Oakland Geology

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.

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 . . .

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

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.

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.

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.

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.

This entry was posted on 5 March 2015 at 11:56 am and is filed under Hayward fault, Landslides, Oakland geology views. 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.