Scientists planted 133 portable seismometers around Yellowstone’s Old Faithful for two weeks; tiny ground vibrations revealed an underground hot-water reservoir holding about 79 million gallons

Old Faithful may be the world’s most famous geyser, but until recently, no one had a clear picture of the “plumbing” that powers its eruptions. In a landmark 2017 studytitled 'Anatomy of Old Faithful From Subsurface Seismic Imaging of the Yellowstone Upper Geyser Basin', University of Utah scientists deployed 133 small, portable seismometers around Old Faithful and nearby Geyser Hill for two weeks, listening to the faint hum of the ground between eruptions.

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