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Visible Fault Features along the
San Andreas Rift Zone in the Los Angeles Vicinity

The San Andreas Fault Zone is a major structural and physiographic feature in California. Many features of the movement can be seen either on a geologic map or out in the field. In this page, I will show many of these features that are visible along the segment of the San Andreas Fault that passes closest to the cities of Santa Clarita and Palmdale. Photos and perhaps maps will follow in the coming weeks.

Sag Ponds:
A sag pond is an area between two parallel fault zones that has dropped, or sagged, down creating a depression that can fill with water. Other examples of "sag ponds" : San Andreas Lake near San Francisco, Lost Lake in the Cajon Pass, and Jackson Lake near Big Pines.

A small sag pond is visible at the end of this valley, known as Cuddy Valley.

Marshy area along main trace of the fault at Barrel Springs. Snow capped San Gabriel Mountain can be seen in the distance.

Fault-Controlled Valleys:
Valley formed as a result of two parallel fault lines lifting mountains or ridges alongside a dropped down area, or the result of thousands of years of erosion in a fault zone. Rock within fault zones has been weakened and is therefore easier to erode. These valleys can be quite large, as evidenced by the Owens Valley in eastern California, or similar in appearance to Leona Valley near the Antelope Valley in the Mojave Desert.

View easterly of part of Cuddy Valley. A fault scarp is visible on the right side of the valley.

Postcard view of part of the San Andreas Rift Zone. This location is just east of the town of Gorman. Interstate 5 is to the left and Gorman Post Road (Old Ridge Route) is on the right. 

Fault Scarps:
Fault scarps can be formed through the surface manifestation of movement that occurred underground along a fault during major earthquakes or continued movement along a specific fault zone over a large period of time.

Scarp visible along Pine Canyon Road (County Road N2). The scarp at the point where the trees visible in the distance transition to chaparral.

This postcard of the old Ridge Route in Peace Valley shows not only a great example of a fault scarp, but also shows a sag pond adjacent to the scarp. The large mountain visible in the distance is Frazier Mountain. The fault runs through the valley visible on the right side of the mountain.

Good example of a fault scarp, offset stream, and springs at the summit of Tejon Pass.

Same area shown today, notice the line of trees along the roadway, marking the sag areas along the fault. Looking easterly.

Fault Gouge:
Rock that has been ground to a fine powder or clay along faults is known as "fault gouge". These zones of fault gouge can be as wide as 25 feet or as narrow as one inch. With continued movement, solid Granite can be turned into clay as evidenced in many places along the San Andreas Fault Zone.

Large zone of fault gouge in road cut at the summit of Tejon Pass on Interstate 5. The gouge is visible as a light colored band within the cut.

Close-up of fault gouge along Pine Canyon Road (County Road N2).

Offset Streams:
Movement along a fault can offset drainage features. Many offset streams are visible in the Carrizo Plain segment of the San Andreas Fault. The best example of offset is located at Wallace Creek, in the Carrizo Plain. There, two channels exist because of continued movement. Other smaller examples can be seen in Leona Valley, and along Fort Tejon Road above Littlerock and Pearblossom.