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Shifting channels and fluvial processes have reworked much of the lahar deposits
from May 18, 1980, but areas upstream and downstream from the bridge still show
effects of the lahars: mudlines on trees, large boulders, and
downstream-pointing "bayonet" trees. Subsequent storms have
deeply eroded and broadened channels in the lahar deposits.
Excerpt from:
Doukas, 1990,
Road Guide to Volcanic Deposits of Mount St. Helens
and Vicinity, Washington: USGS Bulletin 1859, 53p.
The Muddy River Bridge was destroyed by a lahar on May 18, 1980. The area is
now largely regrown with alders. A painted line about 10 feet above the ground
on the pole adjacent to the parking area shows the maximum height of the lahar
in this area, as determined by mudlines on trees bordering the lahar. Large
boulders of yellowish Tertiary bedrock were transported by the lahar from
outcrops miles upstream and are visible along a trail to the river.
Excerpt 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
Clearwater Overlook (north)
Link to: USFS Mount St. Helens National Volcanic Monument![[large size]](http://vulcan.wr.usgs.gov/Imgs/Jpg/MSH/Images/MSH80_muddy_bridge_devastation_09-23-80.jpg){kind=link}