Publications
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Radar interferometry observations of surface displacements during pre- and coeruptive periods at Mount St. Helens, Washington, 1992-2005
We analyzed hundreds of interferograms of Mount St.
Helens produced from radar images acquired by the ERS-1/2,
ENVISAT, and RADARSAT satellites during the 1992-2004
preeruptive and 2004-2005 coeruptive periods for signs of
deformation associated with magmatic activity at depth. Individual interferograms were often contaminated by atmospheric
delay anomalies; therefore, we employed stacking to
Authors
Michael P. Poland, Zhong Lu
Use of thermal infrared imaging for monitoring renewed dome growth at Mount St. Helens, 2004
A helicopter-mounted thermal imaging radiometer documented the explosive vent-clearing and effusive phases of the
eruption of Mount St. Helens in 2004. A gyrostabilized gimbal controlled by a crew member housed the radiometer and
an optical video camera attached to the nose of the helicopter. Since October 1, 2004, the system has provided thermal
and video observations of dome growth. Flights c
Authors
David J. Schneider, James W. Vallance, Rick L. Wessels, Matthew Logan, Michael S. Ramsey
Growth of the 2004-2006 lava-dome complex at Mount St. Helens, Washington
The eruption of Mount St. Helens from 2004 to 2006
has comprised extrusion of solid lava spines whose growth
patterns were shaped by a large space south of the 1980-86
dome that was occupied by the unique combination of glacial
ice, concealed subglacial slopes, the crater walls, and relics
of previous spines. The eruption beginning September 2004
can be divided (as of April 2006) into five p
Authors
James W. Vallance, David J. Schneider, Steve P. Schilling
Magmatic conditions and processes in the storage zone of the 2004-2006 Mount St. Helens dacite
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
Authors
Malcom J. Rutherford, Joseph D. Devine
Use of digital aerophotogrammetry to determine rates of lava dome growth, Mount St. Helens, Washington, 2004-2005
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
Authors
Steve P. Schilling, Ren A. Thompson, James A. Messerich, Eugene Y. Iwatsubo
Seismic-monitoring changes and the remote deployment of seismic stations (seismic spider) at Mount St. Helens, 2004-2005
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
Authors
Patrick J. McChesney, Marvin R. Couchman, Seth C. Moran, Andrew B. Lockhart, Kelly J. Swinford, Richard G. LaHusen
Seismicity and infrasound associated with explosions at Mount St. Helens, 2004-2005
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
Authors
Seth C. Moran, Patrick J. McChesney, Andrew B. Lockhart
Petrology of the 2004-2006 Mount St. Helens lava dome -- implications for magmatic plumbing and eruption triggering
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
Authors
John S. Pallister, Carl R. Thornber, Katharine V. Cashman, Michael A. Clynne, Heather Lowers, Charlie Mandeville, Isabelle K. Brownfield, Gregory P. Meeker
Identification and evolution of the juvenile component in 2004-2005 Mount St. Helens ash
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
Authors
Michael C. Rowe, Carl R. Thornber, Adam J. R. Kent
Instrumentation in remote and dangerous settings; examples using data from GPS “spider” deployments during the 2004-2005 eruption of Mount St. Helens, Washington
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
Authors
Richard G. LaHusen, Kelly J. Swinford, Matthew Logan, Michael Lisowski
Analysis of GPS-measured deformation associated with the 2004-2006 dome-building eruption of Mount St. Helens, Washington
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,
Authors
Michael Lisowski, Daniel Dzurisin, Roger P. Denlinger, Eugene Y. Iwatsubo
The Pleistocene eruptive history of Mount St. Helens, Washington, from 300,000 to 12,800 years before present
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
Authors
Michael A. Clynne, Andrew T. Calvert, Edward W. Wolfe, Russell C. Evarts, Robert J. Fleck, Marvin A. Lanphere