Journal of Volcanology and Geothermal Research最新文献_第2页

The spatiotemporal development of downsag and trapdoor structures during caldera subsidence with 1–10 km in diameter in analogue sandbox experiments

IF 2.4 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of Volcanology and Geothermal Research

Pub Date : 2025-02-10 DOI: 10.1016/j.jvolgeores.2025.108294

Ryuhei Sanjo , Toshihiko Sugai

Calderas are volcanic depressions formed when the roof of a magma chamber collapses due to the depletion of magma within the chamber. Investigating the development of caldera boundary faults that accommodate chamber-roof subsidence is crucial for understanding caldera collapse events and predicting contemporaneous and subsequent volcanic eruptions. Because subsurface structures in natural calderas are difficult to observe, analogue sandbox and numerical experiments, and inversions of geodetic data are often used to reconstruct caldera structures. Recent experimental and analytical studies have revealed localized downsag during the upward propagation of caldera boundary faults and that the fault structures of trapdoor calderas are highly variable. However, how downsag becomes localized during upward boundary fault propagation, and when and why trapdoor structures originate during caldera collapse remain open questions. Here, we performed analogue sandbox experiments in a transparent sandbox and used image analysis techniques to provide insights into these questions. Calderas with 1–10 km in diameter are more favorable than larger ones (tens of kilometers in diameter) for assessing downsagging and trapdoor subsidence, because these volcanic deformations may be masked by crustal deformation due to regional tectonics controlling large caldera subsidence. We therefore focused on calderas with 1–10 km in diameter, and excluded some factors such as pre-existing stress regimes, faults and magma flow, in order to evaluate the development of downsag and trapdoor subsidence themselves. Despite these experimental limitations, our experiments are in agreement with natural calderas and show that as caldera subsidence increases, downsag and trapdoor faulting evolve in four stages. (1) At the beginning of downsag, the horizontal displacement velocity is greatest along the edge of the downsagging region. (2) As the outward-dipping reverse faults nucleate at depth and propagate upward, the peak of horizontal displacement velocity localizes along the surface projection of the concealed faults. (3) Caldera collapse blocks then undergo trapdoor subsidence when the outward-dipping reverse faults reach the surface. (4) Finally, a second episode of trapdoor subsidence of the collapse block occurs when inward-dipping normal faults nucleate beyond the outward-dipping reverse faults. The first and second stages suggest that the existence and location of concealed caldera boundary faults can be predicted from the downsag deformation pattern. The third and fourth stages explain temporal and structural variations observed in trapdoor calderas in the context of caldera boundary fault development. Our model will improve the resolution of caldera structural reconstructions and associated inferences regarding magma chamber dynamics.

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引用次数: 0

Microearthquakes identification based on convolutional neural networks and clustering techniques

IF 2.4 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of Volcanology and Geothermal Research

Pub Date : 2025-02-07 DOI: 10.1016/j.jvolgeores.2025.108282

Fernando Lara , Román Lara-Cueva , Felipe Grijalva , Ana Zambrano

Microearthquakes are critical for understanding volcanic activity, leading to monitoring many volcanoes worldwide with seismic sensor networks. These networks generate a substantial amount of data, making visual analysis challenging. Consequently, researchers have focused on developing automatic microearthquake recognition systems over the past decades. A primary challenge with these systems is their reliance on labeled databases for training supervised learning models, where the output labels depend on the database labels. We propose using clustering algorithms in conjunction with a Fine-tuned Convolutional Neural Network (CNN) as a feature extractor to identify overlapping microearthquakes, and other types of microearthquakes withoutneeding labeled datasets. This methodology has two stages: The First stage relies on Transfer Learning, to specialize the CNN in microearthquake recognition. The Second stage uses the Fine-tuned CNN as a feature extractor. This methodology is applied to the Cotopaxi Volcano and validated in the Llaima Volcano. It uses unsupervised databases to find clusters of isolated events with similar characteristics to Long Period (LP), Volcano Tectonic (VT), Tremor (TRE), among others. Additionally, it identifies a cluster with overlapping microearthquakes. In the validation stage, 79 % of the VT events are associated to the same cluster without the need to adjust the Fine-tuned CNN. This test is performed on a dataset of a volcano never seen by CNN or Clustering algorithms. Normalized Entropy is used as a metric to verify the generalization of knowledge, the proposed work is compared with Uniform Manifold Approximation and Projection for Dimension Reduction (UMAP). The proposed work obtains 0.04 lower uncertainty with respect to UMAP.

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引用次数: 0

Development of permeable networks by viscous-brittle deformation in a shallow rhyolite intrusion. Part 2: Microstructural analysis

IF 2.4 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of Volcanology and Geothermal Research

Pub Date : 2025-02-06 DOI: 10.1016/j.jvolgeores.2025.108278

Taylor Witcher , Steffi Burchardt , Tobias Mattsson , Michael J. Heap , Anne Pluymakers , Kai Li , Peter Lazor

Volcanic and magmatic outgassing mechanisms can determine eruptive behavior of shallow silicic magma bodies. Most outgassing mechanisms proposed take place along conduit margins, where the highest strain rates drive ascending magma to brittle failure. However, these mechanisms do not account for outgassing large volumes of magma away from the conduit walls. Here, we present a continuum of porosity preserved in the microcrystalline rhyolitic Sandfell laccolith, Eastern Iceland. Three stages in the continuum are described: porous flow bands, pore channels, and fracture bands. These deformation features are present throughout the entire exposed volume of the Sandfell laccolith in meter-long band geometries, ranging from mm- to dm-scale thickness, and interlayered with coherent, undeformed rhyolite. Using microstructural analytical methods and drawing on the result of previous experimental studies, we show that emplacement-related deformation induced strain partitioning around a crystal content of 45 % that resulted in the segregation of melt-rich and melt-poorer flow bands. Subsequent deformation induced by continued magma emplacement caused strain partitioning in the melt-rich flow bands. Depending on strain rate, different types of deformation features developed, through dilation or porosity redistribution (porous flow bands), cavitation (pore channels), or tensile fracture (fracture bands). Porous flow bands have permeability values ∼4 orders of magnitude higher than undeformed rhyolite. Pore channels and fracture bands have much larger length scales, and so permeability increases dramatically in those systems. Hence, the abundance and interconnectivity of deformation features preserved in the Sandfell laccolith provided an efficient outgassing mechanism for the bulk of the intrusion. Outgassing due to viscous-brittle magma deformation during magma emplacement should therefore be considered for crystal-rich magmas, e.g., during effusive lava dome extrusion.

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引用次数: 0

Multiple dikes make eruptions easy

IF 2.4 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of Volcanology and Geothermal Research

Pub Date : 2025-02-03 DOI: 10.1016/j.jvolgeores.2025.108284

Agust Gudmundsson

Dikes supply magma to most volcanic eruptions. Understanding how propagating dikes may, or may not, reach the surface is thus one of the fundamental tasks for volcanology. Many, perhaps most, dike segments injected from magma sources do not reach the surface to feed volcanic eruptions. Instead, the dike segments become arrested (stop their propagation), commonly at or close to contacts between mechanically dissimilar layers/units, at various crustal depths. This means that many and perhaps most volcanic unrest periods with dike injections do not result in eruptions. There are several conditions that make dike arrest likely, but the main one is layering where the layers have contrasting mechanical properties. Such layering means that local stresses are heterogeneous and anisotropic and, therefore, in some layers unfavourable for dike propagation – hence the dike arrest. Here I show that once a dike has formed, however, its very existence tends to make the local stress field along the dike homogeneous (with invariable orientation of principal stresses) and favourable (with dike-parallel orientation of the maximum compressive principal stress) for later dike injections. This means that subsequence dikes may use an earlier dike as a path, either along the margin or the centre of the earlier dike, thereby generating a multiple dike. Because earlier feeder-dikes form potential paths for later-injected dikes to the surface, many volcanic eruptions are fed by multiple dikes. Examples include recent eruptions in the volcanoes Etna (Italy) and Kilauea (Hawaii), and the Icelandic volcanoes Krafla, Hekla, Fagradalsfjall, and the Sundhnukur crater row. Thus, multiple dikes favour dike propagation to the surface; thereby making dike-fed eruptions easier.

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引用次数: 0

The influence of graben geometry on dike propagation 地堑几何形状对堤坝扩展的影响

IF 2.4 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of Volcanology and Geothermal Research

Pub Date : 2025-02-01 DOI: 10.1016/j.jvolgeores.2024.108254

Khaled Rahimi , Marcus Bursik , Janine L. Kavanagh

Understanding dike behavior under varying topographical stresses is essential for predicting volcanic vent locations. This study addresses how graben geometry influences dike propagation by employing an experimental approach to simulate dike propagation, using fluids as analogs for magmas. We inject these fluids into the center of the base of an elastic gelatin medium, molded with an elongated topographic low representing a graben structure in the Earth's crust. Experiments involving different graben geometries were conducted to assess how local stress fields influence dike propagation. The results demonstrate that shallow grabens facilitate vertical to sub-vertical dike propagation within the graben, while deeper grabens cause dike deflection, often leading to off-graben venting or the formation of canoe-like sheet intrusions. These findings introduce new variables into the understanding of volcanic vent locations and eruption forecasts, particularly in rift zones with complex topography. The results offer critical implications for improving volcanic hazard assessments by incorporating the influence of topographical stress on dike propagation. Overall, the study advances our understanding of the mechanisms controlling dike propagation and provides a basis for further research into mitigating risks associated with volcanic eruptions in a graben setting.

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引用次数: 0

Magmatic differentiation and plumbing system beneath Nyamulagira volcano (Virunga Volcanic Province, East African Rift)

IF 2.4 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of Volcanology and Geothermal Research

Pub Date : 2025-02-01 DOI: 10.1016/j.jvolgeores.2024.108264

Ephrem Kamate Kaleghetso , Olivier Namur , Benoît Smets , Jacqueline Vander Auwera , François Lubala , Thomas Van Gerve , Sander M. Molendijk

Nyamulagira volcano (eastern Democratic Republic of the Congo) is one of Africa's most active volcanoes and poses a significant threat to the nearby rapidly expanding population centers. Situated in the Virunga Volcanic Province in the western branch of the East African Rift System, Nyamulagira's frequent eruptions offer a valuable opportunity to study effusive rift volcanism. However, understanding its subsurface processes remains challenging, impeding monitoring efforts.

Here, we report a comprehensive mineralogical, petrological, and geochemical study of rocks from historical eruptions at Nyamulagira. Mineral textures and compositions show strong spatial and temporal variations. We identify multiple active magma reservoirs in which magma compositions and textures evolve via crystal accumulation, fractional crystallization, magma recharge, mixing, and convection.

We distinguish three distinct reservoirs: a deep reservoir at ∼ 22–30 km depth, the main storage region at ∼ 13–18 km depth, and a shallow reservoir at ∼ 2–9 km depth. We propose that differentiation at Nyamulagira integrates olivine and clinopyroxene crystallization and accumulation in the deep reservoir, and fractional crystallization and magma mixing/homogenization in the interconnected intermediate and shallow reservoirs. Primitive magmas from the deep reservoir are predominantly emitted via distal eruptions, whereas more evolved magmas from the shallower reservoirs have been erupted on the flanks or at the summit caldera in recent decades.

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引用次数: 0

Corrigendum to “Evolution of a large Quaternary monogenetic field; the multifaceted volcanism of the Serdán-Oriental basin, México” [Journal Of Volcanology and Geothermal Research, 446 (2024) 107999]. 对 "一个大型第四纪单源火山场的演变；墨西哥塞尔登-东方盆地的多面火山活动 "的更正[《火山学与地热研究杂志》，446 (2024) 107999]。

IF 2.4 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of Volcanology and Geothermal Research

Pub Date : 2025-02-01 DOI: 10.1016/j.jvolgeores.2024.108239

Jaime Alberto Cavazos-Alvarez , Gerardo Carrasco-Núñez , Giovanni Sosa-Ceballos , Federico Lucci

引用次数: 0

Modeling magma recharge dynamics during the 2016 Nevados de Chillan eruption: An interacting two-chamber system evidenced by petrology and geodesy 2016 年奇兰内瓦多斯火山爆发期间的岩浆补给动力学建模：岩石学和大地测量学证明的互动双室系统

IF 2.4 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of Volcanology and Geothermal Research

Pub Date : 2025-02-01 DOI: 10.1016/j.jvolgeores.2024.108253

Camila Novoa Lizama , D. Remy , J.C. Baez , A. Oyarzun , S. Bonvalot , A. Hooper

The Nevados de Chillan is a large composite stratovolcanic complex located in the Southern Andean Volcanic Zone, at the south of Chile. Its last eruption spanned six years from January 8, 2016 until January 2023. After three years without any deformation, exhibiting phreatic and phreatomagmatic activity, an uplift episode was reported in June 2019, marking the start of its magmatic phase. How this geodetic activity evolved in the following three years is still not clear, neither how it correlates with its superficial activity. Here we analyze InSAR time series, as well as daily GNSS time series from 2015 to early 2022, highlighting the wide range of ground surface displacements observed during the eruption. In-depth analysis of these displacements together with recent petrological and geochemical results leads us to consider a recharge mechanism involving a double-reservoir model to explain the observed geodetic activity. We develop an analytical model of dynamic magma flow, which we coupled with a boundary element method to account for any geometry of the reservoirs and the topography of the volcano. The model consists of a shallow elongated source located at 5.8 km depth below the volcanic edifice connected by an incompressible magma-filled hydraulic pipe to a deeper sill like source centered at 15 km depth. We propose that the activation of the system started with a small magma intrusion of one month of duration, which was sufficient to overheat the hydrothermal system and re-mobilize magma in the shallow chamber, thus explaining the non-deformation during its phreatic phase and the slight subsidence observed during its phreato-magmatic stage. Then, we propose that a new and larger magma intrusion occurred in June 2019, explaining the uplift episode observed, which continued for the following three years of the eruption, decaying exponentially. Our model indicates that this intrusion was triggered by magma coming from the crust-mantle boundary to the deep reservoir at constant rate of 0.016 km³y⁻¹ from June 2019 to Jan. 2022, with small changes to this rate that would explain the small fluctuations observed during this uplift episode. We show that the conduit-dominated magma transfer between both reservoirs controls the dynamics of the system. A deep mafic reservoir recharging an evolved shallow reservoir would explain the mafic enclaves found in the dacites in the latter eruption and thus offers a physical model to jointly explain the observations we get from petrology, geochemistry and geophysics, bridging the disciplines. The model presented here can be used to study potential recharge mechanism occurring in the different stages of an eruptive cycle including pre-eruptive, co-eruptive and post-eruptive stages.

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引用次数: 0

Development of the Late Oligocene Zákupy Diatreme, Czech Republic: New insights into protracted diatreme emplacement

IF 2.4 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of Volcanology and Geothermal Research

Pub Date : 2025-02-01 DOI: 10.1016/j.jvolgeores.2024.108257

Vladislav Rapprich , Michael S. Petronis , Sarah F. Trevino , Jennifer Lindline , Benjamin van Wyk de Vries , Ondřej Pour , Zuzana Tasáryová , Matt Heizler

The Zákupy diatreme is well exposed by an abandoned quarry on Kamenický Vrch Hill (Czech Republic) located in the Lusatian (Lausitz) Volcanic Field in the eastern part of the NE-SW trending Ohře Rift. The abandoned quarry's walls extend upward over 50 m exposing the lower and upper diatreme facies. Petrographic analyses revealed two main compositionally distinct suites of intrusive and extrusive bodies: dikes, sills, and lava-lakes with relics of fine-grained basanite (to limburgite) and a set of rhönite-bearing picrobasalt dikes and sills. The parallel, almost linear, and relatively fractionated (La_N/Yb_N 21.98–26.21) chondrite-normalized REE patterns suggest the erupted magmas originated through low-degree partial melting and did not undergo any significant fractionation. Close relationships between basanites and picrobasalts is confirmed also with mineral chemistry with almost identical compositional trends of clinopyroxene and spinel-group phases. The negligible difference between bulk-rock Mg# (0.71–0.72 for basanites and 0.74 for picrobasalts) and melt Mg# calculated from olivine composition (0.70 for basanites and 0.68–0.70 for picrobasalts) reflects rather a load of mantle-derived (high Mg#) xenoliths and xenocrysts rather than the presence of cummulitic olivine. Anisotropy of magnetic susceptibility data reveals magnetic fabrics of variable orientations that reflect upward, downward, and subhorizontal magma flow within the diatreme complex. Paleomagnetic data fall into three general groupings that we interpret to reflect magma emplacement during at least three phases. These data also support tilting, rotation, and slumping of diatreme host rocks causing physical displacement of the intrusions following remanence acquisition. Four new ⁴⁰Ar/³⁹Ar age determinations from the picrite (n = 1) and basinite (n = 3) yield relatively undisturbed age spectra that constrain the age of emplacement between 31.24 and 32.40 Ma, indicating that magmatic evolution of the Zákupy diatreme spanned 1.2 million years. This multidisciplinary study reveals that the Zákupy diatreme evolved from several similarly sourced magmatic pulses. Repeated molten fuel coolant interactions produced a complex diatreme setting consisting of multiple eruptive events leading to coherent intrusions, various pyroclastic and hyaloclastite materials, local contact metamorphism, and other evidence of explosive hot rock-fluid interactions. The complex evolution and eruptive behavior, together with a protracted time of the diatreme activity, illuminate that small, seemingly simple volcanoes experience a very dynamic evolution involving multiple intrusive events, changing eruptive styles, and surface morphologies.

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引用次数: 0

Magmatic processes associated with the 2020 eruption of Taal Volcano, Philippines, revealed by local seismic source estimates

IF 2.4 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of Volcanology and Geothermal Research

Pub Date : 2025-02-01 DOI: 10.1016/j.jvolgeores.2024.108256

Hiroyuki Kumagai , Ma. Antonia Bornas , Winchelle Ian Sevilla , Rudy Lacson Jr , Melquiades S. Figueroa II , Christian Joseph Clarito , Azusa Mori , Miki Hamamoto

After 43 years of repose, Taal Volcano (Philippines) erupted on 12 January 2020 with plumes reaching 17 km above sea level. To investigate Taal's magma system before, during, and after the 2020 eruption, we performed detailed analyses of local seismic data using the amplitude source location (ASL) method to estimate sources of volcano-tectonic (VT) earthquakes and tremor. Our ASL estimates indicate that magma intruded beneath the northern flank of Taal Volcano Island (TVI) before the main sustained eruption, which started at 06:40 UTC on 12 January 2020 and continued for about 14 h. Within one hour after the start of the eruption, magma emplacement along an inclined magmatic dike from a magma reservoir initiated. Seismically estimated plume heights during the eruption show that plumes were initially almost continuously higher than 10 km, then intermittently fluctuated while the base-level height of the sustained plume gradually decreased. After the eruption, tremor episodes occurred at depths down to 8.5 km beneath TVI along the northern end of a dike. Our study highlights the drastic change of Taal's magmatic system from a closed to an open system during the 2020 eruption. Before the eruption, Taal had been a closed system, and the increased pressure caused by renewed magma supply to a magma reservoir produced heightened VT activity within the edifice. The eruption opened the vent–conduit system, and CO₂ and/or SO₂ degassing within the conduit may have generated gas flows through shear-induced fractures in the conduit margins, triggering tremor episodes at various depths.

经过 43 年的沉寂，菲律宾塔尔火山于 2020 年 1 月 12 日喷发，火山羽流高达海平面 17 公里。为了研究塔尔火山在 2020 年喷发前、喷发期间和喷发后的岩浆系统，我们使用振幅源定位（ASL）方法对当地地震数据进行了详细分析，以估计火山构造地震（VT）和震颤的来源。我们的振幅源定位估算结果表明，在塔尔火山岛（TVI）主要的持续喷发之前，岩浆就已经侵入了该岛的北侧，喷发从 2020 年 1 月 12 日世界协调时 06:40 开始，持续了约 14 小时。喷发期间的地震估计羽流高度显示，羽流最初几乎持续高于 10 公里，然后间歇波动，而持续羽流的基底高度逐渐降低。火山爆发后，沿堤坝北端的 TVI 地下最深处发生了 8.5 千米的震颤。我们的研究强调了塔尔火山岩浆系统在 2020 年喷发期间从封闭系统到开放系统的巨大变化。喷发前，塔尔火山是一个封闭系统，由于岩浆库的岩浆供应增加，导致压力增大，火山口内的 VT 活动加剧。喷发打开了喷口导管系统，导管内的二氧化碳和/或二氧化硫脱气可能通过导管边缘的剪切裂缝产生气体流，引发了不同深度的震颤。

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引用次数: 0