Archive for the ‘oakland soil’ Category

Rejuvenation

12 December 2008

big daddy garden

Big Daddy’s Complete Rejuvenating Community Garden sits astride the Emeryville line just north of 580 on Peralta Street at Macarthur. It’s a nice spot to look at the harmony between Oakland’s land and its history. There are the hills; here are the works of the city; beneath all is the same old soil, ready to bloom for us under the care and energy of visionaries.


big daddy

Reclaiming dead land is the same work as reclaiming dead metal—making waste into wealth. There are many lessons and a lot of pleasure to be had at this urban garden. Click both photos for larger versions.

I probably will not blog here next week while the big annual meeting of the American Geophysical Union goes on across the bay. Look for activity on my About.com blog

Soil creep

12 November 2008

soil creep

I was up in Redwood Park this morning looking for this. Not the woods or the sun or the fine cool air, lightly scented with fall leaves. A textbook publisher wanted a photo of bent trees like these, which curve because they grew on a creeping slope. The sandstones across the Oakland hills weather into clean, fine sand that doesn’t have much strength. Thus the slopes in the redwood groves are as steep as a sandpile. Redwoods favor the sandstone because it retains moisture, and they seem to be fine with the angle of slope. But other trees root themselves differently, helpless against the very slow, steady earth movement called soil creep, and saplings may have to correct their stance as the ground shifts.

If compression across the Hayward fault didn’t keep pushing the hills up, they wouldn’t have these intimidating slopes but would soften into something more like the hills of Moraga.

The valley here is precious for being the habitat of the rainbow trout’s type population, the community of fish from which the species was first officially described. That doesn’t mean that the trout here are higher in genetic diversity, or bigger, or more special in any way except their fortuitous encounter with a biologist. But the park is taking good steps to safeguard the stream anyway, and I am so proud of East Bay voters for continuing to ensure funds for the regional park system. Developers take care of themselves; utilities and municipalities do too. Only the people, united, can take care of their common lands.

Sheffield soil

3 September 2008

soil profile

At the end of Covington Street, in the Sheffield Village neighborhood, you’ll find a little parking area and a public access to the Dunsmuir Ridge Open Space. (It’s also the back entrance to the Dunsmuir House property.) Take the dirt road up the hill and you’ll pass this textbook exposure of the soil profile: dark topsoil on top, pale subsoil beneath. But keep going; this is one of Oakland’s most secluded public spaces. Sheffield Village is one of Oakland’s prettiest neighborhoods, all built in the late 1930s except for the higher houses on upper Revere Avenue, above the Hayward fault.

Adams Point alluvium

15 July 2008

adams point

Adams Point isn’t really named Adams Point—the name refers to the neighborhood overlooking Lake Merritt from the north. (And it’s named for Edson Adams, who once owned it all.) But I like to think of the low peninsula of Lakeside Park, between the lake’s two arms, as being Adams Point proper. One day in early 2003 I strolled along the water at its base, looking for outcrops. It appears to be the only spot on the entire Oakland shoreline that is nearly in its original condition.

The rocks in this view are not original; they’re pieces of the old wall that lines the rest of the lake. And the large boulder is a decorative one that fell or was pushed down here from the park lawn up above. What truly belongs here is the sand and gravel, which makes up the lake shore and the hills around it, Haddon Hill on the east and Adams Point hill on the north. Both are part of a large alluvial fan of Pleistocene age.

Under the roots of a tree, I found the original sediments exposed:

adams point

This being a city park, I left the material untouched, but the pebbles of local red chert and bluish basalt are unmistakable. These particles eroded from the hills and were carried here by vigorous streamflow, which also rounded their sharp corners somewhat. Outside of building excavations, exposures of this material are rare in Oakland.

Firm clay

13 April 2008

clay

On two occasions I’ve spotted construction sites on the fringes of Haddon Hill, once at the corner of MacArthur Boulevard and Wesley Avenue and once at the west end of Brookwood Road. I asked what the ground was, and both times the owners said the same thing: “firm clay.” There is no bedrock to speak of west of the Hayward fault, outside the Piedmont block and Toler Heights, up where 98th Avenue ends. It is safe to say that any Oakland neighborhood named “Heights” or “Highlands” has some bedrock under it, and some of the “-monts” do. But the rest of the hilly places that adjoin the flats are firm clay, with maybe a little sand and gravel. If the slope isn’t too steep, this soil is good for building.

All are part of a large alluvial fan dating from late Pleistocene times. It stretches from Pill Hill to Evergreen Cemetery, and its closest approach to the Bay is here at San Antonio Park, overlooking Coast Guard Island.

san antonio

Its sediments are said to contain “extinct late Pleistocene vertebrate fossils.” I haven’t read the literature, but that could mean anything from Ice Age mice to the mammoths, horses, camels, sloths and bison known from other Bay area sites, not to mention some extinct great cats. It’s worth keeping an eye on this stuff.

Montgomery Ridge

16 March 2008

bowlofchert.jpg

St. Mary’s Cemetery, north of Mountain View Cemetery, is on a ridge that runs toward the bay and peters out at the Kaiser hospital on Macarthur and Broadway. The ridge is on bedrock at the high end and changes to old alluvial fan sediment just past Pleasant Valley Boulevard. I call it Montgomery Ridge because Montgomery Street runs approximately up its crest. My yard lies on the edge of this ridge down near its end. I find these Franciscan chert cobbles scattered thinly in the dirt, and I’ve been putting them aside. They are rough, but not jagged, so I take them to be natural, in-situ alluvium rather than fill or crushed rock. That’s where things stood until the other week, when I found a cutbank on upper Howe Street dug into the ridge, and the same chert was tumbling out of the hillside from a layer just beneath the topsoil. Walking down Montgomery, I saw more chert chunks in the soil by the road at the corner of John Street. My favorite pieces are the greenish ones, like this one by the side of upper Howe Street.

howegreenchert.jpg

This chert comes from the Piedmont block, but the geography is different today. Today, streams have incised the old fan and they’re too feeble to carry this kind of material. I picture much drier conditions, and flash floods strewing the chert across the surface of the ancient fan. The next thing is to see where else it occurs. Let me know if you find it in your neighborhood.

The 9th Avenue palms

4 February 2008

9thavepalms.jpg

This row of palms has a history, but I don’t know it yet. The Oakland Heritage Alliance has a guided walk through this area, which was part of the Francis “Borax” Smith estate. Smith made his fortune developing the borax industry in the playas of Nevada and the Mojave, and nothing spoke success in turn-of-the-century California like an allee of palms. (Click it for an 800×500 version)

The ground here is a large, dissected alluvial fan that spans much of central Oakland. Pill Hill marks its west end, the rise of Evergreen Cemetery the east end. Foothill Boulevard runs along its base. The soil is a firm silt of excellent quality for building or growing. Many of the stream valleys that dissect it are now major streets: Park Boulevard, 14th and 23d Avenues, Fruitvale Avenue, High Street, Seminary Avenue.

These palms are widely visible around Oakland, if you know where to look. Yesterday I spotted them from the Kaiser Hospital parking structure; they’re also easily seen from upper Mountain View Cemetery and the Chetwood Street bridge over I-580. Other sighting reports are welcome.


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