Oakland Geology

These days we’re all sheltering in place: doctor’s orders. What better thing to do than rummage through those thousands of camera images on our hard drives? This phase of our lives is going to last a while, and I have little sense of what I’ll be writing here instead of reports from the field, my tried-and-true resort. I’ll start anyway, with a dozen shots of Oakland’s incomparable defining feature: its backdrop of hills. From near, from far, from every part of town, the Oakland Hills make up our civic stage set.

What they do: The early boosters in the 1800s wrote florid panegyrics about both the beauty of the hills and their salubrious effect on our local climate. They elevate the Pacific winds so that San Francisco’s notorious ground-hugging summer fog never bothers us, and they gather orographic rainfall that keeps the streams flowing. The hills give our topography a concave shape, like a skateboard ramp, that makes every place in the city visible from every other place.

How they look: The hills shift their colors and shadows throughout the day and around the year. Right now they stand out in crisp focus because the air, almost free of traffic pollution and seasonal haze, is so clear. Look at them on a hazy or misty day and they resolve into a set of ridges, arranged in depth. They turn the most prosaic places pretty, and they set off our best buildings to advantage. They peek from behind every photo, a welcome intruder. Without them, this would not be Oakland.

What they are: The Oakland Hills are tectonic hills. They arise along the far side of the Hayward fault because there is a modest amount of compression across the fault in addition to its dominant sideways displacement. They’re not the product of thrust faulting, bulldozed up like the San Gabriels or the Rockies or the Himalaya; not the product of crustal stretching like the basins and ranges of Nevada; not erosional eminences like the Appalachians. They’ve been sort of smeared up. They have a wide variety of rocks in them, arranged in a pre-existing order that isn’t closely related to their shape.

These images are presented from north to south. As usual, click them for the 800-pixel version.

I offer these images not to encourage you to visit the hills (unless you live among them), but to inspire you to hang in there until we can again. I hunger to return to them, but at least I can see them whenever I walk outside.

This entry was posted on 13 April 2020 at 8:01 am and is filed under 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.