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Abnormal seismicity under Lanin volcano, alert level raised

earthquake-swarm-lanin-volcano-february-2017

An energetic seismic swarm has been detected under Lanin volcano on the border of Chile and Argentina, prompting the Chilean National Geological and Mining Service (Sernageomin) to raise the volcanic alert level to Yellow. The last known eruption of this volcano took place in the year 560 (± 150 years).

According to Sernageomin's special report issued February 15, a swarm of earthquakes, associated with the movement of fluids inside the volcano, started at 18:24 UTC and lasted 59 minutes and 45 seconds. The strongest earthquake had a magnitude 1.8.

No changes have so far been observed at the surface. 

Sernageomin said the seismicity continued after they issued the report and estimated that there could be a destabilization of the volcanic system.

Given the relevance of this unusual activity, the agency has raised the alert level to Yellow.

This has activated the Civil Protection System and the notification to the Argentine Mining Geological Service to take measures to safeguard the population on both sides of the border.

Geological summary

Lanín is a large conical late-Pleistocene to Holocene stratovolcano along the Chile-Argentina border. The dominantly effusive basaltic-to-trachydacitic volcano lies at the eastern end of a NW-SE-trending volcanic group beginning with Villarrica that is transverse to the Andean chain. The beautifully symmetrical, 3776-m-high Lanín rises 2500 m above its base; shoulder areas on the upper flanks hint at a buried caldera. The volcano was formed in four eruptive stages dating back to the early Pleistocene or late Pliocene. The last two stages occurred during the late-Pleistocene and Holocene.

A small lava dome at the summit fed blocky lava flows to the north about 2200 years ago. Lanín was reported active after an earthquake in 1906, but Sapper (1917) stated that newspaper accounts are strongly disputed, and no historical eruptions are known. A postglacial tuff ring (Volcán Arenal) is located below the SW flank in Argentina. A younger lava flow from Lanín covers deposits of Volcán Arenal and extends south into Lago Paimún. (GVP)

Featured image: Lanin volcano . Courtesy of Hugo Moreno (University of Chile)

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