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Abstract
The Eureka area of northwestern California is characterized by a variety of terrain forms that reflect a variety of geologic materials, most of which are components of the highly disrupted and heterogeneous Franciscan Complex. Recent regional geologic mapping by McLaughlin and others (2000) has delineated the distribution of contrasting materials within the principal recognized units of the Franciscan, and so has revealed for the first time the intricate distribution of materials in much of the area. This geologic mapping was used by a mass-wasting review panel to select areas for detailed geomorphic mapping of landslide processes. Three study areas were chosen to represent the geologic and topographic diversity of timberlands in the broader area. In addition to abundant debris sliding, this mapping revealed that as much as 70 percent or more of this landscape shows evidence of large landslides of diverse scales and styles, ranging from fresh features produced by recent movement to subdued features suggestive of ancient movement followed by long quiescence. Several lines of evidence suggest that large landslide deposits in this area warrant monitoring for movement, as sediment contribution from subtle movement of these large masses in some areas could be comparable to that from debris sliding.
Parent Publication
Citation
Ellen, Stephen D.; de la Fuente, Juan; Falls, James N.; McLaughlin, Robert J. 2007. Overview of the Ground and Its Movement in Part of Northwestern California. In: Standiford, Richard B.; Giusti, Gregory A.; Valachovic, Yana; Zielinski, William J.; Furniss, Michael J., technical editors. 2007. Proceedings of the redwood region forest science symposium: What does the future hold? Gen. Tech. Rep. PSW-GTR-194. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture; p. 335-346
