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Bill Normark Interview: A Huge Glacial Flood that Traveled Far Beneath the Sea

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When ancient glacial Lake Missoula burst through its dam 15,000 years ago, ten times the volume of all the rivers on Earth plunged down the Columbia River drainage. PBS producer Alison Kartevold interviewed USGS scientist Bill Normark on October 31st about where the floodwaters went when they hit the sea. Bill and colleagues discovered Lake Missoula flood deposits in Escanaba Trough about 250 km off the coast of Northern California. The discovery means that part of the ancient floodwaters traveled a distance of at least 1,100 km along the sea floor as hyperpycnally generated turbidity currents before being trapped in the box-canyon topography of Escanaba Trough. In this sense, the turbidity currents left a submarine flood record similar to records left by their terrestrial counterparts, which flowed back up tributaries of the Columbia River. Alison has been working with USGS scientist Richard Waitt to document onshore evidence of the flood. She hopes to broadcast the hour-long program in March 2001. (For more information about Bill's research, see Normark, W.R., and Reid, J.A., 2003, Extensive deposits on the Pacific plate from late Pleistocene North American glacial lake outbursts: Journal of Geology, v. 111, no. 6, p. 617-637 [URL].)

Schematic map showing glacial Lakes Missoula and Columbia
Schematic map showing glacial Lakes Missoula and Columbia Schematic map showing glacial Lakes Missoula and Columbia (blue). About 15,000 years ago, Lake Missoula burst through its glacial dam, sending massive amounts of water and sediment through the Columbia River drainage. Solid arrowed lines (left) show probable submarine pathways for turbidity currents that carried the sediment from the mouth of the Columbia River to Escanaba Trough (red rectangle at southern end of Gorda Ridge). Red circle with cross marks location of the Heceta submarine slide, which occurred about 110,000 years ago. This huge landslide blocked Astoria Channel, whose southern part (dashed red line) became abandoned. Thus, Astoria Channel could not serve as a pathway for the glacial turbidites 15,000 years ago. Offshore bathymetry modified from Grim et al. (1992), and subaerial features from Baker and Bunker (1985). Blue line at upper right indicates edge of the Cordilleran ice sheet.
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African Dust

Bill Normark Interview

Rock Course for Teachers

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Coastal Marsh Die-Back

Southwest Washington Coastal Erosion

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9th International Coral Reef Symposium

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