Hair ice is a whimsical thing. It grows on the rotting branches of certain trees, with grouped strands of silk-like hair protruding from the wood. Conditions must be ripe for formation, usually humid winter nights when air temperatures dip below the freezing level. Researchers call it a “somewhat rare and fleeting phenomenon.”
Physicist Christian Mätzler, of the Institute of Applied Physics at Switzerland’s Univ. of Bern, was ambling through the forest the first time he stumbled upon hair ice. The sight inspired awe, and he was spurred to investigate the phenomenon.
On July 22, Mätzler and his colleagues published their research identifying the fungus responsible for hair ice’s growth in Biogeosciences, confirming an almost 100-year-old hypothesis.
The research paper combines the experiments and research done by Mätzler, German biologist Gisela Preuss and Swiss chemist Diana Hofmann. By studying wood samples collected over three winter seasons from western forests in Germany, Preuss found and identified 11 species of fungi colonizing the wood. However, Exidiopsis effusa was present in all the samples; and in more than half the samples, it was the only species of fungi present.
Meanwhile, Mätzler was prodding into the physics behind hair ice. “He found, confirming the guesses by other researchers, that the driving mechanism responsible for producing ice filaments at the wood surface is ice segregation,” according to the European Geosciences Union. “Liquid water near the branch surface freezes in contact with cold air, creating an ice front and ‘sandwiching’ a thin water film between this ice and the wood pores. Suction resulting from repelling intermolecular forces … then gets the water inside the wood pores to move towards the ice front, where it freezes and adds to the existing ice.”
“Melted hair indicated the presence of organic matter,” the researchers wrote. And “treatment by heat and fungicide suppresses the formation of hair ice.”
Hoffman studied the water from melted hair ice and found, via chemical analysis, the complex organic compounds lignin and tannin. The find is further confirmation of the biological influence on hair ice.
Hair ice was observed by German geologist Alfred Wegener, who is known for his continental drift theory, in 1918. According to James R. Carter, of Illinois State Univ.’s Georgraphy-Geology Dept., Wegener “assumed the ice was associated with fungus evident on the dead wood but he was not able to identify the fungus.”
The team’s find puts Wegener’s speculation to rest.
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