How river rocks round: Resolving the shape-size paradox

G. Domokos, Douglas J. Jerolmack, Andras Á Sipos, A. Török

Research output: Contribution to journalArticle

35 Citations (Scopus)

Abstract

River-bed sediments display two universal downstream trends: fining, in which particle size decreases; and rounding, where pebble shapes evolve toward ellipsoids. Rounding is known to result from transport-induced abrasion; however many researchers argue that the contribution of abrasion to downstream fining is negligible. This presents a paradox: downstream shape change indicates substantial abrasion, while size change apparently rules it out. Here we use laboratory experiments and numerical modeling to show quantitatively that pebble abrasion is a curvature-driven flow problem. As a consequence, abrasion occurs in two well-separated phases: first, pebble edges rapidly round without any change in axis dimensions until the shape becomes entirely convex; and second, axis dimensions are then slowly reduced while the particle remains convex. Explicit study of pebble shape evolution helps resolve the shape-size paradox by reconciling discrepancies between laboratory and field studies, and enhances our ability to decipher the transport history of a river rock.

Original languageEnglish
Article numbere88657
JournalPLoS One
Volume9
Issue number2
DOIs
Publication statusPublished - Feb 12 2014

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Abrasion
Rivers
rocks
Rocks
rivers
Particle Size
Research Personnel
stream channels
particle size
Sediments
researchers
Particle size
sediments
Experiments

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Medicine(all)

Cite this

How river rocks round : Resolving the shape-size paradox. / Domokos, G.; Jerolmack, Douglas J.; Sipos, Andras Á; Török, A.

In: PLoS One, Vol. 9, No. 2, e88657, 12.02.2014.

Research output: Contribution to journalArticle

Domokos, G. ; Jerolmack, Douglas J. ; Sipos, Andras Á ; Török, A. / How river rocks round : Resolving the shape-size paradox. In: PLoS One. 2014 ; Vol. 9, No. 2.
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