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 from Parkfield to the Salton Sea. Photos are arranged North to South.
A sag pond is an area between two parallel faults that has dropped, or sagged, down creating a depression that can fill with water. These areas can also form marshes. Other examples of “sag ponds” include San Andreas Lake (the fault’s namesake) near San Francisco, Lost Lake in the Cajon Pass, and Jackson Lake near Big Pines.
Sag Pond visible in the distance just north of Hwy 33. Distant mountains are Mt Pinos and the San Emigdio Mountains.
A small sag pond is visible at the end of this valley, known as Cuddy Valley, near Frazier Park.
Marshy area along main trace of the fault at Barrel Springs. Snow capped San Gabriel Mountain can be seen in the distance.
Jackson Lake in the San Gabriel Mountains along Big Pines Highway
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 of Gorman from the late 1950’s. Taken from the southern end of town.
Looking easterly along the fault zone near Neenach from the Ridge Route
Looking westerly along the fault zone from Big Pines Highway toward Devils Punchbowl (obscured by smoke).
Lone Pine Canyon from the summit near Wrightwood. The San Andreas Fault runs to the left side of the canyon. A pressure ridge is visible as a light colored hill near the center of the photo above the trees.
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.
Fault scarp in the Carrizo Plain. This marks the line of movement from the 1857 event.
State Highway 58 crossing the San Andreas Fault in the Carrizo Plain.
Scarps and offset streams visible on the Carrizo Plain Road south of the Carrizo Plain.
Good example of a fault scarp, offset stream, and springs at the summit of Tejon Pass.
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.
Same area shown today, notice the line of trees along the roadway, marking the sag areas along the fault. Looking easterly.
Scarp visible along Pine Canyon Road (County Road N2). The scarp at the point where the trees visible in the distance transition to chaparral.
Scarp visible just beyond aqueduct near Palmdale.
Fault scarp is visible as the abrupt rise in the background. This is along the 1857 rupture at the State 14 Freeway.
1999 aerial photo showing the San Andreas Fault crossing State 14 at Ave S in Palmdale. The scarp passes through the upper ramps to State 14. at an angle
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.
Wallace Creek in the Carrizo Plain. This stream is a classic example of how a stream course gets offset by repeated movements.
Additional Features
In Parkfield, the fault is marked in a most amusing way. The bridge here has also been slowly shifted by fault movement since it was built in the 1930’s.
The Fault marked just like a political boundary.
Bridge over the creek south of Parkfield. The slight bend to the right has been created by fault movement.
While the section of the San Andreas Fault through the Palmdale area is “locked”, some cracking has occurred along roadways, culverts, and parking lots that cover the fault line. At the Ave S / State 14 Park and Ride lot, some en echelon fractures have been noted. Pavement here is only a few years old.
Closer view of the fractures. While not conclusive, I do believe these to be from the fault.
En echelon fractures within the parking area at Ave S.
Fractured and slightly offset culvert at the San Andreas Fault scarp at Ave S.
Alquist-Priolo buffer zone along the San Andreas Fault at Church St in Highland, CA.
San Andreas Fault (Mission Creek Segment) near Indio, CA. Palm trees mark where springs have been formed along the fault line.
