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The Ore Bin ; Vol. 38 No. 11 (November 1976)
No full textThe Columbia River Basalt consists of dozens of seemingly identical flows of basalt covering thousands of square miles of Oregon, Washington, and Idaho. For years, detailed mapping of the units relied almost entirely on subtle petrographic distinctions, the presence or absence of interbeds, and actual walking along contacts in the field. Eventually two divisions were recognized: Yakima Basalt and Picture Gorge Basalt. Further detailed work in southeastern Washington revealed distinctive and laterally continuous flows within the Yakima Basalt. In recent years, geochemical and geophysical techniques have been used to supplement more traditional geologic approaches, allowing geologists to map with much greater precision. The paleomagnetic technique described in this article illustrates how new technology is assisting the geologist in his work
The Ore Bin ; Vol. 34 No. 5 (May 1972)
No full textThe Oregon Coast between Yachats and Newport is a narrow, slightly elevated coastal plain. With the exceptions of basalt rock at Yachats and Seal Rock, the bedrock along this segment of the coast is sedimentary. Several Pleistocene marine terrace levels are discernible at places along the plain, and sand dunes, both active and stabilized, impart a rolling topography to most of it. Numerous streams have incised small valleys and ravines into its surface; at Waldport the plain is interrupted by the estuary of the Alsea River and at Ona Beach State Park by the alluvial plain of Beaver Creek. Except in the two localities where basalt is exposed, the shore is marked by long stretches of sandy beaches bounded by low sea cliffs. Where the basalt is exposed, the shore has the rugged features that are characteristic of Oregon shores bounded by this type of rock
The Ore Bin ; Vol. 38 No. 5 (May 1976)
No full textAverage annual losses caused by geologic hazards in Oregon are difficult to determine, owing to incomplete and scattered data. Preliminary considerations, however, indicate that losses to landslides may total between 40 million per year. As many as nine persons have been killed by one landslide in Oregon in recent years. Losses through coastal retreat have totaled millions of dollars as large parts of major communities have been destroyed. Tsunami damage totals approximately 36 million per year by the year 2000. Because this hazard is so large and complex, it is dealt with by several state and Federal agencies. Volcanic and earthquake hazards constitute long-range threats, with the potential for catastrophic consequences. Specific identifications of these hazards and long-range mitigative efforts can reduce the risk considerably. It is the aim of a good hazards investigation to regard not only the historic distribution of hazards but also the causes and the distribution of hazardous antecedent conditions. The net result is the generation of information that is more than purely a descriptive account of past events, but which is also a predictive tool for evaluating the impacts of contemplated changes in land use. In this way, the information becomes a powerful land-management tool. Effective mitigation and planning can only proceed on a firm foundation of accurate hazards analysis and mapping. The aim of the geologic hazards program at the Oregon Department of Geology and Mineral Industries is to provide objective and accurate data, free of personal value judgments. The purpose is to provide government with an array of appropriate uses for land in hazardous areas, based on adequate information and on unbiased investigation