9.1: Introduction
As far as we can learn , John C. Fremont was the first to use the phrase ‘Coast Ranges’ for the mountains bordering the coast of California. Although mountains are practically continuous along the coast from Oregon to Southern California, yet, geographers have come to apply the term Coast Ranges much as Fremont used it, meaning that portion of the mountains bordering the Pacific Coast which lie between the Great Valley of California and the ocean.
The Coast Ranges are limited on the south by a line drawn westerly from the extreme southern end of the San Joaquin Valley, a line which closely accords with the northern boundary of Santa Barbara county. We find this marked topographically by the Cuyama Valley and the Santa Maria River, and further by the fact that to the south, the Transverse Ranges extend nearly east and west, while the Coast Ranges have a northwest and southeast direction.
The Coast Ranges do not constitute a simple mountain block like the main part of the Sierra Nevada. The folding of Earth's crust and the formation of fracture and earthquake lines in a general northwest and southeast direction have given origin to the series of parallel mountains and valleys. The disturbances of Earth's crust in this region have been many and severe, affecting different parts episodically.
At previous times, the Coast Ranges were submerged until nearly buried beneath the waters of the Pacific. They were then practically a group of islands and peninsulas separated from the Sierra Nevada by a broad, deep bay which occupied the Great Valley. Earthquakes and volcanic outbreaks, and changes in the level of the land seem never to have left the country at rest.
It was formerly believed that the Coast Ranges were newer than the Sierra Nevada and that the continent grew progressively westward from the Rocky Mountains. This is a mistake, for there was extensive land here long before there was any Sierra Nevada Range. The granite exposed in the Santa Lucia, Gavilan, and Santa Cruz Ranges, on the Farallon Islands and at Point Reyes, tells us there was land here long ago, and it was on this ancient land that the earliest known representatives of the Sequoia tree species flourished, as has already been mentioned.
The complexity of the geography of the Coast Ranges is increased by the fact that the underlying rocks vary greatly in their resistance to decay and erosion. Valleys may be formed where the rocks are soft, and peaks formed with more resistant rocks, as is illustrated in the case of the San Luis Buttes. These are the most striking mountain peaks, due to purely erosion effects. They represent ancient igneous eruptions that once emerged through the crust and now stand out because they are hard and the rocks around them are soft. They extend in a line from the town of San Luis Obispo northwesterly to the ocean and terminate in a great rock known as Morro Rock which rises bare and rugged to a height of nearly 600 feet.