<p>Various slip surfaces on the face of these dunes give the sand different colors and create artistic patterns. 
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Sand dunes with wavy patterns
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/41585865@N06">Western Arctic National Parklands</a>
CC BY 2.0
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/nps_wear/8477433759/">Patterns in Nature</a>