Windy Ridge is one of the best places to get an overview of the area devastated
by the 1980 eruption. The landscape is littered with sand and gray rocks from
that event. Deposits of the debris avalanche are visible to the west. These
include the lower parts of The Spillover, where the debris avalanche traveled up
over Johnston Ridge and into the South Coldwater area.
The blast stripped most of the vegetation and some soil from many of the older
bedrock surfaces, revealing to geologists and visitors previously hidden
chapters in the geologic history of the area.
Rockfalls from the crater walls stir up ash clouds that curl over the edges of
the crater rim, especially in late summer. A faint bluish-white volcanic gas
plume is often visible rising from the Lava Dome, and sometimes fumaroles
or clusters of fumaroles can be seen there.
A walk up the steps on the hill north of the parking lot provides a better view
of the devastated area adjacent to Spirit Lake. The 1980 debris avalanche
roared over part of a ridge that protrudes into Spirit Lake from the north and
carried all the downed trees off the slope and into the lake, leaving a distinct
trimline. The avalanche also displaced water from Spirit Lake, creating a giant
wave that carved a slosh line along the shore. Many of the logs that now float
in the lake were carried in by this wave; others have been eroded off the slopes
since than. Wind moves the logs to different locations on the lake.
The water level of Spirit Lake is maintained at about
3,406 feet (1,038 meters) by
draining water through a gravity-feed tunnel completed in 1985.
The 2,500-feet
(762 meters) -long tunnel was cut
through Harrys Ridge (named form Harry Truman, the
Spirit Lake resident who refused to leave his home and was killed by the May 18,
1980, eruption) to South Coldwater Creek. The portal is just visible about
midway along the western shore of the lake. Had the lake level not been
stabilized, its dam probably would have been breached, possibly causing
catastrophic floods in the Toutle River.
-- 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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