GEOMORPHOLOGY

Shaping landscapes with large floods

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Science  03 Apr 2015:
Vol. 348, Issue 6230, pp. 88-89
DOI: 10.1126/science.348.6230.88-f

A large canyon in Iceland formed by an extreme flooding event

PHOTO: E. R. C. BAYNES ET AL. PNAS 112, 8 (24 FEBRUARY 2015) © 2015 NATIONAL ACADEMY OF SCIENCES

Extreme flood events can wreak havoc on landscapes by carving out features such as large canyons. Baynes et al. consider the multimillennial impact of extreme flood events on the erosion rate of a canyon in Iceland. By dating the canyon surfaces with cosmic rays, they find that three extreme flood events dominated background erosion processes over the past 9000 years. This is due to a transition from an erosion regime driven by abrasion to one in which basalt lava columns were toppled during the large floods. High-impact, short lived events clearly play an overriding role in this locality and may be an underappreciated force for landscape evolution.

Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1415443112 (2015).

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