Explosive Volcanic Eruptions Research Articles

The Influence of Internal Climate Variability on Stratospheric Water Vapor Increases After Large‐Magnitude Explosive Tropical Volcanic Eruptions

AbstractSubstantial and prolonged enhancements in stratospheric water vapor (SWV) have occurred after large‐magnitude explosive tropical volcanic eruptions, with modified tropopause entry caused by aerosol‐absorptive heating. Here, we analyze the timing and longevity of heating‐driven post‐eruption SWV changes within CMIP6‐VolMIP short‐term climate‐response experiments with the UK Earth System Model (UKESM1). We find aerosol‐absorptive heating causes peak SWV increases of 17% (∼1 ppmv) and 10% (0.5 ppmv) at 100 and 50 hPa, at ∼18 and ∼23 months after a Pinatubo‐like eruption, respectively. We track the temperature response in the tropical lower stratosphere and identify the main SWV increase occurs only after the descending aerosol heating reaches the tropopause, suggesting a key role for aerosol microphysical processes (sedimentation rate). We explore how El Niño–Southern Oscillation variability modulates this effect. Post‐eruption SWV increases are ∼80% stronger for the La Nina phase compared to the ensemble mean. Tropical upwelling strongly mediates this effect.

The Effect of Conduit Walls Roughness on Volcanic Jets and Their Seismo‐Acoustic Radiation: An Experimental Investigation

AbstractTo explore the effect of conduit roughness on volcanic jet dynamics and on the related seismo‐acoustic radiation we performed a series of shock‐tube experiments using pipes with variable inner surface fractal dimension D. Variable starting pressure produced subsonic to supersonic jets visualized using high‐speed shadowgraph and recorded with an array of accelerometers and microphones. At all starting pressures, increasing D increases the energy transfer from the gas to the conduit walls, decreasing the jet exit velocity (Mach number) and, for supersonic cases, the related shock‐cell spacing, and increasing the seismic to acoustic radiation amplitude ratio. The roughness‐induced changes in jet velocity and turbulence affect the dominant sources of the jet noise and modulates the spectral properties of the acoustic signals. From our study we show that conduit wall roughness is an important and yet largely neglected factor in the dynamics of explosive volcanic eruptions and their monitored geophysical signals.

Excess explosivity driven by melt inclusions during the 946 CE Plinian eruption of Baekdusan

Melt inclusions readily rupture and form gas bubbles during explosive volcanic eruptions, but their role as a volcanic gas source remains enigmatic. Here, we examined a pumice texture generated by the instantaneous bursting of melt inclusions during the 946 CE Plinian eruption at Baekdusan. The burst produced non-sheared, super-vesicular (>80 vol.% voids) bubble pockets, occupying volume fractions of 6–24% within the Millennium gray pumice. The bubble pocket texture suggests that the melt inclusions acted as an additional volcanic gas source that increased the volume of the erupting magma at the moment of magma fragmentation. Two distinctive feldspar–glass assemblages of either sanidine-bearing trachyte or anorthoclase-bearing rhyolite in the bubble pockets indicate that the chemical bimodality of the hemisphere-scale, 946 CE Baekdusan tephra resulted from cryptic mixing of two magmas. The excess explosivity induced by the bursting melt inclusions should be considered when modeling eruption dynamics and assessing volcanic hazards, therefore having broad volcanological implications.

Effects of debris entrainment and recycling on explosive volcanic eruption jets and columns

Effects of debris entrainment and recycling on explosive volcanic eruption jets and columns

Emergency shelters fleeing La Soufrière: a case study from the April 2021 volcanic eruption in St Vincent and the Grenadines

Abstract La Soufrière, St Vincent is the northernmost stratovolcano on mainland St Vincent. Over 25 000 residents were issued orders to evacuate their homes in the high-risk zones close to the La Soufrière Volcano in St Vincent and the Grenadines because of the imminent explosive volcanic eruption. The aim of this paper is to explore the experiences of residents who evacuated and sought shelter as a result of the 2021 eruption of La Soufrière Volcano. The researchers conducted surveys of affected residents of the red and orange zones (evacuees and non-evacuees) as well as shelter volunteers. The results indicate that residents are willing to evacuate if they are provided with information to guide their decision-making and if they feel that they have a suitable place to stay and that they are likely to receive support, especially food supplies. Despite their willingness to evacuate, people are generally concerned about the safety and security of their house, crops and livestock. In relation to future eruptions, people would be more prepared if they received more information, were evacuated earlier and took more supplies with them when they were evacuated.

Modeling Wind‐Blown Umbrella Clouds in Lagrangian Dispersion Models

AbstractThe ash and gas released by large explosive volcanic eruptions rises to its neutral buoyancy level in the atmosphere, then spreads laterally to form an umbrella cloud. Density stratification of the atmosphere generates buoyancy forces in the cloud, which drive the outward spread. Although umbrella clouds are often modeled as circular axisymmetric structures, in practice they are usually influenced quite strongly by the meteorological wind, with spread in the upwind direction halted by the oncoming wind, and different rates of spreading in the downwind and crosswind directions. In this work, we derive a simple parametrization of non‐axisymmetric umbrella cloud spreading from a much more complex physically based shallow‐layer intrusion model. The new parametrization is quick to evaluate and so is suitable for use in operational Volcanic Ash Transport and Dispersion Models (VATDMs). In contrast to previous parametrizations, in which there is assumed to be no interaction between a circular umbrella cloud and the meteorological wind, here the umbrella cloud is influenced by the wind and adopts a shape determined by the balance of buoyant spreading and downwind drag forces. We apply the new scheme to four historical case studies of eruptions at Puyehue 2011, Pinatubo 1991, Ulawun 2019, and Calbuco 2015. The results are compared with VATDM simulations using a conventional circular umbrella cloud parametrization. Using the new scheme, good descriptions of cloud spread are recovered and the prediction of horizontal ash distribution is improved relative to the axisymmetric parametrization.

Atmosphere injection of sea salts during large explosive submarine volcanic eruptions

The 15 January 2022 submarine eruption at Hunga volcano was the most explosive volcanic eruption in 140 years. It involved exceptional magma and seawater interaction throughout the entire submarine caldera collapse. The submarine volcanic jet breached the sea surface and formed a subaerial eruptive plume that transported volcanic ash, gas, sea salts and seawater up to ~ 57 km, reaching into the mesosphere. We document high concentrations of sea salts in tephra (volcanic ash) collected shortly after deposition. We also discuss the potential climatic consequences of large-scale injection of salts into the upper atmosphere during submarine eruptions. Sodium chloride in these volcanic plumes can reach extreme concentrations, and dehalogenation of chlorides and bromides poses the risk of long-term atmospheric and weather impact. Salt content in rapidly collected tephra samples may also be used as a proxy to estimate the water:magma ratio during eruption, with implications for quantification of fragmentation efficiency in submarine breaching events. The balance between salt loading into the atmosphere versus deposition in ash aggregates is a key factor in understanding the atmospheric and climatic consequences of submarine eruptions.

Volcanic Imprints in Last-Millennium Land Summer Temperatures in the Circum–North Atlantic Area

Abstract Summer cooling is one of the most direct consequences of explosive volcanic eruptions that can affect ecosystems and human societies. Recent studies revealed a multiyear cooling impact on hemispheric and global summer temperatures after tropical eruptions, yet the volcanic responses appear to vary on regional scales. Here, we revisit volcano-induced summer cooling in eastern Canada and northern and central Europe by applying superposed epoch analysis on CMIP6-PMIP4 simulations and millennial temperature reconstructions based on tree-ring density. We then examine potential causes modulating region-specific volcanic impact. While confirming that, on average, tropical eruptions over the last millennium have induced a longer cooling (>4 yr) than eruptions from extratropical Northern Hemisphere in all three North Atlantic regions, we show that the peak magnitude of cooling is stronger in eastern Canada. We also find that the detected volcanic temperature anomalies can be strongly affected by the selection and number of volcanic events and nonvolcanic signals embedded in the climate time series. This study highlights the risks of using highly noisy proxy records to investigate volcanic impacts, especially in regions with strong unforced climate variability. The CMIP6-PMIP4 simulations generally agree with the three reconstructions on the average response to tropical eruptions, but their performance is poorer regarding the production of significant cooling after extratropical eruptions. Our results further suggest that the particular sensitivity to tropical eruptions in eastern Canada is likely related to increased sea ice surrounding Quebec–Labrador associated with the positive Arctic Oscillation and North Atlantic Oscillation formed during the first posteruption winter.

A One‐Dimensional Volcanic Plume Model for Predicting Ash Aggregation

AbstractDuring explosive volcanic eruptions, volcanic ash is ejected into the atmosphere, impacting aircraft safety and downwind communities. These volcanic clouds tend to be dominated by fine ash (<63 μm in diameter), permitting transport over hundreds to thousands of kilometers. However, field observations show that much of this fine ash aggregates into clusters or pellets with faster settling velocities than individual particles. Models of ash transport and deposition require an understanding of aggregation processes, which depend on factors like moisture content and local particle collision rates. In this study, we develop a Plume Model for Aggregate Prediction, a one‐dimensional (1D) volcanic plume model that predicts the plume rise height, concentration of water phases, and size distribution of resulting ash aggregates from a set of eruption source parameters. The plume model uses a control volume approach to solve mass, momentum, and energy equations along the direction of the plume axis. The aggregation equation is solved using a fixed pivot technique and incorporates a sticking efficiency model developed from analog laboratory experiments of particle aggregation within a novel turbulence tower. When applied to the 2009 eruption of Redoubt Volcano, Alaska, the 1D model predicts that the majority of the plume is over‐saturated with water, leading to a high rate of aggregation. Although the mean grain size of the computed Redoubt aggregates is larger than the measured deposits, with a peak at 1 mm rather than 500 μm, the present results provide a quantitative estimate for the magnitude of aggregation in an eruption.

BOOM! Tephrochronological dataset and exploration tool of the Southern (33–46° S) and Austral (49–55° S) volcanic zones of the Andes

Tephrochronology studies the deposits of explosive volcanic eruptions in the stratigraphic record. The Southern (SVZ, 33–46° S) and Austral (AVZ, 49–55° S) Volcanic Zones of the Andes are two very active volcanic zones where tephrochronology is of great use. There, it can be used to improve chronologies of paleoenvironmental records in Patagonia, an area providing valuable records at global scale; as well as to identify areas likely to be affected by volcanic eruptions in the future, essential for producing volcanic hazard maps. The close proximity of many volcanic centers with recurrent explosive activity, which have very similar geochemical compositions, and very often poor age constraints, represent a challenge for the study of tephrochronology in the region. In addition to this, the ever-growing amount of tephrochronological information in the area, dispersed in different types of publications which vary greatly in format, makes the integration of the data produced by different actors, and consecutively its interpretation, increasingly difficult. Here we address this issue by compiling the BOOM! dataset, which integrates ∼30 years of research on 32 active volcanic centers and 132 different eruptions, which took place during the last 20,000 years. To help users find and reuse data in the large dataset, we developed an online platform which provides user-friendly tools for exploring it, and helps users download subsets of it. To integrate this very heterogeneous information, special attention was given to include information which allows users to evaluate data quality and comparability, as well as to provide tools in the explorer for users to filter data by different criteria. The integration of this dataset opens new perspectives for the development of novel visualizations of tephrochronological data, for example, to better understand the multidimensional uncertainties associated with it. For example, uncertainties associated with analytical precision, with age estimates of both tephra deposits and volcanic eruptions, and of tephra classification. Additionally, it allows for the use of robust statistical tools to correlate tephra deposits, including those based on machine learning algorithms, which are here explored.

Impacts on water transport networks after three widespread volcanic ashfalls in Andean Patagonian lakes

Although the impacts of volcanic ashfall on air transport and land transport networks are well documented, little information exists about volcanic ash effects on water transport. Three recent widespread ashfall events severely affected the extensive shipping activity that takes place in the many lakes of Andean Patagonia, Argentina. By means of impact assessment fieldtrips, meetings, semi-structured interviews, and expert consultation, we surveyed and categorized impacts of volcanic ash on ships, ports and shipping activities, also assessing most effective mitigation strategies undertaken, including clean-up actions. To better catalogue type and severity of impacts, we expand on available damage scales developed for critical infrastructure, to include more specific details about water transport systems. Our contribution ultimately aims to communicate to emergency managers, and the volcanological and nautical communities, the most likely outcomes from explosive volcanic eruptions on shipping, along with best-practice advice for mitigating adverse effects.

Mobility and emplacement of an ancient, large-volume pyroclastic flow, Ongatiti Ignimbrite, North Island, New Zealand

Pyroclastic flows are the most devastating phenomena of explosive volcanic eruptions. These hazardous fast-moving, hot, concentrated density currents are able to travel several tens of kilometers radially away from their source. Due to an enveloping ash cloud, it is still impossible to directly study pyroclastic flows. However, their deposits (i.e., ignimbrites) provide useful insight into their internal processes of emplacement. This study focuses on the Ongatiti Ignimbrite, which is sourced from Mangakino caldera (i.e., the oldest volcanic centre in the Taupo Volcanic Zone, North Island, New Zealand dated at 1600–950 ka) and offers a unique opportunity to understand the emplacement processes of an ancient and large-volume pyroclastic flow. It is a welded to non-welded, columnar-jointed, cliff-forming deposit, that has been divided into nine facies based on the variation in pumice and lithic clast abundance, and degree of welding.Our results constrain the minimum deposit volume for the Ongatiti Ignimbrite to ca. 1400 km3, or 1000 km3 dense-rock equivalent. Zircon (UTh)/He data suggest an eruption age of 1.37 ± 0.04 Ma, which is in good agreement with the previous proposed eruption age. The topographic controls on the spatial distribution of the ignimbrite have been determined to understand pyroclastic flow pathways through valleys and over hills. The ignimbrite covered hills up to ∼900 m (about 650 m above the caldera height) to around 40 km from the Mangakino volcanic center (MVC) and, the pyroclastic flow travelled to beyond 90 km from the vent. The Ongatiti Ignimbrite was a landscape-modifying event that covered at least the western North Island and as far away as Auckland and Wellington.

Earthquakes Record Cycles of Opening and Closing in the Enhanced Seismic Catalog of the 2008 Okmok Volcano, Alaska, Eruption

AbstractSeismicity during explosive volcanic eruptions remains challenging to observe through the eruptive noise, leaving first‐order questions unanswered. How do earthquake rates change as eruptions progress, and what is their relationship to the opening and closing of the eruptive vent? To address these questions for the Okmok Volcano 2008 explosive eruption, Volcano Explosivity Index 4, we utilized modern detection methods to enhance the existing earthquake catalog. Our enhanced catalog detected significantly more earthquakes than traditional methods. We located, relocated, determined magnitudes and classified all events within this catalog. Our analysis reveals distinct behaviors for long‐period (LP) and volcano‐tectonic (VT) earthquakes, providing insights into the opening and closing cycle. LP earthquakes occur as bursts beneath the eruptive vent and do not coincide in time with the plumes, indicating their relationship to an eruptive process that occurs at a high pressurization state, that is, partially closed conduit. In contrast, VT earthquakes maintain a steadier rate over a broader region, do not track the caldera deflation and have a larger b‐value during the eruption than before or after. The closing sequence is marked by a burst of LPs followed by small VTs south of the volcano. The opening sequence differs as only VTs extend to depth and migrate within minutes of the eruption onset. Our high‐resolution catalog offers valuable insights, demonstrating that volcanic conduits can transition between partially closed (clogged) and open (cracked) states during an eruption. Utilizing modern earthquake processing techniques enables clearer understanding of eruptions and holds promise for studying other volcanic events.

Impact of a strong volcanic eruption on the summer middle atmosphere in UA-ICON simulations

Abstract. Explosive volcanic eruptions emitting large amounts of sulfur can alter the temperature of the lower stratosphere and change the circulation of the middle atmosphere. The dynamical response of the stratosphere to strong volcanic eruptions has been the subject of numerous studies. The impact of volcanic eruptions on the mesosphere is less well understood because of a lack of large eruptions in the satellite era and only sparse observations before that period. Nevertheless, some measurements indicated an increase in mesospheric mid-latitude temperatures after the 1991 Pinatubo eruption. The aim of this study is to uncover potential dynamical mechanisms that may lead to such a mesospheric temperature response. We use the Upper-Atmospheric ICOsahedral Non-hydrostatic (UA-ICON) model to simulate the atmospheric response to an idealized strong volcanic injection of 20 Tg S into the stratosphere (about twice as much as the eminent 1991 Pinatubo eruption). Two experiments with differently parameterized effects of sub-grid-scale orography are compared to test the impact of different atmospheric background states. The simulations show a significant warming of the polar summer mesopause of up to 15–21 K in the first November after the eruption. We argue that this is mainly due to intrahemispheric dynamical coupling in the summer hemisphere and is potentially enhanced by interhemispheric coupling with the winter stratosphere. This study focuses on the first austral summer after the eruption because mesospheric temperature anomalies are especially relevant for the properties of noctilucent clouds, whose season peaks around January in the Southern Hemisphere.

Cu-Ag-Au Microspherules in Igneous Rocks: Morphology, Composition, Diagnostic Criteria and Possible Origin

Igneous rocks from the Russian Far East contain Cu-Ag-Au microspherules with distinct exterior and interior structures, compositions and assemblages of Cu-rich micro-inclusions. Natural microspherules are compared in this study with technogenic Cu-Ag-Au microspherules, which are experimentally produced and extracted from gold scrap jewelry. The following set of diagnostic criteria are considered to distinguish natural from technogenic microspherules on a genetic basis as follows: (1) compacted-related features versus cellular appearance of the exterior; (2) lack of exsolution- or crystallization-related features in natural and domain-type internal structure in technogenic microspherules; (3) absence of spherical copper-oxide inclusions along with meniscus-type textural boundaries in technogenic mcirospherules; (4) pure copper-oxide composition of inclusions versus the common presence of Fe, Ni, Zn, Cu and Na in natural microspherules. The diagnostic characteristics of natural Cu-Ag-Au microspherules suggest extremely fast cooling rates during their formation, which is possible during violent explosive volcanic eruptions or injection of partially molten, pulverized metal alloys into shallow intra-crustal cavities and fault-related tectonic gashes.

Sedimentary response to the early Silurian (Rhuddanian-Aeronian) post-glacial transgression and Kwangsian Orogeny in the Upper Yangtze region, South China

Unlike the lowermost Silurian ‘hot’ shales deposited in many other regions of the world, the early Silurian (Rhuddanian-Aeronian) succession in South China exhibits a distinctive lithofacies transition from organic-rich black siliceous mudstone in the early Rhuddanian, to interlaminated siltstone and mudstone with relatively low total organic carbon content in the late Rhuddanian, and finally to organic-lean argillaceous mudstone or calcareous mudstone in the late Aeronian. The interlaminated siltstone and mudstone interval has been the subject of a long-standing dispute over its nature, whether it belongs to turbidite or contourite. In this study, we employed a range of approaches, including petrographic analyses, UPb dating of detrital zircons, and measurements of paleocurrent directions to generate a dataset that reveals: (1) four typical fine-grained facies developed within the interlaminated siltstone and mudstone interval, (2) detrital zircon UPb ages yielding a wide age range from Archean (∼2.50 Ga) to early Paleozoic (0.42 Ga), with a predominant peak of ca. 447 Ma based on 516 detrital zircon UPb analyses, and (3) paleocurrent directions indicate the presence of current circulation in the Upper Yangtze region. The results of this study demonstrated that the detritus of the interlaminated siltstone and mudstone interval originated from concurrent explosive volcanic eruptions along the southeastern margin of the South China Craton. It was deposited and reworked by bottom currents under the background of the early Silurian post-glacial transgression. We suggest that the occurrence of the interlaminated siltstone and mudstone interval is indicative of a far-field sedimentary response to the onset and progradation of the Kwangsian Orogeny in the Upper Yangtze region.

Impact assessment caused by bradyseism phenomena in the Campi Flegrei area

Campi Flegrei (Italy) is among the areas with the greatest volcanic explosive risk in the world due to the dangerousness of the expected hazards, the high exposed value (about 500,000 people will be evacuated during the “alarm phase”), and the vulnerability of the urban settlements under the effect of the volcanic phenomena. The last two dramatic bradyseism phases occurred in 1969–1972 and 1982–1984 when Pozzuoli town was affected by rapid ground inflation, which brought an overall higher level of about 3.5 m and caused numerous earthquakes (M ≤ 4.2), with severe damage to buildings. During 1984, the seismicity was intense, with 33 events with 0.5 < M ≤ 3 and six with 3 < M ≤ 3.8. Subsequently, the Campi Flegrei caldera was characterized by general subsidence for about 20 years until 2005, when a new inflation period started and is still ongoing (∼1 m). The areal distribution of the recent uplift is characterized by the maximum vertical displacement in the town of Pozzuoli, with a radial decrease from the caldera center outwards. The need to better understand Campi Flegrei volcanic activity is fundamental to protecting the population from hazards linked to explosive volcanic eruptions and understanding the role of seismicity as a possible precursor of a potential eruption. In this perspective, as part of the activities of the PLINIVS Study Centre (Centre of Competence of Italian Civil Protection Department for Volcanic Risk), the authors developed a procedure, implemented in a web application, that relates the monitoring of the ground deformation with the behavior of buildings to evaluate the level of progressive damage to the ordinary Phlegraean buildings due to bradyseism in near real time. This study describes the models adopted for the three impact/risk factors (hazard, exposure, and vulnerability) used to estimate building damage.

A Specific Earthquake Processing Workflow for Studying Long‐Lived, Explosive Volcanic Eruptions With Application to the 2008 Okmok Volcano, Alaska, Eruption

AbstractBy providing unrivaled resolution in both time and space, volcano seismicity helps to chronicle and interpret eruptions. Standard earthquake detection methods are often insufficient as the eruption itself produces continuous seismic waves that obscure earthquake signals. We address this problem by developing an earthquake processing workflow specific to a high‐noise volcanic environment and applying it to the explosive 2008 Okmok Volcano eruption. This process includes applying single‐channel template matching combined with machine‐learning and fingerprint‐based techniques to expand the existing earthquake catalog of the eruption. We detected an order of magnitude more earthquakes, then located, relocated, determined locally calibrated magnitudes, and classified the events in the enhanced catalog. This new high‐resolution earthquake catalog increases the number of observations by about a factor of 10 and enables the detailed spatiotemporal seismic analysis during a large eruption.

Mechanisms of hydrological responses to volcanic eruptions in the Asian monsoon and westerlies-dominated subregions

Abstract. Explosive volcanic eruptions affect surface climate, especially in monsoon regions, but responses vary in different regions and to volcanic aerosol injection (VAI) in different hemispheres. Here, we use six ensemble members from the last-millennium experiment of the Coupled Model Intercomparison Project Phase 5 to investigate the mechanisms of regional hydrological responses to different hemispheric VAIs in the Asian monsoon region (AMR). Northern hemispheric VAI (NHVAI) leads to an intensified aridity over the AMR after northern hemispheric VAI (NHVAI); spatially, a distinct inverse response pattern to the climatological conditions emerges, with an intensified aridity in the relatively wettest area (RWA) but a weakened aridity in the relatively driest area (RDA) of the AMR. Southern hemispheric VAI (SHVAI) shows a weakened aridity over the AMR, but the spatial response pattern is not that clear due to small aerosol magnitude. The mechanism of the hydrological impact relates to the indirect change of atmospheric circulation due to the direct radiative effect of volcanic aerosols. The decreased thermal contrast between the land and the ocean after NHVAI results in a weakened East Asian summer monsoon and South Asian summer monsoon. This changes the moisture transport and cloud formation in the monsoon and westerlies-dominated subregions. The subsequent radiative effect and physical feedbacks of local clouds lead to different hydrological effects in different areas. Results here indicate that future volcanic eruptions may temporarily alleviate the uneven distribution of precipitation in the AMR, which should be considered in the near-term climate predictions and future strategies of local adaptation to global warming. The local hydrological responses and mechanisms found here can also provide a reference for stratospheric aerosol engineering.

Sensitivity of stratospheric ozone to the latitude, season, and halogen content of a contemporary explosive volcanic eruption

We present a systematic evaluation of the perturbation to the stratosphere from an explosive volcanic eruption injecting sulfur dioxide into the atmosphere, as a function of latitude, season, and injection gas halogen content in a chemistry-climate state representative of the present day (modeled as year 2025). Enhancements in aerosol surface area density and decreases in stratospheric ozone are observed for a period of years following all modeled scenarios, with volcanic eruptions near the equator impacting both hemispheres relatively equally, and eruptions at higher latitudes reducing the thickness of the ozone layer more substantially in the hemisphere of the eruption. Our simulations reveal that there that are significant seasonal differences when comparing the stratospheric impact of a volcanic eruption occurring in summer versus winter, and this holds true regardless of whether volcanic halogen gases (Cl, Br) are co-injected with sulfur dioxide. If an explosive halogen-rich eruption were to occur, there would be substantial ozone losses in both hemispheres, regardless of latitude or season, with recovery potentially exceeding 4 years.