The last glacier receded 10,000 years ago, leaving large boulders and other glacial debris behind. This site stands on a drumlin left by that glacier, a hill of sediment formed by retreating ice. Sinkholes and underground streams lie 10-200 feet below ground and can be found throughout Woodbury, including in this park. This type of terrain is called karst. Glaciers moved rocks 10,000 years ago, and farmers cleared rocks from their land 175 years ago.