USGS Volcano Notice - DOI-USGS-YVO-2025-10-01T16:31:47+00:00

Summary

Yellowstone Caldera activity remains at background levels, with 87 located earthquakes in September (largest = M3.3). Deformation measurements indicate that the annual summertime pause in long-term caldera subsidence started in late May.

Recent Work and News

Minor eruptions of Steamboat Geyser in Norris Geyser Basin remain sporadic, indicating that a major eruption is unlikely anytime soon.  There have only been 2 major eruptions of the geyser so far during 2025, and the period of frequent activity that started in 2018 is probably ending.  Valentine and Guardian Geysers in Norris Geyser Basin have been erupting intermittently since August, the former for the first time in more than 20 years.  In late September a new steam vent opened in the Mud Volcano area in a location of numerous past venting episodes.

During the past month, field engineers from EarthScope Consortium performed maintenance and upgrades on several continuous GPS stations in the park.  USGS staff recovered temporary GPS deployments and swapped batteries at temperature monitoring stations, and they also conducted a microgravity survey in the Norris, Old Faithful, and Hayden Valley areas.

Seismicity

During September 2025, the University of Utah Seismograph Stations, responsible for the operation and analysis of the Yellowstone Seismic Network, located 87 earthquakes in the Yellowstone National Park region. The largest event of the month was a minor earthquake of magnitude 3.3 located about 14 miles south-southwest of Mammoth Hot Springs in Yellowstone National Park on September 28 at 1:29 a.m. MDT.

September seismicity in Yellowstone was marked by one swarm of 16 earthquakes that occurred approximately 14 miles south-southwest of Mammoth Hot Springs during September 27–29. The swarm was a culmination of mild ongoing seismicity in the area throughout September. The largest swarm event is also the largest event in September, described above.

Yellowstone earthquake activity remains at background levels.

Ground Deformation

Continuous GPS stations in Yellowstone Caldera continue to record the annual summertime pause in subsidence or transition to slight uplift, which is caused by seasonal changes related to snowmelt and groundwater conditions.  Since late May, the caldera has risen by about 1.5 cm (roughly half an inch), which is superimposed on the overall trend of subsidence that has been ongoing since 2015–2016.  Deformation in the area of Norris Geyser Basin also recorded the seasonal uplift, but with no overall changes during the past several years.

An example of GPS data can be found at http://www.unavco.org/instrumentation/networks/status/pbo/data/NRWY (click on Static Plots / Cleaned)