Publications
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Investigation of magnesium isotope fractionation during basalt differentiation: Implications for a chondritic composition of the terrestrial mantle Investigation of magnesium isotope fractionation during basalt differentiation: Implications for a chondritic composition of the terrestrial mantle
To investigate whether magnesium isotopes are fractionated during basalt differentiation, we have performed high-precision Mg isotopic analyses by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) on a set of well-characterized samples from Kilauea Iki lava lake, Hawaii, USA. Samples from the Kilauea Iki lava lake, produced by closed-system crystal-melt...
Authors
F.-Z. Teng, M. Wadhwa, Rosalind T. Helz
Geology and complex collapse mechanisms of the 3.72 Ma Hannegan caldera, North Cascades, Washington, USA Geology and complex collapse mechanisms of the 3.72 Ma Hannegan caldera, North Cascades, Washington, USA
Contiguous ring faults of the 8 × 3.5 km Hannegan caldera enclose the Hannegan volcanics in the Cascade arc of northern Washington. The caldera collapsed in two phases, which each erupted rhyolitic ignimbrite (72.3%–75.2% SiO2). The first collapse phase, probably trap-door style, erupted the ≥900-m-thick ignimbrite of Hannegan Peak at 3.722 ± 0.020 Ma. This single cooling unit, generally...
Authors
David S. Tucker, Wes Hildreth, Tom Ullrich, Richard M. Friedman
Sediment compaction rates and subsidence in deltaic plains: Numerical constraints and stratigraphic influences Sediment compaction rates and subsidence in deltaic plains: Numerical constraints and stratigraphic influences
Natural sediment compaction in deltaic plains influences subsidence rates and the evolution of deltaic morphology. Determining compaction rates requires detailed knowledge of subsurface geotechnical properties and depositional history, neither of which is often readily available. To overcome this lack of knowledge, we numerically forward model the incremental sedimentation and compaction...
Authors
T.A. Meckel, Uri S. ten Brink, S.J. Williams
Interferogram formation in the presence of complex and large deformation Interferogram formation in the presence of complex and large deformation
Sierra Negra volcano in Isabela island, Galápagos, erupted from October 22 to October 30 in 2005. During the 8 days of eruption, the center of Sierra Negra's caldera subsided about 5.4 meters. Three hours prior to the onset of the eruption, an earthquake (Mw 5.4) occurred, near the caldera. Because of the large and complex phase gradient due to the huge subsidence and the earthquake, it...
Authors
S.-H. Yun, H. Zebker, P. Segall, A. Hooper, Michael P. Poland
Effects of wastewater disinfection on waterborne bacteria and viruses Effects of wastewater disinfection on waterborne bacteria and viruses
Wastewater disinfection is practiced with the goal of reducing risks of human exposure to pathogenic microorganisms. In most circumstances, the efficacy of a wastewater disinfection process is regulated and monitored based on measurements of the responses of indicator bacteria. However, inactivation of indicator bacteria does not guarantee an acceptable degree of inactivation among other
Authors
E. R. Blatchley, W.-L. Gong, J.E. Alleman, J.B. Rose, D.E. Huffman, M. Otaki, J.T. Lisle
Sorted bed forms as self-organized patterns: 2. complex forcing scenarios Sorted bed forms as self-organized patterns: 2. complex forcing scenarios
We employ a numerical model to study the development of sorted bed forms under a variety of hydrodynamic and sedimentary conditions. Results indicate that increased variability in wave height decreases the growth rate of the features and can potentially give rise to complicated, a priori unpredictable, behavior. This happens because the system responds to a change in wave characteristics...
Authors
Giovanni Coco, A. Brad Murray, Malcom O. Green, E. Robert Thieler, T.M. Hume
A circulation modeling approach for evaluating the conditions for shoreline instabilities A circulation modeling approach for evaluating the conditions for shoreline instabilities
Analytical models predict the growth (instability) of shoreline salients when deep-water waves approach the coast from highly oblique angles, contrary to classical shoreline change models in which shoreline salients can only dissipate. Using the process-based wave, circulation, and sediment transport model Delft3D, we test this prediction for simulated bathymetric and wave...
Authors
Jeffrey H. List, Andrew D. Ashton
Highstand fans in the California borderland: The overlooked deep-water depositional systems Highstand fans in the California borderland: The overlooked deep-water depositional systems
Contrary to widely used sequence-stratigraphic models, lowstand fans are only part of the turbidite depositional record; our analysis reveals that a comparable volume of coarse-grained sediment has been deposited in California borderland deep-water basins regardless of sea level. Sedimentation rates and periods of active sediment transport have been determined for deep-water canyon...
Authors
Jacob A. Covault, William R. Normark, Brian W. Romans, Stephan A. Graham
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
Hindcasting potential hurricane impacts on rapidly changing barrier islands Hindcasting potential hurricane impacts on rapidly changing barrier islands
Hindcasts of the coastal impact of Hurricane Ivan on Santa Rosa Island, Florida, using a storm-impact scaling model that compares hurricane-induced water levels to local dune morphology, were found to have an accuracy of 68% in predicting the occurrence of one of four impact regimes: swash, collision, overwash, and inundation. Errors were overwhelming under-predictions of the regime...
Authors
H.F. Stockdon, D.M. Thompson, A. H. Sallenger
Volcano-electromagnetic effects Volcano-electromagnetic effects
Volcano-electromagnetic effects—electromagnetic (EM) signals generated by volcanic activity—derive from a variety of physical processes. These include piezomagnetic effects, electrokinetic effects, fluid vaporization, thermal demagnetization/remagnetization, resistivity changes, thermochemical effects, magnetohydrodynamic effects, and blast-excited traveling ionospheric disturbances...
Authors
Malcolm J. S. Johnston
Guidelines on preparedness before, during, and after an ashfall Guidelines on preparedness before, during, and after an ashfall
This document has been prepared by the International Volcanic Health Hazard Network (IVHHN), Cities and Volcanoes Commission, GNS Science and the United States Geological Survey (USGS) to promote the safety of those who experience volcanic ashfall. It details procedures to follow if warning of a volcanic ashfall is given, recommends what to do during ashfall, and what methods are most...
Authors
C. Horwell