Littoral Cave Development on the Western U.S. Coast

Abstract

Sea caves have been documented in all four states on the Pacific coast of the United States. By far the most extensive written documentation, along with cave surveys, is from California due to the efforts of the California Sea Cave Survey since the early 1980s. The largest concentration of sea caves there are those in the Channel Islands of southern California, where over 15 km has been surveyed in 380 caves. Painted Cave on Santa Cruz Island is one of the world’s largest at 375 m in length. But large caves are also known from the central California counties of Santa Cruz, San Luis Obispo, and Mendocino. Currently Sea Lion Caves in Oregon is the longest known on the Pacific coast of the U.S. at 401 m, as well as one of the world's longest, and among the few sea caves in Oregon with survey data available. Sea caves are known from several other regions in the state. Washington State has scattered areas with sea caves and few surveyed, with perhaps the largest concentration at Cape Flattery on its northwestern tip. Alaska has seen some significant survey activity resulting in documentation of a few dozen caves. Potential is great there for some large sea caves to be explored in the future, especially in the Aleutian Islands. Southeast Alaska contains the best documented caves to date, some within carbonate rocks with speleothems and some now found well above the current littoral zone due to uplift following retreat of coastal glaciers. The latter has resulted in more caves with archaeological significance since their drier environment was more hospitable as shelter than is typical of littoral caves in the region. Few such uplifted caves are known in the other Pacific states other than some well-documented Channel Islands caves.