Proceedings of workshop XLIV; geological, geophysical, and tectonic setting of the Cascade Range

Abstract

VllNorthern California through Oregon and Washington to British Columbia. The intellectual scope was as broad and interdisciplinary as possible, with participants representing the fields of geology, heat flow, seismology, igneous petrology, hydrology, electromagnetic geophysics, magnetics, water geochemistry, gravity, paleomagnetism, and tectonics.The conference was organized around three major themes:Variations in tectonics, geophysical signature, and magmatism along the length of the Cascade volcanic arc.Relationship of the Cascade Range to the subduction tectonics to the west and to the continental tectonics to the east. Controls on the location, composition, and rates of magmatism in the Cascade Range. The 35 attendees were almost equally divided between USGS scientists and scientists from other research institutions, including universities, other federal agencies, state agencies, Canada, and Japan.This Redbook contains nearly all the presentations made at the 01-04 December 1988 Conference in Monterey. We do not intend or imply that it is the final word on the Cascade Range.Instead, its purpose is to release promptly the material presented at the December 01-04 Conference to other concerned investigators and to the public.Accordingly, we have not attempted to edit the contributions, even lightly. It is our plan, however, that each of the authors will revise his/her Redbook contribution in view of the other contributions and that the resultant papers will form the nucleus of a reviewed and edited special section of the Journal of Geophysical Research, hopefully to be published within the year.

Volcano and earthquake hazards in the Crater Lake region, Oregon

“…There is a significant variation in rates of modern seismicity along the Cascade Range, with the area south of Mount Hood in Oregon being quiet compared to other parts of the Cascades (Weaver, 1989). For example, a four station array along with an ultraportable outlier station operated in the summer of 1970 at Crater Lake found that there were fewer small events at Crater Lake than at Mount Hood and that no recorded events were deeper than 12 km (Westhusing, 1973).…”

Geothermal resources in the Crater Lake area, Oregon

“…There is a significant variation in rates of seismicity along the Cascade Range, with the area south of Mount Hood in Oregon being particularly quiet compared to other parts of the Cascades (Weaver, 1989). A four station array along with an ultraportable outlier station operated in the summer of 1970 at Crater Lake found that there were fewer small events at Crater Lake than at Mount Hood (Westhusing, 1973).…”

“…The climactic eruption took place over a few days, toward the end of which the caldera collapsed. This eruption produced a classic, compositionally zoned pyroclastic deposit that represents the rather orderly venting of a shallow, stratified magma body (Druitt and Bacon, 1986, 1989Bacon and Druitt, 1988). Pumiceous pyroclastic-flow deposits fill valleys around Mount Mazama to depths of -100 m ( Figure 2) and extend as much as 70 km from the caldera.…”

Time-evolving surface and subsurface signatures of Quaternary volcanism in the Cascades arc

“…Here, we combined a database of mapped Quaternary vents, surface topography, and diverse geophysical data sets within the Cascades arc (western North America) to probe relations between volcanism and underlying crustal structure. Building on prior efforts to synthesize geophysical (e.g., Weaver et al, 1989;Wells et al, 1998;Till et al, 2019) and geologic (e.g., Guffanti and Weaver, 1988;Hildreth, 2007) data in the Cascades arc, we analyzed (1) arc-scale relations among geophysical data sets associated with magmatism; (2) the extent to which volcanoes match geophysical subsurface magmatic signatures; and (3) temporal variations in these relations during the Quaternary.…”