27 July 2016
Posted by Callan Bentley
Here are two scenes, depicted in two photos each, that I saw on the beach at Machir Bay, Islay, last week. Compare and contrast them.
Scene #1:
Scene #2:
What stories do these pebbles tell? Answers tomorrow…
Callan Bentley is Associate Professor of Geology at Piedmont Virginia Community College in Charlottesville, Virginia. He is a Fellow of the Geological Society of America. For his work on this blog, the National Association of Geoscience Teachers recognized him with the James Shea Award. He has also won the Outstanding Faculty Award from the State Council on Higher Education in Virginia, and the Biggs Award for Excellence in Geoscience Teaching from the Geoscience Education Division of the Geological Society of America. In previous years, Callan served as a contributing editor at EARTH magazine, President of the Geological Society of Washington and President the Geo2YC division of NAGT.
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Wind erosion (first photo) versus water erosion (second photo) around the pebbles?
That would certainly be my guess. Wind predominantly from right to left in the top photos leaving sand to accumulate in the wind shadows behind the pebbles vs. the lower photos showing the results of water coming in from the left to the right as waves then receding in thinner, less energetic sheet flows from right to left leaving the characteristic dimpled asymmetric flow markings.