More than 10,000 years ago, the area that is now the park was covered by a huge glacier. Today, reminders of that ancient glacier can be seen in the high, rolling hills, the valleys partly filled with glacial soils, and the uplands with their eskers, kames and moraines -- different formations of gravel and silt that were left behind when the glacier receded. East of Antrim Lake in the park is a pre-glacial boulder field, where massive rounded rocks lie in a jumble.