Lithology and Stratigraphy
This subsection is on predominantly Mesozoic and Tertiary marine sedimentary rocks over granitic basement of the Salinian block that is exposed on Montara Mountain. The Tertiary sedimentary rocks are Eocene, Oligocene, Miocene, and Pliocene. There are relatively smaller areas Miocene volcanic rocks, Quaternary marine terraces, and late Quaternary or recent alluvium.
This is a subsection of northwest trending mountains with rounded ridges, steep sides, and narrow canyons. The crest of the mountain range is near the northeast edge of the mountain range, parallel to the San Andreas Fault, which is along the northeast side of the Santa Cruz Mountains. Most of the streams drain toward the southwest. There are some dissected marine terraces along the coast, and some recent alluvium on narrow floodplains and terraces. The subsection elevation range is mostly from sea-level to about 2000 feet, and up to 3231 feet on Castle Rock Ridge. Mass wasting and fluvial erosion are the main geomorphic processes.
The soils are mostly Pachic Ultic Haploxerolls, Dystric Lithic Xerochrepts, Ultic Haploxerolls, and Ultic Argixerolls with mesic soil temperature regimes; Pachic Haploxerolls and Typic Argixerolls with thermic soil temperature regimes; and Lithic Haplustolls, Ustic Dystropepts, Pachic Hapustolls and Argiustolls, Ultic Haplustalfs, and Ultic Tropudalfs with isomesic soil temperature regimes. In granitic terrain of Montara Mountain the soils are mostly Lithic and Typic Haplu-stolls and Pachic Argixerolls. On marine terraces, the soils are mostly Xeric Argialbolls, Pachic Argixerolls, and Mollic Palexeralfs. The soils are well drained, and most are leached free of carbonates. Soil temperature regimes are mostly mesic and isomesic, with some thermic. Soil moisture regimes are mostly ustic and xeric (nearly ustic), and some are udic.
The predominant natural plant communities are Redwood series and Douglas-fir - tanoak series. Coast live oak series is common on the northeast side of the mountains. California oatgrass series and Coyote brush series are common adjacent to the coast, and Yellow bush lupine series is present on stabilized dunes. Chamise series and Manzanita shrublands are common on shallow soils and on south-facing slopes.
Characteristic series by lifeform include:
- Dune vegetation: Dune lupine - goldenbrush series, Native dunegrass series, Sand-verbena - beach bursage series, Yellow bush lupine series.
Grasslands: California annual grassland series, California oatgrass series, Introduced perennial grassland series, Pacific reedgrass series.
Shrublands: Blue blossom series, California sagebrush series, Chamise series, Coyote brush series, Deer brush series, Woollyleaf manzanita series.
Forests and woodlands: California bay series, Coast live oak series, Douglas-fir - tanoak series, Douglas-fir series, Knobcone pine series, Ponderosa pine series, Redwood series, Santa Cruz cypress stands.
The mean annual precipitation is about 20 to 60 inches. It is practically all rain, except for some snow on at higher elevations. Summer fog is common. Mean annual temperature is about 50° to 58° F. The mean freeze-free period is about 250 to 300 days. Surface Water. Runoff is rapid and streams on the northeast side of the mountains are generally dry during the summer, but streams on the seaward side are generally perennial. There are natural lakes, or sag ponds, in the San Andreas fault zone, and ponds behind dunes along the coast.