by Ned Kahn
Shape the sand by spinning the globe. On land or under water, sand dunes and ripples form when small bumps make the wind or water passing by undulate, carving hills and valleys into the sand. If you spin the globe quickly for about ten seconds, and then stop it suddenly, you'll see ripples form and march slowly around the bottom edge of the globe. Desert sand dunes also "walk" in this way, pushed by wind instead of water.
Exhibits || CompLexicon || Timeline
(c) The Exploratorium, 1996