Black Rapids Glacier
March 16, 2015
Photographer: Lee Petersen
Summary Author: Lee Petersen
Water backs up behind a natural dam on the Black Rapids Glacier in the Alaska Range. This dam formed from one of three enormous landslides that cover the entire width of the glacier. The landslides were triggered after a 7.9 earthquake in 2002 occurred on the Denali Fault that runs along the length of the glacier. While the debris cover itself is not very thick, a few meters at most, the rock insulates the ice beneath it so there is less melt in the summer months compared to the surrounding ice. The height difference between the top of the debris here and the ice surface where I took this photo from is due almost entirely to the difference in the amount of melt of insulated and non-insulated ice over the previous 11 years. Photo taken June 29, 2013.