San Andreas Fault at Wallace Creek

We drove to the Carrizo Plain to see the wildflower bloom, so an opportunity to see visible effects of the San Andreas fault was an unexpected bonus. The 1906 San Francisco earthquake on the San Andreas fault led to fires that burned much of San Francisco.

According to a geology tour brochure from the Carrizo Plain National Monument, the San Andreas fault is about 700 miles long, and it’s “the boundary between the Pacific and North American tectonic plates.” The land on each side of the fault has slipped sideways as the tectonic plates moved, and you can see this at Carrizo Plain.

In the above aerial view from Google Earth, the red arrow points to where Wallace Creek crosses the San Andreas fault. The diagonal line running parallel to the Temblor Range is the San Andreas fault. From wikipedia, temblor is “from the Spanish word for ‘earthquake’ (terremoto)”.

Shown below, Wallace Creek makes a zigzag at the San Andreas fault. About 3,800 years ago, Wallace Creek flowed straight across the fault, but since then the creek’s path has been displaced 420 feet at the San Andreas fault. During an earthquake in 1857, the land moved 30 feet (9 m).

Wallace Creek offset by 420 feet as it crosses the San Andreas fault

We hiked up the creek to see wildflowers in the Temblor Range. Click on any photo to enlarge it.

Closer to the parking lot, fiddleheads were less dense here than at the overlook, allowing a photo with fiddleheads in and out of focus, standing out from the background. I think it’s a common fiddleneck, a California native plant.

common fiddleneck, amsinckia intermedia

Living in the San Francisco Bay Area, the San Andreas fault is several miles from our home. It shaped a nearby mountain. Seeing the San Andreas fault 200 miles south of us helps us appreciate the enormous forces of nature. A geology tour brochure says “large earthquakes … happen once every few
hundred years”. Well, it’s been 111 years since the last Big One…


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I enjoy travel, art, food, photography, nature, California native plants, history, and yoga. I am a retired software engineer. The gravatar is a Nuttall's woodpecker that visited our backyard.

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