NEHRP Clearinghouse
- Title
- Hillside Materials and Slopes of the San Francisco Bay Region.
- File
- PB2006105319.pdf
- Author(s)
- Ellen, S. D.; Wentworth, C. M.
- Source
- January 1995, 223 p.
- Identifying Number(s)
- USGS/PP-1357
- Abstract
- Hillsides in the San Francisco Bay region differ in slope of the ground surface and in the kinds of materials beneath the ground surface. These differences affect engineering use of the land in several ways, including the volume and ease of grading needed to provide flat space for roads and foundations, the stability of that grading, the success of water wells and septic tank systems, and the susceptibility to geologic hazards such as landsliding and earthquake shaking. This report systematically describes the materials and slopes of hillsides in nine counties (Alameda, Contra Costa, Maria, Napa, San Francisco, San Mateo. Santa Clara. Solano, and Sonoma) that constitute the bay region, so that land-use advantages or problems can be anticipated. Hillside materials in the region range from soft, young stratified rock to older and harder stratified rock, volcanic rock, hard homogeneous rock, and chaotically mixed assemblages of hard and soft rock. The distribution of these materials is shown on 1:125,000-scale maps based on geologic mapping of the region.
- Keywords
- Hillside materials; Materials units; Weathering phases; California; Physical properties; Unit descriptions; San Francisco Bay region; Stratigraphic thickness; Slopes; Composition