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In Search of Ancient Earthquakes Volume 59 Number 1, January/February 2006
By Lois Wingerson

Can archaeologists help predict the next big one?

[image] Jim Price discovers evidence of a prehistoric earthquake at the Towosaghy mound near New Madrid, Missouri. (Courtesy Michael Fuller) [LARGER IMAGE]

As Jim Price recalls, at the time it was just another job: Excavate the odd bulge on the east side of the main mound at the Towosaghy site near New Madrid, Missouri, and record the staircase everyone expected him to find. The mound builders of the prehistoric Mississippian culture had put a temple atop the 16-foot-tall earthen structure; logically, they would have built stairs to reach it.

Starting outside the base of the mound, he dug step trenches into the slope. "Here's what the bulge turned out to be," he says. "About A.D. 1400, the occupants of the Towosaghy site burned their temple. They took all the debris and dumped it down the side of the mound. There was lots of burned clay--the daub from the wattle-and-daub structure--baked very hard in tremendous quantities." Mingled with the charcoal and ashes, the University of Missouri archaeologist found ceremonial pottery, ornamental ear spools, and mushroom-shaped labrets designed to be worn in the lower lip.

That the Late Mississippian residents torched and then deliberately trashed their temple was startling enough. But what sent Price straight to the telephone were the sand-filled cracks in the trench. He needed to call a geologist to be sure, but Price immediately suspected the truly astonishing implications: that the violent and devastating earthquakes that rocked the New Madrid area for two years, starting in 1811, were not a singular event. It had happened before and could happen again.

[image] Like a bull's-eye in the Midwest, the New Madrid fault stands out on a map showing the earthquake hazard levels in the continental United States. [LARGER IMAGE]

The largest of the 1811 quakes are estimated to have reached 8 on the Richter scale--even stronger than the famous San Francisco quake of 1906. Their epicenter was at New Madrid near the Mississippi River, but there were reports of tremors as far away as Detroit, Pittsburgh, Cleveland, and Charleston. In Boston, the ground shook so hard that the church bells rang. The New Madrid earthquakes overshadow all other midcontinent quakes recorded before or since. Altogether, they surged through more than 5,000 square miles of land--from southern Illinois to northern Arkansas and from eastern Missouri to western Tennessee and Kentucky. Some of that land can't bear crops to this day, in part because of the "sand blows" left by the eruptions, which covered nearly a thousand square miles and are still clearly visible.

Geologists familiar with the region used to assume that the 1811-1812 New Madrid disaster was no cause for concern to current residents of Illinois, Missouri, Arkansas, Tennessee, and Kentucky. Then in 1989, archaeologist Jim Price took a shovel to a temple mound near New Madrid. And that reassuring picture was abruptly shaken apart.

Lois Wingerson, a science writer based in Brooklyn, is author of Unnatural Selection: The Promise and the Power of Human Gene Research.

© 2006 by the Archaeological Institute of America