The park's bedrock is limestone laid down 500 million years ago as organic sediments settled to the bottom of a shallow sea that covered much of the Midwest. This limestone is entirely covered by glacial till deposited during a Pre-Illinoian glaciation about 400,000 years ago. As those glaciers were retreating, a block of ice broke off and remained embedded in the till. The ice melted, forming a kettle which became Rice Lake. 10,000 years ago the more recent Wisconsin glaciation missed Rice Lake, passing to the west of the park. Meltwater from that glacier eroded streambeds into the Kansan till.