Faceted spurs along the Hayward fault

A lot of geology involves glimpsing the ideal behind the real. As you look around Oakland, the Hayward fault isn’t easy to see without a bit of training. For this post, let me start you from the ideal. The process of faulting has very specific effects on the land that you can learn to look for, then see.

Motion on the Hayward fault is mostly sideways, but a small proportion of its motion is compression across the fault. Compression has been pushing up the east side of the fault for at least the last million years, building the Berkeley/Oakland Hills. Where streams cut their valleys across such a fault, the ideal result is something like this example from the Manti-La Sal National Forest, in Utah. The image is from the Open Topography site and is derived from lidar (laser “radar”) data.

faceted-spurs

The flat, triangular faces of hillside are called faceted spurs. As you look at this, imagine the motions and processes that create the landforms. The high part is being raised; the streams are cutting downward; the low part is sinking while the streams dump their sediment onto it.

That’s about as geometrically perfect as faceted spurs get. In Oakland, they’re much more subtle. The rest of the images in this post are large; click each one to see it full size. Here’s a 1000-pixel view looking north from the top of Mountain View Cemetery.

spurs-pano

The numbers are as follows: 1 is the north side of Claremont Canyon, 2 is the south side, 3 is Grizzly Peak, 4 is Hiller Highlands, and 5 is the nameless ridge (Powerline Ridge, I guess I’d call it) south of route 24 as you approach the Caldecott Tunnel. Except for Grizzly Peak, those are faceted spurs.

Here they are labeled in the 1915 topographic map, made before the Caldecott tunnel construction changed the hills. The asterisk is where I was standing.

spurs-1915topo

I’ve also marked them in this view from above in Google Maps, turned so the fault runs straight across the image.

spurs-google

And finally, here’s the same view in Google Earth, including the lidar data along the fault. The beauty of lidar data is that you can digitally subtract buildings, trees and so on to show the pure shape of the ground.

spurs-GE-with-lidar

Do these help you see? I hope so. There are other faceted spurs in Montclair and around Sheffield Village, at the far east end of Oakland.

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4 Responses to “Faceted spurs along the Hayward fault”

  1. ed matney Says:

    From the last Lidar image it looks like there are more faceted spurs to the south along the ridge.

  2. The Park Explorer Says:

    Thank you Andrew. Is lidar data available across the country?

  3. Andrew Says:

    Lidar surveys are still pricey. Opentopography.org has some scattered datasets, but at the moment only two are in New England.

  4. nbschiff Says:

    This is great. I’ve been thinking a lot about the Hayward Fault because of plans to build more houses on the parking lot at the Claremont Hotel. Might be good to take a bunch of photos up around there before they start bulldozing things. It would be a great time to do a walk in that area, using these images for reference.

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