Wednesday, June 29, 2022

Fan of Columnar Jointing? Here's a Real Gem for You in the Sierra Nevada, and it's Not Devil's Postpile


Tucked away in a small corner of an unheralded canyon of the Sierra Nevada is a real gem of a geological locality. It is a marvelous example of columnar jointing that has been modified by glacial scouring, and it's NOT called Devil's Postpile. Welcome to the Columns of the Giants.

The Stanislaus River doesn't quite have the panache of the Merced River, which flows through Yosemite Valley, or the Tuolumne River, the architect of Hetch Hetchy Valley. It's not protected as a national park like Kings Canyon. It had glaciers during the ice ages, but they didn't have the volumes of ice necessary to carve stunningly deep gorges like the previously mentioned river valleys. But it does have a grandeur all its own.


The headwaters of the Stanislaus expose rocks that are quite distinct from those of the other more famous rivers. The rocks have a darker aspect, due to being composed of relatively young volcanic rocks, rather than the granite that makes up three-quarters of the Sierra Nevada. Highway 108 crosses one of the uppermost tributaries at Sonora Pass (9,624 feet/2,933 meters), and travelers can get a spectacular view of these former volcanoes that were active about 10 million years ago. They erupted onto a muted landscape of eroded granitic rocks. Some of the eruptions produced flows that traveled more than fifty miles downstream through the canyons of the Ancestral Stanislaus River. Later erosion acting on these flows produced the famous Stanislaus Table Mountain in the vicinity of the Gold Rush Towns of Jamestown and Sonora.

Beginning around 2 million years ago, glaciers began tearing away at the higher parts of the Sierra Nevada, removing many of the volcanic flows and carving U-shaped gorges like the one above, visible just a few miles downstream of Sonora Pass at Chipmunk Flat. The ice age was not a single event. The ice advanced and retreated more than a dozen times, with warmer periods in between that lasted for thousands of years. It was during one of these interglacial periods that something extraordinary happened in the upper reaches of the Stanislaus River drainage. Roughly 150,000 years ago there was a volcanic eruption down in the canyon.

It wasn't a large eruption, certainly not on the scale of some of the rhyolite cataclysms that devastated the regions east of the Sierra crest 767,000 years ago. It was more of a mild cinder cone eruption that might have flooded a portion of the canyon, flowing just a few miles downstream before the lava flows ceased. Subsequent glaciations scoured away much of the remaining lavas, and river erosion removed still more. Hidden in a cleft, a basalt dike just upstream of the columns may be all that remains of the volcano responsible for the eruption. It's not much, just the fracture in the granite that filled with basalt that fed the eruptions above. 


The remains of the lava flow, though? Spectacular! The lava flow (or flows; there were possibly two of them) was ponded by some obstruction downstream, most likely a glacial moraine, and a modest lava lake developed, several tens of meters deep. As the lava cooled, it shrank and the rock fractured in generally hexagonal columns roughly perpendicular to the surface against which the lava flowed. Since the lava flows were erupted onto a canyon bottom with slopes on either side, not all of the columns are vertical (this is also true of the better-known Devil's Postpile). 

Subsequent glaciations (primarily the Tahoe and Tioga stages for those who want to know) tore away at the lava flow, exposing the columns. Over the last 10,000 years or so since the last Tioga glaciers melted away, frost wedging has pried many of the columns loose, dumping them into a vast talus slope that covers the base of the lava flow. Cold air emanating from the base of the talus suggests that a mass of ice might actually remain deep within the rockpile. 

Columns of the Giants can be easily visited by following Highway 108 about 25 miles east of the Pinecrest Lake Resort area or 13 miles west of Sonora Pass. Overnight accommodations can be found at nearby Kennedy Meadows and a number of National Forest campgrounds. Educational groups may be able to make arrangements to stay the High Sierra Institute at Baker Station just a few miles away (contact the Yosemite Community College District for more information).

Stanislaus National Forest has provided a parking area and simple toilets for visitors, and a paved ADA-compliant trail and bridge provides access. The trail is only a few hundred yards long, and the visual rewards are great. 

Can't get there in person? My friend and colleague Ryan Hollister put together a marvelous virtual field exercise that provides an experience that is the next best thing to being there. It was featured on NPR's Science Friday a few years ago.

Monday, May 16, 2022

How it Was: Lunar Eclipse of May 2022

This evening's lunar eclipse was visible all across North America, and it was spectacular! I hope you were able to see it, but if you didn't, here is some sense of what it was like.

Out here in California the eclipse was already underway at sunset, and most of the Moon was already in the Earth's shadow. It was kind of strange to see a "crescent" Moon rising in the east as the sun set in the west.

The sliver of the sunlit lunar surface grew smaller and smaller, and the Moon seemed to disappear in the deepening dusk. The darkened face of the Moon was actually glowing with red light refracted through the Earth's atmosphere, but it took a few moments for the sky to grow dark enough to see it.
The red of the Blood Moon became visible, and then I had a bit of a surprise. It is hard to see stars in the immediate vicinity of the full moon because it is so bright. But if you look in the picture below, look at the 10:30 position of the disk, and there is a star emerging from behind the Moon! I've never seen this happen before.
A few moments more, and the moon had moved away from the star, and several others were visible as welll.
It wasn't easy holding the camera still enough to catch the stars as well. I guess I should just use a tripod, but what's life without challenges? I only deleted 30 or 40 shaky shots...
This was an unusually long period of totality for a lunar eclipse. After around an hour, the bottom edge of the Moon began to glow brighter as the orb moved closer to the edge of the Earth's shadow.
And then just like that the Sun began to shine on the lunar surface again. 
The red disk disappeared and the stars dimmed and disappeared once again.
And then it was over, and our bright full Moon had returned. And that is how it was! Thanks to our friends Jeanne and Barry for a nice evening with a porch overlooking the Tuolumne River and a perfect moonrise!



 

Monday, May 2, 2022

Are You Sure That Enclosure Will Be Enough? New Dinosaur at MJC's Great Valley Museum!

I couldn't help but recall a certain famous movie opening: guys in hardhats unloading a dinosaur at a new park named after a geological time period...Cretaceous Park or something like that. Things went scarily wrong, and movie history was made.
Today's experience didn't end badly though, since the dinosaur in question was a plant-eating Parasaurolophus and it wasn't a living specimen. It was one of the final additions to the Great Valley Outdoor Nature Lab at the Great Valley Museum on the campus of Modesto Junior College.

The exhibit commemorates a little-known fact about our county: it was the site of the first reported discovery of dinosaurs in California. Back in 1936 17-year-old Al Bennison was exploring Del Puerto Canyon in the Coast Ranges along the western part of Stanislaus County looking for shell fossils when he found bones scattered on a slope. He showed them to his science teacher who reported them to the paleontologists at U.C. Berkeley. It proved to be the partial remains of a Saurolophus, which was one of the last dinosaurs that ever lived on our planet, one the last groups in existence when the gigantic asteroid hit the planet (or when the volcanoes blew, or whatever else did them in). They lived in the latest part of the Cretaceous Period, which is well represented by sedimentary rocks in our region. The rocks are marine in origin, which tend not to be good places to search for dinosaurs, but sometimes a carcass would float out to sea, as this one did.

The creatures were gigantic, on the order of thirty to forty feet long, weighing several tons (our model is a 1/2-sized replica at 16 feet long). They were plant-eaters, with teeth well-adapted to grinding twigs and leaves. Whether they swam or not has been a topic of discussion and debate. Some argue that they had few other defenses from predators, so that swimming was necessary to escape from being eaten. Others suggest that they lived in herds that provided protection. California designated a species of Saurolophus, Augustynolophus morrisi, as the state dinosaur in 2017.
For comparison purposes, here is what the Saurolophus looked like. Source: http://en.wikipedia.org/wiki/Saurolophus
We thought it was important to put a dinosaur on display as we planned for the new Great Valley Outdoor Nature Lab. Dinosaurs certainly capture the imagination of our children (and not a few of our adults), and it is a good thing for our students to know that our county played an important part in the paleontological discoveries in our state. When students realize that one of their own (however long ago) made an important find, they also can visualize themselves as a paleontologist or geologist making important contributions to science. The concrete squares covered by orange tarps are mock paleontological digs where students can experience the sense of discovery that all paleontologists live for.
So why a Parasaurolophus, and not the Augustynolophus morrisi or other 'real' Saurolophus? That's easy: none of the marketers of dinosaur replicas offer any for sale, at least far as I could find. We figured that a similar species was better than none at all...
Trying hard not to be trampled to death 
What a great day for geological education in our county. I just hope the containment structure works! It just won't do to have wild dinosaurs running around on our campus...
 

Wednesday, April 6, 2022

Red Hills Area of Critical Environmental Concern (Couldn't the Bureaucrats Just Call it a Preserve?): Spring Update

Welcome to one of the most unique ecosystems and habitats in California's wealth of incredible places. It was ignored initially by miners in the region because it had no gold (the Mother Lode is a scant two miles away).  It was more recently ignored because it had no grass for grazing and poor soils incapable of growing anything "useful". The Bureau of Land Management, tasked in its early days of giving away land by way of the Homestead Act couldn't give the free acreage away at all. All but ignored by federal government, the absentee owner, it became an unofficial garbage dump, unauthorized shooting range, and unsanctioned off-road vehicle route. 
Why were the soils so poor in nutrients and toxic to plant growth? It was the underlying rocks: the serpentine and other ultramafic rocks associated with the Melones Fault in the Sierra Nevada Mother Lode. The soils developed on these rocks were severely deficient in important macronutrients, and contaminated (so-to-speak) by toxic metals. Most plants, including most grasses, cannot survive in these soils. Some select species tolerate the soils, and a few rare ones thrive. It is literally a different world, and as you can see in the picture above, the change is abrupt, as the prairie grasses and oak woodland suddenly give way to ceanothus or buckbrush and gray pine.
By the late 1980s the Bureau of Land Management, the federal agency in charge of the Red Hills area, belatedly recognized (with the encouragement and assistance of community and environmental activists) the unique nature of the ecosystem here, and declared it an "Area of Critical Environmental Concern", the kind of a designation that only a bureaucrat could love. It turned out that this landscape contained a large variety of endemic species found almost nowhere else, including a unique fish species, the Red Hills Roach (Lavinia symmetricus). Clean-ups were organized, and minimal tourists facilities (trails, parking areas, vault toilets, and a nature trail) were constructed. 
Bitter root (Lewisia rediviva)
For much of the year, especially in the hot dry summer, there is little to recommend about the Red Hills. Most of the plants are dead and gone to seed. But for a few months during the cooler wetter spring season, the hills come alive. It turned out that many of the plants adapted to living in these soils produce a vivid display of color when they bloom.
California Goldfields (Lasthenia californica) and scattered poppies
We took a bit longer to make our way up to the Red Hills this year, in large part because there hasn't been more than a spatter of rain since December. We are in the midst of another year of lingering drought. But in the end we decided to have a look, and although it came nowhere near the pyrotechnics of color of past years, there was more than enough to make for a satisfying excursion.
Poppy, a flower that seems able to grow in just about any environment California can fling at it.
Enjoy a little bit of color!
Monkeyflower (Erythranthe sp.)

Blue Dicks (Brodiaea)

The parking area and trailhead at Red Hills ACEC

Poppy sp. and Blue Dick (Brodiaea)

Serpentine
The Red Hills got their name from the red soils that develop on the ultramafic rocks, including serpentine. The rocks are rich in iron, thus the red color, but fresh surfaces of the rocks are generally shades of green, as can be seen above.
Paintbrush sp.

Lupine sp.

Lupine sp.
The Red Hills Area of Critical Environmental Concern is in the Sierra Nevada foothills near Chinese Camp off of Highway 120. If you want to learn more, or pay a visit, information about the Red Hills can be found on this BLM website, and the trail and road map can be found here.
 

Thursday, March 31, 2022

Those Things We Scientists Never Talk About...

I am often asked if I have run across strange phenomena in my travels. My journeys take me to many different places and environments, and frankly, some really...um...eerie things have been known to happen. It is not one of those things that we earth scientists like to talk about, and one might be tempted to say, really that we could say, we have been hiding this knowledge from the public for years. I don't think that conspiracy is the right word here, it's just that we don't think that the public at large should be led to believe in the existence of these things.  That there are things out there...
They're seen in caves in and around Mt. Shasta and Medicine Lake Highland. If you are in the dark long enough...you start to see the lights. They float through the open spaces of the lava tubes, the long passageways produced when subsurface lava flows drain away from openings downslope. They aren't easy to photograph, but I once hid behind a pile of broken rubble and left the shutter open. The spectral lights appeared around the corner and silently passed by.
There are stories about the Atlanteans and Lemurians inhabiting the underworld of Mt. Shasta, and incredibly detailed descriptions of how they carved the tunnels of their underground cities. Being the hard-boiled logical scientist I am, I am not unreluctant to declare that this is the only possible explanation for these lights. The underground civilizations of beings who lost their islands in the Mediterranean Sea and Indian Ocean tens of thousands of years ago in giant cataclysms and who came to Mt. Shasta and Medicine Lake Highland to some might make so much more sense than anything else that could explain the images on my digital camera.

In Avril Erste, there is a colleague who can back me up on all my assertions. Avril has seen these same lights in other caves, too, much farther south than Mt. Shasta. They're in the caves of the Sierra foothills too...
I want to believe...

Friday, March 25, 2022

A Tale of Two Pullouts: Yosemite Valley From a Different Angle

El Capitan and the Merced River from the east

I know that I am truly privileged living as I do only a two-hour drive from one of the most sublime places on Earth, Yosemite Valley and the Sierra Nevada. We head up there two or three times a year, sometimes with students in tow, and sometimes on our own, so in 30+ years we've been there at least 100 times.

And I never get tired of it.

Part of the allure is seeing the seasonal changes. Winter provides the coating of snow, while fall provides the changing colors of foliage. Spring offers surging waterfalls and wild river flows. Summer provides...well...crowds, but also nice moments in places we learn of where the crowds can be avoided. We have favorite meadows and lakes for instance where people rarely stop. No matter when or where we visit, there always seems to be something new or different.

The Cathedral Spires are tucked away on the east side of the Cathedral Rocks at Bridalveil Falls
I know how it is if one gets to see Yosemite Valley for the first, and maybe only time. I've had that experience at so many other places around the world. The time available may be very limited, one may be part of a tightly controlled tour, and no one wants to miss any of the most famous views or hikes. And so it is that there is the required stop at Tunnel View, Bridalveil Falls, Cook's Meadow for the view of Yosemite Falls, and maybe Ahwahnee Meadow for a view of Half Dome. The walk to Lower Yosemite Falls, or Nevada Falls. And the Visitor Center. It makes for a full day, and a fulfilling day too. One of the most spectacular days you might ever experience.

And I never get tired of it. I'm perfectly happy to hit those same spots on my 101st trip to the valley. The season, the time of day, and the weather all conspire to make each stop a unique experience of wonder. But sometimes there are changes of a different nature, and that makes some trips really memorable. That is what today's collection of views is about.
Sentinel Rock rises above the south side of Yosemite Valley across from Yosemite Falls
Since the time that Yosemite Valley became a park, suppression of all forest fires has been the official policy. It was not however the natural condition of the parkland, nor was it the normal condition of the valley floor over the last few thousand years when it was managed by the original inhabitants of the region. 

The Ahwahnechee people, with roots among the Miwok and Paiute peoples of both sides of the Sierra, depended in large part on the acorns of the Black Oak and grazing animals like deer or bighorn in Yosemite Valley. It was in their best interest over the centuries to allow fires to burn through the valley floor and hold the quick-growing conifers at bay. When the park administrators put an end to the fires, the pine and cedar trees choked out meadows (only 65 acres of the original 750 acres of meadows remain) and grew into impenetrable thickets, blocking views of the canyon walls above.

What's worse is that choking off small fires can cause a buildup of fuel in the forest that could only lead to much worse fires than usual. This was always a danger, but it is far more hazardous today in a time of warming climate and extended droughts. Every Californian is fully aware of how wildfires in the state have morphed into monstrous events without parallel in written history.

The National Park Service has come around in their fire philosophy, especially after extensive fires a few decades ago in Yellowstone and Mesa Verde National Parks. They have instituted new policies of prescribed fires and selective tree removal to make the parks safer, but also to enhance the experiences of park visitors. In what way? The views.
The distinctive profile of the Three Brothers is the result of parallel jointing, or fractures in the granite that occur as the rocks are exposed by erosion
There are the parking lots that attract the majority of park visitors, but on the roads that loop around the valley there are many small pullouts, enough for perhaps three or four cars. In years past there seemed no real purpose for them, as they were surrounded by thick forest and offered no views or trailheads. On our visit a week ago, I found that two of those previously uninteresting pullouts had had the forest thinned out, and that they now possessed some outrageously spectacular views! The familiar iconic cliffs were there, but from angles I had never really seen before. In particular there was the long vertical cliff extending east from El Capitan, a view of the rarely seen Cathedral Spires (as opposed to the Cathedral Rocks at Bridalveil Falls), the vertical pillar of Sentinel Rock (often missed by people staring at Yosemite Falls), and the Three Brothers, which have never really had a designated viewpoint and are usually hidden by the tall trees. Upper Yosemite Fall was visible as well, perhaps farther away, but how many of you Yosemite veterans can recall seeing the falls with not a single other person in sight?
Yosemite Falls from a pullout west of Swinging Bridge
We had a leisurely lunch at the pullouts and wandered about taking pictures, and only two or three cars pulled off the road, and no one else actually got out. Except for the noise of passing traffic on a crowded Sunday afternoon, we literally had the best of Yosemite Valley to ourselves.
Prescribed fire in Yosemite Valley, with Half Dome and Clouds Rest in the distance.
We stayed at the park through Monday morning, and when we stopped by Tunnel View we witnessed another chapter in the new fire/forest regime: the ignition of a prescribed fire. It was done in March because the ground was still damp enough to prevent the uncontrolled spread of the fire. If you are on Facebook and would like to know more about forest management in Yosemite, check out (1) Yosemite Fire and Aviation | Facebook.