Their main ingredient is beach sand. The Aral Dunes, along Platte Bay's north shore, are good examples of beach dunes. Perched dunes, on the other hand, sit high above the shore on plateaus. Glacial sands atop these surfaces supplied material for these dunes. The Sleeping Bear Dune of Indian legend is a perched dune as are the dunes at the south end of South Manitou Island.
Some dunes migrate, pushed by the wind.
Sometimes shifting sands bury trees. Then, as the dunes move on, ghost forests of dead trees are exposed, stark reminders of the dunes' passing. Not even man has escaped the influence of windblown sand. U.S. Coast Guard buildings now located in Glen Haven had to be moved from Sleeping Bear point in 1931 because migrating dunes threatened to cover them. Beach grass and sand cherry are among the first plants to grow on newly built dunes.