RIDGE RUNNER CHRONICLES: Why The Next “New Madrid Earthquake” Will Be Much Worse Than Those Quakes in California
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If you live in the Mid-West, you probably have heard that sooner or later, there will be a huge earthquake centered somewhere along the lower Mississippi River. What you might not know is that this anticipated earthquake has the potential to be much more destructive than any of those California earthquakes that seem to happen every few months. So let’s take a brief look at why an earthquake along the Mississippi could be so severe.
There is an area in the lower Mississippi, from about Cairo, Illinois to below Memphis, Tennessee that is referred to by seismologists as the “New Madrid Seismic Zone.” It is an area that because of its unique geologic conditions, will probably produce a significant earthquake within the next 200 years. These geologic conditions include a layer of alluvial soil, composed of sand, clay and decayed organic material extending miles deep into the Mississippi River floodplain. This layer of alluvial soil is positioned directly on top of a portion of the earth’s crust that has a complex network of fault lines rather than just a single fault line. When this alluvial soil becomes excessively wet due to periodic floods and other causes, two things happen: it becomes heavy and it becomes “liquified,” similar to quicksand. This liquefaction increases subsurface pressure on the earth’s crust beneath it and at some point, a fracture in that network of faults can occur, resulting in an earthquake.
There have been four major earthquakes in the New Madrid Seismic Zone over the past two thousand years but we only have eyewitness accounts for the last one, which occurred during a three month period from December 1811 to February 1812, and which is collectively referred to as “the New Madrid Earthquakes.” (The name comes from the fact that this series of earthquakes occurred near New Madrid, Missouri.) Eyewitness accounts of the 1811-1812 earthquakes make these events seem diabolical. It is said that the earth opened up and ejected streams of sand, mud, carbon and sulfuric gases from deep fissures while at the same time, the earth seemed to be swallowing huge stands of forests and clay bluffs along the river. At one point just upstream of New Madrid, the Mississippi River briefly flowed in the opposite direction. There were three particularly intense quakes during this three month period (with those quakes being felt as far away as Michigan, New York, South Carolina and Louisiana) and over 2,000 minor quakes during this same period; aftershocks in the area continued for the next ten years. The reason these quakes were felt so far away is because unlike the typical California earthquake, the earth’s crust in the Mid-West and eastern US is dense and it does not easily fracture, so shifts and movement in this dense crust can be felt hundreds of miles away. If you are wondering why these quakes were not also felt in Texas, Colorado or South Dakota, remember this was 1811-1812; who’s to say they weren’t felt there as well? And the reason the aftershocks lasted over ten years in the New Madrid Seismic Zone is because the liquefaction of the alluvial soil located between the earth’s crust and the surface reacted as if it were a huge tub of jello, continuing to shake for years after the main event.
Obviously, the area around New Madrid in 1811 was not heavily populated so the damage from that series of major earthquakes —one of which was estimated to be a level 7.5– was relatively minimal, but experts predict that the next earthquake in the New Madrid Seismic Zone will result in a major economic disaster for the US. The Mississippi River could become impassible for years, the major highway network between the northern and southern portions of our country—such as Interstate 55– will be impacted, many energy sources, such as gas and electric supply lines, will be ruptured or otherwise destroyed, and unlike the California situation, buildings in the Mid-West (including many homes) could be destroyed because they typically are not designed to withstand earthquakes. All in all, it will be an extremely dangerous situation for folks in the Mid-West if and when that earthquake occurs.
Note: Because the earthquakes and aftershocks in the New Madrid area in 1811 and 1812 were so severe, church attendance increased significantly in areas up and down the Mississippi until the aftershocks stopped. Once the shaking stopped, some parishioners stopped attending church and subsequently became known as the “Earthquake Christians.”
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■ Bill Hoagland has practiced law in Alton for more than 50 years, but he has spent more than 70 years hunting, fishing and generally being in the great outdoors. His wife, Annie, shares his love of the outdoor life. Much of their spare time is spent on their farm in Calhoun County. Bill can be reached at [email protected].
