Yellowstone

Summary

The >2450 km³ (588 mi³) Huckleberry Ridge Tuff erupted about 2.1 million years ago, creating an approximately 75 km (47 mi) wide caldera and thick volcanic deposits. A second eruption cycle concluded with 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 >1000³km (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 from within and near Yellowstone Lake. Uplift and subsidence of the ground surface is centered on two uplifted regions (the Mallard Lake and Sour Creek resurgent domes). Large earthquakes occur just off the plateau along the nearby Teton and Hebgen Lake faults, the latter of which ruptured in 1959 (Ms = 7.5), causing considerable damage to the region. Yellowstone is presently the site of one of the world's largest hydrothermal systems including Earth's largest concentration of geysers.