Erosion has a point -- and an edge, NYU researchers findNovember 12, 2012
Erosion caused by flowing water does not only smooth out objects, but can also form distinct shapes with sharp points and edges, a team of New York University researchers has found. Their findings, which appear in the latest edition of the journal the Proceedings of the National Academy of Sciences (PNAS), reveal the unexpected ways that erosion can affect landscapes and artificial materials.
The impact of erosion is widely recognized by environmentalists and geologists, but less clear is how nature's elements, notably water and air, work to shape land, rocks, and artificial structures, often resulting in unusual formations.
"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. In it, the researchers submerged clay--shaped as balls or cylinders--into a 15-ft. long water tunnel. The apparatus was designed to continuously generate a uniform flow of water, which would allow the researchers to observe how erosion shapes an entire object.
What they found was water flow acts as a shearing force--not unlike a nail file--against objects, working them into specific shapes. Starting from a clay ball, the flowing water sheared the sides away, producing a cone with a pointed face. Likewise, the clay cylinder was sculpted into a triangular shape. The researchers then sought to confirm these findings by replicating the experiment using a computer model. These results were consistent with the experimental findings, revealing in a computer simulation 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."
The research was supported by grants from the U.S. Department of Energy (DE-FG02-88ER25053) and the National Science Foundation (DMS-1103876, MRI-0821520).
New York University
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Related Erosion Reading:
Erosion: Changing Earth's Surface (Amazing Science)
by Robin Koontz (Author), Matthew Harrad (Illustrator)
Did you know that rain, waves, wind, snow, and ice can change the shape of Earth’s surface? They can create valleys, sea stacks, caves, and rock arches. Learn about the natural forces of erosion and how they shape the land. View Details
Weathering and Erosion (Science Readers: Content and Literacy)
by Torrey Maloof (Author)
The Earth's surface is always changing. Learn how weathering and erosion constantly reshapes the earth through wind, water, and more! Even people can drastically change the earth's surface. With the help of easy-to-read text and bright, colorful images, this reader simplifies challenging scientific topics while keeping students engaged from cover to cover. This reader also includes instructions for an engaging science activity where students can see what happens when land erodes. A helpful glossary and index are also included for additional support. View Details
Cracking Up: A Story About Erosion (Science Works)
by Jacqui Bailey (Author), Matthew Lilly (Illustrator)
Describes the process of erosion and how water, ice, wind, and sun wear away at Earth's surface. View Details
Erosion (Reading Essentials in Science)
by Virginia Castleman (Author)
Earth is changing every day as a result of erosion, and weather plays a major part. View Details
Erosion and Weathering (Rocks: The Hard Facts)
by Willa Dee (Author)
Discusses the different causes of erosion and weathering, how these phenomena create problems for people, and their role in the rock cycle. View Details
Erosion (Let's Explore Science)
by Shirley Duke (Author)
Examines the different forces of erosion, such as wind, waves, acid rain, and glaciers and explains how those forces affect the topography of the earth. View Details
Soil Erosion and How to Prevent It (Everybody Digs Soil)
by Natalie Hyde (Author)
Looks at the processes of weathering, erosion, and deposition, and how they affect plant and animal life. View Details
Dirt: The Erosion of Civilizations
by David R. Montgomery (Author)
Dirt, soil, call it what you want—it's everywhere we go. It is the root of our existence, supporting our feet, our farms, our cities. This fascinating yet disquieting book finds, however, that we are running out of dirt, and it's no laughing matter. An engaging natural and cultural history of soil that sweeps from ancient civilizations to modern times, Dirt: The Erosion of Civilizations explores the compelling idea that we are—and have long been—using up Earth's soil. Once bare of protective vegetation and exposed to wind and rain, cultivated soils erode bit by bit, slowly enough... View Details
Erosion (Princeton Series of Contemporary Poets)
by Jorie Graham (Author)
. . . . How clean
the mind is,
holy grave. It is this girl
della Francesca, unbuttoning
her blue dress,
her mantle of weather,
to go into
labor. Come, we can go in.
It is before
the birth of god. No-one
has risen yet
to the museums, to the assembly
and wings to the open air
market. This is
what the living do: go in.
It's a long... View Details
Erosion: How Land Forms, How It Changes (Exploring Science: Earth Science)
by Darlene R. Stille (Author), Farhana Hossain (Illustrator)
Describes the process of erosion, including how the power of wind, water, and glaciers have changed the Earth's surface. Includes information on fossils. View Details