A mountain range once separated the continental interior of the U.S. from the Gulf of Mexico. Some clever geologic sleuthing has revealed how that barrier was breached, allowing the river to reach the Gulf... [S]omehow the once continuous Ouachita-Appalachian range was cleaved in two, leaving room for the Mississippi River to flow into the Gulf of Mexico. The explanation for the split, which the two of us have been investigating for most of the past decade, touches on many other mysteries of North American geology, too -- such as why you can find diamonds in Arkansas and why the largest...