Palsas, lithalsas and remnants of these periglacial mounds. A progress report

There is no general agreement about the meaning of the word 'palsa'. Usage and recent suggested definitions indicate that the word is chiefly used for cryogenic mounds covered by peat that were formed by an accumulation of segregation ice in the discontinuous permafrost zone. Lithalsas are similar mounds, but without any peat cover. The thickness of aggradation ice on the top of lithalsas can be considerable. Use of development and decay palsas as indicators of climatic change is difficult. The climatic conditions in which lithalsas form are much more restricted than those for palsas and, as a consequence, regions where lithalsas exist are rather rare. After melting, lithalsas leave ramparted depressions; the mass movements on the peaty slopes of palsas are less propitious to the formation of ramparts. Some of the pingo remnants described in western Europe are, more accurately, lithalsa traces.