High-frequency rock temperature data from hyper-arid desert environments in the Atacama and the Antarctic Dry Valleys and implications for rock weathering |
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| Authors: | Christopher P McKay Jamie L Molaro Margarita M Marinova |
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| Institution: | aSpace Science Division, NASA Ames Research Center, Moffett Field CA 94035, United States;bDivision of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, United States |
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| Abstract: | In desert environments with low water and salt contents, rapid thermal variations may be an important source of rock weathering. We have obtained temperature measurements of the surface of rocks in hyper-arid hot and cold desert environments at a rate of 1/s over several days. The values of temperature change over 1-second intervals were similar in hot and cold deserts despite a 30 °C difference in absolute rock surface temperature. The average percentage of the time dT/dt > 2 °C/min was ~ 8 ± 3%, > 4 °C/min was 1 ± 0.9%, and > 8 °C/min was 0.02 ± 0.03%. The maximum change over a 1-second interval was ~ 10 °C/min. When sampled to simulate data taken over intervals longer than 1 s, we found a reduction in time spent above the 2 °C/min temperature gradient threshold. For 1-minute samples, the time spent above any given threshold was about two orders of magnitude lower than the corresponding value for 1-second sampling. We suggest that a rough measure of efficacy of weathering as a function of frequency is the product of the percentage of time spent above a given threshold value multiplied by the damping depth for the corresponding frequency. This product has a broad maximum for periods between 3 and 10 s. |
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| Keywords: | Rock Rock weather Rock weathering Surface weather Grain-scale Temperature Thermal Stress Stress gradient Thermal shock Thermal stress fatigue Cracking Flaking Spalling Antarctica Beacon Fryxell Dry Valleys Atacama Desert Arid Damping depth |
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