The Great Drying Has Begun: Springtime in the Sierra Nevada

It may seem paradoxical to speak of drought in California right now. The snowpack in the Sierra Nevada is running nearly 200% of normal, and farms are receiving the most irrigation water they've seen in years. Yosemite waterfalls are thundering. Yet that is what is happening this week, just as it does every year. The great drying has begun; the subtropical belt of high pressure, which maintains the aridity of places like the Sahara and Australian Outback, is making its presence known here in California. Despite the overwhelming amount of precipitation this last winter, we'll see hardly a drop of rain anytime between now and next October.

Even though the high country is still encased in a mantle of snow, the grass is dying here on the floor of the Central Valley. The low foothills are turning brown, so we headed a little higher, where spring is still happening. Marshes Flat Road climbs out of the Don Pedro Reservoir area onto a resistant ridge of metamorphic rock called the Penon Blanco Volcanics. These rocks formed as volcanic islands in the Pacific Ocean in Jurassic time, and were pushed into the western edge of the North American continent in Cretaceous time and scraped off to become part of what is called the Foothills Terranes. The road reaches elevations of 1,800 feet or so before crossing the ridge into the Mother Lode region at Moccasin.

The rocks are mostly greenstones, and are shot through with occasional quartz veins, as can be seen in the picture above. Oh wait, is that a flower of some sort? We've discovered spring again! It's moving uphill right now, and will take all summer to reach the alpine peaks at 12,000-13,000 feet. That is certainly the fun of living in this state. Even as the valleys dry out and bake in the dusty heat of summer, the mountains still get a certain amount of orographic (rain shadow) precipitation and remain green through September.

As I've mentioned before, I have no qualms about making my students learn the names of a couple of dozen minerals, but I have never learned more than a few flower names during my travels. In my own perception, then, I might see flowers every year, but without learning their names, they seem like a new discovery. That's fun in a way, but it is also an appalling form of ignorance, so I'm undertaking a personal project to learn the names and nature of some of the flowers I am seeing this year. So, the hardy succulent in the picture above that survives in the cracks and fractures of solid rock where almost nothing else can grow is a Live-Forever(Dudleya cymosa, corrected with Neil's help). I've seen them before and wondered how they survived, but it seems clear that they store the moisture in their leaves, rather than drawing moisture from the ground.

I'm pretty sure I've never closely observed these striking scarlet colored flowers up close. I suspect that I mistook them for Indian Paintbrush in the past, but a close look this week made it clear that they are something entirely different. These showy flowers are called Indian Pink (Silene californica), or Catchfly, or Campion. None of my internet sites seem clear on why they are called Pinks when they clearly are not. It may refer to the pink at the center of the flower, or that they are part of a family of flowers that include pink varieties. The "Catchfly" name refers to sticky parts of the flower that sometimes traps insects.

In a meadow near the summit of Marshes Flat Road, we found a beautiful purple flower that seems to be a Larkspur (Delphinium species). Besides being very obvious, it is also highly poisonous to cattle.

Another flower that did not seem at all familiar was the White Fairy Lantern (Calochortus albus), which is a member of the lily family. The flowers never really completely open up (gotta make those bugs earn their nectar?).

I've seen Clover (Trifolium sp) many times in springtime meadows, but I've never really gotten down on the ground to have a closer look.

I've also noticed this beautiful small pink flower in the past (below), but never identified it. I was surprised to find it is called Wild Carnation (Petrorhagia dubia). The genus name translates to rock fissure, referring to where some of the species grow. It is actually native to Europe.

Of course, flowers aren't the only things we see. The oak trees were bright green, and quite a few Acorn Woodpeckers were flitting about. They didn't pose very nicely for me, but I got one shot that allowed me to identify this shy one.

As always, being the non-expert botanist, I am open to corrections for any misidentifications! More spring updates as I find excuses to hit the road!

Reflections on Yosemite and Mass Wasting

OK, not philosophical reflections, but literal reflections. One of my favorite spots to visit on the floor of Yosemite Valley is the Mirror Lake area, due to the relative peace and serenity brought about by the lack of cars and other urban distractions. Just people walking about quietly. Mirror Lake is not exactly a lake, and not exactly a river, and for a good part of the year it is entirely dry.

Tenaya Creek is a relatively minor tributary of the Merced River, but Tenaya Canyon is nearly as deep as the Grand Canyon. That would seem to be a bit of a mystery, since the size of glaciers in a canyon can be roughly comparable to the size of the watershed, and it looks like there was a very large glacier here. Studies of the glacial topography help to explain the disparity: large masses of glacier ice spilled over the divides from the Tuolumne River drainage, adding to the ice load in Tenaya Canyon. As big as they were, glaciers never overrode the summit of Half Dome, which looms thousands of feet above the lake. They instead undercut part of the base of the dome, taking advantage of joint patterns in the granitic rock to quarry rock away from the 700 foot-high face.Mirror Lake developed several thousand years ago when a large rockfall collapsed off the north wall of the canyon, damming up Tenaya Creek. The lake mostly filled with sand and was turning into a meadow, but heavy riverflows during spring runoff scoured out the river channel and left some very wide pools that are excellent for photographing (and just appreciating) the cliffs and domes that are reflected from above.

Lest one thinks that the rockfalls in Yosemite are a thing of the past, a large rockfall occurred here just a few years ago (see some posts on the Ahwiyah Point fall here and here). Ahwiyah Point is the prominent summit just east of Half Dome (below). The rockfall destroyed hundreds of trees, and a hiking trail, which is still closed to entry due to continuing danger from falling rocks.

Mirror Lake is not hard to get to (a tram stops just about a mile away), and one can even ride a bicycle most of the way up. There is a small network of trails around the pools, and the main trail climbs out of Yosemite at Snow Creek. It is a very beautiful corner of a very beautiful valley. Don't miss it if you get a chance to visit!

Random Thoughts on Yosemite in Spring

My last couple of posts on Yosemite in springtime followed a theme of some sort, rockfalls or waterfalls and such, but I also just plain saw a lot of beauty derived from the bounty of water at this time of year. The nice thing about a place like Yosemite (and any other kind of park) is the richness of color and texture in features big and small. The picture above is of some redbuds that are still blooming, along with a groundcover teeming with flowers of all kinds.

It was raining prior to our arrival...moisture was everywhere, including the droplets on the clover by the highway where we looked at Grouse Creek Falls. The clouds were moving eastward ahead of us, giving an interesting perspective to the little noticed cliffs around Stanford Point (little-noticed because everyone is looking east to El Capitan, Half Dome, and Bridalveil Fall from the Tunnel View parking lot. It's one of those cases where these cliffs would be world-famous if they were located anywhere else.

Half Dome was putting on a show today, too. This view from the Curry Village parking lot is hard to miss, although I almost always get a telephone wire in the picture. Whose idea was it to string a telephone wire across the view of one of the most iconic rocks in the American West?

Tenaya Creek was running full, and will deserve an entire post of its own in a day or two. The water is strikingly clear, primarily because the watershed above has been stripped almost entirely clean of soil by the glaciers that coursed through the canyon as recently as 13,000 years ago. The water flows over barren rock over much of its course and thus carries relatively little sediment.

One more waterfall to add to the mix. This is Royal Arch Cascade, which tumbles down the canyon wall just west of the Arch. Most people don't see this particular view, as it is a zoom view of just the very top of the waterfall.

It is easily viewed from the parking lot of the Ahwahnee Hotel. We had an appetizer in the bar for the price of a dinner! And it felt worth it...

As we left the valley, we made a brief stop at Valley View, another one of the iconic views of Yosemite just west of the "Gateway", the towering cliffs of El Capitan and Cathedral Rocks. Jet contrails usually screw up pictures of nature, but there seems to be a kind of symmetry to the ones seen here.

Spring in the Sierra Nevada: Some of Yosemite Valley's High Waterfalls

Yosemite Valley is justly famous for its beautiful waterfalls, and literally billions of pictures have been taken of them over the years (and that's just counting me). Bridalveil Fall (above) is one of the most visible and popular. During the spring runoff the falls run fast and cold and are the main reason most people are visiting Yosemite right now. It's too early for the flowers, and the high country is still wrapped in a deep, almost record-breaking blanket of snow. Although the eyes are drawn to the famous and familiar falls, springtime is a good time to see some of the less famous ephemeral falls that in any other place would be the center of attention. This last weekend, after chasing down rockfalls in the Midpines area, we made it to Yosemite Valley. This particular day I was able to discover a new thousand-foot high waterfall for the first time, and I caught another of my favorites from a new angle.

As noted a few posts ago, the highest single drop in Yosemite Valley is not Upper Yosemite Fall (1,430 feet), but is instead Ribbon Fall (1,612 feet) just west of El Capitan (above). It is usually viewed from the valley road near Bridalveil, but when I pulled out at Valley View at dusk, I saw it from a different perspective. There are a lot of trees that tend to block the view, but you can get a clear shot from...er...the middle of the busy highway. Needless to say, it is a stupid way to get a shot...

While I was standing...er...in the middle of the highway, I realized I had a fine view of a fall I had not noticed on previous trips...it is informally called Widow's Tears, and it drops over 1,000 feet down a series of ledges. There is some confusion about the name. As Mike Osborne reports in Granite, Water and Light, the name Widow's Tears once graced what is today Silver Strand Falls. The name was officially set aside in the 1920's, but in the 1970's ice climbers gave the name to this ephemeral cascade in the alcove just to the east. The northern shady exposure provides some excellent winter climbing opportunities.

If you ever sit down for a pizza in the plaza at Curry Village in springtime, be sure to look at the cliffs below Glacier Point for a view of one of Yosemite's really unique ephemeral waterfalls, Staircase Falls. The rocks have a prominent set of diagonal joints that force the water to fall over a series of ledges that cause the waterfall to go sideways around 1,000 feet while falling about 1,300 feet vertically.

Lest you think that I totally ignored the famous waterfalls, I most certainly did make a stop at the base of Yosemite Falls to catch the spray. The falls were booming away, but as I watched the beautiful spectacle, I realized it has been a rather cold spring. Most of the snow is still up there in the high country, and when the warm days come, these waterfalls are going to get even bigger. The temptation will be hard to resist, so expect a few more on-site reports in the next few weeks!

Rockslide on Highway 140 Near Yosemite (Video)

Headed up to Yosemite Valley today to see some waterfalls and enjoy the holiday. Had a wonderful time, but had an extra surprise. Got to see a modest rockslide on Highway 140 on our way there, and managed to catch it on video! We were driving down Highway 140 near Midpines on our way down to the Merced River when the new rockslide caught my attention. A lot of rock had already fallen, and given that there was a bulldozer parked on the other side, it was clear that the main event had happened a day or two earlier, but I decided I wanted a picture so we stopped and I hopped out.
As I approached the slide, I could see a couple of large boulders still perched near the top of the roadcut that looked unstable, and I could hear small pebbles bouncing down the slope. When I got closer, I realized the pebbles and cobbles were dropping out from under the larger boulders. The rock was slowly giving way and I had a suspicion (and yes, a secret hope) that it might be about to collapse. I moved the camera setting to video, and only a minute later I got lucky. I was standing across the highway, and luckily no cars were passing at the moment. A couple of the broken chunks landed on the highway

The picture above is the only shot I got before the slide. The rocks on the lower part of the roadcut are probably greenstones, metamorphic volcanic rock, while the unstable material above is metamorphic slate. Both are part of the late Paleozoic Calaveras Complex or Sullivan Terrane. The material was deeply weathered (thus the red coloration), which contributed to the slope instability. Further instability was introduced by having a roadcut in the first place, which oversteepened the slope, and by the tremendous amount of precipitation we've had this year, around 150% of normal. There were numerous other examples of recent slope failures along the entire Highway from Mariposa to the entrance of Yosemite National Park.


Sure, it wasn't the biggest slide in the world, but it was very loud, and it was very cool to be standing in front of it when it happened. You can hear me starting to say "I'm O.K." at the end of the recording, mainly because my wife was down the road a bit and heard the rocks drop, but couldn't see me.

Professor Incognito Reawakens...

I come crawling to the end of a long semester, and finals week looms, starting tomorrow. I've been wading through a massive pile of laboratory manuals and quizzes for the last four days. I'm having so much fun. It's time to revive the character who appeared on this blog last year about this time, a return at least as welcome as federal tax deadlines and lawn weeds. Professor Incognito is the creation of Zeo at ranthour.com, an artist who refuses to reveal the inspiration for her professor character. I certainly know it couldn't be me. I mean, I would NEVER say things like this...well...almost never.

Anyway, I must say that once again my students have exhibited a great deal of restraint in terms of begging for a passing grade. They mostly seem to know where they stand. But with finals coming up, I figure it can't hurt to clue them in as to what might happen if they try to con a grade they don't deserve. After all, they are ALL reading this blog, because I told them at the beginning of the semester that it would be fun and interesting to read. And who ever ignores advice from a professor? Especially my fine students, and in all seriousness, I have some stellar students this year. It actually has been a pleasure working with them, and they will be missed.

Oh, and for those thinking about a geology class in the fall? I welcome you! I welcome you all! Up to the limits being imposed on us all by the rationing of education by the state of California. If you make it into a class, by golly make it count! Don't be the other incognito character below...

Springtime on the California Prairielands: Violence in a Gentle Landscape (and a gratuitous picture of a duck)

The gentle wind caresses the waving blades of grass...meadowlarks sing, frogs chirp...it's a serene day in the springtime of the Sierra foothills. Of course the science of geology holds no such sense of peace. Almost every aspect of this peaceful view speaks of violence, both in the recent past, and in the depths of time.

Take the layers revealed in the gentle slopes of the first picture above: a few terraces of dark rock on the distant skyline and some white exposures near the creek. These are two of the distinctive strata that make up much of the Sierra foothill slopes near the Central Valley, the Mehrten Formation and the Valley Springs Formation. The Mehrten layers resulted from numerous volcanic mudflows (lahars) and floods caused by eruptions of andesitic volcanoes in the vicinity of the Sierra Nevada crest in Mio-Pliocene time. Events that form layers like these are no picnic. Volcanoes of the 20th century like Mt. St. Helens and Mt. Pinatubo of the Philippines produced destructive mudflows that caused damage dozens of miles away from the volcanoes.

Likewise, the Valley Springs Formation speaks of volcanic violence. In Miocene time, around 20 to 30 million years ago, huge rhyolite caldera eruptions rocked the American west. A single eruption was capable of producing hundreds of cubic miles of volcanic ash that buried thousands of square miles under a stiflingly hot layer of what amounted to microscopic glass shards. The layers of the Valley Springs Formation record a number of violent eruptions, some relatively close, such as at the Sierra Crest, but some of them originated from ash explosions in eastern Nevada. Today, the differentially eroded layers provide shelter for burrowing owls and swifts along the small creek above.

Roadside runoff provides a bit of extra moisture supporting a thicket of monkeyflowers along Willms Road near Knights Ferry (above). But again, the landscape reveals a bit of geologic mayhem with the black boulders of the Table Mountain lava flow in the distance.

A favorite stop of ours on our seasonal treks through the foothills along Willms Road is a small stock pond a few miles south of Knights Ferry. At this time of year the flowers and birds are plentiful. The cattail marsh on the far shore was filled with chattering birds of all kinds. A peaceful, if raucous scene, but once again the present-day scene reveals a history of violence. The bits of rock sticking out on the lakeshore and far hillside are exposures of the Jurassic (yes, that Jurassic, the dinosaur period) Gopher Ridge Volcanics. These are andesitic and rhyolitic rocks that formed volcanic islands along subduction zones in the Pacific Ocean many miles away. Not only was there the violence of the original eruption, there were also the tectonic movements that carried the island arc into the western edge of the North American continent. The rocks were jammed into the continent, deformed, and metamorphosed into greenstone and slate.

The timing doesn't have to be measured in the millions of years. A look at the grass stuck in the fence (above) reveals that the road was inundated three and four feet deep during one of our intense rainstorms a month or two ago. The flooding obviously didn't do the road a whole lotta good either.

The frogs in the creek seemed fine, but unfortunately they reveal a certain level of violence, this time to the ecosystem of the foothills. Bullfrogs are an introduced species. They are voracious predators of other frogs and the native species have not been able to compete. They have driven the native species into a few refugia where the bullfrogs can't survive (even there, the native frogs have problems; they are eaten by the introduced species of fish as well).
I would almost be depressed by all the violence, but geologic processes are the very essence of drama, and the earth would be a boring (and probably unliveable) place if we didn't have earthquakes, volcanoes, plate movements and mountain-building. Just the same, I am ending with a picture of a duck that I saw hanging out along the water. As far as I know, the duck is not a terrifying animal unless you happen to be a snail in the creek....