Home >> News: October 19th, 2010 >> Story
Satnews Daily
October 19th, 2010

Here's Looking @ Earth... Glacier Gander (Imagery—NASA)


[SatNews] Like rivers of liquid water, glaciers flow downhill, tributaries joining to form larger rivers.

But where water would rush, ice crawls. As a result, glaciers gather dust and dirt, and bear long-lasting evidence of past movements. That was the case on Alaska’s Susitna Glacier on August 27, 2009, when the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA’s Terra satellite passed overhead. This false-color image looks similar to an areal photograph, except that vegetation is red. Susitna Glacier’s surface is marbled, combining dirt-free pale blue and dirt-coated dark brown ice. Infusions of relatively clean ice push into the glacier from tributaries flowing from the north. The glacier surface appears especially complex near the center of the image, where ice from a tributary has pushed ice in the main glacier slightly southward.


NASA Earth Observatory image created by Jesse Allen and Robert Simmon, using data provided courtesy of NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team. Caption by Michon Scott.

A photograph taken by the U.S. Geological Survey and archived by the National Snow and Ice Data Center shows an equally complicated surface of Susitna Glacier in 1970, with dirt-free and dirt-encrusted surfaces forming stripes, curves, and U-turns. Susitna Glacier flows over a seismically active area. In fact, a 7.9-magnitude quake struck the region in November 2002, along the previously unknown Susitna Glacier fault. Although geologists surmised that this and other earthquakes left steep cliffs and slopes on the glacier surface, the complex glacial surface apparent in this image results from surges of tributary glaciers.

Glacier surges — typically short-lived events where a glacier moves many times its normal rate — can occur when meltwater accumulates at the base of the glacier. The water provides lubrication that quickens flow. This water may be supplied by meltwater lakes that accumulate on top of the glacier, and melt ponds appear on the Susitna Glacier, in the lower left corner of this image. The nature of the underlying bedrock might also contribute to glacier surges, with soft, easily deformed rock leading to more frequent surges.