Geyser eggs don't spawn a swarm of baby steam-sputtering structures; they are, after all, rocks. But they're far from ordinary: These pebbles are like geologic gobstoppers. They solidify layer by layer as silica from the steamy waters of geothermal pools precipitate out of solution, making each layer a snapshot of pool conditions at the time it was formed.
A trove of these geologic oddities lay scattered in the colorful thermal pools surrounding Yellowstone's Old Faithful geyser, yet strong protections within the national park have long preventing scientists from getting their hands on the eggs. But recently, for the first time, a team of geologists were allowed to remove a single “Old Faithful” egg. Their analysis of the bean-shaped pebble, which is roughly the size of a silver dollar, provides new insights into the egg's delicate structures and could provide clues to how Old Faithful changes overtime.
“It is amazing to think that these little rocks capture and preserve the history of the discharging fluid for as long as it is growing,” says study author Bridget Lynne of the University of Auckland and the Geothermal Institute.
The study was conducted in conjunction with a National Geographic-funded project focused on teasing out near-surface geyser features led by GRC Member Duncan Foley.
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