Publications
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Frictional properties of the Mount St. Helens gouge
Frictional properties of gouge bounding the solid dacite
plug that extruded at Mount St. Helens during 2004 and 2005
may have caused stick-slip upward motion of the plug and
associated seismicity. Laboratory experiments were performed
with a ring-shear device to test the dependence of the peak
and steady-state frictional strength of the gouge on shearing rate and hold time. A remolded gouge s
Authors
Peter L. Moore, Neal R. Iverson, Richard M. Iverson
Chemistry, mineralogy, and petrology of amphibole in Mount St. Helens 2004-2006 dacite
Textural, compositional, and mineralogical data are
reported and interpreted for a large population of clinoamphibole phenocrysts in 22 samples from the seven successive
dacite spines erupted at Mount St. Helens between October
2004 and January 2006. Despite the uniformity in bulk composition of magma erupted since 2004, there is striking textural
and compositional diversity among amphibole ph
Authors
Carl R. Thornber, John S. Pallister, Heather Lowers, Michael C. Rowe, Charlie Mandeville, Gregory P. Meeker
From dome to dust: shallow crystallization and fragmentation of conduit magma during the 2004-2006 dome extrusion of Mount St. Helens, Washington
An unusual feature of the 2004-6 eruptive activity of
Mount St. Helens has been the continuous growth of successive spines that are mantled by thick fault gouge. Fault gouge
formation requires, first, solidification of ascending magma
within the conduit, then brittle fragmentation and cataclastic
flow. We document these processes through field relations,
hand samples, and thin-section texture
Authors
Katharine V. Cashman, Carl R. Thornber, John S. Pallister
Remote camera observations of lava dome growth at Mount St. Helens, Washington, October 2004 to February 2006
Images from a Web-based camera (Webcam) located 8
km north of Mount St. Helens and a network of remote, telemetered digital cameras were used to observe eruptive activity
at the volcano between October 2004 and February 2006. The
cameras offered the advantages of low cost, low power, flexibility in deployment, and high spatial and temporal resolution. Images obtained from the cameras provided i
Authors
Michael P. Poland, Daniel Dzurisin, Richard G. LaHusen, Jon J. Major, Dennis Lapcewich, Elliot T. Endo, Daniel J. Gooding, Steve P. Schilling, Christine G. Janda
Photogeologic maps of the 2004-2005 Mount St. Helens eruption
The 2004-5 eruption of Mount St. Helens, still ongoing
as of this writing (September 2006), has comprised chiefly
lava dome extrusion that produced a series of solid, faultgouge-mantled dacite spines. Vertical aerial photographs
taken every 2 to 4 weeks, visual observations, and oblique
photographs taken from aircraft and nearby observation
points provide the basis for two types of photogeolo
Authors
Trystan M. Herriott, David R. Sherrod, John S. Pallister, James W. Vallance
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