Oakland Geology

I have believed — and what’s worse, repeated — that Oakland’s highest point is Grizzly Peak. In fact, the highest point within the city limits is Chaparral Peak, an eminence so subtle you can barely tell it’s there.

Let’s look at the 1959 topo map of the high Berkeley Hills. Everything south of the county line is in Oakland.

Grizzly Peak stands out, at approximately 1745 feet. Figures differ, so don’t quote me on that. But Chaparral Peak definitely rises above the 1760 foot contour, making it a hair over one-third of a mile above the Bay. Here’s the mountaintop, such as it is.

It’s Oakland’s largest exposure of the Bald Peak Basalt, which extends from here beyond Vollmer Peak.

Chaparral Peak is the heart of Frowning Ridge, a name we don’t use much (and I’m not sure we ever did). Frowning Ridge is an ill-defined set of peaks and eminences running from Grizzly Peak to Chaparral Peak and then down Siesta Valley where it’s cut off by a fault. This is the view upridge to Grizzly Peak. Mount Tam is in back, on the left.

And this is the view southeast to the Oakland Hills.

Round Top is in the center, against the sky, and exactly in front of it is Barberry Peak. On the right rises a nameless hill, topped by a large installation, where the county line goes. I think of these as affiliated with Gudde Ridge, on the south side of Route 24, because they line up with it.

Both ridges reflect the presence of volcanic rock units. Frowning Ridge is held up by the Bald Peak Basalt and Gudde Ridge (and its northern affiliates) by the Moraga Formation.

Here’s one more view, this time due east across the far flank of Siesta Valley to Mount Diablo.

The Mount Diablo Base Line, the master line for land surveys in most of northern California and all of Nevada, runs right through Chapparal Peak. That’s the red line on the map, with Township 1 North and 1 South on either side of it.

This entry was posted on 25 September 2017 at 8:03 am and is filed under Oakland peaks. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.