Yosimite Rock
Half Dome is perhaps the most recognized symbol of Yosemite. Rising nearly 5,000 feet above the Valley floor, it is one of the most sought-after landmarks in Yosemite. Some people even hike or rock-climb to the top!
Yosimite Rock
Cathedral Rocks and Spires form the eastern side of the canyon through which Bridalveil Creek flows. Some people think these rocks, just opposite of El Capitan, are even more impressive than El Capitan!
More than 100 climbing accidents occur in Yosemite each year; of these, 15-25 parties require a rescue. Climbing in Yosemite has inherent risks and climbers assume complete responsibility for their own safety. The National Park Service does not maintain routes; loose rock and other hazards can exist on any route. Rescue is not a certainty. If you get into difficulties, be prepared to get yourself out of them. Know what to do in any emergency, including injuries, evacuations, unplanned bivouacs, or rapid changes in weather. Safety depends on having the right gear and the right attitude. Practice self-rescue techniques before you need them! Courtesy is an element of safety. Falling rock or gear is a serious hazard. Be careful when climbing above others. Do not create a dangerous situation by passing another party without their consent.
Geologists from the University of California, Berkeley, employed a novel technique of rock analysis to get a more precise answer, and concluded that much of Yosemite Valley's impressive depth was carved since 10 million years ago, and most likely even more recently -- over the past 5 million years. This shaves about 40 million years off the oldest estimates.
While the scientists are unable to be more precise, the new estimate is the first to be based on an experimental study of the granite rocks in and near Yosemite, rather than on inferences based on what was going on elsewhere in the Sierra Nevada.
Shuster's technique, called helium-4/helium-3 thermochronometry, reconstructs the temperature history of a sample of rock based on the spatial distribution of natural helium-4 in minerals, which is measured by comparison to an artificially-produced uniform distribution of helium-3. Because temperature increases with depth underground, the temperature history can tell when a rock was uncovered as the landscape eroded.
"The temperature of the rock is a function of the surface lowering down into it," Shuster said. "It's very analogous to removing a down comforter -- the rock beneath it progressively gets colder. This progression through time with the rock cooling is what we get from the geochemistry and thermochronometry."
The expectation is that granite bedrock exposed on the broad uplands of the Sierra should show a long history of cool surface temperatures, since they've been exposed for tens of millions of years longer than bedrock more recently exposed on the floor of Tenaya Canyon, which feeds into Yosemite Valley from the northeast.
The experiments, conducted at the Berkeley Geochronology Center, indicated that, while rock from the uplands has been close to the surface for about 50 million years, bedrock at the bottom of Tenaya Canyon has been exposed much more recently. The temperature history of the rock obtained from the bottom of Tenaya Canyon -- from an exposed area of bedrock at the base of Half Dome -- indicates that it was more than a kilometer underground 10 million years ago, and most likely only 5 million years ago. This means that a kilometer of rock was eroded away since that time.
The geologists collected samples of granite bedrock from nearby highlands and the bottom of Tenaya Canyon, but not from the bedrock bottom of Yosemite Valley itself, which lies buried under about 500 meters (1/3 mile) of sediment that today forms the valley floor. But since the two formed at the same time, one can infer the timing of the formation of Yosemite Valley from the time of the scouring of Tenaya Canyon.
"The brief history of Yosemite Valley would be that there was some kind of valley in place for tens of millions of years -- a river-carved canyon associated with the ancient Sierra Nevada. And then, in the last 5 million years or so, renewed uplift of the range through westward tilting caused rivers to steepen and deepen the canyons that they were in," Stock said. "So, that probably carved out more of Yosemite Valley and may have started forming Tenaya Canyon. And then in the last 2 to 3 million years, as the climate cooled and glaciers came down through Tenaya Canyon and into Yosemite Valley, they further sculpted the rock, deepening those valleys. And in the case of Yosemite Valley, widening it out considerably. So, there's some component of an old Yosemite Valley. But I think this recent work shows that much more of that topography is younger, rather than older."
An 1,800-cubic-yard slab of rock cartwheeled down the cliff, shattered and sent boulders and fist-size granite shrapnel toward the edge of Curry Village and its more than 500 tent cabins, regular cabins and hotel rooms.
Park officials used a helicopter to get a closer look at the rock face Tuesday afternoon and again Wednesday morning, after the bigger slide. No findings have been announced, though park geologists are theorizing that recent rains may have lubricated the rock face just enough to trigger the rockfall.
Around 9 a.m. Tuesday, the pair were in their Dodge Ram rental truck on Highway 140 near the Arch Rock entrance when they were hit by rocks that fell 1,000 feet from above the roadway. Officials said the force of the impact pushed the truck off the road, where it landed on the embankment of the Merced River.
Officials said the rockfall comprised of about 185 tons of rock and it impacted about 500 feet of the road. Highway 140 was closed through Wednesday afternoon as crews cleared the scene and performed temporary repairs.
The USGS began studying the hazards of rockfalls at the park after a 1980 incident on the upper Yosemite Falls Trail killed three people and injured at least 19 others. It was "the greatest mass casualty incident in Yosemite National Park's history," the report noted.
More than 1,000 rockfalls have occurred over the last 150 years, according to the park, mostly in winter and early spring, "during periods of intense rainfall, snow melt and/or subfreezing temperatures."
Officials urge Yosemite visitors to be aware of their surroundings, as rockfall hazard zones occur throughout the park, near any cliff faces, and are unpredictable and may happen at any time. They offer these tips:
Parker, of Sebastopol, was climbing alone at 5:45 p.m. without ropes or any other climbing equipment on a rock face called the Matthes Crest Traverse, above Tuolumne Meadow, when a half-dozen other climbers on the route saw him fall, according to Ashley Mayer, a Yosemite spokeswoman.
"The section where he was climbing is a bit more difficult than the standard way," he said. "There is a little more loose rock up there. ... If you are dehydrated and cramping ... that would certainly impede your ability to climb."
In 1996, a rock slide in the same area sent as much as 162,000 tons of rock plummeting more than 2,000 feet, killing one visitor and felling 500 trees. A slide in 1999 killed one climber and injured three others while narrowly missing the popular campground.
Another photographer, Rena McClain, a nurse from Dover, Del., told The Associated Press that she had her back to the granite face when she heard what sounded like a thunderclap. She whipped around and saw a giant cloud of rock and dust coming down.
These films underscore the fact that Yosemite has long been known as a rock climbing Mecca. Serious climbers from around the world aspire to test themselves on the soaring granite walls of cliffs like El Capitan, Half Dome, Sentinel Rock and so many more. But make no mistake, there are plenty of shorter and easier climbs here in Yosemite as well that are more suitable for mere mortals and aspiring rock climbers.
From your cabin rental at The Redwoods In Yosemite, you can also make a quick exploration of the rock climbing right in Wawona. Look for areas like Mortar Rock or Powerline Rock for nearby climbs. Plus, there are also many routes on nearby Wawona Dome, though there is a longer hike to get there.
There is only one rock climbing guide service authorized to take you climbing in Yosemite National Park, the Yosemite Mountaineering School (YMS). YMS offers rock climbing lessons, guided climbs, and special skills workshops that can walk you through learning to lead, self-rescue techniques, or even help you prepare for your first big wall.
Over time, the elements have continued to polish the granite and strip away the limestone and shale to create natural features famed around the world for their raw beauty, while forces beneath the surface have continued to thrust the bedrock skyward.
To move beyond assumptions, the researchers employed a technique developed by senior author and UC Berkeley geochemist David Schuster; one based not on models of a shifting landscape, but evidence baked inside the minerals that make up the prominent rock formations.
Much like a thermometer can be used to judge how long a cake has been cooling out of the oven, these results can provide researchers with a clue on how long a sizable rock has been above the warmer parts of the crust.
With the cooling of the climate in the past 2 to 3 million years, glaciers took their icy chisels to the valley floor and its rock walls, pushing back the boundaries and sculpting the familiar cliffs that dwarf us today.
The California park shut down its El Portal entrance on Tuesday, after one rock slide killed visitors Georgios Theocharous, and Ming Yan, a married couple from San Jose, according to NBC News. The entrance was reopened the next day.
Another entrance was closed on Friday evening from a rock slide, the park reported, as a winter storm causes hazardous conditions in the mountainous terrain. Those traveling in the park are encouraged to carry an emergency kit and chains, according to local ABC affiliate ABC30.