Monthly update of activity at Yellowstone Volcano, March 1, 2023

Could an external event trigger a Yellowstone eruption? No, says Yellowstone Volcano Observatory’s scientist-in-charge Mike Poland, that’s not how volcanoes work. Most of the pressure that drives a volcano toward eruption comes from within, from the exsolution of gases in the magmatic system. External events, like large earthquakes or nuclear blasts, can't cause that.

This question arose in 2019 after the magnitude 7.1 Ridgecrest earthquake in eastern California, and again in March 2020 with a magnitude 6.5 in central Idaho. More recently, YVO has been asked if a nuclear blast could trigger a Yellowstone eruption.

Consider Yellowstone's history. The last lava flow eruption was 70,000 years ago, and there have been hundreds to thousands of magnitude 7, 8, and 9 earthquakes in the western U.S. since that time without triggering an eruption. The last big explosion was 631,000 years ago, and again, there have been thousands of very large earthquakes in the western U.S. since that time, none of which triggered eruptions. And perhaps the greatest evidence is the magnitude 7.3 that occurred just west of the park near Hebgen Lake. The earthquake occurred several miles deep, essentially right next to the magma chamber, and it released the same amount of energy as a moderate-sized nuclear weapon. Nothing happened regarding Yellowstone's eruptive activity, although the shaking did cause many geysers to change their behavior.

Distant earthquakes, local earthquakes, and nuclear blasts would all be devastating events but would not trigger Yellowstone to erupt.

During the month of February 2023:

• The University of Utah Seismograph Stations, which monitors and operates the Yellowstone seismic network located 168 earthquakes. The largest was a magnitude 2.9.

• Deformation trends continue, with overall subsidence of about two to three centimeters (about an inch) per year, and very little deformation in the Norris Geyser Basin.

• There were no recorded Steamboat Geyser eruptions.

Yellowstone Volcano remains at normal, background levels of activity.

For questions, email yvowebteam@usgs.gov