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

Jay Quade, Peter W Reiners, Christa Placzek, Ari Matmon, Martin Pepper, Lujendra Ojha, Kendra Murray

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Abstract

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 M W 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.

Original languageEnglish (US)
Pages (from-to)851-854
Number of pages4
JournalGeology
Volume40
Issue number9
DOIs
StatePublished - Sep 2012

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boulder
seismicity
desert
earthquake
abrasion
hillslope
smoothing
sediment transport
Mars
energy

ASJC Scopus subject areas

  • Geology

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Seismicity and the strange rubbing boulders of the Atacama desert, Northern Chile. / Quade, Jay; Reiners, Peter W; Placzek, Christa; Matmon, Ari; Pepper, Martin; Ojha, Lujendra; Murray, Kendra.

In: Geology, Vol. 40, No. 9, 09.2012, p. 851-854.

Research output: Contribution to journalArticle

Quade, J, Reiners, PW, Placzek, C, Matmon, A, Pepper, M, Ojha, L & Murray, K 2012, 'Seismicity and the strange rubbing boulders of the Atacama desert, Northern Chile', Geology, vol. 40, no. 9, pp. 851-854. https://doi.org/10.1130/G33162.1
Quade, Jay ; Reiners, Peter W ; Placzek, Christa ; Matmon, Ari ; Pepper, Martin ; Ojha, Lujendra ; Murray, Kendra. / Seismicity and the strange rubbing boulders of the Atacama desert, Northern Chile. In: Geology. 2012 ; Vol. 40, No. 9. pp. 851-854.
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