While the specific mechanisms shaping these bends remain uncertain, previous models suggest a relationship between fluid flow and channel topography. In rivers, centrifugal force drives water to move more swiftly along the outer bends while slowing along the inner edges. This process erodes the outer banks and deposits sediment on the inner banks, progressively intensifying the river's curvature.
Conversely, channels formed by lava or ice are shaped through thermal erosion, lacking sediment deposition. As a result, only the outer bends experience significant change, leading to smaller, less pronounced curves compared to river channels.
"This distinction sets up a great natural experiment for us to see if the shape, or size, of bends in rivers is distinct from those in volcanic or ice channels," explained Tim Goudge, assistant professor at the Jackson School's Department of Earth and Planetary Sciences and a co-author of the study.
The study, published in *Geology*, suggests that this differentiation could serve as a tool for identifying the origins of sinuous channels on extraterrestrial bodies. Scientists studying planetary surfaces often lack the ability to directly measure or sample channels, making remote diagnostic techniques valuable.
Lead researcher Juan Vazquez, a 2024 graduate of the Jackson School, analyzed thousands of river and ice channels on Earth, as well as volcanic channels on the Moon. Initially mistaking an anomaly in the data for an error, he soon realized that river bends exhibited a more exaggerated curvature than other channels.
"It wasn't until the parameters for the code we had set for the volcanic channels on the Moon kept failing for the rivers on Earth that we realized, 'Oh, that's not a fault of the code. It's an intrinsically different amplitude,'" said Vazquez.
Further analysis revealed that volcanic and ice channels tend to exhibit a greater frequency of downstream-skewed bends in comparison to rivers.
On Earth, geologists can determine the origin of a channel by examining fluid presence or identifying geological markers left by past flows. However, on distant planetary bodies like Titan-where ethane and methane streams carve channels through water ice-scientists struggle to determine whether such formations result from sediment transport or thermal erosion. A similar challenge exists on Mars, where both ancient rivers and volcanic activity shaped the landscape billions of years ago.
"There are these sinuous channels on the sides of Martian volcanos. Some people have interpreted them as volcanic channels, and some people have interpreted them as rivers that formed when maybe snowpack on the top of the volcano melted," Goudge said. "We're saying that because volcanic channel bends are so distinct, you can measure those channels to find out."
However, Goudge cautioned that while the study provides valuable insight, it should not be used as an absolute classification system. Individual channels can vary significantly, and further research is needed to refine the method.
"But I think it has the potential to be if we understand it more," he added.
Doctoral student Mariel Nelson of the Jackson School contributed to the study as a co-author.
Research Report:Upstream bend skewing in alluvial meandering rivers is distinct compared to other sinuous channels on the Moon and Earth
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