Planchón-Peteroa volcano enters new eruptive phase

Planchón-Peteroa volcanic complex, located on the Chile–Argentina border in the central Andes, entered a new phase of eruptive activity in late October 2025. The Argentine Geological and Mining Service (SEGEMAR) confirmed that a new eruption began on October 25, producing sustained gas and ash emissions visible from both sides of the border.

Monitoring data from the Servicio Nacional de Geología y Minería (SERNAGEOMIN) and the Observatorio Volcanológico de los Andes del Sur (OVDAS) indicated that seismic activity began increasing several months before the eruption.

From March 2025, low-magnitude (mostly less than M2) volcano-tectonic earthquakes were recorded beneath the complex. On June 19, a tremor pulse with deep-source characteristics was detected. Seismicity increased further between July 13 and 15, dominated by long-period (LP) events and tremor pulses linked to internal fluid movement. From July 13 to 16:40 LT on July 16, the monitoring network detected more than 1 200 low-energy events, marking a clear shift toward LP-dominated seismicity.

On July 18, the alert level was raised to Yellow, the middle level on a three-color scale, and access restrictions were expanded. The Sistema y Servicio Nacional de Prevención y Respuesta Ante Desastres (SENAPRED) issued a “Preventive Early Warning” for the communities of Molina, Curicó, Romeral, and Teno, limiting access within a 4 km (2.4 miles) radius of the active craters.

The Buenos Aires VAAC issued multiple advisories between October 25 and November 11. Reported plume heights ranged from 4 300 to 4 600 m (14 000 to 15 000 feet) above sea level, drifting mainly east and northeast depending on prevailing winds. Continuous emission to 4 300 m (14 000 feet) a.s.l. was noted in the latest November 11 advisory.

Satellite imagery acquired on November 8 showed a significant increase in ash emission with the plume drifting toward the southeast. This coincided with continuous degassing and sustained low-intensity explosions at the active vent.

Satellite image of ash from Planchón-Peteroa volcano on November 8, 2025. Credit: Copernicus EU/Sentinel-2, The Watchers

Satellite image of ash from Planchón-Peteroa volcano on November 10, 2025. Credit: Copernicus EU/Sentinel-2, The Watchers

Thermal observations indicated intermittent hotspots at the crater consistent with shallow magma–hydrothermal interaction. However, no publicly released deformation measurements suggest large-scale magma intrusion into the upper conduit.

No reports of lava flows, significant pyroclastic activity, or major structural collapse were issued. The observed behaviour corresponded to low-intensity eruptive activity typical of the volcano’s recent pattern since its 2018–2019 eruption sequence.

Authorities in Chile and Argentina maintain the alert level at Yellow (“changes in the behaviour of volcanic activity”). SERNAGEOMIN advises avoiding approaches to the crater area due to the risk of minor explosions and ashfall.

Although no population centres were directly affected, light ash dispersal could affect air quality and aviation operations in the vicinity.

The last eruptive phase at this volcano lasted from November 2018 to May 2019, with Volcanic Explosivity Index estimated at 2.