Marsha Beatty
Salt Lake City
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| Map of the San Andreas system. USGS |
Marsha,
The San Andreas fault is visible in many places. You might want to get a copy of this book to serve as your guide: Field Guide to the San Andreas Fault (Caveat: I haven't read it, and don't know the author.)
The San Andreas is the boundary between the North America and Pacific plates. The fault extends from the Gulf of California (Sea of Cortez) northwest for 810 miles across California, from the Salton Sea trough to north of San Francisco, entering the sea south of Fort Bragg. The fault is far longer than that, as it continues into the Pacific Ocean, where it separates the Pacific Plate from the Juan de Fuca Plate.
The fault runs right through Carrizo Plain National Monument, established in 2001 to highlight the geology. The USGS has an online field guide to San Andreas features there. The National Monument is located about 160 miles north of Los Angeles, 260 miles south of San Francisco, about 55 miles west of Bakersfield, and and 50 miles north of Santa Barbara. The San Andreas is a 'right lateral fault'. That means that if you are standing on one side looking
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| Famous sign just south of Parkfield, California. |
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| The Pacific Plate is the rock on the right. North America is the tan rock above the car. Photo by David Lynch. |
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| The patch on this road repairs damage from motion along the fault, and has to be periodically replaced. |
Try this website to visit some features in the Hollister- Pinnacles National Monument area; here and here.
This blog has photos of features along the San Andreas in the LA area.
This website is a field guide to the famous Wallace Creek site on the Carrizo Plain, probably the best-known feature on the San Andreas.
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| Wallace Creek--- This view of the Wallace Creek on the Carrizo Plain is perhaps the most famous feature on the San Andreas Fault. As the stream continues to progressively erode into its channel, right-lateral motion along the San Andreas Fault has moved the downstream portion of the channel northward (towards the viewer). Sediments cut by Wallace Creek were radiocarbon dated at about 3,700 years old, and the stream channel has been offset about 430 feet since then. USGS. |
When in California we went to Parkfield (pop. about 20) to 'see' the 'fault'. This is a great place to view the effects and learn the history since white men first settled there. On the road in from the south (paved) you cross the fault; it runs along the road and crosses it near the power line and you can see the road patches it has required. Nearer town the road crosses the fault on a bridge which is specially constructed to be able to 'slide' when tremors hit (usually a couple of small ones every week or so). In fact we saw a curve in the bridge from the last larger one. In town are 2 granite rocks set apart to show how far the earth has moved since the area was first settled. And of course a water tower with the sign "be here when it happens" and "buy land here and own beach front property in 2 million years". A fun place and I'm sure if you stay there a few days, or or just plain lucky, you may feel a small quake on your visit. Lawrence Spencer
ReplyDeleteVisit deRose Winery on Cienega Road, south of Hollister, CA. Located in a former Almaden winery facility. The fault runs directly under the building, and has cracked the concrete floor and caused walls to off-set. You can stand with one foot on the Pacific Plate and one foot on the Continental plate.
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