A field study of pingo ice exposures shows that all pingos contain pore ice and varying proportions of intrusive ice, segregated ice, dilation crack ice, and ice wedge ice. The intrusive ice is derived from water in a subpingo water lens. The ice is usually pure and columnar grained with c axes normal to the direction of heat flow. The columnar grains tend to develop parallel lines normal to the c axis upon exposure to radiation. Precise surveys of pingo growth for the 1973–1983 period show that displacement vectors are upward and radially outward and that radial dilation cracks are produced by circumferential stretching. The dilation cracks, which can open at any time of the year, become infilled with surface water and also with soil from the pingo overburden. The cumulative width of the dilation crack ice approximates the stretch of the pingo overburden as it is domed by pingo growth. Dilation crack ice is vertically banded. The bands are much wider than those in ice wedge ice and have less vertical taper to them. Segregated ice, under high subpermafrost pore-water pressures, may grow in medium-grained sands. Calculations based upon the 1973–1983 growth of one pingo with an intrusive ice core show that the annual increment of intrusive ice is greatly exceeded by pore ice and segregation ice, an observation probably true for many pingos.

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