As global temperatures increase, glaciers are melting in mountain ranges all over the globe. Between 2000 and 2023, the Alps and Pyrenees in Europe lost 40% of their glacier volume. For ages, people downstream have relied on this and other glacial areas for freshwater; now, about 2 billion people depend on glaciers.
However, glaciers can provide potentially fatal hazards since they melt more quickly. Large lakes are often formed as water from the melting ice flows into depressions that the glacier originally inhabited. Precarious ice dams or rock moraines that the glacier has accumulated over generations are responsible for holding many of these growing lakes in place.
These dams may be broken by too much water behind them or by a landslide into the lake, which would send massive amounts of water and debris rushing down the mountain valleys and destroy everything in their path. The United Nations designated March 21 as the inaugural World Day for Glaciers and 2025 as the International Year of Glacier Preservation in part because of these threats and the depletion of freshwater resources. As mountain geographers and Earth scientists, we investigate how ice loss may affect the stability of nearby glacier lakes and mountain slopes. Concern is growing for a number of reasons.
Landslides and ice dam eruptions: The majority of glacial lakes started to emerge more than a century ago due to warming trends that started in the 1860s, but since the 1960s, their numbers and growth rates have increased significantly. Numerous inhabitants of the Himalayas, Andes, Alps, Rocky Mountains, Iceland, and Alaska have seen floods of some kind caused by glacial lake outbursts.
In October 2023, a 200-foot (60-meter) hydroelectric facility was demolished and over 30 bridges were damaged in the Himalayas due to a glacial lake outburst flood. There was minimal warning for the residents. done fifty persons had perished by the time the catastrophe was done. A glacier lake on an arm of Mendenhall Glacier that has been blocked by ice has caused many flash floods in Juneau, Alaska, in recent years.
A melting glacier that gradually flooded a basin below it until the ice barrier burst caused those floods, including the one in 2024. Glacial lake outburst floods may also be caused by avalanches, rockfalls, and slope collapses. As permafrost, or frozen earth, thaws, mountain landscapes lose the cryospheric glue that formerly bound them together, making them more frequent. When these slides fall into a lake, they may produce enormous waves.
A rush of water, silt, and debris may then be released if the waves break through the moraine or ice barrier. At 20–60 mph (30–100 kph), the hazardous mixture may surge downstream, demolishing houses and other objects in its path. Such an incident might result in a shocking number of victims. The moraine barrier that had kept Laguna Palcacocha, a glacial lake in the Peruvian Andes, confined for decades was overtaken in 1941 by a massive wave brought on by a snow and ice avalanche that dropped into the lake.
Between 1,800 and 5,000 people were murdered in the ensuing flood, which also devastated a third of the city of Huaraz downstream. The risk there has only grown in the years after. The size of Laguna Palcacocha has increased by around 14 times since 1941. Meanwhile, Huaraz’s population has increased to more over 120,000 people. Today, an estimated 35,000 people who live in the water’s path might be at danger of dying in a glacial lake outburst flood.
In response to this pervasive and increasing concern, governments have created programs and early warning systems to detect potentially hazardous glacial lakes. Some governments have constructed gabions, which are walls of wire cages packed with rock, to divert floods from communities, infrastructure, or agricultural areas, or they have taken action to decrease the water levels in the lakes. Communities have been urged to utilize zoning that forbids development in flood-prone regions where the hazards cannot be controlled. Although flood danger has been made more widely known via public education, the tragedies still happen.
Internal flooding and melting permafrost: Glacial lake outburst floods are spectacular events that make news, but there are other dangers as well. Scientists are discovering many more processes that might result in equally catastrophic disasters as they deepen their grasp of the relationship between global warming and the world’s frozen areas. For example, glacial conduit floods begin within glaciers, usually those on steep slopes. Meltwater may gather inside extensive networks of pipes, called ice caverns. A chain reaction that explodes out of the ice as a full-fledged flood may be started by an abrupt flow of water from one cave to another, perhaps caused by a surface pond draining quickly. Floods may also be caused by thawing alpine permafrost.
For thousands of years, this permanently frozen mass of rock, ice, and dirt has been present at elevations higher than 19,685 feet (6,000 meters). Mountains are held together by freezing. However, even solid rock becomes less stable and more liable to collapse when permafrost thaws, and ice and debris are more likely to separate and form hazardous debris flows. Due to these novel sources of possible triggers, thawing permafrost has been increasingly linked to glacial lake outburst floods. In 2017, almost one-third of the 20,935-foot (6,374-meter) solid granite face of Nepal’s Saldim Peak tumbled to the Langmale glacier below.
A tremendous flood was caused by the slurry of rock, debris, and silt that fell into the Langmale glacial lake below as a consequence of heat from the friction of stones falling through air melting ice. Climate change is making these and other glacier-related floods and risks worse. Other instances include the abrupt emergence of meltwater ponds on the surface of a glacier and flows of ice and debris from high heights. Glacier lake outburst floods may potentially be caused by earthquakes. In addition to the destruction of hydropower plants and other infrastructure worth billions of dollars, thousands of lives have been lost.
A reminder of the danger: The World Day for Glaciers and the International Year of Glacier Preservation serve as reminders of the dangers and the people who are at risk. The cryosphere, or the 10% of the Earth’s land area covered in ice, is essential to the world’s population. However, floods and other hazards are increasing as more glacial lakes develop and grow.
According to a 2024 research that surveyed over 110,000 glacier lakes worldwide, 10 million people’s houses and lives are at danger due to floods caused by glacial lake outbursts. The UN is promoting more study in these areas. Additionally, 2025–2034 was proclaimed the “decade of action in cryospheric sciences.” In order to assist communities adapt to and lessen the hazards, scientists from across continents will be striving to understand the threats.
