Publications
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40Ar/39Ar ages of the AD 79 eruption of Vesuvius, Italy 40Ar/39Ar ages of the AD 79 eruption of Vesuvius, Italy
The Italian volcano, Vesuvius, erupted explosively in AD 79. Sanidine from pumice collected at Casti Amanti in Pompeii and Villa Poppea in Oplontis yielded a weighted-mean 40Ar/39Ar age of 1925±66 years in 2004 (1σ uncertainty) from incremental-heating experiments of eight aliquants of sanidine. This is the calendar age of the eruption. Our results together with the work of Renne et al....
Authors
Marvin A. Lanphere, Duane E. Champion, Leone Melluso, Vincenzo Morra, Annamaria Perrotta, Claudio Scarpati, Dario Tedesco, Andrew T. Calvert
Mount St. Helens Petrology Workshop Mount St. Helens Petrology Workshop
Following seismic activity in late September 2004, the current eruption of Mount St. Helens began with an explosive steam and ash emission on 1 October 2004, with hot dacite emerging from the crater floor on 11 October 2004. Nearly two years later, with more than 80 million cubic meters of erupted dacite, accompanied by rare explosions and predominantly shallow seismicity questions still...
Authors
Michael C. Rowe, John S. Pallister, Anita L. Grunder
Landslide susceptibility revealed by LIDAR imagery and historical records, Seattle, Washington Landslide susceptibility revealed by LIDAR imagery and historical records, Seattle, Washington
Light detection and ranging (LIDAR) data were used to visually map landslides, headscarps, and denuded slopes in Seattle, Washington. Four times more landslides were mapped than by previous efforts that used aerial photographs. The mapped landforms (landslides, headscarps, and denuded slopes) were created by many individual landslides. The spatial distribution of mapped landforms and...
Authors
W.H. Schulz
Drag-out effect of piezomagnetic signals due to a borehole: The Mogi source as an example Drag-out effect of piezomagnetic signals due to a borehole: The Mogi source as an example
We show that using borehole measurements in tectonomagnetic experiments allows enhancement of the observed signals. New magnetic dipoles, which vary with stress changes from mechanical sources, are produced on the walls of the borehole. We evaluate such an effect quantitatively. First we formulate a general expression for the borehole effect due to any arbitrary source models. This is...
Authors
Y. Sasai, M.J.S. Johnston, Y. Tanaka, R. Mueller, T. Hashimoto, M. Utsugi, S. Sakanaka, M. Uyeshima, J. Zlotnicki, P. Yvetot
The lakes of Titan The lakes of Titan
The surface of Saturn’s haze-shrouded moon Titan has long been proposed to have oceans or lakes, on the basis of the stability of liquid methane at the surface1,2. Initial visible3 and radar4,5 imaging failed to find any evidence of an ocean, although abundant evidence was found that flowing liquids have existed on the surface5,6. Here we provide definitive evidence for the presence of...
Authors
Ellen R. Stofan, Charles Elachi, Jonathan I. Lunine, Ralf D. Lorenz, B. Stiles, K. L. Mitchell, S. Ostro, Laurence A. Soderblom, C. Wood, H. Zebker, S. Wall, Michael A. Janssen, Randolph L. Kirk, Rosaly Lopes, F. Paganelli, Jani Radebaugh, L. Wye, Y. Anderson, M. Allison, R. Boehmer, P. Callahan, P. Encrenaz, E. Flamini, G. Francescetti, Y. Gim, G. Hamilton, S. Hensley, W.T.K. Johnson, K. Kelleher, D. Muhleman, Philipe Paillou, G. Picardi, F. Posa, L. Roth, R. Seu, S. Shaffer, S. Vetrella, R. West
Hydrothermal circulation at Mount St. Helens determined by self-potential measurements Hydrothermal circulation at Mount St. Helens determined by self-potential measurements
The distribution of hydrothermal circulation within active volcanoes is of importance in identifying regions of hydrothermal alteration which may in turn control explosivity, slope stability and sector collapse. Self-potential measurements, indicative of fluid circulation, were made within the crater of Mount St. Helens in 2000 and 2001. A strong dipolar anomaly in the self-potential...
Authors
Paul A. Bedrosian, Martyn J. Unsworth, Malcolm J. S. Johnston
Colored dissolved organic matter in Tampa Bay, Florida Colored dissolved organic matter in Tampa Bay, Florida
Absorption and fluorescence of colored dissolved organic matter (CDOM) and concentrations of dissolved organic carbon (DOC), chlorophyll and total suspended solids in Tampa Bay and its adjacent rivers were examined in June and October of 2004. Except in Old Tampa Bay (OTB), the spatial distribution of CDOM showed a conservative relationship with salinity in June, 2004 (aCDOM(400) = − 0...
Authors
Z. Chen, C. Hu, R.N. Conmy, F. Muller-Karger, P. Swarzenski
Annual modulation of seismicity along the San Andreas Fault near Parkfield, CA Annual modulation of seismicity along the San Andreas Fault near Parkfield, CA
We analyze seismic data from the San Andreas Fault (SAF) near Parkfield, California, to test for annual modulation in seismicity rates. We use statistical analyses to show that seismicity is modulated with an annual period in the creeping section of the fault and a semiannual period in the locked section of the fault. Although the exact mechanism for seasonal triggering is undetermined...
Authors
L.B. Christiansen, Shaul Hurwitz, Steven E. Ingebritsen
Vapor transfer prior to the October 2004 eruption of Mount St. Helens, Washington Vapor transfer prior to the October 2004 eruption of Mount St. Helens, Washington
Dome lavas from the 2004 eruption of Mount St. Helens show elevated Li contents in plagioclase phenocrysts at the onset of dome growth in October 2004. These cannot be explained by variations in plagioclase-melt partitioning, but require elevated Li contents in coexisting melt, a fact confirmed by measurements of Li contents as high as 207 µg/g in coexisting melt inclusions. Similar Li...
Authors
A.J.R. Kent, J. Blundy, K. V. Cashman, K.M. Copper, C. Donnelly, John S. Pallister, M. Reagan, M.C. Rowe, Carl Thornber
Diurnal variation of oxygen and carbonate system parameters in Tampa Bay and Florida Bay Diurnal variation of oxygen and carbonate system parameters in Tampa Bay and Florida Bay
Oxygen and carbonate system parameters were measured, in situ, over diurnal cycles in Tampa Bay and Florida Bay, Florida. All system parameters showed distinct diurnal trends in Tampa Bay with an average range of diurnal variation of 39.1 μmol kg− 1 for total alkalinity, 165.1 μmol kg− 1 for total CO2, 0.22 for pH, 0.093 mmol L− 1 for dissolved oxygen, and 218.1 μatm for pCO2. Average...
Authors
K. K. Yates, C. Dufore, N. Smiley, C. Jackson, R. B. Halley
Methane gas hydrate effect on sediment acoustic and strength properties Methane gas hydrate effect on sediment acoustic and strength properties
To improve our understanding of the interaction of methane gas hydrate with host sediment, we studied: (1) the effects of gas hydrate and ice on acoustic velocity in different sediment types, (2) effect of different hydrate formation mechanisms on measured acoustic properties (3) dependence of shear strength on pore space contents, and (4) pore pressure effects during undrained shear. A...
Authors
W.J. Winters, W.F. Waite, D.H. Mason, L.Y. Gilbert, I.A. Pecher
Understanding Merapi-type volcanoes Understanding Merapi-type volcanoes
"We have to understand volcano science to know what to monitor.” That simple statement by Antonius Ratdomopurbo, director of the Indonesian Center for Volcano Technology [Balai Penyelidikan dan Pengembangan‐Teknologi (BPPTK)],captured the spirit and content of a recent workshop about Merapi and Merapi‐type volcanoes. Merapi still is experiencing low levels of unrest, following a peak in...
Authors
M.A. Purbawinata, Antonius Ratdomopurbo, John S. Pallister, B. Luehr, Chris Newhall