On February 7, 1812, a massive earthquake struck the area within the New Madrid Seismic Zone.  There was no Richter scale back then but the energy released was so intense that window panes in Boston were rattled.  The Reelfoot reverse fault drove the hanging wall upward tearing a fault scarp 20 feet high for more than 20 miles long.  The basin that formed on the foot wall eventually formed Reelfoot Lake.  The magnitude of the earthquake was probably equivalent to an 8.5 on the Richter scale.  Huge earthquakes in the interior of continents are rare so why did the seismic zone occur?  It appears to be related to rifting 750 million years ago when of the supercontinent of Rodina which generated the New Madrid Fault Zone. The zone was reactivated by the breakup of Pangaea about 500 million years ago.   The scarp has been eroded but it can still be seen here.