The Yellowstone Plateau Volcanic Field is a vast volcanic system centered mostly in Wyoming, with parts in Idaho and Montana, and much of it lies within Yellowstone National Park. Forming over about 2 million years, it has produced more than 110 eruptions and over 6,000 cubic kilometers of mostly rhyolitic material. Geologists have identified three especially large caldera-forming eruptions: the Huckleberry Ridge eruption about 2.08 million years ago, the Henrys Fork eruption about 1.3 million years ago, and the Yellowstone Caldera eruption about 0.6 million years ago. Continued magma upwelling, lava flows, and hydrothermal activity make it scientifically important, closely monitored, and home to the world’s greatest concentration of hydrothermal features.