On Looking: Eleven Walks With Expert Eyes (7 page)

BOOK: On Looking: Eleven Walks With Expert Eyes
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“Yep.”

Those rocks were schist. Manhattan schist. Well, to quote another geologist, “very massive rusty- to sometimes maroon-weathering, medium- to coarse-textured, biotite-muscovite-plagioclase-quartz-garnet-kyanite-sillimanite gneiss and, to a lesser degree, schist.”

Yikes! Here I must pause, anticipating a collective drop in reader blood pressure. One risks, in writing about geology, numbing one’s readership with the terminology. Schist, gneiss, phyllite; metamorphic, sedimentary; siliciclastic, schistosity. It can be dizzying. I sympathize. I hear “Paleozoic” and I nearly drop right into a deep sleep. Perhaps the time scale of geology (hundreds of millions of years) combined with the amount of multisyllabic jargon used (thousands of terms) has some kind of cumulative soporific effect.

Of course, this is not an exclusively geological effect. What my Paleozoic response indicates is that I am a geology naïf. It is much easier to follow the details of a topic when one knows the least bit about it. When that least-bit develops into a great pond of knowledge, one may rightly call oneself an “expert”—and have the brain to prove it. Expertise changes what you see and hear, and it even changes what you can attend to. Neuro-imagery shows us how expert and naive brains look when attending: fundamentally different. Watch the brains of dancers while they watch a dance performance, and you will see considerably more activity than you
would find in the brains of nondancers. Expertise leads to the ability to acquire more expertise.

This is why, listening to Horenstein wax eloquent about geology, I began to think about chess. In the field of cognitive psychology, there is a large amount of research on expertise: how it is acquired, retained, and applied. Since the 1970s, the preponderance of studies have scrutinized the behavior and abilities of one group: chess grandmasters. The reasons are simple. Master chess players have incredibly good memories, for one; and, helpfully, the compact, folding, packable chessboard is a tidy way to investigate the extent of those memories. And those memories are extensive: as soon as expert chess players see a game in progress, they see something quite different from what a novice chess player sees. Their eyes fixate on the board differently than the novice’s; they actually see
more
of the board in one glance. They can see not just where the pieces are but also where the pieces came from and where they are going. Often, they can see a dozen moves ahead—perhaps to checkmate—or a dozen moves behind, to the opening gambit.

Grandmasters remember phenomenal amounts of chess. It is estimated that a typical chess master remembers on the order of 50,000 to 300,000 “chunks”—arrangements of five to seven pieces placed normally, not randomly, on a board. They might know, unconsciously, 100,000 opening moves. These memory stores allow them to recall the precise positions of a large number of pieces on a series of games in progress, having seen them once. Sometimes this ability even extends to random piece placements, since a randomly placed piece is surprising, and distinctive, to someone who can see the logic in the piece placement of a game underway. By contrast, when a novice chess player looks at a board, he sees a jumbled arrangement of black and white pieces. If he is attentive, he might later be able to remember a few squares of the board, or a handful of pieces neighboring one another. Nothing else.

The difference is that the scene is
meaningful
to the chess master but not to the novice. To the expert, every piece relates to the others, and every arrangement of pieces on a board relates to previous boards the player has seen or made. They become as familiar as the faces of friends.

The comparison to faces turns out to be apt. For quite a while, neuroscientists have known that there is a brain structure, subsequently named the “fusiform face area,” which is largely responsible for our perception and recognition of faces. Humans can quickly distinguish a face in a scene, find a familiar face in a crowd, and remember uncountable faces even after very brief exposures. Indeed, infants’ perceptions are face-centered from the beginning. On our walk, my son aimed his gaze at people’s faces with a bald interest that seemed to unnerve some people. More recently, researchers have found that this same fusiform face area is also active in chess masters not only when they see faces but also when they are playing chess. Chess objects do not have any facelike features to them, so it appears that this area of the brain helps to process those visual scenes at which we have become expert “lookers.” We are all experts at seeing and recognizing faces
3
; to experts at viewing other scenes, those scenes are just like the faces of friends and family.

I glanced over at Horenstein, who was himself looking at his rock friends. For a split second I swear I could see his fusiform face area pulsing with recognition.

 • • • 

Back to the Paleozoic. I do suspect that others share my (naive) reaction to geology, which is why I spent several eye-crossing days trying to sort out, simply, what schist is. Follow me here: your brain will begin to change as you do.

Schist is metamorphic rock.
Schist
comes from a Greek word for
split
; metamorphic simply means “it changed forms”: and in these word histories lie almost the entire story. For schist, the change of form was monumental. It started as mud or clay on the ocean floor. A couple of hundred million years ago, in an era that shall remain nameless, continents collided, land split, and that mud was pressed down toward the core of the earth, squeezed and heated and squeezed some more. For a very, very long time. When it was pushed back up again, it was in a form ultimately re-christened schist. Minerals pushed into the schist give it the layered look that distinguishes it from gneiss, which is more grainy metamorphic rock.

That’s it for schist. But that’s not the end of the story for us. Schist is the bedrock of my city. Skyscrapers are built on foundations embedded in schist; indeed, for many years the story of the Manhattan skyline, famously tall downtown and Midtown, but short in the streets between, was explained by the need to drive the foundations of especially tall buildings into bedrock. Schist lies right below the surface downtown and Midtown, but is buried more deeply on the intermediate streets.
4
Here and there, schist pokes up above “ground”—the convenient name for the surface
on which we have placed roads and houses—and silently occupies an entire lot. Central Park is erratically polka-dotted with these peekabooing rocks. Olmsted and Vaux left some in place for natural color, and also moved around some slabs to make a hill from which to appreciate the newly designed view.

On this day, the schist of the city shined with the mica embedded in its layers, playing with the afternoon light as Horenstein and I gazed at it admiringly. I ran my hand across its striped surface. “That’s the glaciation,” Horenstein said. I must have looked puzzled, because he elaborated: long ago, “glaciers moved over these rocks, ground them down.” New York City was covered by glaciers—and though they retreated thousands of years ago, they have left calling cards. We owe the shape of the coastline and the height of the seas to the glaciers’ final, inglorious melting retreats. They also left us, on the schist, evidence of their passage. Glaciers move slowly and powerfully over rock, pushing along smaller rocks and rasping the surface. The striped surface I was petting was the result of the ice rasp it received. Horenstein pointed out that the stripes of the rock showed the direction of the ice’s movement, in a southeasterly (advancing) or northwesterly (retreating) way. In theory, should you find yourself lost in Central Park, you can find your way out by seeing the schist stripes as a slightly skewed compass of the park: they point you to the southeast and the safety of Midtown. Those piggybacking rocks, “erratics,” are the boulders peppered like modern art around the park and the city.

Back on the streets, we were honked at for jaywalking and nearly swiped by a bus. I felt for a moment that we had left the geology behind us, but I was quickly disabused of this notion. A few buildings in from the avenue, we reached a knee-high retaining wall in front of a row house: a short, unlovely white wall separating the sidewalk from the building’s trash storage. Horenstein stopped, to my surprise. Apart from a few bright yellow leaves
on its surface, the wall was not something to attract me: it looked filthy. Not to Horenstein: to him it looked like gold.

“Limestone. This is a limestone from Indiana. Right here, these are worm burrows.”

He fingered a long squiggle on the surface of the wall. It did look like a place a worm had been trapped. But—in the rock?

In the rock. “This rock was once loose stuff”—sediment—“on the sea floor—and you have sea worms going through it and leaving their trails.” When the rock was soft sediment, ancient marine worms burrowed through it, eating their way along. The worm-shaped traces Horenstein was pointing out were their paths, chemically changed from passing through the worm’s digestive system and fossilized after the worm moved on. On the very next building down the street, he found some of the sea worms’ old pals: “Oh, and here’s a crinoid! And that’s a bryozoan. And that’s actually a pelecypod right there.”

These were not familiar animal characters to me, but as I started to parse the variegated surface for signs of past life, Horenstein explained who we were seeing. Limestone, a popular building material, is full of the shells, remains, and other traces of ancient animals. In fact it mostly
is
these fossils and fragments. Like schist, it formed in the Geologically-Long-Ago era, on the floor of the oceans—and this ocean was where the Midwestern United States is now. The movement of ocean waters broke up the shells of the small invertebrate animals—snails, scallops, other tiny organisms. Crinoids were little creatures with stems of repeated discs, stacked like wafers. Bryozoans were sedentary animals, shaped like fans, much like coral. Pelecypods, scallopy things, left a trace of the familiar seashell-by-the-seashore.

The crinoid wafers looked like small coins with
O
s in their center, ancient subway tokens for the sea. Suddenly I saw them everywhere. The worm traces read like ancient graffiti down the
length of the building. Taking this in, my view of the street was entirely changed: no longer was it passive rock; it was a sea graveyard. I was nearly speechless.

“That’s a surprising thing to see on this retaining wall, three-hundred-million-year-old worm tracks,” I managed, as though Horenstein could make this fact logical and ordinary.

He did not attempt a response. Instead, he indicated for me to follow him. As we continued down the block, Horenstein was constantly talking. If you think of the city as geology unearthed, it is nonstop: he pointed out features of the sidewalks and streets; walls, roofs, and stairs; atriums, cornices, and decorative rosettes. All were stones; all were known to him. Just this one block, a random sample of any block in this city or any city, contained the history of geology across eras and locales. But it began to look to me like a mash-up history written by lunatics, where red granite from Missouri sat next to stone from Knoxville, Tennessee, and immigrant limestone from France rested alongside the Midwesterners, both politely quiet on the other’s accent. Between these sightings were a half dozen of the city’s famous brownstones—actually sandstone, I learned, from two hundred million years ago. Underfoot, concrete, made of heated limestone, cement, and pebbles, nudged slabs of quarried granite from Maine and bluestone from Vermont.

We stopped at the bluestone. “It’s from Proctor, Vermont,” he specified. “It shows a very interesting thing, which we never think about. You see the feathers?”

I laughed. Clearly a trick question.

Wrong. “See right here? See these lines radiating out? . . . That is where the stone mason hit the stone to split it.”

The stone has multiple stories to tell us, for it has had multiple lives. Every stone has a parent—for the limestone, it is the creatures of the sea—and even in this latest, most quiet phase
of its last hundred million years, it has seen some things. Quarries, created to pull stone out of the earth by the tonful, each have distinctive characters, and the people who know stones come to know the quarries from which they have been sourced. Different techniques of harvesting the rock, splitting the rock into workable sizes, and treating the rock result in characteristic pocks and colors. One method of splitting a rock like bluestone into manageable slabs is to use a “plug” and “feathers”—just a rod and flanking shims, which, when hit into the stone at even intervals, causes the stone to split naturally in two. The lines of the split can be seen (Horenstein called both the tool and the mark it left by the same name), and sometimes even the round hole that housed the plug is clearly visible.

The bluestone’s neighbor was a brownstone building whose first-story stone face was textured with pocks. These were the marks of the tools of the stone mason: hammers and chisels used not just to break apart the stone but to decorate it. Two blocks of stone adjacent to each other might have very different pocking, because they were done by different hands.

By the time we reached the end of the block an hour later, I was almost afraid to look around me. This vision of the city as vertical geology had made me dizzy. I could no longer see, and dismiss, a city block as simply a row of uniform buildings neatly snuggled together between avenues. Now the block and its contents appeared to me more as a jumble of geological time and place. Even a single building on West Seventy-sixth Street became a wildly anachronistic historical painting, on examination: Italian marble stood proudly aside 330-million-year-old Indiana limestone, atop 365-million-year-old bluestone from the Catskills and next to boulders of Manhattan schist, some 380 million years old and revealed by retreating glaciers only twelve thousand years ago.

Horenstein smiled in his gentle way. “There is so much to entertain you, you know.” He had bestowed on me the ability to be entertained by rocks—not a trivial gift. A street full of rocks, made buildings, becomes a whirlwind tour through eons. I now saw Horenstein, too, changed by his own expertise. He can never walk down a block and not see its geology. We all have our own chesslike expertise in our heads, the place we know impossibly well, the images with which we are intimately familiar, the fine motor skill or athletic grace we can recognize in other people. Horenstein’s brain, I thought, is full of rocks, arranged on a chessboard of his own reckoning. He shook my hand, turned away, and walked back to the museum, surrounded by his friends.

BOOK: On Looking: Eleven Walks With Expert Eyes
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