An ancient rift awakens
Between December 1811 and February 1812, the central United States was struck by three of the most powerful earthquakes in the nation's recorded history. The main shocks occurred on December 16, 1811, January 23, 1812, and February 7, 1812. Modern estimates place their magnitudes between 7.2 and 8.2. The shaking was felt over an area of approximately 5 million square kilometers, with reports of church bells ringing in Boston and clocks stopping in Washington, D.C. The area of strong shaking was about 10 times larger than that of the 1906 San Francisco earthquake, due to the older and more rigid crust of the continental interior, which transmits seismic energy with great efficiency.
The effects on the landscape were immediate and severe. The ground rose and fell in visible waves, creating fissures and triggering massive landslides. An area of 5,000 square miles was visibly scarred by uplift, subsidence, and soil liquefaction. This last phenomenon, where saturated soil behaves like a liquid, caused huge jets of sand and water to erupt from the ground, creating features called "sand blows" that are still visible today. The February 7th quake, centered near the town of New Madrid, Missouri, caused sections of the Mississippi River's banks to collapse and uplifted the riverbed, forcing the water to flow backward for a period of several hours. This event also dammed the Reelfoot River and flooded the surrounding forest, creating the 18,000-acre Reelfoot Lake in Tennessee.