Genetic variability of rock glaciers

Abstract

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.

Exposure dating and reinterpretation of coarse debris accumulations (‘rock glaciers’) in the Cairngorm Mountains, Scotland

“…Two main types are widely recognised: glacierderived rock glaciers, formed through the accumulation of melt-out debris on the surface of downwasting valley glaciers; and talus rock glaciers, produced through the downslope deformation of talus accumulations (Clark et al, 1998;Humlum, 1998a;Haeberli et al, 2006). Several studies have indicated that the distribution of active talus rock glaciers is constrained by both temperature and precipitation.…”

Modelling debris transport within glaciers by advection in a full-Stokes ice flow model

“…Kirkbride (1989) proposes that variations in ice mass influx serve to unify a process continuum of deformational geomorphological features of mixed ice and debris composition. The implication of this process continuum is that glaciers can transition between rock glaciers, debris-covered glaciers and clean-ice glaciers through space or time as a result of the varying ice influx (Kirkbride, 1989;Ackert Jr., 1998;Clark et al, 1998). Accordingly, the extent of a debris cover varies inversely with the glacier mass balance, whereby the debris cover extent is governed by transport-dominant conditions (higher ice velocities and lower surface ablation) during periods of positive mass balance and ablation-dominant conditions (lower ice velocities and higher ablation) during periods of negative mass balance (Kirkbride, 2000).…”

Dinámica, evolución y estructura de los glaciares rocosos de los Pirineos

“…Los estudios realizados desde los años 80, mediante sondeos geofísicos, perforaciones, registros térmicos, seguimientos dinámicos en superficie y profundidad, han mostrado la complejidad morfogenética de los glaciares rocosos. Hoy son mayoría los autores que admiten su complejidad, con complicadas relaciones espaciales y genéticas (Whalley y Azzizi, 1994, Hamilton y Whalley, 1995Clark et al, 1998;Krainer, 2002;Berger et al, 2004;Humlum et al, 2007;Ribolini et al, 2007), si bien, los estudios más detallados no muestran estructuras y dinámicas internas asociadas a procesos glaciares.…”