A Crack in the Edge of the World Page 9
The world became steadily more complicated as time wore on. There were two further coalescences about 500 million years later on, when the continents now known as Baltica and Atlantica emerged, also then in the Northern Hemisphere. Baltica held much of what is now northern Europe as far south as today’s Ukraine. Atlantica, on the other hand, encompassed what is today’s West Africa, Congo, Guyana, Brazil, and the region around the river Plate, all landmasses that would eventually shift south of the equator.
The world was now possessed of four continents—or five, if Kenorland is counted—Ur, Arctica, Baltica, and Atlantica, which sound as if they come from the title of a short story by Borges. It seems that these bodies, all of them massive, cool, and quite stable platforms, probably represent the totality of continental material that would be on the fledgling earth for a very long while.
And, having been fully made, these bodies then began a complex dance—a dance that, in the phrase of some fascinated geophysicists who are brave enough to mix metaphors, seems an accordion-like process, in which continents clang into one another, sometimes joining up, then separating, most colliding and separating once again for the remainder of their existence, right up to the present day. Knowledge of what happened and the sequence in which it did so is still ragged, and since the creations that resulted from the marriage of the various bodies all have new names, too, the whole megillah adds up to a delicious tectonic confusion. In essence, though, it seems to have unrolled itself approximately thus:
First, about 1,800 million years ago, or maybe a little before, Arctica (which, it will be remembered, contained Siberia, Canada, Greenland, a bit of Wyoming, and the majestic monster called by some Kenorland) collided with Baltica, which held a great deal of what is now far northern Europe down to the Ukraine, and the two subsumed for good measure a small and noncontinental part of what is now the Antarctic. The resulting supercontinent has been called Nena (or Nuna to some, who claim it as an Inuit word that means “the land around us,” as in the recently formed Canadian province of Nunavut). Nena then collided with and promptly gobbled up Atlantica and became a truly vast body, which its namers (Americans) have seen fit to call Columbia (or, according to some others, Hudsonland). This enormous continent enfolded all of the world’s continental blocks for about 400 million years, then broke asunder once more around 1,300 Ma, whereupon its parts—behaving for the next 300 million years or so with the accordion-like back-and-forth squeezing and pulling apart that seems to have marked the world’s early progress—in due course collided with a re-formed Atlantica and a reinvigorated Ur and created yet another extrasupercontinent that has been called Rodinia, after the Russian word for “homeland.”
Rodinia then stayed stable, despite being so immense, for the next 300 million years—from about 1,000 Ma to 700 Ma, or the period known as the late Precambrian, when there was a fairly healthy amount of multicellular life to be found on the planet (fossils of which are scattered about the world’s outcrops today, in patterns that indicate where Rodinia had been stitched together). But then, and one hesitates to say once again, it fractured into a number of slightly different constituent parts—Laurentia, East and West Gondwana, bits of Ur, bits of Atlantica, all of which careened across the millions of square miles of crust before finally reassembling themselves into yet another body, which has been named Pannotia (which essentially means “all southern continents”). Another breakup, another reconciliation—and then, with some parts eventually drifting back together about 550 million years ago, and after a quarter of a billion more years of miniseparations and microdivorces, all were rejoined in an unholy tectonic matrimony almost exactly 280 million years ago, forming what we now know, with all the familiarity of its relative chronological closeness to us (a mere 250 million years, after all), as Pangaea.
From this point on, the world’s historical story becomes relatively plain sailing. It is generally very well known, but it belongs in its details to a later part of this story. The weird, almost biblical passages of complexity that speak of these places of a much greater antiquity—of Ur, and then of Atlantica, which in turn begat Rodinia; of Baltica, which begat Nena; and of Rodinia, which ultimately spawned Pannotia, which then in turn begat Pangaea—are daunting, to say the very least. But after the making of Pangaea 250 million years ago, all suddenly becomes much clearer. Pangaea ultimately split into two of its original building blocks, a northern massif called Laurentia and the more southerly and somewhat-better-known Gondwana. The two bodies then themselves began to fracture into a myriad pieces, the present-day oceans opened up, the present-day continents formed from the aforesaid myriad pieces, and these in turn—Africa, Europe, the Americas, Australia, Asia—started to pull apart from one another, or to travel toward one another, or to slide by one another; until eventually, with the exhausted arrival of all the continents, broken up, rewelded, reconfigured, and reconstituted in the approximate configuration of the present, geological history ended. The Triassic became the Miocene, then the Pliocene and the Pleistocene and the Holocene, and the present day arrived with its culminating finality.
For some, other explanations will become clear also. Once the awful rote of the supercontinents’ new names has been assimilated, and if all of this theorizing is borne out by fieldwork and the facts and proves to be more or less correct, then the perceived development of the earth that emerges assumes a simple elegance, a certain cosmic symmetry.
Punarapi jananam
Punarapi maranam
Punarapi janaijatare
Sayanam.
Adi Sankara’s famous sixth-century Sanskrit song “Bhaja Govindam” seems to have more than a little relevance here. Birth again; death again; repose in mother’s womb again.
Moreover, the simple elegance of the picture that emerges manages in an instant to answer, as plate tectonics answered in its early days, a lot of the very largest questions.
Why are there rocks both terribly ancient and extraordinarily modern smashed together in modern Greenland? Because, as the history above easily explains, what is now Greenland was once a group of freshly made granites that formed into something big enough to be called the continent of Arctica, and eventually Arctica became Columbia, Columbia evolved into Pangaea—and once Pangaea broke up in fairly modern times, the Atlantic Ocean opened up, the Mid-Atlantic Ridge fissured, and thick black basalts welled up—as they are still doing today on Surtsey. These spilled over and laid themselves down on the old Pangaea-Columbia-Arctica-Ur granitelike continental rocks that exist underneath, making the confection of geology that—in juxtaposition with all the ice and snow of climate and the storms and winds of weather, the polar bears and lichens of biology, and the Eskimo and Inuit and Danes and American soldiers of anthropology—constitutes the great and mysterious island known today as Greenland.
And the added beauty of the history is this: that this very same simple and elegant explanation can be wheeled out to offer valid answers to any of the major geological questions that scientists are currently pondering. What, for example, caused the terrible undersea earthquake in northern Sumatra in 2004, which sent up waves that killed hundreds of thousands in the Bay of Bengal? Why do large and very dangerous volcanoes threaten parts of the Congo? Why are there more than twenty huge volcanoes in the main islands of Indonesia? Why is the geology beneath Moscow, or around Hudson Bay, or southern Queensland, so disarmingly stable? What lies behind the creation of the newly found diamond deposits in the Yukon that have so excited Canada? Why are the Cyclades where they are? And Lipari, Tristan da Cunha, and Kerguelen? To answer any one of these questions one trundles out the same litany of proper names, the same descriptions of motion and rising and falling, and the same visions of long-vanished places: Ur, Pannotia, Gondwana, Arctica.
And why was there an earthquake on Wednesday, April 18, 1906, in San Francisco? The ultimate reason is just the same. The rocks shift, one set against the other, in California as everywhere else—for reasons that, at bottom, have everything to do
with the behavior of plates that are the legatees of Gondwana, Arctica, and Ur.
A CERTAIN NERVOUS SHAKING
It is a very long way, both in space and in time, from the continent of Ur to the city of Charleston, South Carolina. But Charleston, the pretty and some might say ostentatiously gracious colonial town that has lazed in the soft, wet heat of the Carolina coast since English settlers founded it in the late seventeenth century, is a place of great seismic interest, and so it is a place that has connections, and to geologists very interesting connections, with the making of the world’s ancient continents.
Not that anyone would have suspected such a thing, back when the town was founded. Charleston had just been sitting quietly and prettily on its coastline, its citizens unperturbed and their manners genteel—until the very last day of August 1886. On that day, however, and according to a resident named Paul Pinckney, something happened. There came a sudden slight vibration, he wrote, “as when a cat trots across the floor.”
This was the harbinger of what a few moments later would be the greatest eastern earthquake in American history—a powerful, deadly, and highly destructive quake that brought ruin and chaos in its wake.
But it was far from being the only eastern earthquake. My journey across the North American Plate was well under way; Iceland was far behind me, Greenland had faded into the background, and so had Newfoundland and Nova Scotia and the states of upper New England. Now I was driving in the area around my home in the Berkshire Hills of western Massachusetts,* and all the talk seemed to be of earthquakes. Stories about past earthquakes abounded. There seemed, all of a sudden, to be a surge of seismic activity in this particular corner of the plate. Many of my neighbors in the Berkshires, for instance, claimed to have felt earthquakes—one friend had been woken a few weeks before by a tremor that turned out to have had its epicenter in Amherst, Massachusetts, thirty miles from my home. The local seismic observatories say they record an average of forty earthquakes each year in New England, of which five are strong enough to be felt by any reasonably aware person.
In the American Northeast the geological factors that trigger earthquakes seem to be all around. Just to the west of New York City, for example, there is a fault system that runs in the same direction as the Appalachian Mountains that rise up to its west. These faults, running along what is known as the Ramapo Fault System, occasionally break along this northeasterly line, and, when they do, throw the torn sides upward, or downward, toward the southeast. Earthquakes, which are generally fairly minor and are felt only by a very few people, have thus been recorded sporadically all along the system for centuries.
Commuters will find it droll to realize that some of their rather commonplace hometowns are actually very well known in seismologists’ circles, because of historically important earthquakes that have taken place there: The Wappingers Falls Sequence of June 1974* and the Annsville Event of January 1980, for example, are two fairly recent events with considerable standing among those who catalog such things. Some of the states in the region are beginning to take the possibility of earthquakes more seriously than before—it used to be thought that quakes were more or less exclusive to California and the very active West—and Massachusetts, for one, has now added seismic requirements, albeit rather limited in their extent, in local building regulations.
The northeastern earthquakes may be more numerous than most outsiders suppose, but they are quite minor even at their worst. The same cannot be said, however, of what happened in Charleston: That was an almighty disturbance, well worthy of inclusion in the lists of the great and the dreadful.
But though what took place in Charleston was certainly terrifying, it did not come entirely without warning. Four days earlier, on Friday, August 27, up north in Summerville, a hamlet about twenty-five miles from Charleston, the entire population was stunned at about 8:00 A.M. by the sound of what they all thought was a tremendous explosion: A train boiler had blown up, some said; or the phosphorus plant on the far side of the river had caught fire; or a hidden stash of gunpowder had been detonated. But no, there was no ready explanation for something everyone had heard and felt. Though very few knew anything about earthquakes, a number of Summerville’s old-timers warned that perhaps this had been one. But the rest of the day passed without incident. Ah, well, they said collectively. Back to the porch and the evening julep. The morning papers would explain.
But next morning, Saturday, at 5:00 A.M., it all happened again. This time people were awakened, and many were tumbled from their beds by a sudden violent crash. For the rest of the day the earth below continued to tremble: Sometimes a series of inexplicable vibrations was accompanied by a slight rumbling sound, and at other times not. Anxious and afraid, the local burghers telegraphed their observations and their concerns to the state authorities. The newspapers across the state line in Georgia picked up on the fretful condition of their neighbors, did some perfunctory research, and began to worry themselves: An editorial in the Atlanta Constitution the next day warned that perhaps the area, which was usually seismically peaceful, was standing into danger.
On Tuesday evening the tension suddenly broke. Thomas Turner, the president of the Charleston Gas Light Company, had arrived home in Summerville in his carriage, weary from a day’s work at the office:
I had been out in the garden admiring the beauty of the evening and was entering the door of the hall of my house when, without any rumble or warning, the floor seemed to sink under me. I seized the door jambs to steady myself, when the floor seemed to go down in front of me at an angle of twenty-five or thirty degrees. It was so sudden and unexpected, that I was thrown forward into the hall about ten feet, and as quickly thrown backwards, and before I could fall upon the piazza I was again thrown forward into the house. At this moment I observed my sister-in-law crawling on all fours, she having been thrown from the door of her chamber, which she was just entering, into the middle of the sitting room. Amidst the rolling and rocking of the building she managed to reach the hall, but was unable to regain her feet. At this moment we observed the upper part of a lamp, which had been jerked off its stand, to fall upon the floor and burst. The oil took fire, and amidst the roaring and violent motions of the house, we succeeded in extinguishing it with pieces of carpet and rugs. Immediately after we received another shock, which threw us from side to side of the hall. Having gotten the members of my family together, and supporting my niece, who was in a fainting condition, we endeavored to leave the house amidst the crash of falling chimneys and plaster; but at every attempt to reach the door we were hurled backwards and forwards and from side to side, as if we had been in the gangway of a steamer in a heavy cross sea. After some delay we reached the garden. I then returned to get wraps and chairs for the ladies, and again experienced severe shocks and rumblings. These were repeated at intervals of several minutes during the night, but were not of so violent a nature, although the earth waves were very perceptible and several times upset a small lantern placed upon the ground.
Summerville seems to have been very close to the epicenter of what seismologists today believe was a magnitude 7 earthquake,* with a very concentrated episode of ground shaking in a corridor extending between the hamlet and Charleston itself.
Paul Pinckney then picks up the story. He was, as he wrote, “just a lad at the time,” but his memory of what occurred in the city remained with him for the rest of his life.
The Tuesday had been hot and sultry, and people were remarking on the unusual stillness of the day. Willis Carrier, the so-called Father of Cool, would not invent air-conditioning for another twenty years, and so the streets were thronged with people doing their best to escape the oppressive indoor heat. Many were returning from church: Even on a Tuesday, and even in a city better known for its soirées, black tobacco, and strong drink, the town maintained a veneer of southern piety. Thomas Turner’s gas lamps had just been lit, and groups of people gathered under their dim illumination to gossip, gawk, and ready themselves for home and b
ed. It was 9:51 P.M. Suddenly, something happened deep within the earth. And all the town clocks stopped dead.
It must have begun with a barely perceptible force. Then the deep-seated murmurings quickly became stronger, and within seconds the vibrations started to come, wrote Paul Pinckney,
in sharp jolts and shocks which grew momentarily more violent until buildings were shaken as toys. Frantic with terror, the people rushed from their houses, and in so doing many lost their lives from falling chimneys or walls. With one mighty wrench, which did most of the damage, the shock passed. It had been accompanied by a low, rumbling noise, unlike anything ever heard before, and its duration was about one minute.
Carl McKinley, who was a reporter on the Charleston News and Courier, was working in his second-floor office that evening. He was writing at his desk when his attention was “vaguely attracted,” as he later wrote, by a noise that seemed to come from the office below. It sounded like something rolling past down on Broad Street—an iron safe, he imagined, or maybe a heavily laden dray: