Archive for the ‘oakland geology walks’ Category

The Wild Oakland walk on the Hayward fault

9 November 2014

Saturday I led a walk for the members and friends of Wild Oakland to show off one of Oakland’s most striking places to encounter the Hayward fault. There was a nice turnout, about 60 people. I was glad to see so much interest. I hope that this post will enable those people, as well as all of you readers, to visit in person and learn more.

Here’s the route we took. It was just over 3 miles, although the altitude gain in the middle made some people bail out. Next time I’ll try to have alternative routes for their benefit.

WildOakwalkmap

The numbers refer to the stops during the walk. The asterisks refer to direct evidence of the fault’s activity, both on and off the day’s route.

Next is the same map with topography added. The thrust of the day’s exercise was to tour some distinctive features that the Hayward fault has left on the landscape.

WildOakwalkmapterrain

Stop 1, where we started, is where Arroyo Viejo does its abrupt 90-degree turn on its way from the hills to the bay. The right-lateral Hayward fault has dragged the Bay side of the landscape to the northwest, and the creek has had to bend in response.

WildOakwalk11-14-1

It’s a vivid example of how plate tectonics works in California, caught between the Pacific and North America plates. As the Pacific plate moves northwestward, pulled in that direction by subduction zones off Japan and Siberia and Alaska, it moves sideways—right-laterally—with respect to North America. That distorts the courses of streams that cross the boundary between the two plates. That plate boundary is a wide zone with three main sets of major faults running along it. The Hayward fault is in the middle set.

At Stop 2 I was able to point out a good example of creep offset, where the curbs on both sides of Encina Avenue have been cracked and shifted by creep (slow motion, less than 10 millimeters per year, without earthquakes) on the fault.

WildOakwalk11-14-2

Stop 3 gave us a decent elevated view of the fault zone from the Oakland Zoo grounds through that offset valley of Arroyo Viejo. (Here’s an earlier post showing the other direction.)

At Stop 4 I pointed out another probable example of creep offset, and everybody turned on cue to look at it.

WildOakwalk11-14-3

Stop 5 was at a highly disturbed bit of ground on Ney Avenue. The scarp crossing the road appears to be the head of a landslide right on the active trace of the fault.

WildOakwalk11-14-3a

Stop 6 was on a hilltop in the King Estates Open Space with a high view over the fault zone and the rest of the Bay area. The set of smooth-topped ridges extending into the valley of Arroyo Viejo have been cut off to form shoulders, and the dramatic shutter ridge on the right is the landform that has forced the stream to run sideways around it instead of straight to the Bay as it would prefer. (Here’s an earlier post about this same view.)

WildOakwalk11-14-4

I am quite taken with King Estates, and I believe it to be the largest piece left of the East Bay hills’ original landscape of grasslands. As the rains come this winter, I hope some Wild Oaklanders will poke around and examine it closely. For most or all of the people who came, it was their first visit.

click for 900-pixel version

Along the way is this nice little example of a landslide.

WildOakwalk11-14-5

The King Estates hills are mapped as alluvium of an earlier generation than the Pleistocene alluvium that makes up East Oakland’s low hills. I wonder two things about them. Are they a pressure ridge, pushed up by compression across the Hayward fault? (I noted that the fault’s motion is 90 percent strike-slip and 10 percent compression.) And what is to be learned from the blend of stones that practically forms a pavement on the hills?

WildOakwalk11-14-6

Stop 7 was a view into the watersheds of the three creeks above the fault: Rifle Range Branch, Country Club Branch, and Arroyo Viejo. And Stop 8 was in the valley of Country Club Branch, so close to its neighboring streams but so well separated from them by elevated divides. I blame the fault, which keeps jolting the countryside out of the equilibrium it seeks.

For dessert, I present a portion of Jim Lienkaemper’s 1992 map of the fault, which has annotations about the detailed evidence along it.

WildOakwalk11-14-features

The features marked G are geomorphic—things geologists notice in the landscape. Those marked C are hard evidence of creep—offset curbs (rc), sidewalks (rs) and fences (rf), and at Stop 2, echelon cracks (ec) across the road that have been erased by road repairs since 1991 when the map was compiled. You can download the whole map and consult the updated version from 2008 if you like.

Mountain roads

23 August 2014

Walking up Mountain Boulevard in the Laundry Canyon area takes you through one of Oakland’s old mining and timber districts. (Laundry Canyon proper is under the Warren Freeway.) First there’s the pyrite mine that I mentioned in the previous post. Then, looking up Bermuda Avenue toward the hills, you’ll spot a tempting area of exposed rock.

mtnroads1

That’s actually a switchback in the road that once served the Hotel Mine, at least that’s what’s shown in the Laundry Canyon historical map hosted on Oaklandwiki. The road meets Mountain Boulevard a little north of here.

mtnroads2

If this doesn’t tempt you, you have no blood in your veins. The land is within the city’s Leona Heights Park.

Knowing this historical background, it’s a safe guess that the flat Bermuda/Belfast Avenue neighborhood, with its sidewalks and homes dating from the late 1920s, is a former staging area for the various quarries and mines that once existed here.

Farther north on Mountain is the entrance to Horseshoe Canyon, the main attraction of Leona Heights Park. This path (technically, it’s Oakleaf Street) runs below the Leona Lodge and will take you all the way up to the former rock quarry by Merritt College.

mtn-leonacyn

A couple years ago, Dennis Evanosky led a walk through this neighborhood for the Oakland Urban Paths group.

Northern Upper Rockridge walk (#30)

27 January 2013

Walk number 30 in Charles Fleming’s Secret Stairs East Bay, which he refers to as upper Rockridge west, goes from the Rockridge BART station over the Franciscan bedrock hills of upper Rockridge. The views are great, and there are a few rocks as well.

Here’s the route map (click it for a larger version).

walk30routemap450

And here’s the route shown on the geologic map. It goes counterclockwise.

walk30geo

The orange Qpaf is old alluvial terrace, KJfm is Franciscan melange, and fg is Franciscan greenstone (you might see a little of that near the end if you’re vigilant). Melange is lumpy stuff, as I’ve said before, mostly shale with knockers of harder rocks here and there.

And here’s the topography, with the sites of the following photos marked on it. The walk basically circles the bowl cradling little Rockridge Park with a couple of forays over its rim.

walk30topo

The new parklet at the BART station is nice. Naturally the boulders were sourced elsewhere.

walk30-1

The first part of the walk is housewatching until you cross Broadway to Rockridge Boulevard, where you face the hills through an allee of big palms. We’re at the 200-foot contour and looking at homes above 400 feet. It’s steep land, but not as bad as the high hills.

walk30-2

Once you get up into the hills, you get views in all directions. Pick a good clear day to do this walk.

walk30-3

As you go along Acacia Avenue, keep an eye out for Cactus Rock, reputed to be The Rock that gave Rockridge its name. I’m not fully sure that’s true, but I’m at a dead end in that quest at the moment.

walk30-4

The high point of the walk is on Alpine Terrace, at about 450 feet. It has several empty lots left over from the 1991 Hills Fire. This one always gives me a qualm.

walk30-5

The top of the elaborate Brookside Steps features this gnarly boulder, which I’ve featured here before. This is what they should have used down at the BART station.

walk30-6

As you wander over to the north end of the loop, enjoy the views that way. Here we have the chaparral of Claremont Canyon, the homes of the Claremont Hills neighborhood, and in front the solar roof of the College Prep School, which I was pleased to see produced a finalist in the Intel Science Talent Search this year. That is a huge brag for Oakland.

walk30-7

Here’s a view of upper Hiller Highlands, including one of the two big round houses up there. This is the lower one, at the end of Devon Court.

walk30-8

And here’s the view east toward the eastern, higher crest of upper Rockridge studded with homes. A glimpse of uppermost Broadway Terrace is at left. All the distant points in these last three photos are across the Hayward fault.

walk30-9

The long, sturdy stairway was constructed by Schnoor & Son. By my reckoning, that makes this 100 years old. Other sidewalk stamps up here date from 1913.

walk30-10

We’re finally going back down in to the bowl of Rockridge Boulevard, so you can see now what those high homes have for views—straight out the Golden Gate. The good burghers who settled this area a century ago would take these steps to catch the streetcar to their jobs across the bay.

walk30-11

Here’s the view of Claremont Canyon from Broadway and Keith. The white bit by the traffic light is the tower of the Claremont Resort. The nearer ridge is just in Berkeley across the valley of Temescal Creek.

walk30-12

And from here it’s a straight walk down to the refreshments of College Avenue. There are bits of bedrock along the upper part of Keith, but then you’re back to the lowlands.

Lakeshore ridges walk (#26)

31 December 2012

Walk number 26 in Charles Fleming’s Secret Stairs East Bay traverses Longridge and its neighbor Calmar ridge, sticking to the paths and stairways. It doesn’t really give you the full experience of the ridges themselves (I plan to make posts for each), but it’s still fun to learn the local shortcuts. Here’s the route map on Google Maps terrain.

walk26topomap

You can see that Longridge Road and Calmar Avenue are both ridge roads, which are especially desirable for developers and homeowners because everyone gets a great view unless the downhill neighbors decide to plant redwoods here, where the habitat is wrong.

The geologic map shows that essentially all the route is in the Pleistocene alluvial fan or, as I’m starting to think of it, the Fan.

walk26geomap

The walk starts at the fine iron gateposts at the foot of Longridge Road. Locations of these photos are noted on the geologic map.

walk26-1

You ascend the ridge along its gently but persistently sloping crest, then sidestep into the private Oak Grove Park along its northern flank. The view here gives a glimpse of Mandana valley, between the two ridges, and the high spine of the Oakland Hills.

walk26-2

Most of the path is quite secluded, though. This entire neighborhood started out as grassland, like most of Oakland.

walk26-3

At the other end of the park is steep Paloma Avenue, providing good views of Calmar ridge across Mandana valley.

walk26-4

And here’s Mandana Boulevard, running down the floor of its stream valley. The creek here is entirely culverted and appears never to have merited its own name, probably because it was seasonal.

walk26-5

Now comes the hardcore stairway portion of the walk, straight up the flank of Calmar ridge and over its top down to Balfour Avenue, shown here. The stairway here is quite hinky, which distracts from the view of Grizzly Peak over the north end of the Piedmont bedrock block.

walk26-6

Another stairway takes you down to Walavista Avenue, running up its own valley. At the street’s upper end you hop over a subtle divide into the valley of a tributary to Wildwood Creek, traversed by a quiet, funky little path that butts onto another path connecting Carlston and Portal avenues as a continuation of Santa Ray Avenue. In 1912, this valley was a Key Route line.

walk26-7

You take the right hook onto Carlston and back down across Mandana valley, ready to climb Longridge again. The little pocket park across Mandana, on the right, is a good place to kick back on a bench.

walk26-8

The route takes a jog along Paramount Road, which happens to occupy the crest of the ridge here while Longridge Road is a little off to the side of its namesake. At the far end of Paramount, where the Fan leaves off and the Piedmont block begins, the terrain starts to change and Longridge peters out as a proper ridge. Right on the geologic line is the Crocker Highlands Elementary School.

From here the route goes along the south slope of Longridge and its stairways. This is part of the Trestle Glen neighborhood, but I don’t think of it as part of the glen itself, that is, Indian Gulch. Keep an eye out for views like this, from Longridge Road near the end of the walk.

walk26-9

Winter is a good time to take this walk, while the leaves are down. Here’s the detailed route map (click it to see full size).

walk26map450

Fleming calls this walk “Trestle Glen and Lakeshore Highlands.” The part of this neighborhood north of Mandana was developed as East Piedmont Heights.

Linear scarps

1 September 2012

Next Saturday, 8 September, I’ll be leading a short, rugged urban walk for Oakland Urban Paths that among other things will visit these faceted spurs along the Hayward fault. Seen from the north . . .

view south

and from the south:

view north

The downhill side is moving north with respect to the near side. The open land in the foreground is the King Estates Open Space.

This will not be a stairway walk. The off-street passages are steep, weedy dirt paths that have not been maintained. The land along the fault is steep, making for nice residential view lots. I haven’t finished the route yet but it will take no more than 90 minutes, 10 to 11:30—I have a lunch destination I’m anxious to make. So I would like to set a good geologist’s pace. Details and questions as they come to you over at Oakland Urban Paths.


Follow

Get every new post delivered to your Inbox.

Join 8,796 other followers