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.


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.


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.


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.


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.


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.


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.)


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.


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?


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.


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.


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.


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.


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).


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


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.


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


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.


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


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.


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.


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.


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.


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.


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.


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.


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.


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.


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.


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.


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


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.


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


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


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.


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.


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.


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.


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.


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).


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.

Lower Piedmont Park walk (#28)

10 August 2012

Walk number 28 in Charles Fleming’s Secret Stairs East Bay winds around the fine homes and hills of Piedmont along the valleys of Wildwood and Bushy Dell creeks. Here’s the route, shown on the Google Maps topo base.

walk 28 topo

The first and last part of the loop is in the watershed of Wildwood Creek while the rest is in the Bushy Dell Creek watershed. (They run down Lakeshore and Grand Avenues respectively, separated by Warfield ridge, and combine down at Lake Merritt where their names are sunk in bronze by the pergola.) Geologically, the walk covers the uppermost part of the big Pleistocene alluvial fan and the edge of the Franciscan bedrock block that underlies most of Piedmont.

geologic map

We start at the Lakeshore-Winsor split in the stream valley and make our way toward the divide. On Portsmouth Road the high ground of the bedrock zone stands out ahead.

At the far end is a steep climb to Wildwood Avenue, where we can look back across the stream valley to the ridge topped by Calmar Avenue, on the Oakland side of the city line.

Turning the other way, we look over the valley of Bushy Dell Creek. Once a large formal garden, this part of the valley was filled and leveled for its current use as a sports complex. It appears never to have been a quarry, unlike Dracena Park to the north or Davie Tennis Stadium to the south.

We turn upstream along the creek, where the land is relatively untouched. Just above this spot is the site of what was reputed as a sulfur spring.

The geologic setting doesn’t really give much support for the presence of a proper sulfur spring like the one in Walnut Creek, but after all this time the question is moot. Certainly I didn’t notice any odor. The grotto was very pleasant anyway, and there’s real bedrock all around. It’s mapped as Franciscan sandstone of the Novato Quarry terrane.

The route goes farther up and takes a loop past a pair of boulders.

Take a close look at these: they’re genuine Oakland-style blueschist, globs of old ocean crust that have been carried tens of kilometers down into the earth along a subduction zone, then spat back out, possibly more than once. (The details are at the bleeding edge of California geology.) The one boulder displays good color and mineralogy:

The other has some nice slickensides to show us.

Coming back downstream and past the baseball diamond, we pass the entrance to the football field. The view looks down the valley toward the lake and downtown.

Near here we can see more exposures of the sandstone bedrock, but soon afterward the route returns to the alluvial fan. The two substrates make subtly different topography, but that can be hard to see given the heavily landscaped landscape.

Palm Drive offers a picturesque farewell view of the Bushy Dell Creek valley.

Again we cross the divide between the two watersheds at Wildwood Avenue. The near valley is accentuated by glimpses of the higher hills.

I never get tired of this stuff.

Here’s the route in more detail.

route map

The upper Piedmont walk (#29)

19 March 2012

This hills-and-paths walk is number 29, “Upper Piedmont Park,” in Charles Fleming’s Secret Stairs East Bay. It’s short and steep and quite scenic. Here’s the street route:

The geology is entirely on sandstone and related rocks of the Novato Quarry terrane of the Franciscan complex, so the geologic map looks a little boring, but the topography is on there too.

The numbers on the street route correspond to the photos that follow. The starting point is the elaborate exedra of Piedmont Park. It evokes the atmosphere of Piedmont’s first business, a “sulphur springs” resort that once sat here above the little city of Oakland.

Go behind the exedra and find the stairway down into the shady valley of Brushy Dell Creek. We have great weather in Oakland, but if you ever need to escape the heat, come here.

Brushy Dell Creek runs through a steep little ravine that exposes some bedrock ledges in the streambed: enigmatic Franciscan metamudstone. There is no trace of anything you might call a sulfur spring. Who knows what it really was.

This set of stairs on the other side is lined with serpentinite boulders for a colorful effect. But serpentine rock is not local to this spot; that would appear in the Franciscan melange higher up in the Piedmont hills at the Oakland line, the purplish patch in the geologic map.

After this the walk goes up into the hills where the views are wide. The local swales and ridges are charming.

The stairways and paths were designed into the neighborhoods back when streetcar lines served them. A hundred years ago it was still a virtue not to rely on a motorcar for commuting—automobiles were for pleasure and travel, and walking was simply the way humans were built to get around.

There is not a lot of bedrock exposed on this route, which is a bit surprising. But the Franciscan sandstone doesn’t have the variety of rocks that the melange has. It was quarried rather than cherished. However, this spot along Scenic Avenue exposes some of the shale that accompanies the sandstone.

Soon enough you get to the last, longest set of stairs. Be sure to turn around now and then as you ascend, to take in the views.

At the top is a little saddle from which you can peek across the neighboring ravine known as Moraga Canyon and spot the high Oakland Hills beyond.

The long stairs down from this point have the mark of their maker, the longtime contractor Ransome Construction Company. At one time Ransome operated the big Leona Quarry; at another time they were in Emeryville. Today they’re in San Leandro and going strong.

The end of the walk takes you along Highland Avenue, which as far as I can tell is the longest level road in Piedmont.

This topographic accident was surely exploited by the town’s founders to connect Moraga Avenue, the oldest road in the area, to the spring resort. And the street imposed its axis on the surrounding roads to make up the town’s largest area of traditional square blocks and straight roadways, a little bit of “flats” in a hilly community.


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