Volcanica

A record of magmatic differentiation in plutonic xenoliths from Santorini (Greece)

Sean Whitley — 2024-07-16

Plutonic xenoliths from volcanic arcs provide unique insights into transcrustal magmatic systems in subduction zone settings. At Santorini volcano in the Central Aegean Volcanic Arc (Greece), plutonic xenoliths occur throughout a sequence of lavas and pyroclastic rocks erupted within the last ~360 ka. They are mineralogically variable, ranging from troctolites to olivine gabbros, gabbros, gabbronorites, and diorites. Thermobarometric calculations based on mineral and melt inclusion compositions indicate equilibration over a range of temperatures (1100 to 750 °C) at shallow to mid-crustal depths (P <400 MPa), but there is no evidence for crystallisation at lower crustal depths. Oxygen isotope data of mineral separates and calculated δ¹⁸O melt values are in line with extensive closed-system fractional crystallisation at magmatic temperatures, without a requirement for extensive assimilation of the subvolcanic continental basement. The xenolith minerals compositionally overlap with phenocrysts from the volcanic rocks, but they also contain evidence for the presence of highly evolved melt compositions in the form of melt inclusions with extremely silica-rich compositions (up to 82 wt.% SiO₂) and high enrichments of incompatible trace elements coupled with increasing negative Eu anomalies in clinopyroxenes. Since these characteristics correlate systematically with differentiation indices and rock type, they are interpreted to reflect melt evolution via fractional crystallisation as the dominant differentiation process with no significant role of reactive porous flow. These observations highlight that trapped melt fractions can influence mineral compositional variations in the plutonic xenoliths, and in turn the mineral compositions demonstrate a melt compositional variability not preserved in the volcanic rock record.

The abundance of submarine volcanism in arcs

Dallas Abbott — 2024-07-22

Explosive submarine arc volcanoes can cause tsunamis, affect climate, and pose hazards to airplanes and ships. Although 70 % of the Earth is submarine, only 15 % of Holocene arc volcanoes in the Smithsonian Global Volcanism database are submarine. Merging locations of active submarine hydrothermal vents in arcs and the above database, we found 71 unlisted submarine arc volcanoes. Using Baker [2017, doi: 10.1016/j.oregeorev.2017.02.006], only 44 % of hydrothermal vents in arcs are known. Only 77 of the vent fields are on volcanoes in the Smithsonian database. Assuming that unknown submarine arc volcanoes are present in the same proportions as unknown vents, there are ~160 as-yet undiscovered Holocene age submarine arc volcanoes. Using geophysical data, we located 291 unsurveyed seamounts <30 km from arc axes, the distance within which active vents occur. We estimate 119±16 have active vents. Because more unknown seamounts exist, this means that >32 % of Holocene arc volcanoes are submarine.

Numerical modeling predicts seismic resonances in the magma chamber-conduit system due to wavefield capturing

Fabian Limberger — 2024-07-19

This study utilizes 3D numerical models to simulate seismic resonances in a volcanic edifice, arising from the interaction between an externally excited wavefield and a magma chamber-conduit system. The magma chamber and conduit efficiently capture the incident wavefield of both P- and S-waves, excited by a high-frequency (~10 Hz) earthquake located within the edifice. Due to multiple internal reflections off the boundaries of the chamber and conduit, prolonged reverberations occur, which are guided along the conduit. Temporal and spectral analyses of synthetic seismograms illustrate that models with larger chambers and wider conduits consistently yield larger resonance amplitudes at distinct frequencies. Our models indicate that a larger magma chamber can produce an intensified scattered wavefield with a broad frequency range, observable up to several hundred meters away from the central conduit. Generally, these externally initiated ‘calabash resonances’ may appear as tremor-like signals at seismometers on the edifice, accompanying more conventional seismic events in its proximity.

"Hot and sticky" and "cold and damp" pyroclastic eruptions, and their relationship with topography: valley- and lake-filling ignimbrites, Ardnamurchan, NW Scotland

David Brown — 2024-07-25

Pyroclastic density currents are complex mixtures of rock, ash and gas and represent significant hazards at many active volcanoes worldwide. Ignimbrites are the deposits of pyroclastic density currents and can be used to record the eruption dynamics and the interaction of the current with the landscape over time and space. The Sròn Mhòr Member in Ardnamurchan, NW Scotland, is a newly documented sequence of silicic Paleocene ignimbrites. Five phases of eruption are recorded by the ignimbrites, which range from non-welded to welded to lava-like. Between each eruption phase, a period of non-deposition occurred, during which rapid erosion and incision took place. The ignimbrites record how pyroclastic density currents of different temperature, grain size, rheology, and composition interacted with the landscape, filling ancient valleys and lakes, before switching to or re-establishing new drainage pathways. Our results provide further insight into ignimbrite deposition that can be applied to volcanoes worldwide.

Estimation and uncertainty quantification of magma interaction times using statistical emulation

Luca Insolia — 2024-08-27

The evolution of volcanic plumbing systems, which controls the style and size of eruptions, is largely determined by processes at depths that are not observable. Scientists use numerical models to simulate these processes and compare the outputs with data on erupted products to understand the plumbing system and eruption processes. However, our ability to explore the parameter space in order to match petrological and geophysical observations is limited by the computational cost required for such simulations. As an alternative, we present a statistical emulator that can reproduce the numerical results as a function of a set of input parameters. This approach can be used to invert the observed distribution of whole rock chemistry to determine the duration of interaction between magmas preceding an eruption and identify the best matching input parameters. This method intrinsically includes error propagation, thus providing reliable confidence intervals for the relevant parameters of the numerical simulations.

Multiple sources of elevation change during and after the 2011–2012 Cordón Caulle, Chile eruption measured by satellite topographic time series

Diego Lobos Lillo — 2024-08-28

The 2011–2012 eruption at Cordón Caulle, Chile offers an exceptional opportunity to investigate topographic evolution of a laccolith, lava flows, and tephra during and after rhyolitic eruptions using satellite TanDEM-X and Plèiades data. We find distinct phases: rapid surface uplift from the laccolith and tephra (June–August 2011) and lava (June 2011–March 2012), followed by a reduction in the elevation of the laccolith and tephra (up to 19 m yr⁻¹) until February 2013, and slower subsidence of all deposits until 2019 (the most recent data). The spatial distribution of subsidence-to-uplift ratios shows different volcanic and geomorphological processes occurring (degassing, cooling, crystallization, lateral movement, compaction, erosion). Pre-eruptive river channels showed elevation increases of up to 10–50 m due to tephra deposition, but this tephra was largely removed within three to four years. This research shows the potential of repeating high-resolution remote sensing elevation data to elucidate volcanic landscape evolution and yields insights into the co- and post-eruptive evolution of deposits.

New insights into the Upper Pleistocene directed blast eruption, Popocatépetl volcano, México

R. Marcela Lira-Beltrán — 2024-08-28

Volcanic eruptions of the directed blast type are characterized by powerful explosions with a significant lateral pyroclastic density current (PDC) component that can travel at speeds above 100 m s^–1 and affect hundreds of square kilometers around a volcano. This study presents preliminary results of a detailed fieldwork and stratigraphic study of deposits associated with the Ocoxaltepec Blast deposit, which originated from the Popocatépetl volcano during a strong eruption associated with the southwestward sector collapse of the volcanic edifice around 23,500 ka BP. Within the study area, which contains 58,870 inhabitants, we found 42 new sites where the blast deposit outcrops, in locations up to 25 km from the volcano crater, with thicknesses up to over 20 m. We divide these blast deposits into two categories: confined channel-fill PDC deposits and unconfined interfluve and upland PDC deposits. With the new data we have estimated the dispersion area of the directed blast to be approximately 338 km². Twenty-nine of the new outcrops are located outside the hazard polygon associated with concentrated PDCs related to the lowest probability Plinian eruption currently considered from Popocatépetl.

Temporal and morphological eruption characteristics of lava flows from the Holocene La Taza monogenetic cone obtained from petrology and LiDAR imagery (Michoacán, Mexico)

Geoffrey A Lerner — 2024-09-04

The Holocene La Taza andesitic volcano is one of over 1000 volcanic centers located within the Michoacán-Guanajuato Volcanic Field (MGVF) in central-western Mexico. La Taza (~8500–8200 yr BP) represents one possible eruption style within the field, with deposits indicating Strombolian activity followed by a series of lava flows. In our study, we reconstruct the eruption of La Taza through a combination of LiDAR mapping and petrological and geochemical analyses. LiDAR mapping combined with ground- truthing in the field allowed us to differentiate and determine the sequence of the volcano’s lava flows, revealing seven lava flows with a volume of ~0.6 km3. This morphological information was paired with geothermobarometers to estimate lava flow viscosities, mean effusion rates, and emplacement times, showing a likely duration of 1.1–4.3 years. Recreating this eruption contributes to the understanding of potential durations and lava flow rheology of future MGVF eruptions, crucial characteristics for hazard planning and mitigation.

Lava lake activity at Nyiragongo volcano between the years 2020 and 2021 documented by seismic activity and sulfur dioxide emissions, DRC

Olivier Munguiko — 2024-09-04

The activity of Nyiragongo volcano was assessed based on seismic data and SO₂ measurements during the years 2020 and 2021. We analysed several events that marked the activity of the Nyiragongo lava lake. It was found that when SO₂ concentrations reached more than 9 kT/day, Nyiragongo is in intense activity. The high SO₂ emission in the Nyiragongo gas plume generates LP and VLP earthquakes, the RSAM curve can decrease when intrusions occur. The RSAM may still increase after degassing of SO₂ to reflect the influx of new magma. SO₂ outgassing always precedes seismic activity (LP and VLP), except when the crater was empty, seismic activity (with LP and VLP) had started, but the RSAM increased with outgassing. This leads us to notice a close link between the seismo-volcanic activity and the SO₂ emissions. Both tools are therefore essential for the monitoring of Nyiragongo volcano.

Rapid caldera subsidence and fluctuating eruption dynamics: the lithostratigraphy and structure of the Loch Bà Caldera, Isle of Mull, NW Scotland

Peter Nicholls — 2024-09-04

Caldera-forming eruptions represent extremely hazardous events. The Loch Bà Caldera on the Isle of Mull, NW Scotland, preserves an ~120 m thick sequence of Palaeogene silicic pyroclastic rocks and collapse breccias. Here we present the first detailed account of the lithostratigraphy and architecture of the caldera-fill. A silicic explosive eruption generated pyroclastic density currents that deposited a range of rhyolitic ignimbrite lithofacies as the caldera collapsed. Abrupt changes in ignimbrite lithofacies and lateral thickness changes are attributed to volcano-tectonic faults and incremental collapse of the caldera. Five eruption phases have been recognised that record rapid switching between sustained high-fountaining and low-fountaining “boil-over” eruptions. The ignimbrites are unconformably overlain by mesobreccias and inward rotated megablocks of basalt lava country rock, which record catastrophic inward collapse of the caldera walls and margins. Our results provide new insights into caldera collapse and intra-caldera-fill that can be applied to other volcanoes worldwide.

Q̓welq̓welústen/Mount Meager Volcanic Complex, British Columbia: Inter-eruptive landslide susceptibility assessment using statistical machine learning techniques

Jason Connelly — 2024-09-04

Over the last 60 years, six landslides with volumes from 10⁵ m³ to 5.3 × 10⁷ m³ have occurred around Q̓welq̓welústen (Mount Meager Volcanic Complex; MMVC), southwestern British Columbia, Canada. The dormant volcanic massif has experienced significant uplift leading to exposed and incised Miocene and older basement rocks and volcanic rocks associated with the MMVC. The topographic relief and variation in rock types creates a complex environment where the interplay between lithology and landslide initiation can be captured. We developed models using logistic regression and random forest methods to assess the most critical parameters affecting inter-eruptive landslide susceptibility in the area. Both approaches indicate that Devastator Peak and Plinth Peak volcanic assemblages are of notably higher landslide susceptibility. Large landslides originated in higher areas, but long runout poses the main hazard. Results support the need for detailed geological mapping for landslide susceptibility assessments in elevated volcanic massifs worldwide.

The geometric spectrum of lava domes and spines

Amy J. Myers — 2024-09-11

Extrusion of viscous lava produces domes and spines, collapses of which pose a significant local hazard. Understanding extrusion processes and probabilistic hazard estimation require comprehensive datasets of geometric parameters. We introduce Morphology of Viscous Extrusions (MoVE), a collation of 323 observations of height and width from 80 extrusions at 46 volcanoes globally with compositions spanning basaltic through rhyolitic. Filtering this dataset for sample size, age, and time series overrepresentation reduces the composition range to basaltic-andesitic through dacitic, for which we do not identify a statistically significant effect of composition on extrusion geometry. Young (<200 yr) basaltic or rhyolitic domes are either rare or underrepresented globally. Five well-resolved time series highlight various height-width evolutions and scales possible during growth. Extrusion heights and widths are well-estimated by a Weibull distribution and scale according to a truncated power law; this can guide parameter values used in probabilistic hazard models of collapse-associated pyroclastic density currents.

Uranium-series disequilibria in MORB, revisited: A systematic numerical approach to partial melting of a heterogeneous mantle

Lynne Elkins — 2024-10-03

We present computational modeling outcomes for bilithologic (peridotite and pyroxenite) mantle melting in divergent environments, considering equilibrium and disequilibrium porous flow melting of 0–50 % pyroxenite in thermal equilibrium with peridotite, potential temperatures of 1300 and 1400 °C, upwelling rates from 1–50 cm yr⁻¹, maximum porosities of 0.1–2.0 %, and four compositions that span pyroxenite melting behavior. Basalt-like pyroxenites (G2) uniquely produce low (²²⁶Ra/²³⁰Th) and (²³¹Pa/²³⁵U) with high (²³⁰Th/²³⁸U), but quantities greater than ~10 % produce anomalously thick crust, restricting their global abundance. Silica-deficient pyroxenite (M7-16 and MIX1G) melts are more moderate, but require chemical re-equilibration during transport to resemble global basalts, while hybrid lithologies (KG1) produce melts similar to those of peridotites. Uranium-series disequilibria in partial melts can also be decoupled from trace elements by radioactive decay in two-dimensional regimes. The mantle must thus contain multiple types of pyroxenite on a global scale, with melts traveling by complex networks and experiencing heterogeneous extents of chemical re-equilibration.

Alkali activated materials from Tajogaite volcanic ash (La Palma, Spain): a green recovery after the 2021 eruption

Roberta Occhipinti — 2024-10-06

The 2021 Tajogaite eruption was marked by intense pyroclastic fallout that covered a substantial portion of La Palma island, with maximum thicknesses in the central-western part. This, combined with lava flows, resulted in widespread damage to public and private properties. In this study, we investigated if volcanic ash from this eruption could serve as a raw material in the synthesis of alkali activated materials (AAMs) and contribute to the construction of eco-friendly buildings and the restoration of those damaged by the eruption. Volcanic ash-based AAMs were synthesized using NaOH and Na₂SiO₃ as alkaline solutions and by adding metakaolin to enhance ash reactivity and enable processing at ambient temperatures. Lightweight porous AAMs were also produced using H₂O₂ and metallic aluminum as foaming agents. Chemical, textural, physical, and mechanical analyses on the final products assessed their suitability as environmentally friendly materials to be used in the reconstruction of the island infrastructure, opening new perspectives on recovery actions that can be undertaken after disastrous eruptions. Of all the islands in the Canary Archipelago, La Palma has experienced the highest number of eruptions (8) in historical times, all of which showing considerable similarity in terms of eruptive mechanisms and composition to the most recent Tajogaite event. Although this study investigated fresh Tajogaite ash, similar perspectives can be envisaged for both other recent eruptions at La Palma and other similar volcanic scenarios worldwide.

A shake and a surge: Assessing the possibility of an earthquake-triggered eruption at Steamboat Geyser

Mara Reed — 2024-10-17

When and why earthquakes trigger volcano and geyser eruptions remains unclear. In September 2022, Steamboat Geyser in Yellowstone, USA erupted 8.25 hours after a local M3.9 earthquake—an improbable coincidence based on the geyser’s eruption intervals. We leverage monitoring data from the surrounding geyser basin to determine if the earthquake triggered this eruption. We calculate a peak ground velocity of 1.2 cm s⁻¹, which is the largest ground motion in the area since Steamboat reactivated in March 2018 and exceeds a threshold associated with past earthquake-triggered geyser eruptions in Yellowstone. Despite no changes in other surface hydrothermal activity, we found abrupt, short-lived shifts in ambient seismic noise amplitude and relative seismic velocity in narrow frequency bands related to the subsurface hydrothermal system. Our analysis indicates that Steamboat’s eruption was likely earthquake-triggered. The hours-long delay suggests that dynamic strains from seismic waves altered subsurface permeability and flow which enabled eruption.

How a non harmonic-like tremor at a volcanic lake could be caused by sustained wind: A case of study of Taupō volcano

Henriette Bakkar Hindeleh — 2024-10-21

Taupō volcano lies underneath the largest lake in New Zealand. It undergoes unrest roughly every ten years, has minor eruptions every few hundred years, and has supereruptions. Understanding volcanic seismic signals provides insights into the volcano dynamics and helps to anticipate eruptions. Harmonic and non-harmonic volcanic tremor are common signals that indicate fluid mobilisation in volcanic systems. We observed a signal that resembled non-harmonic tremor during 2019 at Taupō volcano. Careful time-frequency analysis of seismic data and weather data from around the lake revealed that the signals were not magmatic in origin, but were most likely from lake microseisms caused by special conditions of the wind, which generates wind-driven waves in the lake. The frequency range of lake microseisms at Taupō starts and ends with a dominant frequency of 0.7–1.0 Hz, and during the maximum energy peak, the dominant frequency is of 0.50–0.56 Hz. Such signals may be common in caldera lakes, which need to be distinguished from tremor caused by volcanic activity, so as not to exaggerate the probability of eruptions.

Pumice cone eruptions at Aluto volcano, Ethiopia

Ben Clarke — 2024-11-12

Pumice cones are volcanic landforms that exist worldwide, but whose eruption has never been observed. Interpretations of these eruptions vary significantly in style, intensity, and magnitude, pertinent for volcanic hazard assessment. Aluto volcano (Ethiopia) provides an unprecedented insight into the hazardous nature of these enigmatic eruptions. We investigate nine such pumice cones, and find that they are the product of moderate-intensity explosive eruptions that develop a sustained but unsteady eruption column, deposit lapilli- to block-sized tephra close to the vent forming pumice cones, can deposit distal tephra from an umbrella cloud, produce pyroclastic density currents by repeated partial column-collapse, and end with the emplacement of silicic lava. Like basaltic pyroclastic cones, pumice cones can also undergo collapse by lava flow emplacement. Alongside recent evaluation of distal tephras, we suggest that these eruptions, at least at Aluto, vary in intensity and magnitude from violent-Strombolian to sub-Plinian, and each follow a remarkably similar sequence of eruptive processes.

PyIRoGlass: An open-source, Bayesian MCMC algorithm for fitting baselines to FTIR spectra of basaltic-andesitic glasses

Sarah Shi — 2024-07-26

Quantifying volatile concentrations in magmas is critical for understanding magma storage, phase equilibria, and eruption processes. We present PyIRoGlass, an open-source Python package for quantifying concentrations of H₂O and CO₂ species in the transmission FTIR spectra of basaltic to andesitic glasses. We leverage a dataset of natural melt inclusions and back-arc basin basalts with volatiles below detection to delineate the fundamental shape and variability of the baseline underlying the CO₃^2- and H₂O_{m, 1635} peaks, in the mid-infrared region. All Beer-Lambert Law parameters are examined to quantify associated uncertainties. PyIRoGlass employs Bayesian inference and Markov Chain Monte Carlo sampling to fit all probable baselines and peaks, solving for best-fit parameters and capturing covariance to offer robust uncertainty estimates. Results from PyIRoGlass agree with independent analyses of experimental devolatilized glasses (within 6 %) and interlaboratory standards (10 % for H₂O, 6 % for CO₂). We determine new molar absorptivities for basalts, εH₂O_t,3550 = 63.03 ± 4.47 L/mol · cm and εCO²⁻_3,1515,1430 = 303.44 ± 9.20 L/mol · cm; we additionally update the composition-dependent parameterizations of molar absorptivities, with their uncertainties, for all H₂O and CO₂ species peaks. The open-source nature of PyIRoGlass ensures its adaptability and evolution as more data become available.