Silicic conduits as supersized tuffisites:Clastogenic influences on shifting eruption styles at Cordón Caulle volcano (Chile)

Understanding the processes that drive explosive-effusive transitions during large silicic eruptions is crucial to hazard mitigation. Conduit models usually treat magma ascent and degassing as a gradual, unidirectional progression from bubble nucleation through magmatic fragmentation. However, there is growing evidence for the importance of bi-directional clastogenic processes that sinter fragmented materials into coherent clastogenic magmas. Bombs that were ejected immediately before the first emergence of lava in the 2011–2012 eruption at Cordón Caulle volcano (Chile) are texturally heterogeneous composite assemblages of welded pyroclastic material. Although diverse in density and appearance, SEM and X-ray tomographic analysis show them all to have been formed by multi-generational viscous sintering of fine ash. Sintering created discrete clasts ranging from obsidian to pumice and formed a pervasive clast-supporting matrix that assembled these clasts into a conduit-sealing plug. An evaluation of sintering timescales reveals texturally disparate bomb components to represent only minutes of difference in residence time within the conduit. Permeability modelling indicates that the plug was an effective conduit seal, with outgassing potential—even from high-porosity regions—being limited by the inability of gas to flow across tendrils of densely sintered inter-clast matrix. Contrary to traditional perspectives, declining expressions of explosivity at the surface need not be preceded or accompanied by a decline in fragmentation efficiency. Instead, they result from tips in balance between the opposing processes of fragmentation and sintering that occur in countless cycles within volcanic conduits. These processes may be particularly enhanced at silicic fissure volcanoes, which have laterally extensive subsurface plumbing systems that require complex magma ascent pathways. The textures investigated here reveal the processes occurring within silicic fissures to be phenomenologically identical to those that have been inferred to occur in tuffisite veins: silicic conduits are essentially supersized examples of edifice-penetrating tuffisites

Alterations in the Interleukin-1/Interleukin-1 Receptor Antagonist Balance Modulate Cardiac Remodeling following Myocardial Infarction in the Mouse

Background Healing after acute myocardial infarction (AMI) is characterized by an intense inflammatory response and increased Interleukin-1 (IL-1) tissue activity. Genetically engineered mice lacking the IL-1 receptor (IL-1R1-/-, not responsive to IL-1) or the IL-1 receptor antagonist (IL-1Ra, enhanced response to IL-1) have an altered IL-1/IL-1Ra balance that we hypothesize modulates infarct healing and cardiac remodeling after AMI. Methods IL-1R1-/- and IL-1Ra-/- male mice and their correspondent wild-types (WT) were subjected to permanent coronary artery ligation or sham surgery. Infarct size (trichrome scar size), apoptotic cell death (TUNEL) and left ventricular (LV) dimensions and function (echocardiography) were measured prior to and 7 days after surgery. Results When compared with the corresponding WT, IL-1R1-/- mice had significantly smaller infarcts (−25%), less cardiomyocyte apoptosis (−50%), and reduced LV enlargement (LV end-diastolic diameter increase [LVEDD], −20%) and dysfunction (LV ejection fraction [LVEF] decrease, −50%), whereas IL-1Ra-/- mice had significantly larger infarcts (+75%), more apoptosis (5-fold increase), and more severe LV enlargement (LVEDD increase,+30%) and dysfunction (LVEF decrease, +70%)(all P values \u3c0.05). Conclusions An imbalance in IL-1/IL-1Ra signaling at the IL-1R1 level modulates the severity of cardiac remodeling after AMI in the mouse, with reduced IL-1R1 signaling providing protection and unopposed IL-1R1 signaling providing harm

Unexpected large eruptions from buoyant magma bodies within viscoelastic crust

Large volume effusive eruptions with relatively minor observed precursory signals are at odds with widely used models to interpret volcano deformation. Here we propose a new modelling framework that resolves this discrepancy by accounting for magma buoyancy, viscoelastic crustal properties, and sustained magma channels. At low magma accumulation rates, the stability of deep magma bodies is governed by the magma-host rock density contrast and the magma body thickness. During eruptions, inelastic processes including magma mush erosion and thermal effects, can form a sustained channel that supports magma flow, driven by the pressure difference between the magma body and surface vents. At failure onset, it may be difficult to forecast the final eruption volume; pressure in a magma body may drop well below the lithostatic load, create under-pressure and initiate a caldera collapse, despite only modest precursors

Halogen (Cl, F) release during explosive, effusive, and intrusive phases of the 2011 rhyolitic eruption at Cordón Caulle volcano (Chile)

We investigate sulphur, chlorine and fluorine release during explosive, effusive and intrusive phases the 2011- 2012 Cordón Caulle eruption, with a focus on the halogens. Analysis of melt inclusions, pyroclasts and lava samples shows most sulphur to have degassed during magma decompression, but halogen release to have accompanied isobaric crystallisation in slowly-cooled magma that was emplaced in a lava flow and sub-vent intrusion. Fluorine in particular mobilised only after extensive groundmass crystallisation and incipient devitrification. By 2017, gas emitted from vent-proximal fumaroles had hydrothermal compositions, with HCl/HF ratios correlating with temperature. We estimate that the eruption could eventually emit up to 0.92 Mt of SO2, 6.3 Mt of HCl, and 1.9 Mt of HF, but only 16 wt.%, 7 wt.% and 2 wt.% of these were respectively emitted during opening explosive phases. Halogen devolatilisation and its associated hazards can persist long after rhyolite eruption and/or emplacement

Iatrogenic coronary dissection: state of the art management

Iatrogenic coronary artery dissections (ICAD) are rare but potentially devastating complications during coronary angiography and percutaneous coronary interventions (PCI). Intima media complex separation may be produced either by the catheter tip or during PCI. Patient characteristics and procedure related risk factors are intimately linked to catheter induced ICAD over diagnostic angiography. Moreover, the increasing complexity of patients undergoing PCI, which frequently involves treatment of heavily calcified or occluded vessels, has increased the likelihood of dissections during PCI. A prompt recognition, along with a prompt management (either percutaneous, surgical or even careful watching), are key in preventing catastrophic consequences of ICAD, such as left ventricular dysfunction, cardiogenic shock, periprocedural myocardial infarction (MI) or cardiac death. This review aims to summarize the main updates concerning the pathophysiology, highlight key risk factors and suggest recommendations in management and treatment of ICAD

Correction to: Silicic conduits as supersized tuffisites: Clastogenic influences on shifting eruption styles at Cordón Caulle volcano (Chile) (Bulletin of Volcanology, (2021), 83, 2, (11), 10.1007/s00445-020-01432-1)

The original version of this article unfortunately contained a mistake. The presentation of Table 1 was incorrect. The corrected table is given below. © 2021, International Association of Volcanology & Chemistry of the Earth's Interior