07/14/2025
Christmas in July!? 🎀🎄🎁
Santa delivers a new thermal feature to Yellowstone.
"The feature probably started to develop on December 25, 2024, with further activity occurring in mid-late January and early February 2025."
Yellowstone National Park geologists recently identified a new thermal feature in Norris Geyser Basin. Its formation may have coincided with a visit from St. Nicholas. It's rhyme time in today's !
https://www.usgs.gov/observatories/yvo/news/another-new-hole-ground-norris-geyser-basin
On April 10, 2025, geologists from Yellowstone National Park were conducting routine maintenance of temperature logging stations at Norris Geyser Basin—their first such visit to the area since the previous fall.
When what to their wondering eyes did appear, but a blue water spring that was new since last year!
The new pool they found is located in the Porcelain Basin subbasin of Norris Geyser Basin, immediately west of a patch of vegetation informally known as “Tree Island.” It is about 4 meters (13 feet) across, and the water in the pool was warm (about 43 °C, or 109 °F), light blue in color, and about 30 centimeters (1 foot) below the rim.
They spoke not a word and went straight to their work, as this was a job that they would not shirk.
The geologists found that the pool was surrounded by numerous small rocks up to 30 centimeters (about 1 foot) across, and the rocks themselves were covered by light-gray, fine-grained, sandy mud. There also appeared to be two layers exposed in the sides of the pool, but the lower “layer” was just a coating left on the steep side of the pool when the water was at a higher level.
With all of this evidence of quite a commotion, they knew they had found a hydrothermal explosion!
That there might have been a hydrothermal explosion at Norris Geyser Basin is not surprising, given that the thermal basin has been the site of numerous such events. Some, like a crater in The Gap subbasin, probably occurred before people were documenting the area and have an unknown age. Others, like the 1989 explosion of Porkchop Geyser, were well observed. And thanks to a new monitoring station installed in September 2023, explosions can now be detected by geophysical data, including an explosion in the Porcelain Terrace area in April 15, 2024, that left a crater a few meters (several feet) across.
So when did this feature near Tree Island form? Might it have been associated with an earthquake swarm?
One tool that can be used to investigate thermal changes at Yellowstone is high-resolution satellite imagery. Although these data aren’t useful at night or during cloudy conditions, the daytime, cloud-free images provide exceptional views of the ground. The satellite data indicate that there was no feature present on the west side of Tree Island prior to December 19, 2024. By January 6, 2025, a small depression had formed in that area. An image from February 13, 2025, shows the water pool, indicating that the feature had fully developed by that time.
Another helpful tool for assessing hydrothermal activity in Norris Geyser Basin is the new monitoring station that was installed in September 2023 and that uses infrasound—low frequency acoustic energy—to detect hydrothermal activity. Not only can infrasound arrays “hear” explosions, but they can also tell the direction from which the sound originated! Interestingly, there were no strong and unambiguous explosion signals during the time over which satellite imagery indicate the feature formed. There were, however, several low-level acoustic signals that came from the direction of the new feature. The most obvious such signal was recorded on December 25, 2024, but it was relatively weak, and there was no associated seismic signal—something that would be expected from a significant explosion. Similar acoustic signals were recorded on January 15 and February 11, 2025, but again there were no seismic signals.
What does this combination of data all mean? Could it be used to investigate the scene?
Clearly the new thermal feature did not form in a single major explosive event, like the one of April 15, 2025, in Norris Geyser Basin or the well-observed event of July 23, 2024, at Biscuit Basin near Old Faithful. Rather, it appears that the feature formed via multiple small events that initially threw rocks and later threw silica mud a short distance, creating a small pit that became filled with silica-rich water. The feature probably started to develop on December 25, 2024, with further activity occurring in mid-late January and early February 2025.
The latest new thermal feature in Norris Geyser Basin—perhaps the most dynamic area in Yellowstone National Park—demonstrates the spectrum of ways in which hydrothermal features evolve. Some form during brief and violent episodes of change. Others may take shape far more gradually, like the new feature found near Tree Island that seems to have begun taking shape on Christmas 2024.
That’s the story from Norris, what a sight! And it seems to have started on Christmas night.
(Photo: View looking northwest at a new thermal pool in the Porcelain Basin area of Norris Geyser Basin, Yellowstone National Park, that probably formed in a series of mildly explosive events between late December 2024 and early February 2025. The rocks and white material (silica mud) surrounding the pool were probably ejected as the feature formed. The pool is about 4 meters (13 feet) across. U.S. Geological Survey photo by Mike Poland, May 12, 2025.)
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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, and Jeff Hungerford, Park Geologist with Yellowstone National Park.
