Since 2004, researchers have been studying the Frasassi cave system, an actively developing limestone cave system located 1500 feet underground in central Italy. Jennifer Macalady, associate professor of geosciences, Penn State and co-author of a paper published on Sept. 2 in Chemical Geology explained that "The main goal of our study was to investigate what happened to hydrogen sulfide in the cave, because when the microbes use hydrogen sulfide for energy, this, along with oxygen, leads to the production of sulfuric acid," said Macalady.
The Frasassi system has cave pathways that formed 10,000 to 100,000 years ago as well as currently actively forming cave pathways, allowing the researchers to compare their measurements and identify the factors contributing to active development.
"What we found is that in certain conditions, the hydrogen sulfide in the water escapes as a gas into the air above the water instead of being 'eaten' by microbes below the water surface," said Macalady. "As a result, the underwater microbes only partially burned hydrogen sulfide. Instead of creating a byproduct of sulfuric acid, they created pure sulfur as a byproduct, which is not corrosive to limestone." But the microbes above the water's surface completely "ate" the hydrogen sulfide, the process that results in the creation of sulfuric acid, which dissolves limestone and contributes to cave growth.
Macalady says that the results would apply to all limestone caves that are rich in hydrogen sulfide, which includes more well-known caves such as Carlsbad Caverns and Lechuguilla Cave in New Mexico and Kap-Kutan Cave in Turkmenistan. #womencavers #speleology #ewls #ScienceWomen
Image: Jennifer Macalady