Archive for the ‘oakland geology walks’ Category

The Pill Hill/Fairmount ridge walk (#20)

29 December 2011

This hills-and-paths walk is number 20, “Broadway and Oak Glen Park,” in Charles Fleming’s Secret Stairs East Bay. This is not a bedrock walk, like the previous ones I’ve featured, but a landform walk. Let’s start this time with the topography.

walk 20 topo

This walk starts in the bayside flats, crosses two hills and two streams, and returns from the side of a third hill. The first hill is Pill Hill, and the second (Fairmount ridge is my name for it) and third are lobes of the Adams Point upland. These are parts of a larger structure that is central to Oakland’s character, an ancient Pleistocene alluvial fan. Here it is, marked “Qpaf” on the geologic map.

walk 20 geologic map

This walk takes in the leftmost edge of the fan, crossing two valleys of the Glen Echo Creek system which dissect the fan. The creek feeds the narrow west arm of Lake Merritt.

All right, here’s the route with the locations of the following photos.

walk 20 route

Here’s the view up Hawthorne Avenue to the edge of Pill Hill. The land west of the fan is a modern alluvial flat with almost no topography to it beyond subtle levees along the modern Temescal Creek and the notorious filled-in marsh that once underlay the ill-fated Cypress Structure in West Oakland. The Pleistocene fan has fairly abrupt edges like this all around it.

pill hill

As you go over Pill Hill and Summit Road on its spine, take a close look at the topography ahead of you. The near ridge is Fairmount ridge, made of Pleistocene alluvium, and the distant hills are Cretaceous and Tertiary sedimentary rocks. The eminence at the foot of the high hills is the older Franciscan block that underlies Piedmont and upper Rockridge.

pill hill view

The walk goes down into the valley of Glen Echo Creek. Brook Street is named for the Broadway branch of the creek, which is culverted under Mosswood Park and runs open to the sky in the backyards here. This shot is at the foot of 30th Street.

glen echo creek

If you go upstream a little ways you can spot the culvert where the two branches join.

glen echo creek

Next we climb the other side of the valley up a long flight of stairs, then turn right and follow the ridge top, along Fairmount Avenue, for a ways. A detour of stairways leads to Hamilton Place, at the toe of the ridge (the new Whole Foods place cut into that toe; unfortunately I never got a good look at the cut). From here we look across the next valley, which I might as well call Harrison valley.

harrison valley view

This valley has a well-developed profile, but apparently it never had a permanent creek. The Oakland watershed map shows only a culvert here. Anyway, we walk up the far side of this valley and return west on classic Perkins Way, where we can look back at the other two ridges.

perkins way

Back up on Fairmount ridge, we stroll up quiet Kempton Avenue, where this nice driveway wall of California mariposite lives.

mariposite

Soon enough we find ourselves again at the steep edge of Glen Echo Creek valley. If you limit yourself to walking, Oakland is really quite a rugged place.

kempton avenue stairs

At the bottom is a precious remnant of early Oakland’s streambeds, Glen Oak Park. An old concrete bridge crosses the stream, and if you have time to stroll up and downstream there are some fine buildings here too.

glen echo creek

I would be remiss not to mention that a little farther, at the foot of Piedmont Avenue, is a good sushi place, Drunken Fish.

The Albany Hill walk (#35)

13 November 2011

Here’s another stairs-and-paths walk from Charles Fleming’s Secret Stairs East Bay covering Albany Hill, the “little hill” for which the city of El Cerrito is named. I covered its geology last month for KQED Quest Science Blogs, so this post is more about the details of what you’ll see as you take walk 35. Here’s the route map starting from the El Cerrito Plaza BART station. In the book, the route starts at San Pablo and Washington, but I have an extra path that’s not in the book. The numbers represent the photos in this post.

walk 35 route

Next is the topography . . .

walk 35 topo

. . . and here’s the geology.

walk 35 geologic map

The geology’s pretty simple: the hill itself is typical Franciscan sandstone of the Novato Quarry terrane, surrounded by Quaternary sediment shed from the Berkeley Hills. Cerrito Creek runs past its north end, and Marin Creek’s drainage lies to its south. The divide between them is a low ridge of older alluvium where Solano Avenue runs. This accident of topography, making Solano a ridge route, is a subtle but important part of that street’s charm (like Park Boulevard in Oakland).

We start to hit bedrock around the first set of steps—duh! That’s what makes the hill so steep. This set of steps, Catherine’s Walk, is the worst.

stairs
steps

Now it’s worth looking around as you proceed. First come views west over the Bay. Click this one for a 1000-pixel version: in the Bay, left to right, are the Albany Bulb, Brooks Island, Point Isabel and Point Richmond; across the Bay are the Golden Gate, Marin Headlands, Angel Island, Tiburon Peninsula and Mount Tam, each and all worthy geological outings.

bay view

Once you enter Albany Hill Park the bedrock starts to emerge more. The real opportunity to inspect and sample it comes later, though.

bedrock

The trail winds up the crest of the hill through eucalyptus woods, for a special experience. The people who planted these didn’t have anyone’s pleasure in mind: they were dynamite-makers who needed a fast-growing screen to help muffle explosions. (The same thing happened up at Point Pinole.)

eucalyptus

Up here you start getting views to the east. The rocks in the Berkeley/Oakland Hills are much younger than where we stand: about 10 million years old as compared to the 80-ish million years of the Franciscan here.

berkeley hills

At the park’s north end we hit the top of Taft Avenue and take it down the east side of the hill. Don’t miss the view south. Behind the downtown Oakland skyline is Black Mountain, south of Palo Alto.

oakland

Along Taft is a long roadcut where you can poke and bang the bedrock to your heart’s content. Unfortunately it’s pretty featureless sandstone. It points to a geographic setting, long ago, when huge quantities of fresh sand were being generated and carried offshore to waiting basins, perhaps at the bottom of submarine canyons like today’s Monterey Canyon.

roadcut

Now if you scrap the last part of the route given in the book, and instead stroll north on Adams Street to its end, you’ll find a cute little path running along Cerrito Creek back to San Pablo.

creek path

Albany Hill and Cerrito Creek have a history of neglectful exploitation, but they have allies today in the Friends of Five Creeks.

The Berkeley panhandle walk (#1)

19 September 2011

Here’s another stairs-and-paths walk from Charles Fleming’s Secret Stairs East Bay, one that he calls “Claremont: The Uplands” but I will call the Berkeley panhandle. It feature’s Berkeley’s share of the Piedmont block of Franciscan melange. Here’s the route map, showing the locations of the photos.

walk #1 route

The terrain consists of steep-sided hills, naturally, which is why there are stairways. On the south they overlook the flat-floored valley of Temescal Creek; on the west is Harwood or Claremont Creek, and on the east is the eroded swale along the Hayward fault, the approximate location of which I’ve marked with the big dashed line.

walk #1 terrain

This time I’ll throw in the geology too, since the panhandle is faded out in my master Oakland geology map.

walk #1 geology

KJfm is Cretaceous-Jurassic (age) Franciscan melange; the red blobs are notable chert outcrops, and I assume the teeny blue one is serpentinite. The gold is alluvial fan material. The curving black dashed line is the inferred fault at the edge of the Piedmont block with the teeth on the upthrown side. OK!

The gates of The Uplands were designed by John Galen Howard of local chert. Berkeley’s architects at the turn of the last century were enamored of the local rocks.

claremont gates

Eucalyptus Road winds around the rim of a promontory, and down at its tip is a big chert knocker, the one on the map.

eucalyptus knocker

But the area is also full of landscaping and building stone. The basalt of this home may have come from the Sibley quarry, but there are other sources of stone like this too.

dark stone house

Some of the nondescript melange crops out at the foot of South Crossways/the head of Roslyn Court; take a look around when you’re there.

roslyn court

A more extensive exposure appears where you enter Roanoke Road. Melange is mostly sandstone or shale that vegetation tends to like, so you don’t see it much.

roanoke melange

Now we go way up on the ridge, Berekeley’s counterpart to the highlands of uppermost Broadway Terrace. It’s much smaller, greener, and more exclusive, probably a lot like the Oakland neighborhood looked like before the fire. This structure, Fleming points out, is brick from the brickworks at Port Costa, including the decorative clinker bricks. I love this stuff.

port costa brick

Do look around, not just downward and outward but upward.

oak and home

The walk leads off the ridge and down to Claremont/Harwood Creek, on its way from Claremont Canyon to join Temescal Creek under the freeway near the BART station.

claremont creek

It’s a privilege to have living water in a neighborhood. Last comes this baroque grotto/pool thing in a front yard that was assembled of serpentine chunks much like Elks Peak.

serpentine extravaganza

Remember, all this is in addition to some grand and gracious homes surrounded by luscious landscaping. Those are Fleming’s main focus; my thing about rocks and stuff is a mere ancillary obsession.

Glenview walk (#23)

8 September 2011

This is another path-and-stairways walk from Charles Fleming’s book Secret Stairs East Bay; his description of the homes and streets is good, but I’m here to talk about the geology you’ll see en route.

The walk starts on Park Boulevard, which is one of Oakland’s premier ridge routes, maybe its best. On its north is Indian Gulch, later known as Trestle Glen, and on its south is Dimond Canyon. Trestle Glen Creek is now culverted, although its waters still run free upstream in Piedmont. Dimond Canyon and points downstream, of course, feature Sausal Creek. The whole idea of Glenview the neighborhood is that from Park Boulevard you could overlook glens—secluded wooded stream valleys—on either side. (Such honesty in marketing may seem quaint today.) The walk route (created using gmap-pedometer) traverses stairs and pathways on the Trestle Glen side:

walk 23 route

Here’s the topography, courtesy Google Maps, with the photo stops marked as well as the bedrock line between the Piedmont block and the Pleistocene alluvial fan at Oakland’s heart. See the Oakland geologic map for context.

walk 23 map

The walk begins on Park Boulevard, going up the gentle slope of the remnant fan. I would love to see what’s beneath these homes, but how likely is that?

park boulevard

As you rise, the hills emerge as does the occasional vista. The Glenview really is the everything-view.

temple vista

At this point the walk leaves the spine of the fan and wanders the slopes and floor of Indian Gulch. The mature palms and lush vegetation combine with steep slopes (though not the insane slopes of the high hills) for a distinctive charm.

steep streets

Again, watch where the trees allow a peep through. Homeowners with their upper stories are privileged over streetwalkers in this respect.

downtown harbor view

On Elbert Street, a patch of rustic funk, emerges bedrock—just a prosaic Franciscan sandstone here. Perhaps more crops out along the power line through this neighborhood, but I was here to follow instructions and did not check.

bedrock

The walk delivers us to the floor of Indian Gulch, long since vacated by its namesake indigenes, converted from a park (with trestle) and turned into a classic upper-middle-class residential district. The narrow road and steep-walled valley give it a uniquely intimate feel. Farther up the valley, what looks like real woods is just the hinterland of what appears to be Piedmont’s largest private lot.

trestle glen

The walk leaves the valley floor at the foot of Barrows Road. Higher up you begin to glimpse the high hills again above the densely settled slopes.

glen slopes

It appears to me that the bedrock portion of the stream valley is a bit steeper than the alluvial-fan part, but not by much. The transition between them is quite subtle. The fan sediments are well compacted and bound with firm clay.

Hayes Creek – Dracena Park walk (#34)

10 August 2011

Last week I bought a copy of Secret Stairs East Bay, by Charles Fleming, and met the author in person at a book event at the Solano Street branch of Pegasus. As I leafed through the book and heard the author, it was clear that while the walks offer lots of insight into Oakland’s history and culture, the geologic stories to be seen on these walks were yet to be told. I thought, Well, I can try that.

Sunday my wife and I took one of the walks, number 34, to Dracena Park (featured here before) in Piedmont. It begins at Chapel of the Chimes on Piedmont Avenue and takes you on a pathway across the valley of upper Glen Echo Creek (which I’ve called Mountain View Valley). Here’s the view back toward the Chapel from the other end.

glen echo creek valley

The stream was culverted long ago, but on the 1897 topo map it’s shown as Hayes Creek. Today it’s Glen Echo Creek. The valley floor is so flat because it was graded and planted to houses. But in my unprofessional opinion, its flood hazard today is as low as anywhere.

Onward! The book directs us to the head of this little gorge, part of Pleasant Valley Creek’s watershed, and thence to the old quarry pit now known as Dracena Park.

pleasant valley creek

You should always suspect humans as a land-shaping agent in Oakland, and indeed Walter Blair, who ran the quarry and before that a dairy at this site, may have had a flume or a transport line of some sort here. But its original form appears to be intact.

We turn into the park proper, and glorious bedrock appears—Franciscan sandstone, ready-fractured for its purpose.

sandstone

Go ahead and inspect the stuff; no hammer is needed (and none allowed anyway) when it crumbles so readily. Fracturing and tectonic movements—and surely some seismic work, like a bartender’s cocktail shaker—has rubbed and even polished parts of the stone.

hand specimen

Fleming says that the stone went into the homes of Oakland, but that is not true. This is not dimension stone by any means, but rather the usual quarry of Bay Area stone hunters in general: crushed stone and aggregate for roadbeds, underlayments and concrete mixes.

What was once a noisy scene of dynamite and dust is now a green bowl punctuated by the cries of children.

dracena bowl

The walls of the park are pretty well greened over, but watch out anyway: bedrock exposures are not forever. Maybe in a marble or granite quarry, where solid rock is sawed away in blocks, but here rockfall is a continuing potential hazard.

rockfall

These are not decorative boulders emplaced by landscape designers, but fallen rock. And that ivy-covered fence at the left? It’s really a safety measure to keep landslides away from picnickers. Here’s the whole thing.

slide guard

Dracena Park is a worthy way to remake an old quarry. But if you’re here when an earthquake strikes, get away from the walls.


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