There doesn’t seem to be a reason for such a flat stretch on an ordinary alluvial fan. Fans slope; that’s why they’re fans. I have to assume that the ground was not excavated flat but is naturally that way. Is it possible that this is a relict wave-cut platform, similar to the Clinton marine terrace but higher and older?

Arguing against that hypothesis, the height is problematic. On the other hand, the East Bay hills are rising and so may be the land west of the Hayward fault. It may be rising in fits and starts (meaning in episodes measured in thousands of years). The next thing I want, and have wanted for a long time, is a really accurate terrain map of Oakland. It would look like the standard digital elevation model of Oakland but would be compiled from lidar data and be accurate to a centimeter or so. Maybe my eyes are fooling me; after all the street does slope a little.

The Hayward fault is mapped running through here from about third base on the ballfield at the left across the field of view. Two trenches were dug across the fault right here in 1981, and Jim Lienkaemper, the US Geological Survey’s (therefore the world’s) leading expert on active faults in Northern California, found evidence that the 1868 earthquake ruptured the fault here. Here’s part of the map he published in 1992 showing this area (at the REN in WARREN).

The map is oriented so the fault runs vertically. The codes refer to evidence of active creep (C2) and vaguer evidence of creep (C3), geomorphic features of greater and lesser distinctness (G2, G3), and the trenches (T) I mentioned. “H2″ means there was good evidence of fault motion in the last 12,000 years—in this case, historic motion. The little oval at the WA in WARREN is a sag basin, now a water feature in the park. From top to bottom, the two-letter codes are as follows: gi, gradual inflection in slope; rw, right-offset wall; sl, linear scarp; jo, opened joints or cracks in concrete; sc, scissor point (where the up and down sides switch); rb, racking/distortion of building; as, arcuate scarp; dr, depression in a right stepover (sag basin); rc, right-offset curb; so, surveyed offset feature. The other codes refer to specific publications. This level of detail is available for the entire length of the fault, and while the USGS considers its online database of 2008 to be the most current, I like the format of this older map, Miscellaneous Field Studies Map MF-2196

Leona Canyon Regional Open Space Reserve is an East Bay Regional Parks District property of some 290 acres that is entirely within the Oakland city boundary. It’s got rocks.

The canyon was cut by Rifle Range Branch, part of the Arroyo Viejo stream network. The branch joins Arroyo Viejo underneath I-580 at the turnoff to the zoo. The topography is rugged. I surmise that the rifle range that gave its name to the creek was here once upon a time, because it’s the sort of place where you could shoot a lot without disturbing the rest of the city.

Here’s the geology of the same piece of ground.

The pink “Jsv” is the same metavolcanic rock (Leona “rhyolite”) found in the Leona Quarry just to the west. The green units are the familiar sedimentary rocks of the Great Valley Sequence, tilted upward so that they get younger to the east. The units, in order of age, are the Knoxville Formation (KJk), the Joaquin Miller Formation (Kjm), the Oakland Conglomerate (Ko) and the Shephard Creek Formation (Ksc). You can see that the canyon is controlled by the faulted contact between pink and green.

OK! The creek is dammed at the base of the canyon, presumably just for flood or sediment control. Maybe the rifle range used to be here. Anyway, the creek is fairly level throughout the park, creating a nice bit of habitat.

As you walk up the creek, it wanders along the contact between the two major rock units, so you’ll see a mixture of boulders in the creek bed. The Knoxville is a shale with some sandstone, not very distinguished, but near its base it includes some conglomerate and breccia: rocks made of pebbles and cobbles derived from the Leona keratophyre. This example is from the high end of the trail, in the upper left corner of the geologic map.

The reserve has two paths that lead up the canyon’s sides. The Pyrite Trail goes west through the metavolcanics. It’s shady and steep. I should note that I saw no signs of pyrite on it.

Along this trail you’ll see the Leona metavolcanics, kinda ragged-looking stuff that’s been chewed up and spit out a few times since it was a volcanic island arc during the Late Jurassic.

There are nice views of the other side of the canyon, which is more open and chaparral-y.

The trail up that side is called the Artemisia Trail. I’m not sure that either trail’s name means much. It passes a lot of this fine-grained sandstone.

Higher up, you get a good look at this big knob, which is a prominent part of the hills’ skyline as seen from the north. This view is from the south.

There seem to be a few informal trails on it, and the view must be fantastic. But the Artemisia Trail offers superb views across the middle and south bay, too. I’ll be back.

This is where the low end of San Leandro Creek, between Hegenberger and the Nimitz, goes through some significant transitions. Here’s the Google Maps view, followed by the geologic map. The photo above is from the corner of Leet Drive at Hegenberger.

The pink area is artificial fill. “Qhb” stands for young basin deposits, which is the zone of sediment at the very bottom of the San Leandro alluvial fan just before you hit bay mud. The darker yellow bit at the top is a belt of levee deposits, where the creek once flowed perhaps thousands of years ago. The alluvial fan has a half-dozen of these splaying out from Lake Chabot, from Elmhurst Creek on the north down to southern San Leandro.

(By the way, the topographic base of this geologic map is quite out of date. Do any of you remember the drive-in theater shown here where Kitty Lane is today? And when was Dag Hammarskjold School, so righteously named, ripped out and replaced with a public-storage joint?)

Looking south (upstream) from Hegenberger, the creek appears almost natural, with its floodplain close-hemmed by levees. At least, it has mud on the bottom and vegetation growing in it.

This stretch of the creek is fenced off and inaccessible. From 98th Avenue—more precisely, looking downstream from behind the Wendy’s at the head of Bigge Street—it looks even more bucolic.

Between these two points is the original Bay shoreline, a gentle transition from low grassland to high marsh that is almost totally gone from the Bay today. This part of the creek is the nearest it gets to being natural. Upstream from 98th the entire creek is walled in.

This last shot is from the spot where the power line crosses the creek; as usual the land beneath is an informal public park. A hole in the fence gives access to the creek, but the going looks tough, and besides the dogs here are numerous and excitable.

The creek forms the boundary between San Leandro and Oakland from here to the railroad tracks. From the tracks to 580, San Leandro spills well north of the creek because, like the village of Temescal, the city began as a town right on the creek.

That’s the Altenheim on the left, across I-580, and of course the LDS temple with Redwood Peak behind it.

The reservoir was built in 1910 by the People’s Water Company, which took the existing valley of a Sausal Creek tributary, hollowed out the top of its watershed and made an earthen dam. Later EBMUD assumed control of it and upgraded things considerably. However, landslides plagued the steep west bank of Sausal Creek directly east of the reservoir starting in the 1930s.

The latest set of slides, in 2006, led to a tangle of lawsuits initially aimed at EBMUD and blaming leakage from the reservoir. The lawsuits were consolidated and went to a jury trial in 2012, with Alameda County as the main defendant and the damaged land owners (two homeowners and a church) as the remaining plaintiffs. The jury found for the County. None of the media that announced the lawsuit bothered to report the outcome, and the City of Oakland hasn’t bothered to clear EBMUD’s name, but the jury dispensed justice as designed.

For 17 MB of geotechnical detail, see EBMUD’s Central Reservoir Seismic Final Report, issued in 2008. As far as engineers can tell, even the Big One on the Hayward fault won’t break the dam. But if I lived downstream, I’d keep a close eye on the dam after a truly major quake and be ready to relocate. And in the aftermath, that emergency water supply may save our lives.

This lot sits at the head of a stream valley at the edge of a regional park. The large expanse of impermeable pavement collects rainwater, and the terrace above it discharges more runoff in a large drainpipe. Ordinarily the ground would absorb most of the water and release it gradually, the way that trees are used to. Instead the flow that results here is strong enough to carry away a lot of gravel. Oh well, call in another truckload.

Turn around and track that water and gravel over the property line into the Regional Open Space. With the extra water, the stream is already cutting a deeper channel into its valley. As the years go by, the valley walls will slump into the stream and the trees will fall with them. A big wad of sediment now working its way downstream will clog the habitat below, smothering the bottomland and its ecosystem. Meanwhile the erosion of the stream valley will work its way headward. Eventually, within a lifetime, the spreading collapse will reach the edge of this large lot (and the neighbors’ lots) and whoever owns it will have an expensive problem. This pristine street may disappear from the map, like others before it in the Oakland hills.

I’m not giving a professional opinion here; it’s obvious to common sense. The landscape of the hills is fragile, but expert advice can make living there much more sustainable.

People have told me about and showed me pieces of fossil wood from the East Bay hills before. I’m no expert on the subject, and I haven’t done a lot of fossil hunting in Oakland. But we have young terrestrial rocks around here in addition to the abundant marine rocks—primarily the Orinda Formation, of Miocene age. I assume this came from there.

People have told me about fossil wood in Wildcat Canyon, but that’s regional park land where collecting is forbidden. This specimen, I was told, was from EBMUD land, where collecting is not expressly forbidden, although I assume that vertebrate fossils (animal bones) are protected. I have purchased an EBMUD permit and have been looking forward to using it for responsible geologizing.

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.

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.

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.