Monthly update of activity at Yellowstone Volcano for July 2021

During July, Yellowstone caught everyone’s attention with 1,000+ earthquakes located in seven distinct earthquake swarms. The largest swarm occurred beneath Yellowstone Lake and had 764 earthquakes, the largest of which was a Magnitude 3.6. While this seems like a lot of earthquakes, it is not the most Yellowstone has experienced in any given month and the volcano alert level remains unchanged.

The earthquake swarms are not caused by magma. The earthquakes occurred on existing faults, triggered by increased pore pressure from the extra groundwater that accumulated as the snow melted. One of the things we look at to see if magma was involved, is changes in ground deformation. We haven't seen any changes in ground deformation during the month of July that has been outside multi-year trends.

Yellowstone Volcano Observatory scientist-in-charge Mike Poland discusses activity in Yellowstone in this monthly update recorded near Solitary Geyser, within Yellowstone National Park.