CompuServe Messages

Kamron, >> If the east and west sides of the App. Mts. were different sections of crust it would go 15 miles deep or more..I would expect to see remnants of the crack…and how did they get welded together so well? << They are, and it does. The reason we don't see any direct evidence of the old subduction zones below the Appalachians is that in the Alleghenian orogeny, rock from the east and southeast was thrust-faulted for dozens of kilometers inland, over the old subduction zones. What wasn't buried that way has been buried since, by renewed sedimentary deposition. The "welding" was not particularly good; it was actually very clumsy and ugly, which is why it was an orogenic event. I'm not sure, but I think the faults in the Appalachians and along the East Coast date from the Acadian and Alleghenian orogenies, and the fact that some of those faults are still active after two hundred million years indicates how rough the suturing was. Jon W.