UA-Led Team Studying 'Baffling' Rock Formations

UA geoscientist Paul Kapp and his research team are studying yardangs, rock formations that have been observed in arid deserts on Earth.

In most major arid deserts in the world, rocks have been shaped into crested ridges seemingly by a form of natural sandblasting.

Called yardangs, the formations have been recognized for decades but scientists do not quite understand how they are fomred over time.

"In general, people think that wind processes cannot disintegrate and transport rock as efficiently as water or ice," said University of Arizona geoscientist Paul Kapp, who is leading a team that is studying the formation of yardangs in the Qaidam Basin, which is located in a region of China.

That's not so in all places, said Kapp, a UA associate professor in the geosciences department. "Here in the basin the material is being removed and the basin is being eroded purely by wind."

He and his colleagues have begun a project – "Wind Erosion in the Qaidam Basin: Records, Rates and Broader Implications" – which has just received new grant funding.

"There is still very little work, amazingly, dealing with how much erosion has happened and how fast the erosion occurred," Kapp said.

Kapp also said that part of the problem has been that scientists have not had the tools necessary to go into the depth of research his team intends. Of course, this makes the team's research not only advantageous, but also pioneering.

The team will travel to China next week to begin collecting and analyzing hundreds of samples of sediment in China for about six weeks.

Among other techniques, the team will use cosmogenic nuclide dating, a technique that allows scientists to determine the amount of time the rock was exposed to sunlight and the rate of erosion based on the concentration of cosmogenic nuclides, such as beryllium, in rock grains, Kapp said.

Yardangs typically form in sedimentary bedrock. The UA-run High Resolution Imaging Science Experiment camera aboard NASA's Mars Reconnaissance Orbiter has even captured images of yardangs on Mars.

As part of their research, Kapp and his UA research team expect to determine that the Qaidam Basin has experienced episodic periods of high wind erosion in the past.

The team also suspects that the basin has experienced certain processes – including wind-enhanced tectonics – that have advanced the erosion process even further. Another hypothesis is that the rate of erosion is among the fastest the Earth has experienced.

"The hypotheses raised are novel and have huge implications in fields that span tectonics, surface processes, paleoclimate and planetary geology. But data are still needed from the ground," the research team wrote in the grant proposal to the American Chemical Society, which awarded the group $100,000 to begin studying the Qaidam Basin yardangs.

Among other things, the team will try to determine historic wind patterns, what conditions existed to form the yardangs, the strength of the wind to create the formations and where the material has gone.

"What's really weird is that since documenting the weather began in this area – about the last 60 years – there has not been any major dust storm," Kapp said.

"This is puzzling. Strong winds are required to form yardangs. Perhaps the winds in this region in the past were much stronger than those observed today."

Kapp said the research findings will also have implications for those studying the warming of the plant, crops and health problems, particularly anything related to the respiratory system. "If you put a lot of dust in the air, it can serve as an insulator and wind erosion degrades the land," he said.

Members of the research team are Alexander Rohrman, a UA graduate student in geosciences, and Richard Heermance, a faculty member in the geological sciences department at California State University, Northridge.

Kapp, the principal investigator on the grant, came up with the idea to research the formations after studying a satellite image of the region of China. At the time, he noticed a series of perplexing rock formations.

The Qaidam Basin, which is home to some of the largest modern yardangs formations on Earth, also contains "paleoyardangs," which may date more than 2 million years in age – another key reason for going to China, he said.

But because the basin is drained internally, it was "baffling" that the yardangs should exist, he said, adding that he wanted to study the yardangs' erosion to help inform the geological and rock records.

Kapp emphasized the potentially broad reach of the research saying "this research is leading me into research directions outside of my current areas of expertise."