Thursday, March 27 - USGS officials issued
a Hazards Watch to public officials. At 11:20AM an observer in an Army National
Guard reconnaissance plane reported seeing a hole in the icecap near the summit
and a gray streak extending southeast from the hole.
At approximately 12:30 people near the volcano reported hearing a loud "boom,"
which probably marked the first sighted explosion. Mike Beard, a Portland radio
reporter, was flying over the cloud-shrouded mountain and reported seeing "ash
and smoke spewing out, a little like smoke out of a chimney."
At 2:00PM UW seismologists recorded the second strongest earthquake to date
(a magnitude 4.7). Following the earthquake a black plume was observed to rise
about 7,000 feet above the volcano.
Earthquakes occurred so frequently that one University of Washington seismologist
was quoted as saying the instruments had detected earthquakes so often that it
"was difficult to tell where one ends and another begins."
Following the explosion a crater about 200 to 250 feet wide was reported near
the summit. A series of cracks criss-crossed the summit from east to west and
volcanic ash had darkened snow in a band across the crater and down the volcano's
southeast slope.
Concerns over the increased potential for large rock avalanches (as a result
of the cracks forming near the summit) and widespread flooding (due to heat from
the volcano melting snow and ice) prompted the evacuation of hundreds within a
15 mile radius from the volcano.
Among these were USFS employees and their families at the Pine Creek Ranger
Station at the head of Swift Reservoir, 300 or so loggers from three Weyerhaeuser
camps, and 20 employees from the state fish hatchery about 30 miles downstream
on the North Fork Toutle River.
Skamania County Sheriffs also evacuated about 45 people, mostly scientists
and reporters, from the Spirit Lake area while Cowlitz County Sheriffs evacuated
those further downstream on the North Fork Toutle River. Skamania County Sheriffs
established a roadblock on State Route 504 approximately 7 miles from the volcano.
By evening, however, USGS hydrologists had determined that there was no rise in
streams draining the volcano.
Additional scientists arrived in the evening to study the continued seismic
activity, measure possible ground deformation on the volcano, determine the chemical
composition of volcanic ash and gases, and to monitor heat emissions, water levels
and water quality.
Pacific Power and Light began drawing down all three reservoirs on the Lewis
River on the south side of the volcano to accommodate flooding and mudflows from
a possible eruption. Company representatives stated that the dams should withstand
the most severe earthquakes expected in the area. The Oregon Museum of Science
and Industry installed a seismograph exhibit with an expert on duty to field questions.
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A Portland radio reporter described the first sighted explosion: "ash and
smoke spewing out, a little like smoke out of a chimney." USGS photo courtesy
of Dan Miller.
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