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Tibetan plateau began to rise 30 million years ago, says a new study
Phayul[Saturday, August 18, 2012 19:41]
DHARAMSHALA, August 18: The rise of the Tibetan plateau, called the roof of the world, began much earlier than previously understood, a new report has found out.
In a research published online in the journal Nature Geoscience, researchers have discovered that the growth of the Tibetan mountains and plateau began as early as 30 million years ago.“Our study suggests that high topography began to develop as early as 30 million years ago, and perhaps was present even earlier," Eric Kirby, associate professor of geoscience at Penn State said in a statement. It was until now believed the high mountains in eastern Tibet developed during the past 10 to 15 million years, as deep crust beneath the central Tibetan Plateau flowed to the plateau margin, thickening the Earth’s crust in this area and causing the area to rise. Using radioactive dating, Kirby and his team found that the uplift began twice as early.The study may help scientists better understand the complicated processes going on beneath the Himalayan Mountains and the Tibetan Plateau.
The Tibetan Plateau, with an average elevation of about 16,000 feet (4,900 meters), lies at the intersection of the most vigorous collision of continental plates on the planet, where the Indian continental plate rams into the Eurasian plate and dives beneath it.
The Indian tectonic plate began its collision with Asia between 55 and 50 million years ago, but “significant topographic relief existed adjacent to the Sichuan Basin prior to the Indo-Asian collision.”
Kirby and associates from around the world took samples from the hanging wall of the Yingxiu-Beichuan fault, the primary fault responsible for the 2008, Wenchuan earthquake, and used a variety of dating methods including the decay rate of uranium and thorium, helium in the minerals apatite and zircon, to tease out the ages of the rocks, which tells when they formed and gives clues to when they lifted.
They also used the fission track dating, an analysis of tracks or trails left by decaying uranium in minerals in apatite and zircon. “These methods allow us to investigate the thermal regime from about 250 degrees Celsius (482 degrees Fahrenheit) to about 60 degrees (140 degrees Fahrenheit),” said Kirby. “The results show that the rocks cooled relatively slowly during the early and mid-Cenozoic — from 30 to 50 million years ago — an indication that topography in the region was undergoing erosion.”
The findings also suggest that this gradual cooling was followed by two episodes of rapid erosion, one began 30 to 25 million years ago, while other dates back to 15 to 10 million years and is continuing even today. "These results challenge the idea that the topographic relief along the margin of the plateau developed entirely in the Late Miocene, 5 to 10 million years ago," Kirby said. "The period of rapid erosion between 25 to 30 million years ago could only be sustained if the mountains were not only present but actively growing at this time."
“We are still a long way from completely understanding when and how high topography in Asia developed in response to India-Asia collision,” Kirby said
Phayul[Saturday, August 18, 2012 19:41]
DHARAMSHALA, August 18: The rise of the Tibetan plateau, called the roof of the world, began much earlier than previously understood, a new report has found out.
In a research published online in the journal Nature Geoscience, researchers have discovered that the growth of the Tibetan mountains and plateau began as early as 30 million years ago.“Our study suggests that high topography began to develop as early as 30 million years ago, and perhaps was present even earlier," Eric Kirby, associate professor of geoscience at Penn State said in a statement. It was until now believed the high mountains in eastern Tibet developed during the past 10 to 15 million years, as deep crust beneath the central Tibetan Plateau flowed to the plateau margin, thickening the Earth’s crust in this area and causing the area to rise. Using radioactive dating, Kirby and his team found that the uplift began twice as early.The study may help scientists better understand the complicated processes going on beneath the Himalayan Mountains and the Tibetan Plateau.
The Tibetan Plateau, with an average elevation of about 16,000 feet (4,900 meters), lies at the intersection of the most vigorous collision of continental plates on the planet, where the Indian continental plate rams into the Eurasian plate and dives beneath it.
The Indian tectonic plate began its collision with Asia between 55 and 50 million years ago, but “significant topographic relief existed adjacent to the Sichuan Basin prior to the Indo-Asian collision.”
Kirby and associates from around the world took samples from the hanging wall of the Yingxiu-Beichuan fault, the primary fault responsible for the 2008, Wenchuan earthquake, and used a variety of dating methods including the decay rate of uranium and thorium, helium in the minerals apatite and zircon, to tease out the ages of the rocks, which tells when they formed and gives clues to when they lifted.
They also used the fission track dating, an analysis of tracks or trails left by decaying uranium in minerals in apatite and zircon. “These methods allow us to investigate the thermal regime from about 250 degrees Celsius (482 degrees Fahrenheit) to about 60 degrees (140 degrees Fahrenheit),” said Kirby. “The results show that the rocks cooled relatively slowly during the early and mid-Cenozoic — from 30 to 50 million years ago — an indication that topography in the region was undergoing erosion.”
The findings also suggest that this gradual cooling was followed by two episodes of rapid erosion, one began 30 to 25 million years ago, while other dates back to 15 to 10 million years and is continuing even today. "These results challenge the idea that the topographic relief along the margin of the plateau developed entirely in the Late Miocene, 5 to 10 million years ago," Kirby said. "The period of rapid erosion between 25 to 30 million years ago could only be sustained if the mountains were not only present but actively growing at this time."
“We are still a long way from completely understanding when and how high topography in Asia developed in response to India-Asia collision,” Kirby said
