Yellowstone grew a brand new thermal pool over the winter of 2024-25. Nobody saw it happen. Scientists returned to Norris Geyser Basin that April. They found a 13-foot-wide, ice-blue pool that had not been there before. The water was 109 degrees, about as hot as a bath. Sound sensors later traced its birth to tiny explosions in December, January, and February. It had been buried under snow the whole time.
