columnar ice

Columnar ice is a type of ice structure that forms when crystals with a horizontal c-axis orientation wedge out adjacent crystals with a vertical c-axis orientation, causing them to grow larger in diameter with depth. This results in a structure composed of adjacent columns of single crystals. This ice formation process is distinct from the typical freezing of water and is often associated with snow ice, which forms when snow cover is heavy enough to submerge the ice and cause water to saturate the snow, which then freezes. When viewed under a microscope with crossed polaroid sheets, the crystal structure of columnar ice is clearly visible.1