San Jose Hills

The San Jose Hills are a part of the Transverse Ranges located in Eastern Los Angeles County, California, marking the border between the San Gabriel Valley and the Pomona Valley. It includes portions of Covina, West Covina, Walnut, Pomona, and San Dimas. To the south, the valley of San Jose Creek (a line followed by the Pomona Freeway) separates the San Jose Hills from the Puente Hills and Chino Hills.GeologyThe San Jose Hills are part of the geologic history of Southern California. The San Gabriel Mountains (the Transverse ranges located north of the San Jose Hills) were uplifted by tectonic force as a result of the colliding Pacific and North American plates more than a billion years ago. This tectonic pressure created a deeply fractured and fissured sheets of rock that began to shift direction about 25 million years ago. Gradually, a portion of this fissured rock began to uplift from the ocean forming the Los Angeles Basin. Further folding and fissures helped form other uplifts that include both the San Jose Hills and Puente Hills. These hills, prone to erosion, were formed their domed appearance while still submerged under water. The San Jose Hills Fault has the possible magnitude of 6.0 to 6.5 and last was active in 1990.