Ice Age Flood at Red Rock Pass

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Ice Age Flood at Red Rock Pass

About 18,000 years ago, at the peak of the last Ice Age, a single flood from Utah's Lake Bonneville occurred as the lake filled to maximum.  Floodwater began to escape from the enclosed basin here at a low point for the lake at Red Rock Pass.  At first, the lake overflowed slowly as it eroded into loose sediment of an alluvial fan complex shed off the surrounding mountains.   Once started, however, erosional acceleration of the lake waters rapidly cut a channel through the alluvial dam.  The ensuing flood lasted for a couple weeks until floodwaters cut a 120m deep channel across the pass.  Then the flood shut down upon encountering the resistant bedrock below.  

Altogether half the volume (~10,000 km3) of Lake Bonneville, flowing at up to one million cubic m/sec, escaped through the pass.  This image looks south into the Bonneville basin where the spillover channel is narrowest and the incised margins of 120m-tall alluvial fan are clearly visible at top center.  Downstream, flood features similar to those of the Channeled Scabland lie along Idaho's Snake River valley. 





Vineesh V
Assistant Professor of Geography,
Directorate of Education,
Government of Kerala.
https://g.page/vineeshvc

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