Publications
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The threat of silent earthquakes
Not all earthquakes shake the ground. The so-called silent types are forcing scientists to rethink their understanding of the way quake-prone faults behave. In rare instances, silent earthquakes that occur along the flakes of seaside volcanoes may cascade into monstrous landslides that crash into the sea and trigger towering tsunamis. Silent earthquakes that take place within fault zones created b
Authors
Peter Cervelli
Magmatic precursors to the 18 May 1980 eruption of Mount St. Helens, USA
Perhaps the most difficult task facing volcanologists today is that of distinguishing between low-level volcanic restlessness and activity that presages a full-scale eruption. We illustrate these difficulties by reexamining the sequence of events that led to the 18 May 1980 eruption of Mount St. Helens, activity that is often presented as a classic example of early phreatic explosions leading to a
Authors
K. V. Cashman, R. P. Hoblitt
Non-double-couple microearthquakes at Long Valley caldera, California, provide evidence for hydraulic fracturing
Most of 26 small (0.4≲M≲3.1) microearthquakes at Long Valley caldera in mid-1997, analyzed using data from a dense temporary network of 69 digital three-component seismometers, have significantly non-double-couple focal mechanisms, inconsistent with simple shear faulting. We determined their mechanisms by inverting P- and S-wave polarities and amplitude ratios using linear-programming methods, and
Authors
G. R. Foulger, B. R. Julian, D. P. Hill, A. M. Pitt, P.E. Malin, E. Shalev
Rear-arc vs. arc-front volcanoes in the Katmai reach of the Alaska Peninsula: A critical appraisal of across-arc compositional variation
Physical and compositional data and K-Ar ages are reported for 14 rear-arc volcanoes that lic 11-22 km behind the narrowly linear volcanic front defined by the Mount Katmai-to-Devils Desk chain on the Alaska Peninsula. One is a 30-km3 stratocone (Mount Griggs; 51-63% SiO2) active intermittently from 292 ka to Holocene. The others are monogenetic cones, domes, lava flows, plugs, and maars, of which
Authors
W. Hildreth, J. Fierstein, D. F. Siems, J. R. Budahn, J. Ruiz
Reaction rim growth on olivine in silicic melts: Implications for magma mixing
Finely crystalline amphibole or pyroxene rims that form during reaction between silicic host melt and cognate olivine xenocrysts, newly introduced during magma mixing events, can provide information about the timing between mixing and volcanic eruptions. We investigated rim growth experimentally by placing forsteritic olivine in rhyolitic and rhyodacitic melts for times between 25 and 622 h at 50
Authors
Michelle L. Coombs, James E. Gardner
Noise in two-color electronic distance meter measurements revisited
Frequent, high-precision geodetic data have temporally correlated errors. Temporal correlations directly affect both the estimate of rate and its standard error; the rate of deformation is a key product from geodetic measurements made in tectonically active areas. Various models of temporally correlated errors are developed and these provide relations between the power spectral density and the dat
Authors
J. Langbein
Decompression experiments identify kinetic controls on explosive silicic eruptions
Eruption intensity is largely controlled by decompression‐induced release of water‐rich gas dissolved in magma. It is not simply the amount of gas that dictates how forcefully magma is propelled upwards during an eruption, but also the rate of degassing, which is partly a function of the supersaturation pressure (ΔPcritical) triggering gas bubble nucleation. High temperature and pressure decompres
Authors
M. T. Mangan, T. W. Sisson, W.B. Hankins
Renewed unrest at Mount Spurr Volcano, Alaska
The Alaska Volcano Observatory (AVO),a cooperative program of the U.S. Geological Survey, the University of Alaska Fairbanks Geophysical Institute, and the Alaska Division of Geological and Geophysical Surveys, has detected unrest at Mount Spurr volcano, located about 125 km west of Anchorage, Alaska, at the northeast end of the Aleutian volcanic arc.This activity consists of increased seismicity
Authors
John A. Power
Growth and collapse of Waianae volcano, Hawaii, as revealed by exploration of its submarine flanks
Wai‘anae Volcano comprises the western half of O‘ahu Island, but until recently little was known about the submarine portion of this volcano. Seven new submersible dives, conducted in 2001 and 2002, and multibeam bathymetry offshore of Wai‘anae provide evidence pertaining to the overall growth of the volcano's edifice as well as the timing of collapses that formed the Wai‘anae slump complex. A pro
Authors
Michelle L. Coombs, David A. Clague, Gregory F. Moore, Brian L. Cousens
1999 Volcanic activity in Alaska and Kamchatka: Summary of events and response of the Alaska Volcano Observatory
The Alaska Volcano Observatory (AVO) monitors 41 historically active volcanoes along the Aleutian Arc. Twenty are seismically monitored and for the rest, the AVO monitoring program relies mainly on daily analysis of satellite images, pilot reports, and observations of local residents and ship's crews. In 1999, AVO responded to eruptive activity or suspect volcanic activity at 7 volcanic centers: W
Authors
Robert G. McGimsey, Christina A. Neal, Olga Girina
Complex proximal deposition during the Plinian eruptions of 1912 at Novarupta, Alaska
Proximal (<3 km) deposits from episodes II and III of the 60-h-long Novarupta 1912 eruption exhibit a very complex stratigraphy, the result of at least four transport regimes and diverse depositional mechanisms. They contrast with the relatively simple stratigraphy (and inferred emplacement mechanisms) for the previously documented, better known, medial-distal fall deposits and the Valley of Ten T
Authors
Bruce F. Houghton, C. J. N. Wilson, J. Fierstein, W. Hildreth
A 2000-year-long record of climate from the Gulf of California
No abstract available.
Authors
John A. Barron, David Bukry, James L. Bischoff