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

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


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. (super 10) Be exposure ages of boulder tops from these fields average approximately 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 M (sub W) 5.2 earthquake was centered approximately 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 approximately 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.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 40
Serial Issue: 9
Title: Seismicity and the strange rubbing boulders of the Atacama Desert, northern Chile
Affiliation: University of Arizona, Department of Geosciences, Tucson, AZ, United States
Pages: 851-854
Published: 20120718
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 18
Accession Number: 2012-073276
Categories: Quaternary geology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: With GSA Data Repository Item 2012239; accessed on July 26, 2012
Illustration Description: illus. incl. 1 table, sketch map
Source Medium: WWW
S24°00'00" - S23°00'00", W69°40'00" - W69°19'60"
Secondary Affiliation: James Cook University, AUS, AustraliaHebrew University, ISR, Israel
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201238
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