Molards and Their Relation to Landslides Involving Permafrost Failure

MILANA, JUAN PABLO

PERMAFROST AND PERIGLACIAL PROCESSES

JOHN WILEY & SONS LTD

Año: 2016 vol. 27 p. 271 - 284

1045-6740

Molards are conical-shaped, often symmetrical debris mounds with a distinctive radial grain size gradation, which were first named in the Alps over 100 years ago. Historically, these landforms did not receive much academic attention as they were rarely observed. Today, six different genetic hypotheses can be applied to molards, and the most recent has suggested a link to permafrost failure. The aim of this research was to test the hypothesis that molards result from the failure of permafrost-bearing ground and subsequent thawing of the frozen debris boulders. This hypothesis is tested by: (1) reviewing the known global distribution of molard-bearing mass movements with respect to permafrost distribution; (2) investigating a landslide in the Andes of Argentina that unequivocally relates to permafrost failure; (3) describing and interpreting the external and internal structure of molards, applying sedimentary transport concepts; and (4) reproducing molards by laboratory simulation. The results show that, with few exceptions, molards are produced by melt-out of ground ice in permafrost blocks. In particular, a permafrost source of the mass flow is more certain for landslide deposits that are densely populated by molards. This study serves to reappraise the presence of molards as they could be used to track ground ice loss and potential permafrost degradation in mountainous areas and hence climate change. Copyright © 2015 John Wiley & Sons, Ltd.