When tableland flows: flow-type landslides in the extra-Andean Patagonia

Landslides in volcanic and sedimentary tablelands rank among the largest mass movement phenomena globally, yet their spatial patterns and prevailing mechanisms remain insufficiently investigated. Our landslide inventory, covering 517,000 km² of volcanic tableland in extra-Andean Patagonia, provides insight into the spatial distribution of various landslide types. Nearly continuous landslide rims along plateau edges are mostly formed by lateral spreads and rotational slides. However, flow-type landslides, particularly earthflows, are also remarkably prominent. These flows are predominantly concentrated in the wetter, higher-altitude western tableland regions that were glaciated by the Patagonian Ice Sheet (PIS) during the Pleistocene. In these formerly glaciated areas, landslides with flow element account for three-quarters of the total landslide area. Nevertheless, some of the longest flow-type landslides, exceeding 10 km in length, occur in steep, arid regions beyond the extent of the PIS. Statistical analysis underscores the critical role of caprock thickness in controlling flow-type landslide occurrence. A thinner caprock results in a higher proportion of weaker sedimentary/volcaniclastic underlying units being exposed along escarpments, thereby increasing susceptibility of the escarpments to viscoplastic deformations. Further investigation focusing on the geotechnical properties of these weak sub-caprock units is essential for a better understanding of the lithological drivers of the flow-type landslides in the Patagonian tableland.