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200 years since massive quakes
To the editor:
Friday, Dec. 16, 2011, marked the 200th anniversary of the beginning of the greatest geological events ever to occur in recorded North American History. In the two o'clock hour of the moonless morning of Dec. 16, 1811, the great hardwood forests and rich bottom lands of what would someday become Blytheville, Ark., began to shake violently ... the first and largest volley of a seven week series of events known as the New Madrid Earthquakes of 1811/12.
That first earthquake in the early morning of Dec. 16, what some geologists believe may have reached as high as 9.0 on the Richter Scale, though the consensus estimate from the USGS is 7.7, was centered in the Eaker Field (Aeroplex) area of Blytheville. It was followed later that same morning by second quake, a large aftershock estimated as a 7.0 magnitude, also center at Blytheville.
For the next two months, the earth's crust continued to shift, almost constantly, including two more major earthquakes ... an estimated 7.5 temblor center further north in the Missouri Bootheel on Jan. 23, 1812, and the final major earthquake of the series, an estimated 7.7 magnitude on Feb. 7, 1812, centered near New Madrid, Mo.
By comparison, the Great Alaskan Earthquake of 1964 measured 9.2 on the Richter Scale and the 1906 San Francisco Earthquake at an estimated magnitude of 7.7.
The Richter Scale, developed by Charles Richter at Cal Tech in 1935, measures on a base-10 logarithmic scale; for example, a magnitude 8.0 earthquake releases10 times more energy than a 7.0 earthquake.
The 1811-12 earthquakes received the New Madrid name because New Madrid was the only notable landmark in the area of the quakes at the time. Interestingly, if Blytheville existed in 1811, the series of earthquakes would probably be known today as the Blytheville Earthquakes of 1811/12.
Although the area was lightly populated at the time, eyewitnesses told stories of the Mississippi River being coated with thick oil, while other accounts said the Mississippi flowed northward for several days.
Some of the geological landmarks of the the local area resulted from the New Madrid Earthquakes. The formation of Big Lake west of Blytheville (before the quake Big Lake was a free flowing part of the Mississippi River system) and Reelfoot Lake across the river in northwest Tennessee (said to be filled by the backward flowing Mississippi River) had their origins in the great earthquakes. Before the earthquakes, the Mississippi River meandered much closer to Blytheville to the area between present day Blytheville and Armorel. Crowley's Ridge and the Saint Francis River Valley can also trace their advent to the historic seismic activity of the fault zone.
Although predicting earthquakes in the New Madrid Fault Zone and Blytheville Arch Zone remains difficult, even more so than predicting earthquakes along the plate boundary type faults of California, an event like 1811/12 could occur again. Geological history indicates there have been major earth movement along a line extending south from Blytheville to Marked Tree and north to New Madrid about every 500 years going back to the time of Moses and likely even further.