Postscript to Frostweeds: Needle Ice

At the end of the third week in January, Central North Carolina experienced a severe winter storm, with snow, sleet, and freezing rain.  Warm weather began to prevail in the days that followed, and the ice and snow melted rapidly, leaving the ground saturated with moisture.   A series of overnight hard freezes then produced perfect conditions for natural ice sculptures to form, particularly ice extruded from porous soils, a phenomenon known as needle ice.  This phenomenon was mentioned briefly in the previous article describing natural ice sculptures produced by Frostweed – Verbesina virginica.  The conditions required for needle ice are the same as for plants that produce ice sculptures: temperatures above freezing below the ground surface interacting with air temperatures below freezing right at the surface of the ground.

The photo below is of an open, grassy field next to a parking lot.  What at first appear to be skiffs of remaining snow, are actually needle ice produced overnight from the hard freeze.

Needle Ice in an Open Grassy Field

Needle Ice in an Open Grassy Field

A couple of closer views follow.

Needle Ice in a Grassy Field

Needle Ice in a Grassy Field

Closer View of Needle Ice

Closer View of Needle Ice

The next photo shows more clearly the ice rising directly from the soil surface itself, often forming narrow ribbons.

Needle Ice Rising Directly From the Bare Soil

Needle Ice Rising Directly From the Bare Soil

A closer view of the needles of ice show grooves in the extruded ice very similar to those produced by plants.

Closer View of Grooved Ice Needles

Closer View of Grooved Ice Needles

Ice formations produced by soils are much more common than those of plant origin.  However, there are sometimes entire winters when the conditions are unfavorable for ground ice as well, particularly  during dry winters when there is not enough moisture at the surface of the soil.

Herb Amyx

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