Dense Rock Equivalent Research Articles

The 2019 pumice raft forming eruption of Volcano-F (Volcano 0403–091) and implications for hazards posed by submerged calderas

Low volcanic explosivity index (VEI) eruptions are common occurrences in the Southwest Pacific but, as demonstrated by the 2021/2022 eruption of Hunga Volcano, submerged calderas in the region are also capable of producing much larger and more hazardous eruptions. As such, characterising smaller events from potentially hazardous systems is essential. The 2019 eruption of Volcano-F, a submerged caldera, would likely have gone totally undetected had it not produced a pumice raft that inundated beaches in Fiji and eventually washed up in Australia. New data, acquired 5 months after the eruption, reveal the development of a new vent and the accumulation of at least 3.1*107 m3 bulk volume (dense rock equivalent of 5.6*106 m3) of material on the seafloor. Between 30 and 70% of erupted material entered the raft, while the rest remained near to or was dispersed down-current of the vent. This previously unaccounted for material increases the volume estimate for the eruption, confirming it as a VEI 3 event and highlights the importance of considering not just the floating component of a pumice raft forming eruption for VEI estimation. Geochemical analysis reveals the eruption comprised a homogenous batch of dacitic magma, with compositional characteristics similar to that erupted from the same volcano in 2001, and an until-now-unidentified pumice raft in the Coral Sea in 1964. Volcano-F therefore appears to have had at least three explosive eruptions in the last 60 years, indicating it is significantly at unrest. Repeated eruptions of similar composition and low crystal content magma over decadal to centennial scales indicate the existence of a melt-dominant magma body beneath the volcano. Submerged calderas, like Volcano-F, are common in the wider Southwest Pacific region, with many such calderas producing regular eruptions, implicating active magmatic recharge. Our findings motivate a need to carefully monitor and characterise even apparently small eruptions at this volcano, and others along the Tonga-Kermadec Arc. This is because such eruptions have the potential to subsequently prime or trigger more explosive eruptions and provide critical geochemical evidence about the plumbing system and evolution of the volcano, essential for understanding the diverse hazards they pose.

Disparate impacts of the Eldgjá and Laki flood-lava eruptions

The Eldgjá eruption of ~ 939 AD is recognised as the largest in Iceland since Settlement, and ranks among the largest late-Holocene volcanic episodes on Earth. It disgorged > 21.0 km3 (Dense Rock Equivalent) of magma as lava flows (~ 19.7 km3) and tephra deposits (> 1.3 km3 DRE), comprising alternating phreatomagmatic (wet) and magmatic (dry) explosive phases. Tephra deposits up to four metres thick buried proximal areas, and extreme quantities of sulphur and other volatiles were released into the atmosphere. Little is known about the environmental and societal impacts of the eruption within Iceland as it took place during the initial decades of human settlement, and before written record-keeping in Iceland became prevalent. In this work, we review what is known of the Eldgjá eruption, making comparisons with the better documented Laki eruption of 1783–1784 AD (~ 15.1 km3 DRE). While the Eldgjá eruption was volumetrically greater, probably longer-lasting, and involved phreatomagmatic explosive phases, we reason that societal resilience to volcanic hazards was likely stronger in the 10th century compared with the 18th, reflecting differences in social and natural capital in Iceland. Accordingly, the impacts of the Eldgjá eruption cannot be inferred reliably from knowledge of the Laki episode and its aftermath.

Applications of ArcticDEM for measuring volcanic dynamics, landslides, retrogressive thaw slumps, snowdrifts, and vegetation heights

Topographical changes are of fundamental interest to a wide range of Arctic science disciplines faced with the need to anticipate, monitor, and respond to the effects of climate change, including geohazard management, glaciology, hydrology, permafrost, and ecology. This study demonstrates several geomorphological, cryospheric, and biophysical applications of ArcticDEM – a large collection of publicly available, time-dependent digital elevation models (DEMs) of the Arctic. Our study illustrates ArcticDEM's applicability across different disciplines and five orders of magnitude of elevation derivatives, including measuring volcanic lava flows, ice cauldrons, post-failure landslides, retrogressive thaw slumps, snowdrifts, and tundra vegetation heights. We quantified surface elevation changes in different geological settings and conditions using the time series of ArcticDEM. Following the 2014–2015 Bárðarbunga eruption in Iceland, ArcticDEM analysis mapped the lava flow field, and revealed the post-eruptive ice flows and ice cauldron dynamics. The total dense-rock equivalent (DRE) volume of lava flows is estimated to be (1431 ± 2) million m3. Then, we present the aftermath of a landslide in Kinnikinnick, Alaska, yielding a total landslide volume of (400 ± 8) × 103 m3 and a total area of 0.025 km2. ArcticDEM is further proven useful for studying retrogressive thaw slumps (RTS). The ArcticDEM-mapped RTS profile is validated by ICESat-2 and drone photogrammetry resulting in a standard deviation of 0.5 m. Volume estimates for lake-side and hillslope RTSs range between 40,000 ± 9000 m3 and 1,160,000 ± 85,000 m3, highlighting applicability across a range of RTS magnitudes. A case study for mapping tundra snow demonstrates ArcticDEM's potential for identifying high-accumulation, late-lying snow areas. The approach proves effective in quantifying relative snow accumulation rather than absolute values (standard deviation of 0.25 m, bias of −0.41 m, and a correlation coefficient of 0.69 with snow depth estimated by unmanned aerial systems photogrammetry). Furthermore, ArcticDEM data show its feasibility for estimating tundra vegetation heights with a standard deviation of 0.3 m (no bias) and a correlation up to 0.8 compared to the light detection and ranging (LiDAR). The demonstrated capabilities of ArcticDEM will pave the way for the broad and pan-Arctic use of this new data source for many disciplines, especially when combined with other imagery products. The wide range of signals embedded in ArcticDEM underscores the potential challenges in deciphering signals in regions affected by various geological processes and environmental influences.

The Cerro Guacha Caldera complex, SW Bolivia: A long-lived, multicyclic, resurgent caldera complex in the Altiplano-Puna Volcanic Complex of the Central Andes

Measuring ∼50 × 30 km, the Cerro Guacha Caldera Complex (CGCC) is a polycyclic, nested caldera complex within the Altiplano Puna Volcanic Complex (APVC) of the Central Andes. Previous work had established that CGCC was built in three stages. Catastrophic supereruptions of the 1300 km3 (DRE - Dense Rock Equivalent) Guacha ignimbrite at ca. 5.65 Ma and the 800 km3 (DRE) Tara ignimbrite at ca. 3.49 Ma resulted in two nested caldera collapses that define the first two stages (G1C and G2C) of the CGCC. The third stage, G3C, initiated ∼1.8 Ma with the eruption of the Puripica Chico ignimbrite and associated lavas. The only previous detailed systematic study of the CGCC was of the G2C (Grocke et al., 2017a, 2017b). In this work we provide new field, petrochemical and geochronological data on the first and third cycles that now allow us to present the first comprehensive account of the eruption history, as well as the magmatic and volcanological evolution of the CGCC as a long-lived caldera complex.Erupted compositions during the G1C and G3C cycles are dominantly high-K, calc-alkaline dacites and minor andesites and these fall within the andesite to rhyolite compositional array previously defined for the G2C. In the CGCC as a whole, dacitic compositions account for over 90% of the ∼2200 km3 of magma erupted. These data reveal a consistency of magma composition, storage and evolution throughout the >4 Ma history of the CGCC.New UPb in zircon ages reveal distinct zircon age distributions that indicate that each caldera cycle represented new magmatic cycles that accumulated 10's to 100's of thousands of years prior to eruption. We find zircon antecrysts in all eruptive stages which we interpret as assimilation of non-erupted progenitors of earlier magmatic cycles. Occassional zircon xenocrysts and cores are interpreted as assimilation of upper crustal basement lithologies, supporting previous interpretations of upper crustal open system magmatic evolution for the G2C to the entire CGCC.Both the G1C and G2C calderas are west-hinged trap-door style collapses. Of these, the 5.65 Ma G1C caldera measures ∼50 km × 30 km, whereas the 3.49 Ma G2C is 30 × 20 km and is nested within the G1C. Resurgent uplift in both the calderas reveals at least a kilometer thickness of intracaldera ignimbrite. Outflow ignimbrites from the CGCC extend 100 km N-S and 40 km E-W around CGCC and were topographically limited. Intracaldera ignimbrite volume dominates outflow volumes by a ratio of ∼5:1. Repose periods between successive stages are now calculated to be 2.1 (G1C to G2C) and 1.8 (G2C to G3C) Myr respectively.The evolution of the CGCC parallels other APVC calderas and is closely linked to the history of the APVC flare-up. The two supereruptions at 5.65 Ma (Guacha Ignimbrite) and 3.49 Ma (Tara Ignimbrite) coincide with the peak of the flare-up and its eruptive and magmatic tempo correlate with the regional tempo. The eruptive and magmatic histories connote a composite granodioritic subcaldera pluton of significant extent accumulated in the upper crust beneath the CGCC.

Radiocarbon dating, magnitude, and catastrophic impact of Popocatépetl's Terminal Preclassic “Lorenzo pumice” Plinian eruption and paleomagnetic age constraints on the Nealtican lava flow field (central Mexico)

The “Lorenzo pumice” (LP) fallout was produced by a Plinian (VEI = 4) eruption of Popocatépetl volcano ∼40 cal BCE during the Terminal Preclassic period. It is part of a pyroclastic sequence that consists in stratigraphic order of fall, pyroclastic density current, and lahar deposits, which in turn are partly covered by the 70 km2 andesitic-dacitic “Pedregal de Nealtican” lava flow field on the eastern slope of the volcano.The composition of the pumice varies insignificantly (SiO2 = 61.0 to 63.5 wt%) with phenocrysts of euhedral plagioclase > orthopyroxene > clinopyroxene ± olivine ± hornblende ± opaques.Sizes of lithics and the isopach map indicate an eruption column height of ∼28 km and a dispersal axis toward the ENE, where an area of ∼600 km2 that included pre-Hispanic dispersed villages was buried under >10 cm of pumice. The minimum volume for the LP fallout was calculated at ∼0.6 km3 corresponding to ∼0.2 km3 of dense rock equivalent (DRE).The short Plinian phase ended when the column collapsed abruptly, generating lethal pyroclastic density currents that were emplaced around the volcano. It was followed by periodic flooding by rain lahars that originated from the slopes of Popocatépetl and from neighboring Iztaccíhuatl, severely affecting ravines and large portions of the plains of Puebla in the east.After the cataclysmic phase, the El Ombligo vent alignment opened at ∼4000 m a.s.l. on Popocatépetl's NE upper slope from which the lavas that form the Nealtican lava flow field emanated, an effusive activity that lasted >30 years. Paleomagnetic data for these lavas and stratigraphic evidence indicate that the lava flows with a total volume of 4.2 km3 were emplaced shortly after the explosive Plinian phase and represent the degassed portion of the LP magma.This eruption had a considerable impact on pre-Hispanic settlements around the volcano, whose population exodus and relocation probably contributed to the rise of important cities in central Mexico, such as Teotihuacán, Cholula, and Cantona.

The post-2016 long-lasting Vulcanian activity of Sabancaya volcano (Peru) and associated aeolian remobilisation of volcanic ash

The characterisation of tephra deposits resulting from almost simultaneous sedimentation and wind remobilisation is complex, and multidisciplinary strategies are required in order to accurately constrain associated processes and eruptive parameters. We present a multifaceted study that aims to characterise the recent eruptive activity and the subsequent aeolian remobilisation of tephra deposits at Sabancaya volcano (Peru), which started erupting in November 2016 with frequent and relatively small explosions (plume heights <6 km above the vent). First, we estimated the bulk volume of tephra deposit produced between November 2016 and August 2018 at 0.04 ± 0.02 km3, and the dense rock equivalent (DRE) volume at 0.02 ± 0.01 km3. This corresponds to a tephra production rate of 1.1 ± 0.5 × 10−3 km3 DRE per month. Second, continuous sampling in a dedicated tephra collector network between April 2018 and November 2019 allowed estimation of the tephra volume at 2.3 ± 1.1 × 10−5 km3 DRE per month, indicating a significant decrease in the mass eruption rate since 2018. Third, by characterising the pulsatory activity through the repose interval between explosions and magma characteristics, Sabancaya's activity was classified as Vulcanian. Finally, aeolian remobilisation phenomena were studied using high-resolution videos, measurements of the airborne concentration of particulate matter with a diameter of ≤10 μm (PM10) and particle physical characterisation. Subtle morphological differences are identified between remobilised particles and those in primary deposits, and we found that particles moving at ground level and above 1.5 m have grainsizes transportable by saltation and suspension, respectively.

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.

Geomorphological Classification of Monogenetic Volcanoes and Its Implication to Tectonic Stress Orientation in the Middle Atlas Volcanic Field (Morocco)

The Middle Atlas Volcanic Field (MAVF) covers an area of 1500 km2, with a total erupted volume of solid products (e.g., Dense Rock Equivalent or DRE) estimated to be more than 80 km3. The MAVF comprises 87 monogenetic basaltic volcanoes of Tertiary-Quaternary age as scoria cones (71%) and maars (29%). These monogenetic basaltic volcanoes have various morphologies (e.g., circular, semi-elliptic, elliptic in map views). They can be isolated or form clustered monogenetic complexes. They are largely grouped in the Middle Atlas, in an intraplate geotectonic context forming two distinct major alignments (N160–170° and N40–50°), each closely associated with regional structural elements. By the best estimates, the preserved bulk pyroclastic products do not exceed 0.7 km3, and they show large textural and componentry diversity (e.g., bedded/unbedded, coarse/fine, dense/scoriaceous fallout and pyroclastic density current deposit, etc.). Lava flows also demonstrate great variety of preserved surface textures, including pāhoehoe, ‘a’ā, and clastogenic types. Morphostructural features of lava flows linked to lava flow dynamics have also been recognized, and the presence of hornitos, columnar jointed basaltic flow units, lava tubes, tumuli, and clastogenic lava flows have been recognized and mapped. Some half-sectioned dykes expose interior parts of magmatic shallow feeding pipes. The current morphology of the volcanoes of the MAVF reflects various syn- and post-eruptive processes, including (1) erosional features due to weathering, (2) gravitational instability during and after volcanic activity, (3) vegetation impact, and (4) successive burial of lava flows. The documented volcanic features of this typical monogenetic volcanic field form the core of the region’s geoheritage elements and are considered to be unique in the new African geoheritage context. Hence, they will likely form the basis of future geotourism, geoeducation, and geoconservation ventures.

Lava deltas, a key landform in oceanic volcanic islands: El Hierro, Canary Islands

Marine and subaerial erosion of volcanic ocean islands form coastal cliffs and shore platforms, particularly during stable sea levels. Posterosional lava flows can spill over these coastal cliffs and fill the platforms, leading to the progradation of lava deltas. This work aims to analyze this volcanic rocky coast setting at the island scale and to assess the volcanic constructional and erosive degradational effects on the coast at the scale of one volcanic edifice. El Hierro Island, Canary Islands, exemplifies a rocky coast with an active sea-cliff profile, reflecting its early evolutionary stage as a young ocean volcanic island with no fringing reef. The occurrence of a contemporary insular shelf formed during the Holocene sea-level highstand (<7 ka) allows constraining the ages of those eruptions forming lava deltas affecting this geomorphological landform. A detailed bathymetry around the island allowed us to distinguish 17 eruptions fulfilling this criterion. The Montaña del Tesoro, which occurred about 1050 years BP, is one of these eruptions and was selected as a case study for morphometric modeling integrating subaerial and submarine data at the scale of a volcanic edifice. This eruption was a Strombolian basaltic volcanic event that produced a scoria cone, pyroclastic fall deposits, and lava flows that reached the ocean in the eastern rift zone of El Hierro island. We combine field-based observations with topographic and bathymetric data analysis to reconstruct the pre- and post-eruption Digital Elevation Models (DEMs) and, comparing with present-day DEM, to analyze morphometrically the influence of volcanism on the coastal landscape's development. The resulting landform complexity required the discretization of the lava field according to the coastline evolution and lava front sectors, and the subaerial or submarine lava placement. The pyroclastic materials' total erupted bulk volume (12,829,578 m3) corresponds to a volcanic eruption index (VEI) of 3. This event was primarily effusive. From a dense rock equivalent (DRE) volume of 25,615,424 m3, 87 % flowed as lava, 10 % formed the cinder cone, and 3 % the tephra fall deposits. We quantitatively demonstrate that dominant degradation occurs in the lava field, mainly disturbed by marine erosion. Marine erosion removed 9 % of the erupted volume of lava flows against 1 % by fluvial erosion. This work provides methods and results of great interest with different implications in oceanic volcanic islands, among which we can mention coastal planning (e.g., rock coast evolution) and volcanic risk assessment (e.g., the importance of Holocene sea-level rise on the development of shore platforms facilitating the progradation of lava deltas).

Volcanic ash, victims, and tsunami debris from the Late Bronze Age Thera eruption discovered at Çeşme-Bağlararası (Turkey)

The Late Bronze Age Thera eruption was one of the largest natural disasters witnessed in human history. Its impact, consequences, and timing have dominated the discourse of ancient Mediterranean studies for nearly a century. Despite the eruption's high intensity (Volcanic Explosivity Index 7; Dense Rock Equivalent of 78 to 86 km) [T. H. Druitt, F. W. McCoy, G. E. Vougioukalakis, Elements 15, 185-190 (2019)] and tsunami-generating capabilities [K. Minoura etal., Geology 28, 59-62 (2000)], few tsunami deposits are reported. In contrast, descriptions of pumice, ash, and tephra deposits are widely published. This mismatch may be an artifact of interpretive capabilities, given how rapidly tsunami sedimentology has advanced in recent years. A well-preserved volcanic ash layer and chaotic destruction horizon were identified in stratified deposits at Çeşme-Bağlararası, a western Anatolian/Aegean coastal archaeological site. To interpret these deposits, archaeological and sedimentological analysis (X-ray fluorescence spectroscopy instrumental neutron activation analysis, granulometry, micropaleontology, and radiocarbon dating) were performed. According to the results, the archaeological site was hit by a series of strong tsunamis that caused damage and erosion, leaving behind a thick layer of debris, distinguishable by its physical, biological, and chemical signature. An articulated human and dog skeleton discovered within the tsunami debris are in situ victims related to the Late Bronze Age Thera eruption event. Calibrated radiocarbon ages from well-constrained, short-lived organics from within the tsunami deposit constrain the event to no earlier than 1612 BCE. The deposit provides a time capsule that demonstrates the nature, enormity, and expansive geographic extent of this catastrophic event.

Volumetric extrusive rates of silicic supereruptions from the Afro-Arabian large igneous province

The main phase of silicic volcanism from the Afro-Arabian large igneous province preserves some of the largest volcanic eruptions on Earth, with six units totaling >8,600 km3 dense rock equivalent (DRE). The large volumes of rapidly emplaced individual eruptions present a case study for examining the tempo of voluminous silicic magma generation and emplacement. Here were report high-precision 206Pb/238U zircon ages and show that the largest sequentially dated eruptions occurred within 48 ± 34 kyr (29.755 ± 0.023 Ma to 29.707 ± 0.025 Ma), yielding the highest known long-term volumetric extrusive rate of silicic volcanism on Earth. While these are the largest known sequential silicic supereruptions, they did not cause major global environmental change. We also provide a robust tie-point for calibration of the geomagnetic polarity timescale by integrating 40Ar/39Ar data with our 206Pb/238U ages to yield new constraints on the duration of the C11n.1r Subchron.

Evaluating the Potential of Rhyolitic Glass as a Lithium Source for Brine Deposits

Abstract Lithium is an economically important element that is increasingly extracted from brines accumulated in continental basins. While a number of studies have identified silicic magmatic rocks as the ultimate source of dissolved brine lithium, the processes by which Li is mobilized remain poorly constrained. Here we focus on the potential of low-temperature, post-eruptive processes to remove Li from volcanic glass and generate Li-rich fluids. The rhyolitic glasses in this study (from the Yellowstone-Snake River Plain volcanic province in western North America) have interacted with meteoric water emplacement as revealed by textures and a variety of geochemical and isotopic signatures. Indices of glass hydration correlate with Li concentrations, suggesting Li is lost to the water during the water-rock interaction. We estimate the original Li content upon deposition and the magnitude of Li depletion both by direct in situ glass measurements and by applying a partition-coefficient approach to plagioclase Li contents. Across our whole sample set (19 eruptive units spanning ca. 10 m.y.), Li losses average 8.9 ppm, with a maximum loss of 37.5 ppm. This allows estimation of the dense rock equivalent of silicic volcanic lithologies required to potentially source a brine deposit. Our data indicate that surficial processes occurring post-eruption may provide sufficient Li to form economic deposits. We found no relationship between deposit age and Li loss, i.e., hydration does not appear to be an ongoing process. Rather, it occurs primarily while the deposit is cooling shortly after eruption, with δ18O and δD in our case study suggesting a temperature window of 40° to 70°C.

A black hole particle swarm optimization method for the source parameters inversion: application to the 2015 Calbuco eruption, Chile

The traditional genetic algorithm and simulated annealing methods have been widely used in geophysical modeling. However, these nonlinear inversion methods require a lot of calculations, many control parameters and are unstable. In this paper, a particle swarm optimization algorithm combined with black hole strategy (BH-PSO) is proposed to solve these problems. The comprehensive experiments show that the BH-PSO method consumes less time than the simulated annealing (SA) method and has a higher accuracy than the genetic algorithm (GA). It is more applicable to the inversion of parameters of volcanic magma chamber, and easier to be generalized to other kinematic source parameters inversion. Based on BH-PSO method, Sentinel-1 data, composite dislocation model (CDM), Yang model and Mogi model, the magma chamber parameters of Calbuco eruption in 2015 were retrieved. The results show that the RMSE of CDM model is 1.1 cm, which can better fit the surface deformation than the Mogi model and Yang model. The final results show that the magma chamber is located about 0.8 km northeast of the crater, about 9 km below the surface, and the total volume of the erupted volcanic material obtained with the CDM Model is of 0.209 km3, without considering dense rock equivalent.

Evolution of a magmatic to a phreatomagmatic volcanic system: The birth of a monogenetic volcanic field, Tilocálar volcanoes, northern Chile

The Tilocálar volcanic complex comprises four monogenetic volcanoes located at the southeastern edge of the Salar de Atacama Basin, northern Chile. These monogenetic volcanic centers are the Tilocálar Norte lava, the El Maní dome, the Tilocálar Sur small–lava shield, and the Tilocálar Sur maar, respectively, and were formed between 460 ± 50 ka to < 1 Ma ago along the north–south-striking Tilomonte ridge that underlies the Tucúcaro Ignimbrite (3.2 ± 0.3 Ma). Their formation is the result of an intermediate magma rising to the surface during a local transtensional regime, which is observed at El Maní, under a dominantly compressional tectonic setting. The Tilocálar monogenetic centers provide a rare opportunity to examine the variability from individual and small–volume magma batches to the development of a monogenetic volcanic field. These volcanoes and the control on their eruption styles were studied by geological mapping and stratigraphic considerations, morphometric analysis, textural studies (density and vesicularity), petrographic observations, and geochemical analyzes. The Tilocálar Norte lavas have an intermediate composition (mostly andesite, 62.02 wt.% SiO2) that reach a maximum distance of 3.9 km to the north and 1.2 km to the southwest from their vent, with a dense–rock equivalent (DRE) volume of 8.73×107 m3. The El Maní lava dome is small (covering 750 m2 area and consisting of 1.06×103 m3 DRE volume) that presents mingled mafic (63.89 wt.% SiO2) and felsic (73.73 wt.% SiO2) products of the original magma source, related to shallow crustal melts. The Tilocálar Sur small lava–shield is characterized by a pyroclastic fall deposit and lavas. The pyroclastic fall deposit is characterized by agglutinated andesite scoria–spatter fall units, covering 2.81 km2 and consisting of 7.75×105 m3 DRE volume. In contrast, the lavas are characterized by an andesitic composition (57.64 wt.% SiO2), which is 1.8 km in length to the northwest and 1.4 km to the east of their source. These lavas cover an area of 3.78 km2 with 9.15×107 m3 DRE volume. Tilocálar Sur maar crater has an elliptical shape in map view (363 m diameter east–west and 288 m diameter north–south), surrounded by individual conglomerates, sandstones, granitoids, and tuff fragments that lie on the present–day surface around the crater rim. The Tilocálar volcanic complex is interpreted as a small monogenetic volcanic field that shows an eruption history defined by a spectrum of eruptive processes determined by internal and external parameters at any given time from the four independent volcanic centers.

Lava effusion rate evolution and erupted volume during the 2018 Kīlauea lower East Rift Zone eruption

The 2018 eruption on the lower East Rift Zone of Kīlauea Volcano produced one of the largest and most destructive lava flows in Hawai’i during the past 200 years. Over the course of more than 3 months, twenty-four fissures erupted, and the rate of lava effusion varied by two orders of magnitude, with significant implications for evolving flow behavior and hazards. Syn-eruptive data were collected to quantify these changes in lava effusion rate, including video of flow through channels and digital elevation models acquired using small unoccupied aircraft systems, airborne lidar, and airborne single-pass interferometric synthetic aperture radar. Topographic data through time allowed calculation of subaerial lava flow volume and time-averaged discharge rate over the course of the eruption, which we integrated with pre- and post-eruption bathymetric surveys. Repeat videos of the near-vent channel were analyzed with particle velocimetry to extract flow velocities, and these were combined with open channel flow theory to calculate a time series of instantaneous effusion rates. Results show a general increase in dense rock equivalent (DRE) effusion rate from ~7 to ~100 m3/s from early to late May for the whole flow field and ≥ 200 m3/s by mid-June after the eruption had focused at a primary vent. By the end of the eruption in August, 0.9–1.4 km3 DRE of lava had erupted, with 0.4 km3 deposited on land and at least 0.5 km3 offshore. The trends in effusion rate through time reflect magmatic processes in the connected summit and rift zone system that controlled eruption rate, with resulting implications for lava flow dynamics and hazards.

New ages, morphometric and geochemical data on recent shoshonitic volcanism of the Puna, Central Volcanic Zone of Andes: San Jerónimo and Negro de Chorrillos volcanoes

Shoshonitic volcanic centres are scarce within the back-arc mafic volcanism of the Puna Plateau in the Central Volcanic Zone of the Andes. San Jerónimo and Negro de Chorrillos volcanoes are two well preserved shoshonitic monogenetic edifices that developed mainly Strombolian activity and lava flows, which extended more than 9 and 4 km from the vent, producing a volume DRE (Dense Rock Equivalent) of 0.091 and 0.020 km3, respectively. The new unspiked K–Ar (groundmass) ages of San Jerónimo (144 ± 3 ka) and Negro de Chorrillos (51 ± 2 ka) eruptions presented in this work are both younger than those previously published. Petrographic and compositional features allow distinguishing between potassic and ultrapotassic suites in volcanic products of both eruptions. Phlogopite occurrence and low glass content characterize the ultrapotassic suite. Based on the crustal thickness of this part of the Puna and the experimental constraint, these magmas last equilibrated at Moho depths at around 50 km (the highest depth of spinel lherzolite stability field) for temperatures of 1100–1200 °C. Once in the crust, the K-rich magma underwent a minor interaction with a trachytic-trachydacitic melt, which is evidenced petrographically and geochemically, e.g., mismatch of mineral assemblages (co-occurrence of olivine and quartz), disequilibrium crystal textures (dusty zones in plagioclase, embayments in sanidine), and a wide range of compositional variation in the glasses. Ultrapotassic (i.e., phlogopite-bearing) and potassic lavas in the same eruption are interpreted as pulses of the same magma but with a longer mixing time with the trachytic-trachydacitic melt for the resulting ultrapotassic rocks within an eruptive time frame of hours or days. The singular shoshonitic character of these magmas could be related to their origin along an old terrane boundary. Afterwards, as occurs for other mafic magmas of the Puna, major NW-SE fault systems would favour their ascent to the surface.

Pululahua dome complex, Ecuador: eruptive history, total magma output and potential hazards

Pululahua is a potentially active dome complex located 15 km north of Quito. It is composed of sixteen dacitic-andesitic lava domes located inside and around a semi-rectangular depression. We divide its eruptive history into: (1) a first member characterized by effusive lava dome growth and collapse (Units I and II, >18–12 ka), (2) a second member consisting of at least four explosive eruptive phases (VEI ~4), responsible for the formation of a caldera-like depression (Unit III, 2.6–2.3 ka cal BP), and (3) a final member encompassing partially explosive dome growth inside the depression (Unit IV, 2.2 ka cal BP). Rock samples show no significant geochemical changes over time, except for a slight decrease in SiO2 and a minor increase in MgO and Fe2O3 towards younger magmas. In addition, based on field measurements, a total minimum bulk volume of all domes and pyroclastic deposits is estimated at ~5.75 ± 0.14 km³, yielding a dense rock equivalent of ~4.24 ± 0.1 km³ and a total erupted magma mass of 10.58 ± 0.16 E+12 kg. Finally, we put forward three future hazard scenarios that could affect the population in the proximal area (>70 k people): (1) an unrest period involving increased seismic events, volcanic gas emissions and potentially small phreatic explosions, (2) the effusive and/or slightly explosive growth and destruction of lava domes accompanied by block-and-ash flows and tephra fall, and (3) large explosive events (VEI ~4) that generate regional tephra fall and massive pyroclastic density currents.

The Magnitude of the 39.8 ka Campanian Ignimbrite Eruption, Italy: Method, Uncertainties and Errors

The 39.8 ka Campanian Ignimbrite eruption is the largest caldera-forming eruption of the Campi Flegrei and had a global-scale impact on the environment and human populations. The cooling following the eruption and its widespread tephra strongly affected the paleoenvironment and the migration of hominids in Europe. Despite a large number of studies, the Campanian Ignimbrite Dense Rock Equivalent (DRE) volume estimates range from 60 to 300 km3. Here we present a review of the previous volume evaluations and a new calculation of the volume of the ignimbrite. This estimate is constrained by the first total isopach map of the Campanian Ignimbrite PDC deposit preserved on land, developed through a method that reconstructs the paleo-topography at the time of the eruption. The method is reproducible for all strongly topographically controlled ignimbrites and allows the calculation of well-defined uncertainties in the on-land ignimbrite deposits. The preserved total extra-caldera bulk volume of the ignimbrite is estimated at 68.2 km3 ± 6.6 km3. The total PDC deposit volume is then corrected for erosion, ash elutriation, the intracaldera deposit volume and the volume of tephra deposited in the sea, and volumes of fallout are taken from other studies. The final total volume estimate of the eruption ranges from 177 km3 – 265 km3 DRE. This value corresponds to a mass of 4.6 - 6.9 x 1014 kg, a magnitude (M) of 7.7 – 7.8 and a volcanic explosivity index (VEI) of 7. The new detailed estimate of the Campanian Ignimbrite eruption physical parameters, for the first time constrained by the ignimbrite deposit, confirms the magnitude of this event.

Comparing Simulations of Umbrella-Cloud Growth and Ash Transport with Observations from Pinatubo, Kelud, and Calbuco Volcanoes

The largest explosive volcanic eruptions produce umbrella clouds that drive ash radially outward, enlarging the area that impacts aviation and ground-based communities. Models must consider the effects of umbrella spreading when forecasting hazards from these eruptions. In this paper we test a version of the advection–dispersion model Ash3d that considers umbrella spreading by comparing its simulations with observations from three well-documented umbrella-forming eruptions: (1) the 15 June 1991 eruption of Pinatubo (Philippines); (2) the 13 February 2014 eruption of Kelud (Indonesia); and (3) phase 2 of the 22–23 April 2015 eruption of Calbuco (Chile). In volume, these eruptions ranged from several cubic kilometers dense-rock equivalent (DRE) for Pinatubo to about one tenth for Calbuco. In mass eruption rate (MER), they ranged from 108–109 kg s−1 at Pinatubo to 9–16 × 106 kg s−1 at Calbuco. For each case we ran simulations that considered umbrella growth and ones that did not. All umbrella-cloud simulations produced a cloud whose area was within ~25% of the observed cloud by the end of the eruption. By the eruption end, the simulated areas of the Pinatubo, Kelud, and Calbuco clouds were 851, 53.2, and 100 × 103 km2 respectively. These areas were 2.2, 2.2, and 1.5 times the areas calculated in simulations that ignored umbrella growth. For Pinatubo and Kelud, the umbrella simulations provided better agreement with the observed cloud area than the non-umbrella simulations. Each of these simulations extended 24 h from the eruption start. After the eruption ended, the difference in cloud area (umbrella minus non-umbrella) at Pinatubo persisted for many hours; at Kelud it diminished and became negative after 14 h and at Calbuco it became negative after ~23 h. The negative differences were inferred to result from the fact that non-umbrella simulations distributed ash over a wider vertical extent in the plume, and that wind shear spread the cloud out in multiple directions. Thus, for some smaller eruptions, wind shear can produce a larger cloud than might be produced by umbrella spreading alone.

Quantifying gas emissions associated with the 2018 rift eruption of Kīlauea Volcano using ground-based DOAS measurements

Starting on 3 May 2018, a series of eruptive fissures opened in Kīlauea Volcano’s lower East Rift Zone (LERZ). Over the course of the next 3 months, intense degassing accompanied lava effusion from these fissures. Here, we report on ground-based observations of the gas emissions associated with Kīlauea’s 2018 eruption. Visual observations combined with radiative transfer modeling show that ultraviolet light could not efficiently penetrate the gas and aerosol plume in the LERZ, complicating SO2 measurements by differential optical absorption spectroscopy (DOAS). By applying a statistical method that integrates a radiative transfer model with the DOAS retrievals, we were able to calculate sulfur dioxide (SO2) emission rates along with estimates of their uncertainty. We find that sustained SO2 emissions were highest in June and early July, when approximately 200 kt SO2 were emitted daily. At the 68% confidence interval, we estimate that 7.1–13.6 Mt SO2 were released from the LERZ during the entire May to September eruptive episode. Scaling our results with in situ measurements of plume composition, we calculate that 11–21 Mt H2O and 1.5–2.8 Mt CO2 were also emitted. The gas and aerosol emissions caused hazardous conditions in areas proximal to the active vents, but plume dispersion modeling shows that the eruption also significantly impacted air quality hundreds of kilometers downwind. Combined with petrologic studies of the erupted lavas, our measurements indicate that 1.1–2.3 km3 dense-rock equivalent of lava were erupted from the LERZ, which is approximately twice the concomitant collapse volume of the volcano’s summit.