The Kelleys Island Glacial Grooves are large, deep grooves carved into limestone on Kelleys Island in Lake Erie. These grooves were formed during the last Ice Age, around 18,000 years ago, when massive glaciers moved across the landscape, scraping and shaping the rock beneath them. The grooves are about 400 feet long and up to 35 feet wide, making them a significant geological feature. Today, the glacial grooves are a popular attraction for visitors and are protected as part of the Kelleys Island State Park. They provide valuable insight into the geological history of the region and serve as a reminder of the powerful forces of nature that shaped the area.