Any mountain range is the product of the struggle between uplift and erosion, but in few places are the results as clear as on the crest of the Teton Range. Today we do not first see the Teton peaks across 160 kilometers (100 miles) of wilderness and then struggle to them afoot, on horseback, or by wagon. This spectacle may break upon us from the window of an airplane, or appear around a bend in the John D. Rockefeller, Jr. Memorial Parkway. The telescoping of time does not lessen the impact however. The range’s nearly even east base (see painting) is the best place from which to grasp its formation. Along this line the valley ends at an abrupt wall, with no foothills at the mountain’s base. These are sure signs of faulting, the elevation of a mountain block along a deep crack in the Earth’s crust. (See diagram.) Shatter lines visible in many of the naked rock peaks show that the uplift was no smooth ride. The Tetons are very young mountains composed of very old rock. The range was thrust up about 9 million years ago. Young? Yes, when compared to the main Rocky Mountains, which rose 60 million years ago, and the Great Smoky Mountains, which have been above water more than 200 million years. The Teton Range’s crystalline rock is comparable to the 3-billion-year-old Allegheny Mountains core. This hard, stable rock, more than 300 times older than the mountains it forms, is a boon to climbers. Another unusual feature of the Teton Range is its divide, the division line at which water will flow off the mountains either west into the Teton River or east into the Snake. The Teton’s divide lies well below and to the west of the highest elevation. This is because the steeper east face caused water to flow off faster and thereby to cut deeper. These streams carved into the range and captured headwaters from less erosive western streams. Erosion and uplift continue competing in the range, which still rises through periodic earthquake activity. 1. Mount Wister 2. Shadow Peak 3. South Teton 4. Cloudveil Dome 5. Nez Perce Peak 6. Middle Teton 7. Mount Owen 8. Teewinot Mountain 9. Rockchuck Peak 10. Mount St. John 11. The Jaw 12. Mount Woodring 13. Maidenform Peak 14. Mount Moran 15. Window Peak 16. Bivouac Peak Forming and Shaping the Mountains [Illustration: Uplift, erosion, and glaciation formed and shaped the Teton Range. Ice Age glaciers profoundly sculpted the horn-shaped peaks and gouged out the U-shaped valleys (photo and diagram). The present mountain glaciers were formed only 500 to 1,000 years ago.]