Oakland Geology

Since I featured what I called the big set of knockers (or in geology-speak, large competent blocks in Franciscan melange matrix) at Mountain View Cemetery, almost 3 years ago, the operators of the cemetery have opened a new premium section just below and removed most of the trees, unveiling the best rock on the hill. I visited it this evening. It’s still not much to look at unless you’re looking for it.

It’s mostly pale-green ribbon chert with some red chert. You might say the green rock has undergone a sea change. I’m not one of the experts in the Franciscan, but red rocks, which owe their color to trivalent iron (Fe³⁺), commonly turn greenish as the iron is reduced to divalent Fe²⁺, so I take it that this chert has undergone some challenging conditions in the ancient subduction zone that created the mixed-up melange. I find it harmonious.

Here’s a closeup. Click it for the full 1000 pixels.

Stone like this doesn’t support a lot of life, being low in nutrients, but lichens have a foothold on it, especially where moisture can gather. The eastern, uphill side is like that, and the total impression, stone and sky and place and time, is most pleasing.

Visit the “cemetery knockers” category for the whole set.

This entry was posted on 10 April 2011 at 9:13 pm and is filed under Cemetery boulders. 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.