“Honeycomb structures on rock faces have been closely studied over the past hundred years, but there’s still no conclusive understanding of how they form,” the lead author of the study, Associate Professor Alexander Safonov of Skoltech Materials, commented. “A number of hypotheses have implicated wind and water erosion, ice and salt crystal formation, sharp temperature fluctuations, and even fungi in honeycomb formation.”
“In this study, we adopt the saltwater evaporation hypothesis, mathematically simulate the process, and identify the ‘Goldilocks zone’ in which honeycomb erosion happens: not too dry, but not too wet either,” the scientist went on. “In terms of monument conservation, our findings may help pinpoint the particular spots on historic buildings, statues, etc. that are most vulnerable to honeycomb erosion, as well as identify safer locations for positioning these objects. Estimating the life span of a projected structure is another possibility.”
The various types of weathering are all known to be capable of damaging rock, but until now no laboratory experiment or mathematical model could reproduce the intricate network of cavities that defines honeycomb weathering. In their study, the Skoltech researchers managed to simulate just that. What’s more, the simulation even explains the characteristic smooth rock face often seen below the weathered region and the unaffected area above it.
Honeycomb formation in Apolena Rock City, Czech Republic. The values on white rectangles describe how much moisture per unit volume the rock is likely to contain at a given height above the ground. The team’s simulation shows that honeycomb formation is favored by a moderate moisture content.