Annals of the former world John McPhee pp242-245
Under the carbonate valleys and quilted farm, the rock was buried from view. The beauty of the fields against steep-rising forests, the shimmer of April green, was not doing much for Anita. She was in need of a lithic fix. Her fingers tapped the wheel. She reminded me of a white-water fanatic on a meandering stretch of flat river. “No wonder I never did geology in this part of Pennsylvania,” she said again. It had been a long time between rocks. “I’d really like to go Iran someday,” she went on, desp erately. “The Zagros are another classic fold-and-thrust belt. The thing about the Zagros is that there’s no vegetation. You can see everything. They’re a hundred per cent outcrop.”
She had scarce uttered the words when the road jumped to the right and through a nameless gap and past a roadcut twenty metres high-Bald Eagle quartzite- and then more and higher roadcuts of Juniata sandstone in red laminations dipping steeply to the west. “I take it back. This is one hell of a series, let me tell you,” Anita said. More rock followed, rock in the median, rock right and left, and we ran on to scout it, to take it in whole. The road was descending now through gorges of red rockthe results of precision blasting, of instant geomorphology. Their depth increased. They shadowed the road. And in their final bend was the revealed interior of a mountain, geographically known as Big
Mountain. There had been a natural gap, but it had not been large enough, and dynamite had contributed three hundred thousand years of erosion. The entire mountain had been cut through-not just a toe or a spur. “Holy Toledo! Look at that son of a bitch!” Anita cried out. “It’s a hell of an exposure, a hell of a cut.” More than two hundred and fifty feet high and as red as wine, it proved to be the largest man-made exposure of hard rock on Interstate 80 between New York and San
Francisco. It was an accomplishment that might impress the Chinese Geological Survey. “When you’re doing geology, look for the unexpected,” Anita instructed me, forgetting the Zargos Mountains.
We stopped on the shoulder in the shadow of the rock. “Holy Toledo, look at that son of a bitch,” Anita repeated, with her head thrown back. “Mamma mia!” The bedding was aslant in long upsweeping lines, of which a few were green. Almost due south of Lock Haven and thirty-one miles west of the Susquehanna River, it was Juniata sandstone, brought down off the Taconic uplift and spread to the west by the same system of rivers that transported the rock of the Delaware Water Gap.
“This would be a beautiful place to measure the thickness of the section,” Anita said. “It’s completely exposed. It’s consistent. There are no faults. The thin green bands are where deposition was too rapid for oxidation to take place.” Evidence of geologists was everywhere. They had painted numbers and letters on the rock. They had removed countless paleomagnetic plugs. The bedding, seen close, was not monotonously ever, as rock would be that formed in still water. Instead, it was full of the migrating channels, feathery crossbedding, natural levees, and overbank deposits of its thoroughly commemorated river. There were little maroon mud flakes. They were plucked off flats in the storm.
We went back a few miles and slowly reviewed the rock. When again we approached the huge roadcut, Anita said, “In Illinois, this would be a state park.
The bedding planes of the Holy Toledo cut, as I would ever after refer to those enormous walls of red stone, where dipping to the east. Over the past few miles, the rock of the country had been folded ninety degrees. To the immediate west, therefore, we would be going down in time and

Annals of the former world John McPhee pp242-245 predictably would descend in space to a Cambro-Ordovician carbonate valley, which is what happened, as the road fell away bending left and down into Nittany Valley, where ribs of dolomite protruded here and there among rich-looking pastures turning green, gentle streamcourses, white farms. “Penn State sits on Nittany dolomite,” Anita said. “It’s twenty miles down this valley.”
Some remnant Cambrian sandstone formed a plaster in the valley. The interstate drifted around in a westerly way and toward the foot of still another endless mountain-Bald Eagle, the last ridge of the deformed Appalachians. After the Cambrian sandstone, the Ordovician dolomite, there was Silurian Quartzite in the gap that broke through the mountain. Its strata dipped steeply west.
The rock had bent again, and again we were moving upward through history. Now, though, the dip of the strata would reverse no more. In a dozen miles of ever younger rock, we climbed through the
Paleozoic era almost from beginning to end. We went up though time at least three hundred million tears and up though the country more than a thousand vertical feet, the last ten miles uphill all the way, from Bald Eagle Creek to Snow Shoe, Pennsylvania-the longest steady grade on I-80 east of
Utah-while, light, wind-driven snow began to fall.
We had come to the end of the physiographic province of the folded-and-faulted mountains, and the log ascent recapitulated Paleozoic history from the clean sands of the pre-tectonic sea to the dense twilight of the Carboniferous swamps. We came up through the debris of three cordilleras, though repetitive sandstones and paper shales-crumbling on their shelves like acid-paper books in libraries. The shales were so incompetent that they would long since have avalanched and buried the highway had they not been benched-terraced in the manner of Machu Picchu. In other roadcuts,
Catskill Delta sandstones, beet-red and competent, were sheer. We had gone through enough hard ridges and soft valleys for me not just to sense but to see the Paleozoic pageant repeatedly played in the rock. For all the great deformity and comlpleiy, the mountains now gone had left patterns behind.
The land rising and falling, the sea receding and transgressing, the ancestral rivers losing power through time had not just obliterated much of what went before but had always imposed new scenes, and while I, for one, could not hold so many hundreds of pictures well related in my mind I felt assured beyond doubt the we were moving through more than chaos. The strata at the foot of the ten-mile hill had been nearly vertical. Gradually, though the long climb, they leveled out. The leaned backward, relaxed, one degree every two million years, until in the end they were flat-at which moment the interstate left the deformed Appalachians and itself became level on the Allegheny
Plateau.

Annals of the former world John McPhee pp242-245