One among my little geological fetishes is a geographic one: circumambulations. Due to the Hayward fault, Oakland has acquired a number of wineglass valleys, with very slim mouths and huge headwaters. I’ve pioneered hikes that circle three of them: Claremont Canyon, Temescal Canyon and Shepherd Canyon.
These are strenuous outings, and I’m getting much less and fewer younger. This 12 months I hope to renew them, however it should take some working as much as. However I had a brainstorm: what concerning the faceted spurs between the wineglass valleys? I’ve written about faceted spurs earlier than, but it surely felt sort of obscure so let’s strive once more.
Right here on the 1897 topo map I’ve outlined the faceted spur that overlooks Montclair, between the slim mouths of Thornhill and Shepherd Canyons. The fault runs from the higher left nook to the center of the underside edge. The spur is about 700 toes excessive and a loop on it’s about 2.5 miles, versus an additional acquire of 300-plus toes and 4 extra miles for the circumambulation.
Visualizing this topography with the digital elevation map and picturing the hills coated with grassland, the way in which they was, I’m considering this is able to’ve been a picturesque hike, on ridge routes the entire method.
You may see that the spur doesn’t have the best flat side — it’s been dissected considerably into small valleys — however the ridges that make up the rim are nonetheless good and powerful. And numerous the streets run alongside the rim to supply a good approximation of that 1897 hike. Right here’s the route, ranging from the tip of the 33 bus line; I’ve taken it each methods and I really feel fitter already. If you happen to do this, be very cautious as you stroll alongside Colton Boulevard.
Zoom in on the route at gmap-pedometer.com
The triangle of streets inside this loop isn’t a part of both Thornhill Canyon on the north or Shepherd Canyon on the south; you would possibly name it pure Montclair. It faces southwest, and as you climb you start to peek over the Piedmont crustal block towards the Golden Gate. This view is from the north finish, the place the ridge runs east-west . . .
and this one is from the south finish, the place the ridge runs north-south.
On this ridge too, Asilomar and Drake Drives supply open views over the mouth of Shepherd Canyon towards the South Bay.
Word a few issues on this view. The notch behind the tree within the center is the place the San Andreas fault runs in addition to Route 17 to Santa Cruz. The LDS temple to its proper is the place the Hayward fault runs, persevering with proper by way of Montclair alongside the freeway. The little valley that holds Montclair owes its existence to the fault, which grinds the rocks to an simply erodible state. Elsewhere alongside the route, you may look north alongside this valley, as right here on the northernmost finish of the Montclair Railroad Path.
The 2 ridges meet simply above the Forestland Reservoir, which is a pleasant quiet place to have a sit earlier than beginning down — or heading farther up the principle ridge to the wonders of Skyline.
The rocks alongside the way in which are all just about the identical: medium-grained sandstone of the Redwood Canyon Formation. The south finish of the loop is mapped because the Shephard Creek Formation — sandstone plus shale — however you received’t see any of it.
I’ve no nice insights or cool issues to notice about these rocks. Like I mentioned, walks like this are a geographic fetish.
