Oakland Geology

I was up in Redwood Park this morning looking for this. Not the woods or the sun or the fine cool air, lightly scented with fall leaves. A textbook publisher wanted a photo of bent trees like these, which curve because they grew on a creeping slope. The sandstones across the Oakland hills weather into clean, fine sand that doesn’t have much strength. Thus the slopes in the redwood groves are as steep as a sandpile. Redwoods favor the sandstone because it retains moisture, and they seem to be fine with the angle of slope. But other trees root themselves differently, helpless against the very slow, steady earth movement called soil creep, and saplings may have to correct their stance as the ground shifts.

If compression across the Hayward fault didn’t keep pushing the hills up, they wouldn’t have these intimidating slopes but would soften into something more like the hills of Moraga.

The valley here is precious for being the habitat of the rainbow trout’s type population, the community of fish from which the species was first officially described. That doesn’t mean that the trout here are higher in genetic diversity, or bigger, or more special in any way except their fortuitous encounter with a biologist. But the park is taking good steps to safeguard the stream anyway, and I am so proud of East Bay voters for continuing to ensure funds for the regional park system. Developers take care of themselves; utilities and municipalities do too. Only the people, united, can take care of their common lands.

This entry was posted on 12 November 2008 at 6:55 pm and is filed under Oakland sediment and soil. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.