Over the centuries glaciers have been responsible for many disasters. In the worst affected area, the Cordillera Blanca in Peru, over 32000 people lost their lives in glacier-related disasters during the twentieth century alone. We have already described the perilous combination of glaciers and volcanoes (Chapter 9), but there are other ways in which glaciers can cause havoc, notably by ice avalanches and bursts from glacial lakes. Such phenomena are quite common, but only constitute a hazard when human lives or property are at risk. As populations increase in glacierized mountain regions such as the Andes and the Himalaya, more and more people are becoming exposed to glacier hazards. Furthermore, glacier recession is leading to the development of an increasing number of dangerous glaciers, and mitigation measures are needed to prevent future disasters. In this chapter we focus on the main types of glacier hazard, giving examples of several of the disasters that have befallen mountain communities, explaining how mitigation measures are undertaken in order to prevent future catastrophes.

Although glacier disasters are not usually as dramatic as, for example, a major earthquake or volcanic eruption, the long-term consequences may be severe, especially for countries with fragile economies. Not only may there be loss of human life and property, but economic consequences may include disruption of transport infrastructure, damage or destruction to hydro-electric power schemes and irrigation, and lost production – all of which can run into hundreds of millions of dollars.