Publications

Paleointensities are being determined in order to characterize geomagnetic intensity variations during Quaternary time. Because the geomagnetic field acts as a shield against cosmic radiation, its intensity directly affects the production rate of radiocarbon (^C) in the upper atmosphere. Coe and others (1978) showed that the variation in dipole moment during Holocene time is nearly...

No abstract available.

This field-trip guide was originally prepared for the 7th International Symposium on Water/Rock Interaction (WRI-7) held in July 1992 in Park City, Utah. A large and diversified group of earth scientists and accompanying family members participated in this 3 1/2-day field trip that focused on water/rock interactions over widely ranging temperatures and pressures in the Yellowstone/Grand...

In 1990, the State of Hawaii proposed the Hawaii Geothermal Project for the development of as much as 500 MW of electric power from the geothermal system in the East Rift Zone of Kilauea Volcano. This report uses data from 31 wells and 8 springs to describe the properties of the ground-water system in and adjacent to the East Rift Zone. Potential effects of this project on ground-water...

No abstract available.

The slides and the accompanying script presented here are based on a campground presentation at Chiricahua National Monument in 1994. Examples of eruptions at active volcanoes are used to help the audience visualize events that took place in the National Monument 27 million years ago. This presentation stresses the following themes: 1) The National Monument lies on the flank of an...

A significant seismic hazard exists in south Hawaii from large tectonic earthquakes that can reach magnitude 8 and intensity XII. This paper quantifies the hazard by estimating the horizontal peak ground acceleration (PGA) in south Hawaii which occurs with a 90% probability of not being exceeded during exposure times from 10 to 250 years. The largest earthquakes occur beneath active...

Quaternary volcanoes of the Cascade Range form a 1,200- kilometer-long arc that extends from southern British Columbia to northern California. The section of the Cascade Range volcanic arc in central Oregon is characterized by relatively high Quaternary volcanic extrusion rates and hot-spring discharge rates. Stableisotope data and measurements of hot-spring heat discharge indicate that...

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...

Data sets for spring and stream chemistry are combined to estimate convective heat discharge and discharge anomalous amounts of sodium and chloride for the Wood River group of springs south of Crater Lake. The best estimate of heat discharge is 87 MWt based on chloride inventory; this value is 3-5 times the heat input to Crater Lake itself. Anomalous discharges of sodium and chloride are...

We develop theoretically a description of a possible subglacial drainage mechanism for glaciers and ice sheets moving over saturated, deformable till. The model is based on the plausible assumption that flow of water in a thin film at the ice-till interface is unstable to the formation of a channelized drainage system, and is restricted to the case in which meltwater cannot escape...

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...