Oakland geo-walks for out-of-towners

5 December 2016

Next week will be the 2016 Fall Meeting of the American Geophysical Union, held in San Francisco since time immemorial — actually, since the hippie days of 1968 — and I’ve attended every year since the early 1980s. Back then it was held in Bill Graham Auditorium; next week some 24,000 people from all over the world will overfill the entire Moscone Center to swap geoscience presentations.

Oddly for a worldwide geoscience organization, the AGU doesn’t schedule any field trips in the days before and after the meeting. If you come, you’re on your own. So, cross the bay and visit beautiful, geologically interesting Oakland.

come-to-oakland

Geologists, it’s easy to show yourself a good time here. You know your way around a geologic map: put USGS MF-2342 on your tablet or my Oakland-only excerpt. If you’re a Zipcar subscriber, ride the BART to the 19th or 12th Street stations and take your pick of cars.

No car? No problem — BART and bus are what I usually rely on. For the AC Transit bus lines, the secret to an easy experience is to buy a day pass (5$ cash, half if you’re 65+) the first time you climb aboard. The free CityMapper app will keep you oriented and informed.

Let’s talk about a typical afternoon day trip, because that’s what I know best — set out during early lunchtime and finish by early dinnertime or beer time (BeerByBART lists the best craft beer places, organized by BART station). You can travel light and cover lots of ground. There are three main starting/ending points: downtown, Rockridge and Fruitvale.

Downtown: Infinite number of lunch places on weekdays, you can’t lose. Goodly number of dinner places, from Jack London Square up to Grand Avenue (served by a free shuttle on Broadway). Many brewpubs and beer gardens on Telegraph Avenue and Broadway.

Rockridge: Delis, grocers for takeout on College Avenue. Plenty of restaurants. Ben & Nick’s for beers.

Fruitvale: Taquerias and carnicerias galore for food, Ale Industries for beer, or The Half Orange for both.

Your destinations are in our beautiful hills, because that’s where the rocks and the views are.

From Rockridge you can:

From downtown you can:

From Fruitvale you can:

If you have a car, you can:

And if you’re a maniac hiker, why not contemplate my hard-core one-way Oakland geology rambles:

Come on over.

Oakland building stones: Lime stones

28 November 2016

There isn’t a good word for the full variety of carbonate building stones — limestone, dolomite, marble, marlstone and travertine. Although I like the word limerock, it apparently doesn’t really exist. In any case, these rocks aren’t very common in Oakland’s buildings, the way they are in, say, Washington DC (all of those memorials, and the Pentagon too).

Part of the reason is that limestone/marble is uncommon in California, and here it’s more valuable as an industrial material than as dimension stone. For limestone, think Indiana and Wisconsin. For marble, think Alabama, Texas and Colorado.

Panels of fossiliferous limestone decorate a building at 9th and Clay.

fossilif-ls-panels

Take a closer look at all the fossils.

fossilif-ls-detail

A builder might call this marble because it takes a polish, but in my language geologists call it marble only if the rock has been metamorphosed, and that would erase all of these fossils.

Its warm color indicates a certain content of clay minerals as well as calcium carbonate minerals (calcite or aragonite). If clay is present in amounts comparable to the carbonates, the stone is referred to as marl or marlstone. The Torrey Pines Bank building, on Webster Street, uses a striking combination of buff and black marlstone. A small building can pull off this look.

marl-bank

The light stone is quarry-faced. The dark stone is fully dressed and then bush-hammer finished to lighten its color.

marl-corner

This stuff has a few fossils in it, too.

marl-fossils

Limestone is a sedimentary rock that forms in warm, shallow seas where sea life, most of it microscopic, takes calcium carbonate out of solution to build its shells. These limy shells pile up and are consolidated into stone at low temperatures and gentle conditions.

You’ll see this environment in the Bahamas, for instance, but the current geological age is not a limestone-building time because the seas are so low. For most of geologic time the low parts of the continents have been warm, shallow seas. Hence the huge limestone beds of Indiana and the rest of the Midwest.

Then there’s travertine. It’s not marble in my language, but it takes a polish so it’s industrial marble. Here it is next door to the Torrey Pines Bank.

travertine-panel

A closeup shows its weird — I mean, attractive character, full of pore spaces and irregular layers.

travertine-detail

It seems like it might be fragile, but it’s very strong. The ancient Romans loved it, and Italy supplies most of the world today. The Getty Center down in L.A. is a veritable Disneyland of travertine.

travertine-getty

Mountain View Cemetery uses a lot of it too.

travertine-mvc

Travertine grows in freshwater marshes, fed by springs of groundwater that’s full of dissolved limestone. It’s actually a renewable resource.

Marble, real marble, metamorphosed and recrystallized limestone, is a common accent and interior stone in Oakland. I like this staircase in City Hall, which pleasingly contrasts detailed tilework against the warmth and translucency of fine marble. The stairs are marble too.

marble-cityhall

“What about dolomite?” you ask. “You mentioned dolomite up there.” The mineral dolomite, magnesium-calcium carbonate, can be present in limestone and marble without affecting the names we give those stones. Pure dolomite rock, or dolostone, is pretty unusual as a dimension stone. But Oakland has a spectacular example of dolomite aggregate used as the facing of the Kaiser Center, which I featured here a few months ago.

The Resilient Oakland Playbook

21 November 2016

Last month the city of Oakland released its long-awaited resilience plan, the Resilient Oakland Playbook. “Resilience” is the 21st-century name for the concept that communities can get up quickly when they’re knocked down, and avoid being knocked down in the first place.

I’ve always thought of resilience in terms of how we deal with natural hazards — earthquake, flood, landslides, sea-level rise, fire. Oakland used a definition that seems closer to familiar city politics and good-government ideas. Frankly, it read as if Mayor Schaaf had simply copied and pasted part of her recent speeches:

Resilience in Oakland means equitable access to quality education and jobs, housing security and community safety. It means building vibrant infrastructure to better prepare for shocks like earthquakes and stresses like climate change. In Oakland, resilience means catalyzing our diverse pool of talents and perspectives to tackle these challenges, both inside and outside our government, with particular focus on addressing the needs of the most vulnerable members of our community.

This will take some getting used to. The geologic hazard of earthquakes is given its due, although there are no new ideas in the playbook beyond the ongoing, snail’s-pace work of encouraging retrofits of old soft-story apartments. The Earthquake Engineering Research Institute, a major source of relevant knowledge that’s headquartered in Oakland, didn’t participate in writing the Playbook.

softstory

Emergency preparedness is represented by a seven-month “Love Your Block” initiative in the Fire Department’s valuable CORE program. That was supposed to start in October, but there’s no sign of it on the city’s website.

The geologic hazards of climate change (a possible rise in floods and wildfires) and sea-level rise are pervasive in the Playbook. That’s OK, although I consider them remote problems. They will slowly creep up on us, noticeable only if you take a snapshot every decade. We need to make long-term plans and float bond issues to deal with them.

But there’s no mention of the mud that wipes out roads in Oakland every year. A “vibrant infrastructure” has to deal with our chronic landslides.

thornhillslide

The word “landslide” isn’t in the playbook once — homebuilders in the hills, you’re free to continue business as usual. Houses on alluvial hillsides, you’re off the radar.

Oakland needs the things in the Resilience Playbook. But we need more than that — we need to cultivate what Robert Muir Wood, a writer I’ve long admired, calls a disaster culture. Last month in the L.A. Times, Wood pointed to the Dutch as exemplars, citing their centuries-long effort to win land from the sea. “What Holland created — a national narrative of resilience, shared by all the people — is what L.A. (and every city threatened by natural disaster) should aspire to. Today, with the power of information technology and education, it won’t take centuries to evolve.”

Disasters don’t wait decades, and neither can we. Maybe the Playbook is how we’ll get to resilience. I’ll be happy if it is.