Geology
Geologically the mountains are young, and with the exception of a few volcanic rocks in the extreme western part of the range, and a small exposure of the metamorphic Franciscan Formation north of Carpinteria, exclusively of sedimentary origin. They were uplifted in the late Miocene Epoch, about five million years ago, along the Santa Ynez Fault, a feature which is considered to be active. Being young, the slopes are steep and the topography is extremely rugged; the gradient is highest on the northern side, above the trace of the fault. Dramatic sandstone formations, including outcrops of the resistant Coldwater and Matilija formations, are visible at many locations in the range.
Read more about this topic: Santa Ynez Mountains