Publications

The 2004-6 eruption of Mount St. Helens produced dacite that contains 40-50 volume percent phenocrysts of plagioclase, amphibole, low-Ca pyroxene, magnetite, and ilmenite in a groundmass that is nearly totally crystallized. Phenocrysts of amphibole and pyroxene range from 3 to 5 mm long and are cyclically zoned, with one to three alternations of Fe- and Al-rich to Mg- and Si-rich layers showi

Beginning in October 2004, a new lava dome grew on the glacier-covered crater floor of Mount St. Helens, Washington, immediately south of the 1980s lava dome. Seventeen digital elevation models (DEMs) constructed from vertical aerial photographs have provided quantitative estimates of extruded lava volumes and total volume change. To extract volumetric changes and calculate volumetric extrus

The instruments in place at the start of volcanic unrest at Mount St. Helens in 2004 were inadequate to record the large earthquakes and monitor the explosions that occurred as the eruption developed. To remedy this, new instruments were deployed and the short-period seismic network was modified. A new method of establishing near-field seismic monitoring was developed, using remote deploymen

Six explosions occurred during 2004-5 in association with renewed eruptive activity at Mount St. Helens, Washington. Of four explosions in October 2004, none had precursory seismicity and two had explosion-related seismic tremor that marked the end of the explosion. However, seismicity levels dropped following each of the October explosions, providing the primary instrumental means for explos

Eighteen years after dome-forming eruptions ended in 1986, and with little warning, Mount St. Helens began to erupt again in October 2004. During the ensuing two years, the volcano extruded more than 80×106 m3 of gas-poor, crystal-rich dacite lava. The 2004-6 dacite is remarkably uniform in bulk-rock composition and, at 65 percent SiO2 , among the richest in silica and most depleted in inc

Petrologic studies of volcanic ash are commonly used to identify juvenile volcanic material and observe changes in the composition and style of volcanic eruptions. During the 2004-5 eruption of Mount St. Helens, recognition of the juvenile component in ash produced by early phreatic explosions was complicated by the presence of a substantial proportion of 1980-86 lava-dome fragments and glass

Self-contained, single-frequency GPS instruments fitted on lightweight stations suitable for helicopter-sling payloads became a critical part of volcano monitoring during the September 2004 unrest and subsequent eruption of Mount St. Helens. Known as “spiders” because of their spindly frames, the stations were slung into the crater 29 times from September 2004 to December 2005 when conditions

Detecting far-field deformation at Mount St. Helens since the crater-forming landslide and blast in 1980 has been difficult despite frequent volcanic activity and improved monitoring techniques. Between 1982 and 1991, the systematic extension of line lengths in a regional GPS trilateration network is consistent with recharge of a deep magma chamber during that interval. The rate of extension,

We report the results of recent geologic mapping and radiometric dating that add considerable detail to our understanding of the eruptive history of Mount St. Helens before its latest, or Spirit Lake, stage. New data and reevaluation of earlier work indicate at least two eruptive periods during the earliest, or Ape Canyon, stage, possibly separated by a long hiatus: one about 300-250 ka and a seco

This highly specialized book is interesting not only because of its important subject matter but also because of its egocentric perspective. The majority of the book provides a nearly exhaustive retrospective of the authors’ many contributions to the shallow‐flow theory of granular avalanches, and it also critiques contributions by others. Indeed, some readers (including this reviewer) might be di

No abstract available.

From October 2004 to May 2005, the Center for Earthquake Research and Information of the University of Memphis operated two to six broadband seismometers within 5 to 20 km of Mount St. Helens to help monitor recent seismic and volcanic activity. Approximately 57,000 earthquakes identified during the 7-month deployment had a normal magnitude distribution with a mean magnitude of 1.78 and a stan