Volcanic Hazards at INL
The potential for future volcanism and associated volcanic hazards at INL are a consequence of the volcanic history of the Snake River Plain. Eruptions of silicic (silica rich) and mafic (iron rich) magmas have occurred in the Snake River Plain as a result of the Yellowstone hotspot. Explosive silicic caldera eruptions began 16 million years ago in association with the hotspot’s initial position in southern Idaho. The hotspot is now located on the Yellowstone Plateau, which has had three major caldera eruptions over the last 2 million years. Within the hotspot track, mild effusive eruptions of mafic magmas that result from dike intrusion now cover much of the Snake River Plain. The most recent eruptions produced basalt lava flows 2,100 to 15,000 years ago at Craters of the Moon National Monument in the Great Rift volcanic rift zone.
Volcanic hazards at INL have been evaluated for possible hazard phenomena associated with the different types of silicic and mafic eruptions. Explosive silicic caldera eruptions similar to those that have occurred on the Yellowstone Plateau are considered to be negligible hazards for INL. Although, the potential for ash falls from Yellowstone and western U.S. volcanoes (e.g., the Cascades) have been evaluated. Three silicic domes located near INL's southern boundary erupted between about 300,000 and 1.2 million years ago. Due to their possible long repeat times and localized effects, their hazards are minimal. Dike intrusion has occurred as recently as 2,100 years ago in the Great Rift. Other basaltic lava flows near the southern INL boundary erupted about 5,000 and 13,000 years ago. As a result of the more recent periods of activity, INL facilities may be affected by hazards associated with future basalt volcanism (e.g., lava flows, ground deformation, and ash falls).