CompuServe Messages

Hi, Ed– I guess (a) does not work alone until everything is worn nearly flat, then keeps on wearing. The Appalachians would be too young(!) for it. But if an anticline is buried in flat land, the tough layer may be exposed as a hill, then wear through to a weak layer, then the weak layers on top of and under it would wear away faster, leaving the tough layer as a pair of ridges facing each other. I suppose that is what I saw northwest of the Grand Canyon from my airliner (a pair of ridges forming a long straight line on an otherwise flat and featureless section of the Colorado Plateau(?)). If your (c) undercutting is a big factor, the tough top layer might fall into a hole in the center and it would look somewhat like a fault block situation on the surface (except I guess the top layer would typically fall as rubble instead of a block). But as long as the undercutting is only a contributing factor, I figure these center-cut folds should be "easily" distinguished from fault block mountains because the top layer would be different between the outside flank of the ridges and the lower center area. –Doug