Volcanic eruptions of 1980 at Mount St. Helens: The first 100 days

Abstract

Volcanologist David A. Johnston writing field notes at Coldwater II observation station May 17, 1980, the evening before he was killed by the lateral blast of the Mount St. Helens eruption. Earlier in the day, Johnston had collected volcanic gas samples from a fumarole high on the unstable northern side of the volcano (see fig. 20.). This photograph was taken by Harry Glicken, who was relieved of his observer duties at Coldwater II by Johnston and who brought this film out of the area the night before the fatal eruption. Among those who lost their lives in the May 18, 1980, eruption of Mount St. Helens was an exceptional colleague, volcanologist David Johnston. David was special not only because he was the first member of the U.S. Geological Survey to die in a volcanic eruption but also because of his capabilities and his dedication to his science. He knew well the personal risks involved in studying active volcanoes. Yet, his belief in the need to better understand volcano behavior led him to vigorous service in the "front lines" at Mount St. Helens. Through it all, he displayed a rare combination of inventiveness and originality in his scientific observations and interpretations. On the morning of May 18, David was alone at the Coldwater II observation station, 5.7 miles from the mountain's summit, measuring the volcano's bulging northern side. He was among the first to see the beginning of the eruption and tried to send a warning to the control center. "Vancouver, Vancouver, this is it!," he shouted into his radio. Then, as the black, billowing front of the lateral blast raced toward him, he tried a second message, which was garbled by atmospheric disturbance from the eruption. Then-nothing. The lateral blast obliterated Coldwater II observation station. Ironically, the location was (and is again) considered to be much safer than some of the sites on the mountain itself that David and his colleagues visited regularly. We dedicate this report to David Johnston, an untimely loss to his science as well as to his friends. Photographs used to depict various events or features discussed in the text were selected, insofar as it was practical, to reflect the first occurrence or discussion of the specific event or feature. Better illustrations of several subjects, however, are provided by photographs that were not strictly equivalent in time. Other illustrations are enhanced by paintings by U.S.

Directed blasts and blast-generated pyroclastic density currents: a comparison of the Bezymianny 1956, Mount St Helens 1980, and Soufrière Hills, Montserrat 1997 eruptions and deposits

“…Pyroclasts with diameters of 1 cm or less are easily supported by turbulence, and particles approaching 10 cm diameter can be supported by free-stream velocities ≫200 m s −1 . Current-front velocities calculated by us from the Christiansen-Larsen photographs from Mount Adams (Foxworthy and Hill 1982;Moore and Rice 1984) suggest maximum speeds around 130 m s −1 , and Moore and Rice (1984) mentioned a maximum speed of 150 m s −1 . Noting that the head of a turbulent gravity current travels at ∼60-70% of the speed of the following current (Simpson 1987), internal speeds could have been about 180-210 m s −1 .…”

“…On MSH, a rapid uninterrupted transition was directly observed and photographed, from a complex slope failure to explosions that began even as the slope failure evolved, leading to subsequent joint travel of the resulting flows (debris avalanche, explosion, and blast PDC) (Voight 1981;Foxworthy and Hill 1982). Slope failures at MSH and probably also at BZ occurred retrogressively in several slices, with outer slices failing first because of highest shear stress (Voight and Elsworth 1997).…”

Rockslide-debris avalanche of May 18, 1980, Mount St. Helens Volcano, Washington

“…Combining this work with studies of the geology of the old mountain (C.A. Hopson, written communication, 1980) and studies of eyewitness photographs of the first moments of the eruption (Voight, 1981;Foxworthy and Hill, 1982;Moore and Rice, 1984) this report tells much of the story of how the volcano fell and blasted apart. It builds upon preliminary work by Voight andothers (1981, 1983).…”

Limnology of two new lakes, Mount St. Helens, WA

“…Within minutes of the onset of the eruption, the heat of the pyroclastic debris began to melt snow and ice on the upper regions of the volcano, producing destructive lahars which swiftly travelled down Smith and Pine Creeks and the Muddy River on the eastern flank of the mountain, entering the eastern end of Swift Reservoir before an hour had elapsed (Foxworthy and Hill 1982). Mudflows developed on the western slope of the mountain during the initial hours after the eruption, coursing down the South Fork of the Toutle River.…”