News Notes
Stone patterns

Many patterns in an otherwise chaotic world sport explanations for their existence that are now taken almost for granted. Build up of sediment directs a river to meander; wind carrying capacity shifts sand dunes grain by grain across a desert. But the idea that physical laws acting on individual particles can explain the Mississippi River’s flow or the Sahara’s changing hillsides is falling out of favor. In its place is the concept that mountains, rivers, deserts and the geomorphology of our planet are self-organizing in a way that incorporates multiple processes that can only be understood when looked at from a variety of perspectives.

In the Jan. 17 Science, Mark Kessler and Brad Werner expand on this idea to explain how the seasonal cycles of freezing and thawing create circles, polygons and labyrinths of stones and soil patterns across the Arctic landscape. Their numerical model considers individual grain sorting as well as the behavior of the feature as a whole under freezing and thawing conditions. They identified feedback mechanisms that move soil toward soil and stones toward stones. Over time, these mechanisms accumulate soils and stones into distinct grouping patterns. “Labyrinths are formed when the stone to soil ratio is low compared to in sorted circles,” Kessler says. When a sloped hillside is brought into the equation, the labyrinths will stretch out forming stripes. Pictured here are formations found in Kvadehuksletta on the western Spitsbergen Island in Svalbard, Norway. Photo by Mark Kessler.

Christina Reed

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