A Crack in the Edge of the World (9 page)

The earth is much bigger than the other close-in planetary bodies like Venus and Mercury and, because of its size, it stores a lot of heat in its interior. But this cannot be radiated away into space at the same rate as heat from the smaller bodies, because of the simple realities of solid geometry: The larger a sphere, the smaller its surface area when compared with its volume. Earth has a very large volume and contains a great deal of heat within that volume—and yet its surface area is too small to radiate away all that energy heat and decay heat with the kind of efficiency and dispatch that other, smaller bodies enjoy. So the core burns; the mantle bubbles and boils and moves up and down in convection curves and plumes, just as the aforesaid soup might do on a stovetop; and the scum of cream that floats on the top, the many-miles-thick earth's crust, which bears all of the seabeds and all of the continents in the solid and broken-up plates of which it is now known to be composed, moves. It slips and slides about under the influence of those convection currents; the plates confront one another, interact with one another, jostle against one another; and a chain of consequences—some of them dramatic, some majestic, some terrifying, and all of them of singular importance for the humankind that clings to existence on top of some of the plates—is visible on all sides. The consequences of the plates' interactions with one another are what we see and feel and know: the topography of the world that rises and falls all around us.

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.

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.

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 American 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.