One can see the etiology of the New Madrid slip and the widening Seaway by looking at the underlying rock strata. The Keweenawan Rift is solid rock formed by hardened volcanic eruption eons ago. It curls around Wisconsin at the top and connects the point where the Seaway is ripping into Duluth, MN and fault lines in Kansas. The Keweenawan Rift lies alongside, parallel to, the Humboldt Fault.
ZetaTalk July, 2010