Shortcut Navigation:

The New Madrid Seismic Zone

megan_pic

By: Megan
Grade: 12
State: Wisconsin


To the Methodist population of the little western towns of New Madrid and Little Prairie, Missouri, the earthquakes of December 1811 through February 1812 were a demonstration of the wrath of god.

Several ministers openly rejoiced at the trembling of "sinners" who feared facing their Maker. During one of the quakes, a minister, James B. Finley, leaped on top of a table and shouted, "The Great day of His wrath is come, and who shall be able to stand?"

In the pioneer towns of New Madrid and Little Prairie, what else could explain the unearthly and terrifying happenings of those three months? For three nights the air had been thick and heavy, but December 16 was clear, cold, and quiet. Then it began—the rumbles of a "loud and distant thunder" moving closer. Jars started to hop off their shelves and log cabin walls began to dance. The people ran out into the cold night, bricks from their chimneys falling behind them. They huddled there in the darkness of a pre-electric-light world as the ground continued to shudder every 8 to 30 minutes. The night that had begun quietly now was filled with the screeching of birds and animals. Trees would sway and creak, becoming tangled in each others branches, and then crack and break from their inability to move.

megan_map1

Intensity map of New Madrid Earthquakes


At dawn the town was still black as night. Fog and rotten-egg-smelling vapors hung in the air and blocked the sun's rays from lighting the destruction of the two towns. At seven that morning another large earthquake struck, and the ground began to move in billowy patterns like sea waves. Great fissures opened up and depressions in the ground burst, spurting a mix of sand, lukewarm water, carbonized wood, small rocks, coal, and vapors. This earthquake did in the entire riverbank by Little Prairie, and Little Prairie flooded. Settlers were forced to wade through eight miles of chilly, muddy water and darkness to get to higher ground. The ground and water were still shaking periodically, and the terrified settlers had to pick their footing carefully, unable to know whether they were about to trip over a submerged fallen tree or step off into oblivion. The settlers also had to be aware of snakes and other wild animals that were swimming for their lives. When they reached higher ground, they began their long trek to New Madrid, the old paths made strange by a mess of fallen trees and branches, crevices, and quicksand. In Ben Chartier's firsthand account of that first night of quakes when he and his family fled from Little Prairie, he describes the ground breaking open into a fissure, and he and his family having to "coon across" the fissure on fallen logs.

At 11a.m. another earthquake hit—the strongest of the three earthquakes that day—then there was a settling. But that was not the end. On January 23 there was another strong earthquake, and by February 4 Eliza Bryan (one of the New Madrid
townspeople) wrote that Earth was in continual movement.

During this time of shaking, the Mississippi River—the powerful neighbor of both towns—turned a rusty brown and developed waves 30 feet high that sometimes traveled horizontally to beat on one bank and then on the opposite bank. Fish were thrown, flopping, onto land, and the battered riverbanks weakened. John Bradbury, a British botanist who was traveling in a keelboat on the Mississippi at the time of the quakes, described the steep banks of the river "both above and below" them as beginning to "fall into the river in such vast masses, as nearly to sink our boat by the swell they [caused]." Other eyewitness accounts described spouts of water shooting up from the Mississippi and the river opening up into whirlpools and the water disappearing into dark holes at their centers. Some rivermen told of the
Mississippi receding from its banks, leaving small boats sitting helpless on the sand, then rising into a wall of water 15-20 feet straight up, and crashing down, crushing the boats and overflowing the banks.

On February 7, 1812, the greatest of the quakes struck, and the Mississippi River flowed backward for several hours. Two waterfalls were created in the river by New Madrid so that the river dropped off six feet into a mile of shallow rapids. The falls lasted for a few days, and during this time the people of New Madrid saw 30 boats plummet over the falls. Twenty-eight of those boats capsized, and the townspeople could hear screams for help from the river but could do nothing.

Most of the casualties caused by the New Madrid earthquakes were drownings as the river came to vengeful life. However, the casualties were very small in numbers, as Missouri in 1812 was still a very rough and sparsely populated region of the young United States. Because of the few casualties and little damage, very few people remember these violent quakes—some of the strongest North America has experienced since European colonization. Tremors were felt in 28 states—from upper Canada to Cuba and Mexico. Vapors filled the air in South Carolina, light flashes were seen in Savannah, clocks stopped in Norfolk, church bells rang in Boston, sidewalks buckled in Baltimore, and chimneys fell in Cincinnati. The quakes permanently changed the course of the Mississippi River, created and destroyed lakes, and lowered 30,000 square miles of land 6 to 15 feet.

I first ran across information about these quakes when researching the San Francisco earthquakes for the 1999 Young Naturalist Awards Essay. I was amazed that the most violent quakes in U.S. history had happened in the Midwest, of all places, and that I had never before heard of them. The idea that an earthquake zone existed in the Midwest and that a recurrence of these fearsome earthquakes might be felt from my home in Verona, Wisconsin, fascinated me. We hear warnings about tornadoes and snowstorms all the time in Wisconsin, but earthquakes? Moreover, one of the colleges I am considering, Grinnell College in Iowa, is right in the moderate damage range. Chicago, my old hometown, is also threatened—and there are far more people living there now than there were in "Fort Dearborn" at the time of the 1811-1812 earthquakes.

Fascinated, I abandoned all of my research on San Francisco to pursue some vague leads about "the hills of Missouri shaking like Jell-O." What would cause such a strong earthquake in the middle of a continental plate? What caused all of the strange phenomena reported in those eerie eye-witness accounts—light flashes, fissures, whirlpools, and the Grand Mississippi herself flowing backward?

From my research it appears that, although the science of geology and plate tectonics has developed exponentially this past century and a half, and many of the strange phenomena that occurred during these earthquakes have been explained, much of the actual underworkings of Earth that cause intraplate earthquakes are almost as mysterious as the New Madrid and Little Prairie Methodists' "wrath of God." There are theories, however.

To begin with, Earth's crust is formed of a jigsaw of continental and oceanic "lithospheric" plates. These plates, which float on the hotter plastic mantle below, have drifted over the past 200 million years to their present positions. As the plates slowly move, they sometimes collide or develop friction. Ninety percent of earthquakes are a release of pressure on plate boundaries due to collisions or friction.

Ten percent of earthquakes, however, are not. The earthquakes of the New Madrid Fault System are included in this 10 percent. The New Madrid Fault System is located hundreds of miles away from either boundary of the North American continental plate. Earthquakes that do not occur on the boundaries of tectonic plates are called intraplate earthquakes.

It is hypothesized that at one time, a very long time ago, the world's seven separate continents were all part of one large supercontinent called Pangaea. Rifts developed in the Pangaea supercontinent, and where those rifts formed, magma continued to well up to form new crust between them. These expanding rifts became our present day oceans.

During this time of stress, when the continental crust was being ripped open to form the North American plate and the proto-Atlantic (the precursor of the Atlantic Ocean), a rift began to form, but failed, in the middle of what is now the North American continent. The Reelfoot Rift, as it is now called, is called a failed rift because it did not completely split—otherwise there would be an ocean where there is presently the Mississippi River. Instead, a narrow sunken rift developed—around 25 miles deep and extending all the way through the crust to the mantle below. The Reelfoot Rift runs the course of the Mississippi River, from where it meets the Ohio River down to where it flows into the Gulf of Mexico. The Reelfoot Rift is the largest failed rift in the North American Plate.

When the Reelfoot Rift was attempting to split, large areas of rock sunk down about a mile or so into cracks formed along the rift. These areas of rock are called grabens. One huge graben—approximately 120 miles long and 40 miles wide—is located in the Reelfoot Rift. A large fault—possibly 15 miles deep and running from Cairo, Illinois, down to Northeastern Arkansas—runs through the middle of this graben. This large fault is the New Madrid Seismic Zone.

There are several theories about what causes earthquakes in this region—especially the massive earthquakes of 1811-1812. One theory is that because the Reelfoot Rift is a weak spot in the North American Continental Plate, the stresses and pressure of the plate are likely to be released there. This theory contends that the North American Plate is presently being compressed. It is being pushed westward from where the magma wells up and forms new crust along the plate boundary in the Atlantic Ocean, and it is being pushed eastward by the friction along the San Andreas Fault. The pressure of this compression is released through intraplate earthquakes.

mega_seismic_waves

Seismic waves


Body waves emanate from the hypocenter and travel out towards the surface. There are two different categories of body waves: primary or pressure (P) waves and secondary or shear (S) waves. P waves travel like sound waves through Earth and cause up-and-down motions when they reach the surface. P waves are the cause of the "loud and distant" thunder so commonly described in New Madrid firsthand accounts. S waves approach the surface with half the speed of P waves and snake through the ground like whips. S waves cause the back and forth movement of the ground during an earthquake. There are also two different categories of surface waves or L (long) waves: Rayleigh waves and Love waves. Surface or L waves originate at the surface. These waves also travel much slower than body waves. Rayleigh waves cause the billowy ocean-like movements of the ground witnessed in the New Madrid earthquakes. Love waves whip back and forth horizontally at a right angle to the direction they are traveling, like a snake.

These seismic waves are the cause of the huge fissures that opened up, such as the ones that Ben Chartier and his family had to "coon" across. Some were as long as five miles, 20-feet deep, and wide enough to swallow a horse. The waves cause clay-like soil to weaken and break up, forming these crevices in the ground surface—an earthquake hazard that is a type of "ground failure." When fissuring occurs beneath a body of water, such as the Mississippi, bizarre occurrences, such as whirlpools, waterfalls, or the reported 30-foot waves are created. There is also a theory that a huge underwater fissure, which sucked water into itself from both directions, was the cause of the Mississippi River flowing backward for several hours on February 7.

Another type of ground failure is "liquefaction." Liquefaction occurs when the seismic waves transform sandy, water-saturated soil from solid ground into an almost liquid state—like quicksand. Liquefaction can cause the mix of sand, water, and other substances described by witnesses of the New Madrid quakes to be spurted from the ground in "sand blows." Liquefaction may also cause soil to become more compacted and sink. Other times soil compression may cause the ominous flashes of light described by people across the United States during the New Madrid quakes. When an earthquake is of great enough strength to squeeze the quartz crystals present in the soil, the resulting voltage emits an eerie light.

Predicted intensities from 6.5, 7.5, and 8.5 magnitude earthquakes.


megan_scale1

U.S. Geological Survey's Modified Mercalli scale key for predicting intensity diagrams


We may have gained insight into the New Madrid Methodists' "wrath of God" over the past few centuries, but we are just as helpless to prevent it as they were. With earthquakes, it is said that it is not a matter of probability but a matter of inevitability. If incredible earthquakes have turned the hills of Missouri to Jell-O in the past, given time, they will again. It is simply a matter of how soon. Each year the New Madrid Seismic Zone is shaken by an average of 200 minor (magnitudes 3.0-4.0 on the Richter scale) earthquakes. The probability of a damaging earthquake (6.0 or greater) occurring within the next 15 years is significant—somewhere in between 40-63 percent, and within the next 50 years it is almost inevitable—around 86-97 percent. An earthquake of this magnitude would cause damage to many older structures. The probabilities of a major earthquake of magnitude 7.0 or greater are estimated around 5-9 percent for within the next 15 years, and 19-29 percent within the next 50 years. An earthquake of this magnitude could cause billions of dollars of damage and be felt throughout most of the United States. The probability of a larger earthquake—one with the catastrophic magnitude of the New Madrid Earthquakes of 1811-1812 (8.0 or greater), has a very small yet threatening possibility—0.3-1 percent chance within the next 15 years, but 2.7-4.0 percent within the next 50 years (a chance of almost 1 in 25).

Will the Midwest be prepared for the next damaging earthquake? The little towns that were shaken up in the early 1800s are now major cities—Nashville, St. Louis, Little Rock, Indianapolis, and Frankfort would have all been within the "destructive" range of the 1812 quakes. Most of the Midwest and a large part of the South would have been within the "strong" range—including what is now the Midwest's largest city, Chicago. Approximately 70 million people live in areas where the earthquake risk is deemed serious. One hundred and twenty million people live in areas considered "moderate risk." The city of Memphis, with over a half-million people, is situated only 25 miles from the fault. Also, Memphis is built on semiconsolidated rock covered with crumbly soil and floodplain deposits, making it incredibly vulnerable to liquefaction. In the case of a major earthquake, Memphis is very likely to be in ruins. It is estimated that if a major earthquake were to happen during business or school hours, the injuries and deaths would be counted in the thousands.

After the New Madrid Earthquakes of 1811-1812, those residents of the affected states that still remained in the area took as direct an action as they knew to prevent the recurrence of the "wrath of God"—they joined churches and repented for their sins. In the years following the earthquakes, Methodist church membership grew by over 50 percent in nine states. In the 1980s and 1990s the legislatures of Missouri, Tennessee, and Kentucky also took as direct an action as they knew—not to prevent future earthquakes but to attempt to lessen their destruction. The Central United States Earthquake Consortium was formed in 1981 to enable local governments to call on emergency crews in nearby cities and states when their own emergency systems are debilitated. In 1990, a bill was passed in Missouri that required all public buildings in at-risk counties to be built to withstand earthquakes and required earthquake drills in schools. Some towns near the fault line have had their schools rebuilt or remodeled to make them more earthquake resistant. However, the New Madrid Seismic Zone is far from being as prepared as earthquake-prone California. Most people living within the reaches of its widespread tremors are still blissfully unaware of the time bomb that might be ticking beneath them.

To me, the New Madrid Earthquakes are a reminder of a fact I often forget-that there is so much in our lives outside of our control. Even though I live in as seemingly safe a place as the Midwest, who knows when my whole world may shift out from beneath my feet.

 

References

Atkinson, William. The Next New Madrid Earthquake: A Survival Guide for the Midwest. Carbondale, Illonois: Southern Illinois University Press, 1989.

Bagnall, Norma Hayes. On Shaky Ground: The New Madrid Earthquakes of 1811-1812. Colombia, Missouri: University of Missouri Press, 1996.

Bolt, Bruce A. Earthquake. New York: W.H. Freeman and Company, 1993.

Coffman, Jerry L., ed. Earthquake History of the United States. Boulder: Government Printing Office, 1982.

"Earthquake Facts and Follies." 23 Dec. 1998. http://www.ceri.memphis.edu/www/public_info/follies.html

"Earthquake FAQs." 23December 1998. http://easternweb.er.usgs.gov/eastern/earthquakes

"An Introduction to Plate Tectonics." 3 Jan. 1999. http://www.eas.slu.edu/Peopl....lasses/IntroQuakes/Notes/plate tect01.html

Nuttli, Otto W. ed. "Contemporary Newspaper Accounts of the Mississippi Valley Earthquakes of 1811-1812." 1972. http://www. eas.slu.edu/EarthquakeCenter/Nuttli.1973/nuttli-73-app.html

Penick, James Lal. The New Madrid Earthquakes. Colombia, Missouri: University of Missouri Press, 1981

Walker, Bryce. Earthquake. Alexandria, Virginia: Time Life Books, 1982.

"World Seismic Hazards." 23 December 1998. http://geohazards.cr.usgs.gov/factsheets/pulse/worldhaz.html

American Museum of Natural History

Central Park West at 79th Street
New York, NY 10024-5192
Phone: 212-769-5100

Open daily from 10 am - 5:45 pm
except on Thanksgiving and Christmas
Maps and Directions

Enlighten Your Inbox

Stay informed about Museum news and research, events, and more!