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How many giant eruptions have occurred in the Yellowstone National Park region and how large were they?

Volcanic activity began in the Yellowstone National Park region a little before about 2 million years ago. Molten rock (magma) rising from deep within the Earth produced three cataclysmic eruptions. The first caldera-forming eruption occurred about 2.1 million years ago. The eruptive blast removed so much magma from its subsurface storage reservoir that the ground above it collapsed into the magma chamber and left a gigantic depression in the ground- a hole larger than the state of Rhode Island. The huge crater, known as a caldera, measured as much as 80 kilometers long, 65 kilometers wide, and hundreds of meters deep, extending from outside of Yellowstone National Park into the central area of the Park (Figure 1).

Later, activity shifted to a smaller region within the Island Park area of eastern Idaho, just southwest of Yellowstone National Park, and produced another large caldera-forming eruption 1.3 million years ago. Subsequent activity has been focused within the area of the National Park, and another huge eruption 640,000 years ago formed the Yellowstone caldera as we now see it.

The three caldera-forming eruptions, respectively, were about 2,500, 280, and 1,000 times larger than the May 18, 1980 eruption of Mt. St. Helens in Washington State. Together, the three catastrophic eruptions expelled enough ash and lava to fill the Grand Canyon.

In addition to the three climactic eruptions, activity associated with each of the three caldera cycles produced dozens or even hundreds of smaller eruptions that produced both lava and pyroclastic materials.

Tags: Geothermal Resources, Earthquakes, Tectonics, Monitoring, Volcanoes, Lava, Seismicity, Ring of Fire