New research reveals geysers like Yellowstone National Park's Old Faithful periodically erupt as a result of "loops or side-chambers in their underground plumbing."
These underground bends and loops are believed to be secret behind geyser eruptions, the University of California, Berkeley reported. The features trap steam and bubble it out at a slow pace until it heats the overhead water column to a state of almost boiling. Eventually sudden boiling occurs from the top of the column, releasing pressure built up in the water below, causing it to also boil. As the column boils from the top downwards, water and steam are catapulted hundreds of feet into the air.
"Most geysers appear to have a bubble trap accumulating the steam injected from below, and the release of the steam from the trap gets the geyser ready to erupt," said Michael Manga, a UC Berkeley professor of earth and planetary science. "You can see the water column warming up and warming up until enough water reaches the boiling point that, once the top layer begins to boil, the boiling becomes self-perpetuating."
To make these findings a team of researchers looked at geysers in Chile and Yellowstone, as well as lab-built geysers made of glass. They found the experimental geyser did not erupt as regularly as the ones observed in nature. They fed temperature and pressure sensors as deep as 30 feet into geysers to observe their underground structure.
"At many geysers it looks like there is some cavity that is stuck off on the side where steam is accumulating," Manga said. "So we said, 'Let's put in a cavity and watch how the bubble trap generates eruptions.' It allows us to get both small eruptions and big eruptions in the lab."
The first measurements were taken inside of the Great Geysir in Iceland back in 1846. These measurements suggested eruptions are triggered when water starts to boil at the surface, reducing pressure within the water column and allowing it to propagate downward. These new findings link the temperature and pressure changes in the water column to the observed "underground plumbing." In places such as Yellowstone, the bubbles that escape from the underground loop also cause mini eruptions, called "preplay," which stop when the water column in the geyser stops boiling.
These findings could help researchers gain insight into erupting volcanoes, which cannot be studied as closely due to their extreme heat. The team looked at the measurements they had taken and combined them with above-ground measurements from seismic sensors and tiltmeters to get an idea of what occurs underground during a volcanic eruption.
The findings were published in a recent edition of the Journal of Volcanology and Geothermal Research.
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