Topanga Canyon State Park where we will visit the chaparral is located in the transverse mountain range of Southern California.The transverse ranges are very unusual in that they run east to west. From east to west the transverse range includes the San Bernadino mountains, the San Gabriel mountains and the Santa Monica Mountains. The orientation of the transverse range was created as the Pacific Plate slowly rotated counterclockwise. This rotation not only created the numerous faults and earthquakes for which the area is famous, but it also created the transverse ranges themselves. These mountains are fault block mountains formed during periods of subduction. A dip-slip motion has resulted in the uplift of these mountains. Most of this uplift has taken place in the last 2 million years.
The transverse mountains lie on the "big bend" of the San Andreas fault. The active faults of the Los Angeles basin lie beneath the thick layer of alluvium that has built up over millions of years from the floodwaters of the Los Angeles, San Gabriel and Santa Ana rivers. In the Santa Monica Mountains near Topanga you can see many examples of the geologic history of this area.
The transverse and Peninsular Ranges tower around the Los Angeles floodbasin, which is only slightly above sea level. Some of the higher peaks are Mt. baldy in the San Gabriels at 3068 m, Mt. San Jacinto in the Peninsular mountains and the highest mountain in Southern California, Mt. Greyback in the San Bernadino mountains at 3506 m.
Fragile Habitats of Southern California is a part of LAEP
Learning Exchange.