DEPENDING ON HOW they are classified and counted, there are between six and thirty-six major plates recognized as wrapping themselves around the entirety of our planet. The edges of these plates are where the geological business of the world is most dramatically conducted. Where plates of the same kind collide with each other head-on, their edges hitting each other, mountain ranges rise up. Where they pull away from each other in midocean, volcanic islands ooze slow-moving lava streams onto the seafloor. Where plates of different kinds smash into each other, and one plate rides up over the other, as if in some kind of bizarre traffic accident, violently explosive volcanoes and other frightening manifestations of the earth’s power are thrown up. And where plates slide alongside each other, like ships passing too closely in the night, there are other kinds of mayhem and havoc on display—not the least being violent earthquakes, of the kind most frequently experienced in California.
The biggest of the plates have suitably big names—the African Plate, the Eurasian (by far the largest of all), the Antarctic. There is the Pacific Plate, for example, the only large plate that does not sport a continent. Lesser plates have more romantic, less familiar appellations: the Caroline Plate, for example, the Cocos, the Nazca, the Gorda, and the Juan de Fuca. And new plates are still being identified and classified, as more observations lead to an ever-greater understanding of the complexity of the earth’s crust. Recently, for example, there has been the christening of the Resurrection Plate, a few thousand square miles of real estate that lies mostly below the sea, tucked up against the southern coast of Alaska and itself bounded by a pair of hitherto unfamiliar lesser plates known, exotically, as the Kula and the Farallon.
These last three small plates nudge up against the western edge of one truly enormous neighbor: the North American Plate. And it was across this immense tectonic entity that I decided in 2004 to make a journey. I decided that to better understand what had happened in San Francisco a century ago, and to place it all in its appropriate geological and historical context, I would get myself there by driving. I would drive my car from where I live on the Atlantic Coast all the way to this once benighted city on the Pacific and, in doing so, traverse the breadth of the plate, one of the largest and most complex and bewildering tectonic entities on the planet.*
My journey would take me from one side of it to the other, driving from east to west. If everything went according to plan, I would eventually end up, after three or four thousand miles of driving and, with luck, a far better comprehension of the undersurface of North America, on the distant West Coast and at the very place—that ragged but essentially die-straight line—where the North American Plate’s western boundary rubs up against and slides along, quite literally, the eastern boundary of the adjoining Pacific Plate. I would eventually reach the place, in other words, where all this rubbing and sliding, which has been going on for the better part of the last 15 million years, produces great and often terrible earthquakes, of which the events of April 1906 in San Francisco remain the best known.
It seemed a simple plan. But then I looked more closely at such maps as exist displaying the plate boundaries and came face-to-face with a small geographical snag—a snag that caused some not inconsiderable complications, just as I was planning the trip.
THE PLATE ENTIRE
Not one of the major tectonic plates exactly overlies the continent or the ocean from which it derives its name. The African Plate, to take a good example, spills out all over the place, extending some hundreds of miles beyond the boundaries of continental Africa itself. It surges out to the west of the continent and into the Atlantic Ocean, incorporating as it does so the Azores and the Canary Islands, and such British colonies as St. Helena, Tristan da Cunha, and Ascension Island. At its eastern margin it embraces Diego Garcia, Mauritius, and Socotra; and to the north it stretches into the Greek Islands and the southern coast of Turkey—ecumenical in its politics, but hardly confined to the Africa that is merely carried along on the plate’s ample middle.
Such indistinct boundaries are a feature of all the big plates, with the North American Plate being probably the most geographically undisciplined of all. It runs in the east from Iceland clear across the American continent to the Russian peninsula of Kamchatka. Sixteen million square miles, depending on how the less certain edges of the plate are drawn, are incorporated within this immense storehouse of geology. A journey across it, from precise edge to precise edge, would in theory take me all the way from somewhere near Reykjavík in the freezing North Atlantic to the muskeg and larch forests near Magadan in the Russian Far East.
And something else became readily apparent as I trawled my way through the staggering amassment of papers and journals and tomes that chronicle the newest developments in the astonishingly fast-moving world of modern geology. Much of the new science—most of the new discoveries and new realizations that have turned geology so comprehensively on its head in the last two decades or so—have been made by examining the rocks and their structures that lie to the east of the shores of modern North America. It would be idle to say that other rocks in other places have not brought forth devastating revelations, too. But, as it happens, the central story of what has taken place in the world—and, by extension, the central story of what has taken place in California, what is taking place there now, and what may well take place there in the near future—is one that has largely been derived from discoveries made by geologists and geophysicists and theorists not in the American West or anywhere else, but off the American East Coast.
The discoveries that have been made, the theories that have been born, the fieldwork that has confirmed them—all originated, for the most part, in the rocks and the rock structures that unroll between the Appalachian Mountains and the Highlands of Scotland. The New Geology provides a picture of the way the world works, and answers, in one splendid moment, all the questions that can be distilled into the perfectly simple: Why San Francisco? And the New Geology—it is worth the capitals, so different is it from the geology of Lyell and Murchison and Smith and all its gray-bearded founders—that begins it all itself, began 2,000 miles east of the eastern American coastline, and 6,000 miles from the western American coastline and San Francisco, in the middle of the 40,000 square miles of fire and snow and black, black North Atlantic rock known as Iceland.
THE EASTERN FRONT
Iceland is still a center of creation, the place where the North American Plate is being born. It is known, and has been known since the late 1960s, that Iceland sits astride—indeed, is created by—a ridge, where material from the mantle wells up and spills out between two plates that are moving apart from each other, under the influence of the almighty convection currents that drive the earth’s outer engine. It is in Iceland that one can see—as I did, back in the mid-1960s—the thick lava, the raw material of the inner planet, belching up from deep within the earth. It piles itself up and helps to shift the already-west-moving North American Plate ever westward; and, as it continues to well up, it squeezes and compresses parts of the plate to such a degree that earthquakes, among a whole host of other phenomena, are triggered.
This is why Iceland, which lies so far from California as to appear quite irrelevant to the geological goings-on in the state (and most certainly it must appear so to most Californians, for when did a surfer at Malibu or a vintner in Sonoma or a camper on Mount Diablo last contemplate his or her connection to the Vatnajökull icecap?), is not, in fact, irrelevant at all. It is a crucial first part of the jigsaw puzzle, important to visit, essential to understand.
I first went there in 1965 as a student, as a climber (of modest ability only), and notionally, since I was a member of the Oxford University Explorers’ Club, on an expedition. We went up into the lava fields and onto the icecaps, and saw spread out before us a landscape quite unlike any other in the world—a place where (though no one knew it then) the planet is being steadily and spectacularly reborn.
Essential to my plan for crossing the North Ameri
can Plate was that in due course I would reach the place where it met its western neighbor, the Pacific Plate. Once I got there, I would in all probability want to place one foot on each of the two plates, as a tourist trophy—much as one likes to have snapshots taken with a foot on each side of the equator (one of them thus experiencing summer, the other technically winter), or to capture the moment of being briefly astride the Greenwich meridian, or (while at sea) the international date line. And then, as I looked through the field notes I had kept from that long-ago trip to Iceland, something similar occurred to me. Even though we had no idea that an entity called the North American Plate even existed (a measure of how new plate tectonic theory is), was there any chance, I wondered, that during that expedition I had managed to stand on the place where that plate met its eastern neighbor, the Eurasian Plate? Had I done so, it would have given my intended American trip a pleasing sense of symmetry, if nothing else.
So, briefly excited, I examined my old notes even more closely. I reread our expedition report; I pored over our yellowed maps. And yes, I thought after a while, there was indeed one place in Iceland, one place to which at the time I had attached little importance, where I might in fact have done that very thing.
My search for that place on the eastern edge began with the reddest of red herrings. Shortly before we went off to Iceland, a brand-new island had been formed, amid much fanfare from the world’s press, off the country’s southwestern coast. The locals named the island Surtsey, after the Nordic fire god Surtur; and since we were there, and curious, and ostensibly interested in a new topography, we found ourselves a small fishing smack and an intrepid young skipper, and went off to have a look. The sea was the color of iron and heaving; the weather was foul, and Surtsey lay twenty miles off the coast. Eventually we reached it—a gray, smoking hulk of fresh lava, by then a good 300 feet high and perhaps half a mile across. There was a dusting of green against the gray, as the first plants had already been established (notably a cluster of something called sea rocket); the first animal had arrived (a housefly, not easily visible from the deck of a rolling smack); and the first of the innumerable seabirds that would stop there, at what for them was a newly convenient resting place, were wheeling down from the clouds—herring gulls, kittiwakes, fulmars, and (from the sound of their chattering growl) murres were clustered happily on the craggy shore.
From the look of the contour lines on the adjoining islands and on the main island itself, and from the son et lumière of all this fresh volcanic activity, it seemed to us very much as though it was somewhere around this point that the Mid-Atlantic Ridge was welling up from the mantle below, with the coast that lay to the west of where Surtsey rose technically American tectonic real estate, and the cliffs and hills that stretched away to the east—toward the Faeroes, Shetlands, Scotland, and France—European territory.
But today’s scientific literature says otherwise. True, if an imaginary line is drawn from Surtsey northeastward to Heimaey and the other Westmannaeyjar Islands (which have to be evacuated with dismaying frequency because of their very active volcanoes, the last time being in 1973), and extended farther northward through the peak of Iceland’s most infamously dangerous volcano, Hekla (whose eruption in 1783 caused terribly cold winters all over northern Europe), it does look beguilingly like a ridgeline.
But geophysicists who are currently monitoring the line—and few places in the world are as closely monitored as Iceland (which is hardly surprising, given that it marks a place where the planet is tearing itself open)—are doubtful. Surtsey is very interesting, of course; but, though the region often behaves in a quite spectacular way and so is noticed by the outside world (as with the birth of the island, for instance, which was greeted with the enthusiasm usually reserved for pandas or heirs to royal thrones), it appears from close examination that nothing much is going on there other than that a plume of superhot material is welling up from within the earth and spilling out along this fissure track.
Most important, the sides of this fissure are not moving away from each other—they are not spreading as they would be if this were the point of the plate junction. At least, the movement is nothing like the one that is occurring sixty miles east of this line, sixty miles closer to the capital city of Reykjavík. It is there that geophysicists now believe a spreading ridge exists—and most specifically at a place to which I had been that sixties summer. I had visited it not because of any great interest in its topography but because it was where Iceland’s ancient parliament had first met more than a thousand years before.
The parliament was called the Althing, and it sat for many years, from the tenth century until the thirteenth; then Iceland entered into a treaty with Norway and for a while lost its independence. The Althing met in a natural rocky amphitheater northeast of where the present capital lies, at an old town called Thingvellir that is a shrine to all Icelandic people. The structure can be reached by traveling—as I had done—a road that runs along the western edge of a lake called Thingvallavatn. It now turns out that this road, which passes through a canyon cut through cliffs of layered basaltic rock, follows exactly the spreading center of the ridge. For the canyon is cut not by a river but by a series of faults, caused by the two sides of the canyon pulling away from each other, with the valley floor between dropping down because its supports have been stolen from it.
The cliffs on the east of the canyon are in Europe; those on the west are American. They are pulling apart at a rate of about one-tenth of an inch every year; and the floor between the cliffs—where the roadway runs today and where I drove back in 1965—is dropping at about the same rate.
This, then, is the true eastern edge of the North American Plate, and I had indeed stood there forty years before, perhaps with a foot on both it and on its Eurasian Plate neighbor, even though I didn’t know it at the time. I was pleasantly intrigued when I realized that one of the world’s first structures made to house the fledgling idea that later evolved into a form of rudimentary democracy had been sited, centuries ago, at the very edge of one of the world’s most crucially important geological pivot points. Synchronicities between geology and expressions of humans’ physical achievements are legion, of course—roads and railways run along valleys, cities tend to be built at river crossings or by estuaries, national boundaries follow mountain chains. But few are the coincidences, so far as I know, between the underpinnings of the earth and the foundation of ideas; and I found it elegant and satisfying to imagine Iceland as a place where this seems to be true. Not least, perhaps, because of its reciprocal: that a wealth of ideas of quite another kind is being produced at the other end of the same plate, in California. Tectonic plates may have more of an effect on those who inhabit their livelier parts than anyone cares to notice.
FROM SURTSEY we had to head west, first across the Denmark Strait to Greenland and then on down to Newfoundland. As we did so, the rocks that composed the landscape became steadily older, and the real character of the plate started, in spectacular fashion, to assert its identity and personality.
Not that this aging of the rocks was dramatically apparent at first. Our icebreaker rammed its way slowly, steadily, and very noisily across the strait, punching leads in the floes for three full days before finally emerging below the curtain wall of tall and embrasured black cliffs with which the East Greenland coast is fortified. We knew a fair amount about these cliffs, and the nunataks, the black mountains that speared through the ice cap behind. We knew they were basalt, the same fine-grained frozen lava that made up the canyon walls that rose beside Thingvellir, and we knew that they were older, though in the geological scheme of things only marginally so. Those back at Surtsey were brand-new—rocks of the entirely modern Holocene Epoch, which we had seen being fashioned before our eyes. Those in the cliffs above the Althing, on the other hand, were a little older—the simple fact of their solid existence being proof of that—by a few million years (comparing the amount of the decay products of rubidium and strontium and other
once-radioactive-marker elements would easily give an accurate figure). And the rocks here in Greenland were older still—perhaps 30 million years old, maybe a little more. They were nowhere near as old as rocks in the island’s center—but these were buried beneath miles of ice and for now were barely visible. The East Greenland basalts merely hinted at the age of things to come.
But the East Greenland basalts interested us for another reason, when we first went there in the mid-sixties. Back then no one could be certain that the continents were spreading apart—and only a scattering of well-connected scientists had any idea of the existence of such entities as tectonic plates—but there was, nonetheless, a widespread feeling that the continents might not always have been where they were today. At the beginning of the century Alfred Wegener had said that a phenomenon he called continental drift had occurred, and that what we think of as a solid earth was not solid at all. These ideas, though they were for decades derided by many in the scientific establishment, were in later postwar years tempting some believers to look for evidence that might prove that Wegener was right—the continents had moved. The apparent “fit” across the Atlantic—the bulge of Brazil looking as though it might fit handily into the bight of West Africa, for example—was proving impossible to ignore. And so student expeditions galore were being sent out from sixties Britain around the world, often organized for reasons of biological or anthropological inquiry that had nothing, ostensibly, to do with the possibilities of continental movement; the expedition leaders, however, were taken aside before setting sail and politely asked if they would mind keeping a weather eye open for any compelling evidence, for any jigsaw puzzle pieces that looked as if they might fit.