Summary of Eruption History
The Yellowstone Plateau volcanic field developed through three volcanic cycles spanning over two million years and including two of the world's largest known eruptions. The >2450 km3 (588 mi3) Huckleberry Ridge Tuff erupted about 2.1 million years ago, creating a large, approximately 75 km (47 mi) wide, caldera and thick volcanic deposits. A second cycle concluded with the eruption of the much smaller Mesa Falls Tuff around 1.3 million years ago. Activity subsequently shifted to the present Yellowstone Plateau and culminated 640,000 years ago with the eruption of the >10003 km (240 mi3) Lava Creek Tuff and consequent formation of the 45 x 85 km (28 x 53 mi) caldera. Large volumes of rhyolitic lava flows (approximately 600 km3 (144 mi3) were erupted in the caldera between 180,000 and 70,000 years ago, distributed primarily along two north-south alignments of vents. No magmatic eruptions have occurred since then, but large hydrothermal explosions have taken place during the Holocene, including near Yellowstone Lake. Uplift and subsidence of the ground surface is centered on two uplifted regions (the Mallard Lake and Sour Creek resurgent domes). Yellowstone is presently the site of one of the world's largest hydrothermal systems including Earth's largest concentration of geysers.