Where the Sierra Nevada Rises From the Sea: A Compilation of Posts

The Sierra Nevada of California is one of the great mountain ranges of the world. The soaring granite peaks, the deep glacial valleys, and the towering Sequoia trees represent some of the most beautiful sights to be seen anywhere on the planet. What is less known is that a portion of the Sierra Nevada is present elsewhere in the state. Around 30 million years ago the San Andreas fault system became active and sliced off a portion of the southern Sierra Nevada batholith and carried it northwest for several hundred miles. It now makes up a considerable portion of the Central California coastline, stretching from Big Sur on the south to Bodega Bay on the north. It is in my humble opinion one of the most beautiful and dynamic coastlines to be found anywhere on planet Earth.

I recently finished my latest blog series, and I present here a compilation of the fifteen entries in the series. If you missed any, here is the place to find them!

  Seeking Geology Along the Most Beautiful Coast in the World

A sneak peak at the coming series. At this point I hadn't fully appreciated that I was going to be covering the entire Salinian Terrane, so I didn't mention the Sierra Nevada connection in the first post.

Where the Sierra Nevada Rises From the Sea: The Big Sur Coast

With the second post I hit upon the idea of the Sierra Nevada connection with my exploration of Limekiln State Park in the southern part of the Big Sur coast. It is a stunningly rugged stretch of coastal cliffs, and amazingly, the state of California almost shut down this beautiful place.

Geologic Change along the Big Sur Coastline: Julia Pfeiffer Burns State Park

I punted on this one. I wrote this blog four months earlier about what may be the prettiest cove along the prettiest coast in the world. But the post fit well with the theme and scope of this series, so here it is: one of California's two tidal falls. And gigantic landslides.

Pfeiffer Big Sur State Park

A short distance inland from the coast we discover a gem of a state park, Pfeiffer Big Sur. The Sierra Nevada has the Sequoia trees, Big Sur has Coast Redwoods. And both the Sierra Nevada and Big Sur have huge wilderness areas. The wildlands around Big Sur are far less crowded.

Not the Easiest Beach to Find

Big Sur has some nice beaches, and not all of them are on the main highway. You have to be a bit of a sleuth to find Pfeiffer Beach, but it's worth the effort. And...garnet sand beaches!

The Granitic Rocks of Garrapata State Park

One of the lesser known beach parks of the central California coast, Garrapata is a beautiful place that belies its horrendous name ("tick" beach). It has some of the nicest exposures of "Sierran" granite in the region.

Sea Wolves and Underwater Yosemites

Point Lobos was named for the seals and sea lions, not for terrestrial canines. It is another gem along the coast with unique exposures of conglomerates that accumulated in deep underwater canyons that rival Yosemite in their depths.

A Quick Explore of the Monterey Peninsula

We finish our journey through Point Lobos and move north onto the Monterey Peninsular. Here it is trees that take up some of the geologic story. Monterey Pines grow naturally only in a few places, mainly on the Peninsula, but have become one of the most widely planted trees in the world. The Monterey Cypress is another unique species in the region.

Half Moon Bay

We take a look at coastline of totally different character as we reach the Half Moon Bay region. There are prominent marine terraces that make for gentle scenery (and apparently great golf courses). There are some nice tidepools in the area, and during the right time of year, the Mavericks hit, the gigantic waves that bring surfers from around the world.

Little Boxes on the Hillside, Little Boxes Made of Ticky-Tacky: The Mess at Mussel Rock

The San Andreas fault looms large in the history of the Central California coastline, but hasn't made an appearance on our journey until now. At Mussel Rock in Daly City, the fault trace moves offshore. The epicenter of the 1906 San Francisco may have been close by. And there is a famous folk song about the cookie-cutter houses on the high, unstable slopes...

Some Call it the Golden Gate...

Maybe you haven't heard that there is a big bridge that connects the city of San Francisco with the Marin Headlands and the rest of Northern California. It's not likely, but it's possible. There is some interesting geology going on underneath the bridge abutments.

On the Most Inaccessible Mountain Range on the Planet: The Marin Headlands

The Marin Headlands expose rocks that were once part of the midocean ridge, the vast planet encircling mountain range that no mountain climber can ever hope to climb. The scenery on the Marin is majestic. And to invaders in World War II, the cliffs would have been deadly.

Point Reyes National Seashore

The Point Reyes Peninsula has wide sandy beaches, sand spits, a bay that may have been a landing for Sir Francis Drake, Tule Elk, and a lighthouse that has to put up with some really rotten weather.

Tomales Bay and Bolinas Lagoon

If the Point Reyes Peninsular bears the brunt of violent Pacific Storms, the mountains of the peninsula shelter the lands to the east. Two bays along the San Andreas fault are peaceful and serene, which belies their violent origin.

Birds and a Hole in the Head at Bodega

We wrap up our exploration of the Sierra that rises from the sea with a look at Bodega Head, the site of a classic horror movie, and a horror story with a nuclear reactor as the main character. A reactor that was almost built on top of the San Andreas fault. It's also the northernmost exposure of the Salinian/Sierra Nevada rocks.

Where the Sierra Nevada Rises From the Sea: Birds and a Hole in the Head at Bodega

Sea stacks at Bodega Head, with the Point Reyes peninsula in the distance

We are reaching the end of my series on the Central California coastline from Big Sur to Bodega Bay. I've been calling the series "Where the Sierra Nevada Rises From the Sea" for a very specific reason. Much of this section of the coast is composed of granitic rocks that formed in the subduction zone complex that was the origin of the Sierra Nevada batholith, the 400 mile long block of granite that is the backbone of California. The rocks, known as the Salinian Block (or Terrane), have been displaced hundreds of miles northwest by lateral motions along the San Andreas and related fault systems over the last 30 million years or so. Bodega Head is the northernmost exposure of these granitic rocks.

Bodega Head refers to the former island of granitic rock that is now connected to the mainland by a large area of active and stabilized sand dunes. Bodega Bay formed between the head and the mainland, and is nearly closed off on the south side by a sand spit along Doran Beach. A small marina is here and a modest fishing fleet works out of the harbor.

No, this isn't a bird attack at Bodega, but I sure thought about it while I was snapping this shot of Red-wing Blackbirds at San Luis National Wildlife Refuge near Los Banos in the Central Valley.

One may not know Bodega for the geology, but there are those who will remember Bodega Bay as the setting for a rather famous movie about our avian friends, The Birds, Alfred Hitchcock's classic. The original house where many scenes were shot is gone now, but the cypress grove where the house stood can be seen on the sand bar that connects the Head to the mainland. The land is owned today by the University of California, which runs a research facility at the site (occasional tours are offered).

Bodega Head has a horror story that may be the equal of an unexplained attack by our feathered companions. The rock sequence found east of the San Andreas fault is part of the Franciscan Complex, and these rocks are notorious for their slope-failure tendencies. Mass wasting is a way of life for anyone who chooses to build on it. Bodega Head on the other hand is composed of hard granitic rock. No slope failures would be expected there.

The Hole in the Head

So it was that in the 1950s that PG&E looked with great longing at the granite headland and decided that Bodega Head would be an ideal spot for a brand new nuclear power plant. The water they needed was there, there was solid ground to build on in contrast with the lousy slopes east of the fault in the Franciscan Complex. And not that they thought of things this way back then, but the site was fairly isolated from large population centers in case of bad accidents (which we all know NEVER happen with nuclear power plants).

And adjacent to the San Andreas fault! Its not like they didn't know it was there. In 1906, this part of the San Andreas shifted 15 feet or more. So they began digging a hole that would serve as the foundation for the power plant. As the plans and excavations progressed, local opposition began to grow, and ultimately the company somehow realized they were about to put a nuclear reactor practically on top of the San Andreas fault (subsidiary faults were discovered in the excavation pit; a geologist opined that “a worse foundation condition would be tough to envision.”). The pit became known as the "Hole in the Head".

So the nuclear power plant was never built, and Bodega Head remains as barren windswept ridge with beautiful cliffs composed of the northernmost exposures of the granitic rock of the Sierra Nevada. The Hole in the Head filled with seeping groundwater that now supports the local wildlife.

And so ends our little series of a part of the Sierra Nevada mountains that rise from the sea. I hope those of you who've followed it enjoyed the journey. I'll be putting up a compilation of the different posts in the series since it has been a rather off and on project over the last three months!

Hitting the Road, Going to Unexpected Places

Thanks to the obstructionist party in the House of Representatives, we've had to completely retool our last overnight field studies trip of 2013. We had planned to explore Sequoia and Kings Canyon, but with the absolutely wrong-minded shutdown of the federal government, those parks are closed.

Luckily, even though the state of California flirted with the idea of closing her state parks, they are open for business, so we will be exploring one of the greatest stretches of coastlines in the world, the one between Big Sur and Bodega Bay. There just isn't any place like it anywhere.

It's been a while (like never) that I've had to plan and conduct a three day trip with three day's notice. I started from scratch, but I think we've got an ambitious itinerary that is flexible, and bound to be fascinating no matter where we go.

I will let you know how it worked out in a few days!

In the meantime, contact your representative and tell them to stop holding the government hostage. The fools in Washington have officially failed basic civics and political science. You don't get your way by tossing hundreds of thousands out of work, and taking food from children and the elderly (including the veterans).

The Other California: I Need This Like a Hole in the Head

What happens when profit motive collides with good science? I dunno, I'm on vacation!

We escaped the heat of the Central Valley yesterday by taking a drive up Highway 1 from Bodega Bay to Fort Bragg. Bodega Bay is formed by a prominence called Bodega Head that would otherwise be an island, except that sand has linked the island to the mainland and in the process formed a small protected harbor. The Head is a beautiful stretch of coast, with some stunning seacliffs and sea stacks on the Pacifc side.

Many of the seacliffs in this part of the state are formed out of Franciscan sediments or Neogene sandstones, so the cliffs at Bodega Head stand out. They seem steeper and more resistant. A quick look at some boulders at the top of the cliff soon make it clear why:

The rocks are made out of granite! Or, to the geologists eye, a granitic gneiss (note the lineations in the boulder above). These rocks have undergone some stress. The granite seems a bit out of place considering the big California picture; we tend to associate granite with the Sierra Nevada or Southern California, not the North Coast.

Which brings me to this scene, from the bay side of the Bodega Head. There is a quiet little freshwater pond, surrounded by thick vegetation. There was a gathering of egrets in the trees, and despite the season, wildflowers were in abundance. It was a serene setting.

What wasn't clear from the ground perspective is the pond is rectangular. It's artificial, having been dug out of the solid granite, but it was abandoned for some reason and left to be reclaimed by nature. Groundwater maintains the water level. So what happened here?

It turns out that in the late 1950's, an electric utility wanted to build a nuclear power plant on the site. The granitic rock would provide a firm foundation, there was a plentiful supply of water for use as a coolant, and the site was close enough to the Bay Area that transmission infrastructure costs could be kept low. What could go wrong? So they dug this hole to prepare the foundations for the nuke plant.

What could go wrong? We need to ask again what granitic rock is doing here. It is indeed out of place, for this rock originated to the south. At least 200 miles south! It was split off and carried north, 10-20 feet at a time during major earthquakes. There have been perhaps 100,000 of these earthquakes in the last 15-20 million years. As we look across Bodega Bay in this last photograph, we come to realize that Bodega Head lies on the Pacific Plate, while the town of Bodega Bay lies nestled on the North American Plate. The San Andreas fault passes within a few hundred yards of the chosen site for a nuclear power plant!

It is said that local opposition led to the abandonment of the project. Maybe. I've heard that they found evidence of active breaks in the granite within the pit. In any case, it never got built, and today the locals refer to the pond as the "Hole in the Head".

The Other California is a series of blog posts highlighting the kinds of places and features you don't find on the postcards of our beautiful state.