Online edition of India's National Newspaper
Thursday, Jan 29, 2004

About Us
Contact Us
Sci Tech Published on Thursdays

Features: Magazine | Literary Review | Life | Metro Plus | Open Page | Education Plus | Book Review | Business | SciTech | Entertainment | Young World | Property Plus | Quest | Folio |

Sci Tech

Printer Friendly Page Send this Article to a Friend

Role of climate, tectonics

The southern Himalayan flanks are eroded by monsoon rain, while the northern flanks by landslides, glaciers and narrow river channels producing nearly the same rate of erosion.



The southern flanks are eroded by rain, while the northern flanks by landslides and glaciers producing nearly the same rate of erosion.

DESPITE A vast difference in precipitation between the north and south sides of the Himalaya mountains, rates of erosion are indistinguishable across these mountains, scientists have found.

Their four-year study talks of interactions between climate, erosion and tectonic deformation. Himalayas were chosen due to their unique combination of massive topography, monsoon rains, and rapid erosion. The study relies on a network of 20 weather stations arrayed across the Himalayas.

These stations are unique in that many are located on mountain tops as high as 15,000 feet, whereas most weather stations in the world are located in valleys.

It was found by the researchers that the difference in precipitation between the north and south is striking. Monsoon rains originating over the Indian Ocean are drawn toward the Himalayas. The moisture in the monsoon storms as they rise over the mountains, is wrung out of them, drenching, in each summer, the south side of the Himalayas with 15 feet of rainfall. By contrast, the north side is a rain shadow region with summer rainfall amounting to just one foot. "Given this profound difference in rainfall, we expected to see large differences in erosion rates. But this is not what we found," said Douglas Burbank, professor of geology at the University of California, Santa Barbara. The findings were published in the journal Nature

Moreover, the tectonic plate of India is colliding with and thrusting under that of Asia at a rate of about two inches per year. The mountains are thrust upward between India and Tibet because about half of that collision is absorbed by the Himalayas. This thrusting, coupled with erosion, carries rocks to the surface from deep in the Earth's crust.

The rocks cool as they move toward the surface. Using a mineral-dating technique called fission-track dating, the team found that it took about a half a million years for Himalayan rocks to cool from about 280{+o}F to surface temperatures. This indicates that two to four miles of rock are eroded from the Himalayas every million years. Not only are these rates of erosion rapid, but also they show no significant variation from the monsoon-drenched flank of the Himalayas to the arid conditions north of the range.

It was noted that if the southern flanks are eroded by monsoon rain, the drier north is steep. This makes it more vulnerable to rapid erosion. Erosion in this case is through landslides made more pronounced even with less rainfall due to steeper slopes. There are other contributors too. Glaciers periodically advance across the northern areas and may erode very efficiently, despite the drier climate. The researchers also proposed that river channels get narrower in the drier areas, thus concentrating more energy on the bedrock and eroding it just as fast as in the wetter areas. — Our Bureau

Printer friendly page  
Send this article to Friends by E-Mail

Sci Tech

Features: Magazine | Literary Review | Life | Metro Plus | Open Page | Education Plus | Book Review | Business | SciTech | Entertainment | Young World | Property Plus | Quest | Folio |


The Hindu Group: Home | About Us | Copyright | Archives | Contacts | Subscription
Group Sites: The Hindu | Business Line | The Sportstar | Frontline | The Hindu eBooks | Home |

Comments to : thehindu@vsnl.com   Copyright 2004, The Hindu
Republication or redissemination of the contents of this screen are expressly prohibited without the written consent of The Hindu