Scientists think they know how these remarkable stone patterns form in frozen landscapes

In rocky, icy landscapes, certain patterns of stone can eventually form – it’s like human hands are formed, but no gardener is near them. A new study shows how these formations can be created with needle ice – spikes of ice that rise from the ground and are formed with groundwater.

The researchers used a combination of laboratory experiments and computer models to show how needle ice can shift small rocks and soil particles into patterns, pushing them underneath to slightly change their position.

Because needle ice is more likely to form and thrive on bare patches of land, the surrounding stones are gradually consolidated into the areas around these pieces – creating some spectacular patterns that can stretching for a considerable distance across the landscape everywhere from Norway to Hawaii.

“That kind of selective growth involves interesting feedback between the size of the stones, the moisture in the soil, and the growth of the ice needles,” said geologist Bernard Hallet of the University of Washington.

This idea of ​​stone needle ice production patterns goes back decades, but here the researchers used their own experiments to see how the formations actually came together and then developed a computer model that could simulate the same process.

The experimental setup was a flat square of wet soil just over 1 foot (0.3 meters) in size, with stones placed evenly on its surface. Researchers then put the setup through 30 freeze-thaw cycles that represented volatile temperatures day and night.

As you can see from the resulting videos (including the one above), pattern formation can begin to happen quite quickly, and within the 30 freeze-thaw cycles. The concentration of the stones, the slope of the earth, and the height of the ice needles all affect how the patterns formed.

“The videos are pretty impressive, and they show the ice coming up and in one ring it pushes stones up and moves them slightly to the side,” Hallet said. “Because of those experiments and the capabilities of the individuals involved to analyze those results, we have much more tangible quantitative descriptions of these characteristics.”

The researchers also tied their study to phase separation models – the concept of two distinct parts coming out of one can be useful when analyzing cell structure, gravity fluids, ecological systems, and more.

This area of ​​research goes beyond our own planet as well: Scientists are also working to analyze some of these patterns seen on the surface of Mars, which may reveal what is on the surface and what is on the surface which occurs in the Martian environment.

rock experimentsTwo computer models predicting stone distribution based on initial concentration. (Li et al., PNAS 2021)

What’s more, because needle ice and the patterns it makes are so closely linked to local temperatures, the team believes that changing rock formations over time could help us understand how the planet is respond to rising temperatures.

“Our study highlights the theory of phase separation as an important source of insight into the study of earth patterns in cold regions and their potential value in signaling important changes in the earth’s condition with the warming climate,” write the researchers in their published paper.

The research was published in PNAS.