Geoscience Horizons

Postmeeting Field Trips

17. Evolution of a Polygenetic Ophiolite: The Jurassic Ingalls Ophiolite, Washington Cascades [417]
Wed.-Fri., Nov. 5-7.
Gregory Harper, Dept. of Earth and Atmospheric Sciences, SUNY, Albany, NY 12222, (518) 442-4476, fax 518-442-5825; Robert Miller; Jonathan Miller. Minimum: 12. Maximum: 30. Cost: $250 (2L, R, 2ON, vans).
We will examine a high-T mantle shear zone (fracture zone?), intrusive and extrusive mafic rocks, argillite containing ophiolite breccias, and post(?)-ophiolite dikes. We will discuss tectonic models in light of new stratigraphic, structural, geochemical, paleontologic, and radiometric age data, including the hypothesis that the ophiolite consists of older oceanic basement that was rifted in a Middle-to-Late Jurassic suprasubduction zone setting.
18. Geohydrology of the Hanford Nuclear Waste Site in the South-Central Columbia Plateau [418]
Wed.-Fri., Nov. 5-7.
Roy E. Gephart, Pacific Northwest National Laboratory, P.O. Box 999, MS K8-88, Richland, WA 99352, (509) 376-1421, fax 509-376-0846; Steve Reidel; Frank Spane; Karl Fecht. Minimum: 7. Maximum: 20. Cost: $240 (2L, R, 2 ON, vans). Due to security restrictions, only U.S. citizens can enter the Hanford Site on this tour.
This field trip provides an overview of the geohydrologic setting of the Hanford Site and its impact on contamination and waste cleanup at the former U.S. Department of Energy weapons site in south-central Washington State.
19. Puget Sound Paleoseismology [419]
Thurs.-Fri., Nov. 6-7.
Brian Sherrod, U.S. Geological Survey, Dept. of Earth and Space Sciences, Box 351310, University of Washington, Seattle, WA 98195, (206) 553-0153, fax 206-553-8350; Alan Nelson; Harvey Kelsey; Carrie Garrsion-Laney. Minimum: 12. Maximum: 45. Cost: $170 (2L, R, vans).
On this Seattle-based two-day trip, we will view geologic evidence for Holocene earthquakes on shallow faults in the Puget Sound Lowland. Evidence includes terraces recording coastal uplift along the Seattle and Tacoma faults and scarps from surface faulting recently discovered on LIDAR maps. Some evidence suggests that a large earthquake about 1100 years ago was shortly preceded by other large earthquakes.
20. Hydrogeology of Cascade Range Volcanoes: Mount St. Helens, Mount Hood, and Central Oregon [420]
Thurs.-Sat., Nov. 6-8. Cosponsored by GSA Hydrogeology Division.
Steve Ingebritsen, U.S. Geological Survey, MS 439, 345 Middlefield Road, Menlo Park, CA 94025, (650) 329-4422, fax 650-329-4463; Terry Keith; Michael Manga; Larry Mastin. Minimum: 12. Maximum: 40. Cost: $370 (2B, 3L, 2D, R, 2ON, vans).
This scenic field trip will explore the hydrogeology of the Cascade Range volcanic arc in southern Washington and north-central Oregon. We will depart from Seattle early Thursday morning and spend much of the day at Mount St. Helens, lodging in northern Oregon near Estacada. On Friday, we will investigate the north-central Oregon Cascades and lodge at Sisters, Oregon. Saturday, we will visit Mt. Hood and return to Seattle in time to catch late evening return flights.
21. Quaternary Geology of Seattle [421]
Thurs., Nov. 6. Cosponsored by GSA Quaternary Geology and Geomorphology Division.
Kathy Goetz Troost, Dept. of Earth and Space Sciences, University of Washington, Box 351310, Seattle, WA 98195-1310, (206) 616-9769, fax 206-543-8954; Derek Booth; Bill Laprade. Minimum: 12. Maximum: 45. Cost: $105 (1L, R, bus).
On this field trip, we will visit representative sites to view the Quaternary geology of Seattle. The city lies in a unique geologic setting near a subducting plate, having been glaciated more than six times in the last two million years. The area is geologically very young and very complex. Because of this setting, the area is subject to abundant geologic hazards, such as volcanic activity, earthquakes, faulting, landslides, liquefaction, and other ground failures. Even though an urban center may seem an improbable place to find any geologic exposures, much less a rich geologic story, examples abound here.

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