YELLOWSTONE NATIONAL PARK — Geologists in Yellowstone National Park (YNP) discovered a new thermal pool in the Norris Geyser Basin back in April. After doing some digging, they believe to have uncovered the origin story.
This week’s Caldera Chronicles — a column written by scientists of the Yellowstone Volcano Observatory (YVO) — was contributed by Scientist-in-Charge Michael Poland. He discusses how the team found the thermal pool and what tools they used to learn its path of evolution.
On April 10, YNP geologists conducted their first routine maintenance of the year for temperature logging stations in Norris Geyser Basin. They discovered a new pool in the Porcelain Basin zone, directly west of an area of vegetation known as “Tree Island.” The pool was about 13 feet in diameter and the light blue water in the pool was 109°F. Poland confirmed to Buckrail that the feature has not yet been named.
According to the column, the pool was surrounded by small rocks which were covered by “light-gray, fine-grained, sandy mud.” Given all the evidence, it seemed like a hydrothermal explosion was to blame.
“That there might have been a hydrothermal explosion at Norris Geyser Basin is not surprising,” wrote Poland, “given that the thermal basin has been the site of numerous such events.”
The scientists used two main tools to help them determine when this new pool might have appeared. High-resolution satellite imagery can be used to investigate thermal changes, although that data is only useful when captured during a cloud-free, daytime period. The satellite data indicated that there was no thermal feature present before December 19, 2024. By January 6, a small depression had formed. And on February 13, an image shows the fully developed thermal pool.
The other tool used to assess hydrothermal activity is an infrasound monitoring station installed in Norris Geyser Basin in September 2023. This station, which monitors low-frequency acoustic energy, can detect explosions and the direction of origin. Though there were no strong explosion signals detected that matched up with the satellite imagery, there were several, small signals that came from the direction of the new feature. The most obvious of which occurred on December 25, 2024. Similar signals were recorded on January 15 and February 11.
The evidence refutes a notion that the feature was formed by a single major explosive event, such as the hydrothermal explosion in Biscuit Basin last summer. Instead, the data points to the theory that multiple small events occurred that threw rocks and silica mud, which caused the small pit to form.
Poland finished up the column by saying: “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.”
