Patagonia

Giant landslides in the foreland of the Patagonian Ice Sheet and across the extra-Andean tableland

Landslides in Patagonia

I am part of Tomáš Pánek’s research team studying landslides in Patagonia — a collaboration that began with our first paper in 2017 and continues today. The work has been supported by two consecutive grants from the Czech Science Foundation: GA19-16013S (2019–2022), focused on landslides in the Andean foreland shaped by the Patagonian Ice Sheet, and the ongoing GA23-07310S, which targets the giant landslides of the extra-Andean Patagonian tableland.

Giant landslides in the foreland of the Patagonian Ice Sheet

The eastern piedmont of the former Patagonian Ice Sheet hosts some of the largest terrestrial landslides on Earth. Along the traces of the former Lago Buenos Aires and Lago Pueyrredón glacier lobes, we mapped more than 283 large slope failures that detached roughly 164 km³ of material from volcanic mesetas, lake-bounding moraines, and river-gorge walls (Pánek et al., 2018). More than 60 % of this volume failed after the Last Glacial Maximum, much of it during successive drops of glacial-lake levels between ~11.5 and 8 ka — making some of these the largest landslides ever documented in moraines.

A detailed look at the Lago Pueyrredón valley showed that at least 4.5 km³ of weak glacial deposits and Early Miocene marlstone were mobilised since the LGM, with nearly 90 % of the failures clustered around a former moraine-dammed meltwater lake and emplaced as catastrophic debris avalanches (Pánek et al., 2020). Numerical modelling combined with luminescence and radiocarbon dating of the largest rock avalanches on Meseta Belgrano (volumes > 1 km³, runouts > 10 km) indicates that they collapsed into a glacial lake between ~17 and ~12 ka, with a newly identified active fault — likely reactivated by post-glacial rebound — concentrating the failures (Pánek et al., 2023).

Distribution and controls across the deglaciated mountain belt

Mapping at the scale of the whole orogen revised the textbook picture of where landslides concentrate. Across ~305,000 km² of Southern Patagonia, the largest landslides cluster not in the highest, wettest, most tectonically active core, but along the lower, arid, tectonically quieter eastern margin of the former ice sheet, where a larger volume of weak sedimentary and volcanic rock remained (Pánek et al., 2022). An inventory covering ~100,000 km² of the Northern Patagonian Icefield region (15,543 landslides, including 1,006 deep-seated ones) confirmed that geology — volcanic tablelands over weak Miocene rocks — controls the distribution of failures, with paraglacial effects playing only a secondary role (Pánek et al., 2021).

The failed Patagonian tableland

Our current focus is the extra-Andean tableland itself. Coalescent landslides fringe roughly 30,000 km² — about a fifth — of the Patagonian escarpments, where weak Cretaceous–Miocene rocks capped by plateau basalts create one of Earth’s largest and oldest landslide terrains, some failures having persisted for millions of years (Kilnar et al., 2024). We have mapped these in detail — including a 1:120,000 geomorphological map of the Sarmiento Basin, where landslides cover 23 % of the area (Kilnar et al., 2024) — and compiled an East Patagonian landslide inventory (Pánek et al., 2025), while also documenting active, large-scale lateral spreading along the Pampa de Salamanca coastal range with DInSAR (Pánek et al., 2025). This work feeds into broader syntheses of how giant landslides occur, behave, and pose hazards along tablelands (Pánek et al., 2024), and of the topographic settings that give rise to Earth’s very largest terrestrial landslides (Korup et al., 2025).

References

2025

When Tableland Flows: Insights from the East Patagonian Landslide Inventory

Tomáš Pánek, Michal Břežný, Jakub Kilnar, and 1 more author

Geomorphology, Feb 2025

Abs DOI

Landslides in volcanic and sedimentary tablelands encompass some of the world’s largest subaerial landslide areas, yet the controls on their distribution and dominant landslide types remain unclear. Our landslide inventory across 517,000 km2 of volcanic tableland in extra-Andean Patagonia reveals that, alongside common rotational slides and spreads forming nearly continuous fringes around plateaus, flow-type landslides dominated by earthflows are very common. Most of these flows are concentrated in the highest and most humid western part of the tableland, formerly covered by the Pleistocene Patagonian Ice Sheet (PIS), where they constitute three-quarters of the landslide area. Nevertheless, many of the longest flows (>10 km) are located in the steepest parts of the tableland outside the PIS limits, paradoxically often in the driest areas. This suggests that these flows are inherited landforms originating during more humid Quaternary or older periods. Multivariate statistical analysis highlights that the distribution of flow-type landslides is largely influenced by caprock thickness. Decreasing caprock exposes larger areas of weak sub-caprock units such as sedimentary rocks and volcaniclastics on escarpments, thereby increasing the potential for viscoplastic flows. Future studies will require detailed exploration of the geomechanical properties of weak layers within sub-caprock units to achieve a comprehensive understanding of the lithological predisposition of flow-type landslides in the Patagonian tableland.
Large Lateral Spreading and Transient Uplift of Gravitational Grabens along the Passive Continental Margin (Pampa de Salamanca, Argentine Patagonia)

Tomáš Pánek, Michal Břežný, Barbora Koláčková, and 2 more authors

Geomorphology, Nov 2025

Abs DOI

Although large-scale landslides mostly occur in tectonically active orogens, they can also exceptionally develop in intracontinental settings and passive continental margins. This study investigates lateral spreading across more than 80 km of the Pampa de Salamanca coastal range in eastern Patagonia. The region is underlain by weakly consolidated Cenozoic sedimentary and volcaniclastic rocks and lies on a passive continental margin that has experienced rapid late Quaternary uplift, which is unusual for this type of tectonic setting. To analyze the origin and dynamics of large-scale lateral spreading, we integrated optical satellite imagery, TanDEM-X topographic data, field surveys, and interferometric (DInSAR) analysis. Spreading has produced a horst-and-graben morphology defined by synthetic, antithetic, and cross gravitational faults, with scarps exceeding 6 km in length. Grabens occur on both ridge tops and slopes, while lower slope sections often show transitions into rotational and translational slides. Although the lack of chronological markers hinders precise dating, geomorphological evidence reveals evolution throughout the Quaternary and ongoing deformation, evidenced by valley floor offsets and damming by antithetic scarps. DInSAR data from 2017 to 2021 reveal centimetre-scale cumulative horizontal and vertical displacements, with strong uplift (>10 cm) systematically concentrated in graben zones. This uplift peaked after an extreme rainfall event in March–April 2017, which brought over 150 % of the annual precipitation in ten days. We interpret this transient uplift as resulting from the preferential accumulation of water in graben depressions, which led to the wetting and expansion of clay-rich soils. Subsequently, water infiltration along gravitational faults and the upward expansion of clay layers might have further contributed to the uplift. We conclude that substantial Quaternary uplift and erosion of weak rocks in the Pampa de Salamanca range facilitated the development of a regional-scale lateral spreading terrain. Superimposed on deep-seated failure kinematics, uplift of near-surface layers from substantial water input can temporarily reverse the otherwise dominant subsidence of lateral spreading grabens.
Size Estimates of Earth’s Largest Terrestrial Landslides Informed by Topographic Setting

Oliver Korup, Tomáš Pánek, and Michal Břežný

Communications Earth & Environment, Aug 2025

Abs DOI

Abstract Landslides regulate the height of mountains by releasing potential energy and reducing topographic relief. Yet, relief also limits the dimensions of small, frequent landslides in turn. But how local topography, lithology, and climate influence the size distribution and hazard of Earth’s largest terrestrial landslides remains unclear. Here we use Bayesian regression to estimate these effects on landslide volume, drawing on a worldwide sample of 411 cases, each involving\,> 1 km 3 . Nearly two third of their total volume is volcanic and sedimentary rocks within 50 km of active fault zones, clustered in actively uplifting mountain belts and on volcanic plateaus. Volumetric estimates vary most distinctly with dominant topographic setting, regardless of local relief, general rock type, or contemporary climate. These largely negligible effects indicate that volume scaling statistics fail to capture differing bulk lithological properties, let alone a detection bias due to climatic controls on land cover, weathering, or erosion.

2024

Fringed Patagonian Tableland: One of Earth’s Largest and Oldest Landslide Terrains

Jakub Kilnar, Tomáš Pánek, Michal Břežný, and 3 more authors

Earth-Science Reviews, Nov 2024

Abs DOI

Sedimentary and volcanic tablelands host the world’s largest landslide areas, sometimes spanning hundreds of kilometers along escarpments. This study, employing new remote sensing-based mapping and drawing on an expanding body of literature on paleogeographic evolution, revises the extent, controls, and chronology of some of Earth’s largest coalescent landslides in the volcanic tableland of extra-Andean Patagonia. Mostly ancient rotational slides and rock spreads, accompanied by earthflows and occasional rock avalanches, cover approximately 30,000 km2, roughly a fifth of the Patagonian escarpments, with the largest landslide areas exceeding 1000 km2. The immense size of the failed tableland in Patagonia is inherited from stratigraphy and geological history: weak marine and continental Cretaceous-Miocene sedimentary and volcaniclastic rocks, capped by plateau basalts, create a highly unstable environment, outcropping along thousands of kilometers of escarpments. Most landslide areas occupy the steepest, most dissected parts of Patagonian tableland, occurring independently of recent climatic conditions. Some of the largest complexes are found in both the most humid and arid regions. Cross-cutting relationships between landslides and dated glacial, lacustrine, marine deposits, and lava flows reveal that some landslides have persisted for several million years, marking them as some of Earth’s oldest landslide terrains with distinctive geomorphological footprints. Future research on failed Patagonian tableland should include direct radiometric dating, InSAR technology monitoring, and numerical stability modeling of landslides. This comprehensive approach will deepen our understanding of their origins and determine whether these giant landslide fringes predominantly represent fossil features or could be reactivated under contemporary environmental conditions.
Failed Tableland: Geomorphological Map of the Sarmiento Basin (Extra-Andean Patagonia, Argentina)

Jakub Kilnar, Tomáš Pánek, Diego Winocur, and 1 more author

Journal of Maps, Dec 2024

Abs DOI

We present a 1:120,000 landslide-focused geomorphological map of the Sarmiento Basin (Chubut Province, Argentina) and the adjacent landscape. The study area covers about 8000 km2 and can be schematically described as an endorheic basin enclosed by tableland. However, the landscape shows a high diversity of landforms and features. The mapping was mostly conducted manually, based on high-resolution satellite images and a digital elevation model, and supported by field observations. We divided the mapped landforms and features into six categories based on their prevailing origin: structural and volcanic, mass movement, hillslope erosional, fluvial, lacustrine and aeolian. We highlight the abundance of landslides (23% of the study area) in the context of volcanic plateaus and (paleo)lake level evolution. The presented map is unique due to the overall scarcity of detailed geomorphological maps of tablelands worldwide and the insufficient documentation of landslides in the extra-Andean Patagonia.
The Occurrence, Mechanisms and Hazards of Large Landslides along Tablelands

Tomáš Pánek, Kristian Svennevig, Michal Břežný, and 1 more author

Nature Reviews Earth & Environment, Oct 2024

Abs DOI

The largest terrestrial coalescent landslide areas of the Earth, spanning hundreds to thousands of square kilometres, occur along the fringes of relatively low-relief sedimentary and volcanic tablelands. However, difficulties in landslide recognition in these areas have led to underestimations of their frequency and likelihood. In this Review, we explore the global distribution, controls and dynamics of landslides occurring along tableland fringes. Landslide fringes are caused by the uninterrupted and extensive presence of weak sub-caprock lithologies below a more competent caprock. Topography, escarpment height and caprock thickness do not affect landslide size but can locally influence the type of displacement. Rotational landslides dominate most landslide fringes and will eventually lead to tableland consumption over million-year timescales. Some tableland rims can generate catastrophic long-runout rock avalanches or earthflows, which might in turn trigger tsunamis, river avulsion or outburst floods. Tablelands can also fail by slow (centimetre per year) landslide movements sufficient to cause damage to infrastructure. These hazards are increasing especially in high-latitude tablelands owing to cryosphere degradation, as observed in Western Greenland. A more detailed global inventory of landslide fringe activity is urgently needed to better quantify these potential hazards.

2023

The Largest Rock Avalanches in Patagonia: Timing and Relation to Patagonian Ice Sheet Retreat

Tomáš Pánek, Michal Břežný, Rachel Smedley, and 4 more authors

Quaternary Science Reviews, Feb 2023

Abs DOI

One of the largest concentrations of giant landslides (≥108 m3) in Patagonia is in the eastern part of Lago Cochrane/Pueyrredón (LP) valley in Argentina. In addition to minor earthflows and rock slides, this landslide cluster is dominated by rock and debris avalanches that affect the northern slope of Meseta Belgrano, the largest of which have volumes >1 km3 and a runout of >10 km. To determine the chronology of these large landslides and their relationship to the geological setting and the glacial history related to the Last Glacial Maximum (LGM) ∼20–18 ka ago, we combined geomorphological mapping with absolute dating (luminescence and radiocarbon dating) and numerical modelling of slope stability. Dating and cross-cutting relationships with glaciolacustrine deposits suggest that some of the largest rock avalanches collapsed directly into a glacial lake between ∼17 and ∼12 ka, soon after deglaciation, but some were pre-glacial and landslide activity continued until today, posing a potential hazard to the area. In agreement with these data, numerical modelling suggests that slope stability was only marginally affected by ice retreat and glacial lake drainage, and landslides were most likely favoured by relatively low rock strength, related glacially-conditioned topography, and, possibly, seismic activity. A newly identified active fault at the base of the Meseta Belgrano, whose activity was likely enhanced by postglacial rebound, was probably the key factor that concentrated postglacial rock avalanches into the LP valley. We conclude that exceptionally large (km-scale) landslides can occur on slopes made of relatively weak rocks in a glacially-conditioned topographic setting even without a strong direct triggering effect of deglaciation, while fatigue due to long-term seismicity may promote collapse.

2022

Large Landslides Cluster at the Margin of a Deglaciated Mountain Belt

Tomáš Pánek, Michal Břežný, Stephan Harrison, and 2 more authors

Scientific Reports, Apr 2022

Abs DOI

Landslides in deglaciated and deglaciating mountains represent a major hazard, but their distribution at the spatial scale of entire mountain belts has rarely been studied. Traditional models of landslide distribution assume that landslides are concentrated in the steepest, wettest, and most tectonically active parts of the orogens, where glaciers reached their greatest thickness. However, based on mapping large landslides (> 0.9 km2) over an unprecedentedly large area of Southern Patagonia (~ 305,000 km2), we show that the distribution of landslides can have the opposite trend. We show that the largest landslides within the limits of the former Patagonian Ice Sheet (PIS) cluster along its eastern margins occupying lower, tectonically less active, and arid part of the Patagonian Andes. In contrast to the heavily glaciated, highest elevations of the mountain range, the peripheral regions have been glaciated only episodically, leaving a larger volume of unstable sedimentary and volcanic rocks that are subject to ongoing slope instability.

2021

Complex Causes of Landslides after Ice Sheet Retreat: Post-LGM Mass Movements in the Northern Patagonian Icefield Region

Tomáš Pánek, Michal Břežný, Jakub Kilnar, and 1 more author

Science of The Total Environment, Mar 2021

Abs DOI

Although the dynamics of individual rock-slope failures above recently shrinking glaciers have received increasing study, less is known about the spatial distribution of landslides in paraglacial settings. Here, we present a landslide inventory for large deglaciated area (~100,000 km2) situated within the Last Glacial Maximum (LGM) limits of the Northern Patagonian Icefield (NPI). Using satellite images and the TanDEM-X digital elevation model, we mapped a total of 15,543 landslides, among which 1006 are deep-seated landslides (DSLs) with area ≥0.01 km2. The distribution of DSLs is highly asymmetric in a W-E transect of the NPI region, with pronounced clustering along the semi-arid eastern front of the Patagonian Andes. The most strongly affected domain is volcanic tablelands overlying weak Miocene sedimentary rocks, but DSLs tend to also cluster along recently deglaciated (i.e. since the end of the 19th century) eastern margin of the NPI. Compared with other high mountain regions, alpine valleys of the Patagonian Andes are affected by DSLs only in <1% of their area, an order of magnitude lower than in other reported deglaciated mountains. The modest incidence of DSLs in the Patagonian Andes is due to dominance of hard granitoid rocks and relatively weak historical seismic activity. We conclude that 1) geological conditions control the distribution of DSLs and their types in the NPI region; 2) paraglacial effects play secondary (although locally important) roles in the origin of DSLs; 3) local clusters of large DSLs originate due to specifics of the post-LGM landscape evolution, involving drawdowns of glacial lakes and incision of rivers into the unconsolidated deposits; and 4) increased abundance of landslides above the recently shrinking margin of the NPI results from the repeated Holocene fluctuations of glacier snouts around the Little Ice Age (LIA) glacier limits and the spatial coincidence of glacial debuttressing effects with the presence of active faults.

2020

Moraines and Marls: Giant Landslides of the Lago Pueyrredón Valley in Patagonia, Argentina

Tomáš Pánek, Elisabeth Schönfeldt, Diego Winocur, and 4 more authors

Quaternary Science Reviews, Nov 2020

Abs DOI

Giant catastrophic landslides (>108 m3) dot the formerly glaciated mountain forelands of the eastern Patagonian Andes. From geomorphic mapping, sedimentological logs and radiocarbon dating, we infer the emplacement kinematics and approximate timing of giant landslides in moraines and other glacial deposits in the Lago Pueyrredo n valley (LPV), Argentina. For the first time, we report in detail examples of giant low-gradient landslides with hummocky lobes derived from unconsolidated glacial deposits and weak bedrock. We find that at least 4.5 km3 of debris and weak bedrock were mobilized by slope failures in an area of ~500 km2 since the Last Glacial Maximum (LGM; ~25e18 ka). Nearly 90% of this landslide volume originated along the shores of, or as subaqueous failures in, a postglacial moraine-dammed meltwater lake. The larger landslides (>1 km3) detached from moraines fringing the lake, whereas other landslides displaced glacial and lake deposits either on the paleolake bed, or in a river gorge that was cut upon drainage of the glacial lake. Sequences of till, glaciofluvial and glaciolacustrine deposits overlying weak Early Miocene marlstone are mostly conducive to major landslides in the LPV. Crosscutting relationships indicate that largest landslides in the area originated during rapid glacial lakelevel drops. Distribution and internal structure of hummocks within landslide lobes suggest that these landslides were emplaced as catastrophic debris avalanches. It suggests that giant catastrophic landslides in the glacier forelands of Patagonia can result from layered weak rocks, changes in meltwater-lake levels, and possibly as a consequence of strong earthquakes linked to rapid post-glacial rebound following the retreat of the Patagonian Ice Sheet (PIS).

2018

Giant Landslides in the Foreland of the Patagonian Ice Sheet

Tomáš Pánek, Oliver Korup, Jan Lenart, and 2 more authors

Quaternary Science Reviews, Aug 2018

Abs DOI

Quaternary glaciations have repeatedly shaped large tracts of the Andean foreland. Its spectacular large glacial lakes, staircases of moraine ridges, and extensive outwash plains have inspired generations of scientists to reconstruct the processes, magnitude, and timing of ice build-up and decay at the mountain front. Surprisingly few of these studies noticed many dozens of giant (!108 m3) mass-wasting deposits in the foreland. We report some of the world’s largest terrestrial landslides in the eastern piedmont of the Patagonian Ice Sheet (PIS) along the traces of the former Lago Buenos Aires and Lago Puyerredo n glacier lobes and lakes. More than 283 large rotational slides and lateral spreads followed by debris slides, earthflows, rotational and translational rockslides, complex slides and few large rock avalanches detached some 164 \textpm 56 km3 of material from the slopes of volcanic mesetas, lake-bounding moraines, and rivergorge walls. Many of these landslide deposits intersect with well-dated moraine ridges or former glacial-lake shorelines, and offer opportunities for relative dating of slope failure. We estimate that >60% of the landslide volume (~96 km3) detached after the Last Glacial Maximum (LGM). Giant slope failures crosscutting shorelines of a large Late Glacial to Early Holocene lake (“glacial lake PIS”) likely occurred during successive lake-level drop between ~11.5 and 8 ka, and some of them are the largest hitherto documented landslides in moraines. We conclude that 1) large portions of terminal moraines can fail catastrophically several thousand years after emplacement; 2) slopes formed by weak bedrock or unconsolidated glacial deposits bordering glacial lakes can release extremely large landslides; and 3) landslides still occur in the piedmont, particularly along postglacial gorges cut in response to falling lake levels.