Sunday, July 19, 2009

Finding fault with a new friend

Every once in a while, I get to meet somebody that I know from working on wiki projects. In a wiki, even a dozen contributors may be spread out all over the world. Sometimes they come to me during the course of a visit to California. Sometimes I go traveling and look up someone lives nearby.

This weekend's visitor, from Germany, asked whether he could see the San Andreas Fault. Despite having lived most of my life nearly on top of it, I could not identify it. I guess I just didn't think there was too much to see. So this time, instead of just showing my guest around the public library, we spent some time there. We asked the librarians to get some materials out of one of the locked cases (apparently a rare request; it took two of them to find the right key). Then we reviewed the different publications. Two of them were short booklets describing fault field trips north and south of San Fransisco. We photocopied various parts of these before returning them to the locked cases.

We drove up to Point Reyes yesterday, where they have an "earthquake trail" set up. Besides some rather pleasant grassland and a sequence of signs, the short, paved trail passes a segment of fence that crosses the fault and is split in two across it. The two halves are 16 feet apart, showing the distance the fault moved during the 1906 earthquake. We took photos of this fence and hiked around the area a bit, but that was not the most interesting part of the trip.

Because we knew what to look for, we drove up onto one of the vista points that dot northbound highway 280 and looked north toward Crystal Springs Reservoir and San Andreas lakes. (See here for the view from Google). The San Andreas runs under these bodies of water, in a nearly straight line.

Further north, the Point Reyes peninsula is west of the San Andreas. Here again, the water follows a nearly straight line that separates one tectonic plate from the next. Look at this link and follow the line of Highway 1 and the water from Stinson Beach to Dillon Beach. We drove along this road yesterday, too.

We also took a side trip on the way north to a lesser-known point of interest, the Bay Model in Sausalito, just north of the Golden Gate Bridge. In the days before computer modeling, it was used to evaluate the effects of possible projects in the bay, such as dredging ship channels and even one plan to dam part of the bay to create a freshwater reservoir. We enjoyed a picnic lunch looking out on one of the marinas and across the bay.

If he had never asked the question, I would never have looked up any of that information, nor made the trip.