Nostradamus was refering to the rebirth of the volcano under the great lakes.The rending apart of faults running from Montana thru N.dak,,Mn and Wisc and points further east.During his time it is unlikely anyone knew anything much about tektonics and North americas geological past.But he was interested in the future,or given a vision of it! The bi products of that long ago event include gorgeous Lake Superior agates and diamonds strewn along the path of passing glaciers.No doubt such an event would be a major disaster!But one that has happened before in precambrian times and could happen again.