Measured water temperature as a function of depth in the conduit of...

Measured water temperature as a function of depth in the conduit of Old Faithful geyser five minutes and fifteen seconds before an eruption (blue dashed curves from Birch and Kennedy, 1972). Both curves show that the temperature at the top of the water column (~5.5 m (18 feet) below the top of the geyser cone) coincides with the boiling curve for pure water (red curve), but it is lower than the boiling temperature of pure water with increasing depth. The boiling temperature of pure water at the elevation of Old Faithful geyser (2245 meters or 7,367 feet) is about 93 °C (199 F). Nearly two decades ago, former Yellowstone National Park ranger Rick Hutchinson and colleagues proposed that dissolved carbon-dioxide in the geyser's water could explain the sub-boiling temperatures shown in the figure. USGS scientists measured the dissolved gas concentrations at the bottom of pools near Old Faithful geyser and their results are consistent with the earlier hypothesis.