West Oakland topography

West Oakland has always been flat and easy to build on, whether it was for factories like the old Shredded Wheat plant built in 1915 (still operating as California Cereal Products) . . .

or for the middle-class Victorian homes that are West Oakland’s pride. It takes a lot of walking around to note the subtleties of the landscape. Except around Raimondi Park, the area was never a coastal marsh but was slightly elevated sand dunes, the same Merritt Sand that underlies downtown. In the Ralph Bunche neighborhood, north of 18th Street between Market and Adeline, the homes perch above the street, not by much but consistently.

Even century-old homes sit up the same way as the newest places. Presumably the streets were dug down, but maybe the lots were piled up too. Perhaps flooding was a concern, and all the earth-moving created more desirable lots here. Only a historian with intimate local knowledge could say.

If you look north along any of these streets (Chestnut, Linden, Filbert, Myrtle), you’ll see the land sink at Grand Avenue where the Merritt Sand leaves off.

The I-980 swath

Interstate 980 is a huge convenience for drivers. I appreciate it every time I drive around town. But its construction was a major injury to Oakland’s neighborhood fabric, splitting West Oakland from downtown harshly and irrevocably. Every time I walk over 980, as here on the 14th Street overcrossing, I ask, Did they really need to hack out all this space for the freeway? Farther north, where the road becomes route 24, it’s narrower and they left a fringe of homes on Martin Luther King bordering the highway. But on 980, the excavation took out a full city block between Castro and Brush streets.

Maybe the difference was the sand. I-980 is built in the Merritt Sand, which underlies downtown and West Oakland up as far as Grand Avenue. The ancient dune sands probably can’t sustain a steep slope on the sides of the freeway. And the builders had to dig deep to make room for the overcrossings—most of the other freeways are not below grade. A narrower roadway, with tall vertical soundwalls on either side (like the new part of the Nimitz farther west in Bay mud), would not be as safe during earthquake shaking, and without room for the vegetation it would be a dreary place indeed. Bad as it is, it could have been worse.

Displacement at the Altenheim

The Altenheim complex is on top of the northern side of the Sausal Creek valley, just across the freeway from the reservoir near the McKillop slide. There seems to be a little ground displacement here, too.

This view shows the downhill side of the property, on MacArthur Boulevard where it takes a leftward jog north of upper Fruitvale Avenue. The more I explore the stream valleys cutting through the Fan, the more of this I see.

Longridge loess

I was walking up Longridge Road and spied an excavation, where a homeowner was replacing some water lines and renewing a driveway. Naturally, I sidled over and took the rare chance to look beneath the skin of Oakland’s Pleistocene fan. The material was massive—unbedded—and clean. I pried off this little piece . . .

. . . and nibbled on it. It was firm, but crumbled like Necco wafers and turned creamy on the tongue with just a hint of grit. Not sticky or chewy with clay. Not indurated like hardpan. No sand or pebbles to be seen. The more I thought about it, the more peculiar this sediment seemed, until I had a wild surmise.

Alluvial sediment is never very well sorted, because it’s carried short distances and laid down by streams. Longridge Road is, as the name suggests, a ridge road running up the crest of a ridge between parallel stream valleys along Trestle Glen and Mandana roads. The crest of a ridge should not be made of this fine silt. But it’s downwind from downtown, which is Pleistocene sand dunes (the Merritt Sand), cousin to the dunes of San Francisco. Dune sand is very fine sand, and the fraction that blows away from the sand is finer still. So my wild surmise is that the fan, at least this part of it, is dusted with a layer of windblown glacial silt—i.e., loess. It’s remarkable stuff, and something I never expected to see in Oakland.

Pebbles and perils

I was writing a post on Pebble Beach for the KQED Quest site. The pebbles there are special because they represent a huge variety of source rocks, pieces of which ended up offshore in deep-sea rocks back in the Cretaceous. Those rocks were pushed up above the sea and eroded again, freeing the pebbles for several more rounds of polishing and recycling. Then they were sifted in the surf to isolate them in a pure deposit.

Oakland wasn’t lucky that way. The sediments here derive mostly from finer-grained rocks, and the big exception, the Oakland Conglomerate, didn’t include such a variety of gravel clasts. And even then, our sediments don’t seem to have enjoyed a vigorous winnowing and polishing in the Pacific waves. Rather than shiny pebbles, our shores are mostly clay and mud.

But not entirely. The Franciscan block that underlies Piedmont and neighboring parts of Oakland contains the grab-bag of seafloor rocks typical of melange, and the debris it has shed down Oakland’s creeks has made it to the bay. So have bits of the basalt in the high hills. One place that these pebbles appear is in a little spot along the shore of Lake Merritt.

Unfortunately the waves of Lake Merritt will never turn them into a dazzling display. However, neither will Oakland ever be ground into bits like the retreating San Mateo coastline. Our dwellings will never fall down the eroding coastal bluffs like they do in Daly City. I can live with that.

Bird islands

Lake Merritt is formally a wildlife sanctuary, declared in 1870, but the land itself is artificial and needs maintenance.

The Parks and Recreation Department website says that the first bird island was built in 1925 and the other four were added in 1956. As long as I can recall (since 1989) they have been a tangle of thick foliage and tall snags, but right now the islands are undergoing a makeover. Anyone have more information?

Sinking and rising

Sometimes the changes we can deduce are simple. In geology, not always so. If you visit Jack London Square, you shouldn’t miss Heinold’s First and Last Chance Saloon:

The building and its floor are canted, and there’s a step down as you enter. The tilt adds a certain funhouse spice to the smoke-dimmed fixtures and memorabilia. What happened here is that the bar was set on landfill, the kind of early landfill done by Oakland’s first developers using harbor dredgings and other waste. Horse and hands and probably some steam powered the work, and little of that hard effort could be wasted on tamping the muck down to be worthy of the ages. So, imperfectly compacted, the “made land” settled for many years. At the same time, layer after layer of new material was laid around the tipsy little landmark, and now it’s the sunken treasure we enjoy today.

Did the building sink or the land rise? Yes.

Parts of San Francisco have gone through the same history, well south of Market around 10th AvenueStreet. Old sinking marshland, topped with layer after layer of fill added to keep the streets draining properly, have left century-old homes almost half a story below street grade.

On the California coast, much of the land is gradually rising while, over geologic time, the sea rises and falls. The dance of land and sea sometimes enables the sea to cut deeply into the coast, creating wave-cut platforms that perch above the beaches today. In Oakland that sort of topography is either obscured or nonexistent, most likely because the bay shore has never been exposed to Pacific surf.