Early navajo dating
Under great confining pressures, or at depths where temperatures reach a significant fraction of their melting points (typically 10-15 km), rocks that are quite brittle at the surface become sufficiently plastic to deform without fracture at rates comparable to the rate at which fingernails grow (~10 mm/yr).
Granted, that makes molasses look downright mercurial, but then relative viscosity is the whole idea here.
Colorado's generous endowments of accessible mineral wealth and fertile farmland were not inevitable birthrights. This overview ventures a "to the best of our knowledge" summary of Colorado geologic evolution current as of late 2004.
Colorado's story still includes many gaps and controversies, often around events and structures shrouded in deep time, deep earth or both.
Over a few Ma, fingernail speed is plenty fast enough to fold great thicknesses of sedimentary rock over the east edge of the relatively brittle Front Range basement block, as in the photo at right.
The geology is in turn inextricably entwined with Colorado's human history.
That's true everywhere, of course, but it goes double here.
Over 50 Ma, an entire mountain range like the Ancestral Rockies can rise up and vanish.
The pink feldspar bands in the severely deformed metamorphic rock at right (a mylonite from the Homestake Shear Zone in the northern Sawatch Range) show the kind of internal folding you'd expect from warm taffy, but this rock didn't actually melt.