Book excerpt: Mass movement of rocks in high mountains can severely injure the population and damage man-made structures in these areas. This book focuses on the understanding of the mechanisms of rockslides and rockfalls using a quantitative approach. The range and velocity of these hazards are calculated to serve as a basis for evacuations and other preventive measures. Examples from four continents illustrate the necessity of this kind of information. The book contains a wealth of information for practitioners and scientists working in the field of catastrophe prevention.