Featured Research

from universities, journals, and other organizations

Mountains are only minor contributors to erosion and climate regulation

Date:
January 7, 2013
Source:
University of Pennsylvania
Summary:
For years, geologists believed that mountains, due to their steep slopes and high rates of erosion, were large contributors to the trapping of carbon in ocean sediment. But a new study suggests that mountains do not play a significant role in this activity, turning a geological paradigm on its head.

Moraine Lake sunrise.
Credit: © james_wheeler / Fotolia

Though churning smokestacks, cud-chewing cows and gasoline-burning vehicles are contributing constantly to greenhouse gas emissions, there are also many processes that do the reverse, pulling molecules like carbon dioxide out of the atmosphere. One of these is chemical weathering, which occurs when rock turns into soil. Carbon dioxide molecules and rain combine to dissolve rock, and the weathering products, including sediment, eventually make their way through waterways to the ocean where some become trapped on the ocean bottom and in coral reefs and seashells.

For years, geologists believed that mountains, due to their steep slopes and high rates of erosion, were large contributors to this "carbon draw down" effect. But a new study led by the University of Pennsylvania's Jane Willenbring suggests that mountains do not play a significant role in this activity, turning a geological paradigm on its head.

Willenbring, an assistant professor in the Department of Earth and Environmental Science, led the research, working with Alexandru Codilean of the GFZ German Research Center for Geosciences and Brandon McElroy of the University of Wyoming.

"High mountains have been the go-to field area for people interested in studying how much sediment goes into the ocean and how tectonics perturbs global climate," Willenbring said. "But what we found was that mountains contribute only a small amount of the total sediment produced on Earth."

This finding, published in the journal Geology, directly challenges previous studies, which suggested that small mountain rivers contributed most of the sediment to the world's oceans.

What these other scientists neglected to account for, according to Willenbring, was that even the steepest, most erosion- and weathering-prone slopes take up only a tiny fraction of Earth's surface. So while these steep protrusions have very high rates of carbon absorption per unit area, they are far outstripped by the much more abundant expanses of gently sloping land.

"These small mountain streams are packing a big punch for their size," Willenbring said. "But even though they have a lot of erosion going on, the amount of the Earth covered by mountain ranges is too small to produce the amount of sediment that less steeply sloped areas produce."

The previous studies lacked access to a new investigative technique that was developed relatively recently. The method involves an examination of cosmogenic nuclides, which are rare forms of chemical elements produced only when supernovas explode, sending high-energy radiation to Earth and breaking up other atoms. Counting these chemical isotopes allows researchers to determine how long sediment has remained in a particular watershed over long time periods.

In contrast, techniques used previously, which involve physically measuring sediment flow in rivers and streams, only capture a snapshot of sediment erosion and deposition rates over a short time frame.

The researchers analyzed published data on cosmogenic nuclide concentrations from around the world to determine the levels of sediment flux over a time frame of thousands to hundreds of thousands of years. They also gathered topographical data to determine the slopes of the surrounding areas. They then extrapolated these rates of sediment deposition to the whole Earth's surface.

"What the cosmogenic nuclides tell us is that chemical weathering still happens in these low sloping areas," Willenbring said.

Other scientists had believed these gently rolling or flat areas, such as floodplains, to be "trappers" of sediment, but the research team's analysis demonstrated that, despite being areas of net deposition, they are in fact still drawing large amounts of carbon dioxide from the atmosphere.

Given these findings, geologists interested in understanding the contribution of erosion to climate fluctuations may want to spend less time on mountaintops and more time in big, lower-lying rivers like the Mississippi and the Amazon, Willenbring said.

"We're going to need to start studying 'boring' rivers if we're going to understand carbon and sediment cycling."


Story Source:

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


Journal Reference:

  1. J. K. Willenbring, A. T. Codilean, B. McElroy. Earth is (mostly) flat: Apportionment of the flux of continental sediment over millennial time scales. Geology, 2013; DOI: 10.1130/G33918.1

Cite This Page:

University of Pennsylvania. "Mountains are only minor contributors to erosion and climate regulation." ScienceDaily. ScienceDaily, 7 January 2013. <www.sciencedaily.com/releases/2013/01/130107121055.htm>.
University of Pennsylvania. (2013, January 7). Mountains are only minor contributors to erosion and climate regulation. ScienceDaily. Retrieved September 19, 2014 from www.sciencedaily.com/releases/2013/01/130107121055.htm
University of Pennsylvania. "Mountains are only minor contributors to erosion and climate regulation." ScienceDaily. www.sciencedaily.com/releases/2013/01/130107121055.htm (accessed September 19, 2014).

Share This



More Earth & Climate News

Friday, September 19, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Wildfires in CA Burn Forest Asunder

Raw: Wildfires in CA Burn Forest Asunder

AP (Sep. 18, 2014) — An out-of-control Northern California wildfire has nearly 2,800 people from their homes as it continues to grow, authorities said Thursday. Authorities said a man has been arrested on suspicion of arson for starting the fire on Saturday. (Sept. 18) Video provided by AP
Powered by NewsLook.com
Raw: Elephant Undergoes Surgery in Tbilisi Zoo

Raw: Elephant Undergoes Surgery in Tbilisi Zoo

AP (Sep. 18, 2014) — Grand the elephant has successfully undergone surgery to remove a portion of infected tusk at Tbilisi Zoo in Georgia. British veterinary surgeons used an electric drill to extract the infected piece. (Sept. 18) Video provided by AP
Powered by NewsLook.com
Raw: Scientists Examine Colossal Squid

Raw: Scientists Examine Colossal Squid

AP (Sep. 16, 2014) — Squid experts in New Zealand thawed and examined an unusual catch on Tuesday: a colossal squid. It was captured in Antarctica's remote Ross Sea in December last year and has been frozen for eight months. (Sept. 16) Video provided by AP
Powered by NewsLook.com
Man Floats for 31 Hours in Gulf Waters

Man Floats for 31 Hours in Gulf Waters

AP (Sep. 16, 2014) — A Texas man is lucky to be alive after he and three others floated for more than a day in the Gulf of Mexico when their boat sank during a fishing trip. (Sept. 16) 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