William E Scott
In retirement I am working on completing a geologic map of Mount Hood volcano, Oregon.
Science and Products
Filter Total Items: 65
Timing of degassing and plagioclase growth in lavas erupted from Mount St. Helens, 2004-2005, from 210Po-210Pb-226Ra disequilibria
Disequilibrium between 210Po, 210Pb, and 226Ra was
measured on rocks and plagioclase mineral separates erupted
during the first year of the ongoing eruption of Mount St.
Helens. The purpose of this study was to monitor the volatile
fluxing and crystal growth that occurred in the weeks, years,
and decades leading up to eruption. Whole-rock samples were
leached in dilute HCl to remove 210Po pr
Authors
Mark K. Reagan, Kari M. Cooper, John S. Pallister, Carl R. Thornber, Matthew Wortel
Effects of lava-dome growth on the crater glacier of Mount St. Helens, Washington
The process of lava-dome emplacement through a glacier
was observed for the first time as the 2004-6 eruption of
Mount St. Helens proceeded. The glacier that had grown in the
crater since the cataclysmic 1980 eruption was split in two by
the new lava dome. The two parts of the glacier were successively squeezed against the crater wall. Photography, photogrammetry, and geodetic measurements doc
Authors
Joseph S. Walder, Steve P. Schilling, James W. Vallance, Richard G. LaHusen
Extrusion rate of the Mount St. Helens lava dome estimated from terrestrial imagery, November 2004-December 2005
Oblique, terrestrial imagery from a single, fixed-position
camera was used to estimate linear extrusion rates during
sustained exogenous growth of the Mount St. Helens lava
dome from November 2004 through December 2005. During
that 14-month period, extrusion rates declined logarithmically
from about 8-10 m/d to about 2 m/d. The overall ebbing of
effusive output was punctuated, however, by ep
Authors
Jon J. Major, Cole G. Kingsbury, Michael P. Poland, Richard G. LaHusen
Dynamics of seismogenic volcanic extrusion resisted by a solid surface plug, Mount St. Helens, 2004-2005
The 2004-5 eruption of Mount St. Helens exhibited
sustained, near-equilibrium behavior characterized by nearly
steady extrusion of a solid dacite plug and nearly periodic
occurrence of shallow earthquakes. Diverse data support the
hypothesis that these earthquakes resulted from stick-slip
motion along the margins of the plug as it was forced incrementally upward by ascending, solidifying, gas
Authors
Richard M. Iverson
Plagioclase populations and zoning in dacite of the 2004-2005 Mount St. Helens eruption: Constraints for magma origin and dynamics
We investigated plagioclase phenocrysts in dacite of the
2004-5 eruption of Mount St. Helens to gain insights into the
magmatic processes of the current eruption, which is characterized by prolonged, nearly solid-state extrusion, low gas
emission, and shallow seismicity. In addition, we investigated
plagioclase of 1980-86 dacite.
Light and Nomarski microscopy were used to texturally
character
Authors
Martin J. Streck, Cindy A. Broderick, Carl R. Thronber, Michael A. Clynne, John S. Pallister
Trace element and Pb isotope composition of plagioclase from dome samples from the 2004-2005 eruption of Mount St. Helens, Washington
We report the results of in-situ laser ablation ICP–MS
analyses of anorthite content, trace-element (Li, Ti, Sr, Ba, La,
Pr, Ce, Nd, Eu, Pb) concentrations, and Pb-isotope compositions
in plagioclase from eight dome-dacite samples collected from
the 2004-5 eruption of Mount St. Helens and, for comparison,
from three dome samples from 1981-85. For 2004-5 samples,
plagioclase phenocrysts range
Authors
Adam J. R. Kent, Michael C. Rowe, Carl R. Thornber, John S. Pallister
238U-230Th-226Ra Disequilibria in Dacite and Plagioclase from the 2004–2005 Eruption of Mount St. Helens
Uranium-series disequilibria in whole-rock samples and
mineral separates provide unique insights into the time scales
and processes of magma mixing, storage, and crystallization.
We present 238U-
230Th-226Ra data for whole-rock dacite and
gouge samples and for plagioclase separated from two dacite
samples, all erupted from Mount St. Helens between October
2004 and April 2005. We also present
Authors
Kari M. Cooper, Carrie T. Donnelly
Constraints on the size, overpressure, and volatile content of the Mount St. Helens magma system from geodetic and dome-growth measurements during the 2004-2006+ eruption
During the ongoing eruption at Mount St. Helens, Washington, lava has extruded continuously at a rate that decreased
from ~7-9 m3
/s in October 2004 to 1-2 m3
/s by December
2005. The volume loss in the magma reservoir estimated from
the geodetic data, 1.6-2.7×10
7
m3
, is only a few tens of percent
of the 7.5×10
7
m3
volume that had erupted by the end of 2005.
Authors
Larry G. Mastin, Evelyn Roeloffs, Nick M. Beeler, James E. Quick
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
Evolving magma storage conditions beneath Mount St. Helens inferred from chemical variations in melt inclusions from the 1980-1986 and current (2004-2006) eruptions
Major element, trace element, and volatile concentrations in 187 glassy melt inclusions and 25 groundmass glasses from the 1980-86 eruption of Mount St. Helens are presented, together with 103 analyses of touching FE-Ti oxide pairs from the same samples. These data are used to evaluate the temporal evolution of the magmatic plumbing system beneath the volcano during 1980-86 and so provide a frame
Authors
Jon Blundy, Katharine V. Cashman, Kim Berlo
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
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
Non-USGS Publications**
**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.
Science and Products
Filter Total Items: 65
Timing of degassing and plagioclase growth in lavas erupted from Mount St. Helens, 2004-2005, from 210Po-210Pb-226Ra disequilibria
Disequilibrium between 210Po, 210Pb, and 226Ra was
measured on rocks and plagioclase mineral separates erupted
during the first year of the ongoing eruption of Mount St.
Helens. The purpose of this study was to monitor the volatile
fluxing and crystal growth that occurred in the weeks, years,
and decades leading up to eruption. Whole-rock samples were
leached in dilute HCl to remove 210Po pr
Authors
Mark K. Reagan, Kari M. Cooper, John S. Pallister, Carl R. Thornber, Matthew Wortel
Effects of lava-dome growth on the crater glacier of Mount St. Helens, Washington
The process of lava-dome emplacement through a glacier
was observed for the first time as the 2004-6 eruption of
Mount St. Helens proceeded. The glacier that had grown in the
crater since the cataclysmic 1980 eruption was split in two by
the new lava dome. The two parts of the glacier were successively squeezed against the crater wall. Photography, photogrammetry, and geodetic measurements doc
Authors
Joseph S. Walder, Steve P. Schilling, James W. Vallance, Richard G. LaHusen
Extrusion rate of the Mount St. Helens lava dome estimated from terrestrial imagery, November 2004-December 2005
Oblique, terrestrial imagery from a single, fixed-position
camera was used to estimate linear extrusion rates during
sustained exogenous growth of the Mount St. Helens lava
dome from November 2004 through December 2005. During
that 14-month period, extrusion rates declined logarithmically
from about 8-10 m/d to about 2 m/d. The overall ebbing of
effusive output was punctuated, however, by ep
Authors
Jon J. Major, Cole G. Kingsbury, Michael P. Poland, Richard G. LaHusen
Dynamics of seismogenic volcanic extrusion resisted by a solid surface plug, Mount St. Helens, 2004-2005
The 2004-5 eruption of Mount St. Helens exhibited
sustained, near-equilibrium behavior characterized by nearly
steady extrusion of a solid dacite plug and nearly periodic
occurrence of shallow earthquakes. Diverse data support the
hypothesis that these earthquakes resulted from stick-slip
motion along the margins of the plug as it was forced incrementally upward by ascending, solidifying, gas
Authors
Richard M. Iverson
Plagioclase populations and zoning in dacite of the 2004-2005 Mount St. Helens eruption: Constraints for magma origin and dynamics
We investigated plagioclase phenocrysts in dacite of the
2004-5 eruption of Mount St. Helens to gain insights into the
magmatic processes of the current eruption, which is characterized by prolonged, nearly solid-state extrusion, low gas
emission, and shallow seismicity. In addition, we investigated
plagioclase of 1980-86 dacite.
Light and Nomarski microscopy were used to texturally
character
Authors
Martin J. Streck, Cindy A. Broderick, Carl R. Thronber, Michael A. Clynne, John S. Pallister
Trace element and Pb isotope composition of plagioclase from dome samples from the 2004-2005 eruption of Mount St. Helens, Washington
We report the results of in-situ laser ablation ICP–MS
analyses of anorthite content, trace-element (Li, Ti, Sr, Ba, La,
Pr, Ce, Nd, Eu, Pb) concentrations, and Pb-isotope compositions
in plagioclase from eight dome-dacite samples collected from
the 2004-5 eruption of Mount St. Helens and, for comparison,
from three dome samples from 1981-85. For 2004-5 samples,
plagioclase phenocrysts range
Authors
Adam J. R. Kent, Michael C. Rowe, Carl R. Thornber, John S. Pallister
238U-230Th-226Ra Disequilibria in Dacite and Plagioclase from the 2004–2005 Eruption of Mount St. Helens
Uranium-series disequilibria in whole-rock samples and
mineral separates provide unique insights into the time scales
and processes of magma mixing, storage, and crystallization.
We present 238U-
230Th-226Ra data for whole-rock dacite and
gouge samples and for plagioclase separated from two dacite
samples, all erupted from Mount St. Helens between October
2004 and April 2005. We also present
Authors
Kari M. Cooper, Carrie T. Donnelly
Constraints on the size, overpressure, and volatile content of the Mount St. Helens magma system from geodetic and dome-growth measurements during the 2004-2006+ eruption
During the ongoing eruption at Mount St. Helens, Washington, lava has extruded continuously at a rate that decreased
from ~7-9 m3
/s in October 2004 to 1-2 m3
/s by December
2005. The volume loss in the magma reservoir estimated from
the geodetic data, 1.6-2.7×10
7
m3
, is only a few tens of percent
of the 7.5×10
7
m3
volume that had erupted by the end of 2005.
Authors
Larry G. Mastin, Evelyn Roeloffs, Nick M. Beeler, James E. Quick
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
Evolving magma storage conditions beneath Mount St. Helens inferred from chemical variations in melt inclusions from the 1980-1986 and current (2004-2006) eruptions
Major element, trace element, and volatile concentrations in 187 glassy melt inclusions and 25 groundmass glasses from the 1980-86 eruption of Mount St. Helens are presented, together with 103 analyses of touching FE-Ti oxide pairs from the same samples. These data are used to evaluate the temporal evolution of the magmatic plumbing system beneath the volcano during 1980-86 and so provide a frame
Authors
Jon Blundy, Katharine V. Cashman, Kim Berlo
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
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
Non-USGS Publications**
**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.