Publications

The volcanic history of the Long Valley region is examined within a framework of six successive (spatially discrete) foci of silicic magmatism, each driven by locally concentrated basaltic intrusion of the deep crust in response to extensional unloading and decompression melting of the upper mantle. A precaldera dacite field (3.5–2.5 Ma) northwest of the later site of Long Valley and the Glass Mou

Basaltic fragments enclosed in andesitic dome lavas and pyroclastic flows erupted during the early stages of the 1991 eruption of Mount Pinatubo, Philippines, contain amphiboles that crystallized during the injection of mafic magma into a dacitic magma body. The amphiboles contain abundant melt inclusions, which recorded the mixing of andesitic melt in the mafic magma and rhyolitic melt in the dac

The Alaska-Aleutian island arc is well known for erupting both tholeiitic and calc-alkaline magmas. To investigate the relative roles of chemical and temporal controls in generating these contrasting liquid lines of descent we have undertaken a detailed study of tholeiitic lavas from Akutan volcano in the oceanic A1eutian arc and calc-alkaline products from Aniakchak volcano on the continental A1a

Basaltic glass grains from the submarine south flank of Kı̄lauea, Hawai′i, have Cl concentrations of 0.01–1.68 wt%, the latter being the highest Cl content yet recorded for a Hawaiian glass. The high-Cl glass grains are products of brine assimilation by tholeiite magma. The glasses are grains in a sandstone clast from bedded breccias draping the southwestern margin of Kı̄lauea’s submarine midslope

In this paper we examine the consequences of bubble nucleation mechanism on eruptive degassing of rhyolite magma. We use the results of published high temperature and pressure decompression experiments as input to a modified version of CONFLOW, the numerical model of Mastin and Ghiorso [(2000) U.S.G.S. Open-File Rep. 00-209, 53 pp.] and Mastin [(2002) Geochem. Geophys. Geosyst. 3, 10.1029/2001GC00

Field mapping of young lava flows at Aleutian volcanoes is logistically difficult, and the utility of optical images from aircraft or satellites for this purpose is greatly reduced by persistent cloud cover. These factors have hampered earlier estimates of the areas and volumes of three young lava flows at Westdahl Volcano, including its most recent (1991–1992) flow. We combined information from s

The age of the Rockland tephra, which includes an ash-flow tuff south and west of Lassen Peak in northern California and a widespread ash-fall deposit that produced a distinct stratigraphic marker in western North America, is constrained to 565,000 to 610,000 yr by 40Ar/39Ar and U–Pb dating. 40Ar/39Ar ages on plagioclase from pumice in the Rockland have a weighted mean age of 609,000 ± 7000 yr. Is

The Taupo Volcanic Zone (TVZ), New Zealand is a region characterized by very high magma eruption rates and extremely high heat flow, which is manifest in high-temperature geothermal waters. The shear wave velocity structure across the region is inferred using non-linear inversion of receiver functions, which were derived from teleseismic earthquake data. Results from the non-linear inversion, and

Mayon is the most active volcano along the east margin of southern Luzon, Philippines. Petrographic and major element data indicate that Mayon has produced a basaltic to andesitic lava series by fractional crystallization and magma mixing. Trace element data indicate that the parental basalts came from a heterogeneous mantle source. The unmodified composition of the mantle wedge is similar to that

We describe an event tree scheme to quantitatively estimate both long- and short-term volcanic hazard. The procedure is based on a Bayesian approach that produces a probability estimation of any possible event in which we are interested and can make use of all available information including theoretical models, historical and geological data, and monitoring observations. The main steps in the proc

Radial Semblance is applied to broadband seismic network data to provide source locations of Very-Long-Period (VLP) seismic energy in near real time. With an efficient algorithm and adequate network coverage, accurate source locations of VLP energy are derived to quickly locate the shallow magmatic conduit system at Kilauea Volcano, Hawaii. During a restart in magma flow following a brief pause in

The 3 November 2002 Mw 7.9 Denali fault earthquake provided an excellent opportunity to investigate triggered earthquakes at Alaskan volcanoes. The Alaska Volcano Observatory operates short-period seismic networks on 24 historically active volcanoes in Alaska, 247-2159 km distant from the mainshock epicenter. We searched for evidence of triggered seismicity by examining the unfiltered waveforms fo