Rahul Somvanshi
Karmactive Team
A milky-blue thermal pool has emerged in Yellowstone’s Norris Geyser Basin, forming through a series of small hydrothermal bursts between December 2024 and February 2025. Park geologists discovered this 4-meter (13-foot) feature during routine maintenance visits on April 10, 2025.
Located in the Porcelain Basin area, the pool sits immediately west of a vegetation patch known locally as “Tree Island.” Its light blue water, heated to 43°C (109°F), rests about 30 centimeters (1 foot) below the rim. Scattered rocks up to 30 centimeters across, coated with light-gray silica mud, surround the pool’s edge – evidence of the mild explosions that created it.
“When what to their wondering eyes did appear, but a blue water spring that was new since last year!” wrote Michael Poland, geophysicist with the U.S. Geological Survey and Scientist-in-Charge of the Yellowstone Volcano Observatory, in the official report.
Unlike dramatic single-event explosions seen elsewhere in Yellowstone, this pool developed gradually. High-resolution satellite imagery tracked its evolution: no feature visible on December 19, 2024; a small depression by January 6, 2025; and a fully formed pool by February 13.
The infrasound monitoring station installed in September 2023 detected low-level acoustic signals from the pool’s direction on December 25, 2024 – Christmas Day – with additional signals on January 15 and February 11, 2025. Notably, these signals weren’t accompanied by seismic activity that would typically mark a major explosion.
“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,” explained Poland. “The feature probably started to develop on December 25, 2024, with further activity occurring in mid-late January and early February 2025.”
This process differs markedly from more dramatic hydrothermal explosions in Yellowstone’s recent history. The April 15, 2024 explosion at Porcelain Terrace and the July 23, 2024 event at Biscuit Basin near Old Faithful both occurred as single, powerful blasts. The new pool’s formation shows how thermal features can develop through more subtle processes.
Norris Geyser Basin is Yellowstone’s most dynamic thermal area. Its location at the intersection of three major fault systems – the Norris-Mammoth fault, the Hebgen Lake fault, and the Yellowstone Caldera ring fracture – creates conditions for frequent change. Historical examples include the 1989 explosion of Porkchop Geyser and older features like a crater in The Gap subbasin that predates written records.
The basin’s extreme conditions make it particularly volatile. Scientific measurements have recorded temperatures as high as 459°F (237°C) at just 1,087 feet (326 meters) below the surface – the highest temperature yet recorded in any Yellowstone geothermal area. The basin also features some of the most acidic waters in the park, with pH levels in some features similar to vinegar.
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The distinctive milky-blue color of the new pool comes from high concentrations of dissolved silica. According to the National Park Service, the thermal waters in Norris contain the highest concentration of silica in Yellowstone, which comes from hot water dissolving the surrounding rhyolite rock. While many Yellowstone hot springs get their colors from thermophilic bacteria, the blue hue of this pool is primarily mineral-based.
Modern monitoring technology played a crucial role in documenting this feature’s formation. The infrasound array installed in 2023 detects low-frequency sound waves that travel farther than audible sounds, allowing scientists to “hear” hydrothermal activity that might otherwise go unnoticed. Combined with satellite imagery from the WorldView system, researchers pieced together the pool’s birth timeline with unprecedented precision.
“Even though this feature had a really subtle emergence, we can actually constrain when and how it formed,” Poland told reporters. “Thanks to high-resolution satellite data and some innovative ground-based monitoring, we have a more comprehensive way of looking at things.”
For park visitors, the new pool serves as a reminder of Yellowstone’s dynamic nature. Located in Porcelain Basin, it joins the park’s catalog of approximately 10,000 thermal features – the highest concentration on Earth. Park authorities emphasize the importance of staying on established boardwalks, as thermal areas can be unstable with thin ground crusts covering scalding water.
In an interview with Newsweek, Poland noted that the new pool is “sufficiently far away from boardwalks and trails to pose no threat to visitors,” but added it’s “a good reminder about why it is so important to stay on marked trails and boardwalks when exploring Yellowstone’s geyser basins.”
The discovery of this new thermal feature demonstrates the ongoing geological activity at Yellowstone National Park. From satellite imagery and geophysical monitoring data, scientists determined that this pool formed through multiple small hydrothermal events between December 2024 and February 2025, with the first signs of activity appearing on Christmas Day.
