This book is dedicated to Professor Kolumban Hutter of the Darmstadt Univer sity of Technology on the occasion of his 60th birthday on 22 January 200l. Professor Hutter graduated in Civil Engineering from the ETH Zurich, and then worked in industry-related consulting at the Institute of Mechanics and the Laboratory of Hydraulics and Soil Mechanics at the ETH, before embark ing on a PhD in Theoretical and Applied Mechanics in Cornell University. He duly completed his PhD under the supervision of Professor Y. H. Pao, working in the field of the electrodynamics of continuous media. After his PhD, Professor Hutter returned to Europe where he worked as a senior scientist at the Labor atory for Hydraulics, Hydrology and Glaciology, ETH Zurich, being involved in glacier flow, physical limnology, avalanche research and granular media. At the same time he maintained scientific contact with the Mechanics Institute of the Vienna University of Technology. In both European cities he received a habil itation degree: In Vienna for Mechanics, in Zurich for Theoretical Glaciology and Limnology. Since 1987 Professor Hutter has been the successor to Professor Becker at the Department of Mechanics, Darmstadt University of Technology. Professor Hutter's work has always been relevant to reallife, and a feature of the man is his attention to experiments and matching theory. He has built up an internationally respected laboratory in Darmstadt which concentrates on both experimental and theoretical aspects.