The National Geological and Mining Service of Chile (SERNAGEOMIN) raised the alert level for the Antillanca-Casablanca volcanic complex in the Los Lagos region of Chile to Yellow on March 11, 2020, after a swarm of 73 tremors detected since March 9. The last eruption at this volcanic complex took place in 230 BCE (± 200 years) -- VEI 5, Casablanca volcano (Raihuen crater).
The alert was raised from Green to Yellow after the series of seismic events due to rock rupture, with tremors up to M1.8 located around 2.4 km (1.5 miles) north-northwest of the Casablanca volcano.
Moreover, other events were detected on January 31 and February 1 with M3.1 and M3.2, respectively -- west and northwest of the Casablanca volcano. Other parameters did not show significant variations, SERNAGEOMIN said.
73 tremors recorded on March 9 were added to other episodes detected late January and August 2019, which were higher than the usual activity level of this volcano.
As a result, the ONEMI regional directorate declared the preventive early warning of the civil protection system for the Puyehue and Puerto Octay municipalities.
According to SERNAGEOMIN's alert scale, yellow alert suggests minor explosions or possible fumaroles, and the notice is intended to keep the public informed while bi-weekly activity reports are issued.
The Antillanca Group is a cluster of late-Pleistocene to Holocene basaltic-to-andesitic scoria cones, maars, and small stratovolcanoes covering an area of 380 km2 SE of Lago Puyehue and NE of Lago Rupanco.
The most prominent edifice is the Holocene Casablanca stratovolcano, which has a truncated conical profile and produced major explosive eruptions about 2910 and 2260 radiocarbon years ago.
Older late-Pleistocene stratovolcanoes, such as Sarnoso on the SW side and Fiuchá on the NW side, are extensively dissected by glaciers. Fissures oriented in four major directions influence the orientation of the cones.
Thermal areas are found in scattered locations on the NW side of the complex (GVP).
Featured image credit: SEGEMAR