How wind sculpted Earth's largest dust deposit

How wind sculpted Earth's largest dust deposit
Geoscientist Fulong Cai stands on a linear ridge on top of China's Loess Plateau and looks across a river valley at another of the plateau's linear ridges. The high hills in the far background are on the edge of the plateau, which drops about 1,300 feet (400 meters) to the Mu Us Desert to the northwest. Credit: Paul Kapp/ University of Arizona Department of Geosciences

China's Loess Plateau was formed by wind alternately depositing dust or removing dust over the last 2.6 million years, according to a new report from University of Arizona geoscientists.

The study is the first to explain how the steep-fronted formed.

Wind blew dust from what is now the Mu Us Desert into the huge pile of consolidated dust known as the Loess Plateau, said lead author Paul Kapp, a UA professor of geosciences.

Just as a leaf blower clears an area by piling leaves up along the edge, the wind did the same thing with the dust that was once in the Mu Us Desert.

"If the blower keeps blowing the leaves, they move backward and the pile of leaves gets bigger," Kapp said. "There's a boundary between the area of leaves and no leaves."

About the size of the state of Arizona, the Loess Plateau is the largest accumulation of dust on Earth. Deposits of wind-blown dust known as "loess" generally create good agricultural soil and are found in many parts of the world, including the U.S. Midwest.

The UA team also found that, just as a leaf blower moves a pile of leaves away from itself, wind scours the face of the plateau so forcefully that the plateau is slowly moving downwind.

"You have a dust-fall event and then you have a wind event that blows some of the dust away," Kapp said. "The plateau is not static. It's moving in a windward direction."

Linear ridges on the top of the Loess Plateau are also sculpted by the wind, the researchers found.

"The significance of wind erosion shaping the landscape is generally unappreciated," Kapp said. "It's more important than previously thought."

How wind sculpted Earth's largest dust deposit
This map shows the location of China's Loess Plateau in relationship to the Mu Us Desert, the Gobi Desert and the city of Beijing. Credit: Paul Kapp/ University of Arizona Department of Geosciences

The team's paper, "From dust to dust: Quaternary wind erosion of the Mu Us Desert and the Loess Plateau, China," is scheduled for publication in the September issue of the journal Geology and is currently online.

Kapp's co-authors are UA geoscientists Alex Pullen, Jon Pelletier, Joellen Russell, Paul Goodman and former UA geosciences postdoctoral researcher Fulong Cai, now at the Institute of Tibetan Plateau Research in Beijing. The National Science Foundation funded the research.

To track down the source of the Loess Plateau's dust, Kapp, Pullen and Cai went to China's deserts in 2013 during March—prime season for . The researchers hoped to experience dust storms first-hand.

While standing atop one of the plateau's linear ridges during a dust storm, the researchers noticed the wind was blowing parallel to the ridge's long axis.

Kapp said they each had the same realization at the same time: The plateau itself was being sculpted by the wind. The plateau is not just a sink for dust, but is also a source of dust.

"You have to live it for it to really sink in," he said. "You have to be out there in the field when the wind is blowing."

Once back at the UA, Kapp fired up Google Earth to see satellite images of the plateau. He saw linear ridges just a few kilometers long—ridges like the ones he'd stood on.

How wind sculpted Earth's largest dust deposit
During a windstorm on China's Loess Plateau, geoscientist Fulong Cai uses a plastic bag as a wind sock to show that the wind blows parallel to the linear ridge he and Wang Zhao are standing on. Roads in this area run along the ridges. Credit: Paul Kapp/ University of Arizona Department of Geosciences

To learn more, he started mapping the ridges in the satellite images.

"I mapped stuff like crazy, for weeks and weeks—I measured the orientation of about three thousand ridges from these images," he said.

The ridges ran northwest-southeast in the northern part of the plateau and ran more north-south in the southern part.

To compare the orientation of the ridges to the orientation of the winds, he asked Russell to make a map of the modern-day wind patterns over the Mu Us desert and the Loess Plateau.

The wind pattern map, especially the winter and spring storm winds, matched the orientation of the on top of the plateau.

"I've never seen anyone look at the wind-related geomorphology and actually relate it to climatology at the large scale of the entire Mu Us Desert and Loess Plateau," Kapp said. "It's a rare approach."

The team's ideas definitely are applicable to the formation of other areas of loess deposits on Earth, Kapp said, adding, "But nothing compares to the size of the Loess Plateau."

He continues to be fascinated by how wind shapes planets. Kapp's next step is looking at other -eroded landscapes on Earth and also on Mars.


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Journal information: Geology

Citation: How wind sculpted Earth's largest dust deposit (2015, September 1) retrieved 13 October 2019 from https://phys.org/news/2015-09-sculpted-earth-largest-deposit.html
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Sep 02, 2015
There's a question mark over the conclusion reached by the scientist. Did the wind form the plateau or is the wind directed by the plateau?
Since the earth has not been in existence for 2.6 million years one can easily come to the conclusion that the wind was not responsible for the formation as calculated by the scientist.
One look at the photo/map delivers the deep impression of a landscape formed by enormous water run-off. The only thing that comes to mind for such a gigantic water run-off is the global flood of Noah's time.
Now since the 2.6 million years is sheer speculation, it's equally valid to present an alternative viewpoint that is far more plausible than the wind story.

Sep 02, 2015
This article is a good illustration of how one's starting assumptions, i.e. one's worldview shapes the way one interprets the data [ or evidence ] at hand. Given the same evidence, two different starting points, two different conclusions.

Sep 02, 2015
Dear Fred, you are so wrong that you are *embarrassing*.
Any non-superficial look around should prove that there was no Noachian global flood. Beetles, kangaroos, polar bears etc etc. There's a zillion examples. Go look. And the Noah flood was lifted from the much more modest 'Gilgamesh' cycle which preceded it by centuries. Plagiarism, yet !!

Welcome to my 'ignore' list...

Sep 02, 2015
This article is a good illustration of how one's starting assumptions, i.e. one's worldview shapes the way one interprets the data [ or evidence ] at hand. Given the same evidence, two different starting points, two different conclusions.


Genesis is without data or evidence of any kind. Thanks for your display of ignorance and delusional thinking.

Sep 02, 2015
There's a question mark over the conclusion reached by the scientist. Did the wind form the plateau or is the wind directed by the plateau?
Since the earth has not been in existence for 2.6 million years one can easily come to the conclusion that the wind was not responsible for the formation as calculated by the scientist.
One look at the photo/map delivers the deep impression of a landscape formed by enormous water run-off. The only thing that comes to mind for such a gigantic water run-off is the global flood of Noah's time.
Now since the 2.6 million years is sheer speculation, it's equally valid to present an alternative viewpoint that is far more plausible than the wind story.


Are you having fun acting the dumbsh*t troll or are you really a dumbsh*t troll?

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