Research About volcanic ash

Posted On: Filed Under: Biological Research

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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Posted On: Filed Under: Biological Research

Effects of eruptions and post-eruptive phenomena on caves and pseudokarst of Mount St. Helens

Beginning June 1980 systematic observations and measurements are documenting the effects of the eruption and post-eruptive events on the caves and pseudokarst of Mount St. Helens. Caves of the Cave Basalt Lava Flow were essentially free of physical impacts by the eruptions, but the biota of some was severely impacted by ashfall. Depending on the local physical geography, some of the caves were severely impacted by post-eruption mudflows.

 

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Distribution of plant detritus and recovery of plants in deposits of May, 1980 eruption of Mount St. Helens

This study seeks to identify types and sizes of plant material and distance and means of deposition in the May 1980 blast of Mount St. Helens. Types of plant material included pieces of moss, leaves, stems, roots, tree branches and trunks. Four types of transport were identified. The debris avalanche deposited plant material 23 km away. Mudflows (lahars) carried material 75 km to the Columbia River. The pressure blast removed vegetation in a 500 km2 area. Pyroclastic flows in conjunction with the plinian column spread plant debris for at least 75 km in a 110o arc to the north and east. These results are being compared with fossilized records of volcanic eruptions worldwide but especially those from Tertiary western United States.

 

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Plant succession and Pacific silver fir (Abies amabilis) mortality

The post-eruption remeasurement of ecology reconnaissance plots installed before 1980 is comprised of five distinct parts. The most basic information was collected on 76 plots relocated during the summer of 1981. Photo points and reconnaissance level plots identical to the pre-eruption plots were installed.

 

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