The Fault is Not in Our Stars

January 7, 2021

I had to get out of the house to escape my laptop and my doomscrolling the news about the attack on the Capitol yesterday. What better way to counteract the doom and gloom than by doing something safe and soothing like riding along the San Andreas Fault. The fault, dear Brutus, is not in our stars but in our rocks.

You may have heard that California is what is called "geologically active." That's because two tectonic plates, the Pacific and the North American, are grinding against each other along the western part of the state at the San Andreas Fault. The San Andreas is probably the most famous fault in the world (at least to Californians), but of course there are many other active faults. For example, offshore from northern California to Vancouver Island is the Cascadia subduction zone, which might be the site of the next Really Big Quake. Kathryn Schulz won the Pulitzer Prize for her 2015 New Yorker article about it.

Geologists say that the San Andreas is really a fault system, with lots of other faults splitting off or paralleling the main fault. Two of the more active ones are across the bay from me, the Calaveras and the Hayward. The Calaveras is a creeping fault, moving several millimeters every year. The nice wide level places for building schools and libraries and city halls turned out to be right on the faults. That creep is hell on plumbing and curbs and buildings. When either of those decide to really move it will cause a lot of damage.

The main course of the San Andreas is easily seen if you use the Terrain layer on the route map.

Something else special about this ride is that I loaded up Pokey in the car and drove somewhere else - I didn't start from home. It's been a few months since I did that.

The first leg was on Cañada Road, a really nice road that goes past old estates and the Pulgas Water Temple, where the Hetch Hetchy Aqueduct finishes its travels from Yosemite. Then we crossed some hairy freeway on/off ramps to get to the next section, the Sawyer Camp Trail, which runs along the shore of a couple of reservoirs that sit right on the fault. After that I crossed over the top of the hill to see glimpses of San Francisco Bay, eventually looping back to Cañada Road.

Note: There's a straight line on the northwest end of the track due to forgetting to turn on the tracking app again after a break. I really did stay on the trail and did not bushwhack.

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Cañada Road is a lovely ride. It starts out in the horsey town of Woodside and goes north to Hwy 92, the route between the bay the the ocean. The northern half of it, the part I rode, used to be closed on Sundays to vehicular traffic but I think that's been suspended for the time being. It's got a few long rollers and slow curves to give interest. The last couple of miles are above Upper Crystal Springs Reservoir so the scenery is wonderful.

This area was where many San Francisco rich people had estates in the late 1800s and continues to this day, where they could escape the cold SF summers and have a bit more elbow room - you know, a thousand acres or so. One was the Bourn family and their estate Filoli, which is a word coined from their motto, Fight-Love-Live. Mr. Bourn made his wealth through the Empire gold mine in the Sierra. The second family to own the estate was Lurline Matson Roth and her husband. She was a member of the Matson shipping family. She donated the estate to the National Trust for Historic Preservation after her husband's death. Both the Empire mine and the Matson Line are big parts of California economic history.

However, the main claim to fame these days is the house's connection to the old prime time soap opera Dynasty. The exterior shots of the family home in the opening credits are those of Filoli.

Something I learned later is that the main fault runs directly under the mansion and gardens. Huh.

We did not go to Filoli today although spending a day there exploring the fabulous gardens might be a good covid activity soon.

Entrance to the Filoli estate. The house and grounds are amazing in that bygone-times way. And we're actually looking across the San Andreas Fault. Runs right under the trees out there.

My usual pitstop along Cañada Road was closed. That's the Pulgas Water Temple, an edifice that glorifies the end of the travels of the water transported along the Hetch Hetchy Aqueduct from the Hetch Hetchy Reservoir in Yosemite to the people of San Francisco. I also use Hetch Hetchy water every day. The grounds are nice and lots of weddings are held here. Not right now though.

The Pulgas Water Temple. Not today - closed for the duration.

Another estate along Cañada Road - the Acme Estate.

At Upper Crystal Springs Reservoir and nearing the end of Cañada Road at its intersection with Hwy 92. Hello Pacific Plate from the North American Plate.

The northern end of Cañada Road is where many cyclists park to before starting one of several good loops you can do in this area, with all the hill climbing you could want. The views open up and you have a good look at the Pacific Plate from the North American Plate.

After a rather hairy negotiation of on- and off-ramps where Hwy 92 becomes a freeway (don't think I need to do that again) I got to a newish bike path above Lower Crystal Springs Reservoir that takes you off a road with no shoulders. The path meanders along the contour line above the lake and best of all had the toilet I wish was available back at the water temple. Phew.

Despite the cracks, this is a newish bike path that gets you off a shoulderless road.

Since I started this ride I've been on right-of-ways through lands controlled by the City and County of San Francisco's water department. They allowed San Mateo County to make the old road into a bike/ped path but no getting near the water.

The dam that created the Crystal Springs reservoirs was redone a few years ago. Thankfully they incorporated more infrastructure for bikes and pedestrians. Nice views from there.

A lovely new dam across San Mateo Creek.

Turning around we see Interstate 280 looming above the canyon where San Mateo Creek exits the reservoir.

I had some trouble negotiating the transition from the dam to the Sawyer Camp Trail because the dam parking area was jammed with ranger trucks and cop cars. Turns out there was a missing person search going on.

Lifted from the San Mateo County Parks site: "Sawyer Camp Trail, later called San Andreas Valley Road, or simply Valley Road, was once the main highway between San Francisco and Half Moon Bay [on the coast]. Wagons pulled by teams of horses hauled wood over the road. Much of the old road was flooded by Crystal Springs Reservoir by 1888.

"When the city of San Francisco took over the watershed lands, narrow, winding Sawyer Camp Trail was then a county road. The Water Department fenced it for the protection of San Francisco's drinking water. In 1978, the San Mateo County Board of Supervisors designated the road a non-vehicular recreation trail and paved it for bicycles with funds provided by the State Department of Parks and Recreation."

Looking south soon after getting on the Sawyer Camp Trail. The dam I just rode over is in the background.

The geology around here is pretty interesting. I took exactly one geology class - which I found a thousand times more interesting than I thought I would - so if anyone else knows more please feel free to correct. One thing I remember is that the rocks around here are known as the Franciscan Complex. It used to be called the Franciscan Melange which I kind of prefer. Those rocks were formed before the San Andreas was created, when the no-longer-existing Farallon Plate subducted under the North American Plate, scraping off all these rocks onto this margin of the North American Plate. From what I gather there are a few different ways the melange shows up. You can explore more photos at the Wikipedia page.

Some Franciscan melange. Or Franciscan complex. Or Franciscan Assemblage. Or maybe not.

The Sawyer Camp Trail goes in and out of trees and grasslands.

Halfway along is a tree called the Jepson Laurel. It's more than 600 years old, and is named after one of the early California botanists. There's a picnic area, a loo, and an archaeological artifact near the tree.

Can't quite remember what this is but it does ring a bell ...

Here's the Jepson Laurel. More than 600 years old and not looking so good any more. All the undergrowth is poison oak, so even though the laurel is fenced off there is little chance anyone would try to climb in there to bother it.

Once we leave the Jepson Laurel the trail climbs until we reach the dam that created the San Andreas Lake in 1868. The lake flooded the San Andreas Valley where various Spanish explorers camped now and again. The fault was named after the valley by geologist Andrew Lawson in 1895 (although many people think he named it after the lake).

This dam, which looks to be mostly earthen, survived two major quakes since it was built - in 1906 and in 1989 - plus many minor ones. I couldn't find any info about it being significantly damaged in either of those big quakes.

We leave the Crystal Springs lakes and head on up to San Andreas Lake through oaks and bay laurels.

The San Andreas Dam. The little brown dots in the center left are deer.

The San Andreas is what they call a strike-slip fault. The Pacific Plate is moving northwest relative to the North American Plate.

Looking out beyond the plaque shown above. The main fault goes under my feet and out beneath the small peninsula on the center right. It all looks so peaceful, doesn't it? But think about all the enormous pressures at work below. Can't help wondering when this is going to move again.

The trail keeps climbing up above the lake until we reach aptly named Skyline Boulevard. At the end of the trail is another plaque to commemorate Portola and his merry band who wandered around here and "discovered" San Francisco Bay.

The plaque reads: First Camp after Discovery [sic] of San Francisco BayOn Nov 4 1769 the expedition of Captain Gaspar de Portola, after crossing Sweeney Ridge, beheld the bay of San Francisco for the first time. That night they camped at a small lagoon, now covered by San Andreas Lake. Finding the bay too large to go around and thinking they had bypassed Monterey Bay, the expedition camped here again on Nov 12 1769 on their return to San Diego.

This discovery thing is interesting. Sir Francis Drake sailed along the California coast in 1579, almost 200 years before Portola. He spent about six weeks somewhere near SF Bay to repair his ship but made no real mention of the bay or any exploration of it. Some say he was at what is now called Drake's Bay in Pt Reyes, outside SF Bay, and some think he was just inside the bay near Sausalito. Drake said he installed a plaque laying claim to Nova Albion for England but it's not been found. One possibility that might explain his missing the bay is the usual coastal fog that time of year. It can be pretty thick and it would be easy to miss the relatively narrow Golden Gate.

So, back to today, at the Portola plaque I left the Sawyer Camp Trail and crossed under the freeway to Skyline Boulevard. I made my own discovery of San Francisco Bay.

Just about to turn right onto Skyline Blvd when I discover San Francisco Bay.

A few streets later down Skyline I stopped to take this photo. The pointy thing in the distance is Mt Diablo. The dark thing jutting out into the water on this side of the bay is the runway for San Francisco Airport. What, we worry about sea level rise?

I'm on Skyline, with I-280 serenading me also.

The zip code I was riding through is highly desirable. But even to the point of building on the lot that abuts the power line? And the freeway across the street?

Still paralleling the freeway but we have more distance from it and a nice view of Crystal Springs Lake.

Back on the dam at Lower Crystal Springs Lake.

See that orange structure under the bridge? That's called the Flintstone House locally.

One of our local oddities is what has come to be called the Flintstone House. You can easily see it from the freeway. Read more about it and see better photos: Flintstone House.

After this I stayed on the main shoulderless road to head back to Cañada Road and the car, deciding not to go on the bike path that paralleled the road. That was a mistake sorta, since I forgot the path followed the contour and the road went up and over a nice hill. Ah well. Luckily traffic was light.

We'll go left, then turn off on to Cañada Road.

Back on Cañada Road. The overcast has cleared and the sun is out.

Just before I got back to the car, there is a formerly grand entrance to a former estate owned by the Phlegers (now part of the Golden Gate National Recreation Area). All the years I've been driving or riding by here I never stopped to explore the gate. Until today. Again, I blame you all for making me take a closer look at where I live. I looked in the window and saw there was a door on the other side. Then I saw you could walk behind the wall to see the door.

Always meant to check out this little window.

The car was just a few yards away. Loaded up Pokey and headed home.

I got these ramps to make loading Pokey a lot easier, especially after the added weight of the motor and battery. It wasn't hard to load her before, but I am really glad I have the ramps now. I ain't getting any younger.

Afterword: I'm posting this a couple of weeks after the fact. About three days ago we had a nice little 4.5 quake about 30 miles south of us right on the San Andreas Fault. It shook the house and rattled the windows well enough that I just started thinking I better get under cover, but then it stopped. I was shaken but I did not stir.

Today's ride: 26 miles (42 km)
Total: 114 miles (183 km)

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Mike AylingAnother interesting report, Kathleen.
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3 years ago

Suzanne GibsonI enjoyed your ride!
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3 years ago

marilyn swettI enjoyed reading all of historical information in your journal. The pictures were also great. Your trike sure looks like fun! I used to own a TerraTrike with fat tires that I would ride in the winter on snow and ice, but it was stolen last year.
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3 years ago

Kathleen JonesTo Mike AylingThanks, Mike. It was a nice ride.
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3 years ago

Kathleen JonesTo Suzanne GibsonThanks, Suzanne - me too!
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3 years ago

Kathleen JonesTo marilyn swettI remember reading about your trike being stolen out of your garage. What incredible nerve. I am still shaking my fist at those creeps.

Glad you enjoyed the journal.
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3 years ago

Gregory GarceauMy only fault is not knowing more about the San Andreas Fault. Thanks to this post, I no longer have that fault.

Great ride. And I'd love to see that Flintstone house. I have seen the Flintstones' Bedrock City campground in Custer, SD though. Freaky!
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3 years ago

Kathleen JonesTo Gregory GarceauIt's not your fault, so don't worry about it.

One of my favorite toys as a young kid was the Flintstones village I had. Plastic sheet with roads and houses marked out, plastic rock houses to put on them, and little dolls for all the characters. I think the Rubbles' house lasted into my teen years, still used by the youngest sibs.
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3 years ago