These images show an unusual event that happened on the coast of Alaska, when a glacier slid down far enough to suddenly block off a fiord (a long, narrow inlet of the sea) from the rest of the bay and ocean. This natural ice dam held for four and a half months, raising its level more than 25 meters.

When a glacier is a dam

Yakutat Bay lies at the base of Alaska's panhandle. Russell Fiord is the narrow body of saltwater connected to the bay and extending southeast. The Hubbard Glacier lies where Russell Fiord meets the bay.

In May 1986, the Hubbard Glacier surged down from the mountains, blocking the outlet of Russell Fiord and creating "Russell Lake." All that summer the new lake filled with runoff; its water level rose 25 meters, and the decrease in salinity threatened its sea life.

Around midnight on October 8th the dam began to give way. In the next 24 hours an estimated 5.3 billion cubic meters of water gushed through the gap, and the fiord was reconnected to the ocean at its previous level.

The fiord could become dammed again, and perhaps permanently. If this happens, the fiord could overflow its southern banks and drain through the Situk River instead, threatening trout habitat and a local airport.

Click here to read a short journal article a written by two USGS scientists explaining this phenomenon.

References

Walker, K., M., and Zenone, C., 1988, Multitemporal Landsat Multispectral Scanner and Thematic Mapper Data of the Hubbard Glacier Region, Southeast Alaska: Photogrammetric Engineering and Remote Sensing, vol. 54, no. 3, March, p. 373-376. (Click here to read this article.)

Eliot, John, L., and Johns, Chris, 1987, Glaciers on the Move: National Geographic Magazine, vol. 171, no. 1, January, p. 106-119.

Satellite images

LT5062018008521910 (Landsat 5 TM, 7 August 1985)

LT5062018008625410 (Landsat 5 TM, 11 September 1986)

Maps

U.S. Geological Survey, 1986 (compiled in 1973, revised in 1986), State of Alaska; Map B (east half): scale 1:1,584,000.

U.S. Geological Survey, 1982 (1959, limited revisions 1982), Yakutat, Alaska-Canada: scale 1:250,000 (spliced to the Mt. St Elias map).

U.S. Geological Survey, 1983 (1959, limited revisions 1983), Mt. St. Elias, Alaska-Canada: scale 1:250,000 (spliced to the Yakutat map).

How to cite this article

Campbell, Robert Wellman, ed. 1997. "Hubbard Glacier, Alaska, 1985, 1986." Earthshots: Satellite Images of Environmental Change. U.S. Geological Survey. http://earthshots.usgs.gov. This article was released 14 February 1997.