Genetic variability of rock glaciers

Rock glaciers, common in many alpine and polar regions, have poorly understood internal structure, dynamics, and origins. A renewal of interest in the climatic and geomorphic significance of these striking landforms has served to intensify a long‐standing controversy surrounding the genesis of rock glaciers. The controversy, which began more than 30 years ago, has resolved into two primary viewpoints. One holds that rock glaciers form through a continuum of glacial to periglacial processes and encompass features that vary from debris‐covered glaciers to slightly remobilized talus or till. The opposing view holds that all rock glaciers are exclusively features of creeping permafrost, genetically distinct from glaciers. Several factors have prolonged this debate: (1) sparse direct observations of internal composition and processes of ice formation; (2) few long‐term measurements of rock glacier deformation; (3) difficulties in establishing geophysical, geochemical, or petrographic methods that unequivocally distinguish between ice of glacial and periglacial origins; (4) difficult access and remote locations of most rock glaciers; and (5) often arbitrary terminological distinctions between “glacial” and “periglacial” processes. Results from several recent studies, some presented in this volume, demonstrate conclusively that at least some rock glaciers are glacigenic, making untenable the view of rock glaciers as exclusively periglacial. This conclusion indicates that several previously held concepts of rock glacier dynamics and development should be re‐evaluated. In addition, it highlights the need for researchers to move beyond taxonomic arguments, and to improve understanding of fundamental aspects of rock glaciers such as climatic sensitivity, geochemistry, hydrology, dynamics, structure, mass balance, and genetic and spatial variability.