Another geophysical anomaly is the earthquake zone around Missouri/Illinois/Kentucky where the monstrous series of earthquakes happened in 1811-12 known as New Madrid. This area is nowhere near a coast either. Of course the Tethys Sea once covered that area, but how many million years ago was that?
Historical geology ping....
More readin’ up for me.
Yep, I’m living on the New Madrid fault. It’s almost as if North America decided to split like Africa is at the Great Rift and then changed its mind.
The New Madred earthquake activity is associated with a really ancient fault (600+ million).
As the story goes, a pre-Pangea supercontinent known as Rhodinia split apart about that time and spreading later ceased there.
When large land masses break apart they do so along a 3-prong set of faults. Ultimately one of the three spreading centers ‘fails’ and the spreading continues along the other two.
This process is going on currently in the region around the Great Rift Valley in northeast Africa. The other two arms of the 3-prong system are the Red Sea and, I think, Gulf of Aden (spelling?).