mountain range, the South Coast is protected from the predominant northwesterly weather systems. The Channel Islands modify the effects of these systems and buffer the effects of the moisture-bearing southerly influences. Thus our South Coast climate is generally predictable in its moderate temperatures, strong winds in spring, coastal fog that reaches the foothills, and a rainy season compressed between November and April.

While impacts upon the land from major weather systems are muted relative to the North Coast, extreme events nevertheless occur and, as elsewhere on the South Coast, they have left clear traces on San Marcos Foothills. Fire is only the most dramatic of these. Temperatures in excess of 100° with high winds occur once every few years, scorching plants and killing livestock. Below freezing temperatures can destroy agricultural vegetation. Torrential rains from 2" to 3" per hour cause massive flooding and immense soil deposition in residential areas and coastal wetlands. Although the mean rainfall is approximately 17" per year, annual rainfall ranges from half that to more than double the mean. All these variable forces of nature have left their unmistakable marks on these acres.

Like the foothills all along the coast, these particular foothills have also taken their dynamic shape from the slow passage of time. Two major east-west geologic faults account for the lifting and lowering of our landscape. The Santa Ynez Fault runs roughly along the Santa Ynez River south of which the Santa Ynez Mountains continue to rise. Along the More Ranch Fault, which runs just inland of the Goleta shore, the coastal bluff continues to rise while the sagging basins on the north side of the fault give us the continuous linear arrangement of wetlands of Devereux Creek, Devereux Slough, Goleta Slough, and lower Atascadero Creek.

Innumerable smaller faults (some yet uncharted) reflect or deflect the larger geological forces. These smaller faults, and especially the junctions of intersecting fault lines, have immense significance for plant and animal communities. Long after the rainy season has ended, these cracks through surface layers receive slow-moving water perched on or stored beneath impermeable soil layers. On San Marcos Foothills that impermeable layer is mostly bentonite clay (Parsons, 1998). These soil layers suspend a lens of water much of which eventually passes laterally to the cracks, small faults, or other kinds of twists and turns of the underlying strata. Where creek banks and channels intersect, these sub-surface waters flow and wetlands occur.

Beneath the clay lies groundwater, water that has managed to pass to greater depths. Along Cieneguitas Creek, four borings taken on October 1997 showed groundwater at 10’, 15’, 16’ and 16’ depths (CFS Engineering, 1997). Creeks and other low-lying terrain allow the surface expression of groundwater also. Where wetlands are persistent or lingering, as they are on San Marcos Foothills, animal and plant communities may flourish year-round. These are some of the underlying processes that give rise to wetlands and support biotic communities.

East of Atascadero Creek, old marine and terrestrial sediments appear in the subsurface, as is typical of the foothills underlying the coast of the Santa Barbara Channel (Parsons, 1998). Sedimentary rock includes Rincon Shale, important because of the function its base clay layer plays in creating seeps and springs, typically marked by relatively fertile soil. On SMF three cultural sites are located near Rincon Shale mudstone. Sespe Formation, colorful sediment from both terrestrial alluvial plain

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