Why Did the Military Get Such Nice Digs? Fort Baker on San Francisco Bay

The reasons are partly geological. But before we mention the geology, there must be pictures of cute and interesting animals...like this young sea lion that was eying the crowd of fisherman on the wharf. We were in the Bay Area today celebrating a birthday, but everywhere we went was crowded, as if it were a holiday weekend or something. No parking on the beach at Half Moon Bay. Nothing at either end of the Golden Gate Bridge. The Marin Headlands didn't look particularly crowded from a distance, but the offramp on 101 was backed up for a quarter mile. There was a crowded art festival at Sausalito. We despaired of finding any place to hang out, but a short distance from Sausalito we found a quiet uncrowded park that had somehow missed my notice in the past: Fort Baker.

The military got all the best spots on San Francisco Bay. The Presidio is a huge complex on the northernmost part of the San Francisco peninsula, and the Marin Headlands were covered with forts and outposts, as well as an imposing group of gun batteries. It isn't hard to figure out why. Before the days when wars could be fought with buttons and missiles and drones, you had to assault other countries with some kind of invading force, and if the countries were bounded by shorelines, you had to invade with ships. A brief look at a map of the California coastline reveals that the state has a grand total of two natural harbors: San Francisco Bay, and Coronado Bay down south at San Diego. Two harbors that controlled essentially all major ship traffic south of the Columbia River in Oregon and Washington. Strategically, this is a vulnerability.

The eastern and southern coasts of the United States are geologically stable and are replete with fine harbors as a result of the steep rise in sea level that accompanied the melting of the glaciers at the end of the last Ice Age. River mouths were drowned, providing extensive bays, and deep anchorages.

California is different. It sits on an active plate boundary, the San Andreas transform, and many parts of the coast rise steeply from the depths of the sea. The tectonic uplift has been geologically rapid, and erosion has not kept up in most places. The one exception in central California is San Francisco where the Sacramento/San Joaquin river system was able to carve a canyon through the rapidly rising Coast Ranges. When the ice ages ended, the rise of sea level filled the lower canyon of the Sacramento and San Francisco Bay was the result.

Fort Baker dates from around 1905 when the United States military was beginning to realize the vulnerability of the west coast to attacks by sea. By the time World War II rolled around, the hills above the Golden Gate bristled with cannons. Any armada that tried to enter San Francisco Bay would have been carved to pieces by the crossfire.

The nature of warfare has changed and the gun emplacements and military forts at San Francisco became obsolete. The Presidio was given over to the National Park Service in 1994, and the last soldiers left Fort Baker in 2000. The areas are now managed as part of the Golden Gate National Recreation Area.

On this holiday weekend we discovered Fort Baker was uncrowded and beautiful. There was a simply spectacular view of San Francisco and a unique perspective of the Golden Gate Bridge. There was plenty of animal life to keep us entertained, and from the look of things, the fishing was good. It was a fine day....

My Beautiful California: A Day on the Marin Headlands

I have spent a lot of time writing about the "Other California", the places in my state that don't always appear on the postcards. I am always hoping to make folks aware of the riches our state has to offer when one gets off the beaten path, but I find that sometimes I like to go where everyone else goes, because, let's face it, California is a spectacular place. Today was one of those times, as I found myself on Highway 1 in the late afternoon exploring the Marin Headlands and Mt. Tamalpais State Park (the Headlands are part of the Golden Gate National Recreation Area). These are the rugged mountains and coast at the north end of the Golden Gate Bridge outside of San Francisco.

This beautiful stretch of coast is composed of the rocks of the Franciscan Complex, a chaotic mix of deep sea sands and muds, fragments of ocean crust and mantle, and even the occasional limestone reef deposit. The rocks formed in the trench of a subduction zone that lay off the coast of California in the time of the dinosaurs. The subduction zone is long gone, but the geologic violence that contributed to their origin continues in the lateral movement of the San Andreas fault which passes a short distance offshore. Large earthquakes like the one that devastated San Francisco in 1906 (close to magnitude 8) can tear the fault over a distance of 200 miles, and shift the crust 10-20 feet over much of that distance. The quakes occur every 100-150 years or so (do the math...).

The San Andreas has been active for more than 20 million years, and in that time has transported a wide swath of California and Baja California northward some 200 miles. Part of the evidence can be seen in the gratuitous sunset picture below, as one can pick out some small islands on the horizon. These are the Farallon Islands, which are composed of granitic rock related to the Sierra Nevada batholith exposed far to the south. The small islands are an important bird rookery, and the only human inhabitants are a few biology researchers.

The storm that threatened to wash out our field trip yesterday (but conveniently waited until the evening to let loose) cleaned up the sky and the gave us a beautiful sunset.

Before heading out for dinner, we stopped briefly on a ridge over the Golden Gate Bridge, and took in one of the most beautiful of all cities, San Francisco. It was a beautiful evening!

Now THIS is why I love California beyond words (but I will use words anyway!)

California gets a lot of crap from around the country for whatever reasons (San Francisco liberals, Berzerkely, L.A. riots and floods, earthquakes, the whole nine yards), but you know what? I think people are just jealous, because my fair state is one of the most beautiful and interesting corners of planet Earth. Today provides a fine example.

I've been blogging a lot about Yosemite National Park of late, and frankly, lots more is coming, but I had an errand in the San Francisco Bay area this afternoon. Yosemite is a two hour drive from where I live. The Golden Gate Bridge is a two hour drive from where I live. My home town routinely comes up 49th or 50th out of 50 on those "best places to live in America" lists, and it has its problems, but I bet a lot of my geology friends would give up a lot just to be able to play in the snow for a few hours before heading to the beach to work on that sunburn. Or to put it more, eh, sophisticated-like, to go from the granite intrusions of a Mesozoic magmatic arc to the deep heart of a fossil subduction zone in the space of a few hours.

So, a few pictures of what we did after we finished our errands. We headed out onto the Marin Headlands, part of the Golden Gate National Recreational Area. The headlands are those dramatic hills at the north end of the Golden Gate Bridge. There's a winding narrow road that traverses the cliffs above the bridge, providing incredible views of the sea cliffs and San Francisco, which just has to be one of the prettiest cities in the world. The road ends at Rodeo Beach (picture above), which is just another typical northern California beach, meaning utterly breathtaking.

The rocks are strange; deep red brown and black, occasionally gray and green. The deep red layers in the picture above are ribbon cherts from the ocean floor, while the black bulbous looking rocks in the picture below are pillow basalts. They are the remains of deep ocean sediment and oceanic crust that were swept into the subduction zone that lay off the coast of central California from around 200 million years to as little as 10-15 million years ago (it's still there in the northernmost part of the state). The destruction of the subduction zone was the origin of the San Andreas fault, which lies just offshore of here.

If you are looking for the white sand beaches of the Bahamas or Florida, you won't find them in this part of California. Those beaches are made of quartz grains or coral fragments. In Northern California, the sand is composed of the same grand selection of minerals that are found in the rocks of the nearby cliffs, and almost any color can be picked out of a handful (for my sed-pet friends, yes, this is a gravel, not a sand sample; but it shows the colors better!).

An exploration of the roads around the tops and sides of the seacliffs reveals a bunch of strange looking concrete structures that are clearly old, and clearly abandoned. It turns out that if the Japanese Navy had ever decided to enter San Francisco Bay to cause havoc during World War II, they would have faced a devastating barrage of artillery fire coming from these concrete bunkers.

Today, these cliffs and rocky islands are home to hundreds of thousands of birds. The Marin Headland, clear-cut of lumber in the 19th century, covered with structures of war in the 20th century, is now a place of tranquility and contemplation. Sometimes we do a few things right...

I love California...