These two world-famous parks are surrounded by a buffer zone consisting of six national forests, six wilderness areas, three national wildlife refuges, 125,000 acres of Bureau of Land Management rangeland, and more than 1 million acres of private property and tribal lands.
All told, this vast complex of wild lands encompasses 28,000 square miles, about the size of West Virginia. Yellowstone alone protects 2.22 million acres (3,468 square miles), roughly the same size as Puerto Rico, or Delaware and Rhode Island combined. In contrast, Grand Teton’s wilderness punch is concentrated in a mere 311,000 acres.
To give you a better idea of just how big the region is, Yellowstone’s seasonal Thorofare patrol cabin in the park’s bottom right corner is around 30 trail miles from the nearest road—a long day’s horseback ride—making it the most remote inhabited wilderness outpost and the farthest spot from a road in the Lower 48.
Long-range planning for holistic management of the buffer zone, home to a rapidly growing human population of well over 200,000 residents, is increasingly seen as the key to preserving this unique region, which is often described as “Island Yellowstone” or “an island of mountains in the high, dry plains.”
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.
Boardwalks provide close access to many frontcountry hot springs.
Also related to the hot spot are Yellowstone’s unique, super-heated hydrothermal features. A recent inventory conducted by the Yellowstone Center for Resources estimates that the park is home to more than 18,000 distinct geothermal features. The most common surface expressions of the park’s extensive subterranean plumbing network are hot springs, where colorful thermophiles (heat-loving microorganisms, also known as extremophiles) and cyanobacteria (single-celled photosynthetic bacteria) thrive in pools of geothermally heated water. These springs are often linked to geysers (from the Icelandic word geysir, which means “to gush or rage”), where highly pressurized water rockets toward the surface and often flashes to steam. Fumaroles are dry, hissing vents that issue hydrogen sulfide (the source of that “rotten egg” odor), hydrochloric acid, and other gases. A solfatara is a sulfur-emitting fumarole. Mud pots (also known as paint pots when tinted by minerals) form in thermal areas where precipitation mixes with fine volcanic soils to create a bubbling, viscous—and often very acidic—slurry, sometimes forming mud volcanoes.
For hikers, this ancient ice sculpting and geothermal hyperactivity translates into many unusual geologic features to explore, including multilayered fossil forests, lava flows, dramatic U-shaped canyons, glacial boulder fields, and black mountains of obsidian. These varied and dramatic landscapes form numerous ecological niches that support an amazing diversity of wildlife and plants, many of them reachable only on foot.
Flora
Some 1,100 native species of flowering plants are found in Yellowstone alone, but only three species are endemic: the Yellowstone sand verbena, the Yellowstone sulfur wild buckwheat, and Ross’s bentgrass. There are more than 200 nonnative species, some of which are starting to invade the backcountry. An additional 600 species of fungi, lichens, mosses, and liverworts have been cataloged. It’s legal to collect small quantities of edible plants and berries for personal consumption, but keep it to a minimum to maintain your good bear karma.
Elevation has the most influence over which plant species flourish where. Though the vegetation varies significantly throughout the ecosystem, it’s mostly typical of the Rocky Mountains. The observant hiker may notice elements of seven distinct biomes from the surrounding deserts, plains, montane forests, and arctic tundra.
Thanks to their shallow root systems, vast tracts of drought-tolerant lodge-pole pines dominate the nutrient-poor, volcanic soils within the Yellowstone Caldera. In sharp contrast, the clayey glacial lake beds beyond the caldera encourage a much more diverse flora.
Botanists group Rocky Mountain vegetation into five zones: foothills, riparian, montane, subalpine, and alpine. These zones overlap considerably and are not strictly defined. The altitude and width of each zone increase progressively as you move from north to south. Fall colors peak around the autumnal equinox (third week in September) in the Tetons, a bit later on Yellowstone’s relatively low-lying Northern Range.
Most of Yellowstone’s lower-elevation hikes begin in sagebrush-blanketed foothills (5,500–6,500 feet). A prime example of this type of habitat