A new technical paper in Nature argues that warming of the lithosphere is a "powerful mechanism" for driving uplift of the Colorado Plateau.
Mousumi et al, say that "warming of the thicker, more iron-depleted Colorado Plateau lithosphere over 35–40 Myr following mid-Cenozoic removal of the Farallon plate from beneath North America, is the primary mechanism driving rock uplift." [right, Middle Tertiary (Early Miocene) Paleogeography, Southwestern US (20 Ma), from Ron Blakey's NAU site].
Ref: Mousumi Roy, Thomas H. Jordan, Joel Pederson, Colorado Plateau magmatism and uplift by warming of heterogeneous lithosphere, Nature 459, 978-982 (18 June 2009) doi:10.1038/nature08052 Letter