Thursday, May 29, 2014

Headed for the Hinterlands: Basin and Range and the Colorado Plateau.

Hitting the road tomorrow, and much looking forward to getting away for a few days. It may seem like I do a lot of traveling, and I have been, but it's mostly been day trips. We're putting in a few miles this time, heading across the Basin and Range province to an exploration of the Colorado Plateau.
If I can, I'll put in a few dispatches from the road. We'll hopefully be busy doing geology, and discovering some new vistas. I found out that my friends from SBCC will be at Grand Canyon the same time as I will, so I hope to see some familiar faces out there!

In the meantime...

Wednesday, May 28, 2014

Spring colors from Clark Fork of the Stanislaus River (in the Other California)

Pride of the Mountain (Penstomen newberryi)

Today's post is a brief collection of the spring wildflowers we saw while we explored Donnell Vista and Clark Fork of the Stanislaus River over Memorial Day weekend. As many of you know well, I'm no botanist, so I freely accept corrections to my identification of particular flower species. I spend weeks in my mineralogy labs trying to get my students to identify their lab specimens by keying them out, but they'll often go right to the book and compare their sample with pictures. So how do I identify wildflowers? Keying them out? Of course not! I go to a wildflower book and flip pages until I find a similar picture....

I've been seeing the bright pink Penstomen species Pride of the Mountain growing in granite roadcuts for years without sitting down and identifying the species (top picture). They must be pretty extraordinary because alpine granite soils must be one of the least fertile growth environments in existence. There isn't much clay to store nutrients, the growing season is very short, and the water can't persist all that long in the small granite crevices, and yet these flowers seem to explode out of the barren rock.
Pussypaws (Calyptridium umbellatum)

Pussypaws are another extraordinary survivor, growing in barren stretches of sandy granitic soil where little else can grow.
Pussypaws (Calyptridium umbellatum)

The flowers are small and the colors muted from a distance, but this trip I got down on my belly and took a closer look. From this perspective, the flowers reveal a world of color and intricate patterns.
Pussypaws (Calyptridium umbellatum)

Spreading Phlox was another flower growing in the harsh environment of granitic soils (which, by the way, is called grus).
Spreading Phlox (Phlox divaricata)

In the deep forests along Clark Fork we saw a lot of Snow Plants (Sarcodes sanguinea). These are strange organisms that have no chlorophyll and must depend on fungus in their root system to make available the nutrients they survive on. They survive off of organic material in the forest soils.
Snow Plants (Sarcodes sanguinea)

Snow Plant (Sarcodes sanguinea)

Iceberg Meadow was covered with what I think were Water Plantain Buttercups (Ranunculus alismifolius).
Water Plantain Buttercup (Ranunculus alismifolius)

And finally, we found what I think is Pacific Hound's Tongue (Cynoglossum grande) growing at the margin of Iceberg Meadow. The flowers were small, but the blue color was striking.  
Pacific Hound's Tongue (Cynoglossum grande). Photo by Mrs. Geotripper

Tuesday, May 27, 2014

The Other California: Clark Fork of the Stanislaus, a quiet version of Yosemite

It's not really fair, of course. No place is like Yosemite, and I shouldn't compare Clark Fork to Yosemite. I doubt there is anywhere in the world that can compare to Yosemite Valley with the high waterfalls, sheer cliffs and strangely shaped domes. But there are some things that are not so nice about Yosemite. It's been used and abused for the last century and a half, and today something like four million people crowd into the few square miles of valley floor. It can be noisy, smoky, and crowded. It's possible to find lonely places on the valley floor where nature still dominates, but it's not easy.
Clark Fork on the Stanislaus River is a world apart from Yosemite Valley. Like Yosemite, it was carved by river erosion, followed by glacial scouring, although not to the same depths. There are small waterfalls and cascades, but nothing like the stunning leaps of Yosemite Falls or the others.
What is there is in Clark Fork is peaceful and uncrowded serenity. A single paved road diverges from Highway 108 and follows the valley for nine miles, passing just a few organizational camps and three campgrounds. No resorts, no stores, and no crowds. We were there on Memorial Day weekend, and there were still campsites available on Saturday evening. The road ends at beautiful Iceberg Meadow, which at this time of year was filled with Water Plantain Buttercups (to the best of my guessing)

Brooding over the meadow is the unique granitic monolith called simply The Iceberg. It's 8,350 feet high. From the perspective of the meadow it looks like a prominent peak, but a look at the topographic shows it to be the last knob of a long divide between Disaster Creek and Clark Fork. Just two miles away, Disaster Peak rises 1,600 feet higher.

The peak is composed of the granodiorite of Topaz Lake, which at about 84 million years is one of the youngest granitic intrusions in the Sierra Nevada batholith (granodiorite is similar in appearance to granite, but contains more plagioclase feldspar and mafic minerals that makes it slightly darker in color). The rock is broken up into joints that are caused by pressure release when the rock is exposed by erosion. This explains the general lack in Clark Fork of bold cliffs like El Capitan or Half Dome, which are relatively less affected by jointing. The rocks of peaks like the Iceberg are more readily eroded by glaciers, which can pluck out the jointed blocks or rock.
Photo by Mrs. Geotripper

Very much unlike Yosemite, there is an abundance of volcanic rocks on the higher ridges above the valley. They are visible from various points along the road and can be accessed by trails that lead up Clark Fork and side canyons like Arnot and Disaster Creeks. Similar volcanics are found along Highway 108 near the summit of Sonora Pass. As noted in the previous post, these rocks were erupted between 10 and 12 million years from a volcanic center along the Sierra crest, similar in appearance to the Mt. Lassen volcanic complex further to the north.
We didn't have a lot of time on our visit last Saturday, but we walked around Iceberg Meadow and saw not a single other person. Cattle are still allowed to graze in the region, but the meadow itself is fenced off to preserve it from damage (deer have no problems jumping the fences). Despite the drought, the meadow is a bright emerald green in places, though in some parts it looked bluish from the impending bloom of some irises or other swamp flowers. It's only May, and it should be still partly covered in snowbanks, but we'll take the short spring over none at all. I hope the drought breaks this year...
Photo by Mrs. Geotripper

Clark Fork is a wonderful part of the Sierra Nevada, one of those largely ignored corners of a beautiful mountain that would probably be a national park in any other setting. It is the kind of place that John Muir wrote about in the Mountains of California when he said “Climb the mountains and get their good tidings. Nature's peace will flow into you as sunshine flows into trees. The winds will blow their own freshness into you, and the storms their energy, while cares will drop away from you like the leaves of Autumn.”

Photo by Mrs. Geotripper

This is one of the irregular entries in my blog series called "The Other California" which existed long before any Toyota commercials with a similar slogan. It is an exploration those places in my fair state that don't always show up on the tourist postcards, but which have incredible geology and are scenic to boot.

Sunday, May 25, 2014

The Other California: Highway 108 and Donnell Vista - like Yosemite, only with Volcanoes!

Those of you who've followed my blog over the years may remember that I produced a blog series called "The Other California" which existed long before any Toyota commercials with a similar slogan. I come back to it time and again when I find (or rediscover) those places that don't always show up on the tourist postcards, but which have incredible geology and are scenic to boot.

Today we are exploring a few corners of the Upper Stanislaus River drainage in the country north of Yosemite National Park. People from outside the region can be forgiven if they think that the Sierra Nevada is just Yosemite Valley, Sequoia National Park, and Lake Tahoe. The range is 400 miles long, and pretty much all of it is spectacular, except Yosemite and Sequoia are just a little more so. I cannot doubt that if Yosemite Valley didn't exist, the upper Stanislaus would have been one of California's national parks. In some ways, Sonora Pass and the upper Stanislaus are even more interesting in the geologic sense. The reason? Volcanoes.

Donnell Vista Point on Highway 108 about 18 miles above Pinecrest Lake and Strawberry is the site of today's exploration. The parking lot and quarter-mile trail to the viewpoint were recently renovated with funds provided by the America Recovery and Reinvestment Act. The old worn-out trail was resurfaced, and a new ADA compliant trail winds along the western part of the slope, providing some new views to the west.

The first thing one notices from the overlook at Donnell Vista is the deep U-shaped canyon occupied by the lake behind Donnell Reservoir. During the Pleistocene Ice Ages, rivers of ice repeatedly scoured the gorge below, with the last glacial stage ending only about 12,000 years ago. The ice exposed the underlying granite, forming steep cliffs and numerous small rounded asymmetical domes called roches moutonnées. Some nice examples of glacial polish can be found in the region.

The ice in most places removed a cover of volcanic lava flows and any soils were stripped away as well. As a result, wide areas of granitic rock are exposed, and the forest grows only in fractures and joints where bits of soil can accumulate.

Glaciers also scour out basins where lakes can subsequently form, but the lake below the view point is clearly not natural. It is Donnell Reservoir, constructed in 1957 by the Oakdale-South San Joaquin Irrigation district for storage of water for agricultural irrigation and power generation. It stores a bit more than 60,000 acre-feet of water which today is only used to generate electrical power. Storage for irrigation now takes place downstream in the much larger (and more controversial) New Melones Reservoir.

The high peaks to the north and east of Donnell Vista preserve the evidence of the volcanic activity that took place here 10-12 million years ago. The few remnants not stripped away by the ice form the mesa-like peaks on the skyline. When the volcanoes were active, the region would have looked a great deal like the Mt. Lassen volcanic center, which remains active today.

The lava flows filled a fault basin near the present-day Sierra Crest in the vicinity of Sonora Pass, and at times spilled over into the adjacent river valleys. One lava flow traveled nearly sixty miles to Knights Ferry in the Sierra foothills above Oakdale. The landscape surrounding the lava flow eroded away during the uplift of the Sierra Nevada block, leaving the lava flow as a prominent ridge called an inverted stream.
The upper drainage and headwaters of the Stanislaus River up to and over Sonora Pass offers up some fascinating geology. I helped edit a field guide of the geology of the region for a meeting of the National Association of Geoscience Teachers in 2012. It's for sale through Sunbelt Publications and the proceeds support scholarships for geology majors in California, Nevada and Hawaii. Get more information about the book here.

PS: Ron Schott has a great gigapan shot of the view from Donnell Vista at

Up Close and Personal with a Western Tanager

Seasoned birders won't be surprised at the excitement a rank amateur like myself feels the first time he or she sees an interesting bird up close. Western Tanagers (Piranga ludoviciana) are relatively common forest and woodland birds across the western United States and Mexico and I'm sure they are seen often by the experts.  I've only been seriously seeking out new species for the last five months, so I still get to experience the joy of seeing something new and different on a fairly regular basis as I add to the list of observed species.
I've known about Western Tanagers for a long time, but I've never been close enough with an adequate camera to actually get decent photographs of one, but that changed today. We were exploring the upper reaches of the Stanislaus River in the Sierra Nevada of California, and as I was driving down the Clark Fork Road at the end of the day, I saw a flash of yellow out of the corner of my eye. I hit the brakes, hoping against hope that I wouldn't spook the brightly colored male.
He didn't spook. I snapped a few distant shots, and then backed up the car hoping to get closer (I know that sounds like an odd way to do it, but from only forty or so feet away, getting out of the car would have spooked it more, I think). He hung around, as if he was observing me (a large rival in his territory?).
The tanagers are a large and diverse group of passerine birds centered mostly in the American tropics, but the Western Tanager ranges farther north than any other species, as far southern Alaska. For being so brightly colored, they are not often seen, as they tend to hang out in the upper canopy of the forest. I felt privileged to spend a few minutes observing this one, from basically all angles. Was he sending me a message with this last shot?

Brightly colored birds often carry the seeds of their own destruction because their feathers may be in high demand for one reason or another. Looking at the tanager reminded me of the large number of species of Honeycreepers that once existed in the Hawaiian Islands. A few of them are still hanging in there (two out of the original 51 species), but most of the others are extinct or nearly so, in part because Hawaiian royalty centuries ago demanded robes made out of their brightly colored feathers (habitat loss, malaria, and competition with invasive species and predators were major factors as well). The tanagers, with their wide range across all the western states avoided such a fate, but they were for a time considered agricultural pests and were poisoned or shot. They are protected today, and their numbers have grown to where they are a "species of least concern".

It was a privilege to see one up close and personal today.

PS: Mrs. Geotripper took a short video of the same bird...

Friday, May 23, 2014

Taking in the View from the Bay Area's Devilish "Not a Volcano"

Mount Diablo looms over the Bay Area, rising 3,849 feet above the coastal plains. The two prominent peaks are miles from any other high mountains, and thus the mountain offers an incomparable view of central California, from Mt. Lassen in the far north to Mt. Dana and other high peaks of Yosemite National Park to the south. Sitting above the Carquinez Straits and the delta of the Sacramento River, it also offers unparalleled views of the Bay Area including the Golden Gate Bridge and the skyline of San Francisco (on non-foggy days). One minor surprise: if you actually stand on the true summit of Mount Diablo, you won't see any of the things mentioned above. It's inside a building (see the picture below).

The monument in the visitor center describes the use of the mountaintop as the initial point for all of survey lines for Central California and Nevada. Any property lines using the township and range system of measurements in the region are based on measurements from the summit that started in the 1850s.
The most prevalent story of how the peak came to be called "Diablo" involves an effort by the Spanish to force members of the local Native Americans into servitude at the nearby missions. Some were hiding out in willow thickets that the Spanish called the Monte Diablo, the "devil's thicket", but the "monte" was later mistranslated as "montana".

Despite the mountain's distinctive shape, it is not volcano. Even though some of the rock making up the mountain is volcanic, it is basalt and related rocks that were once part of the ocean crust, and not something erupted from a terrestrial cone. The origin of the mountain can best be described as ocean floor crust and Franciscan trench deposits breaching the Earth's surface like (oh, geologist friends forgive me) some gigantic Godzilla character in a movie. Described more properly, the rocks from deep in the crust have been thrust upwards along active compressional faults.
A rather narrow and exciting road climbs to the summit of Mt. Diablo, the centerpiece of Mt. Diablo State Park. The summit building contains a visitor center and store, and includes an observation deck. Trails lead out in several directions from the summit, but one, the Mary Bowerman Nature Trail, circles the summit in about 0.7 miles.
North from the summit, the hills drop away rapidly to the Sacramento River and Carquinez Straits, where about 60% of all of California's fresh water flows. 32 of the 35 islands in the delta have subsided to below sea level. They are protected by poorly designed levees that are a century or more old. If a moderate earthquake strikes on one of the nearby faults, liquefaction will cause widespread failure of the levees, and the delta will be flooded with salt water. The California Water Project will be shut down for many months while the delta is slowly flushed out. The implications for water deliveries to the San Joaquin Valley and Southern California are frightening.
An odd sight is visible just to the north, the large open pit mine called the Mt. Zion quarry. The basaltic diabase is some of the oceanic crust mentioned earlier. It is a tough and stable rock, useful for breakwaters, road beds, and railroad lines. Note how the quarry lies on the ridge side opposite of the suburban developments of Clayton. Out of sight, out of mind...
North Peak is about a mile northeast of the main summit, and only about 300 feet shorter. Like the main summit, it is composed primarily of rugged Franciscan chert. Chert develops on the deep ocean floor as myriads of one-celled creatures with silica shells sank to the bottom and became more compacted (diagenetic alteration). The rock was carried on the Pacific Plate for thousands of miles before being scraped off in the subduction zone along the western edge of North America.
 The view to the east and southeast reveals my home. It's flat. They grow lots of stuff there.

Actually though, the oak-covered ridges in the foreground reveal something of interest. The Great Valley is a deep trough with upwards of 25,000 feet of sedimentary layers dating back to the Mesozoic Era, the age of the dinosaurs. We would know little about them except that along the eastern Coast Ranges, the sediments have been curled upwards and exposed by erosion. The rocks surrounding the core of Mount Diablo are in fact called the Great Valley Group, and they contain a rich fossil record, including plesiosaurs, ichthyosaurs, mosasaurs, and even an occasional dinosaur bone.

The easternmost section of the trail offers an excellent exposure of the Franciscan chert called the Devil's Pulpit. No one walking by was able to resist the temptation to climb it, including me!
The southern flank of Mount Diablo was burned last September. With the horrific drought, regrowth of vegetation has been limited, but there were lots of interesting flower species. The views included the Livermore Valley and the South Bay. A short distance later, I reached the end of the trail and we headed down the mountain. We made one more stop, at the very cool sounding Rock City.
After visiting with the resident raccoon, we set out to explore the bizarre rock exposures. We were looking at the Domengine Sandstone, a coastal estuary deposit that included extremely pure quartz sandstone and low grade coal called lignite. Earlier in the day we had explored one of the coal mines at the Black Diamond Mines Regional Preserve.
We made our way through a warren of criss-crossing trails and followed a sandstone ridge to Sentinel Rock. It is an eerie landscape, but it's also a lot of fun to explore.
Knowing that Sentinel Rock would be an irresistible but dangerous climb, the park administration installed cables and carved out steps.

Mt. Diablo State Park is an absolutely fascinating and beautiful island of wilderness in the midst of the Bay Area. It is a great place to visit, and a marvelous geological wonderland. If you are ever in the region, check it out!

Wednesday, May 21, 2014

Through the Looking "Glass" and into the Rabbit Hole: A Tour of the Black Diamond Mine

Coal mining...

Barren open pits, overburden stripped away, ruined rivers, flattened mountain tops. It doesn't have a very good reputation and probably doesn't deserve it. Yet even today it provides a significant part of our energy mix, despite the destructive effects it has on our atmosphere, land, water, and the lives of the miners themselves. A hundred years ago it provided much more of our energy.

California doesn't have much of a reputation for coal mining. During the middle and late Paleozoic, when widespread parts of the eastern United States and parts of Europe were covered by forests, swampls and coastal estuaries, California was pretty much underwater, and no major coal seams ever formed.

The situation was a little different about 50 million years ago. The Ancestral Sierra Nevada, the mountains that formed while granite was cooling deep in the Earth, had been worn away, and the modern Sierra Nevada had not yet begun rising. Large meandering rivers coursed across the landscape, bringing sediments into the coastal complex from sources as distant as central Nevada and Idaho. A shallow sea filled the forearc basin that paralleled the Pacific coast, and along its margins there were beaches and barrier islands, along with coastal estuaries and jungles of tropical vegetation. The river and coastal complex formed a sedimentary layer called the Domengine Formation (in the Sierra Nevada foothills, it is known as the Ione Formation and the Auriferous Gravels). It was here that coal formed in California. It was a low-grade form of coal called lignite. It had none of the quality or energy content of  bituminous or anthracite coal, but it was close to San Francisco, and it was the only coal for hundreds, even thousands of miles. Coal mining began in the Coast Ranges above Antioch in the 1850s, eventually producing four million tons before shutting down around a half century later. Several thousand miners and their families lived in five villages in the immediate vicinity, and dug miles and miles of tunnels into the hills (I've heard of upwards of 200 miles of passageways).

The towns faded away and many of the underground workings collapsed. In the 1920s, a new resource was being mined here: sand. Sand? What in the world for? For glass-making. It turns out that the sandstone of the Domengine Formation is very pure, almost 100% quartz. If you've ever stood on a sandy beach in California, you would know that the sand in the state is usually gray or brown in color because of the many other minerals that are present. It's only sands that have been transported along lengthy rivers and deposited in coastal regions where they would be washed back and forth for millennia that they reach that level of purity. Those were the conditions present as the Domengine was being laid down 50 million years ago. Glass mining took place through the 30s and 40s, and ultimately 8 miles of huge tunnels were excavated. That's a lot of glass bottles...
California paleogeography from interpretive signs at Black Diamond Mines, mapping by Ron Blakey of Northern Arizona University

So it was that last Saturday, the Geology Club at my college finally conducted their semester field trip, two weeks after the semester was done. We headed out to the Black Diamond Mines Regional Preserve, a unit of the East Bay Regional Park District to have a tour. Not a tour of the former towns...we were going underground!
We gathered outside the portal of the Hazel Atlas mine where we met Pat, the mining technician and engineer for the park. He came to work here in 1998 to prepare for the reopening the mines for tours after safety concerns shut them down in 1989 after the Loma Prieta earthquake.
We donned our hardhats, grabbed flashlights, and headed into the main portal. One thinks of mines as dark dank places, and I'll bet they were to the original coal miners, but with lighting and white colored walls of sand, the tunnel was actually fairly bright, at first not really different than walking down a corridor in a factory.
The main adit intersected one of the thinner coal seams in the Domengine Formation. The miners in the 1800s generally followed the seams until they thinned out to a foot or so. The thickest of the coal seams, the Black Diamond vein, averaged 40 inches thick
One can see in the picture above that the layers in the mine slope about 30 degrees. The miners accessed the coal seams from the lower end and excavated their way upward, allowing gravity to do some of the work for them.

Diagram from interpretive signs in the visitor center
The walls of the mine reveal other signs of the depositional environment of the sandstone. In the picture below are some crossbeds, formed in coastal dune complexes.
Farther in, the sand layers broke away to reveal symmetrical ripplemarks, which indicate oscillating waves in shallow water. Although I didn't get good shots, there were trackways of worms in some sand layers, and burrows from crabs or shrimp. Such disturbances of sediment by biologic activity is called bioturbation.
By this point we had gone several hundred feet into the mountainside, and the tunnel turned 90 degrees to run parallel to the surface.
We had reached the main part of the mine, where excavation was done by the room and pillar method, where large chunks of sandstone were left in place to support the ceiling of the mine, in many places 6o feet above our heads. It's not often that I am in underground chambers this big. I almost expected a Balrog to come around a corner ("You shall not pass", he said, wielding his rock hammer like a wizard...)
There were dark unlit pits too. The dark squares on the left in the picture below are rock bolts, drilled into the rock to hold unstable jointed rock in place. Pat reported that chunks of rock do occasionally split off the walls and fall. One of his jobs is to locate such rocks along the main tour tunnel and either stabilize them or pull them down. That actually sounds like fun, even if a bit dangerous.
We had reached the end of the regularly scheduled tour, and found that there is an escape route out of the mines in the event of a collapse. We continued on, following the escapeway, because there was some good geology still to be seen!
We were now following a stope back towards the surface.
We intersected one of the coal seams, and could see why the coal mining was so dangerous. The rock was much softer and incompetent. They occasionally have problems with the coal because it generates noxious gases. When the sand mine intersected with one of the old coal mining passageways, there would occasionally be a spike in carbon dioxide or other gases, and the coal tunnel would have to be isolated to keep the air fresh.
I was surprised by how good the air was. The temperature was about 56 degrees and there was usually a current of air blowing through. It was not at all like some mining tunnels I've been in. I don't think there is any worse feeling than warm stagnant air in a dark tunnel.

Near the exit, we had a view down into the Eureka slope, one of the coal mines active in the 1860s. The picture below doesn't provide the downward perspective. It sloped about 30 degrees or more and disappeared in the darkness below. Visiting a coal mine? Fine. Working in one every day of one's working life? No, thank you. I like the job I have now.

We approached the surface after close to a half mile of walking underground. We had barely begun to explore the intricate boxwork of passageways in the mine. The visitor center occupies a particularly large tunnel at the other opening to the mine (the "emergency exit").
We emerged back into the world of sunlight and blue sky.

Although there are occasional tailings piles of coal here and there, the region has recovered nicely from the mining days, and is a nature preserve today with miles of trails and picnic areas. More information about the park can be found at It's well worth a visit!