The distribution, rheology, and origin of rock glaciers, Selwyn Mountains, Canada
PhD: University of Colorado Boulder, 1998.
The distribution, rheology, and origins of rock glaciers in the Selwyn Mountains, Canada, are examined with the intent of constraining rock glacier formation and flow characteristics. This dissertation consists of four papers which have been prepared for publication, including:
- The stratigraphic and altitudinal distribution of rock glaciers in relation to past glacial advances,
- Decadal and millennial velocities of rock glaciers,
- The rheology of rock glaciers, and
- A predictive model of rock glacier location using spatial statistics and a Geographic Information System (GIS).
By considering the relative stratigraphy of rock glaciers to moraines deposited in past glaciations, I identified constraints on rock glacier formation. Rock glaciers located on valley sides distal to late Wisconsin recessional moraines do not contain glacier ice and formed as a result of talus remobilization during the mid-late Holocene. Rock glaciers in cirque basins formed either through the coalescence of lobate, talus rock glaciers or are remnants of late Wisconsin ice.
Process geomorphology and Quaternary geology were integrated in a study of rock glacier velocity and provided a unique comparison of rock glacier flow rates over decadal and millennial timescales. Surveyed velocities, representing a 12-year average, and long-term velocities calculated using lichen ages and rock glacier length for nine rock glaciers were found to be statistically similar, at 0.20 ± 0.11 m/yr.
Using rock glacier velocities, thickness, and surface slope on eight rock glaciers from the Selwyn Mountains, and data from six rock glaciers described in the literature, the relationship between flow parameters was characterized. This is the first synthesis of rock glacier velocity and geometry data into a rock glacier flow law. Results indicate that rock glaciers are characterized by non-linear viscous flow.
The site characteristics of rock glacier accumulation areas in cirque basins were analyzed spatially and statistically using a GIS and used to develop a predictive model of rock glacier location. The model correctly predicts the contents of the cells in 95% of the cases, and was more successful at identifying areas where rock glaciers were absent than present.