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 Geyser EruptionPhoto: CanvaOld 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.
• By turning everyday micro-vibrations, caused by wind, water, tourists, and the geyser’s own boilin