High-Energy Megafloods: Planetary Settings and Sedimentary Dynamics

  1. I. Peter Martini1,
  2. Victor R. Baker2 and
  3. Guillermina Garzón3
  1. V. R. Baker

Published Online: 17 MAR 2009

DOI: 10.1002/9781444304299.ch1

Flood and Megaflood Processes and Deposits: Recent and Ancient Examples

Flood and Megaflood Processes and Deposits: Recent and Ancient Examples

How to Cite

Baker, V. R. (2002) High-Energy Megafloods: Planetary Settings and Sedimentary Dynamics, in Flood and Megaflood Processes and Deposits: Recent and Ancient Examples (eds I. P. Martini, V. R. Baker and G. Garzón), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304299.ch1

Editor Information

  1. 1

    Department of Land Resource Science, University of Guelph, Guelph, Ontario, Canada

  2. 2

    Department of Hydrology and Water Resources, University of Arizona, Tucson, AZ 85721–0011, USA

  3. 3

    Dpto de Geodinámica, Fac. de Geología, Universidad of Complutense, 28040 Madrid, Spain

Author Information

  1. Department of Hydrology and Water Resources, University of Arizona, Tucson, AZ 85721–0011, USA

Publication History

  1. Published Online: 17 MAR 2009
  2. Published Print: 10 FEB 2002

ISBN Information

Print ISBN: 9780632064045

Online ISBN: 9781444304299

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Keywords:

  • megafloods;
  • high-energy megafloods - planetary settings and sedimentary dynamics;
  • planetary settings;
  • palaeohydraulics;
  • megafloods and climate;
  • sedimentary process overview;
  • boulder transport;
  • submarine effects of megafloods

Summary

High-energy megafloods usually occur in relatively narrow and deep, confined reaches supplied by large volumes of water. Examples of planetary settings include modern and ancient glacial outburst floods (jökulhlaups) of Iceland, glacial lake spillways south of the Pleistocene Laurentide Ice Sheet, the Channeled Scabland of the north-western USA, mountain lake bursts from central Asia, spillways connecting Pleistocene lake basins in Asia, and the immense outflow channels of Mars. The palaeohydraulic analyses of all these floods indicate that they generate values of stream power per unit area (> 103 W m−2) and bed shear stress (> 103 N m−2) that are two orders of magnitude larger than are typical for floods on large alluvial rivers such as the Amazon and Mississippi. Flood discharges can be comparable to flows in ocean currents, indicating important short-term roles in planetary water and sediment fluxes.

Significant sedimentary processes in the confined reaches for megafloods include streamlining (and related bar formation), scour around obstacles and giant current ripple (dune) formation. Sediment transport involves the entrainment of large boulders and phenomenally high loading of the flow with extremely coarse suspended and wash load. The outflux of high-energy, sediment-charged megafloods from confined continental settings to ocean basins results in hyperpycnal flows, and unusually powerful turbidity currents. These have been documented recently for the Pleistocene Missoula floods that formed the Channeled Scabland. They also were probably very important for the Martian outflow channel floods, which may have exerted the primary trigger for climatic change during Mars' geological history.