Geothermal Phenomena Geothermal phenomena like Mammoth Hot Springs in Yellowstone National Park typically get their heat from a shallow magma chamber. As the puddle rises, so does the rim. Eventually, the puddle overflows and the flowing mineralized water rounds off the rim of the terrace with new mineral deposition. Films often portray Old Faithful going off with a roar. In reality it sounds a lot more like a giant fire hose.
Geysers are very transient phenomena.
They plug up with mineral deposition or blow themselves apart with violent eruptions. Old Faithful probably didn't exist a few thousand years ago and probably won't exist in a few thousand years more. Looking into the Grand Canyon of the Yellowstone, it becomes obvious that the present geothermal phenomena in Yellowstone are the tiniest fraction of what has occurred there. The entire plateau has simmered in boiling water, and the vivid colors of the canyon are all due to hydrothermal alteration of the rocks. 20 million years ago, the San Juan Mountains of southwestern Colorado were another Yellowstone, a volcanic plateau parboiled in geothermal waters.