Archive for the ‘Oakland peaks’ Category

Grizzly Peak

20 December 2014

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

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

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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.

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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.

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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.

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

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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.

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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.

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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.

Middleton hill

26 July 2013

Way down in the Sheffield Village neighborhood is a big hill and a little hill, but most of the place is in a flat little basin. The geologic map shows it as a patch of old alluvial sediment of the same vintage as the Fan:

sheffieldmap

The big hill is on the east side, across the Hayward fault (the black line from the lower right corner). The little hill is on the west side, butting against I-580. The road on its west side is Middleton Street, so I give the hill that name. I didn’t realize it when I poked around there earlier this month, but the hill is mapped as San Leandro Gabbro, of Jurassic age. The rock doesn’t show itself very much, but here’s a small exposure. Next time I’ll bring a hammer.

middletonhill

The highlight of the hill is the little private park inside the ring of houses there, just a microscopic piece of the original oak meadow (although this is actually a cork oak).

middletonpark

From there you get a nice view of the big hill. The fault runs along the foot of the hills, behind the homes in the center and in front of the lower set of homes on the right.

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Click the photo for a big version.

Bella Vista hill

22 July 2012

Bella Vista hill is part of the big Pleistocene alluvial fan that sprawls across the middle of Oakland, as shown by the “Qpaf” code on the geologic map.

pleistocene fan

The “Qmt” code is the marine terrace I’ve discussed before. The fan is dissected by modern streams into several lobes, which take their position in today’s cityscape as distinct topographic hills as seen in Google Maps topography:

topography

Bella Vista hill lies in the polygon defined by Park Boulevard, East 34th Street, MacArthur Boulevard, 14th Avenue, East 18th Street and 8th Avenue. All of those street run in valleys or saddles, except that East 18th is on a break in slope. The numbers refer to the following photos, taken from across or in the valley of 14th Avenue Creek.

The hill is low on its bayward side, as shown here from E. 22nd Street.

It has a corrugated surface, such that 9th, 10th and 12th Avenues run on high ground and 8th, 11th and 13th run up declivities. Higher up on the hill, the ground is steeper and the allee of palms marking the former Francis Smith estate is the defining feature of the hill.

The top of the hill has two eminences. The more dramatic one is on the south where Highland Hospital frowns down upon the stream valley.

hospital

Hospitals, like schools, were traditionally sited to take advantage of fresh air. Highland Hospital took its very name from this practice. Here’s a view of the whole hospital complex on the southern boss of the hill.

highland hospital

The northern knob is higher, exceeding 200 feet elevation. At its high end, 10th Avenue becomes Bella Vista Avenue and curves across this peak. Old palm trees from the Smith estate mark it from a distance.

Borax Smith knew what he was doing when he picked this hilltop for his home base. The hills on the fan to the south are a bit higher, but the views to every other direction were unimpaired from that spot. If you want to walk the crest of this hill, go up 10th or 12th Avenue and jog across to 13th and take it all the way up to the I-580 overcrossing.