Archive for the ‘oakland geology views’ Category

Landslides of Outlook hill

5 March 2015

I’ve been surveying the low hill between Mills College and Holy Redeemer College, home of the Millsmont and Eastmont Hills neighborhoods. Its western face has no bedrock, either on the geologic map or in my experience. Here’s the relevant portion of the geologic map.

outlookmap

Its crest is supposedly Jurassic basalt, which would be part of the Franciscan assemblage. But the Hayward fault runs right along its length, and I lean toward calling it a pressure ridge. Long story short, it is squeezed up, shattered, and oversteepened, and these make it prone to landslides. Here are some, starting with the notable example at the top of 64th Avenue. This is its toe . . .

64th-beunaventura-slide

. . . and this is the view from its head, at Delmont Avenue.

64-buena-slide-top

Another is above Outlook Avenue, south of 76th Avenue. As you walk along its base, you’ll see bits of concrete from the homes that once stood here.

outlook-76-slide

Above it, on Hillmont Drive, there is a gap in the houses that offers a nice view. I have no business saying whether a landslide is responsible.

outlook-76-slide-top

Between these two obvious slides are some fine hillsides. This one, below Simson Street, makes a lovely backdrop to the Eastmont mall and, it seems, a nice informal park for the residents.

simson-field

It isn’t really vacant—all of the lots that subdivide it are extremely long for some reason. I think that spaces like this, shared without fuss by the landowners around it, are very precious.

Grizzly Peak

20 December 2014

Grizzly Peak is the highest point in Oakland, at 1754 feet elevation (sources differ). As you approach it on Grizzly Peak Boulevard, it seems to loom quite high.

grizpeak1

That’s an illusion caused by the eucalyptus forest. As you get closer, you start to see through the trees.

grizpeak2

And from the bay side, the peak has a mohawk look because the trees are stripped off its northern half.

There’s a vague trail up the south side. Even in its true contours, Grizzly Peak is a steep little climb, and the thick layer of leaves is slippery. I’d rather the eucalyptus trees weren’t here, but they do offer a lovely privacy.

grizpeak3

And underfoot are rocks! The peak is mapped as the Moraga Formation, a set of lava flows from 9 to 10 million years old. This is the stuff connected to the volcano at Round Top.

grizpeak4

The top of the peak has a broadcasting tower of some sort, with a fenced-in support building at its foot. There used to be a lookout tower here, and a benchmark nearby attested to its elevation. Mount Diablo is almost exactly due east—not that you can see it through the damn eucalyptus.

You could walk up the access road instead. Either way, you can’t get any closer to the peak per se than this.

grizpeak5

That route offers nice views, and it takes you past a lot of broken rock, if you have your heart set on a specimen.

grizpeak6

Most of the rock is like this—weathered and fractured. There’s no easy way to tell what causes the strong layering, as this rock has been tilted almost vertical and then eroded by the fog, rain and earthquakes of the Berkeley Hills.

grizpeak7

It’s hard to expose unaltered bits. What’s there is a medium-gray, featureless stone that geologists typically call andesite until they can study it in the lab.

Grizzly Peak is not a place to stay long, but it seems that there are those who love it.

grizpeak8

Emeryville

9 October 2014

The little town of Emeryville has almost no geology that passers-by would recognize. On the geologic map it’s displayed as largely artificial land and coastal alluvium.

emeryvillemap

The only people who see these things are builders and the geological professionals who advise them with their foundations.

The point was made from scratch—the original shore was a straight line pretty much where the railroad is now. Out at the end it’s been prettied up into Marina Park, a simulacrum of a wooded meadow. I like it there.

e-ville-point

A seawall, made of typical Franciscan riprap, protects it from the mild surf that manages to get here through the Golden Gate.

marinapark

The park-y part of Marina Park offers great views of Berkeley and points north. This is a good place to test your knowledge of the geography: Can you point out Strawberry Canyon, for instance. The highest point in this picture is Grizzly Peak.

e-ville-sculpture

We aren’t making any more artificial land in the Bay area, thank goodness. For a while there, people were planning to fill the whole Bay in. The nice thing about artificial land is that we can feel free to decorate it, whether formally as here or informally as at the Albany Bulb.

Manzanita ridge

28 April 2014

The ridge traversed by Manzanita Drive is one of Oakland’s highest residential areas, higher than 1400 feet. It’s the home-studded rise in the Oakland skyline to the right of Round Top in the blog’s banner image. Here’s the topographic view, from Google Maps:

manz-ridge-topo

. . . and here’s the matching part of the geologic map:

manz-ridge-geo

The ridge crest is held up by the Claremont Chert (Tcc), while Skyline Boulevard and Arrowhead Drive, running parallel just to its south, go through the crumbly Sobrante Formation (Tsm). (The other formations are the Orinda Formation, Tor, and the unnamed Eocene sandstone of upper Shepard Canyon, Tes.) Here’s the chert exposed at the west end of Manzanita; it and the next two photos click bigger.

Click for 800-pixel version

The views are terrific. Here’s the view north over the Huckleberry saddle to the smaller ridge of Claremont Chert that Elverton Drive skirts.

Click for 1000-pixel version

The middle of Manzanita offers fine views of Round Top.

Click for 800-pixel version

And the other end of Manzanita, past the unexpected Hills Swim & Tennis Club, is another saddle at the top of Shephard Canyon where the road to Canyon and Moraga crosses the hills.

skyline-shep-pinehurst-saddle

More than anywhere else in Oakland, this is an island in the sky.

Fruitvale Station vista

24 March 2014

Sometimes the weather is clear enough, but just hazy enough, to reveal the details of the landscape for quite some distance. A week ago the view down the line from the Fruitvale BART station looked like this.

fruitvalestationview450

I know it’s a small image, so click on it for an annotated 1000-pixel version. Most of the view extends beyond Oakland city limits. The farthest peaks are in the Ohlone Wilderness east of San Jose, some 30 miles away. Once you become familiar with our skyline, it’s never boring.

Lower Colton

31 January 2014

You may think of Snake Road as the ridge road that climbs the crest between Thornhill and Shepherd canyons, but it’s really Colton Boulevard. For a quiet hike above Montclair with views, you want Colton. Its lower part runs north of Snake across ground underlain by the Redwood Canyon Formation. Here’s a roadside outcrop.

colton-Kr

I didn’t even notice the parallel fractures until I opened the photo at home. They probably represent a bit of extra cementation, thanks to a late pulse of fluids, but they may also be original bedding.

I mentioned views. If you loop around Mendoza and Mazuela Drives you can view some immaculate houses and grounds, but I like the big empty lot on Mazuela that overlooks Pinehaven canyon; click it for the bigger version.

mazuelaview450

Huckleberry saddle

18 November 2013

The entrance to Huckleberry Botanic Regional Preserve is at a low point in the spine of the Oakland Hills, where the steep eastern arm of Thornhill canyon has cut headward toward the equally steep canyon of San Leandro Creek. Both canyons are steep because the rock between them is the tough Claremont chert. The saddle between the two canyons provides good views to the west and east, and a little path (labeled Huckleberry Path on the map) leads north from the Huckleberry entrance, a private entrance to the preserve for the residents of Elverton Drive. That’s where I got these pictures, first looking southwest toward downtown:

elvrtn-lakemerit

and due west, over the opposite wall of Thornhill canyon, toward the Golden Gate.

elvrtn-ggate

Turn around, and it’s just a few steps to find these views of the Las Trampas Ridge area—

elvrtn-trampas

—and Mount Diablo, which never ceases to surprise me when I see it from Oakland. I think of Diablo as a whole different domain, reachable only by a drive through the tunnel and not visible west of Lafayette. But here it is, looking downright neighborly.

elvrtn-diablo

Only a few Oaklanders get to see the view east; we’re a westward-leaning city.


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