Scientists say they have solved the mystery of the “floating rocks”—the eerily balanced stones on Siberia’s frozen lakes that perch on slender pillars of ice. Named “Zen stones” for their resemblance to the carefully stacked rocks of Zen gardens, researchers reproduced the formations in the laboratory, showing they arise from uneven sublimation rather than wind or melting.
Physicists Nicolas Taberlet and Nicolas Plihon of the French National Centre for Scientific Research reported in a 2021 paper in Proceedings of the National Academy of Sciences that the stones act like tiny umbrellas, shading a thin column of ice beneath them from diffuse solar radiation so that the surrounding ice sublimates away while the protected column remains.
“We demonstrate that they are caused by a variation in the sublimation rate of the surrounding ice, which leads to the slow formation of a pedestal,” the researchers wrote. They added that far-infrared radiation emitted by the stone itself then helps carve the shallow depression that conforms to the rock’s shape.
The Zen stones formation consists of a rock balancing on top of an ice pillar
Baikal Zen is a rare phenomenon on Siberia's Lake Baikal, where stones rest atop thin ice pedestals due to wind, sunlight, and sublimation. It creates a stunning visual on the lake's clear, frozen surface during winter. pic.twitter.com/67f4wJTU4o
— crazy for facts (@crazyforfacts) November 26, 2024
The formations, found on Lake Baikal and elsewhere in cold regions, consist of a rock balancing atop a narrow ice pillar surrounded by a small hollow. The balanced stones have long baffled observers and spawned online fascination; some have suggested wind erosion as the cause. Taberlet and Plihon said the pedestals show no sign of mechanical wear and can even be found in caves, which argues against wind as the dominant force.
To test their idea, the team recreated the phenomenon in a vacuum chamber. They placed an aluminum disk as a stand-in for a stone on an ice block and exposed it to far-infrared “black-body” radiation from the chamber walls. Without the disk, the ice sublimated uniformly; with the disk in place, a pedestal formed beneath it. The laboratory process was deliberately accelerated, the researchers said, whereas comparable pedestals form over several weeks in nature.
Numerical modeling supported the experiments. Diffuse solar radiation drives sublimation of the exposed ice surface, while the stone’s shade reduces local sublimation beneath it. The stone’s own far-infrared emission produces the basin around the base of the pillar, the researchers concluded.
Zen stones in Siberia are the structural opposite of ice glaciers
The team contrasted Zen stones with much larger glacier tables, structures whose tops remain intact because the rock insulates the ice beneath and slows melting. “Glacier tables form because the rock may act as a thermal insulator,” Taberlet and Plihon wrote, “The conclusion is exactly opposite for Zen stones.”
Beyond explaining a striking natural curiosity, the scientists said their work sheds light on other differential ablation processes on ice surfaces, including debris-covered glaciers, features whose behavior is important as the world warms, and on icy bodies elsewhere in the solar system.
Lake Baikal and its "floating rocks"
The stones are first pushed by strong winds to the icy surface of the lake and then warmed by sunlight. The surface beneath the rocks melts slightly only a small area of contact remains, keeping the rock suspended above the lake
This… pic.twitter.com/zVgrVQ1bcm
— Moon Dragon (@frozenaesthetic) November 10, 2023
“Understanding this process sheds light on other differential ablation processes encountered on ice surfaces,” the researchers wrote, noting the wider relevance of sublimation-driven pattern formation.
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