A Series of Nearly Unfortunate Events: Fall in Yosemite National Park

Oh jeez, that's not something one likes to see on a field trip...

How many horror movies begin with people ignoring the warning signs, both literally and metaphorically? The doomed characters doggedly soldier on, minor disasters mount, and then major disasters. Today felt a little like that. At our second stop, two CHP units took up positions on both sides of the bus. Uh-oh...

It turned out they were there for the cow which had escaped the nearby pasture. We helped herd the wayward bovine back inside the enclosure.

We passed the continuing effort to contain the huge Ferguson Slide, which collapsed into the Merced River and across Highway 140 nearly ten years ago. It's been completely covered with boulder containment nets, and they are apparently ready to start work on the rock shed that will allow future rocks to roll over the road and into the river.

And then the first of the menacing signs. The rain had started falling, a true blessing in the drought, but why during our field trip? Because it was maybe a metaphorical sign, of course! Don't go on!

But the next sign said not to stop! What were we to do? 

There were fires burning next to the road, and after all the horrific wildfires of last summer, one could hardly resist the urge to call and report the fire. But the signs said not to report! What were they trying to hide?

Sorry for the blur. We couldn't stop!

The actual reason for the fire of course was to try to bring the valley floor back into some kind of reasonable ecological balance. Fires had been suppressed on the valley floor starting when the park was established, but this turned out to be a bad idea. So many trees grew that the forest was too thick and full of fuel that a wildfire could have destroyed all the trees, not just some of them. By burning the forest when conditions are safe, the troublesome trees can be controlled without destroying the mature trees.

So we pressed onward, farther into the valley through rocks, wind, rain and fire, just daring the elements to interrupt our geological field studies. And then we found incredible things! The storm relented for a few moments at at time and the cliffs and towers of Yosemite began to peek out from behind the clouds.

The fall colors were starting to appear here and there...

The clouds provided an interesting contrast to the forests and cliffs...

And at Yosemite Falls, we saw something precious and rare: flowing water. Two days of rain had rejuvenated the iconic waterfall, which had been dry since early summer. All in all, a challenging day, but also a spectacular day. And no crazed axe murderers!

A Series of Fortunate Events: Fall in Yosemite National Park

 It was a privilege this last weekend to conduct a field studies exploration of Yosemite National Park and the surrounding region. It was a new class, but was similar to one we last taught back in 2008 when the Great Recession put a serious crimp in the scheduling of our field studies courses (we still did them, but there were fewer of them). Even better, I have another day trip scheduled on Saturday for a different course. Yosemite twice in a week!

I say it in a joking manner, telling students they have to "earn" the right to explore Yosemite. It's true though, in a way. There is a lot of geologic history in the rocks west of Yosemite National Park, and they help us to understand the origin of the rocks in the park. An example is the outcrop along Highway 140 between Merced and Mariposa. Just east of Dial's Rock Shop is an exposure of the Mariposa Slate.

The Mariposa Slate is a deposit that formed on the bottom of a deep sea off the coast of California in Jurassic time. The shoreline lay east of where it is today, and the Sierra Nevada was a different place: a series of active volcanoes led to a coastal forest. Dinosaurs, pterosaurs, and primitive mammals roamed the forests and floodplains. In the sea, large swimming reptiles including plesiosaurs and ichthyosaurs were found. The Mariposa is somewhat less altered than many other rocks of the metamorphic belt, and because of this, a few fossils have been found which enabled geologist to figure out the age of the rocks. This was an important step in unraveling the complex geologic history of the region.

The Mariposa is part of a large section of crust called the Foothills Terrane, a group of rocks that were added to the western part of North America during Triassic and Jurassic time along a subduction zone plate boundary. A great deal of compression caused the rocks to be tightly folded, as can be seen in the photo above (note a set of car keys just below the center of the shot). The slate has excellent rock cleavage (the tendency to split into very flat surfaces) so it finds use as chalkboards and billiard tables. There is a quarry on the top  of the hill above the outcrop (you can just make out some heavy machinery in the second picture above, on the left side).

The Mesozoic subduction zone that placed the Mariposa Slate against the edge of the continent was also instrumental in the placement of the vast granitic plutons that are exposed today in Yosemite National Park. The slate provides some insight into what came before the intrusive igneous rocks.

Our path was not the straightest route. Instead of following Highway 140 directly into Yosemite, we turned south at Mariposa and followed Highway 49 to the town of Oakhurst. We were having a look at the largest living things in existence, as well one of the greatest mineral collections in the state. More next time!

National Fossil Day is Tomorrow! Do You Know the Paleontological Heritage of Your Region?

A hadrosaur skull similar to Saurolophus, the first dinosaur ever found in California

Tomorrow is National Fossil Day, which if anything, is of far greater interest than a holiday concerning an Italian explorer discovering a Caribbean island a few hundred years ago. One of the really exciting changes in our region is that our fossil heritage is being celebrated, pretty much for the first time. We finally have a museum with the room to adequately showcase the incredible paleontological history of the Great Valley of California. If you've read my blog at all, you'll know it's the Great Valley Museum at Modesto Junior College.

Two fossils here, but one of them isn't quite dead yet. The other is a Mosasaur

The Great Valley of California has a rich history of fossil discovery. Sediments were accumulating here in Jurassic and Cretaceous time, so dinosaurs and other reptiles have been discovered here, although not in concentrations like those of the continental interior. The first dinosaur ever discovered in California was found in our county. It was a Saurolophus, a variety of duck-billed dinosaur (the hadrosaurs). It was found by a teenager exploring Del Puerto Canyon in the 1930s.

Even more interesting, especially in light of a certain dinosaur movie last summer, are the Mosasaurs, large marine reptiles that were the terrors of the Cretaceous seas. One of them, Plotosaurus bennisoni, was discovered by the same kid who found the Saurolophus. It may have been 35 feet or longer in length.

Some fossils are more mundane, but they're exciting because I found them. Those would include these Jurassic wood fragments from the Sierra Nevada foothills. They were carried into the ocean by turbidity currents in the vicinity of the subduction zone that was once active here.

The most diverse and plentiful fossils are those of the creatures that grazed and hunted up and down our valley in Pleistocene time. The Fossil Discovery Center in the Madera area a few miles south of us has the best collection on display of these animals. The animals include the sometimes terrifying Short-faced Bear, Saber-tooth Cat, American Lion, and Dire Wolf. The grazers included a number of species of horse, camel and antelope, as well as mammoths and giant ground sloths. Many other smaller animals have been found in the quarry at Madera (which doubles as the sanitary waste disposal pit).

Few people in our county and region have had a venue in which they could learn about this fascinating fossil history, which is why the newly opened Great Valley Museum is such a wonderful opportunity. We have a full-sized skeleton of a Saber-tooth Cat, and a life-sized Mosasaur skull.

The newest exhibit highlights the research being done in Miocene sediments of the Mehrten Formation near Turlock Lake by the faculty and students of California State University, Stanislaus. Former MJC student Jake Biewer designed the current exhibit. The students are investigating some of the fossil sites where six-foot long "saber-toothed" salmon remains were found, along with tortoises the size of those found on the Galapagos Islands. Other exhibits are currently in the planning stages.

It's hard to describe how exciting it is to finally have a place to tell the story of the fascinating animals that lived here before us. The response from the children of our valley has been infectious. They love finding out that their home was once the home of that terrifying creature from the dinosaur movie, but also that they themselves could be the one who makes the next great discovery.

Have a great fossil day tomorrow! Learn something new about the place that you live!

And Mercury Makes Four. Beautiful Gathering in the Morning Sky

There is still a beautiful show in the sky in the early morning this month. When I realized I missed Mercury in my Friday morning picture, I went out again this morning for another try, and caught it between the trees on the eastern horizon. It's only the fourth or fifth time that I've seen Mercury (mostly out of laziness because you have to know just where to look), and only the second time I've photographed it.

In all the excitement about Pluto and Ceres over the last few months, it might be good to remember that NASA and the European Space Agency have been on a real winning streak of late. There are the tireless surface vehicles on Mars, the Cassini exploration of Saturn, the Galileo mission to Jupiter, and the Messenger mission to Mercury that have given us an unprecedented look at our Solar System. It is simply stunning that we have in just 58 years of space travel that we have had such success in exploring our nearest neighbors in space, and that they have turned out to be places of the imagination. No one could have predicted in 1957 that the moons and planets of our Solar System could have been so strange and wonderful.

Extraordinary Grouping of Planets this week

It was one of those incredibly busy weeks, planning for our campus club events, a "Wild Planet Day" fundraiser for our Great Valley Museum, a field trip to Yosemite, and all the regular stresses of an academic week. I didn't spend much time cruising the web, and missed the posts about the relatively rare close grouping of the visible planets this week in the early morning sky. But I sure couldn't miss it on Friday morning when I was loading the car for our early morning departure on a field trip. Out came the camera, and I got three planets and the moon together in one frame. The star Regulus is visible at the top, next to bright Venus. Mars is to the left and just above the Moon, while Jupiter is at the lower left. I found out later that Mercury had just risen over the horizon, but I didn't have a view of that part of the sky.

The ancients thought that such groupings were portents of great or terrifying things, but today we understand that we are seeing the result of orbital mechanics and gravitational attraction. But that knowledge doesn't take away from the beauty. If anything, our understanding of why the planets appear this way makes it all the more beautiful.

Faulting, Volcanism, and Life in Northernmost California: the Tulelake Graben

Gillem's Bluff at Lava Beds National Monument

Lava Beds National Monument at the extreme north end of California is a fascinating place. It preserves hundreds of lava tubes and lava flows only a few thousand years old. It also preserves the memory of a people, the Modoc tribe, who were destroyed so settlers could raise alfalfa and potatoes. And there are lakes that formerly gave life to millions upon millions of birds. The smaller lake that persists (with human help) provides shelter for the migratory birds who remain. The lake basin below Lava Beds is protected as the Tulelake National Wildlife Refuge.

Multiple fault scarps (the shadowed terraces) cross the region north of Lava Beds National Monument

It began with faulting. The crust in this region has been stretched beyond the breaking point, and some of the fault blocks have sunk against the others, forming a series of horsts (the uplifted blocks), and one deep graben (the sunken block). The main fault scarp in the top picture is called Gillem's Bluff. One can just make out the waters of Tulelake at its base.

The faults provided an avenue for basaltic magma to reach the surface. The rough blocky a'a lava in these photographs is the Devil's Homestead flow, which emerged just over 10,000 years ago from fissures at the Fleener Chimneys in Lava Beds National Monument.

The graben became a collecting sump for waters in the Klamath River drainage. The present incarnation of Tulelake covers only about 15 square miles (five miles long and three miles wide), but the lake once extended across one hundred square miles. Diversions of the rivers that fed the lake caused vast portions of the lake to dry up and the new land was converted to agricultural fields. Not that the original European settlers particularly cared, but the lake was a critical stop where migratory birds rested and fed during their long journey between the Arctic regions and their winter homes in central and southern California. The topography literally funneled the birds through to Tulelake and  the Klamath Lakes a bit farther north. The lands here are mostly arid, and the water was a sanctuary.

The birds still come, Sandhill Cranes, Ross's and Snow Geese, Greater White-fronted Geese and many others, more than a million each year, but they face challenging conditions of overcrowding and disease, especially in dry years when there is less water and food (the lake is at the end of the receiving line in terms of water allotments). Avian cholera sometimes kills thousands of them. But they've survived, and I hope they will continue to do so.

Earthly violence in the form of earthquakes and volcanic eruptions created this strange landscape, but water made it productive and full of life. It's a fascinating place to visit, especially in spring and fall when the bird migrations peak.

Time Heals All Wounds. Or Does it Just Hide Them? The Ghosts of Nelder Grove

It's a beautiful place, really. It was one of the most serene places I've been in my travels, away from busy roads, cities, tourist traps, and most of all, crowds. We were only 10 miles from Yosemite National Park on a Sunday afternoon, yet we shared the place today with just six other people, all of whom were quietly looking up as if in a a medieval cathedral.

Sequoia groves are like that. The ancient trees are so big and so tall, so grand, that they seem to inhabit a different universe than "normal" trees. They tower above, like placid gods looking down on their earthly domain. They are the only species in their genus,  Sequoiadendron giganteum. The species, or species very much like it, once grew across the northern hemisphere. Through habitat loss, perhaps related to the ice ages, they disappeared from most of their range. Only on the western slopes of the Sierra Nevada have they survived, living in 68 isolated groves, and numbering only in the few tens of thousands (the more widespread Coast Redwoods of northwest California are related, but are classed in a different genus).

We were walking through a mountain cathedral, marveling at the beauty and size of the incredible trees, but I realized there were ghosts all around us. There were only 16 mature Sequoia trees along the trail we were following, but there were dozens of gigantic stumps. This serene forest was a shadow of its former glory. Someone had cut down these forest giants. According to the Friends of Nelder Grove, the entire grove includes just over 100 mature trees spread over 1,540 acres (2.4 square miles). There are 277 stumps hidden in the shadows. Three quarters of the trees that had survived for 2,000 years or more were cut down in a few decades, between the 1890s and 1920s.

The sad part is that the wood, though resistant to rot, is brittle and was rarely used for anything more substantial than grape stakes and shakes, even toothpicks. As much as 75% of the wood went to waste, as most of the trees shattered when they hit the ground. Loggers would build trenches filled with tree branches for the trees to have a soft landing, but to no avail.

The remaining trees have been protected since the 1920s, but they still face some serious threats. The trees are adapted to fire. Their trunks are very thick and do not readily burn, so the wildfires that would burn through the grove every decade or so would kill off saplings of other trees and clear the forest duff, but would rarely kill the Sequoia trees. The nature of the fires has been changing. The policy of the Forest Service for decades was to suppress fires at all cost, allowing the other conifers like White Fir and Sugar Pine to grow very tall, reaching the lowest branches of the giant Sequoia trees.

Sugar Pines are especially susceptible to catching fire, and the fire rises up the trunk into the crown. Crown fires can kill the Sequoia trees by destroying their foliage. So by protecting the trees from fire, we've made it easier for fire to destroy them. The situation has not been helped by the growing effects of global warming. Ongoing drought has led to super wildfires on a scale never before seen in the Sierra Nevada. Several recent fires burned through 200,000 acres or more.

The deep conifer forests threaten the Sequoia trees in a different way. The seedlings need bare soil and sunny conditions to germinate, but the thick forest instead provides shade and thick forest duff. The remaining ancient giants are not being replaced by young trees, not at a rate fast enough to guarantee the future of the grove.

At least we've reached a point where we know what many of the problems are, and steps (sometimes baby steps) are being made to preserve the future of these incredible trees. In the meantime, the Nelder Grove is a quiet treasure, a beautiful place for meditation.

The Nelder Grove is off of Sky Ranch Road, about 8 miles off of Highway 140 north of Oakhurst, just a few miles from the south entrance of Yosemite National Park. The last two miles of road are unpaved, but the gravel is well-graded. Our walk was along the Shadows of the Giants trail, but there is a network of trails throughout the grove. The Mariposa Grove in Yosemite is presently closed to visitation as the site is being renovated to improve the visitation experience and protect the trees. Of course when it is finished, the grove will still be visited by hundreds of thousands of people yearly. If you want to see a Sequoia grove the way it should be, quiet and uncrowded, check out Nelder. For more information, check out the web pages of the Friends of Nelder Grove, or this Sierra Nevada Geotourism site.