Long Runout Landslides with Associated Longitudinal Ridges in Iceland as Analogues of Martian Landforms

Abstract. Much work has been done to study the behaviour of long runout landslides and their associated longitudinal ridges, yet the origin of the hypermobility of such landslides and the formation mechanism of longitudinal ridges are poorly understood. As terrestrial long runout landslides emplaced on glaciers commonly exhibit longitudinal ridges, the presence of these landforms has been used to infer the presence of ice on Mars, where hundreds of well-preserved long runout landslides with longitudinal ridges are found. However, the presence of the same landforms in regions where extensive glaciations did not occur, for instance, on the Moon and in the Atacama region on Earth, suggests that ice is not the only factor influencing the formation of long runout landslides with longitudinal ridges.

Iceland is a unique region for its high spatial density of well-preserved hypermobile large landslides with longitudinal ridges. Here, we compiled the first catalogue of Icelandic long runout landslides with longitudinal ridges and we compared them with martian long runout landslides with longitudinal ridges of similar length. Moreover, we present detailed morphological observations of the Dalvík landslide deposit, in the Tröllaskagi peninsula, Iceland and compare them with morphological observations of martian landslides.

Our results show that Icelandic long runout landslides share key features with martian analogue deposits, including splitting of longitudinal ridges and development of associated en-echelon features. Therefore, Icelandic long runout landslides with longitudinal ridges represent good analogues of martian landforms. Moreover, Iceland represents the ideal site to investigate these landforms at a regional scale and their link with ice retreat following the Late Glacial Maximum, which could also provide insights into martian paleoclimatic and paleoenvironmental conditions.