Supereruption Research Articles

Can the Artificial Release of Fluorinated Gases Offset Global Cooling Due to Supervolcanic Eruptions?

Large volcanic eruptions, such as the prehistoric Yellowstone eruption, induce abrupt global cooling—by some estimates at a rate of ~1 °C/year, lasting for more than a decade. An abrupt global cooling of several °C—even if only lasting a few years—would present immediate, drastic stress on biodiversity and food production. This cooling poses a global catastrophic risk to human society beyond the immediate and direct impact of eruptions. Using a simple climate model, this paper discusses the possibility of counteracting large volcanic cooling with the intentional release of greenhouse gases. Longer-lived compounds (e.g., CO2 and CH4) are unsuitable for this purpose, but selected fluorinated gases (F-gases), either individually or in combinations, could be released at gigaton scale to offset large volcanic cooling substantially. We identify candidate F-gases (e.g., C4F6 and CH3F) and derive radiative and chemical properties of ‘ideal’ compounds matching specific cooling events. Geophysical constraints on manufacturing and stockpiling due to mineral availability are considered, alongside technical and economic implications based on present-day market assumptions. The effects and uncertainty due to atmospheric chemistry related to aerosol injection, F-gases release, and solar dimming are discussed in the context of large volcanic perturbation. The caveats and future steps using more complex chemistry–climate models are discussed. Despite the speculative nature of the magnitude and composition of F-gases, our conceptual analysis has implications for testing the possibility of mitigating certain global catastrophic cooling risks (e.g., nuclear winter, asteroid impact, and glacier transition) via intentional intervention.

Neutralisation of Acid Rock Drainage by Youngest Toba Tuff Leachate Revealed by Hydrogeochemistry

ABSTRACTThe Youngest Toba Tuff (YTT) supervolcanic eruption occurred 75000 years ago, and resulted in distinctive ash fall deposition in different locations encompassing marine, estuarine, lacustrine, and fluvial sedimentary basins. Of the different sedimentary basins, the YTT crypto‐tephra horizon preserved in the South Kerala Sedimentary Basin (SKSB) of the western coast of India is hosted by a paleo‐estuarine carbonaceous clay layer. Along the eastern margin of SKSB, confined aquifers hosting highly acidic groundwater is associated with this YTT ash and associated organic matter (OM)‐rich carbonaceous clay layer, creating worse acid rock drainage (ARD), which eventually gets neutralised during summer, signalled by the crystallisation of halotrichite. Hydrogeological investigation gave insights on some of the unique geochemical processes, which facilitated the neutralisation of ARD. The main aquifers in the area include laterite and clayey‐sand, which is separated by this impervious layer hosting YTT ash. Wells tapping the clayey‐sand aquifer, beneath this layer, is affected by the ARD condition due to the interaction with pyrite, manifested as low pH of groundwater (3.7). Simultaneously, leaching from YTT ash, which constitutes 11.91% of Al2O3, facilitates Al content to reach groundwater in high concentration (2879.97 ppb). During dry season, when the surface of YTT‐hosting OM‐rich carbonaceous clay layer is exposed, the leached Al interacts with the acid derived from the YTT‐hosting OM‐rich carbonaceous clay layer and results in the precipitation of halotrichite. The two processes, one resulting in ARD condition and the other as formation of halotrichite, occur in succession. Thus, the crystallisation of halotrichite signals the neutralisation of water as well as heralding the potability of water.

The Impact of Abrupt Sunlight Reduction Scenarios on Renewable Energy Production

To combat global warming, energy systems are transitioning to generation from renewable sources, such as wind and solar, which are sensitive to climate conditions. While their output is expected to be little affected by global warming, wind, and solar electricity generation could be affected by more drastic climatic changes, such as abrupt sunlight reduction scenarios (ASRSs) caused by nuclear war (“nuclear winter”) or supervolcanic eruptions (“volcanic winter”). This paper assesses the impacts of an ASRS on global energy supply and security in a 100% renewable energy scenario. National generation mixes are determined according to roadmaps for a global transition to renewable energy, with wind and solar contributing a combined 94% of the global energy supply. Wind and solar generation are determined for a baseline climate and an ASRS following a large-scale nuclear exchange. While effects vary by country, overall wind and solar generation are expected to reduce by 59% in the first year following an ASRS, requiring over a decade for full recovery. Ensuring sufficient energy for everyone’s critical needs, including water, food, and building heating/cooling, would require international trade, resilient food production, and/or resilient energy sources, such as wood, geothermal, nuclear power, tidal power, and hydropower.

Resilience of Snowball Earth to Stochastic Events

AbstractEarth went through at least two periods of global glaciation (i.e., “Snowball Earth” states) during the Neoproterozoic, the shortest of which (the Marinoan) may not have lasted sufficiently long for its termination to be explained by the gradual volcanic build‐up of greenhouse gases in the atmosphere. Large asteroid impacts and supervolcanic eruptions have been suggested as stochastic geological events that could cause a sudden end to global glaciation via a runaway melting process. Here, we employ an energy balance climate model to simulate the evolution of Snowball Earth's surface temperature after such events. We find that even a large impactor (diameters of d ∼ 100 km) and the supervolcanic Toba eruption (74 Kyr ago), are insufficient to terminate a Snowball state unless background CO2 has already been driven to high levels by long‐term outgassing. We suggest, according to our modeling framework, that Earth's Snowball states would have been resilient to termination by stochastic events.

A pre-Campanian Ignimbrite techno-cultural shift in the Aurignacian sequence of Grotta di Castelcivita, southern Italy

The Aurignacian is the first European technocomplex assigned to Homo sapiens recognized across a wide geographic extent. Although archaeologists have identified marked chrono-cultural shifts within the Aurignacian mostly by examining the techno-typological variations of stone and osseous tools, unraveling the underlying processes driving these changes remains a significant scientific challenge. Scholars have, for instance, hypothesized that the Campanian Ignimbrite (CI) super-eruption and the climatic deterioration associated with the onset of Heinrich Event 4 had a substantial impact on European foraging groups. The technological shift from the Protoaurignacian to the Early Aurignacian is regarded as an archaeological manifestation of adaptation to changing environments. However, some of the most crucial regions and stratigraphic sequences for testing these scenarios have been overlooked. In this study, we delve into the high-resolution stratigraphic sequence of Grotta di Castelcivita in southern Italy. Here, the Uluzzian is followed by three Aurignacian layers, sealed by the eruptive units of the CI. Employing a comprehensive range of quantitative methods—encompassing attribute analysis, 3D model analysis, and geometric morphometrics—we demonstrate that the key technological feature commonly associated with the Early Aurignacian developed well before the deposition of the CI tephra. Our study provides thus the first direct evidence that the volcanic super-eruption played no role in this cultural process. Furthermore, we show that local paleo-environmental proxies do not correlate with the identified patterns of cultural continuity and discontinuity. Consequently, we propose alternative research paths to explore the role of demography and regional trajectories in the development of the Upper Paleolithic.

Severe Global Cooling After Volcanic Super-Eruptions? The Answer Hinges on Unknown Aerosol Size

Abstract Volcanic super-eruptions have been theorized to cause severe global cooling, with the 74 kya Toba eruption purported to have driven humanity to near-extinction. However, this eruption left little physical evidence of its severity and models diverge greatly on the magnitude of post-eruption cooling. A key factor controlling the super-eruption climate response is the size of volcanic sulfate aerosol, a quantity that left no physical record and is poorly constrained by models. Here we show that this knowledge gap severely limits confidence in model-based estimates of super-volcanic cooling, and accounts for much of the disagreement among prior studies. By simulating super-eruptions over a range of aerosol sizes, we obtain global mean responses varying from extreme cooling all the way to the previously unexplored scenario of widespread warming. We also use an interactive aerosol model to evaluate the scaling between injected sulfur mass and aerosol size. Combining our model results with the available paleoclimate constraints applicable to large eruptions, we estimate that global volcanic cooling is unlikely to exceed 1.5°C no matter how massive the stratospheric injection. Super-eruptions, we conclude, may be incapable of altering global temperatures substantially more than the largest Common Era eruptions. This lack of exceptional cooling could explain why no single super-eruption event has resulted in firm evidence of widespread catastrophe for humans or ecosystems. Significance Statement Whether volcanic super-eruptions pose a threat to humanity remains a subject of debate, with climate models disagreeing on the magnitude of global post-eruption cooling. We demonstrate that this disagreement primarily stems from a lack of constraint on the size of volcanic sulfate aerosol particles. By evaluating the range of aerosol size scenarios, we demonstrate that eruptions may be incapable of causing more than 1.5°C cooling no matter how much sulfur they inject into the stratosphere. This could explain why archaeological records provide no evidence of increased human mortality following the Toba super-eruption. Further, we raise the unexplored possibility that the largest super-eruptions could cause global-scale warming.

Population genomic analysis reveals distinct demographics and recent adaptation in the black flying fox (Pteropus alecto)

As the only mammalian group capable of powered flight, bats have many unique biological traits. Previous comparative genomic studies in bats have focused on long-term evolution. However, the micro-evolutionary processes driving recent evolution are largely under-explored. Using resequencing data from 50 black flying foxes (Pteropus alecto), one of the model species for bats, we find that black flying fox has much higher genetic diversity and lower levels of linkage disequilibrium than most of the mammalian species. Demographic inference reveals strong population fluctuations (>100 fold) coinciding with multiple historical events including the last glacial change and Toba super eruption, suggesting that the black flying fox is a very resilient species with strong recovery abilities. While long-term adaptation in the black flying fox is enriched in metabolic genes, recent adaptation in the black flying fox has a unique landscape where recently selected genes are not strongly enriched in any functional category. The demographic history and mode of adaptation suggest that black flying fox might be a well-adapted species with strong evolutionary resilience. Taken together, this study unravels a vibrant landscape of recent evolution for the black flying fox and sheds light on several unique evolutionary processes for bats comparing to other mammalian groups.

Methane Single Cell Protein: Potential to Secure a Global Protein Supply Against Catastrophic Food Shocks.

Global catastrophes such as a supervolcanic eruption, asteroid impact, or nuclear winter could cause global agricultural collapse due to reduced sunlight reaching the Earth’s surface. The human civilization’s food production system is unprepared to respond to such events, but methane single cell protein (SCP) could be a key part of the solution. Current preparedness centers around food stockpiling, an excessively expensive solution given that an abrupt sunlight reduction scenario (ASRS) could hamper conventional agriculture for 5–10 years. Instead, it is more cost-effective to consider resilient food production techniques requiring little to no sunlight. This study analyses the potential of SCP produced from methane (natural gas and biogas) as a resilient food source for global catastrophic food shocks from ASRS. The following are quantified: global production potential of methane SCP, capital costs, material and energy requirements, ramp-up rates, and retail prices. In addition, potential bottlenecks for fast deployment are considered. While providing a more valuable, protein-rich product than its alternatives, the production capacity could be slower to ramp up. Based on 24/7 construction of facilities, 7%–11% of the global protein requirements could be fulfilled at the end of the first year. Despite significant remaining uncertainties, methane SCP shows significant potential to prevent global protein starvation during an ASRS at an affordable price—US$3–5/kg dry.

Forest Resource Availability After Nuclear War or Other Sun‐Blocking Catastrophes

AbstractA global, sun‐blocking catastrophe like nuclear war, an asteroid strike, or a super volcano eruption spells disaster for most aspects of life as we know it. There have been many studies on how differing magnitudes of sun‐blocking catastrophes would affect the global climate, and many mention the effects of this cold, dark climate on forests and cropping systems. However, few studies have solely focused on the effects of nuclear winter on forests in terms of food, resources, and decomposition. Forests already provide over a billion people with food and fuel for their livelihoods. In this review, we connect how prehistoric catastrophes affected the world's forests to how a current‐day catastrophe may affect forest health, forest resource availability, and wood decomposition rates. We briefly discuss how forest resources may be used in this post‐catastrophe climate for food and fuel in an energy and fuel‐depleted world. We use this information to make policy and education suggestions to prepare for future catastrophes, build resilience from smaller local disasters, prepare for the many effects of climate change, and discourage nuclear weapon stockpiles.

Legacy of supervolcanic eruptions on population genetic structure of brown kiwi

Supervolcanoes are volcanoes capable of mega-colossal eruptions that emit more than 1,000km3 of ash and other particles.1 The earth's most recent mega-colossal eruption was the Oruanui eruption of the Taupo supervolcano 25,580 years before present (YBP) on the central North Island of New Zealand.2 This eruption blanketed major swaths of the North Island in thick layers of ash and igneous rock,2,3 devastating habitats and likely causing widespread population extinctions.4-7 An additional devastating super-colossal eruption (>100km3) of the Taupo supervolcano occurred approximately 1,690 YBP.8 The impacts of such massive but ephemeral natural disasters on contemporary population genetic structure remain underexplored. Here, we combined data for 4,951 SNPs with spatially explicit demographic and coalescent models within an approximate Bayesian computation framework to test the drivers of genetic structure in brown kiwi (Apteryx mantelli). Our results strongly support the importance of eruptions of the Taupo supervolcano in restructuring pre-existing geographic patterns of population differentiation and genetic diversity. Range shifts due to climatic oscillations-a frequent explanation for genetic structure9-are insufficient to fully explain the empirical data. Meanwhile, recent range contraction and fragmentation due to historically documented anthropogenic habitat alteration adds no explanatory power to our models. Our results support a major role for cycles of destruction and post-volcanic recolonization in restructuring the population genomic landscape of brown kiwi and highlight how ancient and ephemeral mega-disasters may leave a lasting legacy on patterns of intraspecific genetic variation.

Toward a New Theory of Earth Crustal Displacement

Snapshot/Lay Summary—In 1958 Charles Hapgood proposed that mass imbalances created by a buildup of polar ice could displace the earth’s crust over the mantle and that resulting pole shifts were the cause of catastrophic climate changes and ice ages. We contrast the first part of his theory with plate tectonics and true polar wander and propose a new mechanism that is triggered by short-term reversals of the geomagnetic field that “unlock” the crust from the mantle, driven by earth–moon–sun tidal forces, the same forces that move earth’s oceans. It is shown that by combining a modified version of the second part of Hapgood’s theory with elements of existing climate theories it may be possible to account for periodic sea-level changes associated with the buildup and melting of polar ice over past glacial cycles with a combination of Milanković cycles and Hapgood pole shifts.
 
 Abstract—In previous studies of more than two hundred archaeological sites, it was discovered that the alignments of almost half of the sites could not be explained, and about 80% of the unexplained sites appear to reference four locations within 30° of the North Pole. Based on their correlation with Hapgood’s estimated positions of the North Pole over the past 100,000 years, we proposed that, by association, sites aligned to these locations could be tens to hundreds of thousands of years old. That such an extraordinary claim rests on Hapgood’s unproven theory of earth crustal displacement/pole shifts is problematic, even given the extraordinary number of aligned sites (more than several hundred) that have been discovered thus far. Using a numerical model we test his hypothesis that mass imbalances in the crust due to a buildup of polar ice are sufficient to displace the crust to the extent required in his theory. We discover in the process that the crust is not currently in equilibrium with the whole earth in terms of its moments of inertia. Based on a review of the literature that reveals a possible connection between the timing of short-term reversals of the geomagnetic field (geomagnetic excursions), super-volcanic eruptions, and glacial events, we hypothesize that crustal displacements might be triggered by geomagnetic excursions that “unlock” the crust from the mantle to the extent that available forces, specifically earth–moon–sun tidal forces, the same forces that move earth’s oceans, can displace the crust over the mantle. It is demonstrated how such a model, when combined with existing climate change theory, may be able to explain periodic changes in sea level associated with the buildup and melting of polar ice over past glacial cycles by a combination of Milanković cycles and Hapgood pole shifts.

A universal severity classification for natural disasters

The magnitude of a disaster’s severity cannot be easily assessed because there is no global method that provides real magnitudes of natural disaster severity levels. Therefore, a new universal severity classification scheme for natural disasters is developed and is supported by data. This universal system looks at the severity of disasters based on the most influential impact factor and gives a rating from zero to ten: Zero indicates no impact and ten is a worldwide devastation. This universal system is for all types of natural disasters, from lightning strikes to super-volcanic eruptions and everything in between, that occur anywhere in the world at any time. This novel universal severity classification system measures, describes, compares, rates, ranks, and categorizes impacts of disasters quantitatively and qualitatively. The severity index is useful to diverse stakeholder groups, including policy makers, governments, responders, and civilians, by providing clear definitions that help convey the severity levels or severity potential of a disaster. Therefore, this universal system is expected to avoid inconsistencies and to connect severity metrics to generate a clear perception of the degree of an emergency; the system is also expected to improve mutual communication among stakeholder groups. Consequently, the proposed universal system will generate a common communication platform and improve understanding of disaster risk, which aligns with the priority of the Sendai Framework for Disaster Risk Reduction 2015–2030. This research was completed prior to COVID-19, but the pandemic is briefly addressed in the discussion section.

Rapid repurposing of pulp and paper mills, biorefineries, and breweries for lignocellulosic sugar production in global food catastrophes

Producing sugar from lignocellulosic biomass is a promising resilient food solution to counter the near-total global failure of food production due to the agricultural collapse that would likely follow an abrupt sunlight reduction catastrophe such as a nuclear winter, a supervolcanic eruption, or a large asteroid or comet impact.This study examines how quickly edible sugar production could be ramped up globally by repurposing pulp and paper mills, sugarcane biorefineries, corn biorefineries, and breweries for lignocellulosic sugar production. A sub-unit component comparison to the NREL 2017 Biochemical Sugar Model indicates that 84%, 65%, 37%, and 39% of ISBL unit components are present, respectively. Fast construction methods were studied to analyze how this and other industrial foods could be rapidly leveraged in a catastrophe.Results suggest that the world’s current sugar demand could quickly be fulfilled by repurposing pulp and paper mills for lignocellulosic sugar production, given 5 months of production ramp-up and 24/7 construction. This method could reduce construction time to an estimated 32% of the original at an increased labor cost of 1.47 times, resulting in sugar production beginning 5 months after the catastrophe at a retail cost of $0.82 USD/kg. This could not only contribute a significant share of the food requirement after the catastrophe (∼28% within the first year), but also be key to preventing global starvation between the time at which global food storages run dry and other resilient food solutions can scale up significantly.This study aims to serve as the basis for more comprehensive scenario analyses. More research is needed to characterize material and labor constraints to fast response in more depth; repurposing and fast construction pilot studies and food safety studies are recommended.

Refining models of archaic admixture in Eurasia with ArchaicSeeker 2.0

We developed a method, ArchaicSeeker 2.0, to identify introgressed hominin sequences and model multiple-wave admixture. The new method enabled us to discern two waves of introgression from both Denisovan-like and Neanderthal-like hominins in present-day Eurasian populations and an ancient Siberian individual. We estimated that an early Denisovan-like introgression occurred in Eurasia around 118.8–94.0 thousand years ago (kya). In contrast, we detected only one single episode of Denisovan-like admixture in indigenous peoples eastern to the Wallace-Line. Modeling ancient admixtures suggested an early dispersal of modern humans throughout Asia before the Toba volcanic super-eruption 74 kya, predating the initial peopling of Asia as proposed by the traditional Out-of-Africa model. Survived archaic sequences are involved in various phenotypes including immune and body mass (e.g., ZNF169), cardiovascular and lung function (e.g., HHAT), UV response and carbohydrate metabolism (e.g., HYAL1/HYAL2/HYAL3), while “archaic deserts” are enriched with genes associated with skin development and keratinization.

Synthetic fat from petroleum as a resilient food for global catastrophes: Preliminary techno-economic assessment and technology roadmap

Human civilization’s food production system is unprepared for global catastrophic risks (GCRs). catastrophes capable of abruptly transforming global climate such as supervolcanic eruption, asteroid/comet impact or nuclear winter, which could completely collapse the agricultural system. Responding by producing resilient foods requiring little to no sunlight is more cost effective than increasing food stockpiles, given the long duration of these scenarios (6−10 years).This preliminary techno-economic assessment uncovers significant potential for synthetic fat from petroleum as a resilient food source in the case of an abrupt sunlight reduction catastrophe, the most severe food shock scenario. To this end, the following are roughly quantified based on literature data: global production potential, capital and operating expenditures, material and energy requirements, ramp-up rates and retail prices. Potential resource bottlenecks are reviewed.Synthetic fat production capacity would be slower to ramp up compared to low-tech food production alternatives, but provides the fat macronutrient, largely absent from these. Using 24/7 construction of facilities, 16–100% of global fat requirements could be fulfilled at the end of the first year, potentially taking up to 2 years to fully meet the requirements. Significant uncertainty remains on several topics including production potential, capital expenditure, food safety, transferability of labor and equipment construction. A technology roadmap is proposed to address these concerns and develop the potential of synthetic fat as a catastrophe-resilient food.

Fast melt expulsion from crystal-rich mushes via induced anisotropic permeability

Catastrophic eruptions of rhyolitic super volcanoes require large volumes of silicic magma to be extracted from a crystal-rich mush at high rates. However, fast melt extraction is thought to be difficult because of the low permeability of mushes and the high viscosities of silicic melts. Here, we show that induced ephemeral high permeability pathways in the mush may be critical. During uniaxial compression of the mush, driven by the impingement of recharging magmas from below, melt within the mush can be redistributed preferentially into vertical melt pockets. This redistribution of melt can increase vertical permeability by a factor of 10-100 times, which leads to rapid expulsion of melt. As melt is expelled, the permeability rapidly declines. The end result is a fast, short-lived pulse of melt extraction that can grow a 1 km thick silicic magma reservoir in 10 kyr. Our analysis shows how the incursion of deep-seated magmas into the base of a crystal-rich mush in the crust can trigger the expulsion of silicic melts that may lead to an eruption.

Focal Palatitis (Previously Focal Palatine Erosions) in Captive Cheetahs (Acinonyx jubatus)

Focal palatine erosion (FPE) is a misleading term that is used in the literature to describe inflammatory lesions associated with depressions of the palatal mucosa in cheetah. Cheetahs have large cheek teeth and these depressions are formed to accommodate them. Previously FPE was only described as a mandibular molar tooth malocclusion on the hard palate due to suspected rotation and super eruption of the mandibular molar teeth of cheetahs aged 18 months and older. Two hundred and fifty six cheetahs (135 male, 121 female), originating from two independent facilities, had their oral cavities evaluated as part of an annual health visit over a decade. Ninety-nine cheetahs were seen once, 59 cheetahs were seen twice, 33 were seen three times, 43 on four occasions, 16 on five occasions, 5 on six occasions, and 1 cheetah was seen seven times. Apart from these clinical cases a prospective study on 5 cheetah cubs (3 male and 2 female) was conducted to document their skull development and mandibular molar tooth eruption over a period of 25 months. Of the 261 cheetahs observed none developed rotation or super eruption of their mandibular molar teeth. The term FPE is a misnomer as these inflammatory lesions were found in palatal depressions opposing any of the cusps of all of the cheetah mandibular cheek teeth. It consisted mainly of deep ulcerations, inflammation and oedema and also micro abscess formation. In severe cases oro-nasal fistulas were present. Of all the depressions present on the cheetah's palate, the large one palatal to the 4th maxillary premolar tooth was most commonly affected. In the five cubs evaluated prospectively, focal palatitis was evident from the 7 month evaluation, before all the permanent teeth erupted. Conservative treatment of the inflamed depressions by removing the foreign material through curettage and copious flushing reduced the grade of the inflammation when observed on follow-up. Focal palatine erosion is an incorrect term used to describe focal palatitis that occurs randomly in cheetahs. This focal palatitis is often associated with foreign material trapped in the palatal depressions. Conservative management is sufficient to treat these animals without odontoplasties.

A modelling approach to the investigation of the effects of the Minoan supervolcanic eruption on Aegean sand fly diversity

The late Bronze Age eruption of the Thera volcano was among the largest eruptions of the Holocene era. This catastrophic event might perish all organisms from the ancient Santorini and could seriously impact the sand fly fauna of the Aegean islands. To investigate these effects, the survival possibility of the sand fly fauna in the Santorini islands and the biogeographic investigation of the sand fly fauna of eleven Aegean islands were conducted. It was found that only the south and east slopes of the massifs of Thira could provide refuge for sand fly populations. The expression-based heat map of the Jaccard coefficient matrix data showed that the Santorini islands and their neighbouring Anafi, Folegandros had clearly different z-score patterns compared to the other islands. It could be a late sign of the devastating effect of the Minoan eruption and/or the consequence of the distance of these islands from the mainland. Neither the glacial seashore patterns nor the geographic-climatic conditions can explain the present sand fly fauna of the Aegean Archipelago. If the sand fly populations of ancient Santorini survived the Minoan cataclysm, it could indicate that the environmental tolerance and the resilience of the sand fly populations can be high, and local geological and geomorphological conditions can play a greater role in the survival of sand fly species than previously assumed.

Decadal Disruption of the QBO by Tropical Volcanic Supereruptions

AbstractThe Los Chocoyos (14.6°N, 91.2°W) supereruption happened ∼75,000 years ago in Guatemala and was one of the largest eruptions of the past 100,000 years. It emitted enormous amounts of sulfur, chlorine, and bromine, with multi‐decadal consequences for the global climate and environment. Here, we simulate the impact of a Los Chocoyos‐like eruption on the quasi‐biennial oscillation (QBO), an oscillation of zonal winds in the tropical stratosphere, with a comprehensive aerosol chemistry Earth System Model. We find a ∼10‐year disruption of the QBO starting 4 months post eruption, with anomalous easterly winds lasting ∼5 years, followed by westerlies, before returning to QBO conditions with a slightly prolonged periodicity. Volcanic aerosol heating and ozone depletion cooling leads to the QBO disruption and anomalous wind regimes through radiative changes and wave‐mean flow interactions. Different model ensembles, volcanic forcing scenarios and results of a second model back up the robustness of our results.

The Geometry of the Subducted Slab Beneath Sumatra Revealed by Regional and Teleseismic Traveltime Tomography

AbstractThe geometry of the subducted Indo‐Australian plate beneath Sumatra is still controversial because of the historical lack of a dense seismic network. Since 2005, Indonesia has been establishing a relatively dense seismic network for real time earthquake monitoring and tsunami warning. The seismic data accumulated by this network make it possible to achieve high‐resolution tomographic images of the velocity structure beneath Sumatra by using eikonal equation‐based seismic tomography method. Our P‐wave tomographic images derived from regional seismic and teleseismic traveltime data demonstrate that the slab in the upper mantle generally follows the strike of the trench and the orientation of the volcanic arc. Additionally, the slab exhibits a sinusoidal shape with a low degree of curvature. Our tomographic results also reveal that the maximum penetration depth of the subducted slab increases from the north to south. The subducted slab beneath the northern tip of Sumatra barely arrives at the 410‐km discontinuity, while the slab in the south penetrates to a depth of at least 660 km. Our inversion further indicates that the subducted slab is characterized by a tear at a depth of 120 km between 0° N and 2° N, which may be closely related to the supervolcanic eruption of the Toba caldera in northern Sumatra during the Pleistocene. Moreover, we report that the dip of the subducted slab varies significantly (i.e., dramatically decreases) across the Sunda Strait; therefore, we infer that another subvertical slab tear exists beneath the Sunda Strait.