A Wilder Time Page 11

  WE DID NOT KNOW AT THE TIME that those are the oldest rocks in the region, remnants of some of the most ancient continents on Earth. It took many months of work back in our laboratories to discover that they were formed more than 3 billion, 300 million years ago. They preserved evidence of the existence of an ocean basin billions of years old, when life was only single-celled and free-floating and what little land existed was adrift with blown sand and utterly barren. It was an ocean vastly older than the one associated with the building of the mountains we had come to study. Black layers had once been molten rock, injected into the sediments of those old seas, probably long after the water had been squeezed from them and their crystalline form changed. Deeply buried, heated, and compressed, the entire sequence was later folded and refolded, deformed and intruded during some unknown mountain-building events spanning hundreds of millions of years. Eventually, sometime in the last few tens of millions of years, they had made it back to the surface, shoreline to a new ocean, supporting our boots while waiting for another transformation. It was, in fact, the northern limit of the zone we were looking for. It was the very edge of one of the continents involved in the collision.

  SINCE MAKING THAT DISCOVERY, John, Kai, and I have visited that headland several times. We are trained observers, looking with a critical eye for facts and hints that will fill in details about the big picture and the small. We want to know the linear history embodied in that complex of patterns, colors, and textures. We record and sample. We make repeated measurements. We argue and deduce. And yet, no matter how carefully we take notes, measure orientations, describe patterns, mineralogy, and textures, each visit is a new revealing. We look at an outcrop or pattern for the third or fourth time and see things we have not noted before.

  All landscapes shape a future terrain. In our moment, riding the back of those implacable forces, we are entangled in that process no less than the boulders pounding the walls of that imperious tidal channel.

  Clockwork Pebbles

  DAYS AND MILES PASS. THE THREE OF US collect fragments of information—measurements of mineral orientations, the strike of planar features, the mineralogy of layered rocks—take samples and notes, all in an attempt to augment what little is known. The naked eye, hand lens, and compass, are feeble tools, and we will need results from laboratory analyses before elements of the story can be pieced together. Even so, what we see provides first impressions, a few facts, and the beginnings of insight. And always, in the evening, we sit and talk, the conversation weaving through the complexities and joys of our private lives and the experience of the science we are pursuing.

  On this particular day, there is a vague aura of satisfaction. The shear zone is not a “straight belt,” but a zone of massive movement, one of the defining elements of convergent, ancient continents.

  I climb out of the cook tent and head toward the little beach that fringes our tundra-blanketed bench. The scramble down the small cliff that bounds our home is easy, the walk to the water’s edge spent mulling over the conversation I’m leaving behind.

  The beach is a short stretch of cobbles and pebbles and not much sand. A little ridge of rock about ten feet long runs parallel to the shore, six feet out in the water, off to my right. The tide is coming in and starting to drown the rock ridge. Ragged, choppy little waves wash up on the beach, except at that stony barrier where they spend themselves in a brief frenzy, then wash around it, carrying small pebbles with them.

  I walk over to the protected backwater behind the barrier and stand by the water’s edge, looking out across the fjord. Clouds scud by overhead, casting a gray gloom over everything. The distant shore is featureless in the dim evening light, just a dark presence on the other side of the water. Lost in thought, I stand there long enough to let the rising tide and little waves make a surprise advance on my boots, soaking them in a flurry of white water and foam. I quickly step back with a crunch of grinding stones, pushing pebbles into mounds and depressions that accidentally mark where I stood.

  That new topography is an assault on the smoothly sloping surface that the waves prefer. Within seconds, the advancing salt water attacks the raised lip of jumbled pebbles, collapsing them back into the space where I had been. As the waves work away at my inadvertent engineering, the beach slowly recovers its original form, returning to some state of quasi-equilibrium. Within minutes, there is little evidence of any human intrusion.

  It is bitingly cold. Standing there isn’t comfortable, but something about the feel of the place holds me. I pull up the collar on my parka and glance down.

  The stones that shingle the beach are fragments of gneiss and schist, weathered from the outcrops we have been studying, eroded and ground down to flattened, smooth oblongs. Most are remarkable only for their dark, gray, unidentifiable plainness.

  The pebbles extend into the fjord and beyond the tidal zone. The water, crystal clear here, makes it possible to look into the depths, where the light vanishes and the stones become progressively less distinct. There is no boundary where the pattern of pebbles ends, only growing dimness, a dissolving.

  There is one small gray flat oval of a pebble that I have been watching. Lying among the others, slightly tipped up, it has a thin edge protruding above the rest. A small wave breaks on the shore and washes across the beach, immersing it. As the wave spends itself and rushes back into the fjord with a light hiss, the little pebble flips over in the brief chaos of turbulence and foam. One wave, one pebble, and the metronome of process registers one more click.

  THE DAY WE DISCOVERED THE STONE that smelled of singed hair, we saw something I had not appreciated at the time, but the tumbling pebble resurrected the memory.

  After collecting that stone and cruising back toward camp in the late afternoon, a brilliant flash of light from the shore we sailed along caught our eyes. It was an odd reflection six feet above the high-water line, several hundred yards away.

  John swung the boat around and slowly retraced our course as we looked for the flash to repeat. When it did, we fixed the location and sailed toward it. There was no beach there, only huge angular boulders that had tumbled from the steep thirty-foot wall of rock at the fjord’s edge. As we slowly made our way along the coast to the west, John idled the outboard, eventually finding a small pocket of sand to land on.

  As he beached the Zodiac, John reminded us that the tide was rising and we had little time.

  We grabbed hammers and jumped out, tying the boat as securely as possible to several boulders. The outcrop was a good distance away, across a jumble of talus we tried to scramble over quickly. As we carefully picked our way along, we kept looking back at the Zodiac to make sure it wasn’t floating off.

  The outcrop was a dull, dark olive green. The reflection came from a perfectly flat surface, polished almost to the sheen of glass, more than a foot long and eight inches wide. As we moved our heads back and forth, changing perspective, we could see that the reflection wasn’t a single sun reflection, but was composed, instead, of several rippled parallel bands. We realized it was a single immense crystal, the reflecting face a cleavage surface that contained bands with slightly different crystal structures called “twins.” Surrounding the crystal was a white rim less than an inch thick. As we looked more carefully, it quickly became clear there were hundreds of these immense crystals, each rimmed by a white rind, each stacked like a brick in a massive pile, one upon another. Stunned and excited, we realized this was an accumulation of giant orthopyroxene crystals, something that had long been postulated to exist but had never before been seen.

  When continents first form, they evolve mainly from diverse melts that rise from the mantle. Some melts are able to penetrate any crust that exists and flow out as lava onto the growing continental surface. But other melts, as they rise from below and encounter the base of the crust, cannot penetrate because they are either too viscous or too dense. A particular kind of melt that was believed to commonly stall at the continental base, but was universally involved in t
he development of continents, is called anorthosite. Trapped at the bottom of the developing continents, the liquid slowly cools over many thousands or millions of years. In this gradual chilling process, crystals form as the magma progressively solidifies, the newly formed minerals incrementally growing and settling to the floor of the magma chamber, piling upon one another. It had been postulated that giant orthopyroxene cumulates must form during this process—giant orthpyroxene crystals had been found in anorthosites around the world—although the preserved giant orthpyroxene cumulates expected to have formed at the very bottom of the cooling magma chamber were unknown. Yet we had now found such an instance, the thin white rims being preserved anorthosite melt trapped as the huge orthopyroxenes settled onto one another.

  We tried following the cumulate to get an idea of its shape, but within a few feet it ended against an intensely sheared band of rock many feet wide. We went in the other direction and discovered the same thing. Examining in detail the sheared material, we realized it was nothing but the finely ground-up remnants of the huge crystals. The cumulate giant orthopyroxenes, which probably extended for miles when they originally formed, had been abraded down to a small lozenge a few tens of feet across. We quickly made measurements, collected a few samples, then raced back to the Zodiac. The tide was lifting it and the line would not hold much longer.

  We returned to the site twice, making observations and collecting samples sufficient to allow the significance of that small outcrop to become clear. Eventually, through many hours of laboratory work, we were able to show that the giant crystals were formed more than twenty miles down in a magma chamber at the base of an ancient, evolving continent over 2.8 billion years ago. They and the crystallized magma they had settled out of had been recycled and transformed through the grinding continental collision we were studying, becoming constituents of the new landmass.

  The simple transfer of momentum, the small bit of heat lost to the shiver of atoms, the dynamics of contrasting masses flowing past each other: The physical reality of mathematical equations is made manifest by pebbles tumbling with the tide and a small sliver of sheared cumulates. The richness inherent in nature’s simple statements fills me with awe.

  WHEN KAI, JOHN, AND I RETURN to our laboratories, we will describe much of what we have seen through equations that honor the observations and data we have collected. By doing so, we will attempt to objectively communicate the details and subtlety of the history in those rocks.

  But the quantified reality we will convey will be more than an analytical result. We will use equations to calculate, from data collected in mass spectrometers, the ages of the samples we have collected. Those equations, derived from atomic physics a century ago, become time machines that focus imagination, opening doors that let us see the pace at which our planet’s surface evolves. Other mathematical formulae allow us to compute the chemical composition of minerals, giving us insight into the chemistry of the oceans and atmosphere bathing Earth billions of years ago, and providing a glimpse of the path which led from naked stone to the human mind.

  Those same equations have shown that the universe is drenched in light that spans a hundred orders of magnitude of energy. Animal vision is constrained by the ability of organic molecules to absorb and respond to only the tiniest fraction of that spectrum. What we see isn’t even a ghost of an outline of what is out there.

  I AM NOT WHO I WAS WHEN I GOT OFF THAT PLANE at Kangerlussuaq. Certainties I held to be immutable—what the world was, what constituted reality and knowledge—are evolving as we live here.

  Separation from the clutter of culture removes the incessant challenges of having to judge, act, and react to bombarding opinions and information. There is no need to struggle with the effort to make sense of the right and wrong of anything, for in this aggressively wild space, there is no judgment, simply the act of being.

  Walking back to the cook tent to talk more with John and Kai, I am once again struck by the rugged frailty of this place. The small bluff at the edge of the fjord just a short distance from our tents is actively eroding, the small rampart of accumulating boulders at the base of the cliff the only remnants of now-vanished landscape. The places we walk in camp are becoming worn paths. A small ice field across the fjord from us has noticeably changed shape and shrunk in the weeks while we have lived here. And so it will be—any evidence of our presence in that wilderness will be erased within months of our departure, just as the small waves eliminated the punctuation of my boot prints.

  Ice

  ARFERSIORFIK FJORD RUNS FROM THE DAVIS STRAIT to the ice front, a distance of nearly a hundred miles. Arfersiorfik means “where the whales are,” or something similar, depending upon whom you talk to. One of the Greenlanders who took us into the field one year said the name came from the fact that often during the winter, the mouth of the fjord stays ice-free, giving the whales a place to breathe.

  Reaching the eastern end of the fjord can be difficult because ice calving from the face can clog the water. But this year, temperatures are warm and summer has come early. Since the eastern end of the fjord has long been a place we have wanted to explore, we decide to make the trip. Years earlier, geologists had been there, but what was mapped had been done as a quick reconnaissance. We have no details. The maps that we use imply we would find the remnant magma chambers that were the first indication of an old volcanic mountain system there. It is an obvious place for us to visit.

  Because the day is going to be long, with many stops for mapping and sampling, we have an early breakfast and quickly launch the boat. The morning is sun-drenched and calm, the water surface softly undulating with a rhythmic, shallow swell.

  Cruising along the shore, we repeatedly make landings to investigate and record. Some of the stops were planned long ago, based on gaps in our data and curiosity about what intervenes between two known locations. But many stops are spontaneous, demanded by some odd or unexpected configuration of color and pattern in an outcrop. As always, each stop exposes something new, providing small insights that embellish the geological story by infinitesimal increments. We find a place where a major thrust fault comes to the water’s edge, marking a massive zone that must have seen thousands of major earthquakes over several million years of grinding and slipping. At another site, brilliant blue tourmalines decorate thick white lenses of once-molten rock, attesting to the presence of boron and other elements from ancient ocean water trapped in crystals formed during the collision of tectonic plates. We smugly revel in our good scientific fortunes. Each new find, so far, remains consistent with the story of intense, long-grinding deformation.

  As we sail along in that quiet serenity, basking in the pleasure of small discoveries, the rolling hills and modest cliffs take on an air of fantasy, as though we are gliding by a pastoral coastline where, around the next bend, a white gabled country inn might materialize. It feels as though we are moving through a place in which even the smallest pebble or blade of grass is encased in some spellbound reality.

  As we sail around a point and look down the fjord, we are slammed back to the hard-core realty of our geological pursuits. A few miles ahead of us, a sheer rock face several hundred feet high blazes in shades of off-white and pink, a stark and startling contrast to what we have been seeing. The very top of the cliff is the dark gray country rock, native to that area, that we have become intimate with, but the rest of the face is shot through with much lighter rock engulfing the gray host in a patchwork of angular geometrical threads, fingers, and thick veins. Dark gray blocks hundreds of feet long and many tens of feet wide are trapped in the whitish pink wall, examples of classic, textbook xenoliths. We have stumbled upon the eroded top of a large intrusion of granite, something rarely observed with such complete exposure. We are looking at the upper reach of a large magma chamber.

  Each of us has seen idealized diagrams in which a magma body stopes its way upward, filling in the space that is left behind as blocks of the roof of the enclosing host rock fall away a
nd settle on the floor of the magma chamber. But this example is on a staggeringly dramatic scale. In all our careers, none of us has seen anything like this.

  John speeds up, and in minutes we land the Zodiac at the western edge of the body. The granite and the suspended geometrical blocks form exquisitely beautiful patterns—the pink intrusion is riddled with tiny, perfect pink garnets; the suspended blocks are encased in intensely black rims; light tan and black micas glisten in the granite; and veins of white and black minerals crosscut everything.

  What we are walking over is just the very upper portion of a chamber of magma that had been rising slowly through the crust just after the collision of continents. The magma had formed from rocks that had been pushed deep into the earth and heated beyond their melting point. The melt that formed had collected into a single body that slowly rose up through its host rock. As it rose, it lost heat to the cooler rocks it was passing through, eventually freezing in place. After nearly 2,000 million years of uplift and erosion, it is now exposed to the sun, providing a solid bench for our boots.