Effects of airfall tephra on forests northeast of Mount St. Helens

The May 18th, 1980 eruption of Mount St. Helens deposited tephra over a very large area of forest land in Southwest Washington. Tephra affected forest stands primarily by covering the foliage. Most tephra originally deposited is now on the forest floor; however, much of the finest deposits were retained by the foliage and still persist in the crowns of many trees.


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