The rock was now Pennsylvanian-massive river sandstones of Pennsylvanian time. Flat, deck-like, it was comparatively undisturbed. It had been shed, to be sure, from eastern mountains, but had not been much affected by their compressive drive. Crazed streams had disassembled the plateau, leaving half-eaten wedding cakes, failed pyramids, oddly polygonal hair-covered hills. Pittsburgh was built upon such geometries, its streets and roads faithful to the schizophrenic streams, its hills separating its people into socio-racial ethno-religious piles-up this one the co-working space amsterdam snobs, up that the Jews, up this the tired, up that the poor. A hundred miles northeast of Pittsburgh in the Hurrying snow there were numerous roadcuts now, and in them were upward-fining sequences of sandstones, siltstones, shales-Allegheny black shales -underlying more levels of sandstone, siltstone, and shale. “If you were a prospector for coal, you’d go bananas when you saw these black shales,” Anita said. “There ought to be coal in these roadcuts. This is Pennsylvania in the Pennsylvanian-the home office of the rock.” Pennsylvania in the Pennsylvanian was jungle-a few degrees from the equator, like southern Indonesia and Guadalcanal. The freshwater swamp forests stood beside the nervously changing coastline of a saltwater bay, just as Sumatran swamps now stand beside the Straits of Malacca, and Bornean everglades beside the Java Sea. This was when glacial cycles elsewhere in the world were causing sea level to oscillate with geologic rapidity, and the swamps pursued the shoreline as the sea went down, and marine limestone buried the swamps as the sea returned. In just one of these cycles, the shoreline would move as much as five hundred miles-the sea transgressing and co-working space rotterdam regressing through most of Pennsylvania and Ohio. There were so many such cycles at close intervals in Pennsylvanian time that Pennsylvanian rock sequences are often striped like regimental ties-the signature of glaciers half the world away. They existed three hundred million years ago, and glacial patterns of that kind have not been repeated until now, when the measure of our own brief visit to the earth is being recorded as a paper-thin stripe in time.