The 1948-1949 eruption

Lava fountain from summit, ash and steam from flank vents: the eruption of 1948-1949
(Full picture JPEG: 120K) Spectacular aerial view of the summit area of Villarrica during a powerful eruption on 31 January 1949 (the latest culmination during the 1948-1949 eruptive period). A broad incandescent lava fountain rises from the summit crater while steam and ash issues from small boccas on the upper flanks, indicating high pressure in the mountain. Note absence of snow and ice on the usually ice-covered volcano. Photo is taken from Casertano (1963b).

Following the major 1908 eruption and minor activity in 1920 and maybe 1929, Villarrica remained relatively quiet for decades, the only manifestation of its activity being fumarolic emissions from its summit crater.

A spectacular and devastating eruption began on 9 October 1948, after a notable increase of fumarolic activity. Initially, the activity was relatively weak and caused only light ash falls onto the snow-covered flanks of the volcano, and incandescent ejections were seen at night.
An active lava lake was observed within the summit crater during an overflight on 15 October. Strombolian explosions from the lake surface ejected glowing spatter onto the crater rims. On the following day, explosions occurred every 3-5 minutes.
The eruption intensified dramatically at 0625 on 18 October, when vigorous explosions produced a large tephra plume, and numerous lahars formed on the flanks of the cone. A total of about 1000 hectares of arable land and forest were buried by mudflows, numerous buildings were destroyed, and 23 people were killed, 31 others missing. Powerful explosions and lava fountaining continued through the day, removing all ice from the summit region. Only steaming was present at the summit crater in late October.

On 25 December, the volcano showed signs of renewed activity. At 2030 on that day, lava began to flow down the flank towards Molco and Calafquén. By 29 December, the flow appeared as a ribbon of fire 500 m long. On 1 January 1949, the eruption intensified dramatically when, at 1615, a huge ash plume rose about 8 km above the summit to attain a mushroom shape. In the late evening, a brilliant glow was visible at the base of the column. Lahars formed on the SW flank of the cone but did not attain the magnitude of those of 18 October and caused only minor damage.
Following this culmination, Villarrica returned to mild steaming and weak emissions of ash (?) that continued through late January.

New Year's eruption in 1949 with pyroclastic flow
(Full picture JPEG: 89K) Extremely rare photo showing Villarrica during the second paroxysm during its 1948-1949 eruptive cycle, on 1 January 1949. Some editing was necessary to highlight important features of the photo. A dark tephra column is shooting upwards from the summit crater, forming an eruption column rising at least 5 km above the crater. Note cloud on the western (right) flank of the volcano, probably from a pyroclastic flow; a similar but darker cloud is visible on the opposite flank. Original photo taken by Pollak, re-photographed by Mrs. Keller.

A third strong eruptive episode began at 0730 on 31 January 1949 with loud rumblings causing alarm among the neighboring population, followed by powerful explosions. During the next 5 h, a spectacular lava fountain rose from the summit crater while several vents opened below the summit and emitted steam and ash. A photo taken during this eruption shows the summit completely free of snow and ice and steam and ash rising from several vents or fissures below the summit. The melting of snow again caused lahars that were about as large as those of 18 October and extended as far as Lake Villarrica. The deposits produced by these lahars, however, contained less large blocks than those of October. A number of houses and large areas of arable land were buried by the lahars, but fortunately, no persons were injured or killed this time.
After noon, the activity decreased notably, and during the following nights, weak ejections of incandescent material from the summit crater were noted. During the first days of February, a lava flow advanced down the NW flank to reach a total length of 10 km, attaining a volume of roughly 6 x 10^6 m^3. All activity ended after 3 February 1949.
After the eruption, the summit crater appeared as a cylindrical pit 200 m in diameter and more than 200 m deep. This indicates that, after the final lava emission of early Feb, the withdrawal of the magma column caused the collapse of the intracrateral cone and/or lava lake.