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Sonoma Mountain is a prominent landform within the Sonoma Mountains of southern Sonoma County, California.〔''Sonoma Mountain Study, a Specific Plan'', Sonoma County Community and Environmental Services, February, 1978〕 At elevation of ,〔 Sonoma Mountain offers expansive views of the Pacific Ocean to the west and the Sonoma Valley to the east. In fact, the viticultural area extends in isolated patches up the eastern slopes of Sonoma Mountain to almost in elevation. The eastern and northern slopes are protected from afternoon heat and hence are more densely forested in oak woodlands, abetted by the well drained nutrient rich soils. The western and southern slopes, on the other hand, are drier and warmer, leading to fewer dense woodlands and more chaparral, grassland and oak savannah. ==Geology== Up until about twelve million years ago, this location was part of the seabed of the Pacific Ocean. In the Miocene era, precipitated by the combination of tectonic movement due to the seismically active environment and the presence of magma not far below the Earth's surface, a massive period of uplift ensued. This uplift formed the volcanically based Sonoma Mountains as well as the Mayacamas Mountains to the east. Residual evidence of these ancient geological features appears in the form of local hot springs such as nearby Mortons Hot Springs and Agua Caliente Hot Springs. The presence of the active Rodgers Creek Fault also attests to this prehistoric tectonic movement. The eastern slopes of Sonoma Mountain drain to Sonoma Creek, the northern flanks drain to Matanzas Creek and the southwestern flanks are in the Petaluma River watershed. The most readily accessed eastern slopes have a predominant occurrence of Goulding clay loam soils, particularly in the immediate area of Graham Creek.〔''Soil Survey, Sonoma County, California'', U.S. Department of Agriculture, Soil Conservation Service, Government Printing Office, Washington DC, May 1972〕 These are generally areas of 15 to 30 percent slopes that support dense mixed oak woodland, with large percentages of California laurel and Bigleaf maple. Higher on the eastern slopes is a large occurrence of Goulding clay loam on 30 to 50 percent slope, still with a dense forest cover, but with more Pacific Madrone and Coast live oak. Soil depths are rarely over a few feet deep before bedrock is reached, but even thin soils support rich plant growth because of the high nutrient content and mild climate. The peak and higher northern slope of Sonoma Mountain consists of soils of the Goulding cobbly loam association, which are five to fifteen percent in slope and may contain up to 20 percent of cobblestones at the near surface. Outcrops of basaltic rock are common among this soil type, betraying the volcanic origin of Sonoma Mountain. The upper western reaches of Sonoma Mountain have some amounts of the Raynor clay association, which group typically has a depth to bedrock of about four to five feet. Lower on the western exposures, along the Lichau Creek immediate drainage area, there is a broad occurrence of Goulding clay loam on slopes of about 15 to 25 percent. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Sonoma Mountain」の詳細全文を読む スポンサード リンク
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