Featured Research

from universities, journals, and other organizations

Glacial Pace Of Erosion Was Not So Slow, New Technique Shows

Date:
December 12, 2005
Source:
University of Michigan
Summary:
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.

A Flood Glacier in the Boundary Ranges of the Coast Mountains, British Columbia.
Credit: Image courtesy of University of Michigan

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.


Story Source:

The above story is based on materials provided by University of Michigan. Note: Materials may be edited for content and length.


Cite This Page:

University of Michigan. "Glacial Pace Of Erosion Was Not So Slow, New Technique Shows." ScienceDaily. ScienceDaily, 12 December 2005. <www.sciencedaily.com/releases/2005/12/051211220547.htm>.
University of Michigan. (2005, December 12). Glacial Pace Of Erosion Was Not So Slow, New Technique Shows. ScienceDaily. Retrieved August 21, 2014 from www.sciencedaily.com/releases/2005/12/051211220547.htm
University of Michigan. "Glacial Pace Of Erosion Was Not So Slow, New Technique Shows." ScienceDaily. www.sciencedaily.com/releases/2005/12/051211220547.htm (accessed August 21, 2014).

Share This




More Earth & Climate News

Thursday, August 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

California Drought Stings Honeybees, Beekeepers

California Drought Stings Honeybees, Beekeepers

AP (Aug. 21, 2014) — California's record drought is hurting honey supplies and raising prices for consumers. The lack of rainfall means fewer crops and wildflowers that provide the nectar bees need to make honey. (Aug. 21) Video provided by AP
Powered by NewsLook.com
Thousands Of Species Found In Lake Under Antarctic Ice

Thousands Of Species Found In Lake Under Antarctic Ice

Newsy (Aug. 20, 2014) — A U.S. team found nearly 4,000 species in a subglacial lake that hasn't seen sunlight in millennia, showing life can thrive even under the ice. Video provided by Newsy
Powered by NewsLook.com
Unsustainable Elephant Poaching Killed 100K In 3 Years

Unsustainable Elephant Poaching Killed 100K In 3 Years

Newsy (Aug. 20, 2014) — Poachers have killed 100,000 elephants between 2010 and 2012, as the booming ivory trade takes its toll on the animals in Africa. Video provided by Newsy
Powered by NewsLook.com
Charter Schools Alter Post-Katrina Landscape

Charter Schools Alter Post-Katrina Landscape

AP (Aug. 20, 2014) — Nine years after Hurricane Katrina, charter schools are the new reality of public education in New Orleans. The state of Louisiana took over most of the city's public schools after the killer storm in 2005. (Aug. 20) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins