|The Himalayas grow by about a centimeter|
The Himalayas may be more than 450 million years old - nine times older than previously estimated - according to a controversial new dating study.
The mountain range is generally thought to have arisen from the collision of India and Asia 55 million years ago. But George Gehrels, of the University of Arizona in Tucson, and his colleagues are proposing that the world's loftiest peaks may owe some of their height to an earlier continental crash.
"We've come to the conclusion that there was an older mountain range in place before the current Himalayas," says Gehrels.
Gehrels' team analysed radioactive uranium in garnet and zircon grains from Himalayan rocks to determine their age. The amount of uranium that had decayed to thorium and lead indicated that many grains are between 450 million and 500 million years old.
The granites and schists containing these garnets were formed during a collision between India and a section of what is now Asia, the researchers suggest. The rocks were forced down to great depths, where intense heat and pressure melted and changed them.
As the collision continued, the mountains grew, pushing some of the rocks back up to the surface, the team argues. Thereafter, tons of sediment eroded from the mountains and settled on their flanks. Zircon grains in some of these ancient sediments are just slightly younger than the garnets.
Sometime after the collision, the idea goes, India pulled back. Then, 55 million years ago, it plowed into Asia once more, and a similar episode of mountain-building followed. India is still moving northwards, and the Himalayas grow about a centimetre taller each year - very fast by geological standards.
"There was definitely something going on back then, but there's still no direct evidence of what that was," says Kip Hodges of the Massachusetts Institute of Technology in Cambridge, who works on the geology of the Himalayas.
Gehrels' hypothesis fits the data and is certainly plausible, but is very difficult to test, Hodges points out. Many of the faults and structures that could have formed earlier were reactivated during the most recent collision, making it hard to determine what happened when, he explains.
"They've found some interesting geological relationships," says geologist Paul Myrow of Colorado College in Colorado Springs. But Gehrels' team focused on Nepal - much more detailed work in other parts of the Himalayas is needed to piece together what really went on, he says.
Archeological Discoveries in Saudi Arabia
Tehran, Jan 4: A stone inscription in Sanskrit, recovered from the Al-Ula of Saudi Arabia a few years ago, has thrown new light on the reign of the Vedic ruler `Sanjit' in that country.
The recovery and significance of the inscription, telling a story of the Vedic ruler of Ancient India and his devotion to lord `Brahma', was told by leading epigraphist and archaeologist . Dr. Mark Beech, at the ongoing Asian History Congress here.
The inscription, with six lines written in Sanskrit of 25th century BC, had several spelling mistakes. ``As the stone is slightly broken at the top left corner, the first letter `OM' is missing'', he said.
According to the inscription, ``the ruler of Aryavrata occupied Arabia by force, It is during his reign that a temple of Brahma was built in Arabia.
The inscription was brought from , what we know Ancient Dedan, which is situatied between Al Madinah and Tabuk in central Saudi Arabia.