Around 1 million years ago, the first of a few glaciers moved south into what is now Ohio. Approximately 2/3 of the state was covered to their maximum extent. Glaciers scraped a lot of Ohio's surface, including its bedrock. They also left deposits of clay, sand, gravel, and rock as they melted back. During this period, humans appeared in what we now call the "Old World." At some point around the end of the Quaternary Period, groups of people migrated to the "New World," and eventually reached what would later become Ohio.
