Most mountains in Wyoming were elevated about 60 million years ago, which is quite recent by geologic standards, since the oldest rocks in the cores of these mountains are about 2.8 billion years old.
Stage 3: Basins filled to overflowing at low places on divides, followed by regional uplift
with titling and faulting. Present master streams developed on rejuvenated surfaces.
(Click image above to enlarge.)
The Tetons, which rise with spectacular grandeur from the floor of Jackson Hole, are a medium-sized but unique mountain range. The bold east front, which stands above the glacial lakes at the base, resulted from intermittent but major movement of more than 20,000 feet on a steeply inclined fracture plane that slopes to the east. The rugged mountain peaks have been carved from the elevated segment of the crust. Glacial processes have produced the matterhorns and U-shaped valleys that are the characteristic landforms.
The Tetons are extremely young by geologic standards, having attained their height less than 10 million years ago. This fact places them among the youngest ranges in the Rocky Mountains. Numerous minor earthquakes within historic time in Jackson Hole attest to the fact that these mountains may still be growing.