Showing posts with label Half Dome. Show all posts
Showing posts with label Half Dome. Show all posts

Saturday, July 12, 2014

Out of the Desert and Back to the Green Hills of Home

Today wraps up the story of a week-long journey through the deserts of the southwest. I've been telling the story as if in real time, so it sounds like I'm just now arriving home, but actually we finished the trip just over a month ago. It's a time warp of sorts. I'm about to leave on another trip, this time to British Columbia and Alberta.

Coming home. You can live in a boring place, a place that is the worst in the country even, but coming home is coming home. There is the familiar kitchen, the television, the well-worn couch. The weeds. The office. To me, home is something bigger. It's the landscape that surrounds my home region. Basically those places within a day's drive that I've seen over and over. My home starts at the summit of Tioga Pass in Yosemite National Park. It's a three hour drive from my house, but a trip doesn't really begin until we've gone over the summit, and on the return trip we feel home the moment we get there.
Compared to the dry lands we had just explored, the mountains have a richness of moisture. It's not nearly what it should be, for we are still in the grip of a horrendous drought, but some late spring snow was still lingering in the high places. We felt such a relief at the sound of babbling creeks.
Tuolumne Meadows is the accessible part of the Sierra Nevada crest in Yosemite National Park. The meadows lie at 8,000 feet, and the surrounding mountains reach elevations of just over 13,000 feet. This region was the source of glaciers that scoured the deep U-shaped valleys of Yosemite and Hetch Hetchy. At one time there was an ice cap at Tuolumne that was more than 2,000 feet thick that spilled out in several directions, including Tenaya Creek which holds beautiful Tenaya Lake (top picture).
John Muir talked about the Sierra Nevada high country as the "gentle wilderness", and that's been my experience most of the time. I've seen violent storms across the Basin and Range and Colorado Plateau, and some have been terrifying because we were camped out there and had nowhere to hide or take shelter. If a storm blows in while I'm exploring Yosemite, well, we just jump in the car and go home. We can come back the next day.
We had already driven three hundred miles this day, so the sun was getting close to the horizon. Photographers say that evening and morning are the best times for good shots, given the nice contrasting shadows instead of the washed out colors from a noonday sun.
There was a storm over the Basin and Range that we had just skirted. We got a few drops, almost enough to turn on the wipers. From a distance it looked menacing. But all was calm for us in the meadow.
We made a last stop at Olmsted Point for a look at the sunset on Half Dome. We then headed down the hill, and returned to our home. It was nice to be back, but of course a few days of sloth and we wanted to get on the road again. We are restless souls sometimes!

Monday, May 5, 2014

Two Serene Hours in a Very Noisy Place: The North Valley Trail in Yosemite Valley

Yosemite Valley is an awe-inducing place, a place that was the inspiration for my current series on "What are the Most Incredible Places You've ever Stood"? I've been there many times and I never get tired of it. It is a destination for three of my field trips every year. It is an easy thing to drag a bunch of students up there (you make it required and stuff them on a bus), but how does one get past the sheer elegance of the scenery and explain to students the grandeur of the geological story of Yosemite as well? Part of it is letting them find out for themselves.

It's a bit of a trick to take 40 students to Yosemite on a busy Saturday in May. Buses are allowed to park in only two or three spots in the valley, and an extended discussion of geology is not possible in a place like the Wawona Tunnel View (above and below). It's simply too crowded with noisy buses and motorcycles and hundreds of tourists enjoying a first view of the valley, and it's really not fair to have a bus parked there hogging a premium spot. So we park the bus at Yosemite Lodge, and I set them free to wander through the an extent. We make appointments. They find their way through the valley floor on the free trams, and we meet each other at a few of the most important localities (principally the Happy Isles rockfall site and a vantage point where we can talk about Half Dome and Yosemite Falls). It works well most of the time because they get a sense of exploration to go with the "learning".
I like the schedule for a different reason. The students have about two hours to find the visitor center and make a series of observations while making their way through the tram system to the other end of the valley. That's two hours that I can use to make some observations of my own, along with a bit of exploration. The trams are great, but nothing can compare with walking the length of Yosemite Valley on one of the less busy valley trails. Two hours of brisk walking for me equates to about six miles. I headed up the trail to Lower Yosemite Falls, trying to make my way through hordes of tourists (and a fair number of my students headed the same direction). It was crowded and noisy, but only a few hundred yards further I had the trail largely to myself.
 The North Valley Trail follows the base of the cliffs above the roads and valley developments. It is surprisingly quiet; I couldn't hear the traffic far below, only the breeze through the conifers and pleasant song of a bird I couldn't see or identify.
I soon passed a superb example of a talus slope at the base of Yosemite Point. In many places the cliffs of Yosemite are bold and vertical, but in other places there are recessed coves with extensive slopes of fallen rocks. The difference lies in the pattern of jointing in the rock. Granitic rocks form deep in the crust miles below the surface under great pressure. As they are exposed by erosion, the rocks expand and fracture. The composition of the rock seems to determine the spacing of the joints, and when they are far apart, bold cliffs occur. When they are closely spaced, rock falls are common and talus slopes are the result.
The trail climbs several hundred feet above the valley floor, offering views in both directions. Across the valley stands Sentinel Rock, one of the most imposing cliffs in Yosemite (although it sometimes gets lost in the scenery, being located across the valley from Yosemite Falls). On the other side are the cliffs of the Three Brothers. The cliffs that make the three brothers are more easily seen from the other side, but from my vantage point I could see the scar of the 1987 Three Brothers rockslide, which dumped something like 600,000 cubic yards of debris onto the valley floor. Luckily no one was hurt, since the park service had some warning that a big slide was imminent and closed the road at the base of the cliff. It was the largest mass wasting event in the recorded history of the valley.
John Muir and other earlier visitors remarked on the open park-like aspect of the woodlands on the valley floor. Fire suppression since the establishment of the park in 1890 has allowed the growth of a thick forest across most of the valley, but below the Royal Arches and Washington Column there are some beautiful old oaks that recall the original state of the valley at the time it was discovered by Europeans (the Miwoks and other first nation people have known of the valley for thousands of years).
Half Dome soon became visible as I worked my way towards Mirror Lake.
 The Dogwoods were still blooming along the side of the trail.
After three or four miles of walking I arrived at Mirror Lake. The "lake" is more of a wide spot in Tenaya Creek that developed as a result of a gigantic landslide in prehistoric time. The creek formed a series of ponds behind the rockslide that in springtime reflect the surrounding cliffs, especially Mt. Watkins and Half Dome. By summer Tenaya Creek often runs dry (especially this year with the drought conditions). On Saturday it was beautiful, but also crowded. I set off towards Happy Isles and soon left the crowds behind.
Half Dome from the vantage point of Mirror Lake is the very definition of "looming". It is nearly 4,000 feet of steep cliffs. Another major mass wasting event took place near here in 2009, the Ahwiyah Point rockfall. It involved something like 115,000 tons of granitic rock. Luckily it happened early in the morning and no one was hurt.
The small details are easy to miss in a crush of people. I enjoyed some more Dogwood flowers...
...and the hard work of huge bumblebee in the Lupine blooms.
After I met with the students at Happy Isles, we started making our way back to Yosemite Lodge. I took one look at the packed tram, and decided it would be nicer to walk back. The direct route was two or three miles, and I had a fair chance of beating the tram (the dozen or so stops and the heavy traffic made for a slow motorized journey). Along the way I was thrilled to see a White-headed Woodpecker for the first time.
Our final stop was in a meadow at the base of Yosemite Falls. It provided an outstanding view of Half Dome where we could discuss the origin of the iconic feature. Soon after we were back on the bus and headed home. It was a spectacular day!

Tuesday, April 22, 2014

Where are the Ten Most Incredible Places You've Ever Stood? A New Blog Series...

What is the most incredible place you have ever stood? That thought occurred to me this last weekend when I got up to Glacier and Washburn Points in Yosemite National Park. For those who are less familiar with the park, Glacier and Washburn Points are on the rim of Yosemite Valley, not on the valley floor. As such, they give a bird's-eye view of one of the most incredible pieces of land in the world, and though a million or more people may stop there during their visit to Yosemite, I'll bet the majority of park visitors don't venture up that way. It's something like 20 winding miles outside of tourist central on the valley floor, and perhaps hard to squeeze in when trying to rush through the park in the limited moments afforded by a vacation.

Is the high point on the rim of Yosemite Valley the greatest spot I've ever stood? I'm not sure yet! This is the opening salvo of a new series called the Ten Most Incredible Places, and I'm going to decide number one somewhere along the way before I finish. I'd also like you to consider what your own most incredible places are. I'd love to have you share them, perhaps in your own blog if you have one, or share them in the comments here. I'd be glad to post a few of your wonderful pictures as I consider my list. Be sure to include some reasons why a particular place stands out, whether geological, biological, spiritual, or personal.

I'm looking forward to seeing some incredible places!

Sunday, April 20, 2014

Vernal Fall in Yosemite and a Sense of Scale (or, How to Feel Very Small)

It's a sense of scale that helps us keep perspective. I was at Washburn Point in Yosemite National Park today, and I took a few shots with the zoom of the same spot across the way.

We have a bunch of people apparently enjoying themselves on a flat slab of rock next to a fair sized river. But why the fence? Why aren't they letting people cool their feet in the river on this reasonably warm day?
Maybe it is the fact that they are standing at the top of a 318 foot (97 meter) waterfall. And a hell of a dangerous one. It is far too easy to miscalculate just how powerful a flowing river can be. Water only a foot deep can easily knock you off your feet, and the rock can be exceedingly smooth from glacial erosion and slick with algae. Too many people on the wrong side of the fence have lost their lives.
As we pull back even more, we can see the full extent of the waterfall, and the insignificance of the people gathered around the brink. They are now barely visible. This is Vernal Fall on the Merced River just upstream of Yosemite Valley. It formed because the glaciers that once flowed through the valley plucked away at highly jointed rocks forming what is called a glacial stairstep. It is just one of many spectacular waterfalls in Yosemite that leave one feeling awestruck.
And yet, Yosemite is such an incredible landscape of gigantic granite domes and deep glacially carved gorges that even a 318 foot waterfall can almost be lost in the richness of scenery. As I noted before, I was on Washburn Point, about two miles away as the crow flies (or more probably the raven, given their abundance here) from Vernal Fall. In the picture below, Vernal is the smaller of the two gigantic waterfalls. The upper one is Nevada Falls, which drops 594 feet (181 meters). 

To the left of Nevada Falls is Liberty Cap, a glacially smoothed granitic dome. To the left of Liberty, the dark rounded form of Half Dome is seen from an unfamiliar angle. From this angle it is clear that if anything, it should be called Three-Quarters Dome, or even Four-Fifths Dome. 

Half Dome was never covered by glacial ice, and was formed instead by exfoliation, the tendency of rocky monoliths to break off slabs of rock as the pressure is released as the rock is exposed at the surface. The slabs mostly remove corners and edges, giving the rock a rounded profile. The steep face of Half Dome was a prominent joint, a vertical crack that also forms from pressure release. The "missing" half was undercut by the glacier below in Tenaya Canyon and quarried away down the valley.

Feeling small yet?

Thursday, April 17, 2014

One of the World's Most Precious Places, Under the Volcano

Yosemite Valley, hands down, is one of the most extraordinary places on our amazing planet. I have been going to Yosemite National Park three or four times a year for the last quarter century, and I never get tired of spending time there. The thousand square miles of national park that surround Yosemite Valley are incredible, but the valley itself is hypnotic. I would hope that everyone could visit the park at least once, but it becomes something special when you can see it throughout the seasons, in all the different moods of the place.
The mood in the park on Saturday was expectant. The snowmelt has been filling the rivers a little (the drought continues unabated), and the first hints of green are showing up in the meadows and oak woodlands on the valley floor. Snow still lingers in the high country. The Dogwoods are just hinting at the possibility of a bloom. Changes will be coming fast in the next few weeks (and the long dry spell of summer will begin soon; much sooner than we have hoped).
The valley is a showcase for learning about glacial features and glacial erosion, although several aspects of valley scenery are not anything like typical. But if the subject is hanging valleys, Yosemite has no peer.

Big glaciers carve deeper valleys than little glaciers. When the massive Merced River glacier joined the Tenaya Creek glacier (with its spillover of additional ice from the Tuolumne Meadows icecap), the combined force of the two ice rivers produced the deep trough of the main valley, 3,000 feet deep (even deeper if the sediments filling the valley floor are removed). The tributary glaciers in Yosemite and Bridalveil Creeks were much smaller and couldn't cut nearly as deep. Their valley floors were left hanging high above the main valley, and today high waterfalls spill over the edges. Bridalveil Fall (in the pictures above and below) is 620 feet high, nearly four times the height of Niagara Falls, but it's one of the smaller waterfalls in Yosemite Valley.
Yosemite Falls is usually described as the highest waterfall in Yosemite Valley, but that depends on which geographer one is arguing with. It has three sections, an upper fall with a drop of 1,425 feet, a cascading central section, and a final sheer drop of 300 feet. It may the fifth or the seventh highest water in the world, but if one is talking about essentially unbroken drops, it's not even the tallest waterfall in Yosemite Valley. That honor goes to Ribbon Fall, shown in the photo below. It drops 1,612 feet, nearly 200 feet more than the upper section of Yosemite Falls. I imagine some first-time visitors mistake it for Yosemite Falls as it is seen first during the drive into the valley. Most people never see it at all though, because it dries up by late spring in most years.
I started up the valley trail from Bridalveil Falls, and ended up with a new view I have not seen before. The trail winds along the base of the Cathedral Rocks, with a sheer precipice of thousands of feet. Being at the base of such high cliffs is awe-inspiring.
Half Dome gets all the attention, but North Dome is beautiful in its symmetry as well. It stands across from Half Dome on the other side of Tenaya Canyon. And it's a whole dome!
And then there is Yosemite Falls. It never fails to amaze me with its stunning drop of nearly half a mile, and it becomes even more amazing when one realizes that it is misplaced in a manner of speaking. Can you see the cleft in the shadows to the left of the waterfall? The cleft provides a route for the trail that climbs up to the top of the waterfall and nearby Yosemite Point.

The dark cleft used to be the path of Yosemite Creek! The falls used to be an inconsequential side canyon but the glacier coming south from the high country pushed up a moraine, a pile of glacial debris, and blocked the normal channel of the canyon. The stream's new pathway took it over the brink of the cliff.
I mentioned the term "under the volcano" in the title because when you stand in the bottom of Yosemite Valley, you are within the frozen magma chambers of a series of volcanoes that once existed here, just five miles or so above. There are eight or nine individual intrusions that make up the valley walls and different susceptibility to erosion has caused the formation of a series of reentrants and coves along with the bold battlements of cliffs like the Cathedral Rocks or El Capitan. Many glacial valleys have long monotonous walls that aren't nearly as appealing a place as Yosemite.

Yosemite is indeed one of the world's most precious places, and I am forever appreciative of living nearby, and being able to share it with you. Enjoy!

Sunday, March 9, 2014

Viewing Half Dome from the Great Valley

Once or twice a year the air clears in the Great Valley. Our valley as great as it is, is a closed basin. The Sierra Nevada and Coast Ranges make it hard for air pollution and dust to move out of the region, and as such the cities of the San Joaquin Valley (south of Stocton) often appear on the top ten "most polluted air" lists. On those few clear days, my eyes drift east towards the Sierra Nevada, and if I am on the way to Turlock, I stop on Hickman Road just south of the Keyes Road intersection and see if Half Dome is visible. For the last two days, it's been visible.

It's not easy to see. Half Dome towers over Yosemite Valley by about 4,000 feet, but the orientation of Yosemite Valley and even the curvature of the Earth make it a challenge unless one knows exactly what to look for. The intervening foothills block the view from most directions. It is only a narrow part of the valley that is framed by the Merced River canyon allows the dome to be seen. In the establishment shot above, nothing is visible. One has to go to the zoom.
 In the picture above, Half Dome is visible, but is not well framed by the snow on the peaks behind. It's almost in the dead center of the picture above, but still hard to see.
 Zooming in a bit more, the outline of the dome with just a bit of snow on top becomes visible (just a bit right of center. If you haven't seen it yet, I drew in the outlines below.
It isn't the clearest of shots. I got a clearer shot a few years ago (look below). Even at that, the issue of visibility from the valley has been an occasional tempest in a teapot, with a few folks arguing that such a view was impossible, and that someone had been photoshopping. Great idea, but beyond my skills!

UPDATE (3/10):Went to Turlock today after a half inch of rain overnight. The pictures I took today show more convincing details, including the top of El Capitan. See below:

And here is the annotated version with the top of El Capitan added.

Saturday, November 2, 2013

The Way it Was Today: Yosemite Valley in November

What a wonderful week! I had the privilege of visiting the most beautiful place in the world twice in the space of a few days. It's true I was taking a bunch of students with me, but we were learning geology in one of the most spectacular settings possible and it was a fine and enthusiastic group. For some it was their first visit to the valley. For others it was the first time seeing the place in a geological sense.
It was an eventful week as well. A storm blew through, leaving a few inches of snow in the valley, but it was all but gone by the time we arrived this morning. Last week there were lots of leaves on the trees in full glory of color, but things were dusty. Today the ground and air were moist, the forest smelled sweet, but there were fewer leaves on the trees.

Our first stop was to visit the Tunnel View, a spot just a few hundred feet below where the valley was first discovered by Europeans in 1851. There was trouble between American settlers and the local Native Americans, so a militia had been raised to search them out. Their medical officer Lafayette Bunnell was entranced with the valley and wrote a glowing account of its beauty.

I seemed to be concentrating on Half Dome a lot today. We had arrived in a large bus, and buses aren't allowed to park in many parts of the valley, so we toured on the free trams with appointments to meet at several locations. I elected to walk between points, and had a few new angles with which to view the iconic chunk of granitic rock (granodiorite, to be specific).

Despite the appearance, the dome is not really in half. It might be more properly called Three-Quarter Dome, although I prefer the Native American name of Tis-sa-ack. The south east flank is a classic exfoliation dome, shaped by the slabbing off of the corners and edges in response to the release of pressure as the rock was exposed by erosion. The steep northwest face is a joint surface that was exploited by glaciers that flowed beneath the face of the dome.
There are other lesser known domes, such as North Dome, seen below. It is the rounded edge of a long ridge of granitic rock. Like Half Dome, it was formed by exfoliation. Glacial ice never covered it. North Dome lies above Tenaya Creek, across from the face of Half Dome.
I was walking from Yosemite Lodge to Happy Isles. I started by wandering through the forest in an unfamiliar direction and almost immediately discovered the central receiving facility for all the raw sewage in the valley (I don't know this for sure, as the building was locked and unlabeled, but the stench was convincing). I reconsidered my route and headed out to the meadow near Sentinel Bridge. I was rewarded with a beautiful panorama of the Cathedral Rocks and the Three Brothers (below).
I said there were fewer leaves, but they certainly weren't gone by any means. Fewer leaves means that the remaining ones stood out in bolder relief.
The Merced River continues its late season serenity. Low flows provide marvelous reflective properties. The picture below is from a stretch of the river just downstream of the tent cabins at Curry Village.
The ravens were out in force. I stopped for a snack and they were flanking me. When I got up to discard my trash, they were thinking about seeing what was left in my pack. I found myself imagining that they will be the next truly intelligent being to evolve after we humans are gone. Like us, they seem capable of surviving practically anywhere (the deserts of Death Valley to the high peaks of the Sierra Nevada and across the desert southwest), and they are probably already smarter than the average touron in Yosemite (it's how they stay fed).
After meeting with the students at Happy Isles, we started back across the valley to Yosemite Lodge. I decided to walk and see if I could beat the tram. I did, by about 10 seconds (Unlike the tram, I didn't have to stop, and I could take the shortest route along roads and trails). I snapped a few shots while rushing along the road. Below is another view of North Dome, and a side of the Royal Arches, a form of exfoliation in reverse.
Washington Column is a steep cliff that overlooks the Mirror Lake area. The largest slide known from Yosemite Valley occurred here a few thousand years ago, forming the lake (that is a lake only seasonally). It may have been about twenty times larger than the biggest historical mass wasting event, the Middle Brother slide of 1987, which involved 600,000 cubic yards of granitic rock.
As I got closer to our final stop, I had one more wonderful view of Half Dome. The late afternoon sun was casting dappled shadows across the meadow. It was another beautiful day in a wonderful place. In a few more short weeks it will be winter!