Yellowstone Caldera

The Yellowstone Caldera, also known as the Yellowstone Plateau Volcanic Field, is a Quaternary volcanic field, caldera complex, and volcanic plateau spanning parts of Wyoming, Idaho, and Montana. It is driven by the Yellowstone hotspot and lies largely within Yellowstone National Park. The field comprises several overlapping caldera structures, multiple lava domes and resurgent domes, and numerous bimodal lavas and tuffs of basaltic and rhyolitic composition, originally covering about 17,000 km2 (6,600 mi2). Volcanism began 2.15 million years ago and proceeded through three major volcanic cycles. Each cycle involved a large ignimbrite eruption, widespread pyroclastic flows and ash fall, and caldera collapse, preceded and followed by smaller lava flows and tuffs. The climactic eruption of the first and largest cycle produced the Huckleberry Ridge Tuff about 2.08 million years ago and formed the first-cycle caldera complex. The second cycle culminated in eruption of the Mesa Falls Tuff and formation of the Henry's Fork Caldera about 1.3 million years ago. The most recent supereruption, about 631,000 years ago, produced the Lava Creek Tuff and created the present Yellowstone Caldera. Post-caldera eruptions included basalt flows, rhyolite domes and flows, and minor explosive deposits, with the last known magmatic eruption about 70,000 years ago. Large hydrothermal explosions also occurred during the Holocene. The volcanic field remains active, with continuing earthquakes, ground deformation, and extensive hydrothermal activity driven by heat from the underlying magmatic system. The Yellowstone Volcano Observatory monitors the region and does not consider an eruption imminent. Imaging of the magmatic system indicates a substantial volume of partial melt beneath Yellowstone, although it is not presently considered eruptible.