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NatureSpeak Articles

The Magic of Hair Ice

Hair ice overwhelming a branch. Photo by: Sabrina Hinitz

In our winter wonderland of frozen water, the stunning formation of ice crystals on just about any surface can be mesmerizing. From surface hoar growing on the slopes to an ice storm caking everything in its path with a rime of ice. None can deny the beauty in seeing our world freeze.

But one phenomenon stands out for its beauty and uniqueness. Hair ice appears as locks of silky smooth white hair cascading from logs and branches. These incredible structures appear like a wizard's unruly beard growing in waves and curls, long and brilliantly white from a dead branch of a broadleaf tree.

Although these strands appear soft to the touch, they are incredibly brittle, clinging with fragility to the host tree. This somewhat rare occurrence is seen worldwide, where the temperature remains just under freezing. Our climate is well suited to allow this growth to form.

If you're lucky during humid and calm weather, you can find these sculptures of nature where broadleaf trees grow. More often than not, you will find the hair ice on the forest floor before the snow buries the deadfall but sometimes up in the trees themselves.

The mechanism of this fantastic formation occurs in much the same way that frost heave occurs in frozen soil. A reservoir of liquid water soaked into the decaying branch is driven by suction to the surface of the wood, where it freezes. Usually, this layer would spread across the surface of the branch and appear like a shell of ice.

But in the presence of certain fungi, the ice is prevented from recrystallizing together. Instead, the ice continues outward as a single strand. These strands are observed as small as .2mm in diameter and as long as 20cm an incredible feat for something so brittle.

Although more research is needed to find out exactly why this happens, we now know that the crust fungi Exidiopsis effusa is present in all cases. The water that remains liquid within the wood is sucked out through the radial wood rays, which are usually responsible for the lateral transfer of nutrients and moisture within a growing living tree.

The now decaying wood still uses this cellular structure to transfer water saturating the porous wood out, which freezes on the ray lines' surface. The thickness of the strands directly correlates to the thickness of the radial cells. This is then pushed back by an ever-present film of water, constantly being replaced through suction by new ice crystals; the long elaborate waves and curls of ice are formed.

It is suspected that decomposed lignin which make up the cell walls of trees is responsible for the ice segregating without recrystallizing. This lignin is found in the melted ice hair and would not be present without the fungi. Whatever the cause, as soon as the fungus is suppressed, so is the hair ice.

A complex mechanism of a living and decaying forest can produce the most amazing phenomena. The science of nature truly is magic.

Written by: Jamie Marconi


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