Mt. St. Helens Update 10/7/04
Posted: Thu Oct 07, 2004 12:02 pm
U.S. Geological Survey, Vancouver, Washington
University of Washington, Pacific Northwest Seismograph Network, Seattle, Washington
Volcanoes in the Cascade Range are all at normal levels of background seismicity except for Mount St. Helens. See Mount St. Helens update below.
Other volcanoes include Mount Baker, Glacier Peak, Mount Rainier, and Mount Adams in Washington State; Mount Hood, Mount Jefferson, Three Sisters, Newberry, and Crater Lake, in Oregon; and Medicine Lake, Mount Shasta, and Lassen Peak in northern California.
USGS Cascades Volcano Observatory, the Pacific Northwest Seismograph Network at the University of Washington, and the USGS Northern California Seismic Network and Volcano Hazards Team in Menlo Park, California, monitor the major volcanoes in the Cascade Range of northern California, Oregon, and Washington.
Mount St. Helens Update, October 7, 2004, 6:50 a.m, PDT
Current status is Volcano Advisory (Alert Level 2); aviation color code ORANGE
The low rate of seismic activity of the past day increased slightly overnight. Earthquakes are presently occurring at a rate of about 1 to 1.5 per minute with maximum magnitudes of about 1.0. Late yesterday afternoon scientists were able to get brief views of the vents and the area of intense uplift on the south side of the 1980- 86 lava dome. They saw only weak puffs of steam coming from vents. They were able to confirm that the top of the area of intense uplift is at or slightly above the highest point on the lava dome, which suggests that some uplift has occurred during this period of low seismicity. They were also able to observe areas affected by the small lahars that spilled out of the crater and onto the Pumice Plain during the rainstorm in the early morning of 6 October. Lahars flowed a short distance toward both Spirit Lake and the North Fork Toutle River.
Today, field crews will continue to harden GPS sites for the approaching winter, do a gas-sensing flight, take thermal images of the dome and crater floor and make geological observations.
As a result of the intense unrest of the past 11 days, we infer that magma is at a very shallow level. During times of unrest, Mount St. Helens and similar volcanoes elsewhere typically go through episodic changes in level of unrest over periods of days to weeks, or even months. Such changes are in part driven by variations in the rate of magma movement. We expect fluctuations in the level of unrest to continue during coming days. Escalation of unrest could occur suddenly and perhaps lead to an eruption with very little warning. There may be little time to raise the alert level before a hazardous event occurs. Therefore, we continue to monitor the situation closely and will issue additional updates and changes in alert level as warranted.
Wind forecasts from the National Oceanic and Atmospheric Administration (NOAA), combined with eruption models, show that winds this morning are southwesterly and any ash will drift to the northeast.
Press conferences will continue to be held at the Headquarters office of the Gifford Pinchot National Forest. The morning press conference is at 9:30 AM.
University of Washington, Pacific Northwest Seismograph Network, Seattle, Washington
Volcanoes in the Cascade Range are all at normal levels of background seismicity except for Mount St. Helens. See Mount St. Helens update below.
Other volcanoes include Mount Baker, Glacier Peak, Mount Rainier, and Mount Adams in Washington State; Mount Hood, Mount Jefferson, Three Sisters, Newberry, and Crater Lake, in Oregon; and Medicine Lake, Mount Shasta, and Lassen Peak in northern California.
USGS Cascades Volcano Observatory, the Pacific Northwest Seismograph Network at the University of Washington, and the USGS Northern California Seismic Network and Volcano Hazards Team in Menlo Park, California, monitor the major volcanoes in the Cascade Range of northern California, Oregon, and Washington.
Mount St. Helens Update, October 7, 2004, 6:50 a.m, PDT
Current status is Volcano Advisory (Alert Level 2); aviation color code ORANGE
The low rate of seismic activity of the past day increased slightly overnight. Earthquakes are presently occurring at a rate of about 1 to 1.5 per minute with maximum magnitudes of about 1.0. Late yesterday afternoon scientists were able to get brief views of the vents and the area of intense uplift on the south side of the 1980- 86 lava dome. They saw only weak puffs of steam coming from vents. They were able to confirm that the top of the area of intense uplift is at or slightly above the highest point on the lava dome, which suggests that some uplift has occurred during this period of low seismicity. They were also able to observe areas affected by the small lahars that spilled out of the crater and onto the Pumice Plain during the rainstorm in the early morning of 6 October. Lahars flowed a short distance toward both Spirit Lake and the North Fork Toutle River.
Today, field crews will continue to harden GPS sites for the approaching winter, do a gas-sensing flight, take thermal images of the dome and crater floor and make geological observations.
As a result of the intense unrest of the past 11 days, we infer that magma is at a very shallow level. During times of unrest, Mount St. Helens and similar volcanoes elsewhere typically go through episodic changes in level of unrest over periods of days to weeks, or even months. Such changes are in part driven by variations in the rate of magma movement. We expect fluctuations in the level of unrest to continue during coming days. Escalation of unrest could occur suddenly and perhaps lead to an eruption with very little warning. There may be little time to raise the alert level before a hazardous event occurs. Therefore, we continue to monitor the situation closely and will issue additional updates and changes in alert level as warranted.
Wind forecasts from the National Oceanic and Atmospheric Administration (NOAA), combined with eruption models, show that winds this morning are southwesterly and any ash will drift to the northeast.
Press conferences will continue to be held at the Headquarters office of the Gifford Pinchot National Forest. The morning press conference is at 9:30 AM.
