Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Glaciers help high-latitude mountains grow taller

16.09.2010
Glaciers can help actively growing mountains become higher by protecting them from erosion, according to a University of Arizona-led research team.

The finding is contrary to the conventional view of glaciers as powerful agents of erosion that carve deep fjords and move massive amounts of sediment down mountains. Mountains grow when movements of the Earth's crust push the rocks up.

The research is the first to show that the erosion effect of glaciers - what has been dubbed the "glacial buzzsaw" - reverses on mountains in colder climates.

The researchers were surprised, said first author Stuart N. Thomson, a research scientist in the UA department of geosciences. "We were expecting to see the buzzsaw."

The team discovered the protective effects of glaciers by studying the Andes Mountains in the southernmost region of South America, known as Patagonia.

UA co-author Peter W. Reiners said, "It's been thought that glaciers limit the height of mountain ranges worldwide."

The key is climate. Glaciers atop mountains in temperate latitudes flow downhill, scouring away the surface of the mountain. Over millennia, such erosion can reduce the height and width of a mountain range by miles.

However in very cold climates such as the Patagonian Andes, rather than scraping away the surface of the mountain, the team found that glaciers protect the mountain top and sides from erosion.

The team dubs the action of the cold-climate glaciers "glacial armoring."

"Climate, especially through glaciers, has a really big impact on how big mountains get," said Reiners, a UA professor of geosciences.

"What we're seeing is that below certain latitudes, glacial buzzsaws clearly and efficiently operate, but south of about 45 degrees, it not only doesn't work - it has the opposite effect," he said. "The glaciers actually protect the surface and allow the mountains to grow higher."

He and his colleagues anticipate that glacial armoring also occurs on cold-climate mountains very far north, such as those in Alaska.

The team's paper, "Glaciation as a destructive and constructive control on mountain building," is scheduled for publication in the Sept. 16 issue of the journal Nature. Additional co-authors are Mark T. Brandon and Nathaniel J. Wilson of Yale University in New Haven, Conn.; Jonathan H. Tomkin of the University of Illinois at Urbana-Champaign; and Cristián Vásquez of the Universidad de Chile in Santiago. The National Science Foundation and the Chilean Fondecyt funded the work.

The Andes are the textbook example of actively growing mountains that are limited in height and size by glaciers, Thomson said. The Andes are actively being pushed higher by movements of the Earth's crust. However, if the glacial buzzsaw is active, the mountains also are ground down.

"We're trying to understand how mountains are built and destroyed," Thomson said. "Why are mountains high?"

In actively growing mountains, hot rocks from deep in the Earth are being thrust up. At the same time, erosion sands away the tops and sides of the mountains, bringing those once-hot rocks closer to surface. The speed at which the rocks cool indicates how rapidly the surface material above the rocks was removed by erosion.

To figure out how fast the glaciers had scoured the Andes, Thomson and his colleagues needed to analyze rocks now exposed on the mountains. The scientists sailed up glacially-cut fjords to the foot of remote glaciers and collected soccer ball-sized rocks. The team collected rocks from latitude 38 degrees south to 56 degrees south, for a total of 146 samples.

The researchers analyzed the rocks in laboratories at the UA and at Yale University to determine what geologists call the "cooling age" of the rocks.

The cooling age tells how fast the rock was exposed by erosion.

The researchers used two independent dating methods, apatite uranium-thorium-helium and fission-track dating, to determine cooling ages.

Both methods showed the same result -- that the rocks cooled faster in the north and slower in the south. The slower the cooling, the more slowly the mountains are eroding.

Reiners said, "What corroborates this is that the mountains are higher in the south than in the north. Uplift is winning in the south, and the glacial buzzsaw is winning in the north."

The importance of climate in the formation of mountains is currently a matter of scientific debate, Thomson said. The new finding indicates that climate plays a key role.

Said Thomson: "Climate determines the size of a mountain range - whether there is a glacial buzzsaw or glacial armoring."

Contact information:
Stuart Thomson
Thomson@email.arizona.edu
Languages spoken: English, German
http://www.geo.arizona.edu/~thomson/
Peter Reiners
520-626-2236
reiners@email.arizona.edu
http://www.geo.arizona.edu/~reiners/
Media contact:
Mari N. Jensen
520-626-9635
mnjensen@email.arizona.edu

Mari N. Jensen | University of Arizona
Further information:
http://www.geo.arizona.edu/~reiners/
http://www.geo.arizona.edu/~thomson/
http://www.arizona.edu

Further reports about: Andes Mountains Climate change cold climate glaciers hot rocks mountain range

More articles from Earth Sciences:

nachricht Global study of world's beaches shows threat to protected areas
19.07.2018 | NASA/Goddard Space Flight Center

nachricht NSF-supported researchers to present new results on hurricanes and other extreme events
19.07.2018 | National Science Foundation

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Future electronic components to be printed like newspapers

A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.

The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes

20.07.2018 | Power and Electrical Engineering

Reversing cause and effect is no trouble for quantum computers

20.07.2018 | Information Technology

Princeton-UPenn research team finds physics treasure hidden in a wallpaper pattern

20.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>