Publications
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Biogenic silica in Lake Baikal sediments: results from 1990-1992 American cores
The Lake Baikal Paleoclimate Project is a joint Russian-American program established to study the paleoclimate of Central Asia. During three summer field seasons, duplicate Russian and American cores were taken at a number of sites in different sedimentary environments in the lake. Eight cores returned to the U.S. were quantitatively analyzed for biogenic silica using a single-step 5-hour alkaline
Authors
Susan J. Carter, Steven M. Colman
210Pb balance and implications for particle transport on the continental shelf, U.S. Middle Atlantic Bight
Supply of 210Pb to the continental shelf off the northeastern United States is dominated by the deposition from the atmosphere, the rate of which is reliably known from previously published work. Excess 210Pb inventories in the shelf sediments show accumulations that are nearly in balance with the supply, even in areas of relict sands where it is believed that no net accumulation of sediment prese
Authors
M.P. Bacon, Rebecca A. Belastock, Michael H. Bothner
Explosive tephra emissions of Mount St. Helens, 1989-1991: the violent escape of magmatic gas following storms?
From 24 August 1989 until 18 June 1991, Mount St. Helens produced at least 28 shallow, explosion-like seismic events with signatures similar to those produced by gas explosions on the dome during the mid 1980s. At least six were accompanied by violent emission of non-juvenile tephra, ejection of blocks of rock nearly 1 km from the vent, and avalanching of debris off the north side of the dome. All
Authors
L.G. Mastin
Emplacement and inflation of pahoehoe sheet flows: observations and measurements of active lava flows on Kilauea volcano, Hawaii
Inflated pahoehoe sheet flows have a distinctive horizontal upper surface, which can be several hundred meters across, and are bounded to steep monoclinal uplifts. The inflated sheet flows studied ranged from 1 to 5 m in thickness, but initially propagated as thin sheets of fluid pahoehoe lava, generally 20-30 cm thick. The morphology of the lava as flow advanced is described. Inflated sheet flows
Authors
K. Hon, J. Kauahikaua, R. Denlinger, K. Mackay
Origin of phenocrysts and compositional diversity in pre-Mazama rhyodacite lavas, Crater Lake, Oregon
Phenocrysts in porphyritic volcanic rocks may originate in a variety of ways in addition to nucleation and growth in the matrix in which they are found. Porphyritic rhyodacite lavas that underlie the eastern half of Mount Mazama, the High Cascade andesite/dacite volcano that contains Crater Lake caldera, contain evidence that bears on the general problem of phenocryst origin. Phenocrysts in these
Authors
S. Nakada, C. R. Bacon, A.E. Gartner
Late Quaternary normal faulting of the Hat Creek basalt, northern California
The Hat Creek fault is a major, young, north-striking, normal fault along the western boundary of extensional Basin and Range deformation in the Lessen region of northeastern California. Volcanic rocks of Quaternary and late Pliocene age are displaced a total of >500 m down to the west along west-facing, en echelon scarps now retreated to ∼35° slopes. Fresh, young scarps as much as 30 m high cut t
Authors
L.I.P. Muffler, M.A. Clynne, D. E. Champion
Fractionation of families of major, minor, and trace metals across the melt-vapor interface in volcanic exhalations
Chemical families of metals fractionate systematically as they pass from a silicate melt across the interface with the vapor phase and on into a cooled volcanic plume. We measured three groups of metals in a small suite of samples collected on filters from the plumes of Kilauea (Hawaii, USA), Etna (Sicily), and Merapi (Java) volcanoes. These were the major, minor, and trace metals of the alkali an
Authors
T. K. Hinkley, M.-F. Le Cloarec, G. Lambert
Hornblende-melt trace-element partitioning measured by ion microprobe
Trace-element abundances were measured in situ by ion microprobe in five samples of hornblende and melt ranging from basaltic andesite to high-silica rhyolite. Except for one sample, for which quench overgrowth or disequilibrium is suspected, the abundance ratios show systematic inter-element and inter-sample variations, and probably approach true partition coefficients. Apparent partition coeffic
Authors
T. W. Sisson
The role of magmas in the formation of hydrothermal ore deposits
Magmatic fluids, both vapour and hypersaline liquid, are a primary source of many components in hydrothermal ore deposits formed in volcanic arcs. These components, including metals and their ligands, become concentrated in magmas in various ways from various sources, including subducted oceanic crust. Leaching of rocks also contributes components to the hydrothermal fluid—a process enhanced where
Authors
Jeffrey W. Hedenquist, Jacob B. Lowenstern
The Loma Prieta, California, Earthquake of October 17, 1989: Strong ground motion
Strong ground motion generated by the Loma Prieta, Calif., earthquake (MS~7.1) of October 17, 1989, resulted in at least 63 deaths, more than 3,757 injuries, and damage estimated to exceed $5.9 billion. Strong ground motion severely damaged critical lifelines (freeway overpasses, bridges, and pipelines), caused severe damage to poorly constructed buildings, and induced a significant number of grou
Authors
Roger D. Borcherdt, A. Gerald Brady, A.F. Shakal, V.F. Cormier, Wei-Jou Su, Jeffry L. Stevens, Steven M. Day, John E. Vidale, Ornella Bonamassa, Paul G. Somerville, Nancy F. Smith, Robert Graves, Gary Glassmoyer, Kyle Rollins, Michael D. Mchood, Roman D. Hryciw, Matthew Homolka, Scott E. Shewbridge, Harvey Carlisle, Nicholas Sitar, Rodrigo Salgado, Pedro de Alba, J. Benoit, Daniel G. Pass, John Carter, T. Leslie Youd, E. H. Field, Susan E. Hough, K.H. Jacob, Paul A. Friberg, Arthur Frankel, R. Busby, Robert A. Williams, Edward Cranswick, Kenneth W. King, Grant T. Lindley, Ralph J. Archuleta, Janice M. Murphy, Steven G. Wesnousky
The Loma Prieta, California, earthquake of October 17, 1989: Tectonic processes and models
If there is a single theme that unifies the diverse papers in this chapter, it is the attempt to understand the role of the Loma Prieta earthquake in the context of the earthquake 'machine' in northern California: as the latest event in a long history of shocks in the San Francisco Bay region, as an incremental contributor to the regional deformation pattern, and as a possible harbinger of future
Authors
Robert W. Simpson, John H. Shaw, Richard E. Bischke, J. Suppe, Gianluca Valensise, Susan Y. Schwartz, Daniel L. Orange, Robert S. Anderson, Paul A. Reasenberg, Paul Bodin, Roger G. Bilham, Kevin P. Furlong, David Verdonck
Fluid expulsion sites on the Cascadia accretionary prism: mapping diagenetic deposits with processed GLORIA imagery
Point-discharge fluid expulsion on accretionary prisms is commonly indicated by diagenetic deposition of calcium carbonate cements and gas hydrates in near-surface (<10 m below seafloor; mbsf) hemipelagic sediment. The contrasting clastic and diagenetic lithologies should be apparent in side scan images. However, sonar also responds to variations in bottom slope, so unprocessed images mix topograp
Authors
Bobb Carson, Erol Seke, Valerie F. Paskevich, Mark L. Holmes