Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Glacial pace of erosion was not so slow, new technique shows

12.12.2005


Glaciers, rivers and shifting tectonic plates have shaped mountains over millions of years, but earth scientists have struggled to understand the relative roles of these forces and the rates at which they work.



Now, using a new technique, researchers at the University of Michigan, California Institute of Technology and Occidental College have documented how fast glaciers eroded the spectacular mountain topography of the Coast Mountains of British Columbia.

Their work is described in the Dec.9 issue of the journal Science.


U-M assistant professor of geological sciences Todd Ehlers has been working in a remote region of the Coast Mountains for the past three years, studying rates of glacial erosion and topographic change. Using a new geochemical tool developed by the Caltech researchers, he and his collaborators were able to quantify the rates and magnitude of glacial erosion across a major valley. They found that glaciers radically altered the landscape around 1.8 million years ago, about the time that Earth began to experience a number of ice ages.

The erosion rates documented in the study suggest that glaciers eroded the mountains six times faster than rivers and landslides had before glaciation began. The researchers also found that glaciers scraped at least 2 kilometers (about 1.2 miles) of rock from the mountains.

"These results are exciting," Ehlers said, "because they clearly document that glaciers are the most efficient method for sculpting the topography of the range. They also demonstrate the utility of a new geochemical tool that can be applied to study erosion in other mountain ranges."

The study relied on a technique called helium-helium thermochronometry, developed by Caltech’s Ken Farley and his former student David Shuster, now at Berkeley Geochronology Center in Berkeley, California. "It’s an unwieldy name, but it gives us a new way to study the rate at which rocks approached Earth’s surface in the past," Shuster said.

The new technique rests on three facts: one, that rocks on the surface have often come from beneath the surface; two, that the ground gets steadily warmer as depth increases; and three, that helium leaks out of a warm rock faster than a cold one. By determining how fast the helium leaked out of a rock, it’s also possible to determine how fast the rock cooled and, ultimately, how deeply it was buried, as well as when and how fast it got uncovered.

The team showed that the cooling of the rock happened very quickly and that the entire valley was carved out in about 300,000 years.

"We can say that the glacier was ripping out a huge amount of material and dumping it into the ocean," Farley said. "And rather than taking evidence from a single instant, we can for the first time see an integral of hundreds of thousands of years. So this is a new way to get at the rate at which glaciers do their work."

Why the intense erosion occurred 1.8 million years ago is not `well understood, Shuster said, "but it seems to coincide with some very interesting changes that took place in Earth’s climate system at that time."

In addition to Ehlers, Farley and Shuster, Margaret Rusmore, a geology professor at Occidental College in Los Angeles, was a coauthor on the paper. The research was supported by grants from the National Science Foundation.

Nancy Ross-Flanigan | EurekAlert!
Further information:
http://www.umich.edu

More articles from Earth Sciences:

nachricht Climate change weakens Walker circulation
20.10.2017 | MARUM - Zentrum für Marine Umweltwissenschaften an der Universität Bremen

nachricht Shallow soils promote savannas in South America
20.10.2017 | Senckenberg Forschungsinstitut und Naturmuseen

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>