[Image above] Example of a fairy circle in Namib-Naukluft National Park, western Namibia. Credit: Mark Dumbleton, Shutterstock
The hydrogen sector has progressed significantly in the past few years, with low-emissions hydrogen production projects growing from just a handful of demonstrations to more than 200 committed investments since 2021. But many challenges remain to witnessing a full-fledged hydrogen economy, including producing enough hydrogen in a cost-effective and environmentally friendly manner to facilitate widespread adoption.
In May 2025, researchers led by the University of Oxford published a review paper that explored the possibility of sourcing hydrogen from Earth’s crust. Geologic hydrogen could in theory serve as a good compromise to emissions-heavy production methods because it already exists and simply needs to be extracted. But questions surrounding the scale and location of geologic hydrogen have to date limited the potential of this hydrogen source.
Fortunately, Earth itself may provide clues as to geologic hydrogen’s whereabouts, according to another recent study.
Fairy circles: One term, two very different causes
In European folklore, “fairy circle” refers to a naturally occurring ring or arc of mushrooms found typically in woodlands and grasslands. These circles allegedly grew due to fairies or other supernatural beings dancing at the site, but the true cause of these circles are underground fungi feeding on decaying organic matter in the soil.
But there is another geological phenomenon called “fairy circle” whose cause is less well understood. In contrast to fungal fairy circles, geological fairy circles are large-scale, shallow depressions in the ground devoid of vegetation. They are typically found in arid regions, such as Namibia, Australia, and northeast Brazil.
While previous theories suggest termites or water-stressed plants are the reason for the geological fairy circles, in 2014, researchers in France and Russia made the startling report that hydrogen seepage could be the reason for some of these depressions. This theory gained traction in the following decade as studies identifying similar structures around the world were published (for example, here and here). The latest paper provides more insight into the mechanisms behind this phenomenon.
Hydrogen-induced fairy circles: A rising soufflé
The most recent study was led by Martin Schöpfer, staff member in the Department of Geology at the University of Vienna. He along with colleagues at Itasca Consulting Group (U.S.) and OMV Exploration & Production GmbH (Austria) explain that the pressure of hydrogen gas as it rises to the surface causes the land to rise and then sink in a two-phase process between the gas and water flow—not unlike the motions of a baked soufflé.
Their model demonstrates how hydrogen gas up to 500 meters underground slowly rises and begins to displace the water in interstitial spaces between the sediment. In all models, the gas pressure increased linearly with time for 100 days, followed by 200 days of constant gas pressure, which then caused the rocky terrain above to rise.
Due to the changes in soil chemistry, the immediate vegetation would also die off, aligning with the characteristics of naturally occurring fairy circles.
“You could say that the sediment rises like a soufflé, but here geomechanical processes are at work, whereas with a soufflé it is chemical processes,” says Schöpfer in a university press release.
However, if the hydrogen source used for the model stopped emitting gas in the second phase, then the surface would sink into a depression due to the decrease in pore fluid pressure and consequent increase of effective stress from the high-gas area. This simulated depression is also known as mechanical compaction, and it closely mimics the way the fairy circles are formed naturally.
Fairy circles as hydrogen depth and yield indicators
This new understanding of how geological fairy circles are formed gives rise to questions surrounding the natural hydrogen found at these spots. Could fairy circles serve as landmarks for subsurface areas with large deposits of naturally occurring hydrogen? Some speculate that the size of the fairy circles may also be linked to the depth of hydrogen sources.
“These findings are a real breakthrough,” says Bernhard Grasemann, deputy head of the Department of Geology, in the press release. “Fairy circles could thus serve as natural signposts in the future for finding underground hydrogen sources—a potentially inexhaustible and environmentally friendly energy source.”
With hydrogen technology at the helm of green energy discourse, fairy circles could help propel the discovery of large deposits of naturally occurring hydrogen in the Earth’s crust.
The paper, published in Geology, is “The mechanical genesis of ‘fairy circle’ depressions” (DOI: https://doi.org/10.1130/G53384.1).
