The Teays River was dissected and largely wiped away by advancing glaciers and their meltwater. These glaciers were the massive continental ice sheets that began to cover large parts of Ohio and other states downstream (west) of Ohio between 2.5 and 3 million years ago. Their presence caused lakes (Lake Tight, Lake Monongahela, etc.) to form along the Teays and associated rivers. Overflow of these lakes into nearby, lower valleys caused large floods and new rivers to form. These new rivers – formed about 2 million years ago – included the present-day Ohio and Scioto Rivers, which are associated with the most direct evidence of the Teays.