Earthquakes can occur in the Lower Mississippi Valley

Over two centuries ago, during the winter of 18111812 a series of earthquakes occurred in what was then the country’s western frontier.

A great earthquake on December 16, 1811, marked the beginning of a set of earthquakes that occurred in northeast Arkansas and southern Missouri. The largest earthquakes were felt from Canada to New Orleans to the Atlantic coast. Earthquakes and aftershocks are estimated to have lasted two years.

With no seismic stations in 1811, the exact number of earthquakes that occurred because of the New Madrid event remains unknown. The most noted damage was to the small settlement of New Madrid, situated along the banks of the Mississippi River in southern Missouri. As a result of the earthquake and erosion of the river shortly thereafter, the town literally slid, piece by piece, into the Mississippi River and was washed downstream. The present town of New Madrid is located near the original site, but behind a levee. Today, this zone is referred to as the New Madrid Seismic Zone in honor of this small frontier town.

Eyewitness accounts of the events were collected years afterward by several authors. The descriptions of the events are impressive. There were few settlers in the area, so damage to structures was low, but destruction of the local forests was extensive. The accounts describe surface waves that moved along the ground surface like ripples on water when a pebble is thrown into a pond.

These ground waves moved through the countryside and caused damage to the woodlands as trees “rode over” the top of the wave. There was extensive caving of banks along the Mississippi River and on steep slopes away from the river. When these slopes failed, a mass of mixed trees and soil came to rest at the base of the slope. Islands in the Mississippi River disappeared as far south as Island 94 near Vicksburg.

Perhaps the largest factor affecting the woodlands was abrupt changes in the elevation of the land surface. Extensive areas extending from Arkansas northward into Missouri are often referred to as the

“sunken lands.” In much of this area the land surface sunk as much as 20 feet, turning upland forests into swamps. The abrupt change from dry uplands to water-saturated swamp environments caused an extensive die-off of upland species of trees.

The New Madrid faults are still active and capable of generating damaging earthquakes. The Mississippi Emergency Management Agency has estimated potential damage to Mississippi, due to a magnitude 8 earthquake in the New Madrid Seismic Zone, would be more than $3 billion. A study at the University of Mississippi suggested a similar earthquake scenario could result in more than $112 million of damage just at the main campus.

Contact your local emergency manager and find out what they are doing on a local level to inform government and private citizens about earthquake preparedness. They can also advise you on what to keep on hand in the event we should ever have an earthquake.