| Summary: | Includes bibliographical references. Includes illustrations and maps. Electrical depth sounding, seismic refraction profiling, and laboratory electrical and seismic measurements are used to describe the occurrences and types of permafrost and depth to bedrock in the Dry Valley region, Antarctica. In topographic depressions, especially near lakes, confining permafrost is thin or absent; whereas, in the uplands and on moraines it may be thick (>1,000 m). Areas where confining permafrost is thin or absent are: Don Juan Pond, Don Quixote Pond, Lake Bonney area, Lake Vanda area, Walcott Glacier, and near Lake Fryxell. Areas where it is thick are: Lake Vida, Lake Miers, and the shore of New Harbor. Laboratory measurements indicate resistivities of saturated rocks, soils, and saline solutions increase exponentially with decreasing temperature ( T ) according to an equation of the form = a e b/T. Discontinuities in the - T curve appear to be caused by a final liquid to crystalline phase transition experienced by the contained fluid. The shape of the - T curve is a function of the crossectional area of unfrozen water lying between the matrix grains and ice crystals. The unfrozen water forms a network through which current may flow until extremely low temperatures are reached. Abnormally high compressional wave velocities for ice (4,293 meters per second) were recorded on Lake Vida. Laboratory measurements on prepared ice-sand mixtures yielded velocities up to 4,567 meters per second, suggesting that the high velocity was due to the lake ice containing close to 30 percent sand and gravel. The velocity of a saturated, low-porosity rock decreases with decreasing temperature, whereas the velocity of a porous, fractured rock appears to increase with decreasing temperature. M.S. (Master of Science)
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