A closer look at Haddon Hill

6 June 2022

My book manuscript (now in the copyeditor’s hands) has a chapter about the Fan, our peculiar region of gravel hills that stretches from Pill Hill to Evergreen Cemetery. In the book I refer to it as Oakland’s second level. I briefly recount its human history, starting with the trouble it caused the initial Spanish exploring expeditions (led by Fages in 1770 and 1772 and by Anza in 1776), then go on:

“Today, whether we drive, ride or walk across the second level, we can still see the underlying landscape and picture how it looked to our predecessors. The eastern, uphill side of the Fan, toward the Hayward Fault, is a string of hills of the third level, most of which are bedrock. The downhill side, toward the Bay, is a variegated landscape of low rises and small gaps through which the Bay sparkles and distant mountains across the water loom, in detail or in silhouette as the weather changes.”

What drives this passage is the bit about picturing how things looked to our predecessors. That might sound romantic — and it surely is — but it’s also a basic skill of geologists, especially in the urban setting.

I sometimes think that as I look around at the Fan, I’m craving glimpses of the hills as they appeared to the Ohlones during the thousands of years they were managed as meadows, the way they appeared in the 1850s when the Town was founded. The Ohlones kept the hills clean to support their lifestyle. Today we keep the hills populated and planted in trees to support our lifestyle. Before humans lived in this country at all, during the ice ages and the warm breaks between them, these hills were either oak-bay woods or cold savannah depending on the climate. The best time for geologists was during the Ohlone years, when the Fan was laid bare.

There are no images from that time. We can only imagine how it looked and felt. To illustrate the tools I use, let’s take Haddon Hill, in the heart of the Fan next to Lake Merritt, as an example (specifically, it’s the Haddon segment of Lobe 4).

First there’s the Bache map from 1857. Although it was primarily a navigation map, it showed details of the surrounding land as well, including Haddon Hill.

The physiography isn’t very precise, but the shoreline and roads can be considered reliable.

Second is the digital elevation map (available in the National Map viewer), which strips the buildings and vegetation off the land.

The composite map, made using the transparency slider, is less stark and easier to deal with.

Haddon Hill is a triangular area defined by the lake, the freeway and Park Boulevard. It has two easy avenues through it that go up little valleys, the northern one on Wesley Avenue and the southern one on Athol Avenue. All the other roads tend to be straight and ruthless. If you walk or bicycle here a lot, you know this already.

When Oakland was a tiny town huddled at the foot of Broadway, Haddon Hill had a road running south through it, undoubtedly based on an Ohlone path, that climbed up from Indian Gulch where Wesley tops out, worked along the 100-foot contour and eased over the hill where Haddon Road meets Brooklyn Avenue, then went down into the southern valley where Athol runs today. (The path branching off to the east along the hill’s crest is probably the route Anza took in 1776.) That all changed when the settlers moved in and cars took over everything. Today gravity doesn’t matter as much, and when we read Friar Juan Crespi’s account of traversing the hills here, “which, although they are all treeless and grass-covered, annoyed us very much with their ascents and descents,” maybe we don’t feel it like he did in 1772.

The old road came down Athol from the right in this view north from the intersection of Athol and Newton Avenues.

Finally we get to the geology part.


Qpaf, Pleistocene alluvium (the Fan); Qmt, Pleistocene marine terrace; af, artificial fill

The “Qmt” part is the same marine terrace that runs through Clinton, and I have to say I disagree with the map. I think the terrace extends only to the “P” in “playground.”

Whenever I venture into the Fan, I’m beguiled by the neighborhoods but always look past the homes and landscaping for the wider views. Here are a few examples from 21st-century Haddon Hill. They tend to come in glimpses. This glimpse from across Park Boulevard, at 9th Avenue and E. 28th Street, shows the St. Vartan church, conveniently on Haddon Hill’s highest point, and Grizzly Peak.

This view down Booker Street shows the lower part of Haddon Hill hiding Lake Merritt in front of downtown. Brooklyn Avenue is just visible in front of the Ordway Building.

This view downtown looks down Cleveland Avenue across the Wesley Avenue valley.

And finally, here’s looking across the Athol Avenue valley at St. Vartan from the top of McKinley Avenue.

Wherever you go, smell the roses.

Rocks with character

23 May 2022

I turned in the final version of my book manuscript the other day, and it’s been nice not having it on my mind all the time. (Follow along with the publishing process on the book’s page here.) But I had occasion to visit Middle Harbor Park this weekend, and as I walked up to this spot it brought to mind a little exchange I had with my editor. This is the replica pier made of reclaimed stones from the 1880s-era training wall.

I was writing about the work of building Oakland’s harbor, which has gone on since the 1850s and continues today. I mentioned that while the original estuary was completely replaced with “made land” and its counterpart, made water, there were now rocks — riprap — where before there had been only mud and sand. I contrasted the old original riprap to what they use today, with this pier in mind, and said that while the new stuff may work better, it has “little character.”

My editor wondered if I could explain that a little more. I decided not to for two reasons: (1) that would be a digression from what was already an aside and (2) the book has lots of examples of rocks with character.

But I came home thinking I’d been a little unfair. For one thing, our new riprap isn’t so monotonous; it’s mostly gray lava, but many of the rocks have veins and texture. Quarries in the Coast Range dig rocks that have gone through a lot, compared to the granites of the Sierra and those truly monotonous limestones of the Midwest. And the other thing is that the replica wall was made of carefully selected stones. It’s a work of art, not a work of work.

Next time you’re down there, look up the pier, at the south end of the beach. Walk on it and feel how solid it is underfoot, a standout piece of stonemasonry. It’s a real Oakland character. But also, check out the other riprap some time.

Oakland is full of rocks with character, and naturally so is this blog. Here are a few choice posts with examples from all over town:

The high-grade wall of Broadway Terrace

The decorative blueschist of Fairmount Avenue

The mastodon rubbing rocks of Tilden Park

The Knoxville conglomerate in Arroyo Viejo

Residential walls of local stones

And of course Big Rock at Lake Temescal

In fact, Oakland by my estimate has more natural rock types than any other city in the United States, making it America’s capital of lithodiversity

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 crude . . .

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.

Source

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.