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Posted on 10/10/2004 1:29:06 PM PDT by Michael Goldsberry
MOUNT ST. HELENS, Wash. - Mount St. Helens vented a new column of steam Sunday, a lazy plume that rose out of the crater of the snow-dusted volcano.
The billow of steam rose from an area where a large upwelling or bulge of rock has been growing on the dome-shaped formation of rock in the crater. The plume rose several hundred feet above the 8,364-foot volcano, and light wind slowly blew it toward the south and southeast.
The venting reminded scientists of the volcano's activity 20 years ago, when it built the dome following its catastrophic 1980 eruption.
"It's a view very, very reminiscent of the years in the 1980s during dome-building and a few years after when the system was hot and water was being heated and vapor was rising and steam clouds were forming," said Willie Scott, a geologist with the U.S. Geological Survey (news - web sites).
The plume appeared to be mostly steam, and scientists said any volcanic ash that was included was probably from past eruptions during the 1980s.
The venting probably was produced by a combination of rain water percolating down to hot rocks and volcanic gas coming from deeper levels, scientists said.
The steam emission followed an increase in earthquake activity over the previous two days, with quakes of magnitude 2.4 occurring every two minutes until Sunday, when the vibrations were more frequent but weakened to magnitude 1 or less.
"What has been peculiar about these earthquakes is that there seems to be a disproportionate number of them that are uniform in size," said seismologist Tony Qamar at the University of Washington's seismic lab in Seattle.
It indicates that pressure in the system is very uniform, which may suggest magma is constantly moving upward, he said. "The pressure will build up, the rock will break, and then you'll get an earthquake," Qamar said.
"Exactly where the magma is, since we don't have visuals, we just can't say," said Jeff Wynn, the U.S. Geological Survey's chief scientist for volcano hazards at Vancouver.
Seismic activity on Saturday was equal to or higher than levels during the Oct. 5 eruption that sent a thick gray cloud thousands of feet into the air and dusted some areas northeast of the volcano with gritty, abrasive ash.
Geologists do not anticipate anything similar to the May 18, 1980, blast that killed 57 people, blew 1,300 feet off the top of the peak and covered much of the inland Pacific Northwest with ash.
Since Sept. 23, thousands of small earthquakes have shaken the peak in the Cascade Range. The volcano vented clouds of steam carrying small amounts of old volcanic ash each day from Oct. 1 through Oct. 5. Thousands of people were evacuated from areas around the mountain on Oct. 2.
Author correction: JOSEPH B. FRAZIER
The current rate of intrusion by magma under the crater's floor is now estimated at TWICE the rate it was in the 1980s dome building events. The lack of seismicity only shows that there is little rock breakage going on while the magma moves upward. Fireworks eventually.
From the CVO:
Additional analysis of lidar and photographs of the intensely uplifting area on the south side of the lava dome suggests that the total volume change represented by the deformation between late September and October 6 is about 16 million cubic meters (21 million cubic yards). The average rate of change is about 2 million cubic meters per day (2.6 million cubic yards per day). If this figure represents the rate of intrusion of magma into shallow levels of the dome and(or) underlying crater floor, it is an intrusion rate about twice that measured during dome-building eruptions at Mount St. Helens in the 1980s. Cartographers with the USGS office in Denver are working to develop precise volume change estimates for the uplifted area from stereo airphotos acquired between 1 and 5 October.
Now think about the scale of this: A standard dump truck carries 12 cubic yards of soil. That's one Hell of a lot of uplift going on!
I'm beginning to wonder if this indicates that there may be a molten lava eruption coming, rather than simply an explosive eruption. Mount St. Helens has had this in the past, though of course the explosive eruptions are more common.
Thank God this isn't a vanity.
Yup. That's Mount St. Helens - the WonderBra of the Cascade Range...
10-10-04
Mount St. Helens Shoots Out More Steam
10-09-04
"Loaf" rises higher than Mount St. Helens dome
10-08-04
Predictions For Mount St. Helens Change! (Scientist now predict another 1980-type blast)
10-07-04
Mount St. Helens Volcanic Eruptions: 1980 vs. Now (Great History)
Mount St. Helens' Crater Floor Rising
10-05-04
Mount St. Helens Vents Biggest Steam Plume Yet Along With Cloud of Ash (Tuesday Morning)
Mount St. Helens going off again?
10-03-04
Mount St. Helens Releasing Green House gasses
Mount St. Helens evacuated; substantial eruption "imminent"
10-02-04
U.S. Warns of Big Mount St. Helens Blast
U.S. Raises Alert for Mount St. Helens [LIVE THREAD]
Mount St. Helens Erupts After 18 Years
Mount St. Helens is not finished, earthquake activity resumes
Steam eruption under way at Mount St. Helens
Mount St Helens steam cloud (Update: Second eruption imminent; area evacuation reported)
09-30-04
Experts Predict Mount St. Helens Eruption
09-29-04
'Volcano Advisory' Issued for Mount Saint Helens
USGS raises eruption alert on Mount St. Helens
Mount St. Helens VolcanoCam
Lava dome growing in Mount St. Helens
09-27-04
Global Cooling ; Mount St. Helens showing the formation of a new glacier
09-26-04
Mount St. Helens Notice of Volcanic Unrest
Mount St. Helens Notice of Volcanic Unrest
09-24-04
Cascade Range Current Update (Mount St. Helens volcano)
Oregon Ping
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Love that steam ~ Bump!
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