Geology of Alameda

Although these two distinctive cities are right next to each other and were settled at the same time, Alameda is a very different place from Oakland. One way to put it is that when you’re in Oakland, you see Oakland all around you. In Alameda, you see everything but Alameda around you.

And I like both of those things just fine. But in this post I’ll attempt to show the subtle ways Alameda reveals itself.

First a little history. The earliest map showing Alameda in any detail was Captain Beechey’s map of the San Francisco Bay, first published in 1833. Mainly a sailor-centric chart, it focused on the seaward edges of things. It shows Alameda as the peninsula it was until the 1890s, when the tidal canal was completed across its east end making it an island.

Two details are interesting. First, the map shows the seaward edge of the peninsula as an embankment rather than the typical marsh found around most of the Bay. A sandy bluff overlooked the beach and mudflats here. Second, the map used the same tree symbols as it used for the redwoods in the high Oakland hills, and not the round icons used for the encinal oak groves to the north, in West Oakland and downtown. Gary Lenhart, over at alamedainfo.com, suggests that this may mean there were redwoods here. I don’t buy that because the habitat is wrong and because I haven’t seen any mention of redwood groves along the shore, but the possibility is intriguing, especially since Friar Pedro Font, during the Anza expedition in 1776, also sketched the peninsula with a heavy forest (view west).

The 1857 Bache map doesn’t cover all of Alameda, but what it does show comports with the Beechey map in depicting a definite edge, not a marshy transition, between land and sea. This segment is from the west end; the Peralta Wharf was where Ballena Bay is today.

This map shows the entire peninsula forested with oaks and labeled “The Encinal,” which is how the first generation of Anglo occupiers knew it.

That’s all long past. The trees went early, turned into firewood and charcoal; the land was farmed, then subdivided for estates and divided again for homes. Underneath it all, the Alameda peninsula is a uniform body of windblown sand dating from glacial times, now surrounded by artificial landfill as seen in the geologic map. Nowhere is the elevation higher than 35 feet.

I should note an exception to that. Once upon a time the shellmound of Mound Street was the tallest thing in town, according to the monument in Lincoln Park. And here let me acknowledge that we live on Ohlone land, and that we don’t deserve the acceptance and welcome the tribes have granted us. Forgive us our trespasses.

Between the natural sand and the artificial fill are Alameda’s lagoons, the city’s most unexpected and hidden feature.

They’re hard to reach, mostly private land. In a few places you can see that the landward side is higher . . .

. . . and the Bay side is lower.

On Willow Street at Alameda Hospital, the transition is plain to see in the roadbed. This is the greatest topographical feature in the whole city.

The main body of the dunes is a very gentle dome, reaching just over 30 feet elevation along Central Avenue. It’s hard to catch in a photo, but charming to see in person. This is looking down Chestnut Street, on the north side of the dome, toward Round Top.

And in the other direction is the top of the dome, such as it is.

It just goes to show that, to a committed geologizer, every place has a there there.

3 Responses to “Geology of Alameda”

  1. Amelia Sue Marshall Says:

    WONDERFUL as always! Where did you get the info that Peralta’s wharf was at Ballena Bay? The standard Evanosky story is that Antonio Peralta’s was at the foot of 14th Avenue in Oakland, and the French abbatoir was nearby, at the location of the Burger King on E 12th Street. Vicente Peralta had one at the foot of Temescal Creek. I suppose Ygnacio had to have a wharf somewhere, presumably near San Leandro Creek. But any of los hermanos Peralta could have had more than one wharf, presumably.

  2. Andrew Alden Says:

    I just looked at the maps. The original coastline in the Bache map matches the edge of the sand in the geologic map. But “Peralta Wharf” on the Bache map could mean any number of things. Still, that’s what it says.

  3. Anthony Says:

    It’s a lot easier to see the gentle slopes in Alameda’s streets when it rains, because we use the roads for storm drainage. It’s especially easy to see in streets which haven’t been repaved since the drought, as the trees sent out roots horizontally which lifted the street pavement (and curbs and sidewalks, etc), creating little dams for the runoff.

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