Lonquimay Volcano | John Seach



38.38 S, 71.58 W
summit elevation 2865 m

Lonquimay Volcano is located in central Chile. A glacier is located in the summit crater and down the south flank.

Lonquimay volcano contains five different sequences.
1) A deeply eroded stratified subhorizontal volcanic sequence, up to 400 m thick, with andesitic and basaltic lavas on the northwest and southeast flanks of the volcano.
2) Postglacial andesitic pyroclasts and lavas on the eastern flank and in the main crater.
3) Andesitic lava flows (basaltic to siliceous, emitted from the main and secondary craters on the eastern fissure, with almost no signs of erosion.
4) Basaltic-andesitic to andesitic lavas and pyroclasts, emitted from secondary craters on the eastern flank.
5) Aa-type lava and andesitic-basaltic to andesitc blocks.

1988-90 Eruptions
Eruptions began at Lonquimay Volcano on 25th December 1988 at a location on northeastern flank. The Strombolian eruptions were the first at the volcano in 100 years. Earthquakes were felt for three weeks prior to the eruption. During the first
month of the eruption, more than 800 earthquakes were recorded. The eruption began at eight small vents along an 800 m long fissure, 3.5 km from the summit. Explosive phreatomagmatic eruptions began on 27th December 1988 at 1820 with the emission of a column of gas and tephra, which rose to a height of 9 km in 5 minutes. Satellite images showed plumes extending 500 km from the volcano.

By April 1989 Navidad cone (an asymmetric pyroclastic cone composed of black scoria with a minor amount of spatter-like bombs), was 210 m high and 700 m wide. Hundreds of cattle and horses had died of fluorosis caused by deposition of 300-400 ppm fluorine on grass over an 800 sq km area.

By early July 1989, evacuation had begun of 800 inhabitants of the Bernardo Nanco area, and 3,800 from the town of Lonquimay. A 64-year-old woodcutter was suspected to have died from effects of breathing ash over a period of months.

On 10th January 1990 lava flowed from a vent at the NE foot of Navidad Cone, at a speed of 70 metres/hr. The eruption from Navidad Cone ended between 22 and 25 January 1990, after 13 months of activity.

1940 Activity
Fumarolic activity occurred at Lonquimay Volcano, with uncertain eruptions.

Further reading
Gilbert, David, et al. "Post-glacial time series of explosive eruptions and associated changes in the magma plumbing system of Lonquimay volcano, south central Chile." International Journal of Earth Sciences 103.7 (2014): 2043-2062.

Kerr, R.C. and Lyman, A.W., 2007. Importance of surface crust strength during the flow of the 19881990 andesite lava of Lonquimay Volcano, Chile. Journal of Geophysical Research: Solid Earth, 112(B3).

Naranjo, J. A., et al. "Morphological, structural and textural variations in the 19881990 andesite lava of Lonquimay Volcano, Chile." Geological Magazine 129.6 (1992): 657-678.

Lonquimay Volcano Eruptions

1988-90, 1940?, 1933, 1887-90, 1853