The Other California: For a time it was the Black Golden State

Talking about oil drilling in California...is that like kicking a beehive?
Picture of beehive in an old oil well taken by Mrs. Geotripper

We drill into the earth to find oil.

It is a measure of our dependence that we also fight wars over it, support vile dictators, and drill for it in the harshest conditions on the planet: in arctic tundra, in isolated deserts, and deep ocean basins. We end up dealing with huge environmental consequences as we attempt to clean up our spills and as our planet warms up at an unprecedented rate.

I can see where it once made perfect sense to go all in with oil and gas. No one knew of global warming and greenhouse gases, and in some areas the oil seemed practically as plentiful as water. It made sense when it was cheap and easy to get.  But now it is different. Oil is expensive, but it is so completely integrated into our economy that we can't easily wean ourselves from it.

California was once one of those places where the oil seemed to flow like water. The freeway economy and near total lack of public transit in the southern California metropolitan area was a consequence of the vast amount of oil that was once drilled in the Los Angeles basin. Fuel was easy to get and cheap to purchase.

From the 2009 Annual Report of the California State Oil and Gas Supervisor

Things have changed in a radical way. California produced 230 million barrels of oil in 2009, fourth in the country after Texas, Louisiana and Alaska. But oil drilling in the state is in a long-term decline; the last time our state produced oil at a level this low was in 1941. But the state uses something on the order of 700 million barrels of oil each year. Nearly two thirds of our oil has to come from somewhere else.

I didn't know a lot about the story of California oil, but a possible opportunity to lead a field trip with foreign oil geologists popped up last summer. I hit the road (and the books) and found myself in the Santa Clarita Valley discovering the site of the state's first gold rush, and some of the oldest rocks. I also stumbled across a historic oil well. Not only was it the first commercially successful oil well in California, it was also the longest continually operating oil well in the world, pumping oil from 1876 to 1989 (a similar claim is made about a well in Pennsylvania, though). It was Pico No. 4.

Equipment has been removed throughout Pico Canyon, but the well casing was kept at Pico No. 4 because of the historic nature of the well. A historical monument can be seen in the background.

Pico No. 4 was not the first attempt at oil drilling in the state. The remote village of Petrolia in northern California was the site of a drilling attempt in 1861, but the oil was very quickly depleted. Other attempts were made in the 1860s, but none were successful until Charles Mentry started drilling a series of wells in Pico Canyon. The fourth well proved successful, and the production began. The town of Mentryville popped up in the lower part of the valley.

The oil drilling took a toll. When production started to fall, wells were abandoned, villages turned into ghost towns, and equipment littered the canyon. Eventually Chevron pulled out of the region entirely, but they clearly made an effort to clean up some of the worst of the damage, and turned the land over to the Santa Monica Mountains Conservancy. Pico Canyon is now a parkland, and it is a surprisingly pleasant place to visit, given the checkered history of our abuse of the landscape.

There is a modest fee for parking at Mentryville, and the "trail" leads up the canyon through the chaparral covered slopes and riparian woodland. Although the road is paved for a mile or so, the gates are locked, so you will see bikers, joggers and hikers, not cars.

The slopes are made of sedimentary rocks that formed in Pliocene time, mostly within the last 5 million years in a shallow marine environment. The exposed formations include the Pico Formation and the Towsley Formation. The rocks are steeply tilted, but at the head of canyon they fold over, forming an anticline that served as the oil trap. Around eighty wells were once present in the upper canyon.

It was an enjoyable stroll, even though the late August day was pretty hot. It was nice to find some occasional trees shading the road.

I found myself wondering how many wildflowers can be seen during the spring. It must be quite a show!

My time was limited, so I turned back at the end of the pavement. Trails continue beyond into adjacent canyons allowing for a number of choices in hiking destinations.

We wandered back down to Mentryville and looked at some of the buildings, and then headed back out to the highway.

The ghost town of Mentryville still has a few buildings.

The thought that occurred to me as I walked back down the canyon is that given enough of it, time does heal some wounds.

The Other California: The Oldest Rocks (well, maybe...)

Part of the mystery question I asked the other day suggested that the oldest rocks in California lie within a few miles of the Santa Clarita Valley. I kind of knew I would be opening a can of worms by pointing this out, and I will try to explain why this idea might be ambiguous at best, and highly controversial at worst. In essence, yes, some of the oldest rocks found in the state are found there, but defining how 'old' a rock is can be a real conceptual problem at times.

It wouldn't be that much of a problem if the rocks in question were volcanic or plutonic. Such rocks are usually ideal candidates for radioactive age dating. The rocks form by cooling from hot magma, and crystallization is either instantaneous (in the case of volcanic rocks), or takes place over several thousand years (as in plutonic rocks cooling deep underground). As the rocks crystallize, they trap small amounts of uranium, rubidium and other radioactive elements in a solid atomic prison. Isolated from weathering and other chemical changes, the radioactive substances start to decay at extremely regular rates, and the original material begins a very slow transformation to daughter elements like lead and strontium, or argon (in the case of radioactive potassium). By analyzing the proportion of daughter element to parent element, the age of the rock can be precisely determined. Because several methods can be used to date a single sample, results can be cross-checked for accuracy

A side note: Carbon dating is another form of radioactive age dating that is recognized by many people, if not well understood. It is rarely used in geology because it only useful in materials that are less than 100,000 years old. Since it is carbon-based materials like bone or wood that can be dated, the method is favored by archaeologists who are working with artifacts.

The problem comes when such rocks undergo metamorphism, that is, when they are changed by heat and pressure into new kinds of rock like gneiss, schist and marble. The heating in essence allows daughter elements to migrate out of the crystals and the radioactive 'clock' is reset to zero. If you age date metamorphic rocks, your results tell you when the rock was metamorphosed, not when the rock originally formed. This kind of information is critical to understanding the tectonic history of a region, but it isn't the age of the "oldest rock".

There is an additional complication. There are a few minerals that are not affected by the heat of metamorphism, including a mineral called zircon. When zircon crystals are present in a rock undergoing metamorphism, their 'clock' is not reset. So depending on which minerals are dated, you get the age of the metamorphism, or the age of the older zircon crystals. It gets even more tricky: zircon is also tough enough to survive erosional processes. So even though you can figure out the age of crystallization, the date you get may have come from the original plutonic rock, but it tells you little about how many cycles of uplift and erosion that the zircon may have gone through.

So there you go...it turns out that the "oldest rocks" in California can be found over a rather wide area. There are rocks that date to 1.7 or 1.8 billion years ago in Death Valley National Park, in the eastern Mojave Desert, in Joshua Tree National Park, and the San Gabriel Mountains, which form the eastern edge of the Santa Clarita Valley. Most of the rocks were part of a vast mountain system that developed in a series of terrane collisions as the supercontinent that we call Rodinia came together (here is an excellent overview if you want the gory details of the story). As I walked through Placerita Canyon, I was very close to exposures of the Mendenhall gneiss, which is dated, like the others, at 1.8 billion years.

Before calling this oldest rocks "contest" a tie, we should point out that the ancient rocks in the Basin and Range and Mojave Desert are part of a Proterozoic terrane called Mojavia, which has zircon dates that extend back to 2.5 to 2.7 billion years, and as far as I know such results have not been found in the San Gabriel Mountains terrane (but as always, I am welcome to correction!).

I wandered through the terrain around Placerita Canyon taking a look at some of the metamorphic and plutonic rocks of the San Gabriel Terrane (yes, terrain and terrane mean two different things; the first referring to the shape of the surface of the land and the other to the underlying crust). I haven't lived in Southern California for nearly a quarter century, but I immediately felt at home. The dry chaparral slopes and the oak and sycamore filled canyons were the places that I grew up in, poison oak and all. If trails weren't present, access was problematic. I had a number of memorable trips where I was climbing slopes using the bushes as a ladder. The San Gabriel Mountains are statistically the steepest mountain range in the world and I find that easy to accept. It is a wonderful place to explore.

One really big change, though: in the 1970s, when I was a budding geologist, the rocks of the San Gabriel Mountainswere mapped as "metamorphic-undivided" and were poorly known. Today there is a richness of data that allows us to see the role of the rocks in reconstructing the American West of nearly 2 billion years ago.

The Other California is my continuing series highlighting the geology of the fascinating places in my fair state that don't often show up on the postcards that tourists buy. The state is a big place and I have yet to see it all, so if you have a favorite corner of the state and would like to put together a blog entry, I would gladly add it to the series.

The Other California: Dreams of Avarice and the First Gold Rush

The Santa Clarita Valley is a suburb north of the San Fernando Valley, a place one drives through while following Interstate 5 to other places. I've been through it dozens of times on my travels, but I haven't usually had a lot of reasons to explore the place. It seems like the whole valley consists of new housing developments and fast-food rows. Oh, and Magic Mountain Amusement Park. But that's the thing about the Other California. There are always surprises in this state, no matter where you go. The strangely sloping hills and rugged mountains that ring the valley hide some interesting secrets.

Yesterday's post was a mystery question, and as the commenters correctly surmised, the Santa Clarita Valley is the location of four very intriguing geological sites. Stay tuned for the other three in coming blog posts. Today I want to talk about the very first gold rush in California's history.

Most people in our state are familiar with the Gold Rush, the one in 1848 in which James Marshall discovered flakes of gold in the Sierra Nevada foothills at Coloma while building a sawmill for John Sutter. The forty-niners. The Mother Lode. Black Bart and Joaquin Murrieta. Fewer people realize that this seminal event was actually the second gold rush in California's history.

Before the Mexican-American War, California was still part of Mexico, and large ranchos had been established in many parts of the territory. The Del Valle Rancho was established on 48,000 acres of the Santa Clarita Valley in 1839, under the ownership of Antonio Del Valle. In 1842, his brother-in-law Francisco Lopez y Arbello was taking a nap under a large oak (reputed to be the one in the picture at the top of the post) during which he dreamed of being surrounded by gold. A short while later he pulled some wild onions out of the ground, and found gold flakes adhering to the roots. California's first gold rush had begun.

Compared to the one that followed in 1848, the rush was relatively inconsequential. The Mexicans were not very interested in advertising the find to the world at large, and the gold played out after only a few years. It did however mean that Mexicans who were familiar with mining methods were situated just a few hundred miles from the Sierra Mother Lode. They played an important role in many of the early gold discoveries in 1848 and 1849.

The discovery site is now preserved as Placerita Canyon State Park just off Highway 14 near the town of Newhall. There are few signs of mining left, but the canyon is a pleasant place to explore. We saw woodpeckers and hawks during our short visit. Los Angeles County Parks administers an excellent nature center with an unusually detailed display of the local rock types. A nice network of trails can be followed, including a paved handicapped accessible trail to the Oak of the Golden Dream (top of the post).

Speaking of golden dreams, keep your eye on the north side of the road as you return to Highway 14. Ensconced in the oak woodland you will see a somewhat bizarre looking development. This is the Golden Oak Ranch, a permanent movie set that has been owned by the Disney Corporation since 1959. Even though you can't visit the place, you've probably seen it many times over in the movies. And if you make movies, you can rent the ranch!

This link to the California Geological Survey has the classic story of the California's gold rushes, originally published in the 1948 Geologic Guide to Highway 49. In the next post we will take a closer look at the rocks in Placerita Canyon. It turns out they are kind of old. Well, really old.