Glacier surge: the view from space.

Glacier surge: The view from space

Glaciers, for the most part, move at a slow and steady pace. But every so often, some glaciers suddenly surge forward and speed up so dramatically that the surfaces of the glaciers break up. Why this occurs is still not known; scientists have had few opportunities to observe these "galloping glaciers' first hand.

When the Hubbard Glacier galloped towards the Gulf of Alaska earlier this year, scientific understanding of the phenomenon didn't exactly surge forward as well, but the event did offer scientists a rare chance to study the mechanics of a glacial surge and its effects on local ecology and geology.

Scientists suspect that the surge began last winter, but the first time they were able to measure a surge velocity on the glacier was in June. In these Landsat Thematic Mapper images the Hubbard Glacier is seen before, left (August, 1985) and after, right (September, 1986) it closed off the Russell Fiord last spring. The ice dam, which made the fiord into a lake, broke down last month, releasing water at a rate of 100,000 cubic meters per second.

Scientists expect that the glacier will once again seal off the fiord in the next ten years, creating a natural laboratory for ecologists studying how the change from a saltwater to a freshwater environment will affect wildlife.