RAPID: Increased activity and risk for volcanic hazard at the Laguna del Maule volcanic field, Chile

The project investigates the cause of a recent increase in volcanic activity at the Laguna del Maule volcanic field, Chile, which has in the past produced voluminous and explosive volcanic eruptions. Starting in September 2025, the ground surface has been rising ~4.5 cm per month, double the rate observed there over the last 15 years. The number of earthquakes has also increased and appear clustered above or near a growing magma body. This volcano has a series of 31 marked stations where gravity measurements have been repeatedly measured since their installation in 2013, with the most recent measurements taken in 2024. Changes in the gravity measurements in this case are likely caused by addition of magma below the ground surface. By repeating gravity measurements in 2026, the team can determine the amount of magma added in the last two years. The team will also deploy seismometers for two weeks to determine the precise location of the earthquakes, which likely occur at the edges of the growing magma body. Together, these data will reveal if there was a recent influx of magma and if so, provide information on the size, shape, and chemistry of the growing magma body. The team will evaluate the present volcanic hazard at the Laguna del Maule volcanic field. Then, they and others can apply new insights to other similar volcanoes, including the Cascades volcanoes in the western United States. This team is investigating the cause of recent unrest at the Laguna del Maule volcanic field (LdMvf), which hosts extensive rhyolitic lava flows. Uplift rates of ~2.6 cm/month since 2007 are interpreted to be caused by addition of magma ~5 km below the volcanic field. Starting in September 2025, uplift rates have nearly doubled to ~4.5 cm/mo. Also, several swarms of seismic events have been detected, including some of the largest earthquakes recorded at LdMvf. Together, these data suggest magma addition to the magma body beneath the lake. A network of gravity stations designed to measure microgravity will be remeasured. Those results will be compared to the last measurements taken in January 2024. The gravity work will be complemented by a short (2 week) deployment of seismic nodes, installed at a subset of stations. The seismic data will provide insight into the extent to which faults are accommodating this intrusion of magma and constrain near-surface velocity changes that will improve gravity modelling. Modelling will constrain the composition of the intruding magma, which impacts the projected eruption style. This work will improve understanding of the mechanisms that control magma emplacement, and their impacts on hazards, at silicic volcanoes on human timescales. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.