A professor at the University of Northern Iowa says he has visual proof of the effects of a famous historical earthquake that rattled this central part of the United States. Kenneth DeNault says nearly a century ago this was a geologically active region.
There was a large “set” of earthquakes beginning late in 1811 and continuing into the year 1812 centered around the town of Mew Madrid on the Mississippi River. DeNault says the quake still quivers. To this day there are tiny “micro-seisms,” miniature earthquakes in this area so small you can’t even feel them. DeNault says that’s because there’s a break in the continental mass and the quakes are the result of movement on both sides.
California, by contrast, has a lot of fractures underground that let stress be released in many earthquakes. DeNault says Iowa doesn’t have those fractures, and doesn’t have many quakes as a result. Here, stress can build up for a long time without being released, the way a watch-spring might get wound up or a stick be slowly bent until it breaks. With a longer time period for the buildup of stress, comes a bigger earthquake, and it had been a long time before the New Madrid earthquake.
DeNault says there are Indian legends of big earthquakes farther back in the history of the region, but no way to verify them scientifically. A professor of geology at U-N-I, DeNault says he has slides showing some of the effects of the New Madrid quakes. Driving along Interstate-35 he says a trained eye can spot “subsidence,” areas where the land sank during the historic quakes, and other subtle changes they made to the land.
There are places where the path of the Mississippi has “peculiar” passages, made or influenced by the quakes nearly 200 years ago. But Professor DeNault doesn’t recommend trying to build quake-proof buildings or taking other precautions, pointing out Iowas who want to be ready for natural disaster would be better off making plans in case of things like tornadoes, which happen a lot more often.