Geologists on a mission to vindicate their theory of a lost mountain range discover something even more significant buried beneath the ice. An excerpt from A Wilder Time: Notes from a Geologist at the Edge of the Greenland Ice.
The Quest for the Collision Zone: An Arctic Expedition
The Quest for the Collision Zone: An Arctic Expedition
William E. Glassley | Excerpt adapted from A Wilder Time: Notes from a Geologist at the Edge of the Greenland Ice | Bellevue Literary Press | February 2018| 18 minutes (4,848 words)
* * *
Erosion always wins.
The vanished mountains we envisioned were simple possibilities, tentative interpretations of passages written subtly in the obtuse patterns and features of Greenland’s rocks.
The patterns match those seen in the Alps and the Himalayas — zones that seemed to be huge thrust faults, folds of immense proportion, metamorphism at extreme conditions. Through the inspired power of analogy, my colleagues Kai Sørensen, John Korstgård, their coworkers, and those who had come before them had surmised that the Greenland landscape was an old ancestor, a forerunner of the young mountain systems that today so dramatically exalt Earth’s skin. But the Greenland ancestors are long gone, erased by the incessant hunger of flowing water, blowing wind, and grinding ice to achieve a form of topographic equality between sea and land. Erosion always wins.
The first clear hint of those lost mountains had come years earlier. Just after World War II, the Geological Survey of Greenland (GGU) was founded in Denmark. Through its offices, a small group of geologists, including Arne Noe-Nygaard and Hans Ramberg, began the first systematic study of the west coast of Greenland, sailing along the complex coastline in motorized sailing vessels strengthened to resist collisions with ice. They found a two-hundred-mile-wide belt of rock that seemed to preserve evidence of multiple complex episodes of protracted and intense deformation. Cutting through this region were several distinct zones, each zone a few miles to tens of miles wide, in which the rocks were steeply inclined and consistently aligned in the same direction.
For some years, the significance of the zones of aligned rocks remained obscure, their tectonic significance unknown. But by the late 1960s and early 1970s it had been suggested by Arthur Escher and Juan Watterson, among others, that these zones contained rocks that had been severely sheared into steeply inclined parallel sheets and layers. The individual zones were eventually called shear zones.
* * *
New story lines emerge.
Geology is not generally considered an enterprise rich with drama. Rocks stolidly await inspection, slowly providing, through insightful consideration, a glacially paced story of incremental change. But there are occasions when perspectives are radically altered, new story lines emerge, and the field is caught by surprise.
In 1987, such a change shook the world of Greenland geology. Although it played out subtly, the consequences for all involved were profound. Feiko Kalsbeek, Bob Pidgeon, and Paul Taylor reported finding along the northern limits of the mobile belt, near the inland ice, remnants of the same type of rocks as those found today in the Andes and the Sierra Nevada range in California. Although nearly 2,000 million years older, those rocks were evidence that what is happening in the Andes today had happened in Greenland.
In the case of the Andes, the continent of South America moves west, riding over the floor of the Pacific Ocean and pushing it hundreds of miles below the surface. Plunging into the incandescent heat of Earth’s interior, generating massively destructive earthquakes, the ocean floor partially melts, giving rise to bodies of molten rock that slowly make their way back to the surface. The volcanoes of the Andes and the mountainous spine they decorate are the result of that process. If the analogy was accurate, somewhere hidden within Greenland’s Nagssugtoqidian mobile belt there should be evidence of a vanished Pacific, but no evidence of such a thing had yet been found.
Kalsbeek and his coworkers acknowledged the enigma, and suggested the ocean may have been swallowed in the collision of two small continents. Such a concept had the power to explain the significance of the mobile belt and the major fault zones in it — the structures reflected the massive deformation expected as a result of two continents colliding head-on. But the evidence for where the actual collision zone might have been was very sparse — there was no good way to identify where the rocks from the old southern continent ended and the rocks of the northern continent began. Compounding the uncertainty was the underlying debate of whether plate tectonics even functioned that long ago.
The areas where John and Kai and their colleagues had worked were central to answering those questions.
* * *
An expedition for their own vindication.
The evidence John and Kai had developed suggested that the collision zone, which would have required exactly the same kind of massive movement and deformation they described, might be within the areas they had worked. Those who study the history of Earth are few, and the areas involved are vast. Knowledge is sparse. Given the immensity of the terrains the continents cover, those dedicated to unraveling the story of evolving landscapes devote their lives to finding the nuance and subtlety held within a specific setting. Some spend their lives immersed in the history of the Alpine system, climbing and hiking through those beautiful mountains. Some are owned by the Himalayas, or by the vast openness of the Canadian shield. For John, Kai, and me, it is Greenland.
Inevitably, commitment to place becomes personal — our identity is affected by the time we spend walking the fragment of Earth that has captivated us. The chosen place permeates being — terrain embeds itself under fingernails, tangles in hair, makes skin bleed and scars the heart and mind. Every thought, conscious and not, becomes riddled by knowledge derived through wandering there; remembered vistas from that world unexpectedly insinuate themselves at random times and in unanticipated ways, forcing an acceptance of a link between what we experienced there and what is lived in the moment here. We are composed of where we have been and what we have seen. John and Kai were part of a pioneering generation that helped refine Greenland’s history. They and their colleagues described in detail the characteristics that defined the “mobile” part of that land — the folds and sheared layers, the discontinuities and disrupted features. Over the years, they mapped major tectonic elements, documenting evidence for miles of displacement along several of the shear zones.
They published respected papers in scientific journals, and were recognized authorities because of their work. They knew that land better than anyone. But in the late 1990s their reputation as field geologists and scientists was challenged by a paper that said, in essence, the work they had done was deeply flawed.
The paper asserted that Kai and John, among others, had made basic and fundamental mistakes reading the rocks. The new publication stated that the NSSZ showed very little evidence of significant movement. It said that in a collective misinterpretation an essentially trivial feature had mistakenly been given major tectonic significance. The words “shear zone” were removed from maps in the paper and replaced with “straight belt.”
Science is a messy business; everything we know is, at best, a simplification of what is real and is therefore inherently flawed. As a consequence, everything we do ultimately requires corrections, implying that nothing published is completely right. It is every scientist’s expectation that whatever he or she publishes will be improved upon by others, who will provide more nuanced and detailed observations that address questions about the world. Indeed, it is an honor to be a building block in an ongoing refinement of the story of how a landscape has evolved. But in the case of the paper I was reading, it was difficult to escape the fact that Kai and John’s work had been summarily dismissed.
About halfway through reading the paper, I stopped to ask them if they agreed with what it was saying, that they had been wrong about how they had interpreted the geology.
“Of course not!” was the answer. At first, they spoke with disciplined calm. But quickly, with increasing emotion, they signaled numerous inconsistencies and errors in the paper, fundamental mistakes and misinterpretations that exceeded what the paper itself had, inaccurately, called to task. But only those intimately familiar with the real rocks would ever know.
Consequently, as things stood in the international scientific world, the work Kai and John had published was implicitly worthless and could be seen as one more example, among thousands, of failed scientific ideas. When I had finished reading the paper and began discussing with Kai and John the scientific conundrum we were in, I realized the devastation and angst they must have felt.
Being the rigorous scientists they were, they framed the argument for our little expedition as a data-gathering effort to resolve the conflict. At the time they invited me, they had said the purpose of the expedition was to pursue unanswered questions. There was no doubt that was, in fact, the underlying justification for the work. But I also realized this was, in part, an expedition for their own vindication.
* * *
Our own manufactured carnival.
Even though the sun blazed in a deep blue sky, the air temperature was close to freezing. Kai and I sat in the bow, huddled against the wind as the Zodiac sped down Arfersiorfik Fjord. I pulled the hood of my anorak over my head and put on gloves. Water splayed off to the sides in fragments of refracted sunlight, decorating the mirrorlike water surface. The outboard roared. John had the throttle wide open. We were headed for the northern boundary of the Nordre Strømfjord shear zone, which had been approximately mapped many years ago. Very little detailed work had been done there, mainly because it was so remote and difficult to get to. On our maps, the edge of the zone was confidently drawn in black ink, but we knew that no one had actually been there.
We sought that tectonic landmark as a reference point, a location where the fabric and grain of the rock could be seen and felt. We were searching for something that could be quantified and analyzed, something that would establish metrics for later measurements and comparisons. In order to be able to recognize severely, as opposed to minimally, sheared rock, we needed a baseline.
The three of us gazed down the fjord as we flew across the translucent water. Despite the roar of the outboard, we were enthralled by the beauty of the place — the hills rolling gently to the sea, the flower-chocked rivulets cascading down the bedrock, the stillness of the scenery. With some effort, we tried to focus our attention on the rock wall to our south, with its extensive exposure of folded and sheared gneisses.
Unexpectedly, as we watched the steep walls of the southern fjord edge, something shifted far to the west, down the fjord and miles away. I turned my head to get a better look, but at first all I felt was confusion. Initially, I thought the distorted landscape I was seeing was due to my eyes watering in the cold wind, but after rubbing them I realized something extraordinary was dancing along the horizon.
The land on the north side of the fjord was broad and rolling. Soft ridges sloped down to the water in a subtle cascade of rocky knolls and tundra pockets. It was a landscape that invited daydreaming. In the early-morning sun, the scene looked almost pastoral.
But farther down the fjord, a thick horizontal blade of sharp turquoise blue cut across the land, as though a giant painter had saturated a brush and slashed the ground with it. The blue was brilliant and intense, a pure distillation of color. It seemed to stretch hundreds of feet into the air and was painted across the land for miles. Within that absolutely horizontal turquoise stripe floated vertical columns of white, gray, tan, and green, looking for all the world like skyscrapers in a city miles away — a shimmering blue Oz resting on the frigid waters of the fjord. Toward the north and east, the blue trailed out into a needle-thin line that vanished at a piercing point sharper than the edge of a razor blade, ending in the middle of the rolling hills.
We all saw it. As we cruised, we watched immense rock masses from the rolling land split off and drift into the blue blade, becoming the skyscrapers that floated in the air. The size of the masses was staggering, seemingly miles wide and hundreds of feet high. As they drifted slowly out into the fjord, they changed form, shifting from angular columns to smoothed elongations filled with textures and patterns, never resolving into a constant shape, and then slowly vanished — evaporating as though consisting of nothing more than mist. Eventually, the effect was too stupefying. John throttled down the motor, the bow dropped, the roar of the engine stopped, and we drifted with the tide.
We sat silently for minutes, watching the fata morgana while the Zodiac slowly turned and drifted in the gentle current.
A nearby island only a few hundred yards away subtly entered the scene. The knob was a small rocky knoll, covered with mosses, shrubs, and lichen. On our maps, it was an ink dot so tiny, it wouldn’t be noticed unless one were looking for it. As our line of sight shifted to the point where the small island came between us and the mirage, regret began to well up at the thought of losing that magnificent show.
Without preamble, and with extraordinary understatement, the distant blue line slowly sliced across the small island. The effect played out with such surgical precision that the inconsistencies between expectations and experience took a moment to register. Emphatically, right in front of us, the little island was divided into an upper and lower half, sandwiching a thin brilliant turquoise layer.
I struggled to accept what my eyes were seeing. The implication was obvious and inescapable: What had seemed so immense and distant, miles down the fjord, was little more than a pencil-thin, trivial mirage barely an arm’s reach away, hovering in the air like a butterfly before my nose, somewhere between our little rubber boat and the small rocky knob of an island.
In that moment, what we knew to be true because we had seen it in the company of others, suddenly became unequivocally false, for all of us. But we did not have the luxury of time to resolve the contradiction. A distant destination waited, offering an opportunity to collect desperately needed data, and the afternoon winds would surely come up, making it difficult to get back to camp. Without discussion, John started the outboard and we continued on.
As our vantage point changed and we rounded the little island, the mirage returned, immense, awe-inspiring, silent. It stayed with us for ten minutes more, then slowly melted away into the thin air.
Cold dense air, chilled by the frigid fjord water, had refracted light, bending it into a vision. Light is a malleable thing, warped and distorted by well-known effects, conditioned by a broad range of circumstances. What we are able to sense, which is less than one billionth of a billionth of the electromagnetic spectrum, is affected by the sensitivities of the organs our bodies use to detect it, and the narrow range of physical conditions within which we wander. Despite the richness and beauty of the things we can perceive, we remain profoundly impoverished by the limitations of our genetically constrained bodies and the space through which they move. What we see of the world is our own manufactured carnival — the mysterious unknown within which that carnival resides beckons through mirages, silences, and misunderstood truths, forever beyond our grasp.
* * *
We were historians, trying to read ancient texts written in a language we barely knew.
The question of what had happened within the Nordre Strømfjord shear zone nearly two billion years ago danced through every waking moment. Was there a place, somewhere along the ground we walked, that was the first point of contact where continents had collided? What would be the sign? Or was the vision of entangled landmasses a flawed story, a misinterpretation of history? Regardless, how did the shear zones fit either tale? The trip to the northern edge of the shear zone had added more observations and hard data but lacked sufficient context to inspire imagining.
For relief from the wondering, we would occasionally take a short stroll together around the hillocks and along the beaches near camp. These were casual and slow hikes, a chance to talk and look at things in an unhurried way. Anything we found could easily be revisited, so we took with us only hammers and hand lenses and notebooks, the minimum equipment necessary to descend below the surface if that seemed necessary.
One particular day, not long after setting up camp, we headed west along the shoreline in the late afternoon. There was a mile of land we had not seen, and we thought this would be a good way to familiarize ourselves with details and patterns.
Almost immediately, John discovered a spectacular example of what we came to call “pencil gneiss.” The rock was the same type of igneous rock that had inspired Kalsbeek and his coworkers to propose the idea of a collision zone, or “suture,” between continents, but there, where John stood, the delicate textures that form in slowly cooling magmatic bodies had been smeared into pencil-like forms, stretched and elongated. Individual crystals that normally were equant and half an inch in size had been strung out like taut pieces of string into thin lines several feet long, each precisely parallel to all those around it — a metaphorical pencil in the gneiss. That was graphic proof of extreme shearing. We took pictures, made notes, and placed another imagined factual stake in the ground. The immediate question now became whether or not such features were throughout the shear zone, or simply local and thus not of regional significance. We walked on, amazed, wondering what would be around the next headland.
A few hundred yards farther along the shore, we came upon a bizarre little cliff face. Hazy, dark lines patterned the surface, looking much like a pile of slightly deflated and sagging soccer balls stacked one upon another. We pored over every inch of the outcrop, struggling to piece together a picture of what we could not quite make sense of. We debated options and argued, running through every idea we could dredge from our experiences. What repeatedly came to mind was a jumble of tears, caught in the instant they were shed, as though Earth had wept from some unseen eye.
Grudgingly, we agreed the most likely answer was that we were looking at a deformed slice, perhaps 150 feet long and 50 feet wide, of a type of volcanic rock called pillow basalt, which forms when lava erupts under the oceans. Unlike the rocks surrounding them, which preserved evidence of complex histories with multiple episodes of folding and shearing, the pillow basalts had a very simple history: They had erupted onto the floor of some ancient sea and then been metamorphosed and simply folded once. That slice of rock was a lens encased in the much more intensely deformed shear zone gneisses and schists. The contrast with the surrounding rocks was dramatically obvious.
If that interpretation were true, the implications were staggering. Ocean basins the size of the Mediterranean or Atlantic commonly separate continents. If the continents are approaching each other, the ocean floor between them is consumed along the boundary that will eventually become the collision zone when the continents run into each other. Such collisions grind on for tens of millions of years, slowly exuding sheared, twisted, and recrystallized rock that had once been the sediments and volcanic pillow basalts of the seabed. It is from such “root” zones that Alpine-like mountain systems emerge. If that folded pile of pillow basalts we had just found was, indeed, all that was left of some long-vanished ocean basin, we had found the suture. That thin remnant slice was all that remained of what once had been a sea probably thousands of miles wide. Could it possibly be that we had stumbled upon the long-sought ocean that, fifteen years earlier, Kalsbeek and his colleagues had postulated might have existed there?
The excitement over that discovery was tempered by a healthy skepticism. Each of us had the experience of interpreting a fact or observation as evidence for some grandiose concept, only to see it crushed under the weight of more data and observations. We held little confidence that one outcrop would be the cornerstone piece of evidence supporting the ocean-floor idea, but neither did we dismiss it as meaningless.
Several days later, along the same trend and a mile west, we came upon another small slice of rock that showed exactly the same simple history preserved in the pillow basalts. It was a different rock type, though, called peridotite. Peridotites are the source rocks from which basaltic lavas are generated, and the rock type we were seeing was precisely what geologists associate with lavas erupted on the ocean floor.
Although it was seeming to be more likely that we had stumbled upon the true collision zone, two outcroppings of rocks are insufficient evidence to allow much certainty for such an imaginative leap. The history of a mountain system is a long story, told in many chapters. An outcrop is, at best, a paragraph in a chapter. We were historians, trying to read ancient texts written in a language we barely knew. But something was being revealed that had not been seen before. There had been tremendous deformation and movement within this zone, part of it involving the consumption of an entire ocean basin. It now seemed, between the pencil gneisses and these two new outcrops, that John and Kai would be vindicated.
The satisfaction Kai and John felt was obvious but muted. They remained thoughtful in how they analyzed everything we observed, but the edge was off. We found many more examples of the pencil gneisses along the trace of where the shear zone should be, providing irrefutable proof that intense deformation was distributed all along it. But the two slices of what might be ocean floor within the same belt of rocks made the story much more complex.
The data we had collected were increasingly supporting the notion that the region preserved a record of intense deformation, as John and Kai and others had originally argued. The pencil gneisses John had first found in that one outcrop near camp and which were irrefutable evidence of extraordinary shearing at high temperatures, turned out to be a common feature for miles along the shear zone. Thin lenses of pillow basalts and ultramafics, too, were likely proof that hundreds or thousands of miles of ancient ocean floor had been dismembered and sliced, a process requiring staggering amounts of displacement and deformation. And all this was localized within the shear zone.
* * *
I feel as though I am in the presence of unencumbered, spontaneous artistry.
We round several small points of land and cross small embayments, looking for outcrops with enough exposure to let us prowl through their history. We are moving through a world barely touched by science; only the vaguest idea exists of what might be here.
Then, fifty yards away and across a small bay, we spy bare rock running from the water’s edge to an eroding cover of tundra about one hundred feet inland. Quickly, we land and head to the outcropping rock, intrigued and excited.
Exposed in that lithic fringe is a pattern so striking, our eyes wander back and forth over it, as we exclaim repeatedly how incredible it is. Bands of pink, white, gray, tan, and black, some no more than a fraction of an inch wide, some several feet thick, draw the eye along stretched-out, languid, folded forms, flowing as though the bedrock had once been as soft as butter. I feel as though I am in the presence of unencumbered, spontaneous artistry, a place where some creative genius has found its rhythm and manically painted from inspired passions, using fluid rock as its medium. Every step we take is a halting one, each new square foot possessing a different form or pattern of colors. We crawl on hands and knees, trying to grasp the significance and history of that place. From a scientific point of view, it is a treasure. From an aesthetic point of view, it is a masterpiece. Our quantitative world has seamlessly become enmeshed with an ethereal realm, dissolving into a Dalíesque fluidity. What we are doing no longer has boundaries; everything the mind can embrace is present here.
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.
* * *
Part of the story had been completely missed.
After our third expedition, it was unequivocal that the shear zone was a scar, slashed across the northern edge of the collision terrain as a last act, a tectonic finale in a mountain-building drama. That scar was what the early researchers had claimed it was — a zone of major movement. Kai and John’s work was correct and the region reverted to the term they had used for it years before — “shear zone” replaced the “straight belt” moniker on later editions of geological maps and in publications.
But buried in the crystalline record, frozen in the minerals of a few rocks from small, scattered localities, was evidence that these rocks had descended into earth before the collision of continents began. That part of the story had been completely missed. Uncertainty had changed in form but not magnitude — new questions now had to be addressed.
Only a handful of places around the world had histories of so-called ultrahighpressure metamorphism — metamorphism under conditions where pressures were more than 400,000 pounds per square inch, a state that is achieved in the earth only at depths beyond sixty miles. The evidence in all those other locations came from ancient subduction zones. In every instance, those subduction zones marked locations where continents had collided and were thus consistent with the history that was suggested as a possibility in our study area in Greenland.
But none of those other sites was older than 900 million years.
The singed-hair rock that we examined with microscopes and discovered was filled with garnets and olivines and spinels contained a startling history of burial at a depth of at least forty miles, an HP metamorphic environment. Up to that time, none of us had imagined that any of the rocks in this region had traveled more than fifteen miles down. We wrote reports and published papers and looked at more samples in the basement archives of Aarhus University, seeking confirmation that such rocks were not enigmatic anomalies.
For months, we examined thousands of samples that had been collected over decades by a small cohort of faculty and students working on master’s and doctoral degrees on Greenland geology. Out of all those samples, we found two that preserved evidence of the same very deep burial. The samples came from sites tens of miles farther to the west of where we had been working, but along the same belt of unusual rocks, and along the northern edge of the Nordre Strømfjord shear zone. The samples from both of those sites had identical characteristics. One sample, ironically, had been collected by Kai when he and Fleming Mengel, a student of his, had worked in the region nearly forty years before. Kai didn’t remember collecting it. The other sample came from a site near Giesecke Sø and had been studied in the late 1960s by Steen Platou, who was working on a graduate degree at the time. Those samples became the core of a small collection that proved that fragments of the region had, indeed, been pushed to extraordinary pressures, surviving a round-trip circuit to depths greater than 150 miles.
Prior to these discoveries, no direct evidence existed that such plate tectonic-driven processes occurred any further back in time than 900 million years ago. These samples pushed that age limit back to at least 2,000 million years.
Moreover, they are the oldest known record of an entire terrain on the surface of the world that had descended to such depths.
* * *
William E. Glassley is a geologist at the University of California, Davis, and an emeritus researcher at Aarhus University, Denmark, focusing on the evolution of continents and the processes that energize them. He lives in Santa Fe, New Mexico.
Excerpt from A Wilder Time: Notes from a Geologist at the Edge of the Greenland Ice. Copyright © 2018 by William E. Glassley. Published by Bellevue Literary Press: www.blpress.org. Reprinted by permission of the publisher. All rights reserved.
Editor: Dana Snitzky