Calbuco: A Deep Dive into the Volcano That Erupted Without Warning
In April 2015, after more than four decades of quiet, the Chilean volcano Calbuco erupted with almost no warning, sending colossal columns of ash soaring into the sky above the Lake District. The dramatic eruption, captured in spectacular photographs and video, became one of the most striking volcanic images of the decade. Calbuco is one of the most dangerous volcanoes in southern Chile, and its sudden 2015 awakening underscored how quickly a long-quiet volcano can spring to life.
A rugged Lake District volcano
Calbuco reaches about 2,003 metres and rises in Chile's southern Lake District, near the city of Puerto Montt and the lakeside town of Puerto Varas. Unlike the elegant, symmetrical cone of its neighbour Osorno, Calbuco is a more rugged, compact edifice. It is considered one of the most hazardous volcanoes in the southern Andes, owing to its explosive history and proximity to populated areas.
A history of explosive eruptions
Calbuco has erupted numerous times over the past few centuries, often explosively. Its eruptions have produced ash, pyroclastic flows, and lahars, making it a serious hazard to the surrounding region. Before 2015, its most recent significant activity had been in the early 1970s, after which it entered a long period of quiet that lulled many into thinking of it as dormant.
The sudden 2015 eruption
On 22 April 2015, Calbuco erupted suddenly, with only a few hours of detectable precursors. It blasted an enormous column of ash and gas more than ten kilometres into the sky, followed by a second powerful explosion. The eruption forced the evacuation of thousands of people, disrupted air travel across the region, and blanketed towns in ash. The images of the towering, lightning-laced eruption column circulated around the world.
The challenge of short warning
One of the most striking aspects of the 2015 eruption was how little warning it gave. Calbuco escalated from quiet to a major explosive eruption in a very short time, posing a serious challenge for monitoring and evacuation. The event became a case study in the difficulty of forecasting eruptions at volcanoes that have been quiet for decades, even with modern monitoring.
Ashfall and its impacts
The 2015 eruption spread ash across a wide area, affecting communities in Chile and neighbouring Argentina. Ashfall disrupted agriculture, water supplies, and daily life, and the cleanup took considerable effort. The eruption demonstrated the far-reaching impact that even a relatively short-lived explosive event can have on a populated region.
Lahars and lingering hazards
Beyond the immediate eruption, Calbuco's deposits posed continuing hazards. Heavy rain on fresh ash and debris generated lahars in the following weeks and months, threatening valleys and infrastructure. This secondary hazard is a common feature of explosive eruptions and a key concern in the aftermath, requiring ongoing vigilance even after the main eruption subsides.
Monitoring Calbuco today
Following the 2015 eruption, monitoring of Calbuco was reinforced as part of Chile's broader volcano surveillance. Seismic networks, deformation sensors, and gas measurements track its behaviour, with the goal of detecting any future unrest as early as possible. The 2015 event remains a powerful reminder of the importance of watching even seemingly quiet volcanoes.
Explore on the map
Calbuco stands among Chile's chain of Lake District volcanoes, alongside Osorno, Villarrica, and Llaima. Explore it on the interactive map — filter by country to see Calbuco among Chile's volcanoes and to appreciate the explosive power hidden within the scenic southern Andes.