Unstable slopes are an increasing concern in mountainous regions worldwide. Significant expansion of human habitats and transport routes in mountain valleys, melting of alpine permafrost as a consequence of global warming, and exceptional climatic events are amplifying the risks of catastrophic mountain-slope failures. To minimize the effects of such failures, short-term predictions are required for the timely evacuation of vulnerable populations, and medium-term forecasts are needed for the optimum design and construction of barriers that protect lifelines (e.g., roads, railways, and pipelines) and other expensive infrastructure. Moreover, long-term hazard assessments are necessary for prudent land-use planning. These tasks require detailed information on the extent and probable behavior of unstable rock. In this context, the locations and geometries of major fractures and faults are particularly important.