Mount St. Helens Precursory Activity

USGS scientists monitor the growth of the bulge from Timberline Viewpoint, May 4, 1980. USGS photo courtesy of Dan Miller.

Hurry Up and Wait - USGS scientists continued to monitor the growth of the bulge. For over a week parts of the north flank have pushed outward at an average rate of 5 feet per day. Earthquake activity remained about the same level as in previous weeks. In the absence of phreatic explosions, scientists found it increasingly difficult to convince non-scientists that a volcanic hazard existed. The quiet ended on May 7 when steam and ash explosions resumed. Earthquake activity also increased later in the week. Scientists were convinced the continued growth of the bulge was a hazard, but could not predict the timing of either landslides or an eruption.

Daily Log

May 3 - The mountain continued to steam without explosions and the bulge continued to grow. Only 26 earthquakes larger than 3.0 were recorded, including 5 larger than 3.9. The USGS took time from monitoring efforts to discuss funding for the increasingly expensive volcano watch.

May 4 - The volcano remained quiet. The bulge continued to move outwards by as much as 5 feet per day in places. USGS geologists were convinced that some bulging resulted from intrusion of magma in late March, but were uncertain if the current bulging is due to intrusion or settling of the already displaced part of the mountain. COSPEC measurements made from Timberline did not detect significant amounts of sulfur dioxide.

Wisps of steam escapes from the crater, May 4, 1980. USGS photo courtesy of Rick Hoblitt.

May 5 - Strong emissions of ash have been uncommon for the past three weeks. The Goat Rocks EDM target had moved outwards to the north between 40 and 50 feet over the previous 11 days. During an interview with the Tacoma News Tribune Jack Hyde, a Tacoma Community College geologist, speculated that the instability of the bulge might result in a massive landslide. The landslide could be followed by a spectacular explosion of lava, possibly without warning, as vents on the northern slope are opened up. USGS geologist Bob Tilling was quoted in The Oregonian: "(The deformation) is continuing at a very high rate. Sometime it has to go. We just don't know how much longer this can last." In the meantime, smoke from slash burns prompted rumors of lava flows.

One of the reasons some people do not understand why scientists and officials have remained cautious may be their familiarity with famous Hawaiian volcanoes. Their frequent eruptions and familiar lava flows have contributed to the popular belief that all volcanoes have fluid, channelized lava flows. One logger was quoted: "We're logging 10 miles away from the peak...I don't see any hazard. I just came back from Hawaii, where they run tourist buses right up to the edge of a venting volcano."

Goat Rocks dome had pushed outward to the north between 40 and 50 feet in 11 days. Note tracks from earlier earthquake-triggered avalanches. USGS photo courtes of Dan Miller.

As the bulge continued to grow, more cracks formed on its surface. USGS photo coutesy of Dan Miller.

May 6 - Clouds obscured the mountain. There were no documented explosions. Earthquake activity continued at about the same level as during previous weeks. The bulge continued to push outwards at 4 to 5 feet per day. For the past two weeks the mountain has done nothing to convince a non-scientist that a volcanic hazard exists. In a Vancouver Columbian article the Sierra Club was quoted as suggesting that Mount St. Helens be considered for national monument status.

Emergency operations center at the USFS headquarters in Vancouver. USFS photo courtesy of Jim Hughes.

May 7 - Explosions resumed after a two week break. Steam and ash plumes reached 13,000 feet. The bulge continued to push outwards. Earthquake activity remained about the same. Since March 20 2550 earthquakes larger than magnitude 3.0 have been recorded, including 291 larger than 4.0. According to a USFS spokesman,"we've had more quakes above 4.0 here in the past few weeks than California has had in the past ten years." Due to renewed activity, USGS geologist Don Mullineaux cancelled a town meeting in Toutle. The meeting was planned to address concerns of local residents about the ongoing crisis.

Small explosions of steam and ash resumed on May 7. USGS photo courtesy of Dan Miller.

May 8 - Muddy rain fell on Timberline as ash was carried to the north and east of the mountain. Steam was observed in the crater and near the head of Shoestring Glacier. At noon airborne observers noted many new avalanches up to 100 feet wide and 1000 feet long on the Wishbone Glacier. There were 25 earthquakes larger than magnitude 3.0 recorded, including 11 larger than 4.0. This was the highest number of large earthquakes since April 24. Harmonic tremor was also recorded, the first since April 12.

Mount St. Helens from the west in early May. Dashed line indicates pre-1980 profile. USGS photo.

May 9 - Explosions continued. Continuous steaming in the crater and at the head of Shoestring Glacier was observed. There were 21 earthquakes larger than magnitude 3.0 recorded, including 9 larger than 4.0. The largest reached magnitude 4.9. The USGS ceased measurements at the Timberline Viewpoint due to the increased danger from sudden avalanches. USGS seismologist Craig Weaver said the new seismic station at Dogs Head may give notice of a massive landslide and will allow scientists to monitor steam and ash emissions 24 hours a day, regardless of weather. USGS geologist Don Mullineaux told at least 130 Toutle residents that the risks from Mount St. Helens were something they could live with. He pointed out that the school where the crowd had gathered was one of the safest places in the area at 135 feet above the valley floor.

USGS scientists make EDM measurements of Goat Rocks dome (GRD) from Coldwater II observation post, May 9, 1980. USGS photo.