Not long after I documented the tombstone at Mountain View Cemetery made of the extremely old Morton Gneiss, I spotted the same stone—four polished disks of it—flanking the entryway of a house in the Grandview neighborhood.
This stuff is certainly a gift to the world. And yet just today I bent down by someone’s fence to caress a boulder of our own red chert, equally striking in its own way.
Lately the city has been fixing up the walks along the waterfront, and they’re well worth a visit. This splendid boulder of slate isn’t on the newest part of the trail—it’s at the foot of Alice Street, just where the Jack London Waterfront leaves off and the Alice Street Mini-Park starts.
I don’t know where they get stones like this; they aren’t from Oakland or even from the Bay area. That’s OK.
Mountain View Cemetery is a fun place for geology. Not only are there the untouched hillsides and the knockers of local bedrock, but the monuments themselves are displays of fine stone from around the world. On my last visit, though, this one caught my eye.
It’s an example of the oldest stone in the United States, the Morton Gneiss from southwestern Minnesota. I mentioned it a few weeks ago in a KQED Quest Science Blogs post before finding this specimen. Touching it will put you in contact with something 3,524 million years old, more than three-fourths of the planet’s age.
Let me take this opportunity to plug Michael Colbruno’s blog about the people in the cemetery. He calls it “Lives of the Dead: Mountain View Cemetery in Oakland,” but I still think of it by its original (non-SEO-friendly) name “Mountain View People.”
Here’s a nice piece of stonework on upper Lakeshore Avenue.
It’s a pit lined with picturesque cobbles and rimmed with gray slate flagstones. A large slate boulder is mounted in the center, and a fountain trickles off a smaller slate stone over the boulder, cascading into the pit with a delightful sound. Thanks for the gift to passers-by.
I look at sidewalks more closely than most people. It has little to do with geology, though—it’s just part of my hobby. But sidewalks do have geological lessons in them. Consider this sidewalk on the north side of upper Broadway near Lake Temescal.
It has a series of light-colored wedges along the fence, on the uphill side. As you might guess, they reflect the pattern of the rainfall and its drainage. Fresh concrete is poured and then caressed with trowels as it begins to cure. This treatment pushes the larger particles of aggregate under the surface and creates a smooth finished surface composed of fine particles and cement. But the surface tends to weather off, partly because the surface is hard to keep moist for proper curing. The imperfectly cured material is prone to attack by rainwater, which is a mild acid. As rain and wind work into the surface, green things both microscopic and visible colonize the rough spots. These turn up the acid attack with exceptionally high CO2 levels similar to those in soils, along with humic acids produced by plant tissues. With time, the crisp white walkway turns rough, variegated—and beautiful, akin to natural stone.
Oakland is blessed with excellent stonework dating from the Depression-era Works Progress Administration or WPA. When the WPA got together with Park Superintendent William Mott to build Woodminster, in 1940, an experienced cadre of artisans built its elegant features with a sure hand.
I should know more about the stone, but I don’t. It’s very similar to the stone used at Lake Temescal and the East Bay Botanic Garden in Tilden Park. It likely came from the Leona Quarry.
While you’re there, be sure to admire the amphitheater’s Deco concrete. And keep your eye open for WPA concrete in Oakland’s sidewalks and gutters. I’ve seen WPA marks from 1939, 1940 and 1941. This investment in public works has endured for more than 70 years.
Even before I knew what it really was, this short pier at Middle Harbor Park stood out.
This is clearly not a typical groin or breakwater, something that is dumped into place, but a carefully laid work of drystone masonry. It feels absolutely solid to walk upon. And then there are the rocks in it, a rich assortment of large and pristine Bay area specimens. There are tuffs composed of volcanic pyroclastic flows,
colorfully metamorphosed volcanics,
slickensided serpentinites,
and other metamorphics whose colors could inspire a fabric maker.
Also sandstones and even a few ringers of Sierran granitic rocks, perhaps from the old quarries of the Rocklin area. But it’s not typical of a modern marine rockwork—those use stone trucked in from a single quarry to save money and control the quality.
An interpretive sign explains that it’s a replica of the old “training wall” on the north side of the shipping lane to Oakland Inner Harbor, where the signature gantries load and unload big freighters. Training walls are jetties designed to turn a shipping channel into a flume during ebb tide, keeping the bottom clear of mud. The walls were built around the 1880s, using shoreline quarries around the Bay and shipping the rock here by barge. That explains the unique variety and distinctive regionality of the material.
The north training wall was removed when the shipping lane was enlarged in 2001, but they saved some of the stones. Masons installed them over a core of rubble, and here they are. The south training wall remains in place.
