Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Mountains have the scars to prove the conflict between tectonic plates and climate

26.05.2004


Across the world, rivers wash mountains into the sea. In the beautiful and rugged mountains of southeast Alaska, glaciers grind mountains down as fast as the earth’s colliding tectonic plates shove them up.




"Like an ice palace cheese grater, glaciers sweep and grind rocks off of mountains. No matter how fast the plate pushes the rock up, the glacier will erode it just as fast," said James A. Spotila of Blacksburg, assistant professor of geosciences at Virginia Tech. The National Science Foundation-funded research is reported in the June issue of Geology, in the article, "Long-term glacial erosion of active mountain belts: Example of the Chugach-St. Elias Range, Alaska," by Spotila; Jamie Buscher of Los Angeles, a Ph.D. candidate in geosciences at Virginia Tech; Andrew Meigs of Oregon State University, and Peter Reiners of Yale.

The research team collected and dated rocks from the rugged, dangerous Chugach and St Elias mountain ranges in southeast Alaska, where a bend in the tectonic plate boundary results in collision of a plate fragment. This fragment, the Yakutat microplate, is sandwiched between the colliding Pacific and North American plates, which move closer together by about 5 centimeters per year, producing massive earthquakes and towering mountains. This collision of tectonic plates has pushed the Chugach-St. Elias Range up faster and higher than any other mountain belt this close to the sea. The range has the greatest coastal relief on earth. Mt. St. Elias rises to a height of 18,008 feet in a distance of less than 20 miles from the sea, despite eroding and discharging one of the highest rate of sediment in the world into the ocean.


It is not faults and plates that make the Chugach-St. Elias Range unique, however. "It is that the erosion is by glaciers," Spotila said. "The tidewater glaciers of southeast Alaska, so familiar to cruise liners, form because of the northern latitude, but are so prominent because of the several meters of annual precipitation along the coast."

The combination of tectonic and climatic conditions provides a huge laboratory for the study of the impact of the earth’s surface processes on tectonics.

"In the last decade of research, there has been ground breaking recognition that processes at the surface have an effect on processes deep in the earth. The rapid removal of mass in one spot can affect where rock is going when there is mountain building and collision," Spotila said.

"We’ve seen hints of this with rivers," Spotila said, "but glaciers are more effective at erosion than rivers." If erosion by rivers can locally keep pace with tectonics under some conditions, erosion by glaciers may do so much more extensively. The impact of erosion on plate motions could thus be more widely felt during ice ages. Geoscientists describe this possibility as the "glacial buzz saw" hypothesis, a term coined in 1997 by University of Southern California researchers (Brozovic, N., Burbank, D.W., and Meigs, A.J., Climatic limits on landscape development in the northwestern Himalaya: Science, v.276.). Meigs continued his pursuit of this work in Alaska, eventually inviting Spotila to join his team.

Helicopters and floatplanes delivered the researchers throughout the range to collect rocks. The Chugach-St. Elias Range is not the most remote mountain range. It is limited in area and no spot is greater than 50-100 miles away from roads or small towns, "but storms and fog make the logistics very fluid," Spotila said. The helicopters would wait to take the scientists out at a moment’s notice. "Sometimes the research required teams -- typically, graduate students -- to remain camped out for weeks at lakes or fjords in the range," he said.

From the rocks, the researchers could determine the rate of exhumation, that is, the rate at which underlying material is pushed to the surface, and how fast it is being stripped off and deposited in the ocean.

"We know that temperature increases with depth in the earth. Different chemical systems are sensitive to temperature. By measuring the different isotopes of different minerals, we can reconstruct their cooling history," Spotila said. "Thus, we figured out how fast rocks rose to the surface. The technique we use measures the helium .produced by radioactive decay."

The researchers report that over the entire mountain range, the rate of exhumation is one to two millimeters per year, or one to two kilometers of rock per million years is pushed to the surface. "This is consistent with findings of other mountain ranges formed by tectonic collision," Spotila said.

And the affect of climate and glaciers on tectonics? "When we look at the rate of exhumation and compare it to the rate at which rock is coming in tectonically, it matches. Glaciers are keeping pace. This supports the buzz-saw hypothesis. The rock mass built into mountains by tectonics is redistributed by the action of glacial erosion," Spotila said..

A remaining mystery is a difference in time scale when rates of erosion are observed. "We see rocks rising to the surface over millions of years, but researchers who have looked at sediment in fjords over 50 and 100 years, by comparing present glacial retreat to photographs from 50 and 100 years ago, report erosion rates 50 to 100 times faster than our measurements," Spotila said. "As climates fluctuate over time, the average rate of movement is going to be lower. But we need to do more research to understand better the system of mountain building, glacial erosion, and climate change. It is possible that the erosion rate has increased."


Contact for more information:
Dr. Spotila, spotila@vt.edu or 540-231-2109. Learn more about his research at http://www.geol.vt.edu/profs/js/

Dr. Meigs, meigsa@geo.orst.edu or 541-737-1214

Susan Trulove | EurekAlert!
Further information:
http://www.geol.vt.edu/profs/js/
http://www.technews.vt.edu/

More articles from Earth Sciences:

nachricht One-third of recent global methane increase comes from tropical Africa
11.12.2019 | European Geosciences Union

nachricht The Arctic atmosphere - a gathering place for dust?
09.12.2019 | Leibniz-Institut für Troposphärenforschung e. V.

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Electronic map reveals 'rules of the road' in superconductor

Band structure map exposes iron selenide's enigmatic electronic signature

Using a clever technique that causes unruly crystals of iron selenide to snap into alignment, Rice University physicists have drawn a detailed map that reveals...

Im Focus: Developing a digital twin

University of Texas and MIT researchers create virtual UAVs that can predict vehicle health, enable autonomous decision-making

In the not too distant future, we can expect to see our skies filled with unmanned aerial vehicles (UAVs) delivering packages, maybe even people, from location...

Im Focus: The coldest reaction

With ultracold chemistry, researchers get a first look at exactly what happens during a chemical reaction

The coldest chemical reaction in the known universe took place in what appears to be a chaotic mess of lasers. The appearance deceives: Deep within that...

Im Focus: How do scars form? Fascia function as a repository of mobile scar tissue

Abnormal scarring is a serious threat resulting in non-healing chronic wounds or fibrosis. Scars form when fibroblasts, a type of cell of connective tissue, reach wounded skin and deposit plugs of extracellular matrix. Until today, the question about the exact anatomical origin of these fibroblasts has not been answered. In order to find potential ways of influencing the scarring process, the team of Dr. Yuval Rinkevich, Group Leader for Regenerative Biology at the Institute of Lung Biology and Disease at Helmholtz Zentrum München, aimed to finally find an answer. As it was already known that all scars derive from a fibroblast lineage expressing the Engrailed-1 gene - a lineage not only present in skin, but also in fascia - the researchers intentionally tried to understand whether or not fascia might be the origin of fibroblasts.

Fibroblasts kit - ready to heal wounds

Im Focus: McMaster researcher warns plastic pollution in Great Lakes growing concern to ecosystem

Research from a leading international expert on the health of the Great Lakes suggests that the growing intensity and scale of pollution from plastics poses serious risks to human health and will continue to have profound consequences on the ecosystem.

In an article published this month in the Journal of Waste Resources and Recycling, Gail Krantzberg, a professor in the Booth School of Engineering Practice...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

The Future of Work

03.12.2019 | Event News

First International Conference on Agrophotovoltaics in August 2020

15.11.2019 | Event News

Laser Symposium on Electromobility in Aachen: trends for the mobility revolution

15.11.2019 | Event News

 
Latest News

The Arctic atmosphere - a gathering place for dust?

09.12.2019 | Earth Sciences

New ultra-miniaturized scope less invasive, produces higher quality images

09.12.2019 | Information Technology

Discovery of genes involved in the biosynthesis of antidepressant

09.12.2019 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>