Rocks in the gutter

9 May 2022

Down in the Chinatown and Produce District area, we have some special rock-lined gutters, ranging from fine . . .

to funky. They’re the nearest thing Oakland has to cobblestone streets, and they serve the same purpose: heavy duty traffic.

The variety of these gutters suggests that they were emplaced over a long period, under various city contracts. Given that, it’s probable that the stones come from several different sources. But nearly all of them are basalt, the fine-grained, gray to black lava erupted from volcanoes up and down the western states.

These days basalt is a fancy stone, as seen in finer landscapings like the courtyard of Berkeley’s new School of Public Health building. These are natural hexagonal cooling columns of basalt, like those up at Devils Postpile in the high Sierra, cut and polished for elegant seating.

But our gutters are lined with prosaic basalt. And I think some of it came from our own hills. The Sibley Volcanic Regional Preserve includes the grounds of several former quarries that produced basalt rock. In 1906, State Mining Bureau Bulletin 38, The Structural and Industrial Minerals of California, reported on the first of these, the Ransome Quarry: “This quarry is on the Old Fish Ranch road, about 5½ miles from the Oakland City Hall. It was opened in April, 1904. A tramway 600 feet long carries rock from the quarry face to the crusher at side of road. The rock is a fine-grained basalt, and is used for macadam and concrete. Some gutter rocks are sorted out. The rock is hauled to Oakland and Berkeley by wagon.”

Sibley’s lava flows aren’t the enormous, massive ones of Oregon and Washington’s Columbia River Basalt, a genuine Large Igneous Province widely attributed to the hotspot that now underlies the Yellowstone region. The Sibley volcano is a dinky thing with a lot of different deposits ranging from ash beds to proper basalt.

I like to think that a couple workers up there kept their eye on the rock and picked out good bits for this premium trade. I imagine that those are the rough gutter blocks. The later street contracts probably used more economical, higher quality material from farther away, like the North Bay counties or even Black Butte up near Orland.

Nowadays, for better or worse, we keep it simple and use concrete or asphalt, even though the work needs more repairs.

Return to Pine Top

25 April 2022

A brief visit to Mills College for the recent pow wow reminded me of some business — not unfinished business, but rather an inquiry ready to renew. The upper end of the Mills grounds is very different from the lush central campus with its beautiful floodplain setting, and it has the possibilities of bedrock and fault-related findings. And it’s been seven years. To refresh our memories, here’s the geologic map.

Pine Top is labeled Jb next to Lake Aliso at the east end of Mills College. Qpaf, Pleistocene alluvium (the Fan); Qhaf, modern alluvium; Jsv, Leona volcanics (Jurassic); Jb, basalt; Jgb, gabbro

I’ve always wondered about Pine Top. It stands up so steeply and dramatically at the foot of the high hills, right on the Hayward fault (which is poorly localized here). The digital elevation model of the hill makes it look as if it had been quarried, and indeed there are records of a quarry on the college land.

I’ve also wondered about Pine Top because the basalt “Jb” is hard to find, and I came up empty on my first visit. The hill appeared to be fully mantled in soil.

The campus is especially pretty right now. I hope they can get past their problems and resume their long successful history in Oakland.

Lake Aliso is its usual self, thanks to the late-season rains.

Supposedly the lake is a sag basin related to the Hayward fault, but I’m starting to think that it owes its existence entirely to damming.

This old photo of the lake, from around 1893, shows the side of Pine Top nicely forested in oaks, which would not be the case had there been a quarry there. I think the quarry was located north of the lake where the freeway now runs.


This time I found the original footpath up the hill. Students used to have costumed processions up this path, bearing torches and regalia.

At the top, they would assemble around the Hearth and enjoy their celebrations.

Maybe some alumnae with long memories can add comments about how it used to be.

The view from the top has closed in as the trees have grown, but in the old days it was surely fine.

But anyway, this time I found bedrock — well, pieces of it, around the big microwave tower that was emplaced up here since my last visit. Here they are arranged for a portrait. I also found a little in the old footpath.

This is not basalt by any means, not even a highly altered basalt. This is the highly altered ash of the Leona volcanics, what the old-time geologists with their eyeballs and hand lenses called the Leona Rhyolite. That calls into question not only the “Jb” label for Pine Top, but the whole stripe of Jb drawn on the geologic map. Just some more things to go and check out this summer.

McAdam’s quarry

11 April 2022

One of my first outings during the pandemic era was a hike up Shepherd Canyon in search of Alexander McAdam’s sandstone quarry. But I was missing a telltale clue. Now I think I’ve found it.

I wanted to locate the quarry because it produced the stone used in the historic First Unitarian Church in downtown Oakland, the only example I’ve found of a truly local rock used as dimension stone in a building instead of crushed stone in an anonymous construction.

The clues I had pointed to a location “at the head of Thirteenth Avenue” somewhere “in Medos Cañon, back of Piedmont.” I thought this meant some place in present-day Montclair, but all the old maps I checked didn’t show any land there belonging to McAdam. Then I tracked down the 1894 Wagner map of Alameda and Contra Costa Counties, and here’s where his ranch was: over the ridge above Shepherd Canyon, in the valley of Redwood Creek.

Shepherd Canyon in the center; the old Thorn Road runs around its north edge. The Heyland property at lower left is in Dimond Canyon and the Hays School is in present-day Montclair. The McAdam property is at lower right past the county line, shown by stippling.

The land is within Redwood Regional Park, so I surveyed the territory last week. Here’s a closeup of the map, showing McAdam’s 131.24 acre holding.

And here’s where it sits in the geologic map.

This is very steep country, in an area where the redwood groves had been logged out forty years before. McAdam used it as ranchland, like others in this remote district, but he also operated a successful quarry here somewhere. It wasn’t in the coarse, crumbly Oakland Conglomerate (mint green) or the shaly stuff of the Shephard Creek Formation (pale green), but somewhere in the thick-bedded, fine-grained sandstone of the Redwood Canyon Formation (Kr on the map, olive green).

Fortunately, Redwood Regional Park maintains the old trails and logging roads, so I superposed McAdam’s land on the park’s trail map and gave it all a good look. Note: the poison oak is very healthy this year.

The only place a quarry would make sense is at the very top of the property, but if you’re up for it, the Tres Sendas trail takes you down to some nice woods.

The rock here is appropriate, just like the stone in the church.

And some of it fractures nicely enough to be dressed into ashlar blocks.

But it would be nuts to operate a quarry down in the back forty. Up on the ridgetop in the northwest corner of the land is where I think McAdam had his pit. It’s the backdrop of this view over the spot where McAdam’s ranchhouse was, at the westernmost corner where the Waterloo Staging Area is today.

It was accessible via the Castle Canyon road, as seen in the 1897 topographic map. The McAdam place is in the center, at the end of the road.

The hilltop is just off high-lonesome Wilton Drive, where I last took you three years ago for the Shepherd Canyon circumambulation. The views from there are still wonderful.

The slope immediately below, too steep to think about descending, is where I think the quarrying went on. The outcrops of Redwood Canyon Formation display good rock.

I’m glad to put this little mystery to bed. And if the Unitarian Church must replace its stone with authentic materials, they know where to look.

Glimpses of Glen Echo Creek

28 March 2022

This is an inventory of what’s left of Glen Echo Creek, a stream with an outsized significance in Oakland’s history of development and planning. I used to live in its watershed and retain a strong affection for it. The photos in this post document every bit that’s accessible to the public. But first here’s the watershed map, courtesy of the county flood control district.

I’ll focus on the main branch, labeled “Cemetery Creek” in its upper reach (the Rockridge Branch on its north side is worth its own post). You can see that close to 90 percent of the creek runs underground today in culverts. Cemetery Creek’s headwaters, in Piedmont’s Moraga Canyon, are buried under Blair Park; the creek trickles out below Coaches Field at the edge of Mountain View Cemetery’s property.

From there the water goes through the cemetery’s three little reservoirs. This vintage view over pool number two is from my post celebrating the cemetery as the Bay area’s best landscape.

Once past the cemetery, the stream is known by its developer-inspired name of Glen Echo Creek. The upper portion, shown in this closeup, has four small segments of living water.

The first two are in back yards, and I’ve never seen them. This is the third, a brief flash at the end of tiny Arroyouela Avenue.

The fourth segment is partly public and partly private. The entrance to the Glen Brook Terrace includes two bridges and a sewer line, one of dozens I’m sure.

Just downstream is the narrow preserve, two residential lots wide, named Glen Echo Park. Neighbors help maintain it. The part above Monte Vista Avenue has a bit of the old floodplain. That’s where the stream flowed before white people came in the late 1700s. The disturbances they made to the countryside led all the little streams to cut into their floodplains forming the steep-sided arroyos we know today.

The creek enters a tunnel and comes out a thousand feet away, under I-580. That’s in the lower portion of the map, shown here.

Starting with Frederick Law Olmsted in the 1860s, thought leaders had a vision of the city laced from the shore to the hills by arterial parklike streets along each of the streams. Charles Mulford Robinson, a leading figure in the City Beautiful movement, was all about using our stream valleys for elegant roads with exquisite views.

The planner Werner Hegemann cited that vision in 1915: “A little suggestion of Charles Mulford Robinson’s plans may be found in the charming piece of a drive following for a short distance Glen Echo Creek under the name of Richmond Boulevard; though this has been carelessly handled by crossing the creek in some places by crude solid fills instead of light bridges, the elegance of a drive along a creek bordered by live oaks in contrast to the baseness of the use of the stream as a storm sewer is very convincing.”

It’s hard to square that picture with today’s dark, overgrown Oak Glen Park.

The envisioned road would never serve serious traffic, and the creek is far from a natural stream. Its fortified banks are choked with English ivy, Himalaya blackberry, French broom and other invasives, with no cleansing floods to clear them.

From here the stream runs privately through front yards, then a concrete ditch behind the Grocery Outlet.

The mappers of the flood-control district missed a final exposure, next to 27th Street at the black dot on the map. This is the last place one can hear the water speak.

Still farther downstream, at the second dot on the map, a ghost of the old creek was exposed as construction began at 24th and Harrison. This is the path of a long-disused culvert, being cleaned out and buried last week.

A photo sent by a reader shows details from a few weeks ago.

Finally we have the wholly artificial channel leading to the creek’s mouth at Lake Merritt.

One of Oakland’s great civic failures was its inability to preserve the natural streams. It took seven generations to reach this state, and it will take seven times seven to undo even part of it. Until then, we can only perceive the moribund creek in the topography of its valley, an echo of the glen it left us.