On the way back to Pennsylvania, we stopped at a service plaza near the Ohio line named Glacier Hills. According to a wall panel there, we were just seven miles north of the farthest advance of the glaciers during the Ice Age. It further noted that the rocks and other debris the glaciers carried along smoothed out the fields behind, and then the retreating glaciers deposited the rich soil that northern Ohio is still blessed with. So there's a pretty good reason the landscape levels out as I have always noticed.