An explanation for the New Madrid earthquakes has resurfaced online for one astonishing reason: It tells the story of how the most powerful earthquake in modern U.S. history briefly caused the Mississippi River to flow backward.
According to Popular Mechanics magazine, seismologist Otto Nuttley later estimated the magnitude of the three main shocks at approximately 7.2, 7.1, and 7.4 on the body wave scale. In later studies, he suggested an even greater magnitude for the surface waves, which, if these estimates are correct, could make the February 7 earthquake the strongest ever recorded in the continental United States.
Renewed interest is focused on the New Madrid earthquakes—a series of powerful earthquakes that struck the central United States between December 1811 and February 1812. Although the region is far from the country's most prominent seismic centers, the shaking was so powerful that islands were swallowed by the earth, new lakes were formed, and the Mississippi River underwent significant changes in shape.
The first major earthquake occurred on December 16, 1811, followed by powerful aftershocks and additional strong earthquakes on January 23 and February 7, 1812. One of the old-timers, Eliza Bryan, described "a great shock of the earthquake" and "the roar of the Mississippi," adding that the river's course "reversed for a few minutes.".
The New Madrid earthquakes were intraplate, meaning they occurred in the middle of a tectonic plate, rather than near a plate boundary, such as the San Andreas Fault in California.
Even in the early 1800s, when the region was much less populated, earthquakes caused widespread destruction.
Landslides destroyed riverbanks, cabins collapsed so frequently that many residents reportedly retreated to tents, and the tremors were felt hundreds of kilometers away. Bells are said to have rung in Boston, and Dolley Madison was awakened in Washington, D.C.
Given that the region is much more densely populated today, experts estimate the likelihood of a similar event to the New Madrid disaster within the next 50 years to be approximately 7-10%.
In his account, the eyewitness described what he saw as "truly horrific," accurately conveying the fear of the residents who could not find a modern explanation for what was happening.
A rift in the Earth's crust in central North America could have caused a catastrophe powerful enough to briefly reverse the flow of a major river.
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