is 20 feet across and over 40 feet deep; one of the largest and hottest springs in the Upper Geyser Basin, and one of the most beautiful. The pool is continuously boiling, sending water a few feet into the air, and producing a large amount of run-off, which flows northwards into the Firehole River. The water is deep blue in color and very clear. All of the main vent is enclosed by a thin, upturned rim of light grey sinter, beyond which is a very shallow overflow pool, colored orange by cyanobacteria.
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