Crescent City Plain
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Geology (main)
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Coastal zone at the mouth of the Smith River, California. Creative Commons
The Crescent City Plain subsection is situated on a coastal plain between mountains of the Northern California Coast Ranges and the Pacific Ocean. The mouth of the Smith River, which drains from the Klamath Mountains, is on this coastal plain. It has a temperate, humid climate with much summer fog. The U.S. Forest Service designation for this subsection is MLRA 4b.
Subsection 263Aa, Lake Earl area (James R. Nelson) Contents
Lithology and Stratigraphy
This subsection, situated in the far northern coastal area of California, contains predominantly Quaternary nonmarine and marine sand and clay coastal plain deposits of the Battery formation. Also, there are substantial areas of beach and dune deposits along the ocean shoreline and recent alluvium and Quaternary fluvial terraces along the Smith River.
Geomorphology
This subsection is on a nearly level [[coastal] plain] adjacent to the ocean. Beaches line the outer edge of the plain and dunes of sand spread inland from the beaches. Water is ponded on the plain behind the dunes and backshore: moreover, a large lake occupies much of the plain. The entire plain is less than 200 feet above mean sea-level. Ocean currents, waves, and wind (coastal marine and aeolian processes) are active in forming the beaches and dunes. Fluvial and erosion is the main geomorphic processes on the plain behind the beaches and on terraces along the Smith River.
Soils
The soils are mostly Typic Tropohumults and Typic Humitropepts. Udifluvents and Fluvaquents are common soils on recent alluvium. Tropopsamments occur on dunes. The soil temperature regimes are isomesic. Soil moisture regimes are primarily udic, and some aquic.
Vegetation
The predominant natural plant communities on the plain are Sitka spruce series on the outer edge and Redwood series inland. Red alder series is common in riparian areas. The dunes support a Succession of plant communities, from bare dune through Native dunegrass series, Sand - verbena - beach bursage series, and Beach pine series to Sitka spruce series. Pickleweed series predominates in saltmarshes.
Characteristic series by lifeform include:
- Dune vegetation: Native dunegrass series, European beachgrass series, Sand - verbena - beach bursage series.
- Saltmarsh vegetation: Pickleweed series, Saltgrass series.
- Grasslands: Introduced perennial grassland series.
- Shrublands: Coyote brush series, Salal - California huckleberry series.
- Forests and woodlands: Beach pine series, Red alder series, Redwood series, Sitka spruce series.
Climate
The mean annual precipitation is about 60 to 80 inches; there is much summer fog. Mean annual temperature is about 53°F, and there is less than 14°F difference between lowest and highest monthly means. The mean freeze-free period is about 300 days.
Surface Water
Water is ponded on the coastal plain to form lakes, with the largest being Lake Earl. The Smith River, a large distributary from the Klamath Mountains, has an outlet on the Plain. Tidal water enters the mouth of the Smith River and may spill over into some of the lakes.
References
- National Park Service. 2006. "Smith River California". National Wild and Scenic Rivers System.
- Stare of California. 2003, Draft Environmental Impact Report, Lake Earl Wildlife Area SCH No. 1989013110, California State Clearinghouse, Sacramento, CA
- State of California. 1974. State Water Resources Control Board Water Quality Control Policy for the Enclosed Bays and Estuaries of California
- U.S.Forest Service. Crescent City Plain
