The sign in front of this hill (back right) reads:
The hill in front of you, known as a kame, was formed thousands of years ago when water from melting glacial ice flowed through a large crack in the ice. Glacial melt water carried sand, gravel, and rocks, depositing them at the base of the crack to form the kame. To help picture this, imagine how sand flows through an hourglass and creates a rounded pile of sand in the bottom of the hourglass.
More geology on Michigan in Pictures.