Oakland Geology

I took this photo last Tuesday, the day after our nice good rain. If you weren’t outdoors last week, you missed a brief moment in the Oakland year that lasts just a few days.

It’s the period between the first significant rain and the sprouting of the grasses. The first rain drenches the ground and changes the dry, gold-brown hillsides to a rare saturated dun color. Soon afterward the hills flush green, and we’re off to a new year in the Mediterranean climate cycle that governs the Bay area. Think of it like the week between Christmas and New Years, only it’s in the calendar that plants use.

This is a special hill at the southern end of the Berkeley Hills overlooking Route 24. Old topo maps mark it with its elevation of 1684 feet, but the latest ones label it Barberry Peak. To the right of this photo, shot from Skyline Boulevard near Radio Tower Hill, the ground plunges to the water gap and roadcut of Route 24. On the other side of 24 the ridge resumes, under the name Gudde Ridge, and rises to the peak of Round Top. So this hill is a northerly extension of Gudde Ridge. The following shots from the peak are from a visit in July 2013, during the gold season of the plant calendar.

Gudde Ridge (and its northern extension) is held up by the thick lava flows of the Moraga Formation. Like most of the rocks in the Oakland/Berkeley Hills, the Moraga Formation is tilted up to nearly vertical. You can reach 1684 Hill by an informal path off the Skyline Trail. The lower western slope of the ridge is underlain by Orinda Formation conglomerate, but basalt makes up its bulk.

Let’s look back west toward Radio Tower Hill. Last week’s photo was taken from the little saddle at the left edge.

The view north takes in the upper part of Siesta Valley. That’s Vollmer Peak in the middle, highest point in the Berkeley Hills. Grizzly Peak is just out of sight at the left, but the tip of its radio tower shows.

The view east overlooks lower Siesta Valley and Mount Diablo.

On a clearer day I imagine the Sierra Nevada is visible along the left horizon.

This entry was posted on 16 November 2015 at 8:03 am and is filed under Oakland peaks, Outside Oakland. 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.