From: Allison Winter, ENN
Published November 13, 2012 04:45 PM

Researchers study the transformation of materials facing water erosion

One of the main reasons why the Grand Canyon looks the way it does is due to water erosion. With its deep valleys and smoothed ridges, the Grand Canyon is a prime example of how erosion can wear away at land formations and change landscapes. But according to a team of researchers at New York University, erosion caused by flowing water does not only smooth out objects, but can also form distinct shapes with sharp points and edges.


Researchers at the university studied the effects of water erosion to better understand how water and air work to shape land, rocks, and artificial structures.

"The main focus of this study was to understand how and why erosion makes these funny shapes," explained Leif Ristroph, a post-doctoral researcher at NYU's Courant Institute of Mathematical Sciences and one of the study's co-authors.

To explore these questions, the researchers designed an experiment, conducted in the Courant Institute's Applied Mathematics Laboratory, to replicate natural erosion. Here, researchers submerged clay shaped as balls and cylinders into a 15-ft. long water tunnel. The tunnel was designed to continuously generate a uniform flow of water, which would allow the researchers to observe how erosion shapes an entire object.

Researchers determined that water flow acts as a shearing force—a force that is directed parallel to a surface. As water runs against objects, the water has the power to erode (or work) them into specific shapes. For the clay ball, the flowing water sheared the sides away, producing a cone with a pointed face. Similarly, the clay cylinders morphed into triangular shapes.

The researchers further confirmed these findings by replicating the experiment using a computer model. These results were consistent with the experimental findings, revealing how the shape was maintained as the body eroded away.

"Water acts tangentially to the surface of objects and skims off material to create these unique shapes," explained Ristroph. "In a sense, it works as a sculptor to naturally mold materials into new forms."

Even though erosion is a natural process, human activities can often speed up these processes and cause severe problems such as land degradation and sedimentation in waterways. Understanding the effects erosion will help us better understand how to manage erosion in the future.

The research can be found in the latest edition of the journal the Proceedings of the National Academy of Sciences.

Read more at New York University.

Grand Canyon image via Shutterstock.

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