Archive for the ‘other’ Category

Our native forest

8 February 2016

I spent Saturday in Napa Valley on a field trip with the Northern California Geological Society, visiting the ultrapremium Promontory vineyards west of Yountville and the merely superpremium vineyards of Harlan Estate west of Oakville.

High-end wine is a culture obsessed with the character of land, and Bill Harlan talked a lot about his land as we tasted the 2009 releases from both sites. What struck me most was his emphasis on the forest around the vineyards. Both properties are enclaves of vineyards in a forested setting. This view of woods-encircled vines is from the top of Promontory.

promontory-op

Harlan spoke of airs and influences while, given my recent reading, I thought of wild yeasts and soil microbiomes. I also thought of Oakland’s woods, which have been on my mind lately as I’ve explored the Leona hills.

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To some Oaklanders, all trees are good trees. To me, the oak forest is what belongs here, and eucalypts should be exterminated from our wild lands. I’ll spell out several reasons, mostly familiar, plus a new one about living in Anthropocene time. But first, a clump of oaks in the Leona hills.

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History: Once our oaks were the basis of a thriving native economy, and their acorns are still here in abundance for true locavores. Eucalypts were planted in our hills in a failed attempt to make a killing in timber. The poet Joaquin Miller, spellbound by a Victorian ideal of Arcadia, covered his grassy Hights with thousands more. Neither wave of tree-planting was done responsibly. We owe that legacy of heedlessness the same respect we owe pampas grass, French broom, foxtail grass and other pest species. Here’s a mono-stand near the Caldecott Tunnel.

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Aesthetics: Our native oaks hug the hills in fleecy blankets; eucalypts hide them in scraggly tufts. Compare the two types of forest, side by side at Lake Chabot. The very air is different.

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Accessibility: In my search for rocks, I go off trail and across country. Eucalyptus country is typically impassible, the footing noisy and slippery. Oak country is typically parklike and quiet, like this grove in the Leona hills — although it’s friendlier to poison oak, I’ll give you that.

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Ecology: Oaks make food and mulch; eucalypts make trash.

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The Anthropocene: The future’s climate is up to us. It’s vital that we pull CO2 out of the air. Trees are touted for doing that, but planting and managing forests is a sophisticated practice we’re just beginning to understand. Forests are more than just groves of fixed carbon. By far the majority of a forest’s carbon is in its soil, not above the ground.

A newly published study argues that more than two centuries of reforesting the European landscape hasn’t made a lick of difference to its CO2 balance. Because the new forests were managed for timber, the wrong kind of trees were subsidized.

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Luckily, we don’t harvest timber in Oakland any more, so we can do things the right way. That means nurturing the biomes that suit the region: native oaks, redwood, chapparal and coastal wetland. Their intricate webs of underground organisms, tuned to our rocks and climate over thousands of years, soak up carbon better than any other strategy.

Well-chosen eucalypts are splendid specimen trees, but they should be phased out in the wild. If we feed our wildland soils correctly, Oakland can do its share to fight global warming. And it will be better in all the ways I’ve mentioned.

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Restoring our land will take time, sustained funding and the same dedication that Bill Harlan gives his vineyards. If we take our ownership of Oakland’s land seriously, we can’t slack.

Geology meets art in the Oakland Museum

14 December 2015

suiseki-rivera

The Oakland Museum of California just opened an exhibit called “UNEARTHED: Found + Made,” and this is the first thing you see when you go there. It is a suiseki stone, collected by the late Felix Rivera in the California desert and prepared and mounted by him according to artistic principles codified centuries ago in Japan. When you visit the show, slow way down at the entrance and drink in its form, colors and presence. The exhibit features about twenty more of these rugged individuals, all exquisitely lit.

I took this photo months earlier under fluorescent lights in a back room at the museum. More about that later.

That’s the “found” part. The “made” part is a set of works by Jedediah Caesar, which complement the suiseki in an off-kilter way. He picks up things off the ground, too, mostly things that are not rocks. He may mix them into a vat of liquid plastic, let it set, and then saw the resulting block into slices, like building stones. Those are on the walls. This larger piece is on the floor.

Jed-Caesar-art

If I have this right, Caesar mixed turmeric into the plastic, which caused a vigorous reaction much like volcanic gases might produce in magma. In any case, his works have a certain geological cast and are a feast for the eyes.

I took that shot with my phone at the opening reception, where I was an invited guest. The museum staff had sought my help as they were preparing the exhibit. You know how for every piece of art, they say what it’s made of? “Albumen print.” “Stainless steel.” “Oil on canvas.” They wanted me to help them do that with the suiseki — you know, like “pegmatite on wood stand.”

Now suiseki collectors don’t know this stuff. Mostly they ignore geology, as they should. To talk about a suiseki’s rock type is to miss the point of the art. And the whole point of geology is to observe rocks, not appreciate them. But I made my best effort to “identify” the stones, relishing the absurdity as I did so. And if you disagree with the names I chose, I’m sure you’re as correct as I was.

Two lessons about floods

19 October 2015

As we anticipate the strong possibility of heavy El Niño rains, my attention will be on Oakland’s streams this winter. Last week parts of southern California were hit by “thousand-year” rainfall events, cloudbursts that washed thick sheets of mud over roads and properties. We can expect such things here too, in any given thousand-year period.

Arroyo Viejo, the stream that crosses Knowland Park, offers two lessons about floods. The scene below is at the northern edge of the park, looking upstream: a streambed piled with boulders, some as large as sofas. (All photos 800 px)

A-viejo-in-K-park

Notice: these rocks have been tumbled by the stream. How much water would it take to do that? Let’s make a rough, arm-waving estimate.

The rainfall in last week’s cloudburst was almost 4 inches in one hour. Had it fallen on the watershed of Arroyo Viejo above this point — say, half a square kilometer — it would represent an input of roughly 30 cubic meters of rainwater every second.

Picture in your mind that volume of water — no, it would be mud and therefore that much greater — funnelled through this narrow valley. Do a little geometry and it’s easy to see the floodwater would be well above the tops of the boulders.

Hidden in plain sight in this photo, then, is a single hour of tumult that might have happened a thousand years ago or five hundered years ago — or perhaps during the dreadful winter of 1861-62, when it rained for 43 straight days and much of the Central Valley became a lake.

The lesson is that most of geology’s hard work gets done in rare spurts of extraordinary activity.

Okay, the second lesson is hidden in these rocks. All of them, like this boulder as tall as me, are made of conglomerate.

Knox-in-A-viejo1

These rocks, assigned to the Knoxville Formation of Late Jurassic to Early Cretaceous age, were laid down by ancient floods in a nearshore or terrestrial setting. I’ll show you three different specimens. Notice the large clasts and the fine-grained matrix that surrounds them.

Knox-in-A-viejo2

This boulder displays a wide range of clast sizes. It was probably laid down by what’s called a hyperpycnal flow, a slurry of sediment that carries everything along with it. We’ve watched them happen offshore in Monterey Canyon. Here’s another example.

Knox-in-A-viejo3

Instead of an underwater landslide, as seen in the first specimen, this represents something gentler and more organized, like a mudflow, or like the mudslides we saw in the news. The clasts are aligned with the current that carried them here.

The key observation in both cases is that the large clasts are floating in the matrix. In geologist’s terms, they are matrix-supported conglomerates.

Then we have this.

Knox-in-A-viejo4

Here’s a beautiful clast-supported conglomerate. It represents a clean bed of well-rounded cobbles, all touching each other, like you’d see in a rushing stream or a rocky beach, nicely infiltrated with clean silt or clay after it was laid down.

None of these stones were made by ordinary sediment wafting down streams during ordinary rainy seasons. They were assembled by floods of all sizes.


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