Hemlock Falls lies nearby, where two small streams cascade down the face of a massive sandstone cliff in the shade of tall hemlock trees, with one fall dropping about 60 feet and the other about 100 feet. The rock is Black Hand Sandstone, deposited in deltas along a great salt-water sea during the Mississippian Period about 350 million years ago. The cliffs were created later by erosion along the side of the valley of the ancient pre-glacial Groveport River. One large slump block, separated from the rock wall by weathering, may be the largest in Ohio. The area contains plants more typical of the Appalachian Plateau and rare in Richland County, and its ecosystem is typical of that found at the past edge of a glacier. Bunker Hill Road lies in a valley that was once the riverbed of the ancient pre-glacial Groveport River, which flowed westward from the ancient Appalachian Mountains far to the east, turned southward here in the Bunker Hill valley, and continued south by the present locations of Butler and Fredericktown to join the pre-glacial Teays River. The Groveport River was formed about 200 million years ago. About 150,000 years ago, the Illinoian Glacier blocked the Groveport River and a new riverbed was formed. The new river, the Clear Fork River, is designated as a national natural landmark.