ROCKSLIDES IN MACKENZIE MOUNTAINS, NORTHWEST TERRITORIES, CANADA

The inventory of large rockslides/rock avalanches within the Mackenzie Mountains, Northwest Territories, Canada, has not been updated since the classic work of G.H. Eisbacher in the late 1970s. Using World Imagery from ESRI and satellite images from Planet, we have recorded the locations of large rockslides/rock avalanches within the entire Mackenzie Mountains and are describing selected rockslides from high-resolution aerial photographs. The records tend to accumulate around the NW-end and the SW-end of the Mackenzie Mountains, while large bedrock instabilities are sparse in the central part. This regional pattern coincides with the distribution pattern of local seismic activity. The records also tend to occur around local faults and in limbs of folds. More than 75% of the records originate in Cambrian to Devonian carbonate-dominant formations; relatively weak layers and/or tectonically weakened zones within these formations are thought to be the main factor in massive failures. Geomorphological features of sliding surfaces indicate a range of failure modes as different stages of catastrophic rock slope failure and particular failure modes are also observed. Through comparisons between rockslides in similar geologic settings, the ongoing study will shed light on puzzles that persist in the failure mechanisms of some well-known massive rock slope failures in the Mackenzie Mountains (e.g. Avalanche Lake and Rockslide Pass) as well as provide insights on failure modes within the sedimentary-dominant Canadian Foreland Belt and related carbonate sequences.