Mt St Helens Images - The deposits at the mouth of the Toutle and in the Cowlitz River

The distal lahar deposits

The lower reaches of the Toutle and Cowlitz Rivers as well as a section of the Columbia River were filled with lahar deposits after the 1980 eruption. It was imperative that these be dredged quickly to restore navigation (some 20 ocean-going vessels were trapped upstream on the Columbia). The products of this dredging are still visible in spoil piles bordering I-5 along the Cowlitz.

Photo by James Maynard © 2011 - free use with attribution [Full-size, jpeg format]

Lahar sedimentation in the Columbia River from Schuster 1981

Source: Schuster, H., 1981, Effect of the eruptions on civil works and operations in the Pacific Northwest, in The 1980 Eruptions of Mount St. Helens, Washington, edited by P. W. Lipman and D. R. Mullineaux: U.S. Geological Survey Professional Paper 1250, p. 701-718. 

 

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