New Madrid, Missouri
New Madrid, Missouri
Those who think that earthquakes are strictly a California phenomenon might be amazed to learn that the most powerful earthquake in recorded American history occurred in the middle of the country near New Madrid (pronounced MAD-rid), Missouri. Between December 16, 1811, and February 7, 1812, about 2,000 tremors shook southeastern Missouri and adjacent parts of Arkansas, Illinois, and Tennessee. The largest of these earthquakes is thought to have had a magnitude of 8.8 on the Richter scale, making it one of the most massive ever recorded.
Witnesses reported shocks so violent that trees 6 feet (2 meters) thick were snapped like matchsticks. More than 150,00 acres (60,000 ha) of forest were flattened. Fissures several yards wide and many miles long split the earth. Geysers of dry sand or muddy water spouted into the air. A trough 150 miles (242 km) long, 40 miles (64 km) wide, and up to 30 feet (9 m) deep formed along the fault line. The town of New Madrid sank about 12 feet (4 m). The Mississippi River reversed its course and flowed north rather than south past New Madrid for several hours. Many people feared that it was the end of the world.
One of the most bizarre effects of the tremors was soil liquefaction. Soil with high water content was converted instantly to liquid mud. Buildings tipped over, hills slid into the valleys, and animals sank as if caught in quicksand. Land surrounding a hamlet called Little Prairie suddenly became a soupy swamp. Residents had to wade for miles through hip-deep mud to reach solid ground. The swamp was not drained for nearly a century.
Some villages were flattened by the earthquake, while others were flooded when the river filled in subsided areas. The tremors rang bells in Washington, D.C., and shook residents out of bed in Cincinnati, Ohio. Since the country was sparsely populated in 1812, however, few people were killed.
The situation is much different now, of course. The damage from an earthquake of that magnitude would be calamitous. Much of Memphis, Tennessee, only about 100 miles (160 km) from New Madrid, is built on landfill similar to that in the Mission District of San Francisco where so much damage occurred in the earthquake of 1990. St. Louis had only 2,000 residents in 1812; nearly a half million live there now. Scores of smaller cities and towns lie along the fault line and transcontinental highways and pipelines cross the area. Few residents have been aware of earthquake dangers or how to protect themselves. Midwestern buildings generally are not designed to survive tremors.
Anxiety about earthquakes in the Midwest was aroused in 1990 when climatologist Iben Browning predicted a 50-50 chance of an earthquake 7.0 or higher on or around December 3, in or near New Madrid. Browning based his prediction on calculations of planetary motion and gravitational forces. Many geologists were quick to dismiss these techniques, pointing out that seismic and geochemical analyses predict earthquakes much more accurately than the methods he used. Although there were no large earth quakes along the New Madrid fault in 1990, the probability of a major tremor there remains high.
While the general time and place of some earthquakes have been predicted with remarkable success, mystery and uncertainty still abound concerning when and where "the next big one" will occur. Will it be in California? Will it be in the Midwest? Or will it be somewhere entirely unexpected? Meanwhile, residents of New Madrid are planning emergency exit routes and stocking up on camping gear and survival supplies.
[William P. Cunningham Ph.D. ]
Finkbeiner, A. "California's Revenge: Someday a Major Earthquake Will Ravage the United States–in the East." Discover 11 (September 1990): 78–82, 84–5.
Johnson, A. C., and L. R. Kanter. "Earthquakes in Stable Continental Crust." Scientific American 262 (March 1990): 68–75.