Journal
PERMAFROST AND PERIGLACIAL PROCESSES
Volume 22, Issue 2, Pages 107-119Publisher
WILEY
DOI: 10.1002/ppp.706
Keywords
rock glacier; ground-penetrating radar; seismic refraction; electrical resistivity tomography; hydrology
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Funding
- BC-CZO
- US National Science Foundation [NSF-0724960]
- NSF [DEB-0423662]
- University of Colorado Mountain Research Station
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Information about the internal structure of rock glaciers is needed to understand their reaction to ongoing climate warming. Three different geophysical techniques-shallow seismic refraction, ground-penetrating radar (GPR) and electrical resistivity tomography-were used to develop a detailed subsurface model of the Green Lake 5 rock glacier in the Colorado Front Range, USA. Below a thin zone of fine sediments and soils (0.7-1-m thickness; 0-20 k Omega m and 320-370 m s(-1)), a 1-3-m thick zone with low p-wave velocities (790-820 m s(-1)) and high electrical resistivity (20-100 k Omega m) is interpreted as the ice-free, blocky active layer with large void spaces. The data corroborate strong reflections of the GPR signals which travel at this depth at 0.11 m ns(-1). A third layer that extends from depths of 1-3 m to about 5 m is characterised by lower electric resistivities (5-20 k Omega m) and has lower electromagnetic wave velocities (0.65 m ns(-1)), representing unfrozen, finer and wetter sediments. At around 5-m depth, the measured physical parameters change drastically (vp = 3200-3300 m s(-1), 50-150 k Omega m, vGPR = 0.15 m ns(-1)), showing an ice-rich permafrost zone above the bedrock. This model of the internal structure was used to evaluate an existing hydrological flowpath model based on the hydrochemical properties of water outflow from the rock glacier. Copyright (c) 2011 John Wiley & Sons, Ltd.
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