Papers by Stella Moreiras
Advancing Culture of Living with Landslides, 2017
The study area is located along the Andean active orogenic front comprising the most seismically ... more The study area is located along the Andean active orogenic front comprising the most seismically active region of Argentina. Main Quaternary deformation is concentrated in this Western central part of the country associated with active faults linked to an intense shallow seismic activity (<35 km depth). During the last 150 years, the region has suffered at least six major earthquakes with a magnitude greater than Ms ≥ 7.0. The focus of this research is to analyse the landslide behaviour along this Andean active orogenic front. To that end, we carried out a landslide inventory along Precordillera (31°–33°S). We analysed type, size, activity grade and other morphological parameters of these landslides. We found huge collapses coincide with traces of active Quaternary faults in this region. However, landslides are clustered being denser splayed in the centre of study area. Furthermore, activity grade of such landslides is higher in this central zone decreasing gradually towards the north and the south. This central area is affected by the Juan Fernandez Ridge which is likely related to higher deformation rate.
Geomorphology, 2018
Rock glaciers are permafrost or glacial landforms of debris and ice that deform under the influen... more Rock glaciers are permafrost or glacial landforms of debris and ice that deform under the influence of gravity. Recent estimates hold that, in the semiarid Chilean Andes for example, active rock glaciers store more water than glaciers. However, little is known about how many rock glaciers might decay because of global warming and how much this decay might contribute to water and sediment release. We investigated an inventory of >6500 rock glaciers in the Argentinian Andes, spanning the climatic gradient from the Desert Andes to cold-temperate Tierra del Fuego. We used active rock glaciers as a diagnostic of permafrost, assuming that the toes mark the 0°C isotherm in climate scenarios for the twenty-first century and their impact on freezing conditions near the rock glacier toes. We find that, under future worst case warming, up to 95% of rock glaciers in the southern Desert Andes and in the Central Andes will rest in areas above 0°C and that this freezing level might move up more than twice as much (~500 m) as during the entire Holocene (~200 m). Many active rock glaciers are already well below the current freezing level and exemplify how local controls may confound regional prognoses. A Bayesian Multifactor Analysis of Variance further shows that only in the Central Andes are the toes of active rock glaciers credibly higher than those of inactive ones. Elsewhere in the Andes, active and inactive rock glaciers occupy indistinguishable elevation bands, regardless of aspect, the formation mechanism, or shape of rock glaciers. The state of rock glacier activity predicts differences in elevations of toes to 140 m at best so that regional inference of the distribution of discontinuous permafrost from rock-glacier toes cannot be more accurate than this in the Argentinian Andes. We conclude that the Central Andes-where rock glaciers are largest, cover the most area, and have a greater density than glaciers-is likely to experience the most widespread disturbance to the thermal regime of the twenty-first century.
Geological Society, London, Special Publications, 2014
This review deals with an integration and update of the knowledge about large-volume landslides i... more This review deals with an integration and update of the knowledge about large-volume landslides in the Central Andes at 32–34°S. An integrated landslide inventory for megalandslides in central Chilean and Argentinean Andean basins was developed, and dispersed chronological data on palaeolandslides were compiled, showing a dominance of Late Pleistocene and Holocene ages. Traditional hypotheses adopted for explaining landslide occurrence in the Central Andes are contrasted. Whereas seismic tremors have been widely suggested as the main triggering mechanism in Chilean collapses, palaeoclimatic conditions are considered as the main cause of Argentinean giant landslides. These different approaches denote the lack of multidisciplinary studies focused on the controversy about seismic or climate trigger mechanisms in the Central Andes. These studies are also essential to understand failure mechanisms and assessment of the related hazard and risk, which are essential to reduce social and eco...
Bulletin of Engineering Geology and the Environment
Relict deposits of a eroded huge Pleistocene rock avalanche were identified in different are-as o... more Relict deposits of a eroded huge Pleistocene rock avalanche were identified in different are-as of middle and lower basin of the Blanco River valley. The rock avalanche source area seems to be the eastern hillslope of the Plata Mount (6,200 m asl), monolithic composition of the de-posits coincides with the Carboniferous rocks outcropping in this sector. We preclude that this catastrophic event should remove and eliminate a pre-existing old glacier from this side of the mount. A recent morphological study evidences this mount face is lacking on uncovered ice bodies contrasting with surrounding areas over the 4,500 m in altitude. Identified relict deposits cover an approximately 64,000 km 2 area with an estimated volume of 32x10 6 m 3 which suggests a huger dimension for the original collapse. Debris material moved down slope 26 km descending topographically 4,400 meters in high. A low angle friction results from these parameters (H/D~0.17). The greenish-grayish deposit presents more ...
DESCRIPTION Conference in Charles University, Prague
Revista del Museo Argentino de Ciencias Naturales, Nueva Serie
Quaternary Research, 2013
Ortega et al. (2012) recently published a study presenting the hydrological regime changes along ... more Ortega et al. (2012) recently published a study presenting the hydrological regime changes along the semiarid coast of Chile (30-32°S) during the early Holocene based on sedimentological, stratigraphical and geomorphological data from Quebrada Santa Julia (QSJ). They suggest a major hydrologic change in the area from arid conditions without heavy rainfall events and local moisture associated to coastal fog to wetter conditions around 8600 cal yr BP, and the onset of modern ENSO influence since 5700 cal yr BP. According to Ortega et al., fine sediment layers (peat, clayed mud and fine sand) at the base of the sequence (13,000-8600 cal yr BP) indicate high humid conditions. They argued that moisture would be local and associated to coastal fogs since the scant presence of alluvial deposits suggests no relation to precipitation. The absence (or scant presence) of alluvial deposits is not enough evidence to point out weak and scarce rainfall events. Pollen records from Los Vilos area (32°S; Fig. 1A) show swamp forests or wetland vegetation, suggesting humid conditions associated with regional precipitation around 13,000 and 10,500-8600 cal yr BP (Villagrán and Varela, 1990; Maldonado and Villagrán, 2006; Maldonado et al., 2009, 2010). Furthermore, the development of this kind of vegetation at QSJ, Quereo and Palo Colorado between 13,000-8600 cal yr BP seems impossible to have been supported only by moisture from coastal fog source. At present, the unique ecosystems supported almost exclusively by fog moisture in the semiarid region of Chile are the early-mid Quaternary relict rainforests but located on particular geomorphological positions, such as the top of coastal mountain ranges over 500 masl where the thermal inversion layer allows the fog condensation (Villagrán et al., 2004; Garreaud et al., 2008). Indeed, relict rainforest survival is not just dependent of water from coastal fog but also from regional precipitation (del-Val et al., 2006). Conversely, our data from isotopic water signal from Los Vilos area support this idea indicating that swamp forests and coastal wetlands water source is not coastal fog but precipitation from inland continent areas about 200 masl (Fig. 1B). On the other hand, similar fine alluvial deposits to those interpreted by Ortega et al. as indicating arid conditions under local moisture due to coastal fog and scarce rainfall events occur today around QSJ. These fine deposits are found today in Los Vilos area in those places where the watertable reaches the surface, keeping the soil moisture year-round and associated with current climate conditions characterized by 180 mm of annual precipitation and periodic torrential rainfalls. It is likely that the absence of alluvial deposits in this part of QSJ before 8600 cal yr BP is related to local geomorphologic features that changed after 8600 cal yr BP, as Ortega et al. suggest for the period after 2800 cal yr BP. Precipitation inferences done by Ortega et al. are based on sediment particle size (clays, limes, sand, etc.) of one profile (column B)
Quaternary Science Reviews, 2015
This paper provides a comprehensive review of the chronostratigraphy of six rock avalanches clust... more This paper provides a comprehensive review of the chronostratigraphy of six rock avalanches clustered in the northern extreme of the Cordon del Plata range. These rock avalanches are stratigraphically related to Pleistocene glacial drifts and valley-fill deposits documenting the regional neotectonic activity. We used cosmogenic dating (TCN) to directly date block surfaces of rock-avalanche deposits, as well as optically stimulated luminescence dating (OSL) of paleo-lakes dammed by these rock avalanches. Our new direct dates (17 TCN and 4 OSL) determine the Middle-to-Late Pleistocene age of these collapses. These are in contrast to the previously established chronostratigraphy based on relative dating techniques, paleontological context, and tephrochronology. These new data help to redefine the geomorphological evolution of the Mendoza River valley. Especially, the new data indicate that the glacial stratigraphy earlier proposed must be reconsidered. We redefine this stratigraphy as far as possible with our data and discuss the data in relation with other recently published results. However, it becomes clear that the glacial history of the Mendoza valley has to be studied anew by using modern dating techniques. In addition, our data suggest that the Carrera Fault system bounding the valleys of the Cordillera del Plata has been active more recently than proposed earlier.
Revista de la Asociacion Geologica Argentina
Developments in Earth Surface Processes, 2009
Research for evaluation of geologic hazards, especially seismic and volcanic, have generally rece... more Research for evaluation of geologic hazards, especially seismic and volcanic, have generally received little attention in Argentina. Nevertheless, the relatively small work done up to the present indicates that a vast field of research has to be developed, not only from the viewpoint of the potential occurrence of an earthquake with destructive force on Argentine territory, but also from the
Engineering Geology for Society and Territory - Volume 1, 2014
Developments in Earth Surface Processes, 2009
This chapter reviews the status of knowledge on landslides in Argentina in order to understand th... more This chapter reviews the status of knowledge on landslides in Argentina in order to understand their behavior and their implications for landscape evolution. This basic understanding allows an analysis of both the vulnerability of mountain communities and the potential risk for regional society and economies.Slope instability processes are analyzed as related to the Argentinean geological provinces. The main landslide processes
Applied Geography, 2013
Archaeology and geomorphology are closely linked in Barrancas, Argentina, where both disciplines ... more Archaeology and geomorphology are closely linked in Barrancas, Argentina, where both disciplines are necessary to understand humaneenvironment interactions during the Holocene. The geomorphology suggests that the area was located in a distal alluvial environment of the Zonda paleo-river that drained to the east. Active tectonics during the Pliocene-Early Pleistocene caused the gradual uplift of the Lunlunta Sierras to the southwest, which led to the bifurcation of the paleo-river. For most of the Holocene, the area was seasonally flooded, suggesting a lacustrine microenvironment. A long record of human occupation beginning in the Early Holocene suggests an extended period of intimate humaneenvironment interactions. Recently, the environment has shifted dramatically. Erosion has created a badlands and significantly impacted the archaeological record. Understanding geomorphological processes is central for archaeological research in general, and especially in Barrancas. This research is an integral part of the ongoing community archaeology program in the area, and for the planned creation of an archaeological reserve.
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Papers by Stella Moreiras