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Map of most recent Yellowstone Caldera and its main thermal features. After the caldera formed, many vents erupted thick rhyolite lava flows, and the central part of the caldera was pushed upward to form resurgent domes. The star marks the magnitude 7.5 Hebger Lake earthquake.

Yellowstone Caldera, Yellowstone National Park, Wyoming. Yellowstone Caldera is one of the largest and most active calderas in the world. The spectacular geysers, boiling hot springs, and mud pots that have made Yellowstone famous--and even the strikingly beautiful Grand Canyon of Yellowstone through which the Yellowstone River plunges--owe their existence to the tremendous volcanic forces that have affected the region during the past 2 million years. Cataclysmic eruptions 2.0, 1.3, and 0.6 million years ago ejected huge volumes of rhyolite magma; each eruption formed a caldera and extensive layers of thick pyroclastic-flow deposits. The youngest caldera is an elliptical depression, nearly 80 kilometers long and 50 kilometers wide, that occupies much of Yellowstone National Park. The caldera is buried by several extensive rhyolite lava flows erupted between 75,000 and 150,000 years ago.

 Yellowstone Caldera

Maintained by John Watson
Updated 06.24.97

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