Needle ice

Formation

In order for needle ice to form there needs to be a process of ice segregation, which only occurs in a porous medium when supercooled water freezes into existing ice, growing away from the ice/water interface. As water permeates the ice, it becomes segregated into separate pieces of ice in the form of lenses, ribbons, needles, layers or strands of ice.

Needle ice is commonly found along stream banks or soil terraces. It is also found by gaps around stones and others areas of patterned ground. The variety of soil properties also affects where it is found. Places where the soil is much deeper and richer can affect the growth of the ice. Consequently, the deeper the soil, the larger the water content allows it to develop. It can be evidently formed anywhere where underground water is exposed to open (freezing) air.

Needle ice is most suitable in soils with a high silt and organic matter content. Needle ice consists of groups of narrow ice slivers that are up to several centimeters long. Although the literature states that the largest recorded needle ice was at 10 cm in length, specimens 15-20 cm in length have been observed at Gerðuberg, for example.

Needle ice grows up slowly from the moist and water-penetrable soil, and melts gradually in the sun. It can vary in appearance but always shows the consistent growth of ice perpendicular to the surface of the ground. Needle ice looks like a series of filamentous crystals, and is straight or curved in shape. It usually forms in the morning when the temperature drops below freezing point (0 °C).

Environmental impacts

The emergence of needle ice has been recognized as a geomorphic agent of soil disturbance, causing a number of small-scale landforms.{{Cite book | chapter-url = https://books.google.com/books?id=JJHyXx42OQEC&pg=PA709 | editor-first = Andrew | editor-last = Goudie

The growth of needle ice lifts a detached, frozen soil crust riding on top of the layer of ice. When the crust and the ice melt, the soil surface settles back irregularly. This phenomenon is linked to erosion, particularly on streambanks.

Needle ice tends to move rocks in the soil up toward the surface and to shift rocks on the surface into nearby depressions.{{Cite journal | access-date = 2020-02-05

Plant growth

Needle ice affects the growth of plants. Seedlings are often heaved to this surface by needle ice. When the ground hardens the stems and roots of the seedling, they are gripped by the soil and then the formation of needle ice is what pushes them up and out the ground. When the needle ice melts, the seedlings do not settle correctly back into the ground causing them to die. Even if the seedlings are partially heaved by the needle ice, they can still die due to root desiccation.{{Cite journal

References

References

1. link. (2006-05-27 '', EPOD of July 10, 2005. URL last accessed 2007-12-07.)
2. Pidwirny, M.: [http://www.physicalgeography.net/fundamentals/10ag.html ''Fundamentals of Physical Geography,'' 2nd ed., section 10(ag), ''Periglacial Processes and Landforms'']. URL last accessed 2007-12-07.
3. Lawler, D. M.: "Some observations on needle ice", ''Weather'', vol. 44, pp. 406–409; 1989.
4. "Ice Segregation process".
5. (August 2025). "HikersNotebook – Needle Ice".
6. (1970). "A Study of Time Dependence During Serial Needle Ice Events". Archiv für Meteorologie, Geophysik und Bioklimatologie, Serie A.
7. "Needle Ice – Ice Segregation in soil".