35-YEAR PHOTOGRAPHIC RECORD OF AN ADVANCING ROCK GLACIER IN THE LAKE LOUISE AREA, BANFF NATIONAL PARK, ALBERTA

Three rock glaciers situated on the flank of Mt. Aberdeen in Banff National Park in Alberta have been advancing for the past 100 years. The rock glaciers are tongue-shaped, about 150 m wide and 300 to 600 m long, and composed of angular blocks of limestone, quartzite, and shale up to 3 m in size. No ice is visible. The rock glaciers do not emanate from glacier ice and presumably are of the ice-cemented variety, also known as talus-derived rock glaciers. All exhibit the characteristics of active rock glaciers. They are oriented perpendicular to the valley of Victoria Glacier upstream of Lake Louise, and are encroaching upon and burying parts of the left-lateral moraine of that glacier.

Rates of advance prior to 1974 can be estimated using an oblique photograph of Victoria Glacier taken by Sherzer in 1902, and the earliest Government of Canada aerial photographs of the area, taken in 1947. Rates of advance were estimated by Osborn (Cdn. Jr. Earth Sci., 1975) to average 0.7 to 0.8 m/yr for the period 1902-1974 and and 0.3 to 0.6 m/yr for the period 1947-1974. Beginning in 1974 a series of photographs has been taken of the front of the downstream (northeastern) rock glacier from the same point. Images from 1974, 1980, 1986, 1995, and 2009 show that the front has continued to advance, almost to the crest of the lateral moraine. The base of the front was two planimetric meters from the moraine crest in 1974, and in 2009 is about 0.5 m, yielding an average rate of advance of approximately 4 cm/yr. These data show that the rock glacier continues to advance even as the glaciers in the Canadian Rockies retreat rapidly, but that the rate of advance has declined by an order of magnitude. The decline may be due to a gradual decrease in volume of interstitial ice resulting from ongoing warming.