Increased seismic activity prompts Yellow alert for Laguna del Maule volcanic complex, Chile

Due to an increase in seismicity detected since March 30, 2023, Chilean authorities raised the Alert Level for Laguna del Maule volcanic complex from Green to Yellow on April 3, 2023.

  • The last eruption at this volcano took place in 50 BCE.
  • The Laguna del Maule volcanic complex is located in the border area with Argentina in the Maule Region.
  • The complex covers around 500 km2 (193 mi2) and is made up of cones, shield volcanoes, domes and lava flows.

Patricio Aguilera, National Director of SERNAGEOMIN, explained that this change in alert level is due to abnormal activity within the complex, which has been monitored by their Volcanological Observatory (OVDAS).1

The seismicity is characterized by volcano-tectonic events, commonly associated with magma movement below the volcano.

It is located in an elongated area in a northwest-southeast direction, approximately 10 km (6.2 miles) to the southwest of the center of the lagoon and with a depth range of up to 8 km (5 miles).2

It is important to indicate that, although the development of this seismicity is the longest since the beginning of monitoring in the year 2012, its magnitudes have been of low energy.

However, the record of earthquakes stands out as sporadic events with increasing magnitude, such as those that occurred on April 3, with local magnitudes of 2.5, 2.8 and 2.9, at depths between 4.5 and 8 km (2.8 – 5 km), located in the Nieblas sector.

The deformation rates remain unchanged, although the inflationary process continues with a
monthly rate of 1.5 cm (0.6 inches) per month.

Other activity parameters such as morphological changes, analysis of temperature, and emission of SO2 to the atmosphere, by remote sensors, remain until now, invariable.

The zone of possible affectation by volcanic hazards is located in a radius of 2 km (1.2 miles) around the center of CO2 emission.

In response to the information provided by Sernageomin, Álvaro Hormazábal, National Director of SENAPRED, declared a Yellow Alert for the San Clemente commune, reinforcing technical monitoring of the volcanic complex.

Hormazábal mentioned that contingency measures have been developed over the years in collaboration with the municipality of San Clemente. These include plans regarding potential eruptions, and contingency planning for the customs complex located on route CH-115.

Geological studies have identified at least 130 individual eruptive centers, which have produced more than 170 km3 (40.8 mi3) of material. In particular, 36 post-glacial lavas and domes of rhyolitic and rhyodacitic compositions have been recognized, originating from 24 different eruptive centers.

The current landscape of the area is believed to be a result of tectonic, volcanic, and glacial processes, with evidence suggesting that the lake was formed by glacial and tectonic processes, and the damming of the lake’s waters primarily due to volcanic effusions.

laguna del maule chile march 31 2023 bg
Laguna del Maule, Chile on March 31, 2023. Credit: Copernicus EU/Sentinel-2, The Watchers

Geological summary

The 15 x 25 km (9 x 15 miles) wide Laguna del Maule caldera contains a cluster of small stratovolcanoes, lava domes, and pyroclastic cones of Pleistocene-to-Holocene age. The caldera lies mostly on the Chilean side of the border, but partially extends into Argentina.

Fourteen Pleistocene basaltic lava flows erupted down the upper part of the Maule river valley.

A cluster of Pleistocene cinder cones was constructed on the NW side of Maule lake, which occupies part of the northern portion of the caldera.

The latest activity produced an explosion crater on the E side of the lake and a series of Holocene rhyolitic lava domes and blocky lava flows that surround it.3


1 Reporte Especial de Actividad Volcanica (REAV) for Laguna del Maule volcanic complex – SERNAGEOMIN – April 3, 2023

2 SENAPRED y SERNAGEOMIN elevaron nivel de Alerta del Complejo Volcánico Laguna del Maule – SENAPRED – April 3, 2023

3 Laguna del Maule volcanic complex – Geological summary – GVP

Featured image credit: SERNAGEOMIN

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