Glaciers are dynamic bodies of ice that change all the time.  Anyone who gets too close could fall in a crevasse, step on a snow bridge that collapses, or get hit by falling ice or rock.  Every year people without proper mountaineering training, or just bad luck, die from climbing on or around glaciers.

Glaciers also pose significantly larger hazards to societies worldwide.  Avalanches and glacial lake outburst floods (GLOFs) are the most destructive types of glacier disasters that have affected people in mountain ranges around the globe.

The most deadly glacier disaster was the 1970 glacier avalanche from Mount Huascarán in Peru’s Cordillera Blanca mountain range, which killed between 6,000 and 15,000 people in Yungay (Evans et al. 2009; Oliver-Smith 1986).  Glacier avalanches are unpredictable and difficult to plan for.  The 1970 Peru avalanche, for example, was triggered by a massive earthquake that killed an estimated 55,000 people (Ericksen et al. 1970).  Despite attempts to keep people outside the path of potential avalanches, inhabitants often live directly in these hazard zones (Carey 2008; 2010).

Glacial lake outburst floods (GLOFs) have also caused many deaths and much destruction—and with global climate change and retreating glaciers, GLOF risk has escalated worldwide.  As the climate warms, glaciers generally shrink. In many mountains such as the Andes, Himalaya, Alps, Rockies, and elsewhere, the retreat of glacier tongues sometimes allows unstable moraine-dammed lakes to form.  Terminal moraines act as dams for these lakes, but as the lakes swell from rising water levels and the retreating glacial ice tongue, the moraine dam can weaken. Moraine dams that become too weak may crumble under too much pressure from the swelling lake, creating a GLOF. Alternatively, and more commonly, glacial ice from the retreating glacier can crash into lakes, generating giant waves that erode weak moraine dams in a matter of minutes—thereby triggering GLOFs.

Peruvians have experienced the most death and destruction from GLOFs, with nearly 6,000 deaths from three floods between 1941 and 1950.  Since then, Peruvians developed an extraordinarily successful history of GLOF prevention projects in the Cordillera Blanca mountain range.  They conducted lake inventories, classified their degree of danger, and drained and dammed 34 of the most dangerous glacial lakes (Carey 2010; click here for more information and links to citations on this research.

But threats continue today in Peru.  Lake Palcacocha, which caused the 1941 GLOF that killed 5,000 people, again contains a dangerous volume of water.  Lake 513 created a large GLOF in April 2010 that destroyed parts of the city of Carhuaz.  And new lakes form all the time, such as one above Lake Artesoncocha above the massive Lake Parón.  Dangerous glacial lakes also threaten to produce GLOFs in other countries, especially Nepal, Bhutan, and throughout the Himalayan region.

Advancing glaciers can also be hazardous. In the European Alps, advancing glaciers during the Little Ice Age formed ice dams across many valley floors. When too much water was stored behind the ice dam, lakes burst and killed hundreds of people.

Given widespread glacial lake instability and the many vulnerable populations today, it is important to distribute information about glacier hazards internationally.  This is one of the major goals of this website, so please visit the glacier hazards bibliography, the resources and linksK-12 education, and the Andes Research section for more details.

Additionally, you might go directly to these websites for more technical information: