Geologische Naturgefahren

High mountain hazards

Gravity tends to level out the Earth's surface. High mountain areas therefore show active morphodynamics with frequent mass relocation processes. Most of the time, such processes occur at slow rates or have a limited spatial extent. Though causing some damage when interfering with people or assets, strategies to manage such risks have proved successful in most of the world's mountains.

This - on the broad scale steady - relocation of mass from higher to lower areas ensures a dynamic equilibrium of mountain geosystems. Sometimes, however, this equilibrium is disturbed by forces from outside the system. Some of these forces act for a few minutes only - e.g. earthquakes - others for decades and centuries. Climate change belongs to the latter category. High-mountain geosystems react highly sensitive to climate signals like fluctuations of temperature or precipitation. Many glaciers in the world's mountain areas are in a stage of retreat. The tongues often leave behind an undulating mass of till, still containing some quantity of ice. Such places are favourable for the development of glacial lakes. Some of these lakes are prone to sudden drainage, e.g. by hydrostatic failure or retrogressive erosion of the dam, or by flood waves triggered by falling ice or rocks. Glacial Lake Outburst Floods (GLOFs) may develop into powerful debris flows with long travel distances. Since the glacial lakes are far up in the mountains and events occur at long intervals, the population is often not prepared and the natural processes evolve into disasters.