Wyoming Geography: Mountains, Plains, and Geothermal Wonders

Wyoming's geography is a dramatic meeting of Rocky Mountain terrain and Great Plains grassland — with the added geological drama of the Yellowstone supervolcano.

Physiographic Regions
Wyoming is divided among the Middle Rocky Mountains (western third), the Wyoming Basin (a broad intermontane plateau in the center), the High Plains (eastern third), and the Colorado Plateau (extreme southwest corner). The Wind River Range in the west-center is the backbone of the Rockies in Wyoming, stretching 100 miles with 40+ peaks above 13,000 feet.

Continental Divide
The Continental Divide runs through Wyoming from northwest to southeast — roughly from Yellowstone south through the Wind River Range and across the Great Divide Basin. The Great Divide Basin is hydrologically unusual: precipitation here drains neither to the Atlantic nor the Pacific, but into an internal basin that evaporates. The "Two Oceans Pass" in the northern Wind River Range is where Pacific Creek and Atlantic Creek drain to opposite oceans from a single watershed divide.

Yellowstone Plateau
The Yellowstone Caldera — one of the largest volcanic systems in the world — sits in the northwest corner of Wyoming. The caldera (45 × 30 miles) last erupted approximately 640,000 years ago. The magma chamber beneath it feeds the park's 10,000 geothermal features: geysers, hot springs, fumaroles, and mud pots. Old Faithful erupts approximately every 90 minutes; Grand Prismatic Spring (300 feet wide, 160 feet deep) is the largest hot spring in the US.

Rivers
The Snake River drains the Jackson Hole valley northwest to Idaho; the Green River flows south to the Colorado River; the Yellowstone River flows northeast to the Missouri; and the North Platte River flows southeast through Casper to Nebraska. Wyoming is the headwaters state for a significant portion of the Missouri-Mississippi drainage.

Climate
Wyoming's climate is semi-arid continental — cold winters, warm summers, low humidity, and significant wind. Cheyenne averages 300+ days of sun per year. The Wind River Basin around Lander and Riverton is Wyoming's warmest region; mountain valleys at 6,000–8,000 feet can experience frost in any month.