Archive for the ‘oakland geology views’ Category

Gudde Ridge

19 February 2012

The basalt of the Moraga Formation is spectacularly exposed on both sides of Route 24 east of the Caldecott Tunnel. From along the highway you can get an excellent view of its makeup and structure, but this view from Radio Tower Hill shows how the rock unit makes up Gudde Ridge.

gudde ridge

Click the photo for the 1000-pixel verson. Gudde Ridge runs just east of Round Top all the way down to Canyon Road, on the back side of Moraga. The town of Canyon is on its west flank. And it’s Moraga basalt the whole way. In this photo you can see the underlying Orinda Formation to the right of the basalt. It’s gray conglomerate as opposed to the red-brown basalt.

Home from afar

5 February 2012

A few weeks ago I paid a visit to distant Mount Vaca, north of Fairfield on the Solano-Napa County line. It’s almost 3000 feet up and commands a wide view. Naturally I looked back at the Oakland Hills. There they were, immediately recognizable.

view from Blue Ridge

Click the photo for a 950-pixel version. In the upper center is Round Top, with Redwood Peak to the left and Vollmer, then Grizzly Peak to the right. Behind them is San Bruno Mountain across the bay. On the left edge are the plumes from the Avon refinery near Martinez and a bit of the Delta. The entire vista is part of the plate boundary, cut into slivers by the strands of the San Andreas fault system. At geological speed, they are all moving rightward at various rates measured in millimeters per year.

I’m working on my talk for the Oakland Heritage Alliance, this Thursday at 7:00. The process is forcing me back away from the details and toward the big picture—not the geological big picture, but the picture nongeologists see. That means I talk less about plate boundaries and more about how to live on our particular one.

Radio Tower Hill

20 January 2012

On Tuesday the skies were so clear I made a point of visiting the hills. Not as clear as Monday, but from the top of Radio Tower Hill this is how the Golden Gate looked. Remember this when the weather is dismal.

golden gate from radio tower hill

Click the photo for a 1000-pixel version. That’s the Farallon Islands on the horizon, perched at the edge of the continental shelf on the Pacific plate. They consist of the same granite found on Point Reyes, Bodega Head, Montara Mountain and points south in the Salinian terrane. The blob just below them is a freighter bound for the Port of Oakland, or perhaps a tanker bound for Point Richmond. Downward in the image is the bridge, Alcatraz Island, Treasure Island and the foot of Ashby Avenue in Berkeley.

Radio Tower Hill doesn’t really have a name. It’s the hill at the intersection of Grizzly Peak Boulevard and Marlborough Terrace. It’s made of Claremont chert.

The view from Panoramic ridge

14 December 2011

I’ve posted three other shots from the walk I took in late May to the ridge at the top of Oakland’s own Panoramic Way, overlooking Claremont Canyon. This is the view south over the rest of Oakland; click it for the 1000-pixel version.

Claremont ridge view

The homes in front are in the Grandview neighborhood, and behind them are the tight ranks of Hiller Highlands. The dark notch beyond is where the Hayward fault runs. On the right side we have Broadway Terrace, the blond summer sward above the top of Mountain View Cemetery, and beyond them San Leandro Bay and the airport on the peninsula known as Bay Farm Island.

Every year this hill repeats this season. I must return here, too.

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.

Radio Beach

8 November 2011

Radio Beach is Oakland’s nearest thing to a natural beach. It’s city land, on the north side of the Bay Bridge approach past the toll plaza. There is no lonelier or prettier spot on Oakland’s waterfront. This is the view toward the bridge as you enter the beach.

radio beach

This was near low tide yesterday, and the mudflats stretching all the way to Emeryville were tempting. Here’s the view back from the other end, with some of the radio towers.

radio beach

And here’s the view out, with Mount Tamalpais, Angel Island and the Tiburon Peninsula on the skyline. Click the image for a 1000 pixel version.

radio beach

The sand is very fine grained, given the energy of the waves and the available sediment in the Bay. It collects here where a little extra wave energy gets focused, against the buttress of the bridge approach. Not a super beach, but a real one.

Upper Claremont Canyon

6 October 2011

I’ve been busy, and October is the climax of the business. But I have a fond memory of May 26, when I hiked up to and past the end of Panoramic Way into the open lands of the Claremont Canyon Regional Preserve. The ground here is mapped as undifferentiated sedimentary rocks of the Great Valley Complex. Because the map doesn’t give it a name, I name it Panoramic ridge. This is the view east. Click the photo for a 1000-pixel version.

claremont canyon

I wonder about the pattern of the ridges that jut west from the ridgeline, but that’s an intellectual task for another time. For now my main thought is, We live in such a beautiful area.

I’ll be out of town for much of the month, so don’t expect a lot of new posts for a while.


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