Pingo

The greatest variation in cover thickness, as determined from collapsed pingos, is in irregularly shaped pingos, or those with asymmetrically located ice-cores.

Source: wiktionary

Considerable progress has been made on the discovery and mapping of many open system pingos in central Alaska and Yukon Territory[…], as well as the discovery of pingo-like mounds in the shallow waters of the Beaufort Sea north of the mouth of the Mackenzie River. The greatest advance in pingo research in the last decade has been a consideration and understanding of theory and rate of pingo growth […]

Source: wiktionary

With the exception of small pingos, most pingo ice cores have several ice types. The bulk of the core can be segregated ice, intrusive ice formed from the freezing of bulk water, or any combination of the two types. In addition, dilation-crack ice (tension-crack ice, Brown and Kupsch, 1974) is commonly the main ice type beneath the summit of pingos with craters.

Source: wiktionary

Larger scale frost-heave features, such as pingoes, are rare because there is insufficient water available, generally, for the growth of large ice bodies.

Source: wiktionary