Thursday, May 6, 2010

The Other California: A Gorge Deeper Than Grand Canyon

Welcome to the Other California, an exploration of the geologically fascinating places in our state that don't normally show up on the postcards.

Imagine a canyon one or two thousand feet deeper than the Grand Canyon, twice as deep as Yosemite Valley, a glacially carved trough surrounded by dramatic mountain peaks reaching almost 14,000 feet into the sky. A canyon filled with remarkable exposures of granitic and metamorphic rocks that serve as a microcosm of the geology of the entire Sierra Nevada. Such a canyon would be Pine Creek, on the eastern side of the Sierra Nevada a few miles northwest of the town of Bishop. It's a spectacular place to visit and appreciate geology.
A paved road provides easy access to many of the most outstanding features, but despite the incredible scenery, this canyon has no campgrounds, no roadside stops, no picnic areas, and no resorts. Nothing more than a small pack station at the head of the canyon. What's going on that such a place could be ignored?
I suppose it has something to do with the exposure seen below. What can be seen on this stunning cliff is the contact where the massive granite intrusions melted and forced their way into the previously existing sedimentary and volcanic rocks. The older rocks formed in Paleozoic time, around 300-400 million years ago, while the granitic rocks intruded around 100 million ago. Why would this cause tourists and explorers to ignore this place? Mineralization would be the answer. Silica-rich liquids from the magma forced their way into the metamorphic marble, reacting and forming ores of tungsten, molybdenum, and copper. This canyon was for many years a major mining center, and huge trucks were constantly driving the canyon road, which kind of interrupted the communion with nature that other visitors might have been seeking.

I walked through the area in 1975 on a trek from Yosemite to Mt. Whitney. It was kind of jarring to hike through a beautiful canyon and end up in the middle of a dusty mining complex. I'm not one to say that all mining is evil and environmentally terrible. I don't see a lot of use for gold, for instance, but tungsten was used to make the filaments in incandescent light bulbs, and I used those (it is used in wartime for armor plating on tanks, and armor-piercing bullets). If we use a resource, we have to make choices about how we will get it. We would hope as a society that the mining is done in such a way as to avoid the worst impacts (offshore oil drilling comes to mind...) on our environment.
The Pine Creek Tungsten Mine was an extraordinary operation. Begun in 1918, the mine operated until 2001, producing (along with the Climax mine in Colorado) 93% of the tungsten produced in the United States as of 1977. Low cost imports led to the mothballing of the mine in 2001 although the operation remains in place should prices rise, or strategic concerns cause an increase in demand for domestic sources of tungsten (China provides most of our tungsten at this time). The main ore is scheelite, a calcium tungstate mineral that is notable for its intense fluorescence in ultraviolet light.
The mine itself was a technological achievement. Most mines go down into the ground, but the ore here extended to 12,000 feet up into the adjacent peak. Miners could enter the mine at 8,000 feet and work some 4,000 feet higher up in the mountain.
There is lots more to see in the canyon, including the outstanding basaltic dikes that cross the granitic rocks. The granite cliffs soar thousands of feet above.
If you ever have a need to explain the term talus to someone, you can't get much of a better example than the one seen below at the entrance to the main gorge. The slopes are made of jointed granite, and whenever temperatures drop below freezing, ice can form in the spaces, pushing the rocks apart and down the steep slopes.
The U-shaped trough and hanging valleys of Pine Creek bespeak the passage of glaciers. Pine Creek Canyon is one of the classic localities for understanding the sequence and intensity of glaciations in the Sierra Nevada. It is one of the southernmost sites in the Sierra Nevada where the Tioga (14,000-28,000 years) and Tahoe (135,000-165,000 years) glaciers extended beyond their canyon and onto the adjacent valley floor. The picture below shows a ground view of the prominent lateral moraines, but the relationships are far clearer from above, as seen in the GoogleEarth image below.
One or more major earthquakes have struck within the last 14,000 years, because the young Tioga moraines are offset several tens of feet where the fault crosses the canyon entrance (marked below). Earthquakes are a serious threat in the Owens Valley; one of the biggest to ever hit the state in historic time was the Lone Pine Earthquake in 1872. It killed 28 people, and knocked rock pinnacles loose as far away as Yosemite Valley (as memorably noted by John Muir: "It is always interesting to see people in dead earnest, from whatever cause, and earthquakes make everybody earnest").
Don't be put off by the presence of a shuttered mine! Pine Creek is a great place to visit, for the scenery, and for the geology (it was a main stop during our recent NAGT-NESTA field conference). Several trails start at roads end, including Pine Creek Pass which provides access to the John Muir Trail and the western Sierra Nevada.

A geologic map of Pine Creek can be found here:

Postscript (12/6/11):

A former employee at the Pine Creek Tungsten Mine, John Sullivan, saw this post and sent me a note relating his experiences working in the mine. He has graciously allowed me to reproduce his narrative, which appears below. Thank you very much, John!

"I recently discovered on your web site your fine description and photos of Pine Creek canyon and information on the mining operation once there. Amazingly, until reading your site, I did not know of the canyon’s remarkable depth statistic even though I lived in it (at the mining camp Scheelite on your map) while in grammar school in the 1950s and later climbed to the top of Mt. Tom (on the south side) and stood atop Wheeler Ridge (on the north side). Your site brought back a lot of memories.

When a house became vacant, my family moved from Scheelite down to Rovana (the major company housing) not far below the canyon mouth. My mining engineer father who leaned toward chemistry oversaw the project that developed a way to make purer tungsten concentrate at the mill.

In the summers after I turned 18 I worked at the mill (on the “bull gang” and helped run the warehouse). Later I spent summers and Christmas vacations at the mine as an engineer and geologist’s aide, helping measure the “cubes broke” each week by the two-man drilling teams (they were paid as “gypo miners” by the cubic foot of ore they brought down or the progress they made advancing a new drift). With the geologists I helped map the underground ore body –the “Pine Creek Pendant” – contact zone as it ran upward. Some days we’d be outside, 4-wheeling then hiking up to map the contact where it reached the surface of Wheeler Ridge. While surveying, you could look up from the transit east over the White Mountains into Nevada, north and south along the crest of the Sierras, at the imposing Bear Creek Spire to the west, and down at Round Valley where we’d gone to grammar school and further out to Bishop in the haze of the little sawmill’s smoke.

I’ll never forget being underground on mornings after blasting, first using a heavy “slag bar” to bar down dangerous loose rock* from the “back” (top) of the drifts and stopes, then washing off the muck and dust with a high-pressure water hose and being the first person on earth to see a new underground scene – quartz crystals, slippery molybdenite, rust brown tactite, patches of white scheelite that would fluoresce later under the geologist’s lamp. We’d go back out to the“engineers shack” and spend the next day drawing maps, merging our underground measurements with those from diamond drill cores so the geologists could keep the mining efficiently aimed upward

Home, down at camp, trucks crawled up the road day and night, hauling ore to the mill from little mines all over eastern California and Nevada. Buses went “up the hill” with men working at the mine and mill three shifts a day, seven days a week. Hardly any of our mothers worked outside the home. It was a prosperous time. It was hard rock mining. Sierra mining."

*My buddy Ron with a couple of beers after work liked to recite a slightly lyrical admonition from the company underground safety regulations:“…if you find loose rock, bar it down. If you can’t bar it down, stull it up. If you can’t stull it up, blast it down." He did become a mining engineer.

John H. Sullivan, Sacramento


Callan Bentley said...

Cool. There's a nice normal fault scarp cutting the northerly moraine, too.

Silver Fox said...

A very neat canyon!

Gold's primary uses are jewelery and financial, but it is also used in the laptop on which I'm typing this comment, and in other electronics, among other things.

Garry Hayes said...

It's true gold has some important uses; there is a fair amount of it in my mouth, for instance! But the primary use, as you say, is financial and in jewelry, and the search for it in the California Mother Lode has left a heritage of polluted river valleys and lost agricultural lands. As I said in the post, we have to make choices. The circumstances are certainly different in NV, where agriculture is not as feasible as a choice for land use.

Silver Fox said...

You've written a lot of good info about the hydraulic mining aspect of things - and I never really thought of it in terms of lost ag land, even though I used to live in the valley. Maybe I've been in the desert too long!