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Ryan Lake Viewpoint and Loop Trail
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Ryan Lake Viewpoint and the 1/2-mile loop trail provide a good overview of the
effects and dynamics of the Mount St. Helens May 18, 1980 blast at a point 12
miles north of the crater.
Research on the effects of heat on conifer needles shows that the temperature of
the blast at this site reached an estimated 300 degrees C (572 degrees F). As
much as 6 inches of ash fell here. Two people died in this area on May 18,
1980, as a result of asphyxiation caused by inhaling the ash. Another person
somehow hiked nearly 10 miles farther north and then succumbed, also to
asphyxiation.
Notice that locally trees on the lower parts of the valley wall have been blown
down, whereas those on upper parts of the valley wall still stand. By the time
the blast reached this location, particle segregation within it had created a
heavier "flow" phase, which blew down trees in lower areas, and a lighter
"surge" phase, which left trees standing in higher areas.
Mount St. Helens tephra layers Y, W, and T crop out in cuts
along this trail. Rock of the Spirit Lake pluton was quarried for road
construction at a site on the south edge of the parking area.
Excerpts from:
Pringle, 1993, Roadside Geology of Mount St. Helens National Volcanic Monument
and Vicinity: Washington Department of Natural Resources, Division of Geology
and Earth Resources Information Circular 88
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Mount St. Helens
Meta Lake(south)
Link to: USFS Mount St. Helens National Volcanic Monument