August 13, 2009

Climate Change Causes Mountains To Downsize

A new study published on Thursday suggests climate is the main factor limiting the height of mountains across the globe, and not the upward thrust of the Earth's clashing tectonic plates, AFP reported.

Scientists said this so-called "buzzsaw" effect of glaciers forms when temperatures stay below a certain threshold, otherwise the peaks of Mount Everest and K2 might have been even higher.

David Engholm, a researcher at Aarhus University in Denmark and lead author of the study, said glaciers are very effective at destroying mountains.

He told AFP even the most active mountain ranges don't get much higher once plate tectonics have pushed them across the snowline altitude.

The new study showed that peaks are generally prevented from thrusting more than 5,000 feet above the line where snow permanently forms and it explained why none of the world's tallest mountains are found anywhere near the North or South Poles.

Engholm said it is simply because the snowline is higher at lower latitudes than at higher latitudes.

The study, published in the British journal Nature, showed that at the equator, glaciers do not accumulate before an elevation of 16,400 feet. Engholm said that in Canada and Norway, or Chile and New Zealand, by contrast, the snowline altitude is as low as 3,300 feet.

The mix of factors that determine the height of mountains have long been debated by geologists and glaciologists

All mountain ranges are created from the bottom up when the tectonic plates covering the planet smash against each other. But forces that are determined by climate destroy them from the top down.

Engholm said building glaciers could even keep pace with the most active mountains on Earth.

The study is the first to gather data on all the world's mountain ranges into a single model using mathematical simulations to confirm the old theory that massive blocks of moving ice shave off layers from mountaintops.

However, one exception is the Transantarctic Mountains, which are significantly higher than they should be according to the 5000-feet-above-the-snowline rule.

Experts suggest it is likely due to it being so cold at the South Pole that the glaciers are frozen in place and therefore do not cause erosion.

Volcanoes are another exception, since they can accumulate mass faster than glaciers can destroy them.

Researchers say that in general, the older a mountain range is, the shorter and flatter it will be.

Egholm said mountains like the Appalachians in the eastern United States become very low if given enough time.

"In Norway, mountains look almost as if they tops had been cut off because very little is left above the snow line -- that is how the term 'glacial buzzsaw' came into play," he said.


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