Teton Range and Jackson Hole

Geography and Topography

      The topography of Greater Yellowstone is the result of an underlying magmatic hot spot and millions of years of volcanic influence. The massif of high, moist plateaus, peaks, and valleys is surrounded by arid plains.

      The region contains the headwaters of many of the continent’s grandest waterways: two of the three forks of the Missouri; the headwaters of the Snake River, which flows into the Columbia and eventually into the Pacific Ocean; and the Yellowstone River, the United States’ longest free-flowing river, which runs north and drains approximately 70,000 square miles.

      The Continental Divide, the crest of the North American continent, zigzags across the southwest corner of Yellowstone. The region’s landforms channel westerly storm systems onto Yellowstone’s Central Plateau, where most of the park’s snow drops. The Tetons’ topographic extremes create their own semiarid microclimate, with most storms approaching from the southwest. Here, snowfall averages 190-plus inches, but annual rainfall hovers around just 10 inches.

      The majority of Yellowstone consists of broad volcanic plateaus scored by deep river canyons, with an average elevation of 8,000 feet. There are 370 miles of paved roads and more than 1,000 miles of maintained hiking trails. Yellowstone is covered 5% by water, 15% by grassland, and 80% by lodge-pole pine forest. The highest point is the seldom-scaled Eagle Peak (11,358 feet), near the park’s remote southeast corner. The lowest point is near the North Entrance at Reese Creek (5,282 feet), just north of the prominent Electric Peak (10,992 feet).

      Grand Teton’s centerpiece is the 40-mile-long Teton Range, an active fault-block mountain front. Twelve peaks exceeding 12,000 feet tower over the Snake River Plain and the valley known as Jackson Hole, which averages 6,800 feet in elevation and tilts subtly southward toward the gateway town of Jackson. In addition to the string of morainal piedmont lakes at the base of the range, the park is home to more than 100 alluring tarns (steep-banked glacial lakes). In Yellowstone, more than 600 lakes and ponds cover approximately 107,000 surface acres, 94% of which can be attributed to Yellowstone, Lewis, Shoshone, and Heart Lakes. Some 1,000 rivers and streams account for more than 2,000 miles of running water.

Geology and Hydrothermal Activity

      Glaciers and supervolcanoes are the primary influences in Greater Yellowstone’s dynamic landscape. In the past 2.1 million years, three cataclysmic eruptions have rocked the region. The most recent massive volcanic explosion, which occurred around 640,000 years ago, created the gigantic Yellowstone Caldera, a vast, collapsed crater that defines the park’s Central Plateau.

      Since 2001, the Yellowstone Volcano Observatory has tracked the uplift of the dome beneath Yellowstone Lake resulting from the pressure exerted by superplumes of near-surface magma in what it calls the “largest volcanic system in North America.” Multiple earthquakes are registered daily, but a swarm of 400 temblors centered in the park’s northwest sector in 2004 sparked renewed speculation about the possibility of another gigantic volcanic event and the possible resulting global climate disruption. Volcanologists downplay the possibility of such an event in our lifetime. However, some say its likelihood is 5 to 10 times greater than that of a globally destructive asteroid impact.