“Fine,” Omar said. Knox bounced out of the room. Omar gazed after him thoughtfully. Knox, planning who knew what with his buddies, made him uneasy, but whatever it was that Knox was planning, he looked to be doing it elsewhere.
A Micah Knox elsewhere was a Micah Knox that Omar didn’t have to worry about. And Omar figured he had enough worries as it was.
FOURTEEN
There has been in all forty-one shocks, some of them have been very light; the first one took place at half past 2 on the morning of the 16th, the last one at eleven o’clock this morning, (20th) since I commenced writing this letter. The last one I think was not as severe as some of the former, but it lasted longer than any of the preceding; I think it continued nearly a minute and a half. Exclusive of the shocks that were made sensible to us in the water, there have been, I am induced to believe, many others, as we frequently heard a rumbling noise at a distance when no shock to us was perceptible. I am the more inclined to believe these were shocks, from having heard the same kind of rumbling with the shocks that affected us. There is one circumstance that has occurred, which if I had not seen with my own eyes, I could hardly have believed; which is, the rising of the trees that lie in the bed of the river. I believe that every tree that has been deposited in the bed of the river since Noah’s flood, now stands erect out of the water; some of these I saw myself during one of the hardest shocks rise up eight or ten feet out of water. The navigation has been rendered extremely difficult in many places in consequence of the snags being so extremely thick. From the long continuance and frequency of these shocks, it is extremely uncertain when they will cease; and if they have been as heavy at New Orleans as we have felt them, the consequences must be dreadful indeed; and I am fearful when I arrive at Natchez to hear that the whole city of Orleans is entirely demolished, and perhaps sunk.
Immediately after the first shock and those which took place after daylight, the whole atmosphere was impregnated with a sulphurous smell.
The first big May quake—M1, as it was later known—began at 5:19 Central Daylight Time as a sudden ten-meter bilateral dextral strike-slip motion along the whole length of the twenty-five-mile Reelfoot rift, a subterranean fault structure running beneath the Mississippi from Missouri to Tennessee. The Reelfoot rift intersects several other faults or fault segments—the Bootheel lineament, the New Madrid north fault, the New Madrid west seismicity trend, and others. The Bootheel lineament in turn intersects the fifty-mile-long Blytheville arch, an axial fault running more or less beneath the Mississippi. The original Reelfoot slip triggered further slippage and upthrusting along all nearby faults, each fault contributing in its turn to the intensity of the destruction—over 150 miles of built-up tectonic energy cutting loose at nearly the same instant. The shock waves from this massive disturbance traveled across mid-continental North America with admirable efficiency.
Most earthquakes occur near the boundaries of the earth’s tectonic plates, the giant twenty-two-mile-thick pieces of the earth’s crust, which drift slowly and massively on the semi-liquid mass of the planet’s interior. The collisions of the earth’s plates throw up mountain ranges, cause deep fractures in the earth’s crust, and precipitate almost all the earthquakes in the world. California’s famous San Andreas fault runs along the boundary between the Pacific plate and the North American plate, which are grinding against one another as they move in opposite directions.
The quakes generated at the edges of plate boundaries tend to be limited in scope. The fractured nature of the earth itself tends to disperse the tremblors, or channel them into a small area. The great San Francisco earthquake of 1906 was a stupendous 8.3 on the Richter scale, but most of the destruction was confined to a compact part of the Bay Area, and deaths were limited to about 700. The San Fernando quakes of 1994 were likewise restricted to a small area, and caused less than a hundred deaths.
But the Reelfoot rift and other mid-American fault structures are not situated on a plate boundary, like the San Andreas fault. They are square in the middle of a very solid continent, and when something hammers the bedrock of the Midwest, the North American plate rings like a giant bell. There is nothing to stop the quake energy from traveling hundreds of miles from the epicenter. P and S waves leaped from the fracture zones at a speed of around two miles per second, and the terrifying Rayleigh and Love waves, though moving a little more slowly, propagated across the American continent and through the entire structure of the earth, met on the far side of the planet, then returned, circling the globe a half-dozen times before subsiding.
The particular structure of the Mississippi Valley contributed to the catastrophe. A hundred and ninety million years ago, the North American continent almost split in two along the line of the Mississippi Valley. Had this geological action continued, a rift valley would have formed, similar to the Great Rift Valley in Africa. But the continent seemed to have changed its mind. The rift never formed, but the geological action left behind weaknesses in the earth’s crust, including the tangle of faults around New Madrid.
The Mississippi River, magnificent as it is, follows the course of what once was an even more magnificent bay, a branch of the ocean that reached as far north as Cape Girardeau, Missouri. Over hundreds of centuries, the Mississippi gradually filled this bay with sediment, creating the Mississippi Delta that stretches from Cape Girardeau to the Gulf of Mexico. The sediment—soil, mud, clay, gravel, vegetable matter, sand—is in some places thousands of feet thick.
When the Mississippi periodically flooded and covered a part of the Delta with a new layer of soil, the soil was intermingled with water and air. Over the course of many years, the water and air normally percolate to the surface and disperse. But if the Mississippi flooded again before this could take place, laying down another layer of a less permeable sediment—clay, for instance—then the water and air was trapped beneath the surface, and as more and more heavy layers of alluvial soil was deposited on top, this water and air was put under enormous pressure.
With layers of clay or other heavier sediment sitting atop a goo of soft soil mixed with air and water, the geology of the Mississippi Valley resembles nothing so much as a layer of bricks placed carefully on a foundation of Jell-O.
The bricks are perfectly stable, so long as nothing shakes the Jell-O.
But when the complex of fault structures beneath the Mississippi snapped, the carefully balanced structure was disrupted. Pressurized water and air blasted its way to the surface, resulting in the so-called “sand blows,” thousands of geysers bursting through the surface to loft water, sand, coal, ancient chunks of wood, and rocks far into the air. More water found its way to the surface in less violent fashion, as M1’s power liquified the alluvial soil.
It is common for sediment or fill to liquify during an earthquake. Otherwise solid structures, built on alluvium, suddenly find themselves supported by nothing more solid than soup. Sometimes they can tumble downhill like a winter tourist on an inner tube. Much of the property damage suffered during the Bay Area quake of 1989 occurred in the Marina District, a part of San Francisco built on fill. All of the Mississippi Delta—all of it, from Cape Girardeau south—is alluvial soil. Structures everywhere suffered catastrophic failure. Levees, dikes, and flood walls were broken, or weakened. Riverbanks collapsed. Whole forests were laid low. Water geysering into the sky or welling up through the sediment poured off the saturated land to join rivers already filled with spring snow melt. Even areas built on solid ground did not fare well. The Chickasaw Bluffs, standing above the Mississippi Valley in Tennessee and Kentucky, were subject to landslides that dropped trees, roads, and expensive houses into the valley below. Cape Girardeau suffered a failure of its flood wall, and the lower part of town was inundated. The old French town of Ste. Genevieve, south of Girardeau in Missouri, was likewise partially flooded, and lost several of its historical structures to the flood or to the quake. The Mississippi town of Natchez, with its proud, pillared collection of antebellum mansions perched atop the loess bluff, windblown soil piled high in the last Ice Age, lost a small city park to landslide as well as a quintessential Southern mansion house, Rosalie, built in 1820. Natchez also lost its riverboat gambling venue when a landslide spilled right through the rough old port town of Lower Natchez and into the casino boat, sinking it at its moorings.