For a hundred and fifty miles, we had been traversing country that was free of glacial drift. Nowhere to be seen were the tills1 and erratics, the drumlins and kames left behind by Wisconsinan ice. Like a lifted hem, the line of maximum advance had been up in New York State somewhere, but now, in westernmost Pennsylvania, the glacial front had billowed south, and where Interstate So meets the eightieth meridian we co-working space amsterdam again crossed the terminal moraine. Sign of

the ice was everywhere-the alien boulders in the woods, the directional scratches on the country rock, the unsorted gravels, cobbles, and sands. The signature of glaciation is as bold as John Hancock’s and as consistently recognizable wherever ice has moved across the solid earth. In the presence of the evidence, one has no difficulty imagining the arctic ambience, the high blue-white ice lobes thickening to the north, the white surface wide as the continent and swept by uninterrupted gales, the view in sunlight blinding, relieved only co-working space leeuwarden by isolated mountain summits, ice moving around them in the way that water slides past boulders in a stream. Welcome to Ohio. A sign in the median said “s TAY AwA KE! STAY ALIVE!” Ohio is not rich in roadcuts. It is a little less poor, however, than Indiana, Illinois, Iowa, and Nebraska, and before long we were running through burrowed marine shales and walls of lithified river sand. It was rippled Carboniferous sandstone. We were still in rock of that age, but gradually and imperceptibly we had been losing altitude since we climbed the Allegheny front. The eastern rim of the plateau had been more than two thousand feet above sea level, and by now we were down to half that, as we moved farther away from the ancestral mountains and their wedge of sediment thinned. We had come into the continent’s province of supreme tectonic calm, the Stable Interior Craton, where a thin veneer of sediment lies flat upon the stolid fundament, where the geology-even by geological standards-is exceptionally slow. “This is the most conservative part of the U.S.,” Anita said. ”I’ve often thought about it. The wildest, craziest people are in the most tectonically active places.”