The University of Utah Seismograph Stations operates the Yellowstone Seismic Network which monitors the Yellowstone region of earthquake activity and reports earthquakes that occur to the public in real time. Yellowstone offers a dual threat to the public including the threat of a large earthquake with the additional threat of volcanic activity.
Yellowstone’s Earthquake Threat
Yellowstone has experienced the largest historical earthquake in the Intermountain West in the 1959 MW7.3 Hebgen Lake earthquake. This event occurred on August 17, 1959 just west of Yellowstone National Park in the Madison Canyon. The earthquake ruptured the Hebgen Lake and Red Canyon faults and produced fault scarps as high as 6.7 m (22 ft) (Smith et al., 2000). In total, 28 people died in the earthquake, 19 of those were permanently buried beneath the Madison Canyon Landslide, which was triggered above the Rock Creek Campground by the intense shaking. Rocks and landslides tumbled into Yellowstone National Park highways in several places, blocking roads between Old Faithful and Mammoth closing the route to the park’s west entrance at West Yellowstone, Montana (Smith et al., 2000). In addition, there was damage to numerous buildings throughout the park including the historic Old Faithful Inn where the indoor chimney collapsed into the dining room.
On average, The University of Utah seismograph stations locates ~1,500 – 2,000 earthquakes per year in the Yellowstone region. The majority of these events are too small to be felt by residents and visitors to the region.
Yellowstone’s Volcanic Threat
There have been three major caldera-forming eruptions in the Yellowstone region in the last 2.1 million years. The first of three major eruptions in the Yellowstone area occurred 2.1 million years ago and erupted 2,500 km3 (600 mi3) of material depositing the Lava Creek Tuff. There was a second major eruption in Yellowstone 1.3 million years ago with 280 km3 (67 mi3) of material erupted forming the Mesa Falls Tuff. The last major eruption of the Yellowstone volcano occurred 640,000 years ago erupting 1,000 km3 (240 mi3) of material depositing the Huckleberry Ridge Tuff and forming the Yellowstone caldera. In comparison, the 1980 eruption of Mt. St. Helens erupted a total of 1 km3 (0.24 mi3) of material.
Since the last major eruption of the Yellowstone volcano, there have been numerous smaller eruptions that have emitted rhyolite lava that has subsequently filled in most of the Yellowstone caldera. The youngest of these flows is the Pitchstone Plateau flow that occurred 70,000 years ago.
In addition to volcanic eruptions, there are other volcano related threats in Yellowstone including hydrothermal explosions. Yellowstone has a history of some of the worlds largest hydrothermal explosions. Large hydrothermal explosions (>100 m [~330 ft] in diameter) in Yellowstone have occurred over the past 16,000 years averaging ~1 every 700 years; similar events are likely in the future (Morgan et al., 2009). These events pose a risk to park visitors and structures.