Physiographically, they are a section of the larger Pacific Border province, which in turn are part of the larger Pacific Mountain System physiographic division. UNESCO has included the "California Coast Ranges Biosphere Reserve" in its Man and the Biosphere Programme of World Network of Biosphere Reserves since 1983.
The northern end of the California Coast Ranges overlap the southern end of the Klamath Mountains for approximately 80 miles on the west. They extend southward for more than 600 miles to where the coastline turns eastward along the Santa Barbara Channel, around the area of Point Conception. Here the southern end meets the Los Angeles Transverse Ranges, or Sierras de los Angeles. The rocks themselves that comprise the mountains are of a great variety and widely varying geologic ages. Most of the rocks were formed during the Tertiary, Cretaceous and Jurassic periods. Most were deposited on the sea bottom as sediments, but in many places also had the cracks, crevices and other gaps infused with molten lava or other masses of igneous rock, which were forced in molten condition into the sedimentary rocks. All of the range has been folded and faulted during several periods, with erosion of the softer rock giving much of the current appearance.
The California Ranges had a high production of mercury following the discovery of gold in the Sierra Nevada. In the Cache Creek Basin, Cenozoic cinnabar deposits near Clear Lake are the northernmost of a group of similar deposits associated with volcanism and migration of a transform fault system. During 1877, these deposits hit their peak production of mercury, producing approximately 2,776 metric tons. These abandoned mines are still a source of mine waste runoff in Cache Creek and other downstream bodies of water.
The Northern Coast Ranges are a section of the California Coast Ranges. They run parallel to the Pacific Coast from the North San Francisco Bay Area to coastal Del Norte County. The Klamath Mountains, including the Siskiyou Mountains sub-range, lie to the north and northeast. The Southern Coast Ranges lie to the south.
The Northern Coast Ranges run north-south parallel to the coast. Component ranges within the Northern Coast Ranges include the Mendocino Range of western Mendocino County and the Mayacamas, Sonoma, and Vaca Mountains and the Marin Hills of the North Bay.