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Article - Catastrophic flood at Grand Canyon 165K years ago

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  • Todd S. Greene
    From: http://dx.doi.org/10.1016/j.yqres.2005.09.006 ... Peak discharge of a Pleistocene lava-dam outburst flood in Grand Canyon, Arizona, USA by Cassandra R.
    Message 1 of 1 , May 13, 2006
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      "Peak discharge of a Pleistocene lava-dam outburst flood in Grand
      Canyon, Arizona, USA"
      by Cassandra R. Fenton, Robert H. Webb, and Thure E. Cerling
      Quaternary Research (March 2006 issue)


      The failure of a lava dam 165,000 years ago produced the largest
      known flood on the Colorado River in Grand Canyon. The Hyaloclastite
      Dam was up to 366 meters high, and geochemical evidence linked this
      structure to outburst-flood deposits that occurred for 32 kilometers
      downstream. Using the Hyaloclastite outburst-flood deposits as
      paleostage indicators, we used dam-failure and unsteady flow
      modeling to estimate a peak discharge and flow hydrograph. Failure
      of the Hyaloclastite Dam released a maximum 11 × 10^9 cubic meters
      of water in 31 hours. Peak discharges, estimated from uncertainty in
      channel geometry, dam height, and hydraulic characteristics, ranged
      from 2.3 to 5.3 × 10^5 cubic meters per second for the Hyaloclastite
      outburst flood. This discharge is an order of magnitude greater than
      the largest known discharge on the Colorado River (1.4 × 10^4 cubic
      meters per second) and the largest peak discharge resulting from
      failure of a constructed dam in the USA (6.5 × 10^4 cubic meters per
      second). Moreover, the Hyaloclastite outburst flood is the oldest
      documented Quaternary flood and one of the largest to have occurred
      in the continental USA. The peak discharge for this flood ranks in
      the top 30 floods (>10^5 cubic meters per second) known worldwide
      and in the top ten largest floods in North America.
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