Yellowstone National Park is the centerpiece of the Greater Yellowstone Ecosystem - the largest remaining nearly-intact ecosystem in the Earth's northern temperate zone. Comprised of lakes, canyons, rivers, and mountain ranges, the park spans an area of 3,468.4 square miles.
Yellowstone Lake is one of the largest high-elevation lakes in North America and is centered over the Yellowstone Caldera, the largest supervolcano on the continent. This caldera is considered an active volcano and has erupted with tremendous force several times in the last two million years. Fueled by this ongoing volcanism, half of the world's geothermal features are in Yellowstone. Lava flows and rocks from volcanic eruptions cover most of the land area of Yellowstone.
Hundreds of species of mammals, birds, fish, and reptiles have been documented in Yellowstone, including several that are either endangered or threatened. Grizzly bears, wolves, and free-ranging herds of bison and elk live in the park. The Yellowstone National Park bison herd is the oldest and largest public bison herd in the United States.
Yellowstone National Park is the largest and most famous megafauna location in the contiguous United States. The park's vast forests and grasslands include unique species of plants. A necessary part of Yellowstone's landscape, forest fires occur in the park every year. In 1988, nearly one third of the park burned and regenerated the landscape.
In summer, Yellowstone has numerous recreational opportunities including hiking, camping, boating, fishing and sightseeing. Paved roads provide close access to the major geothermal areas as well as some of the lakes and waterfalls. During winter, visitors can access the park by way of guided snowcoach and snowmobile tours.