Apparently, massive earthquakes (reaching magnitudes of 7.0 and 8.0) struck Middle America between December 1911 and February 1812. (The largest of those quakes caused the Mississippi River to flow backwards temporarily!)
The area of the quakes, New Madrid Missouri, isn’t located at the intersection of tectonic plates, so why did earthquakes of such magnitude strike there?
Courtesy National Center for Earth-surface Dynamics (NCED)Well, a paper recently published in the journal Nature suggests that the earthquakes were due to the actions of our beloved mighty Mississippi River.
The idea is that the Mississippi rapidly eroded tons of soil—39 feet of sediment from the river basin—at the end of the last ice age (around 16,000 years ago). That “quite dramatic” erosion (which occurred over a period of 6,000 years, but I guess is considered “rapid” in geological time) set in motion the events that would lead to the New Madrid quakes, as Roy Van Arsdale, a geologist and co-author of the study told msnbc.
Courtesy National Center for Earth-surface Dynamics (NCED)Van Arsdale and fellow authors suggest that the erosion of the sediment released a lot of weight from the Earth’s surface, causing it to buckle just like a stick that is bent from both ends. Imagine bending a stick in your mind, and you will see that in the middle, bending part of the stick, the top part curves upward and is stretched. The bottom part is compressed. In the case of the Earh's crust, the stretching creates faults, or cracks, in the crust. The study's authors suggest that the faults failed in 1811 and unleashed the Earthquakes of New Madrid.
So there you have it, earthquakes in the middle of the country (which is apparently the the country's most earthquake-prone region outside California! Who knew?!) caused by our old familiar mighty Mississippi.