I overcame inertia Monday morning and went for a walk in the woods with a temperature of 30º. (It helped that 8:00 is the new 9:00.) I was hoping I might find hair ice. I’ve seen it only once before (I can’t find my blog post), and I wasn’t hopeful. But, there is was. It is as soft as it looks, but not so substantial. Hold some in your hand and it, well, melts.
There are many articles on this “somewhat rare phenomenon,” but I like this sweet one from BBC’s Earth.
In some forests on humid winter nights, peculiar ice crystals form on rotting wood.
The ice looks like bursts of hairy cloud, and sometimes a bit like candy floss.
It is neither. These hair-like wisps appear at night and melt when the sun comes up.
Hair ice only grows on humid winter nights when the temperature is just below 0°C.
Scientists have now discovered exactly what gives “hair ice” its strange shape. It’s caused by a fungus called Exidiopsis effusa.
When the fungus is not present, ice still forms, but in a crust-like structure instead.
The action of the fungus is to enable the ice to form thin hairs – with a diameter of about 0.01mm – and to keep this shape over many hours at temperatures close to 0°C.