Ground uplift of 25cm per year since 2007 suggests magma intrusion. If it erupts, pyroclastic flows could reach Argentina. It's the fastest-inflating volcanic system in the Andes.
NASA's Earth Observatory, CC BY 2.0, via Wikimedia Commons
A sleeping giant inflates
In the high Andes on the border of Chile and Argentina, the ground is swelling at an astonishing rate. Satellite measurements using Interferometric Synthetic Aperture Radar (InSAR) show that since 2007, the Laguna del Maule volcanic field has been inflating, with maximum vertical uplift speeds exceeding 25 centimeters per year. This deformation is one of the highest rates ever measured for a volcano that is not actively erupting. The cause is a massive body of magma accumulating roughly 5 kilometers beneath the surface.
Geophysical studies, including gravity and electrical resistivity surveys, have helped to outline this growing magma reservoir. The models suggest an inflating, sill-like body—a horizontal sheet of magma—is being fed from a deeper source. The total increase in volume from 2004 to 2012 alone was estimated at 0.15 cubic kilometers. The magma is rhyolitic, a type of silica-rich magma that is highly viscous and gas-rich. These characteristics are associated with highly explosive eruptions.
The uplift is not uniform; it accelerated after 2007, slowed slightly around 2014, and then began to accelerate again in late 2018. This dynamic behavior indicates an active and complex magmatic system. The total uplift between 2007 and 2014 was 1.8 meters, raising concerns and prompting the declaration of a yellow alert by the Southern Andes Volcano Observatory (OVDAS) in 2013.
A history of explosive volcanism
The Laguna del Maule (LdM) volcanic field is is not a single cone-shaped mountain, a sprawling 500-square-kilometer complex with at least 130 vents. Its eruptive history spans 1.5 million years, during which it has expelled over 350 cubic kilometers of volcanic material. The area shows this activity, featuring a ring of 36 rhyolite and rhyodacite lava domes and flows that erupted after the last glaciers retreated about 25,000 years ago.
While there have been no eruptions in recorded history, the geological record shows frequent and powerful events. The most recent confirmed eruption created the Las Nieblas rhyolitic lava flow around 800 years ago. Larger explosive events have also occurred, including several Plinian eruptions between 7,000 and 3,000 years ago. One eruption, less than 7,000 years old, produced a pumice fall deposit 4 meters thick as far as 22 kilometers away in Argentina.
The location of the volcanic field, straddling the Andean crest, is a transnational hazard. The topography slopes eastward into Argentina, creating a potential pathway for pyroclastic density currents. These fast-moving avalanches of hot gas and volcanic debris from a large eruption could travel tens of kilometers, crossing the international border.
💡Fun Facts
The uplift is so significant that ancient shorelines of the lake, formed during the Holocene, have been warped and tilted by the growing magma body below.
The LdM volcanic field is the largest concentration of silica-rich rhyolite erupted in the Andes during the last 25,000 years.
The lake itself partially fills a caldera created by a massive eruption around 950,000 years ago.
In pre-Columbian times, the area was an important regional source of obsidian, a volcanic glass used for making tools and weapons.
The area is accessible via the Paso Pehuenche international pass (Ruta 115 CH). The road is generally open 24/7, but passage can be restricted by Chilean customs (Aduana) and is subject to weather conditions, especially heavy snowfall in winter (June-October).
Admission
Free to access the area via the public road.
Accessibility
The main road to the lake is paved. The surrounding terrain is rugged and mountainous, suitable for hiking and, in winter, backcountry skiing. A 4x4 vehicle is recommended, especially if there has been recent snowfall.
