Fold mountains
Hi, Don and Jon–
I remember reading about those water gaps. I cannot find the article in
question at the moment, but it offered several theories about how they could
have been formed. One has the river establish its course on flattish land,
then uplift and differential weathering of folded layers creates new mountains,
with the river cutting whatever gets exposed in its path. There were other
theories that allow the river valleys to form while the mountains are present.
But none of the theories seemed entirely satisfactory – the article left me
with the feeling the origin of the water gaps has not been established with
confidence.
The Delaware River's cut through the mountains figured prominently as an
example.
–Doug