MapView: Not ready for Oakland (updated)

The U.S. Geological Survey’s programmers have made a nifty nationwide map server called MapView that lets you play with geologic maps from most of the country. Naturally I zoomed in on Oakland. I expected to see something like this when I looked at the Toler Heights area.

It’s kinda garish, but it’s from the USGS and as authoritative as these things can be. Instead, MapView shows me this:

It’s crisp, it’s suitable for colorblind readers, but it’s wildly different. It shows simpler divisions and more limited areas of bedrock. It shows the active trace of the Hayward fault running on the opposite side of the hill from where it actually moves. Then there are things I notice: the names of the rock units have an antique feel and very few faults are mapped. And what’s with the ludicrously small landslide (“Qls”) and serpentinite pod (“sp”) in the middle? Why such a mixture of vagueness and precision?

In fact, this is not a USGS map at all, but a map issued by the Dibblee Foundation. Dibblee is the late and distinguished Tom Dibblee (1911–2004), popularly considered “the greatest geologic mapper who ever lived.” I consider him one of the greatest reconnaissance geologic mappers ever because that was his M.O.: to take his Jeep out to various high spots in poorly mapped territory and sketch out the bedrocks in the landscape onto a map base, then do field-checking until it was ready to publish. His skills were more than just fieldwork; he knew the literature and the community too, both scientific and industrial. I don’t have the talent to question his talent.

But. If you download the map and look at its sources, you’ll see that it’s based on Dibblee’s fieldwork in 1963 and a short return visit in 1977, plus three “preliminary maps” issued by the USGS, one of them in 1967 and all of them superseded by the map I use, Russ Graymer’s USGS Map MF-2342 published in 2000. I can only infer that this map was based on Dibblee’s old field notes as edited, posthumously, by John Minch in his role as official map editor for the Dibblee Foundation. I don’t question his talent, either, but it would be a major undertaking to update this map, one that has not been done.

What’s a few years, you might ask; the rocks never change. Well, consider that this map misplaces the Hayward fault. How do I know? It ignores the experience of Jim Lienkaemper’s meticulous mapping, which checks out in the field wherever I’ve looked. This is from his 1992 compilation of the fault trace and the supporting evidence.

The Dibblee Foundation map is beautiful, but in this respect it is simply wrong. It didn’t go through the rigorous USGS review process; in fact I am confident that if it were submitted it would be rejected.

I’m going to ask the MapView people to reconsider using these maps in preference to USGS maps. For now I have to say that MapView is not curated to my standards.

UPDATE: The MapView administrator responded to me promptly and politely; I’ll excerpt his reply: “the point you raise has been a real concern . . . but [we] didn’t know the entire story nor had we been presented with a clear example of the problem, as you did in your blog. . . Our starting assumption is that newer maps supersede older mapping, and so unless there’s a compelling reason to not do so, we show the newer map. . . . The most effective way to improve upon what’s shown in MapView is for local and regional experts to weigh in with their opinion and experience, as you have done. I sincerely thank you for contacting us, and assure you that we’ll remove the Dibblee Foundation maps in all cases where there isn’t an older map of that scale that is ‘better’.” Translation: We pick maps by their release date and we won’t adjust that until someone squawks.

The other attractive feature of the Dibblee maps is that they’re standard 7.5-minute quadrangles, which makes things much easier for the MapView programmers. But ease of programming is not the same as usefulness.

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.

23rd Avenue valley

Between the stream valleys occcupied today by 14th Avenue (originally named Commerce Street) and Fruitvale Avenue (Sausal Creek) is a subtle little valley that once had its own little creek. Now 23rd Avenue runs up its former course, diverting the street from the grid so typical of the rest of the neighborhood. The creek is shown on the 1877 map entering the Bay where the Embarcadero Cove Marina sits today. There seems to have been a shellmound a little south of there.

This view is looking up Foothill Boulevard where it crosses the valley. This is at the top of the marine terrace and the foot of the Fan. You can pretty much always tell where the Fan starts by following Foothill. The geologic map shows the valley splitting here with a spur running due north for a few blocks, filled with young alluvium.

This is looking across the valley farther uphill, on E. 17th Street where Garfield Park is. The valley is a bit deeper here, and it continues to deepen as you go uphill.

At 23rd and 23rd the creek split, with its northern fork running where Highland Avenue is today. The main fork continued straight, along 23rd Avenue, and petered out by E. 30th Street right next to the Central Reservoir, which is in the Sausal Creek watershed. The stretch where the divide between the two watersheds is most pronounced is occupied by a street named, unsurprisingly, Grande Vista.

This creek is entirely covered today.

Sneak creek peek

Sausal Creek has escaped culverting in a large part of its course. Between Dimond Park and the freeway, it mostly runs through people’s back yards, but you can spot it looking downstream from MacArthur Boulevard across from Canon Avenue:

. . . and farther down, looking upstream from a spot at the intersection of Dimond Avenue and Montana Street.

It’s culverted from here all the way down to the end of Hickory Street, directly below the miserable house on McKillop Street. Maybe it’s safer to say that the creek is covered, because even this open stretch has walls hemming it in.

Smilodon californicus

If you’re at UC Berkeley with a little time to spare, go visit the Valley Life Sciences building and say hi to the sabertooth cat fossil there.

Smilodon californicus is our official state fossil. It got the honor from its abundance in the tar pits of Rancho La Brea down in Los Angeles. It turns out that they were suckers, walking into the tar to feed on animals already stuck there, then getting trapped themselves. They and the extinct dire wolf are the two most common species in the tar pits.

Presumably they lived in Oakland, but I don’t see any reference to local Smilodon fossils. One of the things on my to-do list is to visit the paleo people at UC Berkeley and learn more.

Dimond valley

Sausal Creek is responsible for digging a floodplain that is rather wide just upstream from I-580. Here’s the view across it from Montana Street at MacArthur.

The squat tower just to the left of the speed limit sign is at the foot of Lincoln Avenue, and it’s at the same elevation as where I’m standing. That’s how wide the valley is. Here’s another view looking right down MacArthur.

The first cross street is Canon Avenue, the next one is Dimond Avenue leading up to the park, and beyond is the Fruitvale Avenue crossing. Here’s how the geology is mapped.

You can see that the stream valley is wide because three streams coalesce here at the edge of the Piedmont bedrock block. Restricted upstream, they enter the big alluvial fan (Qpaf) and have room to move and easy material to erode. It is curious that Sausal Creek hugs the west side of the valley; I suspect that tectonic movements may account for that, but only a decade or so of careful satellite altitude monitoring can answer my suspicion.