Departed glaciers left the ridge of sand and gravel that made these dunes possible. Melting continental ice formed the glacial ridge, and steady winds off Lake Michigan have carried sand grains inland, laying a veneer of dunes across its top. The dune is still moving, with part of the slope advancing toward Glen Lake and capable of burying nearby trees or shrubs within a few years. Beyond the wall of sand lies a windswept plateau with small stones, occasional boulders left by ice, sparse vegetation, and sculpted dunes, while this side offers views of Glen Lake. Farther across are steep bluffs 400 feet above Lake Michigan, and the whole expanse was once only a bone in the teeth of a mile-high glacier.