13-foot-wide baby blue pool shows up in Yellowstone. What caused it to form?
Get ready for a little Christmas in July: There’s a new baby blue pool in Yellowstone National Park, and science suggests it started forming on the winter holiday.
Park geologists discovered the new thermal feature during routine maintenance of temperature logging stations at Norris Geyser Basin in April, officials said in a July 14 news release. It was their first visit to the area since fall.
Because of the timing of the new feature, officials sprinkled some Christmas cheer among the scientific explanations in the release.
“When what to their wondering eyes did appear, but a blue water spring that was new since last year!” the release says.
The new pool is in the Porcelain Basin sub-basin of the Norris Geyser Basin and is just west of a patch of vegetation known as “Tree Island.”
It’s about 13 feet across, 109 degrees Fahrenheit and filled to about a foot below the rim. A photo shows the milky blue pool.
Its formation was visible from space, and was likely caused by several small hydrothermal explosions in the area, high-resolution satellite images show.
“The satellite data indicate that there was no feature present on the west side of Tree Island prior to December 19, 2024,” officials said. “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.”
A new hydrothermal explosion monitoring station detects explosions by geophysical data, including one in the Porcelain Terrace area that left a several-foot-wide crater in April 2024. It uses infrasound (low frequency acoustic energy) to “hear” explosions and the direction they originated from, officials said.
“Interestingly, there were no strong and unambiguous explosion signals during the time over which satellite imagery indicate the feature formed,” officials said. “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. ...
“What does this combination of data all mean? Could it be used to investigate the scene?”
It means the new thermal feature didn’t form in a single major explosive event like the one in April 2024 or the massive hydrothermal explosion last summer at Biscuit Basin near Old Faithful, when charcoal-colored debris and steam blasted hundreds of feet into the air and ultimately changed the shape of Black Diamond Pool, McClatchy News reported at the time.
Instead, the feature formed via several small events that threw rocks and later silica mud a short distance, creating the small pit that then 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,” officials said. “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 features form from brief, violent episodes of change, officials said. Others take shape more gradually, like the new (and yet unnamed) icy blue pool formed during Christmas 2024.
“That’s the story from Norris, what a sight! And it seems to have started on Christmas night,” officials said.
Several people in the comments of USGS Volcanoes’ Facebook post about the pool seemed enchanted by the milky blue hue.
“It would be awesome to come up with that same color in a paint and then name it after this new geyser,” someone said, suggesting that “Christmas Geyser Blue might be a fitting name for the paint, especially if it is named Christmas Geyser or something similar.”
Several people also shared that they were delighted by the festive presentation of the information.
“Christmas in July!” someone said.
“This is fun,” another person said. “Amazing to me that this comes out of the earth.”
