Rettig canyon

I paid a visit yesterday to part of the Hayward fault in Oakland, but while there I felt the pull of a neighborhood treasure I call Rettig canyon. The name is from Rettig Avenue, which traverses it. Here’s the topography, from Google Maps. This is just south of the LDS temple.

rettig map

The fault runs from top middle down Jordan Road and exits where Victor Avenue leaves the map. The hills to the west are the southernmost part of the Piedmont block of Franciscan rocks. Rettig canyon cuts right through the hills thanks to Peralta Creek, which comes here from Butters Canyon on its way to the bay through Peralta Hacienda and Foothill Meadows Park.

Normally when you see a stream cutting through a bedrock ridge, you explain it as either stream capture or a water gap. That is, either the stream eroded its way headward through the ridge or was running that way already when the ridge rose underneath it. Given the intense tectonic activity here, I’m inclined to call it a water gap, as I do Dimond Canyon (with the addition of tectonic stream capture).

I saw some possible evidence of this in the streambed. But first, a look at the scene.

rettig road

Rettig Road is a single lane through the canyon and is coned off as a landslide zone. It’s been that way for at least six years; I hope a local will say more in the comments. The canyon is steep, dark and thickly wooded. You can scarcely see the stream, but you can hear the water everywhere.

rettig canyon

But there is a place to scramble down to the streambed. It’s well populated with rocks that appear to be local Franciscan melange, pretty jagged and hence not transported far.

rettig streambed

I was looking for bedrock and found some candidates like this scaly schist. I didn’t have my hammer and was reluctant to disturb the scene anyway, so I can’t say much about it. It might be serpentinite.

rettig schist

This is the outcrop that excited me, showing what looks like a thrust contact.

rettig contact

Ignore the green patches; that’s just algae. The rock on the left is fairly soft and foliated parallel to the contact. I picked out a small piece and can’t say much about it, but in the hand lens it looks like a highly altered talcy kind of stone. At the base is a good centimeter-think layer of nice gray clay, then we hit clean tightly packed sediment with highly tilted bedding; indeed it’s tilted steeper than the contact above it. So my best guess is that it may be the contact between the Franciscan and much younger Pleistocene sediments. Due to squeezing along the Hayward fault, the older rock has been thrusted up and over the sediment. This isn’t unheard-of, but I haven’t seen it documented around here so I could easily be wrong. But that would explain the rising ridge, the topography of Jordan Road (which sits in a long trough here that may well be a sag basin) and the course of the stream.

I couldn’t resist bringing home a pocket-sized cobble of beautiful actinolite schist.

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11 Responses to “Rettig canyon”

  1. Dennis Evanosky Says:

    Thanks for this great post. This is a magical place with a lot of give and take between the neighbors and the city and among the neighbors, some want development, others preservation.

    Here are some links to background information from the MacArthur Metro. I’ve also copied and pasted a story from Oakland Magazine about the canyon’s biggest proponent, Denise Davila.

    http://macarthurmetro.org/200511/shen

    http://macarthurmetro.org/200502/shen

    http://www.macarthurmetro.org/200505/news/587

    Maintaining Homegrown Roots

    Denise Davila has a lot to say about her neighborhood, Redwood Heights, considering she’s lived there her entire life. She currently resides in her grandmother’s 1930s home on the street that she grew up on. All told, her family has been in the neighborhood for almost 80 years (Davila is 40). “We’ve seen a lot of changes over the years,” she says. “All this time, Redwood Heightshas remained a desirable, family-oriented neighborhood.”
    Davila attended Redwood Heights Elementary School and has fond memories of riding her bike around the neighborhood after school, ending up at Avenue Terrace Park to play with friends.
    “I know of three people who recently bought into the neighborhood, because they grew up here and wanted to raise their kids here,” Davila says.
    After the 1998 El Niño storms, a landslide made Peralta Creek accessible once again to Redwood Heights residents. The landslide closed off Rettig Avenue near Wisconsin Street and opened up nine acres of creekside that has since been designated a wildlife corridor. Davila and her neighbors have played an active role in the restoration of Peralta Creek, forming a nonprofit group, Native Environment Watershed Transformation, or NEWT, to maintain the banks and creekbeds. Davila, who also leads creek field trips for local school groups, is an education specialist with the nonprofit Community Resources for Science and a professor and teacher-trainer for the education program at CSU East Bay, so the Peralta Creek work has been close to her heart.
    Neighborhood organizing is another part of what makes living in Redwood Heights so enjoyable, says Davila. In addition to the large Redwood Heights Neighborhood Association, there are numerous subgroups of neighbors who organize around various issues. Davila serves as co-editor of the Redwood Heights quarterly newsletter, which goes out to 1,400 residents.

  2. Mike Says:

    Do waterways have a tendency to follow faults? It seems to me that they do, as I often see offsets around a waterway.

  3. Andrew Says:

    Thanks, Dennis. I must have first visited the canyon back in 2005, because I recall the work going on in the slide area. I’m pleased to see that the canyon didn’t suffer from that work, as the neighbors feared. The walls are ugly but probably as sound as these things can be built.

    Seeing the little park at the foot of Rettig, obviously cared for by the residents, made me feel good.

    As for development versus preservation, it probably won’t surprise anyone that I would favor very light and expendable development this close to the fault.

    Mike, our local faults grind up the rocks between them, making them tend to erode easily. But the steady sideways stretching of the landscape also encourages the streams to get longer in the same direction as the fault. You’ll see this strongly on the map between San Francisco north to Cape Mendocino.

  4. donna gatts Says:

    Thats great! I love the area also. Have you been to end of Jordan, there was a huge landslide there as well, maybe at the same time as this one?

  5. Andrew Says:

    I looked at every place I could reach. If there’s a slide at the end of Jordan Road, it’s behind someone’s gate. The property lines in Google Maps suggest some rights-of-way in there, though.

  6. donna gatts Says:

    Jordan follows the creek and at the end of the road, there is a smaller private.. road, as you walk along it and look to the left, the whole hill came down. There is a house, it was pink, on the left side, and atleast half of the hill under the house came down at some point. I havent been back to see if they have finished work on the house.

  7. m. Carey Says:

    A large landslide occurred on the NW-facing slope between Norton and Rettig in February 1998. A 20-ft. high headscarp was located directly behind three houses along Norton; these houses had to be temporarily abandoned. The underlying bedrock on the southern slope is Leona “rhyolite”, which is very contorted and weathered. The slide involved several lots, and of course, it is always difficult to coordinate repairs among the various property owners. Google-earth photos show that there was some sort of stabilization done in June 2007.

    I have not been in the creek itself, and therefore have never seen that nice contact with the green actinolite rock. You can see the red Leona in the photo you included in the post. I will brave the poison oak sometime and check it out.

  8. Liz Says:

    Hi, thanks for this wonderful post. I really enjoy reading your blog. Just wanted to let you know we shared a link to your blog on our website: http://www.totallyunprepared.com/2011/08/quake-hike-series-hayward-fault-hard-to-see-but-easy-to-find/

  9. Andrew Says:

    Thanks, Liz. By the way, the photo on your page does not show the Hayward fault, which doesn’t enter Tilden Park. See the viewer at http://pubs.usgs.gov/ds/2006/177/HF_index.html

  10. Nancy Says:

    There was a landslide in the late 60’s/early 70’s and approximately 22 homes were lost — some sliding into Peralta Creek, near the 3000 block of Jordan Road. The homes that slid down the hill were situated on Kitchener Court (right side of the street going toward the Mormon Temple) and London Road, slightly below. Before the landslide, London Road was at very end of Maple Avenue (to the left) and you were able to drive down London Road and end up at Jordan Road. The road was never rebuilt. There is still a London Road street sign at the end of Maple Avenue! I’ve even noticed that some street maps still show London Road as it was before the slide. Over the years, I had heard about this landslide and went to the Oakland Library History Room, and found the “Oakland Landslides” folder and came across many articles from The Oakland Tribune about the Peralta Creek landslide.

  11. Andrew Says:

    Thanks for that, Nancy. I need a copy of that folder.

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