YVO Figure 4: Illustration of the inner workings of Yellowstone’s geysers.
Figures and pictures used with permission from "Windows into the Earth, The Geologic Story of Yellowstone and Grand Teton National Park", Robert B. Smith and Lee J. Siegel, Oxford University Press, 2000.
Figure 4. Workings of Yellowstone geyser illustrate how heat from cooling magma rises to warm dense salty water circulating in a porous rock later. The brine transfers heat to overlying fresh groundwater, which is recharged by rainfall and snowmelt. The shallow hot water can be trapped and pressurized in small underground reservoirs, then released suddenly through narrow openings, creating geysers.