Yellowstone National Park, was established by the U.S. Congress as a national park on March 1, 1872, is located primarily in the U.S. state of Wyoming, though it also extends into Montana and Idaho. The park was the first of its kind, and is known for its wildlife and its many geothermal features, especially Old Faithful Geyser, one of the most popular areas in the park. It has many types of ecosystems, but the subalpine forest is dominant.

Yellowstone National Park spans an area of 3,468 square miles (8,983 km˛), comprising lakes, canyons, rivers and mountain ranges. Yellowstone Lake is one of the largest high-altitude lakes in North America and is centered over the Yellowstone Caldera, the largest supervolcano on the continent. The caldera is considered an active volcano; it has erupted with tremendous force several times in the last two million years. Half of the world's geothermal features are in Yellowstone, fueled by this ongoing volcanism. Lava flows and rocks from volcanic eruptions cover most of the land area of Yellowstone. The park is the centerpiece of the Greater Yellowstone Ecosystem, the largest remaining, nearly-intact ecosystem in the Earth's northern temperate zone.

The Yellowstone Caldera is the volcanic caldera in Yellowstone National Park in the United States. It is located in the northwest corner of Wyoming extending into portions of Montana and Idaho. The major features of the caldera measure about 55 kilometers (34 mi) by 72 kilometers (45 mi) as determined by geological field work conducted by Bob Christiansen of the United States Geological Survey in the 1960s and 1970s. After a BBC television science program coined the term supervolcano in 2000, it has often been referred to as the "Yellowstone supervolcano."

Yellowstone, like Hawaii, is believed to lie on top of an area called a hotspot where light, hot, molten mantle rock rises towards the surface. Yellowstone's hotspot, referred to as the Yellowstone hotspot by geologists, is now under and helped form the Yellowstone Plateau but was once under and helped create the eastern Snake River Plain through a series of volcanic eruptions. The hotspot's apparent motion is to the east-northeast. In reality, the North American Plate is moving west-southwest over the stationary hotspot deep underneath.

Studies and analysis may indicate that the greater hazard comes from hydrothermal activity which occurs independently of volcanic activity.

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Yellowstone National Park
Yellowstone Caldera

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