An asymptomatic 27-year-old physician is diagnosed SARS-CoV-2 by occupational medicine after contagion (RT-PCR).

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Shortening of the continental lithosphere is generally accommodated by the growth of crustal wedges building above megathrusts in the mantle lithosphere. We show that the locus of shortening in the western margin of South America has largely been controlled by the geometry of the slab. Numerical models confirm that horizontal subduction favors compression far from the trench, above the asthenospheric wedge and steeply dipping segment of the subducting slab. As a result, a second crustal wedge grows in the hinterland of the continent, and widens the Andes. In the Bolivian orocline, this wedge corresponds to the Eastern Cordillera, whose growth was triggered by a major episode of horizontal subduction. When the slab returned to a steeper dip angle, shortening and uplift pursued, facilitated by the structural and thermo-chemical alteration of the continental lithosphere. We review the successive episodes of horizontal subduction that have occurred beneath South America at different latitudes and show that they explain the diachronic widening of the Andes. We infer that the present-day segmented physiography of the Andes results from the latitudinally variable, transient interplay between slab dynamics and upper plate tectonics over the Cenozoic. We emphasize that slab flattening, or absence thereof, is a major driving mechanism that sets the width of the Andes, at any latitude.

[1] Absolute plate motion models with respect to a deep mantle reference frame (e.g., hot spots) typically contain some net rotation (NR) of the lithosphere. Global mantle flow models for the present-day plate setting reproduce similarly oriented NRs but with amplitudes significantly smaller than those found in some high NR Pacific hot spot reference frames. It is therefore important to understand the mechanisms of NR excitation, which we attempt here with two-dimensional cylindrical models of an idealized Pacific domain. We study the influence of slab properties, oceanic ridge position, continental keels, and a weak asthenospheric layer on NR and trench migration. Fast slab return flow develops in models with stiff slabs and moderate slab dips. Rapid NRs, comparable to the high NR Pacific hot spot reference frames, are Copyright 2012 by the American Geophysical Union 1 of 23 primarily induced by asymmetric slab dips, in particular a shallow slab beneath South America and a steep slab in the western Pacific. A scaling relationship links the amplitude of NR to plate size, slab dip angle, and slab viscosity. Asymmetric ridge positions also promote NR through asymmetric plate sizes. Continental keels have less impact, in contrast to what has been found in earlier global studies. Several models yield unidirectional Pacific trench motions, such as slab advance in the western Pacific and, simultaneously, slab retreat in the eastern Pacific. Our model provides a physical explanation for NR generation in the present-day Pacific setting and hints at mechanisms for the temporal evolution of the basin.

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Topography above subduction zones arises from the isostatic contribution of crustal and lithospheric buoyancy, as well as the dynamic contribution from slab‐driven mantle flow. We evaluate those effects in southwestern Mexico, where a segment of the Cocos slab subducts horizontally. The eastern part of the volcanic arc—the Trans‐Mexican Volcanic Belt—stands at an average elevation of 2.3 km, nearly 1.3 km above the fore‐arc. Lateral changes in bulk crustal density are relatively small, and seismic imaging shows that there is little variation in crustal thickness between these two regions. Thus, the elevation difference between the arc and the fore‐arc should arise from differences in mantle properties. We present finite element models of flat‐slab subduction that provide a simultaneous match to topography, plate velocities, and stress state in the overriding plate. We find that the dynamic effects are primarily controlled by the amount of coupling at the subduction interface and in the mantle wedge, the lack of slab anchoring into the lower mantle, and the absence of continental mantle lithosphere. With a mantle wedge and a subduction interface that are, respectively, 2 and 4 orders of magnitude weaker than the asthenosphere, the flat slab exerts a downward pull that can explain most of the elevation difference between the fore‐arc and the arc. We infer that lateral viscosity variations play a significant role in shaping dynamic topography in complex tectonic settings and that sublithospheric dynamics can influence the topography at wavelengths that are significantly shorter than previously recognized.

Abstract. Sexist behaviour in the workplace contributes to create a hostile environment, hindering the chance of women and gender non-conforming individuals to pursue an academic career, but also reinforcing gender stereotypes that are harmful to their progress and recognition. The Did this really happen?! project aims at publishing real-life, everyday sexism in the form of comic strips. Its major goal is to raise awareness about unconscious biases that transpire in everyday interactions in academia and increase the visibility of sexist situations that arise within the scientific community, especially to those who might not notice it. Through the website didthisreallyhappen.net, we collect testimonies about everyday sexism occurring in the professional academic environment (universities, research institutes, scientific conferences…). We translate these stories into comics and publish them anonymously without any judgement or comments on the website. By now, we have collected over 100 testimonies. From this collection, we identified six recurrent patterns: (1) behaviours that aim at maintaining women in stereotypical feminine roles, (2) behaviours that aim at maintaining men in stereotypical masculine roles, (3) the questioning of the scientific skills of female researchers, (4) situations where women have the position of an outsider, especially in informal networking contexts, (5) the objectification of women, and (6) the expression of neosexist views. We first present a detailed analysis of these categories, then we report on the different ways we interact and engage with the Earth science community, the scientific community at large and the public in this project.