph is unknown but apparently shows late stage of eruption when
effusive activity had ended and the eruption became more explosive. Lago Todos los Santos is in the right background. Scanned from
original photo provided by Werner Keller.
The most recent eruption from Calbuco occurred in
February-March 1961. Minor explosive activity began in late January but
more significant activity started on 1 February with the extrusion of a new
lava dome that broke through the glacier filling the summit crater.
Immediately after the onset of the activity, a lahar
rushed down the flanks of the volcano and reached the shore of Lake Llanquihue, about 10 km
north of the summit. Later, two thick and broad tongues of lava began to
extend from the dome over the NE and SE crater rims and down the flanks of
the volcano. With time, the activity became more and more explosive,
culminating in a large explosion on 10 March. This event produced a tephra column that rose about 15 km above the summit
and dropped meter-sized blocks at 0.5 km distance from the crater. Minor
activity continued for about one week; since then (that is, since more than
35 years) Calbuco has been quiet, with the
exception of a weak explosive eruption in 1972.
Stronger
than usual fumarolic activity from the summit
crater began to be noted by nearby residents in May 1995, and on 12 August
1996, a large steam plume was observed above the summit (report by H.
Moreno R. on Volcano Listserver). An overflight by Christian Brellenthin
(a resident of the area) on 12
October 1996 revealed an ice-free crater (probably
formed in 1961) about 50-100 m in diameter showing very weak fumarolic activity (information supplied by Werner
Keller).
References
Casertano L (1962) La actividad
volcanica en Chile durante 1961. Boletín de la
Universidad de Chile, No. 30 (June 1962): 40-45.
López-Escobar L, Parada
M, Moreno H, Frey FA & Hickey-Vargas RL (1992) A contribution to the petrogenesis of Osorno and Calbuco volcanoes, Southern Andes (41°00'-41°30'S):
comparative study. Revistia Geológica
de Chile vol. 19: 211-226.
Stone JB (1930) Two active volcanoes of Chile. The Volcano
Letter No. 284 (5 June 1930). All issues of
the Volcano Letter were re-printed in 1987 by the Smithsonian Institution.
Stone JB (1935) The volcanoes of Southern Chile. Zeitschrift für Vulkanologie vol. 16: 81-97.
Extracted from Werner
Keller's and Boris Behnke's Chile's Volcanoes
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