Recently, I took the following picture:

enter image description here

I have read about this phenomenon and I think it is caused by water vapour that is pressed out of the ground and then freezes due to low temperature. However, I cannot recall the name of this phenomenon and I couldn't find it on the internet.

The picture was taken in the Alps around 3000 meters above sea level in August. I'm pretty sure that the white thing is ice. They're a couple of centimetres long and quite porous. I found them on top of an earthy and slaty flank of a mountain early in the morning (around 8 am).

What is this phenomenon called?


1 Answer 1


This is needle ice which forms when moist soil freezes, for example during a cold night. Freezing starts at the ground surface and as ice is formed moisture gradients develop which draws water to the freezing front and growth continues. Ideal conditions may be a sub-freezing night after a rainy day or a sub-freezing night after a day of snow melt.

According to the National Snow and Ice Data Center (NSIDC) site needle ice be up to 40 cm in length. Since the favourable conditions are not unique to soils, although most often encountered in soils, needle ice can develop from freezing of, for example, vegetation

  • $\begingroup$ I have seen something similar recently next to Lake Michigan. It was not on top of soil. Here's a photo with exaggerated contrast to show the detail better. $\endgroup$
    – Glacialis
    Feb 11, 2015 at 18:17

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