Monoliths with names such as “The Yosemite Valley Floor” rise thousands of feet high above the Yosemite Valley floor’s meandering tracks. El CapitanSentinel Rock and Sentinel Rock are like mythological giants of the past.
They have been dominant for a long time, but it is not clear. Previous estimates of their emergence were anywhere from tens to many millions. Only 15 million years ago.
New research has revealed that previous attempts to determine the time of Yosemite Valley’s evolution were not accurate. The stunning granite skyline is believed to have developed over the last 10 million years.
A research team from the University of California Berkeley found that most of the sculpting may have been done in the past 5,000,000 years.
“This upland surface that people are familiar with from parts of the Tioga Road and Tuolumne Meadows – that’s a very old landscape,” “ UC Berkeley glaciologist Kurt Cuffey.
“The big question is: What do you think about the deep canyon?” Is it also very old or relatively young? It’s quite young, which is what our study revealed. The timing of the event is best guessed at between 3-4 million and 10 million years ago. But, for the incision to begin quickly, we can go back as far as 10 million years.
Yosemite National Park sits among the jagged peaks of the Sierra Nevada – a mountain range created from a chain of volcanos generated by the clashing of continental plates around 100 million years ago.
Over time, the elements continued to polish the granite, strip away the limestone, and shale, creating natural features around the world that are known for their raw beauty. While forces beneath the surface continue to push the bedrock higher.
Yosemite Valley itself is home to a handful of monoliths that stand out for their imposing facades – near-vertical rock faces that attract photographers, naturalists, and tourists … not to mention rock climbers willing to brave life and limb to scale them.
The rocks are easy to examine for clues about aging, but the carving of the flanks is a different story.
“We know the Sierra was a high mountain range 100million years ago, as the granite was forming at deep. It was a chain if volcanoes, which might have looked something like the Andes Mountains in South America. “ Yosemite National Park geologist Greg Stock.
“The real question is whether the elevation has been falling through erosion or whether it fell some and was then raised again.”
Many signs are visible around Sierra Nevada that both mechanisms may be at work. These include steepening slopes, exposing parts of the range for increased weathering or erosion.
Geologists extrapolating these events suggest that similar phenomena could have been at play in Yosemite many millions of years earlier.
The researchers went beyond assumptions and used a technique by David Schuster, senior author and UC Berkeley geochemist. This was not based on models of shifting landscapes but evidence embedded in the prominent rock formations.
Called helium-4/helium-3 ThermochronometryThis involves assessing the helium-4 isotope. Over time, it slowly decomposes into helium-3.
At temperatures above 30 °C (around 86 °F), this change sharply escalates, providing a means of approximating the rate of cooling of a distribution of rock samples.
Researchers can use these results to determine how long a large rock has been sitting above the crust’s warmer parts, much like a thermometer.
Researchers subjected 16 mineral samples from Yosemite Valley to thermochronometry. This allowed them to chart the history of cooling in the massive expanses of volcanic rock.
Now, we might imagine that a river carved a hole in the Sierra Nevada geology over tens to millions of years, paving the way for what would become a valley.
About 5 million years ago, renewed activity under the crust tilted it, speeding up water’s flow, and deepening ravine.
Glaciers carved the familiar cliffs we see today, following a cooling in the climate over the past 2 to 3-million years.
Millions of people visit Yosemite each year to be awed by these monolithic giants. You can see formations that are as old as the Earth in just one glance. This makes those feelings even more powerful. dinosaurs – and yet as recent as humanity’s own emergence.
This research was published in Geological Society of America Bulletin.
