Here's why:

* Faulting: The Tetons were formed by the uplift of a large block of Earth's crust along a normal fault. This fault is a steep break in the rock where one side has moved downward relative to the other.

* Tilting: The uplifted block tilted eastward, creating the steep, westward-facing slopes of the Teton peaks and the gentler eastern slopes.

* Erosion: Over millions of years, erosion has shaped the mountains into their current form, carving out valleys and canyons.

The Tetons are a spectacular example of how tectonic forces can create dramatic landscapes. The dramatic vertical relief and the sharp, angular peaks are hallmarks of fault-block mountains.