Mountains may experience a growth spurt that can double their heights

June 6th, 2008 - 12:38 pm ICT by ANI  

Washington, June 6 (ANI): A new study has revealed that mountains may experience a growth spurt that can double their heights in as little as two to four million years, which is several times faster than the prevailing tectonic theory suggests.

The study was carried out by Carmala Garzione, associate professor of geology at the University of Rochester, John M. Eiler, professor of geochemistry at California Institute of Technology, and Prosenjit Ghosh, assistant professor of atmospheric and oceanic sciences at the Indian Institute of Science in Bangalore.

The traditional method of estimating mountain growth is through understanding the history of folding and faulting of the Earths upper crust.

In the new study, the geologists used recently developed techniques to measure how ancient rainfall and surface temperature altered the chemical composition of a mountains soil.

By studying sedimentary basins in the high Andes Mountains, the team could determine when and at what altitude these ancient sediments were deposited.

That record of altitude changes shows that the Andes Mountains rose slowly for tens of millions of years, but then suddenly lifted much faster between 10 and 6 million years ago.

The work of one of Garziones post-doctoral research fellows, Gregory D. Hoke, corroborates the swift-rise theory and shows that not just the mountains, but a broad region more than 350 miles wide rose to some degree with the Andes.

By dating the incisions and mapping the depth and extent of the canyons, Hoke shows that the surface uplift that occurred in the sedimentary basin where Garzione took her measurements must have happened across the entire width of the Andes Mountain range.

Garzione and her colleagues show that with the addition to their new findings, a broad range of geologic indicators, including the history of folding and faulting, erosion, volcanic eruptions, and sediment accumulation suggest a hotly debated tectonic process called delamination likely at work.

When oceanic and continental plates come together, geologists believe the continental crust buckles. On the surface, the buckling manifests itself as a rising mountain range, but beneath the crust, the buckling creates a heavy, high-density root that holds the crust down like an anchor.

The delamination theory suggests that instead of eroding slowly away, the root heats up and oozes downward like a drop of molasses until it abruptly breaks free and sinks into the hot fluid mantle.

The mountains above, suddenly free of the weight of the blob, would rush upward and, in the case of the Andes, lift from a height of less than two kilometers to about four kilometers in less than 4 million years. (ANI)

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