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The Andes region is highly susceptible to disasters caused by glaciers. However, Argentine glaciologist Lucas Ruiz emphasises the importance of community awareness regarding the fact that not all glacier collapses will lead to catastrophic flooding akin to the event witnessed in Nepal on August 28. “The existence of danger does not imply that an event of such magnitude will occur. Our aim is to generate action and measures to study these phenomena, rather than allowing fear to paralyse us,” he stated in a conversation.
The devastating flood that engulfed entire communities and critical infrastructure in Nepal was triggered by the collapse of a glacier and the rock at its base. It has now been established, Ruiz elaborates, that the collapse formed a natural dam which temporarily blocked the river, leading to a significant accumulation of water that was eventually released.
Ruiz indicates that climate change acts as a “catalyst” for these events. He highlights that heatwaves, rising temperatures, and increasingly prolonged summers contribute to the melting of glaciers. Furthermore, areas that previously received snowfall, which nourished the glaciers, are now experiencing more rain, exacerbating the melting process.
The rainfall, in turn, increases pressure at the glacier’s base and facilitates sliding, while also accelerating melting and fracturing the rocks that support massive ice blocks. This scenario creates conditions ripe for significant rockfalls and avalanches.
“Global climatic phenomena, such as El Niño-Southern Oscillation, can also play a role,” adds Felipe Ugalde Peralta, a Chilean geologist specialising in glaciology. He notes that El Niño could lead to intense hydrometeorological events with rain at high altitudes in areas that once received snow.
Additionally, El Niño typically brings hotter summers, which could accelerate melting, according to Ruiz. Ugalde Peralta also underscores the importance of local factors, such as the type and arrangement of rocks beneath the glaciers. He points out that one hypothesis regarding the Nepal incident suggests that the rocks in that region had specific characteristics contributing to the magnitude of the collapse.
Understanding the Threat of Volcanic Activity
In the Andean region, Ugalde Peralta identifies glaciers located on volcanoes as one of the greatest threats. He recalls the 1985 eruption of the Nevado del Ruiz volcano. Although not particularly large, it melted snow and ice, subsequently creating a lahar that travelled over 100 kilometres, burying the town of Armero.
<p“If there are active volcanoes with glaciers on their surface, they must be examined through the lens of glaciovolcanic interaction,” remarks the Chilean specialist, noting that this concern extends across Colombia, Ecuador, Peru, and Chile.
Paola Moschella, director of glacier research at the National Institute of Research on Glaciers and Mountain Ecosystems (INAIGEM) in Peru, warns that not all glaciers pose a risk. Nonetheless, she asserts that tropical Andes are more vulnerable to melting primarily due to climate change. This region stretches from Venezuela to Bolivia, excluding Chile and Argentina.
According to Moschella, Peru has the highest concentration of tropical glaciers, situated in high-altitude mountains above 5,000 metres. She states that climate change has already caused a 59% reduction in the glacier surface area in Peru, which increases susceptibility to potential disasters. Additionally, nearby populations and cities heighten the risk.
The threat of large ice mass collapses is not the only concern. Another documented phenomenon includes glacial lake outburst floods (GLOF), which result from the sudden emptying of glacial lakes. Several Andean countries could be impacted by this occurrence.
The GLOF Risk in Peru
Ruiz explains that GLOFs are easily quantifiable as they are associated with the formation and growth of lakes following glacier retreat. To assess these threats, the dams holding the lakes are analysed alongside the volume of water that would flow into the basin in the event of a breach.
In Peru, disasters of glacial origin have already been recorded, according to Moschella. In 1970, an earthquake off the coast triggered a massive ice and rock collapse from Huascarán, the highest mountain in Peru and the tropical region. The resultant melting ice created a sudden influx of water, which mixed with rocks and soil, leading to a flood that travelled dozens of kilometres, resulting in 6,000 fatalities.
At present, two glacial hazards threaten populated areas, the expert notes. The first involves ice and rock avalanches, which, as past events have shown, can generate floods in lower areas due to their material volume and velocity. The INAIGEM has identified glaciers at risk of collapse on both the southern and northern peaks of Huascarán. A 2020 study found that a collapse from susceptible glaciers could entirely affect the urban area of Ranrahirca and parts of Yungay, home to 11,385 people. These two towns were also devastated by the 1970 flood.
On the other hand, a collapse on the southern peak could lead to a flood reaching populated areas in under 12 minutes, impacting more than 9,900 individuals, according to an evaluation published in 2025.
Glacial Lakes and Flooding Risks
The second risk involves the overflow of glacial lakes. A national assessment conducted in 2024 identified 528 lakes at risk of overflowing, with 58 posing a very high risk, Moschella points out. “We are not indicating an imminent danger but rather referring to lakes that meet a series of conditions,” she clarified. These could include steep slopes, avalanche zones, and natural dams made of unconsolidated materials.
Among the highest alert cases is the Palcacocha lake, located above the city of Huaraz in the Ancash region, which has overflowed in the past, burying a third of the city. “That same lake has been growing and poses an even greater risk,” she warned, noting that approximately 27,000 people are exposed to this threat.
The INAIGEM conducts real-time monitoring of the Upiscocha, Palcacocha, and Gangrajanca lakes. According to Moschella, they are working to expand real-time monitoring efforts, which allow for automated alerts to local governments when danger thresholds are exceeded, providing valuable minutes for nearby populations to respond.
The institution continues to gather information, produce hazard maps, and offer technical assistance. However, the director asserts, “it is up to local authorities to implement mitigation measures.” She revealed that the Geophysical Institute of Peru (IGP) will launch early warning systems in areas exposed to potential flooding in Huascarán.
Chile’s Glacial Monitoring Challenges
Chile faces significant risks from glacier-related disasters, particularly in the central region, according to Ugalde Peralta. In 2025, he published a study assessing the susceptibility of glacial disasters in the Volcán River basin, located in Cajón del Maipo, Metropolitan Region. This area, which includes several settlements, a hydroelectric plant, a gypsum mine, and thermal springs, was prioritised for risk management analysis due to its relevance. The basin is also capped by the active San José volcano.
The study found that ten glaciers are highly susceptible to ice avalanches, one to sudden advances, two to catastrophic collapses, seven to GLOFs, and three to lahars triggered by volcanic eruptions. Ugalde Peralta is currently expanding this research across central Chile, which harbours 4% of the country’s glaciers but is home to nearly half of its population. He is identifying characteristics that increase the likelihood of disasters, such as glaciers with steep fronts on slopes typically around 30 degrees. For GLOFs, the primary conditioning factor is the presence of a glacial lake or a glacier that is melting and forming bodies of water.
Some sites preliminarily identified as highly susceptible to generating ice avalanches include the Juncal Norte glacier, in the Aconcagua basin, which features a five-hectare lake, and another glacier in the Juncal river basin with a two-hectare lake. “They exhibit characteristics suggesting they could be highly susceptible, but these are preliminary results that require further analysis,” he notes.
The case that raises the greatest concern involves the glacier, lake, and Cerro El Morado. A former ice waterfall has melted, creating a lake. Currently, only a hanging glacier remains at the mountain’s summit, where various-sized ice avalanches have occurred without impacting the lake thus far. Some of these avalanches have reached volumes of 50,000 cubic metres, which is low compared to the hundreds of millions reported in Nepal.
He warns that the combination of a hanging glacier with a glacial lake directly below poses a significant risk. The collapse of the ice block could generate a wave that overflows the natural dam, creating a large-scale flood.
Argentina’s Need for Early Warning Systems
In Argentina, glacier-related disaster risks are concentrated in Patagonia and the central Andes, as noted by glaciologist Lucas Ruiz. In 2007, a glacier collapse occurred in southern Mendoza, which was identified through satellite imagery but resulted in minimal impact.
Regarding GLOFs, Ruiz points out that Patagonia contains the highest number of glacial lakes, which have expanded significantly. In contrast, the central