Thermal image of Castle Geyser eruption (1:58 PM-onward, 11 August 2016) 1
The temperature scale is in degrees Fahrenheit.
Castle Geyser is the namesake & largest member of the Castle Group in Yellowstone’s Upper Geyser Basin. It has a large, gray, asymmetrical, terraced geyserite mound that is relatively old, estimated to be near-latest Pleistocene to mid-Holocene in age. Minor eruptions are water-phase only, and last less than 15 minutes. Major eruptions have a longer-than-15 minutes water phase, which gradually changes to a mixed water-steam phase and then a moderately noisy steam phase.