- West Coast of the United States (Wikipedia)
The West Coast of the United States, also known as the Pacific Coast and the Western Seaboard, is the coastline along which the Western United States meets the North Pacific Ocean. The term typically refers to the contiguous U.S. states of California, Oregon, and Washington, but it occasionally includes Alaska and Hawaii in bureaucratic usage. For example, the U.S. Census Bureau considers both states to be part of a larger U.S. geographic division.
- Tukwila Formation—Andesitic to dacitic volcanic sandstone, siltstone, shale, tuff-breccia, tuff, volcanic mudflow (lahar), carbonaceous shales, and minor lava flows or sills. Typically massive; only local sedimentary interbeds indicate structure. K-Ar age on plagioclase from tuff-breccia at top of unit, about 3 km west of quadrangle, yielded an age of 42.0±2.4 Ma (Turner and others, 1983)