Under the Volcano and Into the Abyss: Yosemite National Park

Yosemite National Park is the oldest "national" park in the United States, having been established by Congress and Abraham Lincoln in the midst of the Civil War as a protected reserve deeded to California. It became an official national park in 1890, third after Yellowstone and Sequoia. I did a short blog series (boog? bleeries?) on some of the less familiar sights that one-time visitors might miss if they spend all their time looking at Yosemite Falls or Half Dome. I recalled the series while discussing America's relationship to the national park system in the aftermath of the wonderful Ken Burns documentary "The National Parks: America's Greatest Idea". I have them (semi) organized below in the order that they appeared. I've also included a flurry of posts on some of the rock falls in the last year. If you are ever headed out to Yosemite, check out the NAGT geologic road guide to Yosemite Valley and the western Sierra foothills (the extended wood-pulp version can be ordered here).

Photo of the Day - Feeling Crushed? : this series started far from Yosemite, but rocks in the Coast Ranges are very much part of the story. Sierra granites originate from subduction of crust and subsequent melting of these rocks to form magma. We take a drive into the crust that would make Ms. Frizzle jealous

Journey to the Center of the Earth (well, the mantle at least) A brief look at chrome and mercury mining in the Coast Ranges, in the subduction zone rocks

Continuing Journey in the Earth - Taking the Time Machine When granites were forming under the future Sierra Nevada, dinosaurs and sea-going reptiles prowled the ancient land surfaces

Standing Underneath Volcanoes We arrive at Yosemite Valley and I describe the familiar scene from the Tunnel View, and explain the odd title

Touring the Underside of the Volcanoes, Part 2 How easy is it to visit the underside of a volcano? We find out, and what enclaves are in this post

Under the Volcano: Changing the Emphasis Taking a closer look at the Cathedral Rocks and the El Capitan granite that forms the impressive cliffs

Under the Volcano: Changing the Emphasis -Part 2 Another less familiar cliff is Sentinel Rock (see the second picture above), and the Sentinel granodiorite of which it is composed

Under the Volcano: Changing the Emphasis -Part 3 One of the unknown waterfalls in Yosemite is the rarely seen Sentinel Falls, on the south side of the valley across from Yosemite Falls

Exploring Yosemite, continued and the Rock of the Day A brief foray west of the park on a beautiful spring day, and a look at some of the older metamorphic rocks

Under the Volcano: Changing the Emphasis -Part 4 Who's heard of Lehamite Falls? Many park visitors ignore them, for they are overshadowed by nearby Yosemite Falls

Yosemite Falls: The Spectacle that Almost Wasn't Yosemite Falls are actually an aberration! They were once far more like Lehamite Falls in the previous post...I explain why

Under the Volcano: Changing the Emphasis -Part 5 A look at the Lost Arrow

Under the Volcano: Changing the Emphasis -Part 6 The highest unbroken waterfall in Yosemite is not named Yosemite! I describe it in this post

Under the Volcano: Changing the Emphasis -Part 7 Another little-known fall, the Royal Arch Cascades, behind the Ahwahnee Lodge

Under the Volcano: Changing the Emphasis -Part 8 Silver Strand Falls, another unknown waterfall

Under the Volcano: Changing the Emphasis -Part 9 Sometimes the familiar sights become transformed by different timing. Yosemite Falls at night, one of the few times we ever had the valley to ourselves

Staring into the Abyss - Yosemite as you (maybe) have never seen it We leave the valley floor and take in the view from the edge of the abyss at Taft Point

Staring into the Abyss #2 - Yosemite as you (maybe) have never seen it The Three Brothers from the rim, and Yosemite's largest historically recorded rockfall

Staring into the Abyss #3 - Yosemite as you (maybe) have never seen it Looking west from Taft Point towards the Cathedral Rocks, and what happened to Yosemite's meadows?

Staring into the Abyss #4 - Yosemite as you (maybe) have never seen it (and my 100th Post!) There are many domes in the vicinity of Yosemite Valley, and most did not form because of glaciation. A discussion of North Dome and Basket Dome, from Glacier Point

Staring up out of the Abyss: Check out this fire in Yosemite I link to one of the most extraordinary pictures I've ever seen of Yosemite. A fire was burning on the north rim, dropping embers into the valley. Spectacular!

Staring into the Abyss #5 - Yosemite as you (maybe) have never seen it Nevada and Vernal Falls from the Glacier Point area

Taking the High Ground: Yosemite as you (maybe) haven't seen it Climbing Sentinel Dome. A bit shorter than Half Dome, and a lot easier to climb!

Revisiting Yosemite Several weeks passed, and I made a few last posts before embarking on my journey through the Colorado Plateau. Yosemite Falls on a very windy day

An Alternate View of Upper Yosemite Falls My photo of Upper Yosemite Falls from an odd angle.

Is This the Most Beautiful Tree in the World? Several months passed, and several posts continued the tour of the valley floor; my favorite oak tree started a mini-meme

More Beautiful Trees... The tree meme grows...

Even More Beautiful Trees, and a Sequoia Story ...and grows some more!

How It Was: Yosemite Valley Yesterday... I visit the valley on a rainy November day, and watch Yosemite Falls go from dry to booming in a few short hours

Rocks fall in Yosemite? I had no idea that could happen! A discussion of rock falls in the valley; there was a lot going on in the valley in 2008-09!

Rocks fall in Yosemite: Park Service closes 1/3 of Curry Village More rock falls

During a Drought, What Do You Think About? In the midst of one of the worst drought years in decades, I ruminate on the incredible 1997 floods in Yosemite Valley and downstream

An Extraordinary Picture (at least for us Central Valley denizens) We find that Half Dome is visible from the Central Valley (on those rare clear days, anyway)

How it was: Yosemite Valley on a Saturday in April A springtime trip to the valley in the aftermath of a major rockfall. Several posts followed...

First Look: Ahwiyah Rock Fall in Yosemite A first look at the Ahwiyah Rock Fall from near Half Dome. The view of Yosemite changes forever!

Another Look: The Ahwiyah Slide in Yosemite Got as close as I could to the new rock fall (don't people usually run the other way?)

A Final Look (for now): The Ahwiyah Point Slide in Yosemite The dust settles...

The Ahwiyah Point Rockfall: the View I Wish I Had The National Park Service checks in with some great photos of the rockfall

Ahwiyah Point Rock Fall Update: Before and After Photos Doug Nelson provides a great view of the rockfall from Glacier Point

Geologic Change in Yosemite: Remembering the Happy Isles Slide of 1996 A look at the big slide behind Happy Isles...

Another Rock Fall in Yosemite ...and the next day, another fall takes place!

Ollie Hopnoodle's Haven of Bliss and America's Greatest Idea And we arrive at the most recent post on my favorite park.

I intend to continue some photo-essays on Yosemite National Park. I'll update this post as they appear. If you take the time to check them out, I thank you and hope you enjoy the series!

First Look: Ahwiyah Rock Fall in Yosemite

For a first look at the latest rock fall in Yosemite National Park, I offer two nearly identical perspectives of Ahwiyah Point: I didn't predict the rock fall! I was able to crop a shot of Half Dome from a trip in 2004 that included Ahwiyah Point and almost match it from a shot taken today. The release point is on the left side, near the top of the cliff. The scar of the rock fall is visible from many, many points in the valley, including perhaps the most famous at the Wawona Tunnel. The appearance of Yosemite Valley is changed forever, even if in a relatively small way (small from a distance, anyway; it is greatly changed from up close)!

Details are starting to emerge about the event, including seismic information. The rock mass fell some 1,800 feet, and more or less exploded on impact, causing an airblast that spread pulverized granite dust throughout the area. The rocks and blast knocked down hundreds of trees, according to a preliminary note from the park geologist, Greg Stock (from the park's daily report at http://www.nps.gov/yose/parknews/upload/daily.PDF). Thankfully, no one was injured.

More pictures soon!

A Final Look (for now): The Ahwiyah Point Slide in Yosemite

When the Ahwiyah Point Rockfall impacted after a tumble of 1,800 feet, the slabs and boulders of granitic rock exploded, producing an airblast that is reported to have flattened hundreds of trees (and also producing a magnitude 2.4 earthquake). It also pulverized the rock. Completely. As I walked on the north side of the Mirror Lake Loop Trail, I didn't see anything right away, but then I nearly slipped and fell on a granite boulder that would normally provide fine traction. I looked and realized the boulders around me were covered with a fine powder up to a quarter inch thick. It looked like volcanic ash, and it occurred to me and my students that the dust would actually be chemically indistinguishable from rhyolite tuff (granite and rhyolite are coarse- and fine-grained varieties of silica-rich igneous rock). It really didn't even feel gritty, and it got all over our shoes and pants.

We were on the far outer periphery of the impact zone, so only a few weakened tree trunks were knocked over. Several are shown in the second photo.

That's all I have on the slide for now. I hope to be able to get closer to the impact zone on my next trip in the area.

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!

The Ahwiyah Point Rockfall: the View I Wish I Had

Photos courtesy of the National Park Service. Photographer: Greg Stock, Park Geologist

The National Park Service now estimates that the March 28 Ahwiyah Point Rockfall had a volume of 43,000 cubic meters, or 115,000 tons. This means that the event was almost 50 percent larger than the 1996 Happy Isles Fall (30,000 cubic meters), and is the largest event since the 1987 Middle Brothers slide (1.5 million tons). The airblast was reminiscent of the Happy Isles event.

These pictures, taken by Greg Stock, the park geologist, show the views I wish I had when I was there last weekend. The top photo is from the switchbacks to Snow Creek, and the other is obviously from the edge of the destruction zone.

For some strange reason, rock climbers have been inordinately interested in this event, and the effect it may have had on some of the Half Dome climbing routes. Via Geology.com, here is a comment string replete with photos from a number of climbers.

Ahwiyah Point Rock Fall Update: Before and After Photos

Now that the Glacier Point Road is open, Yosemite National Park visitors have an opportunity to get a true bird's-eye view of the Ahwiyah Point rock fall that took place in late March of this year. This was an event that changed the look of Yosemite Valley forever, and drives home the point of the rate of geologic change, even on a human time scale.

Many thanks to Doug Nelson, photographer of the image of the slide, taken a few days ago. The top photo was from a 2005 visit to Glacier Point by my field studies class.

Another Look: The Ahwiyah Slide in Yosemite

The Ahwiyah Point rockfall in Yosemite Valley was probably the largest rockfall since 1996, when the Happy Isles fall killed one person and severely damaged the Nature Center (photo here). Luckily the slide a week ago occurred early in the morning so no one was on the trails covered by the event. Access is a bit tricky, but good views of the entire pathway of the slide can be had from the trail north and east of Mirror Lake (the south side of the loop is covered with rockfall debris). Unfortunately (for us geologists) views of the impact area are not so easy; I didn't have time to bushwack across the river, and it was probably still very dangerous in the impact zone anyway.

The first photo shows the entire rockfall zone, from near the top of Ahwiwah Point to the base of the canyon slope on Tenaya Creek. The high rock on the right side is Half Dome, from an angle not often seen by casual tourists (it requires a one and a half mile hike, after all!). The total length of the fall was 1,800 feet.

The second is a zoom on the release point (sorry for the intervening branches; I took about 30 pictures and zoomed only the one time! There were clearer views elsewhere). The nearby trees provide scale; the rock mass was dozens of yards across.

The third and fourth photos provide the only view I could get of the impact zone. Lots of new talus slopes up there, lots of mangled logs, and if you look very carefully at the top of the talus pile, you can see a single tree that survived the onslaught of falling rock.

One more set of photos in the next post!

Nice Media Catch: The Ahwiyah Slide

The largest rockfall in Yosemite Valley in two decades thundered off Ahwiyah Point in late March of this year, setting off seismometers in Berkeley, which recorded a magnitude 2.4 quake from the impact. I posted a number of pictures and descriptions at the time. Now the Modesto (and Fresno) Bee has run a front page article detailing some of the research being done on the slide by Berkeley graduate student Valerie Zimmer (details here).

It's great to see some good geology on the cover of the local news, especially when they get the general details right.

This note was also posted at the other blog I run for the National Association of Geoscience Teachers. We have some great geology field guides for the California-Nevada region you might want to check out, including a geologic tour of Yosemite Valley. Part of the Yosemite tour is posted at http://virtual.yosemite.cc.ca.us/ghayes/roadside.htm.

You Can Never See This View Again. Ever.

The title isn't as ominous as it sounds, but it is true. This is the panorama seen from Tunnel View at the west end of Yosemite Valley, one of the most famous viewpoints in the world, in 2013. But the specific scene above can never be experienced by anyone ever again. Geological forces, instead of acting at a slow incremental pace, moved things tragically fast late last month. A chunk of granitic rock the size of a football field came off the cliff just east of El Capitan (cliff on the left), and the scar will be visible for centuries. The picture below is how it looked today.

The view is fundamentally the same, but the changes are occurring, and the appearance of Yosemite changes with it. See below for a zoom of the cliff near Horsetail Falls, first in 2013, and then how it was this afternoon.

There were a total of seven rockfalls from the site on September 27-28, 2017. One person was killed and two were injured. One report mentions the largest of the falls as weighing 30,000 tons. This wasn't the biggest rockfall in Yosemite's history, not even close. The largest in recorded history was the Middle Brothers slide of 1987, which totaled about 1.4 million tons. Prehistoric rockfalls in the Mirror Lake area were larger still.

Actually, if we were to look at photographs from a decade ago, there would be an additional difference. The 2009 Ahwiyah Point rockfall scar can be seen just right of center, in both of the pictures above (but especially in the upper one). It totaled 115,000 tons, but thankfully injured no one. Check below for a 2009 view of the same spot to compare the difference.

Although partly hidden in shadow, the rock face at the bottom, just right of center (below the snow) is composed of darker weathered rock instead of the white scar seen in the photos above. Geologic change is constant only in that fact that it happens. Sometimes it is imperceptible, and sometimes is rapid and tragic.

2nd Blogoversary! Hanging in There

This week I join NOVA Geoblog, Lost Geologist, Looking for Detachment, and Dinochick (did I miss anyone?) in the ranks of geoblogs reaching their second anniversary! This year I managed to finish my long series on the geology of the Colorado Plateau, and I got off to a good start on a new series on the unheralded geological wonders of the state of California.

I've had a satisfying level of traffic during the year (via Statcounter), with a bit over 115,000 hits since last December. I really love reading the statistics. I had some interesting spikes, once in February when I got linked to a CNN transcript of Bobby Jindal's anti-volcano monitoring speech, in April when I got linked to the heavily trafficked Yosemite Blog (run by one of my earliest students; thanks Loyd!) because of the Ahwiyah Rockfall in Yosemite, and in August when I commented on some giant waves hitting the beaches at Balboa in Southern California. The October spike came when I commented on the Keeler Earthquake Swarm. I guess a lot of people were curious!

As I said at my first anniversary, this continues to be a lot of fun, not just the blogging, but to see the exploration of the world throughout the geoblogosphere. Many thanks are due to Chris at Highly Allochthonous for his blog feed, and also to the producers of the Geoblogosphere News. Both sites have become indispensible sources of news in the earth sciences. I fervently thank everyone who has paid a visit to my site, and appreciate more than you can know the comments and conversations that have taken place here....And, if you are tempted, give it a shot: blogging is fun!

How it was: The Last Days of Fall in Yosemite

We were in Yosemite last weekend, catching the last vestiges of the fall season, and exploring a landscape that was at the end of a cycle. Life was ebbing, preparing for the arrival of winter, which apparently intends to arrive on Thursday (a series of snowstorms is expected). As such, we were probably some of the last people who got to visit Glacier Point this year. It was a beautiful day (I would be more poetic about it, but words start to fail when trying to describe a place like this).

The peak of the fall colors was some time ago. We passed groves of trees that had lost all their leaves, but in some sections of the park, color was still intense. I understand that the eastern hardwood forests are the epitome of fall glory, but I also see wonder in catching the colors spread out in a dark conifer forest as the sun lights up the dogwood and oak understory.

 A spider was feverishly busy trying to catch a last meal for the season.

There were a few flowers still hanging on near the Merced River. This apparently is a Coneflower (my credentials as a biologist have always been suspect). The flowers were on their way out; the petals were gone on the other side of this one.

The Merced River was running slow and clear. Last spring I would have been standing in two or three feet of water at this spot.

We headed up the road to Glacier Point. The air was still and clear, and there were no clouds. The peaks stood out clear as crystal, and I couldn't help taking pictures of mountains and domes I've photographed many times before. It always seems like I am looking for unusual lighting and clouds to spice up pictures of these features, but today I was concentrating on preserving the peaks in plain afternoon sunlight. The pictures make me think of a baseline, a version from which all other pictures can be compared ("what do those mountains look like when they aren't shrouded in mysterious clouds?"). The exfoliation dome of Mt. Starr King appears below.

The Sierra Crest could be glimpsed in the distance, with Mt. Lyell, the highest peak in the park at 13,114 feet (3,997 meters) barely visible. Peaks of the Clark Range a little west of the crest tend to dominate the skyline. A few small patches of snow made it through the summer.

Half Dome sits across the valley from Washburn and Glacier Points. A zoom on the summit revealed no hikers; I'm guessing the cables are down by now, so no one was around.

Mt. Clark is a pretty nice example of a glacial horn, a peak that has been steepened on all sides by the plucking action of the glaciers that were here only 12,000-13,000 years ago.

I was reminded while looking at Tenaya Canyon below Half Dome how much geology changes the park. If you remember this view from any time before 2009, it is forever changed now. The Ahwiyah Point rockfall produced the long white scar down the slope in the center-left side of the photo. It was the biggest rockslide in more than two decades.

Glacier Point offers one of the greatest views to be seen anywhere. The cliffs drop 3,000 feet below one's feet, and there is a unique perspective of the famous waterfalls, since they are being observed from above. Yosemite Falls had the smallest of trickles falling down the face (the bright sunlit cliff). In a few days ice will replace water on the cliff face.

On the way down Glacier Point road, we stopped for a look at Summit Meadow. The willows had turned red, contrasting with the yellow meadow grasses and the evergreen lodgepoles. To get the reflections on water, I had to get out into the middle of the meadow, which is not really a nice thing to do, since the trampled grass and mud is unsightly, and it damages the soils. So I found a way to get there without stepping on grass...

 And there it is, a fallen tree. It was a real balancing act to not fall off.

And that's the way it was. I saw reports that it was very windy in the valley today, and that snow level will be down to 3,500 feet or so by the end of the week. Yosemite will be a very different place by the weekend.

Whispers and Echoes from the Past, When Half My DNA Visited Yosemite National Park

While my "Vagabonding on Dangerous Ground" journey took me far north of my usual haunts in the Sierra Nevada, I had an unexpected encounter with Yosemite National Park while I was gone. We had a brief visit with my mom as we drove home from our long trip. While there, I saw an ancient looking leather booklet, one of those little photo/scrapbooks that were popular in the days when pictures were printed on paper. It was full of pictures of half my DNA visiting Yosemite National Park in the early 1940s. My love for Yosemite is literally in my blood!

The "half DNA" of course was my mother when she was just a few years old. As I flipped through the photographs, I realized that I have been standing in these same places, snapping pictures of my own. It was possible to put them side by side. I wondered to myself, how has Yosemite changed in those 73 years? And more importantly, how has Yosemite NOT changed?

The most noticeable difference is the vegetation. Trees that are in some pictures aren't in others. That's not much of a surprise, given the fact that many trees can grow to maturity in that time period. The man-made structures underwent changes as well. The Tunnel View Parking Lot (in the top picture) was completely renovated and rebuilt just a few years ago. The "Swinging Bridge" at the Swinging Bridge Picnic Area (below) no longer swings. It was replaced by a more stable pedestrian bridge a couple of years ago. The cute little girl on the left in the picture is mom.

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Other changes are more subtle, at least in slightly fuzzy photographs from nearly three quarters of a century ago. A number of serious geologic events have taken place, including three or four of the biggest rockfalls and debris avalanches ever witnessed in the park. I even witnessed one of them, when a large slab came off the face of El Capitan in 2010. The Ahwiyah Point rock fall in 2009 permanently changed the appearance of Half Dome, and the 1996 Happy Isles rock fall did the same to the cliffs below Glacier Point. Four "hundred-year" floods scoured the river channels in the valley in the last 50 years or so, washing away buildings and camp facilities.

The things that didn't change are the things I realized were important. Yosemite National Park is a treasure, and the idea of preserving it for future generations was America's best idea, as the Ken Burns documentary pointed out in beautiful fashion. In one sense, Yosemite is where it all started. In 1864, Abraham Lincoln gave Yosemite Valley to the state of California, with the idea that it be preserved in perpetuity. Later, in 1872, Yellowstone became the first official national park, and Yosemite followed in 1890. The idea of protection and preservation moved forward in fits and starts, with some failures and other hard fought victories. Hetch Hetchy Valley, the second "Yosemite" in the park, was inundated under the waters of a reservoir in 1923. But the ridiculous idea of building a tramway to Glacier Point was stopped cold in the 1970s. The totally crowd-pleasing, but totally unnatural nightly firefall ended in 1968. As I looked through these ghostly pictures of the past, I realized that I've been able to experience the park much as my family did all those years ago. The park has changed, but for the most part the change as been directed towards an appreciation for the natural environment, and not towards profit-making opportunities (although that happens).

My grandparents took my mother to Yosemite in a time and in circumstances that were difficult. It wasn't that the park was inaccessible. The "All-Weather Highway" (Highway 140) was completed in 1926, and other good routes were available. But with the war going on, resources were limited. In those days it would have been quite the challenge for a family of modest means to find their way to the park from Southern California. Although it costs more these days to enter the park, one can stay in relatively inexpensive campgrounds and still have an affordable experience in one of the most spectacular landscapes on the planet. The park can be very crowded at times, but those who are willing to walk a bit can find absolute solitude in the 95% of the park that is officially wilderness land.

Yosemite National Park remains a wonderful place, despite budget constraints and government neglect. The rangers, park personnel, and volunteers do the best they can with the resources they are given. The idea of national parks is still America's best idea, and the parks deserve our vigilance. Threats from those who would profit from our most beautiful landscapes should be stopped, and that's only going to happen if those of us who love the parks keep the pressure on our political representatives. It's never easy, but it needs to be done. I want my pictures of today to compare favorably with the three dimensional total sense immersion photographs and virtual reality images that will be taken by my grandchildren 75 years from now.

If you want to be involved, join the Yosemite Conservancy. Most national parks have a natural history association that fights for the good of the parklands. They deserve your support as well.