99 Geomorphology (Posters)

Monday, 1 November 2010
8:00 AM - 6:00 PM
Hall D

HYDROLOGICAL CHARACTERISTICS OF ROCK GLACIERS: SAN JUAN MOUNTAINS, CO, USA

Paper number: 99-2
Program: Technical Sessions
Time: 8:00 AM – 6:00 PM

Authors

Abstract

Rock glaciers serve dual roles as debris transport systems and principal sinks for rock and ice in alpine regions. The mixtures of rock debris and matrix/core ice that constitute a rock glacier are characteristically insulated by a layer of several meters of rock debris in which seasonal snow and ice can accumulate. The volume of water and ice stored within the upper layer of rock debris fluctuates as a result of rates of snowfall accumulation, seasonal weather fluctuations, and rates of debris accumulation. The upper layer of rock debris, characteristic of rock glaciers, makes them sensitive to climatic changes that occur in alpine environments, and, thus, they may serve as surrogate indicators for climatological conditions, particularly at latitudes and elevations below those of glaciers. The amount of snow and ice that can be incorporated in the upper layer is subject to fluctuations in the yearly precipitation over the mountain range in which a rock glacier is located. Some factors that affect orographic snow cover are temperature, aspect, cloud cover, and wind. Measurements of amounts of wind-blown dust suggest that dust accumulations can shorten the melting time for accumulations of snow on the surface of the rock glacier.

To understand the hydrologic characteristics of the upper layer and its response to climatic changes, we used GPR surveys to collect data in centrally located furrows on rock glaciers in the San Juan Mountains and Stella modeling. Meltwater from snow pack was observed infiltrating the upper layer of each rock glacier along the bottom of the furrow and reappearing down slope at the terminus of the furrow. GPR profiles suggest that the water pathway, which changes course within the upper layer, is not controlled by the furrow. Induction conductivity has the flowing water penetrating the upper layer and flowing along the interface with the frozen matrix until reemerging at the terminus of the furrow. The Stella model highlights the interaction between inputs, pathways and potential sinks in the rock glacier.