Seismicity and the strange rubbing boulders of the Atacama Desert, Northern Chile

Quade, Jay, Reiners, Peter, Placzek, Christa, Matmon, Ari, Pepper, Martin, Ojha, Lujendra, and Murray, Kendra (2012) Seismicity and the strange rubbing boulders of the Atacama Desert, Northern Chile. Geology, 40 (9). pp. 851-854.

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We found clusters of 0.5–8 t boulders worn to smoothness around their midsections in the Atacama Desert of northern Chile. We suggest that the boulder smoothing is the cumulative result of at least 1 m.y. of rubbing between boulders during earthquakes. ^10Be exposure ages of boulder tops from these fields average ~1.3 m.y., unsurprisingly old given the hyperaridity of the Atacama. During a visit to one major boulder site, we experienced an earthquake that rocked but did not tip the boulders, causing them to rub against each other for about a minute. This MW 5.2 earthquake was centered ~100 km northeast of the site. In the seismically active Atacama, earthquakes of this energy or greater occur about once every four months, suggesting that the average boulder has undergone ~40,000-70,000 h of abrasion over the past 1.3 m.y. This unusual evidence underscores the largely unrecognized role that seismicity probably plays in hillslope sediment transport in the nearly rainless Atacama Desert, and perhaps on other seismically active but now dry worlds like Mars.

Item ID: 22910
Item Type: Article (Research - C1)
ISSN: 1943-2682
Date Deposited: 29 Aug 2012 12:04
FoR Codes: 04 EARTH SCIENCES > 0402 Geochemistry > 040203 Isotope Geochemistry @ 50%
04 EARTH SCIENCES > 0404 Geophysics > 040407 Seismology and Seismic Exploration @ 25%
04 EARTH SCIENCES > 0406 Physical Geography and Environmental Geoscience > 040601 Geomorphology and Regolith and Landscape Evolution @ 25%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970104 Expanding Knowledge in the Earth Sciences @ 100%
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