Archive for the ‘“Deep Oakland”’ Category

Introducing Deep Oakland 2: Lake Merritt

29 August 2022

Lake Merritt, subject of chapter 2 of Deep Oakland, is something of a yang to the Hayward fault’s yin: “Whereas the Hayward Fault perturbs us with energy from the Earth’s interior, Lake Merritt connects us to the world ocean, the world atmosphere, and the cosmic cycles of the solar system.” The lake is far more than it appears to be.

The lake’s human history is well known. First of all it’s not a real lake, but a freakish arm of the Bay — a slough — that reaches straight inland a couple miles, unlike any other shoreline feature in the East Bay. We’ve called it “lake” since Mayor Samuel Merritt dammed it at the 12th Street crossing in 1869, even though that only muffled the daily tides. For a long time it was the city’s open sewer. Then over the course of the 20th century, the slough was mucked out, its shore developed as city parkland and its waters cleaned up to make it the ornamental pool we love so much today, with real live sea life and shorebirds.

In the landforms around the lake, the geologist sees evidence of three different parts of the deep past. Two of them are related to the ice age, by which I mean the latest of dozens of ice-age cycles that we’ve been living through for the last few million years. The younger of these two landforms is the sandy platform that holds downtown Oakland.

Chapter 3, “Downtown,” gets deep into that, so I’ll just briefly say here that if you picture an ice age, it’s a cycle roughly 100 thousand years long of huge polar ice caps growing and melting. The ice ages are triggered by slow oscillations of the Earth’s orbit caused by the gravity of Jupiter and Saturn, and that’s the cosmic cycle I mentioned. Today we’re living during a warm peak, but not so long ago we were at the cold peak, with maximum ice and very low sea levels. The shoreline was way out by the Farallon Islands, and everything from here to there was fresh sand and gravel carried down from glaciers in the Sierra Nevada. That’s how San Francisco got covered with sand dunes, and so did downtown Oakland and the whole dry Bay in between.

Now this point is important: if you picture what must have been here at that time, it was dry land. In fact, the same streams that feed the lake today were digging a deep ravine here.

Then there’s the older of the two ice-age landforms, the flat ground on Adams Point that holds Lakeside Park (and a few other places around the lake).

This platform is a little lower than the downtown platform. It’s made of gravel, not sand.

It dates from the last time there was a warm peak in the ice-age cycles. The sea level was even higher than today, and the same streams that drain into the lake today were building terraces of sediment along that higher shore.

The whole ice-age thing, highs and lows and 100,000-year cycles, means that for most of recent geological time there’s been no lake here; Lake Merritt is a rare, temporary feature that reappears only during the warm peaks like today. But it keeps coming back because of what’s upstream: that block of hills near the Bay, in front of the high hills, that the city of Piedmont sits on.

All of the streams that drain into the lake come from that ridge, and when it rains hard enough for them to do some serious work, those streams combine to send a powerful flush of water through here. That’s why the deep ravine that periodically becomes Lake Merritt persists through cycle after cycle of ice ages. But that’s a story I get into in later chapters. For now I’ll just say that it’s connected to the third set of Lake Merritt’s landforms: the steep hills of the Adams Point, Cleveland Heights and Grand Lake neighborhoods.

Look for these hills and terraces next time you visit. Collect them all.

Introducing Deep Oakland 1: The Hayward Fault

22 August 2022

Chapter 1 of Deep Oakland features the Hayward fault—Oakland’s prime mover. The energies that play out on the fault have built a distinctive East Bay landscape that has looked roughly the same as it does now for a least a million years, maybe two: a long ridge of mixed rock types no more than a kilometer high but never very low either; a middle ground along the fault where the hills, streams and valleys are strangely organized; and a wide alluvial flat and gentle coastal zone. A great wave from the ridgeline to the shoreline: Swell, surf and swash. The fault is the builder and maintainer of our special landscape. “The fault has made us beautiful,” I start off saying, “but it also keeps us on our toes.”

The Hayward fault has a central role in the book, and this chapter has a lot of ground to cover. I visit a few sites along the fault where its effects are easily seen; some (like this and this and this) are things I’ve posted about here.

In Deep Oakland I try, as I do on this blog, to approach the fault as a thing of interest rather than a source of dread. On the fault that maintains Oakland, construction is always in progress, destabilizing the land.

Some of the changes are slow and constant. Deep in the Earth at the base of the fault, the rocks warp like taffy in response to steady, relentless shear between the North America and Pacific plates. Higher within the Earth’s crust, where the rocks are hard and brittle, the same motion happens in bursts. Earthquakes! (Oops, there’s the dread.) And up near the Earth’s surface, in the top kilometer or two where conditions are gentler, the Hayward fault moves steadily, a few millimeters a year, in a counterpart of the deep shear known as creep.

Creep is the most disruptive thing the fault is doing right now. Over the years, creep damages whatever is on or under the ground.

The big work, meters at a time, is done in earthquake jolts. Big ones are occasional rather than regular, but they’re inevitable. The fault hasn’t ruptured the ground in a large earthquake since 1868, when Oakland was a small, ambitious town of about ten thousand people. The fault zone in the hills was a remote frontier, way out of town. In the years after the quake, as homes and roads and infrastructure moved in starting with Anthony Chabot’s dams, no one spoke of the fault (although Chabot built his dams extra strong).

So here we all are today (hi, me too), living on ground that’s bound to shake us down. How do we live with it? In the book I say it takes “the right mix of denial, preparation and equanimity.” How we should live with it is another question, with no easy answer.

Between quakes and creep, the fault keeps nudging Oakland’s landscape into unusual and precarious configurations. It gradually uplifts the hills; they respond by eroding and falling down. By pulling the land sideways, the fault disrupts all the streams that flow across it, adding kinks to their courses and swapping watersheds from creek to creek over the ages. And the rising hills on the one side urge the other side down, keeping it just below sea level and maintaining the beautiful San Francisco Bay. Without the Hayward fault and its siblings that together have built the Coast Range, Oakland would be just another Central Valley town. Oakland is earthquake country.

In the end, I come back to a long view of the fault: “Patiently over millions of years, it has arranged Oakland’s landscape, affecting all of its parts—and the lives of those in them—in ways it takes a geologist to appreciate.” The fault is a presence in each of the book’s eleven chapters.

PS: In the endnotes, Deep Oakland cites my blog posts as places to learn more about a topic. I figure this site will last about as long as the book does, and it’s archived too. It’s as good as paper for practical purposes.

Images: View from the self-storage building on San Pablo; Ney Avenue; Broadway Terrace at Lake Temescal

Introducing Deep Oakland: The title

15 August 2022

This post is the first of a weekly series that will summarize my upcoming book, Deep Oakland: How Geology Shaped a City. The book has eleven chapters, and each post will go into one of them. But first I wanted to talk about the title.

I was raised a Navy child, and I’ve lived in several different places, so I know about moving. When we arrive in a new city, we learn where everything is and how to get there, and that’s enough to know for us to live our lives. As we stay longer, though, curiosity kicks in and we may start to learn where things were and how they got there. There’s a deeper city beneath and behind the city we spend our days in. Clues include this odd intersection; that old home; a road’s unexpected detour; a place that developers have left alone; overgrown foundations; faded slogans on old brick walls.

Geologists do the same thing, only it’s the city’s landscape and rock exposures that they focus on. Their starting point is beneath and behind the city itself. They envision the land at other times, in different climates, with different inhabitants and vegetation.

That is to say, there are two deep Oaklands. We may never care about the geologist’s version, and they may be indifferent to our human version. Over thirty-three years in this town, I’ve learned a lot about both deep Oaklands, and I think they’re both exceptional. The human city has all the drama and events that every major California city has undergone, and geologically, Oakland has an exceptional range of features related to every major geological episode that has formed California as we know it. It has, I believe, more variety among its rocks than any other city in America. Oakland is a great place to learn about both California history and California geology.

Then there’s the subtitle, “how geology shaped a city.” The land of Oakland has been inhabited by several different waves of people. We know about the last three: the Ohlone tribes nurtured and harvested the land; the colonial Spanish staged a geopolitical drama on it; the Americans relentlessly exploited it. As I told The Oaklandside last month, “the choices that different people have made here, from the Ohlones to the Americans, depended on facts in the landscape that each have a geological story.” In Deep Oakland I show how these choices went different ways at different times, according to the cultures of the inhabitants. As Americans continue to change, so can our choices. By illuminating how things have changed, I hope to bring more perspective, and possibly more wisdom, to our future choices.

Geology is one of the things that ground me. Perhaps that’s compensation for an upbringing of regular uprootedness. The Indigenous worldview, so easily misconstrued and caricatured, for me has always meant a deep kinship with the country around my home. Although Oakland’s inhabitants will never fully regain the lived experience of the Ohlones, who continue to speak of belonging to the land, I hope to thin the insulation between us and the land we live in. That’s where the book and I are coming from.

Book In Progress

2 August 2021

I’m going to take a break and tell you about the book, one I’ve been hinting at off and on for a few years now.

Its working title is “Deep Oakland” and it’s about this city, the ground that birthed and nurtured it, and the ways Oakland’s geology — and any city’s — matters to its people. It’s part Earth science, part history and part arm-waving talk by the side of a roadcut. Someone could write such a book about any city, but Oakland is an unusually good subject, with eleven chapters worth of examples.

“Deep Oakland” got its start a long time ago: in fact, one reason I started this blog, in 2007, was a naive idea that once I had enough posts I could just paste them together and have a good start on a book. No, doesn’t work that way. The first draft was finished four years ago, and draft six, the final draft, will be finished four months from now. How do I know that? The contract I’m about to sign says so. As I learned long ago writing geology-related piecework for the site now known as ThoughtCo, a manuscript is never done, just due.

The book will be published by a highly respected local press. Under its final title, whatever that is (presumably they’ll append a long subtitle), it will come out as a proper hardback in the spring of 2023. Be assured I will keep y’all fully informed as things progress.

There are some neat things about this project:

  • The first four drafts are completely different from the last two. My first efforts ended up being a geologizing manual for Oaklanders. Nevertheless the publisher liked what they saw and suggested that I submit something different. I looked at all the bits I had that weren’t fitting into that manuscript and accepted their challenge. The writing experience has been great. But the manual is still worth publishing, and it’s completely independent of the new “Deep Oakland.”
  • As many nonprofit publishers are doing, this publication will involve some fundraising on my part. And I’m up for that. I won’t start a formal campaign, with premiums and so on, until next year — there’s enough on my plate this year. But from now until then, any contributions that come in through the PayPal link will be dedicated to that purpose.
  • This blog is completely independent of the book; there’s been no cutting and pasting. Long-time readers will recognize the places I visit and some of the ideas I’ve espoused here, but the whole thing will be fresh, coherent and integrated. The publisher will bring in an expert illustrator, so there will be none of my phone-cam photos or bloggy graphics in it.

I’m excited. Stay tuned.