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Fig 1 - Ecological history

Fig 1. Geologic regions of California. As the old sea floor surface of the Pacific was scraped off, it accreted to North America’s western margin and formed the most important basic rocks of the Coast Ranges, the sandstones, shales, and cherts of the Franciscan formation. Ultra basic rocks from deeper ocean bottom were forced upwards by the subduction of the Pacific Plate beneath the North American Plate, through the Franciscan sedimentary layers to form serpentine soils with their often unique floras. Continued action of the two plates still distorts and elevates the coastal mountains which form the western edge of the Central Valley. The Central Valley began filling with sediments, now thousands of meters deep, in the Cretaceous period about 80 million years ago. Originally an inland sea, it filled with enough sediment to become mostly dry land by 1.5 million years ago. The Great Valley Sea persisted longer in the San Joaquin Valley than the Sacramento Valley (Harden 2004). Already a low mountain range formed as a result of the subduction of the Pacific Plate, the Sierra Nevada tilted and became several thousand meters higher in the Pliocene period. This uplift, beginning about 5 million years ago, had major effects on the regional environment. Also important, and relatively recent, was the beginning of movement of the San Andreas Fault, which in 15 million years moved granites from the southern Sierra Nevada to their present locations 500 km farther north, as far as San Francisco. Geologic processes at a continental scale continue, but within the past 150,000 years, global climatic events have modified the basic geologic structure and associated landscapes in ways which modify the slower processes of plate tectonics. Important have been the changes in sea level associated with ice ages, which, with uplift of coastal lands, has produced distinctive coastal terrace landscapes. The most recent major glacial retreat began about 14,000 years ago, ending the Tioga glacial period in the Sierra (Phillips et al. 1996), which generally corresponds with the late Wisconsin in North America and the Wurm in the Alps (Wood 1975). As glaciers melted, the rising sea level drowned the mouth of the Sacramento River to form San Francisco Bay. Because so much of California's Mediterranean landscape rests on the unstable sedimentary rocks of the Franciscan formation, mass movement of soil is common. These movements are an integral feature of the landscape, which typically exhibits multiple landslides of varied ages but associated with intense rainfall events (Smith and Hart 1982). Removal of woody vegetation often leads to disastrous mass movement (Heady and Pitt 1979; Gabet and Dunne 2002). Norris and Webb (1976) claim that slides on Franciscan substrate transport more material in the North Coast ranges than streams. 
Geologic regions of California. As the old sea floor surface of the Pacific was scraped off, it accreted to North America’s western margin and formed the most important basic rocks of the Coast Ranges, the sandstones, shales, and cherts of the Franciscan formation. Ultra basic rocks from deeper ocean bottom were forced upwards by the subduction of the Pacific Plate beneath the North American Plate, through the Franciscan sedimentary layers to form serpentine soils with their often unique floras. Continued action of the two plates still distorts and elevates the coastal mountains which form the western edge of the Central Valley. The Central Valley began filling with sediments, now thousands of meters deep, in the Cretaceous period about 80 million years ago. Originally an inland sea, it filled with enough sediment to become mostly dry land by 1.5 million years ago. The Great Valley Sea persisted longer in the San Joaquin Valley than the Sacramento Valley (Harden 2004). Already a low mountain range formed as a result of the subduction of the Pacific Plate, the Sierra Nevada tilted and became several thousand meters higher in the Pliocene period. This uplift, beginning about 5 million years ago, had major effects on the regional environment. Also important, and relatively recent, was the beginning of movement of the San Andreas Fault, which in 15 million years moved granites from the southern Sierra Nevada to their present locations 500 km farther north, as far as San Francisco. Geologic processes at a continental scale continue, but within the past 150,000 years, global climatic events have modified the basic geologic structure and associated landscapes in ways which modify the slower processes of plate tectonics. Important have been the changes in sea level associated with ice ages, which, with uplift of coastal lands, has produced distinctive coastal terrace landscapes. The most recent major glacial retreat began about 14,000 years ago, ending the Tioga glacial period in the Sierra (Phillips et al. 1996), which generally corresponds with the late Wisconsin in North America and the Wurm in the Alps (Wood 1975). As glaciers melted, the rising sea level drowned the mouth of the Sacramento River to form San Francisco Bay. Because so much of California's Mediterranean landscape rests on the unstable sedimentary rocks of the Franciscan formation, mass movement of soil is common. These movements are an integral feature of the landscape, which typically exhibits multiple landslides of varied ages but associated with intense rainfall events (Smith and Hart 1982). Removal of woody vegetation often leads to disastrous mass movement (Heady and Pitt 1979; Gabet and Dunne 2002). Norris and Webb (1976) claim that slides on Franciscan substrate transport more material in the North Coast ranges than streams. 
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