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ABSTRACT: Radar Remote Sensing of Glacial Features, Malaspina Glacier, Alaska

Bruce F. Molnia, John E. Jones

Two types of radar investigations were conducted at Malaspina glacier, the largest piedmont glacier lobe in North America. Digital x-band side-looking airborne radar (SLAR) data were collected to image surface features; ice-surface, ice-penetrating radar was employed to measure ice thickness and to identify the configuration of subglacial bed rock. SLAR revealed a complex pattern of surface backscatter responses related to three types of channellike features on the glacier surface, which mimic the configuration of its underlying bed rock. The features resemble (1) glacially eroded valleys with cirque-like indentations, (2) dendritic stream valleys, and (3) a greater than 40-km-long, arcuate, east-west lineament that corresponds to the Fairweather fault. Field examinations of the three types of features were made to determine relief, slope, and other conditions. The channel-like features had elevations as much as 40 m lower than adjacent high areas and were characterized by fewer crevasses, minimal surface relief, a sediment veneer, and standing and running water. Hundred-m-spaced ice-penetrating radar soundings showed that the ice thickness over these low areas is much greater than over adjacent highs.

About 50 ice-thickness measurements were made elsewhere on the glacier. The maximum ice thickness measured exceeded 850 m, whereas the minimum thickness was less than 150 m. Comparison of ice-thickness measurements and ice-surface elevations at each site suggests that the Malaspina Glacier occupies a deep basin or series of basins extending well below sea level.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990