Myriad small columns of ice rise out of the ground. These are ice extrusions.
Typically, these are seen when the daytime temperature is above 0C and the nighttime temperature is below. During daytime, water drains into the cavities within a porous soil; during nighttime, the freezing water expands forcing little columns of ice up through the ground. Those of us who remember the home delivery of milk to a cold doorstep in the winter are already familiar with the process whereby the cap of the milk bottle was lifted atop a column of frozen cream.
Sometimes an extrusion is long enough to bend and droop like a petal under its own weight. This sinuous form prompts some to call them ice flowers, but they, despite that descriptor, should not be confused with frost flowers.
Although an ice extrusion and a frost flower both appear as small frozen structures above the ground surface, each is distinctly different in origin. The ice extrusion arises from the freezing of what was initially liquid water in the ground; the frost flower arises from the condensation of what was initially water vapour above the ground.
Myriad ice extrusions arise from the ground.
