Not until the 1840s had scientists realized that much of the world was once covered by continental glaciers, and not until after the Civil War had the line of furthest advance into Pennsylvania been systematically mapped.In a 1980 publication by the state's geological survey I came across an updated version of that line the ice front actually stretched from the unfrozen Atlantic to the unfrozen Pacific.I had returned to Potter County fully expecting the triple divide to provide the basis for concluding my vignettes.Although the divide was indeed a feature of the landscape that we could comfortably explore on a day trip, what grabbed my attention turned out to be something whose dimensions were much more extensive.
To our right the land quickly dropped away, into the valley for Pine Creek, which joins the West Branch of the Susquehanna at Jersey Shore, Pennsylvania.
At first I tried keeping the idea of the ancient ice front strictly localized.
In the absence of obvious direct evidence, I imagined the line being marked with metal plaques, like the furthest advance of an army across a Civil War battlefield. Maybe our experience was more like a beach trip, so that Terry and I had walked along the former "shore" of an elevated "ocean" of ice at its moment of "high tide." At the time of the region's first European-American settlements, the existence of this vast ocean of ice had been completely unknown.
But with Denny's image in mind I realized we hadn't just parked in a different watershed.
For the first time in our Genesee travels we had moved beyond the influence of the ice.