Wyoming
The Teton Range is one of the world’s most visually stunning mountain ranges, shooting higher than 7000 feet above the adjacent valley floor—from the sky, it appears as a range of jagged peaks running north and south, bordered by the Jackson Hole valley to the east.
The Tetons have the distinction of being the youngest mountain range in North America, yet they were formed from some of the oldest rocks on the continent. The most famous summit is the Grand Teton. As the biggest tooth in a very toothy range, the Grand Teton soars to an elevation of 13,775 feet. The Grand is so extreme in part because it is so young. Both the Grand Teton and the nine spiky peaks that make up the range, including Teewinot Mountain and Mount Moran, are only about 9 million years old—toddler age in geologic time—and they’re still growing taller.
The Tetons were thrust up as a result of extensional movement along the Teton Fault; both the mountain range and the Jackson Hole valley formed from tilted blocks of Earth’s crust. As the block that forms the Tetons continues to be uplifted, the block that underlies Jackson Hole is sinking. In the past 9 million years, the vertical displacement along the Teton Fault has grown to as much as 23,000 feet as the mountains rise and the valley sinks. Movement along the fault is rushing along at geologic warp speed of a foot every 300 years.
In contrast to the Tetons’ youthful age as mountains, the oldest rocks that make up the range began forming around 2.5 billion years ago, when this area of the world was covered by an ancient ocean. Extensive volcanism during this time added to the deep piles of seafloor sediments, and the mix was later buried and metamorphosed under intense heat and pressure to produce gneiss.
As the Teton Range keeps rising, the valley of Jackson Hole, on the east side of the range, keeps sinking.
Later episodes of volcanism forced magma up through cracks in the gneiss deep underground, creating granite intrusions, or dikes, that were exposed when the range was uplifted and eroded. This granite—harder than the gneiss—is as thin as a crack in some places and hundreds of feet thick in others. Dikes can be seen all over the Teton Range; the most famous is the black stripe on the east face of Mount Moran. Black Dike was formed 775 million years ago—long before the mountain was formed—when magma filled a vertical crack in existing rock that was 150 feet wide and more than seven miles thick. A portion of the dike remained when the uplift of the Tetons took place and can be seen today as a vertical streak on the summit spire. One of the classic technical climbing routes in the Tetons follows this dike to the summit of Mount Moran.
Mount Moran’s famous Black Dike can be seen as a thick, dark line descending from the summit on the left. It was formed when magma filled a vertical crack in existing rock, eons before the mountain was created.
The Tetons are so striking in part because of the way they rise right out of the valley, with no foothills at their base, evidence of dramatic fault movement.
You will be treated to a view of the spectacular Teton Range flying into Jackson, Wyoming.
