Genesis, Morphology, Age and Distribution of Cryogenic Mounds on Kaffiøyra and Hermansenøya, Northwest Svalbard

Three main types of cryogenic mounds on the coastal plains (strandflats) of Kaffiøyra and Hermansenøya on northwest Svalbard are distinguished according to their distribution, morphology, internal structure, genesis and age. The mounds include aggradational forms: a previously unrecognised hydraulic pingo, frost peat mounds with either a minerogenic core (mineral palsas) or an ice/ice‐peat core, and earth hummocks. Previously unrecognised degradational features represent thermokarst mounds. Individual types of mounds have developed in different geomorphological locations: (i) in the forefield of a retreating subpolar glacier over fault zones (hydraulic pingo 7.8 m high); (ii) on peat bogs (two types of frost peat mounds 0.7–1.3 m high and thermokarst mounds 0.5–0.8 m high); (iii) on raised beaches (high earth hummocks 0.5–1.0 m high); and (iv) on flat and wet tundra surfaces (miniature earth hummocks 0.2–0.3 m high). Although large, pingo‐type mounds are typical on Svalbard, only one pingo occurs in the study area because of lithological, hydrological and geomorphological conditions of the area. These conditions, together with thick permafrost, do not allow the outflow of sub‐ and intra‐permafrost water to the surface. Some cryogenic mounds are the result of climate fluctuations in the recent part of the Holocene (Little Ice Age). The oldest frost peat mounds from Hermansenøya developed 3.0–2.5 kyr BP, while the pingo is still growing. Copyright © 2015 John Wiley & Sons, Ltd.