This takes me to the hard to explain uplift of the the remarkably stable plate region of the Colorado Plateau (you can read a lot of history in the walls of the Grand Canyon) and the Basin and Range Provence which both of which rose two or more kilometers in elivation. What would cause the Colorado Plateau to uplift so far after accumulating sediments and occasional volcanics for some 600 million years.
This article might lead to some answers and a lot more questions.
A rather rough map of the orogenies (Major plate stresses and mountain building in the borders of the continental USA.
I kind of like Dr.
Walt Brown’s hydroplane theory to explain the uplift and many other things.