Publications
Filter Total Items: 3006
Observed discrepancy between geodolite and GPS distance measurements Observed discrepancy between geodolite and GPS distance measurements
Comparison of contemporaneous measurements of 84 distances in the range of 10 to 50 km by both Global Positioning System (GPS) and Geodolite (an electro-optical distance-measuring instrument) indicates that the Geodolite measurements are systematically longer by 0.283 ± 0.100 parts per million of the measured distance. Quoted uncertainty is 1 standard deviation. This amounts to 11.3 ± 4...
Authors
J.C. Savage, M. Lisowski, W.H. Prescott
Differentiation and magma mixing on Kilauea's east rift zone: A further look at the eruptions of 1955 and 1960. Part II. The 1960 lavas Differentiation and magma mixing on Kilauea's east rift zone: A further look at the eruptions of 1955 and 1960. Part II. The 1960 lavas
New and detailed petrographic observations, mineral compositional data, and whole-rock vs glass compositional trends document magma mixing in lavas erupted from Kilauea's lower east rift zone in 1960. Evidence includes the occurrence of heterogeneous phenocryst assemblages, including resorbed and reversely zoned minerals in the lavas inferred to be hybrids. Calculations suggest that this...
Authors
T. L. Wright, Rosalind Tuthill Helz
Long-term geochemical surveillance of fumaroles at Showa-Shinzan dome, Usu volcano, Japan Long-term geochemical surveillance of fumaroles at Showa-Shinzan dome, Usu volcano, Japan
This study investigates 31 years of fumarole gas and condensate (trace elements) data from Showa-Shinzan, a dacitic dome-cryptodome complex that formed during the 1943-1945 eruption of Usu volcano. Forty-two gas samples were collected from the highest-temperature fumarole, named A-1, from 1954 (800??C) to 1985 (336??C), and from lower-temperature vents. Condensates were collected...
Authors
R.B. Symonds, Y. Mizutani, Paul H. Briggs
Mauna Loa lava accumulation rates at the Hilo drill site: Formation of lava deltas during a period of declining overall volcanic growth Mauna Loa lava accumulation rates at the Hilo drill site: Formation of lava deltas during a period of declining overall volcanic growth
Accumulation rates for lava flows erupted from Mauna Loa, as sampled in the uppermost 280 m of the Hilo drill hole, vary widely for short time intervals (several thousand years), but overall are broadly similar to those documented elsewhere on this volcano since 100 ka. Thickness variations and accumulation rates for Mauna Loa lavas at the Hilo drill site have been strongly affected by...
Authors
P. W. Lipman, J.G. Moore
Chemical and isotopic characteristics of fluids along the cameroon volcanic line, cameroon Chemical and isotopic characteristics of fluids along the cameroon volcanic line, cameroon
Results of the chemical and isotopic analysis of the water and gases discharged from volcanic crater lakes and soda springs located along the Cameroon Volcanic Line were used to characterize and infer their genetic relationships. Variations in the solute compositions of the waters indicate the dominant influence of silicate hydrolysis. Na+ (40-95%) constitutes the major cation in the...
Authors
G.Z. Tanyileke, M. Kusakabe, William C. Evans
Kulshan caldera: A quaternary subglacial caldera in the North Cascades, Washington Kulshan caldera: A quaternary subglacial caldera in the North Cascades, Washington
Calderas that collapse during large pyroclastic eruptions are anomalously rare in the Cascade arc. Recognition of the early Pleistocene 4.5 × 8 km Kulshan caldera, filled with rhyodacite ignimbrite at the northeast foot of Mount Baker, brings to only three the Quaternary calderas identified in the Cascades. A near-vertical ring fault cut in basement rocks of the North Cascades encloses...
Authors
W. Hildreth
This dynamic earth: the story of plate tectonics This dynamic earth: the story of plate tectonics
In the early 1960s, the emergence of the theory of plate tectonics started a revolution in the earth sciences. Since then, scientists have verified and refined this theory, and now have a much better understanding of how our planet has been shaped by plate-tectonic processes. We now know that, directly or indirectly, plate tectonics influences nearly all geologic processes, past and...
Authors
W. Jacquelyne Kious, Robert I. Tilling
Volcanic activity in Alaska and Kamchatka: Summary of events and response of the Alaska Volcano Observatory 1995 Volcanic activity in Alaska and Kamchatka: Summary of events and response of the Alaska Volcano Observatory 1995
The Alaska Volcano Observatory (AVO) responded to eruptive activity or suspected volcanic activity (SVA) at 6 volcanic centers in 1995: Mount Martin (Katmai Group), Mount Veniaminof, Shishaldin, Makushin, Kliuchef/Korovin, and Kanaga. In addition to responding to eruptive activity at Alaska volcanoes, AVO also disseminated information for the Kamchatkan Volcanic Eruption Response Team...
Authors
Robert G. McGimsey, Christina A. Neal
Aeromagnetic map of the Clear Lake region on parts of the Santa Rosa and Ukih 1° by 2° quadrangles, California Aeromagnetic map of the Clear Lake region on parts of the Santa Rosa and Ukih 1° by 2° quadrangles, California
No abstract available.
Authors
Water Resources Division U.S. Geological Survey
Provisional geologic map of Augustine Volcano, Alaska Provisional geologic map of Augustine Volcano, Alaska
No abstract available.
Authors
R. B. Waitt, J. E. Beget, Juergen Kienle
The Loma Prieta, California, Earthquake of October 17, 1989: Main shock characteristics The Loma Prieta, California, Earthquake of October 17, 1989: Main shock characteristics
The October 17, 1989, Loma Prieta, Calif., earthquake (0004:15.2 G.m.t. October 18; lat 37.036º N., long 121.883º W.; 19-km depth) had a local magnitude (ML) of about 6.7, a surface-wave magnitude (MS) of 7.1, a seismic moment of 2.2x1019 N-m to 3.5x1019 N-m, a source duration of 6 to 15 s, and an average stress drop of at least 50 bars. Slip occurred on a dipping fault surface about 35...
Authors
Paul A. Spudich, Gregory C. Beroza, George Choy, John Boatwright, Stephen H. Hartzell, Gordon L. Stewart, Carlos Mendoza, Stephen Horton, John G. Anderson, Andres J. Mendez, Hiroo Kanamori, Kenji Satake, Michael Lisowski, Mark Hunter Murray, Jerry L. Svarc, Grant Marshall, Ross S. Stein, Karen McNally, Gerald W. Simila, Judy G. Brown, J.L. Nabelek, Ze’ev Reches, Mark D. Zoback, Jamison Steidl, Ralph J. Archuleta, Aaron A. Velasco, Thorne Lay, Jiajun Zhang, David J. Wald, Donald V. Helmberger, Thomas H. Heaton, Chesley R. Williams, Paul Segall, Francis T. Wu, Mingdong Wu, J.W. Rudnicki
Channel adjustment of an unstable coarse-grained stream: Opposing trends of boundary and critical shear stress, and the applicability of extremal hypotheses Channel adjustment of an unstable coarse-grained stream: Opposing trends of boundary and critical shear stress, and the applicability of extremal hypotheses
Channel adjustments in the North Fork Toutle River and the Toutle River main stem were initiated by deposition of a 2.5km3 debris avalanche and associated lahars that accompanied the catastrophic eruption of Mount St. Helens, Washington on 18 May 1980. Channel widening was the dominant process. In combination, adjustments caused average boundary shear stress to decrease non-linearly with...
Authors
Andrew Simon, Colin R. Thorne