Explore how rocks form weaving patterns in frozen landscapes

Nature is full of repeating patterns that are part of the beauty of our world. An international team, including a researcher from the University of Washington, used modern tools to explain the repeating patterns of stones that form in cold landscapes.

The new study, published Oct. 5 in the Proceedings of the National Academy of Sciences, uses experimental tools to show how ice needles growing haphazardly on frozen ground can gradually move rocks in regular, repeating patterns. The team, based primarily in China and Japan, uses a combination of new experiments and computer modeling to describe these striking features with new theoretical knowledge.

“The presence of these amazing models that develop without any human intervention is quite striking in nature,” said co-author Bernard Hallet, professor emeritus of Earth and space sciences at UW and member of the Center. quaternary research. “It’s like a Japanese garden, but where’s the gardener?”

Hallet specializes in the study of patterns that form in polar regions, high mountains and other cold environments. One of the reasons for the patterns is needle ice cream. As the temperature drops, the moisture in the soil turns into spikes of ice crystals that protrude from the ground.

“When you step out into the garden after a frosty night and feel a little crackle under your foot, you are probably walking on needle ice,” Hallet said.

As needle ice forms, it tends to lift soil particles and, if there are any, small stones. More needle ice can form on patches of bare soil compared to areas covered with rocks, Hallet said. The ice needles will move the remaining stones slightly in the more bare area. Over the years, the stones begin to cluster together in groups, leaving the bare plates mostly without stones.

“This type of selective growth involves interesting feedbacks between stone size, soil moisture, and ice needle growth,” Hallet said.

Hallet had previously reviewed another scientific paper by first author Anyuan Li, formerly at Shaoxing University and now at Tsukuba University in Japan. The two have started a collaboration that combines Hallet’s long-standing expertise in investigating patterns in nature with Li and his collaborators’ experience in experimental science and computer modeling.

Senior author Quan-Xing Liu of East China Normal University uses fieldwork and laboratory experiments to understand self-organizing patterns in nature. For this study, the experimental setup was a flat square of moist soil just over 1 foot on each side (0.4 meter) that began with stones spaced evenly across the surface. The researchers carried out the experiment over 30 freeze-thaw cycles. By the end of this period, regular models had started to appear.

“The videos are quite striking, and they show that the ice has just come up and in one cycle, it lifts rocks and moves them slightly to the side,” Hallet said. “Because of these experiences and the abilities of the individuals involved to analyze these results, we have much more tangible quantitative descriptions of these characteristics.”

Other experiments examined how the pattern changes depending on the concentration of stones, the slope of the ground, and the height of the ice needles, which is also affected by the concentration of stones. Based on these results, the authors wrote a computer model that predicts the patterns that will appear depending on the concentration of stones on the frost-prone surface.

Reference: Li A, Matsuoka N, Niu F et al. Ice needles weave stone patterns in frozen landscapes. PNAS. 2021; 118 (40). doi: 10.1073 / pnas.2110670118

This article was republished from the following materials. Note: The material may have been modified for its length and content. For more information, please contact the cited source.

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