A Love of Bridges, Part 8: From My Oldest Set of Slides: Hanging Out Near a Transform Plate Boundary | Golden Gate Bridge, San Francisco to Marin County, California (1937)

Well, it took a lot of moxie for this Midwesterner to get this close to one of our planet's major transform plate boundaries, but I did it. This photo, taken with my trusty, square-format Instamatic at the dawn of its illustrious career, shows the magnificent suspension bridge from its southern (Presidio) end, at or near Golden Gate Postcard Viewpoint.

My occasion for being in San Francisco in the first week of that particular July was that I was a lowly Midshipman Third Class and part of the crew of the USS Hollister, an old, Gearing-class destroyer that was conducting a holiday port visit as part of our Pacific training cruise.

I believe that this image, and those that follow in this set, were taken specifically on July 5th of 1971. At any rate, I recall that the Fourth was my duty day, and I spent most of it in the firesides of the ship's Babcock and Wilcox boilers, cleaning out the accumulated black soot that's the combustion byproduct of Navy-grade fuel oil. After that metaphysically grimy experience, my fellow middies and I were only too happy to take a long walk in the open air—in this case, across the mile-long span we'd recently sailed under.

In addition to the mighty San Andreas transform fault, which runs northwestward from the southern side of the city to a little oceanward of the bridge and up to the Point Reyes area, there is the Hayward Fault just to the east, just across the bay in Oakland. And there are others as well. The last I checked with the US Geological Survey, the Hayward has a 33% chance of producing a Richter 6.7 earthquake or higher by 2043; for the same timeframe the San Andreas has a 22% probability. Most San Franciscans and their neighbors apparently are feeling lucky. But I was born into a culture with a different approach to anxiety.

What the Pacific and North American Plates are going to do or not do in the near future is one aspect of California's ever-dramatic geology. Another is the bedrock, or rather the bedrocks, of the greater Bay Area. The crust that anchors the bridge on this side, at Fort Point in the Presidio, is mostly Jurassic-period serpentinite mélange of the Coast Range Ophiolite. This assemblage of metamorphosed upper mantle and seafloor rocks has been glommed onto various portions of the state's western side.

On the far, Marin County side of the bridge, however, the hills closest to the strait are composed of Jurassic to Cretaceous units (sandstone, chert, volcanics, etc.) of the Franciscan Complex. Throughout the whole area, however, there is quite a patchwork of these and other units, including large Quaternary sand deposits. That's what happens when you're on the leading edge of a continent, which generally collects a lot of interesting and exotic things over the course of millions of years.

The other photos and descriptions of this series can be found in my Love of Bridges album.

Taken in: United States / California / Fort Winfield Scott (show map)

Taken on: July 1, 1971

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Sets appears in: • Architectural Geology of California • The Beauty of Building Materials more » • A Love of Bridges • Mountains & Hills; Mesas & Buttes; Hogbacks, Cuestas, & Flatirons • Natural History: California • Ortsinn: Landscapes & Localities • Shorelines • Urban Exposures: La città esaminata « less

Groups appears in: • Landschaft/Landscape • Water... Oceans, Lakes, Rivers, Creeks more » • Geology Rockers • GeoTagging Flickr • Geotagged • Geology • Architecture | Nature • Architecture Photography • *Inspirational Travel Photos • Geologists • USA - UNITED STATES OF AMERICA • Architecture of Days Gone By • The World of Architecture • Landscapes of the World • Geology for all • Geology/EarthScience • Architectural Photography Group • Great Buildings • America's Best Landscapes • American Photography • California Nature • Geotagged: California • Geology Flickrs • USA Landscape Photography • California Landscape Photographer • Landscape Photography: From Snapshots to Great Shots • World Of Architecture • Landscapes of the earth • Soft Rock Geology • On Landscape • National Parks of the USA • Photography with a Story • Geology / Geologie • The Very Great Outdoors • We love Nature and Geology • Landscapes Buildings Waters | Landschaften Bauwerke Gewässer • American West Flickrology • (A)111 AMERICAN NATIONAL PARKS: CANADA & US « less

Camera: MAKER NAME 96660, f/1.8, 1/128 sec, 2.8mm, ISO 50 (more info) (hide info)

Camera:	MAKER NAME 96660
Aperture:	f/1.8
Exposure Time:	0.008 sec (1/128)
Focal Length:	2.8mm
ISO:	50
Exposure Bias:	-0.7 EV
Flash:	Auto, Did not fire
Exposure Program:	Program AE
Metering Mode:	Average
White Balance:	Auto
Color Space:	Uncalibrated
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