(Station 1.) To the south, in the far left distance, is Mount Umunhum with its abandoned cold-war radar tower sticking up on the left. Behind it to its right, you can barely see the tip of Loma Prieta 23 miles away, under which was the epicenter of the huge 1989 quake. Beneath our feet are rocks from Loma Prieta, as we're standing on a different plate from the peak.

The Los Trancos Open Space Preserve includes a 1.5-mile trail that shows short-term and long-term effects of two tectonic plates sliding past each other--the Pacific Plate and the American plate sliding along the San Andreas fault. Dad and I went exploring. If you want to follow along with the trail guide, download it in PDF .

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elf1 > (Station 1.) To the south, in the far left distance, is Mount Umunhum with its abandoned cold-war radar tower sticking up on the left. Behind it to its right, you can barely see the tip of Loma Prieta 23 miles away, under which was the epicenter of the huge 1989 quake. Beneath our feet are rocks from Loma Prieta, as we're standing on a different plate from the peak.

elf1 > Atop our vantage point, looking northeast towards Dad and the San Francisco bay, I'm surrounded by shoulder-high shrubbery.

elf1 > Here it is up close. Pretty. Don't know what it is. Mom would know, but she's not along.

elf1 > (Station 1 still.) Looking east from our viewpoint, there's a depression like a gully between us and the next hillside. That's where the fault runs.

elf1 > (Station 2.) Looking mostly north, in the distance to the left (above the big V formed by the trees/shrubs) you can just see a couple of reservoirs in a depression between two ranges of hills. 19th-century engineers didn't realize that they were building dams to hold that water right on top of a major fault: The San Andreas.

elf1 > Some ferns along the path, fading for the winter. This is not the fault's fault.

elf1 > (Station 3.) Much of the trail runs along a "bench", which is a wide flat area that looks completely like an old logging road that has grown over. As the earth pulls apart, sediment settles into the cracks left on the surface, eventually forming a wide, road-like "bench."

elf1 > (Station 4.) In the 1906 San Francisco quake, the two plates moved about 25 feet apart north of the Golden Gate. In this area, they moved only about 3-4 feet apart. This reconstructed/renovated old fence shows what it would have looked like immediately after the quake.

(Station 1.) To the south, in the far left distance, is Mount Umunhum with its abandoned cold-war radar tower sticking up on the left. Behind it to its right, you can barely see the tip of Loma Prieta 23 miles away, under which was the epicenter of the huge 1989 quake. Beneath our feet are rocks from Loma Prieta, as we're standing on a different plate from the peak.