Deep Time and Ceaseless Motion

I read Basin and Range, John McPhee’s celebration of geology, during a long plane ride from Portland to Boston. I am not a morning person, but I managed to reach the airport long before the flight (and almost before dawn) to secure a “geologist’s seat”—by the window, before the wing and on the left side—all for a view of Mt. St. Helens. I was not disappointed.

Volcanoes, with their symmetry and gently parabolic slopes, are perhaps the most stunning objects of a world dominated by irregular topography. If volcanoes tower above the local landscape—as they do in the northwestern United States—the effect is even more striking. When I flew by in early March, the snow had melted at lower elevations, leaving all the surrounding hills brown. But three gleaming white volcanic peaks stood out above them—Mt. St. Helens, with its cloud of steam still rising a thousand feet into the air, Mt. Adams beside it, and the granddaddy of the Cascade volcanoes, Mt. Rainier, behind. It was the most awesome sight I have ever seen from an airplane window.

We have been poor at assimilating the great lessons that geology teaches—the earth’s ceaseless motion and immensity of time (or “deep time” as McPhee calls it), I well remember the catechism I learned in grade school: Mt. Lassen, which erupted in 1914, is the only active volcano in the United States (Alaska and Hawaii were still colonial possessions at the time). Written history recorded no eruptions, so we declared that the internal fires had been quenched irrevocably. Lassen is but one peak in the Cascade chain; St. Helens is another. Every one of those volcanoes is potentially active—Shasta, Hood, Rainier, all of them. Mt. Rainier may bury Seattle before another earthquake levels San Francisco.

Geology presents its irreducible beauty in raw appearances—and who would gainsay it. But another, perhaps deeper, beauty lies in understanding. The Cascade volcanoes extend for hundreds of miles in a linear belt. Why are they so aligned? And why do they stop in northern California? Why do volcanoes tend to come in linear arrays anyway? Until the theory of “plate tectonics” revolutionized geology by constructing a new earth, these questions had no adequate answers. But now we recognize that dense oceanic rock is pushed downward (subducted) beneath lighter continental rock when two “plates”—the large, thin “wafers” that form the earth’s upper layer—push into each other, one with oceanic rock and the other with continental rock at its margin. As oceanic rock slides into the earth below a continent, friction induces partial melting of the sinking plate and, perhaps, some of the surrounding mantle rock as well. This molten material may rise to form a chain of volcanoes on the earth’s surface right above the sinking edge of the oceanic plate.

California struck (and either consumed or removed) a ridge on the ocean floor many millions of years ago. Hence, from San Francisco to the south, oceanic rock is no longer spreading into and under America; in fact the Pacific is largely moving north along the San Andreas Fault. But a shortened ridge persists in the eastern Pacific north of San Francisco, and the oceanic rock on its eastern flank is still spreading under America, where some of it melts and rises to form the Cascade volcanoes. When I viewed the lineup—Rainier, St. Helens, and, looking out the opposite window, Mt. Hood—I could almost see the old floor of the Pacific Ocean a hundred miles below me, and I apprehended those majestic volcanoes as mere pimples, minor vents for a restless earth.

John McPhee has captured this duality—beauty in particulars and satisfaction in general understanding—in his superb, highly personal book of reflections. He recognized that plate tectonics had revolutionized geology during the last two decades and he wanted to understand how the profession (and its earth) differed from the one he studied in a college course taken before the great instauration. He knew that he could not obtain the information he sought from didactic sermons in text-books or from interviews with leading figures in academic offices. He had to go into the field with geologists, and spend months observing daily scientific life, to grasp how a scientific revolution permeates the core of practice. For God does dwell in the details, and visceral comprehension can only arise from an immersion in particulars. As a scientist, I thank McPhee for understanding this, as so few who write about us do.

Before plate tectonics, there was no discernible God at all; only the details. Traditional introductory geology courses were catalogues of names for time slots, rocks, and landscapes, and they deserved the name that generations of undergraduates bestowed upon them—rocks for jocks. Both McPhee and I started with a course like that. He gives his list of fondly remembered terms; I could supply mine. My favorite was “paternoster lakes”—the chains of connected pools that often form near the edges of glaciers and once reminded someone of beads on a rosary, hence “ourfather” lakes. The terms did provide an interesting name for my friend’s pet rabbit—Inselberg Bornhardt. Beyond that I could never see much use for them. In the hands of a poet with good slides, such a course could be inspiring; usually it was insufferably dull. No matter though; it cannot be taught anymore. (And thank goodness for that; for I am not a poet, and I now teach the successor to rocks for jocks at Harvard.)

Plate tectonics has given us a unified theory for the behavior and history of the earth as a whole. It has coordinated and brought under a single rubric such disparate phenomena as: the reason for Iceland and Hawaii, the coincidence of earthquakes and volcanoes with ridges and subduction zones, the youth of the sea floor and the greater age of continental cores, and the great Permian extinction that wiped out up to 90 percent of marine invertebrates some 225 million years ago. (Iceland and Hawaii sit above vents for molten rock rising from the earth’s interior. Ridges and subduction zones mark lines of activity where plates meet, spread apart, collide, and rub against each other. New sea floor forms at ridges, spreads out, and disappears into subduction zones on a cycle measured in tens of millions of years, while continents stand high on their plates and cannot be subducted. The great extinction coincides with the fusion of all continents into a single Pangaea.) These phenomena, and hundreds of others, are no longer isolated facts. We can now present the earth as an integrated unit. Our science—and our courses—have become exciting; geology has regained a prestige it has not enjoyed since we discovered deep time and discernible history in the early nineteenth century, and Europe’s finest scientists became geologists.

As McPhee’s book opens, he is, of all places, on the George Washington Bridge. It makes sense. The Atlantic Ocean has had an off-again-on-again history during the last half billion years. It existed at the dawn of modern life in the great Cambrian explosion nearly 600 million years ago. But it closed gradually during the next 350 million years and disappeared entirely when New York collided with Europe at the end of the Permian. But it opened again soon thereafter and, beginning as a puddle, and then a channelway, grew as the sea floor spread beneath it at the mid-Atlantic Ridge. Our modern continents carry some curious scars of the collision; for the breakup of Pangaea did not occur precisely along the lines of previous suturing. Bits of ancient Europe remain stuck to the extreme eastern border of North America (as we know from the strictly European fossils found in their rocks), while smidgens of old America grace the western coasts of Norway and Scotland.

Much of New Jersey’s geology records the stretching and splitting that reformed the Atlantic. But New Jersey is a fossil; the action is now more than a thousand miles east at the mid-Atlantic Ridge. McPhee wanted to see plate tectonics at work, so he headed west with his mentor Ken Deffeyes, professor of geology at Princeton, to the Basin and Range province of Nevada.

The Basin and Range is a vast expanse of alternating parallel chains: hills and valley, hills and valley. This topography is the superficial expression of a pulling apart of the earth beneath. The earth’s crust is being stretched in Nevada. In response, it has fractured in a series of faults running perpendicular (north-south) to the direction of stretching (east-west). At each fault, the rocks on one side fall while those on the other rise, producing an alternating series of hills and valleys.

The Cascade volcanoes exist because the East Pacific spreading zone still operates north of San Francisco. But, as I mentioned before, California overrode the same zone farther south, as the North American plate moved west, pushed by sea floor forming at the mid-Atlantic Ridge more than 4,000 miles to the east. Many theories have been advanced to explain the Basin and Range province in terms of plate tectonics, but all involve the fate of this overridden Pacific spreading zone. In one version, the entire zone was subducted beneath California and still operates under the Basin and Range, uplifting Nevada and tearing it apart. In any case, the Basin and Range topography records the early history of a potential ocean. It may be a living reminder of eastern North America’s visage just before the Atlantic puddle reappeared some 200 million years ago. McPhee went to the Basin and Range to see plate tectonics in action, and his title is a symbol of our reconstructed, restless earth.

Basin and Range is a series of disparate but organically connected chapters recording McPhee’s personal journey. Some are loosely sequential, as McPhee travels with geologists from the fossilized fracture zones of New Jersey to the active topography of Nevada. Others explore the consequences of plate tectonics in different ways—by examining the practicalities in Deffeyes’s search for silver in abandoned mine tailings, and by contrasting plate tectonics with another great reconstruction of the earth presented by James Hutton in the late eighteenth century.

Where McPhee’s style works—and it usually does—he triumphs by succinet prose, by his uncanny ability to capture the essence of a complex issue, or an arcane trade secret, in a well-turned phrase. Consider his topographic characterization of the United States: “really a quartering of a continent, a drawer in North America. Pull it out and prairie dogs would spill off one side, alligators off the other….” Or his organic metaphor for “deep time”: “With your arms spread wide…to represent all time on earth, look at one hand with its line of life. The Cambrian begins in the wrist, and the Permian extinction is at the outer end of the palm. All of the Cenozoic is in a fingerprint, and in a single stroke with a medium-grained nail file you could eradicate human history.” If geology has two great themes—deep time and ceaseless motion—consider his one-liner for the second: “If by some fiat I had to restrict all this writing to one sentence, this is the one I would choose: The summit of Mt. Everest is marine limestone.”

Where it doesn’t work, at least not for me, McPhee sometimes seems to forget a principle he himself enunciates midway through the book: history is interesting when it presents a pageant of irreversible change, less so when it cycles and recycles the same kinds of physical events, and the events themselves are neither markers of time nor determiners of subsequent states. The history of life is a pageant; the history of rocks and landforms is not, unless the scale is broad enough, and events tell a coherent story framed within theories of geological change. Dinosaurs are gone forever; if the little, lone primate Purgatorius had not survived the great Cretaceous extinction, we would not be here today. But granite is granite, whether formed in the Cambrian or yesterday. McPhee presents too much descriptive history of rocks and topography. However interesting to local aficionados, a regional sequence of repeatable events lacks the grandeur of true history.

To present a more serious objection, I think that McPhee has been beguiled by the mystique of field work. No geologist worth anything is bound to a desk or laboratory, but the charming notion that true science can only be based on unbiased observation of nature in the raw is mythology. Creative work, in geology and anywhere else, is interaction and synthesis: half-baked ideas from a barroom, rocks in the field, chains of thought from lonely walks, numbers squeezed from rocks in a laboratory, numbers from a calculator riveted to a desk, fancy equipment usually malfunctioning on expensive ships, cheap equipment in the human cranium, arguments before a roadcut.

This mythology leads to serious, but unfortunately conventional, misrepresentations of the past, a tradition that McPhee follows in the historical section of his work. (The rest of this essay is not an attack on McPhee’s fine book, but a plea to all of us for reassessing a common habit of thought.)

Ceaseless motion, one of geology’s two great themes, achieved its explanation only when the theory of plate tectonics developed during the 1960s; McPhee’s book concentrates upon this contemporary revolution. But deep time triumphed 150 years ago, and this first conceptual overhaul is best treated historically. The conventional hero for deep time is the Scottish gentleman farmer and geologist James Hutton (1726-1797); and while I do not dispute the attribution, I do challenge the usual explanation, which McPhee adopts, for Hutton’s insights.

Hutton developed a theory of the earth that had, as its correlate and prerequisite, the proposition that “time, which measures everything in our idea, and is often deficient to our schemes, is to nature endless and as nothing.” He proposed an ever-cycling “world machine” that would make the earth’s history as orderly and timeless as its celestial motion. Continental rocks are eroded and deposited in thick sequences of sediments at the bottom of oceans. Subterranean heat then fuses and consolidates the sediments to rock. The same heat expands, fractures, and uplifts the rock to new continents and the old, eroded continents become ocean basins. Land and sea change places, but the world is ever the same. The cycle starts again. God undoubtedly once made a beginning and he will ordain an end, but these are matters outside the ken of science. As geologists, we can only observe and infer the cycles; and nothing in these investigations permits us to discern any direction, any indication that the process will terminate or was ever different in the past. Thus, in the last lines of his initial presentation in 1788, Hutton penned the most famous words in the history of geology: “The result, therefore, of our present enquiry is, that we find no vestige of a beginning—no prospect of an end.” Deep time with a vengeance.

In the conventional view, Hutton achieved his insight because he reasoned objectively from data observed in the field, while his benighted opponents held fast to Moses from their pulpits or their academic desks. McPhee portrays Hutton as a field geologist, drawn to his theory of cycles inductively, after piling fact upon fact: “Wherever he had been, he had found himself drawn to riverbeds and cutbanks, ditches and borrow pits, coastal outcrops and upland cliffs…. He had become preoccupied with the operations of the earth, and he was beginning to discern a gradual and repetitive process measured out in dynamic cycles.” He labels Hutton’s concept of time as “novel and all but incomprehensible,” and tends to view his opponents as religiously motivated and devoted to the strict Mosaic chronology of a mere 6,000 years or so for the earth’s history.

Hutton did do some field work, and it did him a world of good. But his system arose as much from his culturally bound mind as from his beloved rocks. Hutton wasn’t fighting theology; he merely acknowledged a differentthe perfect clockwinder who ordained proper laws of nature when he created the universe, and then let it run without further meddling.

Hutton’s system cannot be understood until we recognize its grounding in a view of science, now repudiated and even slightly musty in Hutton’s own time: all phenomena and processes have not only an “efficient cause” (a mechanical explanation coincident with our entire sense of the word “cause”), but also a “final cause,” or purpose. The old Aristotelian notion of final cause still has its place in discussing human conduct or the adaptation of organisms (though we now view its agents as natural rather than divine). But final cause has been banned from physical science; we may not speak of the purpose of erosion or lunar motion.

Hutton was committed to the belief that all phenomena had both efficient and final causes: God wound the clock correctly and events unfolded in accordance with his preordained purpose. Hutton referred to his work as “this view of things, where ends and means are made the objects of attention.” When we treat Hutton as a modernist and discuss only the mechanical workings of his world machine, we cannot understand him. He himself stated, both in private and in the organization of both his great treatises, that the world machine had its roots in a troubling challenge to final cause.

As a farmer by trade, Hutton was obsessed by what might be called the “paradox of the soil.” Soil, as a substrate for plants, is a sine qua non of our life on earth, and God made the earth for us: “This globe of the earth is a habitable world; and on its fitness for this purpose, our sense of wisdom in its formation must depend.” Soil is a product of the erosion and decomposition of rocks. But erosion also destroys the land and will eventually carry all sediments to the sea. Would God construct a world in which the same agent that supports life must eventually destroy it by wearing away the continents? Therefore, a restorative force must exist; the sediments deposited in the sea must be raised to form new continents.

Hutton’s work was placed in the category of old-fashioned, speculative world systems by the most committed empiricist among Hutton’s immediate successors—the French catastrophist Georges Cuvier (in the section “of former systems of geology” in the famous Discours préliminaire of 1812). And who can blame him when we read the opening paragraph of Hutton’s 1788 treatise:

When we trace the parts of which this terrestrial system is composed, and when we view the general connection of those several parts, the whole presents a machine of peculiar construction [efficient cause] by which it is adapted to a certain end [final cause]. We perceive a fabric, erected in wisdom, to obtain a purpose worthy of the power that is apparent in the production of it.

In the simplistic scenario of hero=uniformitarian=empiricist vs. villain=catastrophist=theological apologist, Cuvier falls among the damned because his belief in rapid changes supposedly upheld an earth of limited antiquity, and God’s direct role in geological history. In fact, none of the great catastrophists followed Moses, and their method was more rigidly empirical than that favored by any uniformitarian. They believed what they saw in the rocks—abundant evidence of catastrophe in faulting, tilting of strata, mass extinction, and abrupt change of inferred environment. Sir Charles Lyell and the nineteenth-century uniformitarians who came after Hutton argued that missing data of a woefully imperfect geological record would supply the gradual links between events not recorded by rocks.

Moreover, Hutton’s commitment to deep time was not unique. As Roy Porter shows in his excellent introduction to William Hobbs’s The Earth Generated and Anatomized (1715), the potential eternity of the world was a major issue in the great debate on earth systems that peaked in Britain about one hundred years before Hutton wrote his treatise. Hobbs was such an obscure amateur that Porter, after painstaking research, cannot even be sure that the gentleman dismissed for dishonesty as an excise officer, and later cited in tavern brawls and domestic disturbances, is his William Hobbs. Hobbs’s previously unpublished treatise rests upon the idea, already archaic in his own time as the mechanical world view spread, that the earth is an active organism. Hobbs wrote his work primarily to argue that tides are not caused by the moon’s gravitational pull, but by the earth’s pulsating heart. In the usual Manichaean division, Hobbs should be among the anti-empirical system builders whom Hutton replaced.

Yet Hobbs, and many of the system builders, supported several of the ideas that Hutton supposedly discovered in the rocks one hundred years later. Hobbs denied that sediments were products of deposition in Noah’s flood; he shared Hutton’s belief in restorative forces, though he attributed uplift to the same pulsating heart that produced tides; he repudiated Moses and proclaimed a much older earth. He railed against armchair speculation (“verbal science” as he called it) and made many astute observations on rocks and tides. He also eschewed teleology and final causes and was, to that extent, more “modern” than Hutton (in the invalid assessment that assigns worth by anachronistic convergence upon current views). Hobbs had no influence upon science, but his work possesses enormous value both for its own charm and for its illustration of how an untutored man, working far from the literati of London, integrated his own thoughts with common perceptions of his time.

Hutton, like Hobbs, was a system builder. He cited field evidence as an important source of support, but he was no modern empiricist. I do not say this to detract from Hutton’s reputation, for there has never been a finer intellect in our profession. His treatise is primarily a brilliant methodological argument for inferring unobservable processes from their results preserved in rocks. As such, it is a true landmark and beginning—for past processes are unobservable in principle, and reconstructing the past is geology’s primary goal. But we do a disservice to Hutton and all great scientists of the past when we judge them by modern standards and pretend that good science is unfettered observation and logical inference made by minds uncluttered with prejudices of former ages.

Creative science is always a mixture of facts and ideas. Great thinkers are not those who can free their minds from cultural baggage and think or observe objectively (for such a thing is impossible), but people who use their milieu creatively rather than as a constraint—as Darwin did in translating Adam Smith’s economics into nature as the principle of natural selection, and as Hutton did in using the principle of final causes to construct a cyclical view of the world.

Such a view of science not only validates the study of history and the role of intellect—both subtly downgraded if objective observation is the source of all good science. It also puts science into culture and subverts the argument—advanced by creationists and other modern Yahoos, but sometimes unconsciously abetted by scientists—that science seeks to impose a new moral order from without.