Tuesday, March 31, 2009

Morgan Hill Temblor

Lest you need reminding that we live in a geologically active part of the world, well, after yesterday's shaker near the conjunction of the Hayward and Calaveras Faults you don't need reminding any more. I've often thought that it's no surprise that the theory of plate tectonics did not mature until after experience with the west coast of North America, in particular with the San Andreas and associated faults, because the fault geology here is so self-evident as to be insulting. Read with Brooklyn accent: "Hey stupid! I'm drifting over here!"

So, to sate the bloodlust of the tectonics gods before they punish us with further quakes, it's worth emphasizing some of the cooler geological features of the East Bay. If you think these are interesting then check out Oakland Geology and Berkeley's Walking The Fault.

1) There's a place in Hayward where you can actually see the displacement caused by the Hayward Fault as one side drifts north. The curb has moved noticeably over a few decades.

2) Sibley Volcanic preserve. Right up in our hills there's a dead volcano, with an old quarry exposing some of the rock. Plus it's damn purty. A few miles to the north, Lake Anza in Tilden is sitting in a dead caldera as well.

3) On Mt. Diablo, there's a cool little trail with interpretive signs heading up through the different geologic age-zones exposed on the mountain.

4) There is a wall that runs the length of the East Bay hills, from above Albany all the way down to Fremont. No one knows who built it, but there are theories ranging from boring early twentieth century rancher, to exciting but probably B.S. Aztec colony.

5) There was a train tunnel under the Oakland Hills that came out in the town of Canyon. (Never been back there? You should go.) The east entrance was buried by a landslide almost 3 decades ago. Does anyone know where the west entrance is/was?


  1. The west entrance was in Shepherd Canyon about a mile east of Montclair Village, as far as I can tell. According to a the websites below, the entrance is completely hidden and/or covered by now, and private homes have been built around where the tunnel entrance was, so it's hard to find any evidence of the tunnel anymore. See these train enthusiast sites for some photos and details about the location:




  2. Now that I've looked more carefully at the map, I realize that it's probably more like half a mile east of Monclair Village, in case you want to edit my other comment or add this correction.

  3. I haven't been there to look, but judging from the 1915 US Geological Survey map, the west portal of the tunnel must have been around what is now the corner of Shepherd Canyon and Saroni Drive.