Yellowstone Caldera Chronicles is a weekly column written by scientists and collaborators of the Yellowstone Volcano Observatory. This week’s contribution is from Michael Poland, geophysicist with the U.S. Geological Survey and Scientist-in-Charge of the Yellowstone Volcano Observatory.
Four radar interferograms (InSAR data) showing surface movement near Norris Geyser Basin in Yellowstone National Park during 1996 to 2003. A color change from violet to blue to green to yellow to red, shown in the color bar in A, marks an increase in the distance from the satellite to points on the ground (mostly subsidence) of 28.3 mm (1.1 inch), and vice versa. White dots represent epicenters of earthquakes recorded during the time interval spanned by each interferogram. Black parallel dashes outline caldera rim.
Yellowstone is a dynamic geologic system—the one constant is change. This is demonstrated daily by hydrothermal activity manifested in geysers, hot springs, mud pots, and other thermal features, but even the ground itself moves!
Surface movement, called deformation, in Yellowstone varies tremendously. Over the past century, both uplift and subsidence have occurred, sometimes alternating on an annual basis. These changes can be driven by a variety of processes, like fault motion, accumulation or withdrawal of magma or hydrothermal fluids, and even cooling and contraction of subsurface fluids.
During 1996–2004, an area along the north caldera rim, just south of Norris Geyser Basin, uplifted by a total of about 12 centimeters (almost 5 inches). This deformation came to be known as the Norris Uplift Anomaly (NUA), and it was thought to be a result of accumulation of magma 14 kilometers (almost 9 miles) beneath the surface. This sort of activity is probably quite common, but it is only thanks to the technological innovations and expanded monitoring networks of the past few decades that such minor changes can be detected.
The area of the NUA subsided by about 7 centimeters (about 3 inches) for a few years after 2004, and deformation in the area was mostly flat for a decade. Then, during 2013-2020, the ground closer to Norris Geyser Basin began to alternate between uplift and subsidence, this time due to shallow accumulation and release of water. It is possible that the water came from the magma associated with the NUA, given that water and gases are dissolved in magma and can be released as the magma rises. No significant changes occurred after 2020, with the possible exception of about 1 cm of uplift and subsequent subsidence of the NUA area during 2020-2022.
(Cue the deep-voiced narrator): Until now.
In July 2025, continuous GPS stations on the northwest side of Yellowstone caldera began moving away from the area of the NUA. The change in surface displacement patterns, however, occurred at about the same time as the seasonal patterns that happen every year, so the results were initially ambiguous.
Map of horizontal velocities between July and December 2025 at Global Positioning System (GPS) stations P711 and NRWY (arrows and yellow circles; arrow length gives displacement rate) in the area between Norris Geyser Basin and Madison Junction. Dashed black line indicates boundary of Yellowstone Caldera and gray lines are roads. White circle is approximate center of uplift that became active in July 2025. Red circles are earthquakes located during 2024-2025 (circle size scales with magnitude). Top right plot shows distance change between GPS sites P711 and NRWY, which span the uplifting area. Positive change indicates extension, which is consistent with uplift beginning in July 2025 and reaching about 1.5 centimeters (0.6 inch) by the end of the year. Lower right plot is number of earthquakes per day in the immediate area of uplift during 2024-2025. The number of earthquakes in the area was elevated during September-December 2025.
Additional data came from semi-permanent GPS stations. These sites are installed each spring or early summer and removed in the fall. They only record data on site, so we can’t see what the stations measured until they are recovered and the data downloaded. Two of these sites are near the center of the NUA, and sure enough, once the data were processed it was clear that uplift began in July. Between July and the time the stations were collected in September, the ground rose by almost 2 centimeters (less than an inch).
Meanwhile, the nearby continuous GPS sites continued to show horizontal movement away from the NUA. By the end of the year, the horizontal displacement had reached 1 centimeter (less than half an inch).
The final confirmation of the uplift was from interferometric synthetic aperture radar—InSAR. This technique uses satellite radar images recorded at different times to detect changes in the shape of the ground. InSAR data spanning October 2024 to October 2025 showed about 2 centimeters (less than an inch) of uplift along the north rim of the caldera. The pattern of uplift was very similar to that of 1996–2004.
It was clear. The NUA was back!
Interferogram created from satellite radar data collected on October 7, 2024, and October 2, 2025, over the Yellowstone region by the Sentinel-1 satellite system. Colored fringes indicate a change in distance (called range change) between the satellite and ground surface that is caused by surface deformation during the time spanned. In this interferogram, the fringes indicate subsidence (an increase in the range between the ground and the satellite) of about 2 centimeters (about 0.8 inches) in the east part of Yellowstone Caldera during the one-year period between the image acquisition times. In addition, about 2 centimeters (about 0.8 inches) of uplift occurred along the north caldera rim, just south of Norris Geyser Basin. Fringes outside the caldera are mostly related to atmospheric artifacts and do not reflect real ground motion. Black lines are roads, and red dashed line marks Yellowstone caldera.
There was even a small increase in seismicity. Overall, earthquake activity during 2025 was low—only 1,113 earthquakes were located, compared to typical rates of 1,500–2,500 earthquakes per year. There was an uptick in earthquakes during September–December 2025, including a swarm near the NUA where over 100 earthquakes were located, especially in November (the largest being M2.7). It is possible that these earthquakes are a response to subtle stress changes associated with the uplift.
Is this a sign of an impending eruption, or some other hazard? No. Rather, it is another example of Yellowstone’s dynamic nature, and what we can learn about the characteristics of the subsurface using a new generation of sensitive monitoring tools. The current deformation is also minor in magnitude (it pales in comparison to deformation seen at other caldera systems), and before any hazardous activity the deformation rates would accelerate dramatically—something that can obviously be tracked by the continuous GPS network.
YVO will continue to monitor the deformation and report about it in monthly updates and annual reports. You can follow along too! The best way to see the NUA deformation is in the horizontal components of motion at sites P711 (which is near Madison Junction) and NRWY (near Norris Geyser Basin), and the distance change between those sites, which span the uplifting area. A website with this information has been established at https://www.usgs.gov/observatories/yvo/science/uplift-along-north-rim-yellowstone-caldera.
