Publications

No abstract available.

No abstract available.

Nonhydrated obsidians are quenched magmatic liquids that record in their chemical compositions details of the tectonic environment of formation and of the differentiation mechanisms that affected their subsequent evolution. This study attempts to analyze, in terms of geologic processes, the compositional variations in the subalkalic silicic obsidians (Si02≥70 percent by weight, molecular (Na2O+K20

The seven volcanoes comprising the island of Hawaii and its submarine base are, in order of growth, Mahukona, Kohala, Mauna Kea, Hualalai, Mauna Loa, Kilauea, and Loihi. The first four have completed their shield-building stage, and the timing of this event can be determined from the depth of the slope break associated with the end of shield building, calibrated using the ages and depths of a seri

Rare melt inclusions ~ 100 μm in diameter trapped near the boundaries of corroded patchy zones in plagioclase phenocrysts from Plinian pumice of three Holocene eruptions were analyzed by IR spectroscopy for molecular H2O, OH groups, and CO2and by electron microprobe for Cl and F. The three rhyodacitic eruptions, each of which began with a Plinian phase, occurred over ~200 yr. The Llao Rock and Cle

This map of the Cold Bay and False Pass 1:250,000-scale quadrangles on the Alaska Peninsula is a compilation based in part on the mapping conducted as part of the Alaska Mineral Resource Assessment Program (AMRAP) and the Geothermal Energy Program. Field studies by the authors began as early as 1973 in the quadrangles, but systematic mapping was not begun until 1988. Systematic mapping remains to

Garnet/liquid trace element partition coefficients have been measured in situ by ion microprobe in a rhyolite from Monache Mountain, California. Partition coefficients are reported for La, Ce, Nd, Sm, Dy, Er, Yb, Sc, Ti, V, Cr, Sr, Y, and Zr. The in situ analyses avoid the problem of contamination of the garnet phase by trace element-rich accessory minerals encountered in traditional bulk phenocry

Kilauea is nearing the 10th year of its most voluminous rift zone eruption in the last 2 centuries. Lava flows have covered 75 km2 to depths as great as 25 m and have added almost 1.2 km2 of new land to the island. These flows have devastated downslope communities and have provided a painful tutorial for local government in planning for and living with volcanic hazards [Heliker and Wright, 1991].

The pattern of historical ground deformation, seismicity, and crustal structure near Medicine Lake volcano illustrates a close relation between magmatism and tectonism near the margin of the Cascade volcanic chain and the Basin and Range tectonic province. Between leveling surveys in 1954 and 1989 the summit of Medicine Lake volcano subsided 389±43 mm with respect to a reference bench mark 40 km t

Within the neovolcanic zones of Iceland many volcanoes grew upward through icecaps that have subsequently melted. These steep-walled and flat-topped basaltic subglacial volcanoes, called tuyas, are composed of a lower sequence of subaqueously erupted, pillowed lavas overlain by breccias and hyaloclastites produced by phreatomagmatic explosions in shallow water, capped by a subaerially erupted lava

No abstract available.

The submarine Mahukona Volcano, west of the island of Hawaii, is located on the Loa loci line between Kahoolawe and Hualalai Volcanoes. The west rift zone ridge of the volcano extends across a drowned coral reef at about-1150 m and a major slope break at about-1340 m, both of which represent former shoreines. The summit of the volcano apparently reached to about 250 m above sea level (now at-1100