International Glaciospeleological Survey

U.S. Geological Survey, Vancouver, Washington University of Washington,  Pacific Northwest Seismograph Network, Seattle, Washington Mount St. Helens Update, October 6, 2004, 7:00 a.m, PDT Current status is Volcano Alert (Alert Level 3); aviation color code RED Seismicity overnight has remained at very low levels. After the vigourous  steam-and-ash emission of yesterday morning, seismicity dropped with individual  events becoming smaller. By about 5 p.m. PDT yesterday, individual events became rare and as of 11:00 p.m., seismicity has been stable at a low level. Yesterday, field crews continued to harden GPS sites for the approaching winter and retrieved data. The GPS sites on the dome survived the steam-and-ash emission and data are being received and processed at the observatory. The station on the northern flank of the dome, shows a trend of northward displacement totaling 2 cm in the last three days. This is the same sense of  movement recorded by the nearby station that was destroyed by the first steam-and-ash emission on 1 October. Data from the other two stations on the dome, which were installed on 4 October are currently being analyzed. Data from  GPS instruments on the outer flanks of the volcano show no movement of the outer flanks. No gas measurements were made yesterday. A seismic crew installed an additional broadband seismometer on the northwest flank of the volcano which  will help show a broader range of seismic energy release. With the help of the  U.S. Forest Service, field crews installed an antenna mast for a VSAT uplink  which will improve our ability to retrieve data from the field. It began raining on the mountain at about 7:30 p.m. PDT. By about 9:30 p.m.  about 0.1 inch of rain had fallen. Overnight, the acoustic flow monitoror (AFM)  in the crater indicated that several small debris flows had moved past the site. By midnight, higher flows were recorded at a station on the pumice plain, but none were large enough to trigger an automatic alert. We expect these types of  flowage events to recur during intense rainstorms. Wind forecasts from the National Oceanic and Atmospheric Administration  (NOAA), combined with eruption models, show winds this morning are from the  west-southwest such that any ash clouds will drift to the east-northeast. We continue to monitor the situation closely and will issue additional updates and Alert Level changes as warranted. 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. If  activity remains low, we will do a show-and-tell of some of the instruments were  are using to monitor the volcano at the press conference.

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U.S. Geological Survey, Vancouver, Washington University of Washington,  Pacific Northwest Seismograph Network, Seattle, Washington Mount St. Helens Alert Level Change Past Alert Level: Volcano Alert (Alert Level 3); aviation color code RED New Alert Level: Volcano Advisory (Alert Level 2); aviation color code ORANGE October 6, 2004 9:15 A.M., PDT Following yesterday morning’s steam-and-ash eruption, seismicity dropped to a  low level and has remained low. Low-level tremor observed following the eruption is also gradually declining. Lack of earthquake and rockfall signals suggest that deformation of the uplift area on the south side of the 1980-86 lava dome  has slowed. Brief visual observations this morning from Coldwater Visitor Center  showed weak steam emissions from the crater. We infer that the vigorous unrest of the past few days has lessened and that the probability of an imminent  eruption that would endanger life and property is significantly less than at any  time since Saturday, October 2, when the alert level was raised to Volcano Alert (Level 3). Therefore, we are lowering the alert level to Volcano Advisory (Alert  Level 2). Such decreases in the level of unrest, which may reflect a decrease in the rate of magma movement, have been common at Mount St. Helens during eruptions in 1980-86 and also at similar volcanoes elsewhere. Episodic changes in level of unrest over periods of days to weeks, or even months, are possible. We don’t  think that the current episode of unrest is over and we expect fluctuations in the level of unrest to continue during coming days and months. Everyone should  be aware that escalation in unrest and perhaps an eruption could occur suddenly or 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. Mount St. Helens Update, October 6, 2004, 7:00 a.m,  PDT Current status is Volcano Alert (Alert Level 3); aviation color code RED Seismicity overnight has remained at very low levels. After the vigourous  steam-and-ash emission of yesterday morning, seismicity dropped with individual  events becoming smaller. By about 5 p.m. PDT yesterday, individual events became rare and as of 11:00 p.m., seismicity has been stable at a low level. Yesterday, field crews continued to harden GPS sites for the approaching winter and retrieved data. The GPS sites on the dome survived the steam-and-ash emission and data are being received and processed at the observatory. The station on the northern flank of the dome, shows a trend of northward displacement totaling 2 cm in the last three days. This is the same sense of  movement recorded by the nearby station that was destroyed by the first steam-and-ash emission on 1 October. Data from the other two stations on the dome, which were installed on 4 October are currently being analyzed. Data from  GPS instruments on the outer flanks of the volcano show no movement of the outer flanks. No gas measurements were made yesterday. A seismic crew installed an additional broadband seismometer on the northwest flank of the volcano which  will help show a broader range of seismic energy release. With the help of the  U.S. Forest Service, field crews installed an antenna mast for a VSAT uplink  which will improve our ability to retrieve data from the field. It began raining t the mountain at about 7:30 p.m. PDT. By about 9:30 p.m. about 0.1 inch of rain had fallen. Overnight, the acoustic flow monitoror (AFM) in the crater indicated that several small debris flows had moved past the site.  By midnight, higher flows were recorded at a station on the pumice plain, but none were large enough to trigger an automatic alert. We expect these types of  flowage events to recur during intense rainstorms. Wind forecasts from the National Oceanic and Atmospheric Administration  (NOAA), combined with eruption models, show winds this morning are from the  west-southwest such that any ash clouds will drift to the east-northeast. We continue to monitor the situation closely and will issue additional updates and Alert Level changes as warranted. 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. If  activity remains low, we will do a show-and-tell of some of the instruments were  are using to monitor the volcano at the press conference.

U.S. Geological Survey, Vancouver, Washington University of Washington,  Pacific Northwest Seismograph Network, Seattle, Washington Mount St. Helens Update, October 6, 2004, 6:00 p.m, PDT Current status is Volcano Advisory (Alert Level 2); aviation color code  ORANGE The low rate of seismic activity that followed yesterday’s steam and ash emission continued through last night, but rose slowly between about 9 a.m. and 1 p.m., before leveling off at a slightly higher level. Earthquakes are presently occurring at a rate of about one per minute with a maximum magnitude  of about 1.0. No thermal observations were possible today owing to low clouds and rain, but late this 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 last nights rain storm. Lahars flowed a short distance toward both Spirit Lake and the North Fork Toutle River. Another crew worked on installation of  broad-band seismometers on the lower flanks of the volcano. Information received today indicates that a light dusting of ash from  yesterday’s event affected the eastern part of Mount Rainier National Park,  about 70 miles north-northeast of Mount St. Helens. As a result of the intense unrest of the past 10 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 in the degree of unrest and perhaps an eruption could occur suddenly or 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 winds this evening will remain westerly and any ash clouds will drift eastward to northeastward. 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

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