Volcanic Processes Research Articles

Rifting Basins at the Accretion-Collision Stage of Fold Belt Development: Eastern Slope of the Southern and Middle Urals in the Carboniferous

Research subject. Sedimentary basins within the Mississippian and Early Pennsylvanian (Middle Carboniferous of Russia) rift (sensu lato) structures on the eastern slope of the Southern and Middle Urals. Methods. An analysis of lithological characteristics of sedimentary rocks and relationships with volcanic complexes in order to clarify the evolution of rifting basins. Results. During the Mississippian and Early Pennsylvanian, several large rifting basins were common in this area. The Early Carboniferous rifting basins (Magnitogorsk-Bogdanovskoe graben and Alapaevsk-Kamensk rift) of accretionary margin of the East European craton were characterized by relatively shallow-water (in some places up to coastal-marine and continental) environments, caused by intensive (compensatory) filling of depressions with sedimentary material. In this case, volcanic rocks – those of fissure-type and stratovolcanoes lava flows – also played a significant role. In the Late Visean, the rifting process paused; a relatively shallow shelf basin regime was established throughout the entire area, which persisted until the end of the Early Carboniferous. In the Early Pennsylvanian, due to a hard oblique collision, the rifting process resumed. However, the rifting basins were already smaller in terms of area and most often deeper, whereas the occurring volcanic processes were less intensive. The characteristic feature of these basins was the presence of flysch complexes. The elongated shape of the rifting basins, large thicknesses of sedimentary strata, lateral facies variability, and the abundance of coarse clastic rocks, consisting largely of fragments of directly underlying sediments (Visean, Serpukhovian, Bashkirian), suggest that the Mississippian and Early Pennsylvanian rifts of the Southern and Middle Urals eastern slope had a strike-slip nature, i.e., the rifting basins were pull-apart type depressions.

Experimental access to volcanic eruptions

Well-chosen experiments provide access to a vast array of magmatic and volcanic processes, from magma transport within the lithosphere through volcanic eruptive phenomena to the fate of erupted materials in the earth system. This selected overview of contributions from our labs collates examples from early work on rheology and fragmentation to some recent experimental excursions into postfragmentation modification and the thermal and chemical journey of lavas and pyroclasts leading up to their deposition and lithification.

Control of slab tears and slab flat wedging on volcanism in the Alaska subduction zone

Multistage plate subduction plays a crucial role in magmatism; however, the mechanisms by which deep geodynamic processes govern volcanism in the Alaska subduction zone remain controversial. Using numerous travel-time data from several seismic arrays, we constructed high-resolution tomographic models to investigate the velocity structure of the Pacific Plate and Yakutat slab. Our tomographic results revealed high-velocity anomalies in the Pacific Plate and Yakutat slab, while the low-velocity areas within the Pacific Plate were identified as slab tears. We suggest that the Pacific Plate transitioned from oblique subduction along the Aleutian volcano chain to lower-angle subduction beneath the Pacific-Yakutat Plate interaction zone, forming two slab tears that enhance hot asthenosphere materials upwelling. The partial melting of the mantle wedge induced by Pacific slab dehydration and the concurrent upwelling of mantle materials jointly drove volcanism in the transition zone. Conversely, the flat subduction of the Yakutat slab into the mantle wedge overlying the Pacific slab effectively hindered the upwelling of hot hybrid materials, cooling the Pacific mantle wedge. These results offer a new perspective on the influence of slab dynamics on volcanic and magmatic processes in the region and represent an advancement in our understanding compared to previous studies, which did not resolve the tears within the slab or their geodynamic implications at this level of detail.

Identification of Paleovolcanic Centers in the Bima District, East Sumbawa Island (Indonesia) as Guidance for Future Exploration of Cu-Au Deposits

The formation of Cu-Au mineralization, such as porphyry and epithermal deposits, is strongly associated with volcanic processes in specific tectonic settings, such as subduction zones. The identification of the presence of ancient volcanoes is one of the important steps to finding mineral deposits. This study aims to identify the presence of ancient volcanoes in the Bima District, eastern part of Sumbawa Island, as a step toward determining the potential indication of Cu-Au mineralization. The methods used in this research consist of a literature study, image analysis and remote sensing, field survey and data collection, and petrographic analysis. Image analysis using DEMNAS (Digital Elevation Model), including texture and pattern analysis using the concept of volcanic anatomy, aims to identify the remaining forms of ancient volcanoes. Field surveys and data collection include volcano geomorphology, lithology and sampling, and also geological structures. Petrographic analysis is conducted to qualitatively characterize the texture, structure, and mineralogy of volcanic rocks. The identification results show that there are at least ten volcanoes (crown) identified through image analysis, namely Doro Mbangga, Doro Baku, Doro Donggo Masa, Doro Rompo, Doro Sape, Doro Kowo, Doro Jia, Doro Sambori, Doro Mangge, and Doro Lambu. Each of these volcanoes has one or more eruption center (hummock). The eruption center identified in the central, proximal, to distal facies of the volcano, even superimposing one volcano product with another, and spread around 80-90% in the study area. The volcanic facies in the study area are characterized by the central part being composed of lithologies such as intrusive rocks, lava, and diatreme breccia, while the proximal and distal facies are composed of breccia, volcanic breccia, and tuff. Hydrothermal alteration zones are identified in the central and proximal facies of the volcano. These alterations were associated with the presence of eruption centers, where the abundance of eruption centers means that hydrothermal alterations are particularly well developed and pervasively formed. Identified argillic and advanced argillic alteration associated with stockworks forming a lithocap environment. In addition, the presence of intrusive rocks such as diorite and dacite with chloritic and sericitic alteration in the central facies of Doro Baku can be associated with the presence of deposits such as porphyry and epithermal, so the identification of ancient volcanic eruption centers in the Bima district has implications for the potential discovery of Cu-Au mineralization, such as porphyry and epithermal deposits.

Applications of paleomagnetism and rock magnetism in understanding volcanic processes and timescales: perspectives to Korean volcanological research

Applications of paleomagnetism and rock magnetism in understanding volcanic processes and timescales: perspectives to Korean volcanological research

Variable preservation of the 1991 Hudson tephra in small lakes and on land

Volcanic ash (tephra) preserved in terrestrial environments and lake sediments contains information about volcanic processes and can be used to infer eruptive parameters and frequency of past eruptions, contributing to the understanding of volcanic hazards. However, tephra deposits can undergo transformation from their initial fallout sedimentation to being preserved as a tephra layer in the sedimentary record. The process is likely to be different in lakes and in terrestrial (soil) sequences. Here we compare the thickness, mass loading and grain size of tephra layers from the 1991 eruption of Cerro Hudson, Chile, from small lakes and adjacent terrestrial settings to measurements of the tephra made shortly after the eruption. We analysed samples from 35 cores in total from six small lakes (<0.25 km2), located 76 and 109 km from the volcano in two contrasting climatic areas (cool and humid northern site, and warm and dry southern site), and made 73 measurements of tephra thickness and 11 measurements of grain size in adjacent terrestrial areas. The major element geochemistry of our samples confirmed they were from the 1991 Hudson eruption. We found that some of the measured characteristics of the preserved tephra layers were comparable to those recorded in 1991 shortly after initial deposition, but that there was considerable variability within and between locations. This variability was not predictable and lake sediments did not preserve a notably more accurate record of the fallout than terrestrial sites. However, in aggregate the characteristics of the preserved tephra was similar to those recorded at the time of deposition, suggesting that, for palaeotephra research, a sampling strategy involving a wide range of environments is more robust than one that relies on a single sedimentary record or a single type of sedimentary environment.

Physical Modeling of Tsunamis Generated by Submarine Volcanic Eruptions

AbstractSubmarine volcanic eruptions can induce major local and regional tsunami hazards through varied source mechanisms. Large‐scale experiments of tsunamis generated by submarine volcanic eruptions are conducted to study the cylindrical wave generation and propagation in a three‐dimensional wave basin. A unique volcanic tsunami generator (VTG) was deployed at the bottom of the wave basin to generate volcanic tsunamis with repeatable and controlled source parameters. The physical modeling is based on the generalized Froude number defined with the VTG velocity and the near source water depth. The pneumatically driven vertical stroke motion generates leading elevation waves in the wave basin. The tsunami waves generated by the VTG are measured with a wave gauge array. The wave maker performance is characterized by the dimensionless leading wave amplitudes and periods. The experimental data show the variations of the leading wave amplitude, period, and celerity along the radial propagation distance. The generated cylindrical waves belong to the weakly nonlinear wave regime in the near field with decaying wave amplitude along radial propagation. The attenuation rate of the leading wave exceeds the range from the linear wave theory in runs with higher Froude numbers. The dimensionless leading wave period increases with the dimensionless propagation distance due to the dispersion relation. Empirical equations for the characteristic wave parameters such as amplitudes and periods are derived. The experimental results contribute to the understanding of volcanic tsunami generation processes and may serve rapid volcanic tsunami hazard assessments as well as the advancement and validation of numerical models.

Novel age constraints on offshore islets around Taiwan with implications for the Northern Taiwan Volcanic Zone

Determining the exact age of volcanic activity in the Northern Taiwan Volcanic Zone (NTVZ) is essential for comprehending Taiwan's tectonic evolution. The timing and duration of the volcanic processes that formed the NTVZ remain uncertain despite the availability of geochronological, geochemical, and geophysical data. While extensive efforts have been directed towards investigating the age of the Tatun Volcanic Group, the primary feature of the NTVZ, many other aspects require further examination. This study concentrates on two offshore islets in the northern region of the NTVZ. We present new 40Ar/39Ar ages of 0.252 ± 0.018 Ma for a lava flow, representing an early stage of volcanic activity, and 0.118 ± 0.012 Ma for a dike, representing the latest stage of volcanic activity around Pengjia Islet. A sample collected from Mianhua Islet did not yield a reasonable age due to high uncertainty, likely attributable to young and low radiogenic argon. Field observations support the interpretation that volcanic activity on both islets is considerably younger than previously estimated. This study corroborates the hypothesis from geophysical studies that submarine NTVZ features to record a potentially active magmatic reservoir offshore of northern Taiwan. By refining our understanding of spatio-temporal patterns in volcanic activity, this study contributes to volcanic hazard assessment in Taiwan and surrounding areas.

Mildly explosive eruptions at Martian low-shield volcanoes

AbstractOngoing acquisition of Martian surface imagery constantly provides new opportunities to reveal previously undiscovered small-scale volcanic landforms, yielding critical insights into volcanic processes, and challenging existing inferences. Here, using the most recent, high-resolution topographical data, we mapped the accumulation of pyroclastic deposits occurring along the margins of several volcanic vents. They share morphological similarities with terrestrial volcanic deposits attributed to low-intensity lava fountaining occurring during mild explosive activity. Our identified, explosive volcanic deposits are associated with late Amazonian volcanic activity in Tharsis. The identification of these very recent (<100 Ma) deposits across the entire Tharsis volcanic province needs reconciling with our current view of the evolution of explosive volcanism on Mars. We contend that these small volume landforms, produced by mildly explosive volcanic activity, need to be considered in models surrounding planet-scale magmatic evolution and atmospheric volatile budgets.

Global carbon cycle disruption during the latest Pliensbachian (Lower Jurassic) evidenced by simultaneous isotopic depletion in marine and terrestrial carbon pools

The Pliensbachian-Toarcian (Pl-To) boundary was marked by an extinction event in marine organisms, and localised ocean anoxia – resulting in the deposition of black shales. Negative isotopic excursions in bulk organic carbon in many of these black shales, are widely believed to indicate that a global carbon cycle disruption accompanied this extinction event. The Pl-To preceded a period of more intense global carbon cycle disruption that occurred during the Toarcian Oceanic Anoxic Event (T-OAE) by around a million years. It is evident from targeted carbon isotopic analyses of marine and terrestrial organic matter that simultaneous disruptions to the marine and terrestrial carbon cycles occurred during the T-OAE. However, it remains a matter of debate whether the main source of carbon emissions was a climate-sensitive methane reservoir, or volcanic processes. No records of terrestrial carbon cycle disruption exist for the latest Pliensbachian, and so the causal mechanisms behind localised anoxia in this stage of the Lower Jurassic are poorly constrained. We present a record of concomitant isotopic depletion in short and long-chain n-alkanes derived from a thin black shale (the Lower Sulphur Band – LSB) deposited during the latest Pliensbachian (located in Yorkshire, UK). A key argument is that simultaneous isotopic depletions in these different compound classes implies the presence of a brief global hyperthermal event in the latest Pliensbachian, with a timescale too short to have been captured by previous analyses of the Yorkshire section. We discuss the relevance of our data to the stratigraphic record of the Lower Jurassic sediments of Yorkshire, highlighting, in particular, the need for better constraint on the ammonite biostratigraphy of the study section. We further argue that the brief climate disruption that occurred in the latest Pliensbachian made the shallow marine environment vulnerable to the development of more widespread marine anoxia, during the succeeding Toarcian stage.

Twenty Years of Thermal Infrared Observations (2004–2024) at Campi Flegrei Caldera (Italy) by the Permanent Surveillance Ground Network of INGV-Osservatorio Vesuviano

Thermal infrared (TIR) time series images acquired by ground, proximal TIR stations provide valuable data to study evolution of surface temperature fields of diffuse degassing volcanic areas. This paper presents data processing results related to TIR images acquired since 2004 by six ground stations in the permanent thermal infrared surveillance network at Campi Flegrei (TIRNet) set up by INGV-Osservatorio Vesuviano. These results are reported as surface temperature and heat flux time series. The processing methodologies, also discussed in this paper, allow for presentation of the raw TIR image data in a more comprehensible form, suitable for comparisons with other geophysical parameters. A preliminary comparison between different trends in the surface temperature and heat flux values recorded by the TIRNet stations provides evidence of peculiar changes corresponding to periods of intense seismicity at the Campi Flegrei caldera. During periods characterized by modest seismicity, no remarkable evidence of common temperature variations was recorded by the different TIRNet stations. Conversely, almost all the TIRNet stations exhibited common temperature variations, even on a small scale, during periods of significant seismic activity. The comparison between the seismicity and the variations in the surface temperature and heat flux trends suggests an increase in efficiency of heat transfer between the magmatic system and the surface when an increase in seismic activity was registered. This evidence recommends a deeper, multidisciplinary study of this correlation to improve understanding of the volcanic processes affecting the Campi Flegrei caldera.

Event classification, seismicity, and eruption forecasting at Great Sitkin Volcano, Alaska: 1999–2023

The frequency content of volcanogenic seismicity is often used to classify events and their spatial and temporal progression is then used to map subsurface volcanic processes. The progression of volcano-seismic events and associated source processes also plays a critical role in eruption forecasting. Here we develop and evaluate a computerized methodology for characterizing volcano-seismic event types using Frequency Index and Average Peak Frequency. We apply and test this technique at Great Sitkin Volcano, Alaska, classifying over 9000 hypocenters between 1999 and 2023. This 24-year time span covers periods of seismic quiescence, earthquake activity on nearby tectonic (bookshelf) faults, precursory unrest from 2016 to 2021, and the explosive onset in May 2021 of the ongoing effusive eruption. We use the spatial and temporal evolution of classified event types to map the active volcanic and tectonic processes, develop a conceptual model of the subsurface magmatic system, and perform a retrospective analysis of eruption forecasts at Great Sitkin Volcano between 2016 and the present. The classification and progression of hypocenters suggests the subsurface Great Sitkin Volcano magmatic system consists of a mid- to lower- crustal source zone between 10 and 40 km depth and an upper crustal magma storage area between −1 and 10 km depth (hypocenter depth is referenced to sea level and negative depths reflect height above sea level). The earliest precursors occurred in July 2016 and consisted of deep long-period and volcano-tectonic earthquakes at mid-crustal depths suggesting the subsequent unrest and eruption were triggered by a deeper intrusion of magma. This mid-crustal seismic activity was immediately followed by the onset upper-crustal long-period events and volcano-tectonic earthquakes VTs suggesting a strong linkage between the shallow and deeper portions of the magmatic system. The upper crustal area was likely capped by the 1974 lava dome until the magmatic explosion on May 26, 2021.

Prospects for the allocation of Paleorousels in the subsalt complex of the south-east of the Caspian sedimentary basin

development and features of the formation of the sedimentary complex of the south of the Caspian sedimentary basin are presented. The complex geological structure of the region is mainly due to the influence of tectonic, volcanic and denudation processes on sedimentation. The introduction of terrigenous material deep into the sedimentary basin (Matken-Ushmolinsk, Biikzhal and South Embin zones) by paleorubic flows contributed to the emergence of accumulative shafts and interbranch uplifts composed mainly of clay rocks with alternating siltstone-sandstones. In the paleorusls themselves, coarser sediments were deposited – gravelites and sandstones. The reconstruction of the conditions of formation of sand bodies made it possible to predict their facies composition, morphology and identify patterns of spatial placement, and are also of great interest in the search for oil and gas deposits in deep-lying lithological traps. The prospects of these structures and their resource potential are evidenced by the world experience in identifying large deposits of hydrocarbon raw materials. This is a new highly promising direction of large accumulations of hydrocarbons for the Caspian Basin. The results of drilling deep wells conducted in recent years have made it possible to refine the internal structure, substantiate new facilities in the Late Paleozoic sedimentary complex, and reassess the prospects of oil and gas potential and forecast oil and gas resources of the south of the Caspian Basin.

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

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.

Active deformation in the central section of the East African Rift from tectonic, volcanic, and hydrologic processes: Observations from satellite geodesy

The East African Rift System (EARS) is an active continental rift zone that hosts a diverse range of processes that result in recent and ongoing crustal deformation. To analyze these processes, we used Sentinel-1 Interferometric Synthetic Aperture Radar (InSAR) to complement the sparse GNSS velocity field with high resolution measurements of line-of-sight (LOS) deformation between 2015 and 2022. A broad survey approach was employed to detect new signals within the central section of the EARS, and to establish a baseline for future studies focused on tectonic, volcanic, and/or hydrologic deformation and change spanning geodetic time scales. With this regional approach, we were able to resolve signals varying over time-spans of a few weeks to several years that have magnitudes greater than ∼1 cm/yr. Our resulting deformation field shows a diverse range of signals related to the processes listed above as well as other unknown sources. This includes up to 8.5 cm/yr of groundwater-related subsidence in Nairobi, up to 70 cm of LOS displacement during the eruption of Nyiragongo in 2021, and steady uplift in the Manyara basin with a rate of 2.8 cm/yr. We update previously published InSAR measurements of Mount Suswa volcano, and the geothermal fields in Olkaria. We also show LOS change ranging between 2 and 5 mm/yr over a distances of approximately 200 km spanning the Kenya Rift with the greatest differential rates occurring south of Lake Turkana. More generally, our results highlight the ambiguity of relying solely on the sparse network of GNSS for studies such as those characterizing tectonic motion and rift opening. Such studies are likely missing many important signals and/or includes sites that are contaminated with signals unrelated to the target process.

Volcano-tectonic controls on the morphology and volcanic rift zone configuration on Bioko Island (Equatorial Guinea) derived from TanDEM-X data

The morphology of the shield volcanoes on Bioko, a volcanic island in central Africa, is controlled both by tectonic and volcanic processes, but the complex interplay of these regional and local mechanisms is poorly understood. Using a TanDEM-X digital elevation model, we are able to create an inventory of 436 vents and monogenetic cones, and over 1330 structural elements and lineaments, and perform a comprehensive morphological and geospatial analysis. We provide detail on the general geomorphology of Bioko Island, and describe its flat top, apical graben-like structures, and the setting of the structural inventory created. Based on vent density and lineament mapping, we are able to identify volcanic rift zones that are governed by vent clustering and the asymmetry of associated monogenetic cones. Specifically, we find that eruption vents are not only clustered but aligned and follow the principal NE-SW axis, although we also highlight evidence for complex structures such as side-stepping alignments and en échelon patterns indicative of strike-slip contributions to the volcano-tectonic fabrics. We discuss possible volcano-tectonic and regional tectonic contributors, such as the Cameroon Volcanic Line and intersecting fracture zones, as well as gravity-tectonic processes dominant at Bioko Island. In this view, our results are relevant for understanding the past and recent volcanic activity and discuss the influence of regional and local volcano-tectonic architectures.

Metal variability in small pelagic fish Scomber colias as influenced by volcanic events in the Canary Islands.

Offshore volcanic activity occurs when an underwater volcano erupts. These volcanoes can be located underwater or on land and can be very dangerous to marine life. The aim of this study is to examine whether the influence of two volcanoes has an effect on the concentrations of metals and trace elements in the Atlantic mackerel Scomber colias in the Canary Islands. For the study, ten specimens of S. colias were obtained from each sampling area in March 2022. Metal concentrations were determined by inductively coupled plasma optical emission spectrophotometry (ICP-OES). The specimens of Scomber colias from the area affected by the Tajogaite volcano (La Palma) showed higher concentrations of all metals and trace elements analyzed than those from the other study areas. The specimens from the area of influence of the Tagoro Volcano (El Hierro) showed the second highest concentration of the elements studied, although this volcanic process is in a state of degassing.

Volcanic Eruption in the Nanoworld: Efficient Oxygen Exchange at the Si/SnO2 Interface.

Here, a phenomenon of efficient oxygen exchange between a silicon surface and a thin layer of tin dioxide during chemical vapor deposition is presented, which leads to a unique Sn:SiO2 layer. Under thermodynamic conditions in the temperature range of 725-735°C, the formation of nanostructures with volcano-like shapes in "active" and "dormant" states are observed. Extensive characterization techniques, such as electron microscopy, X-ray diffraction, synchrotron radiation-based X-ray photoelectron, and X-ray absorption near-edge structure spectroscopy, are applied to study the formation. The mechanism is related to the oxygen retraction between tin(IV) oxide and silicon surface, leading to the thermodynamically unstable tin(II)oxide, which is immediately disproportionate to metallic Sn and SnO2 localized in the SiO2 matrix. The diffusion of metallic tin in the amorphous silicon oxide matrix leads to larger agglomerates of nanoparticles, which is similar to the formation of a magma chamber during the natural volcanic processes followed by magma eruption, which here is associated with the formation of depressions on the surface filled with metallic tin particles. This new effect contributes a new approach to the formation of functional composites but also inspires the development of unique Sn:SiO2 nanostructures for diverse application scenarios, such as thermal energy storage.

The influence of temperature (up to 120 °C) on the thermal conductivity of variably porous andesite

The thermal conductivity of volcanic rock is an essential input parameter in a wide range of models designed to better understand volcanic and geothermal processes. However, although volcanoes and geothermal reservoirs are often characterised by temperatures above ambient, laboratory thermal conductivity measurements are often performed at ambient temperature. In addition, there are currently few data on the temperature dependence of thermal conductivity for andesite, a common volcanic rock. Here, we provide elevated-temperature (up to 120 °C) laboratory measurements of thermal conductivity for variably porous (∼0.05 to ∼0.6) and variably glassy andesites from Mt. Ruapheu (New Zealand) using the transient hot-strip method. Our data show that (1) the thermal conductivity of these andesites has little to no temperature dependence and, therefore, (2) there is also no influence of porosity on the temperature dependence of thermal conductivity. We compare our new data with compiled published data to show that the thermal conductivity of volcanic rocks may decrease, remain constant, or increase as a function of temperature. We show that the thermal conductivity of amorphous glass and crystalline material increase and decrease, respectively, as temperature increases. We therefore interpret the temperature dependence of the thermal conductivity of volcanic rock to be dependent on glass content. The thermal conductivity of the studied andesites, the microstructure of which can be characterised by phenocrysts within a variably glassy groundmass, has little to no temperature dependence because the decrease in the thermal conductivity of the crystalline materials, due to decreases in lattice thermal conductivity, is offset by the increase in the thermal conductivity of the amorphous glass. A simple modelling approach, using the temperature dependence of the thermal conductivity of glass and crystalline material, provides a crystal content of 0.26 for a thermal conductivity independent of temperature, a common crystal content for andesite dome rock. Our findings imply that calculations of heat transfer through partially glassy volcanic rocks need not consider a temperature-dependent thermal conductivity, but that decreases and increases in thermal conductivity with temperature should be expected for fully crystallised or devitrified volcanic rocks and completely glassy volcanic rocks, respectively. We highlight that more experimental studies are now required to assess the evolution of thermal conductivity as a function of temperature in a wide range of volcanic rocks with different crystallinities.

Heat pulse−dominated magmatic storage: The 33 ka dacite dome eruption at Taápaca volcano (Central Andes)

We present 40Ar/39Ar ages of dacite domes and rare volcanic sanidine megacrysts from Taápaca volcano (northern Chile) that record 1.3 m.y. of activity. Our focus is on 20 megacrysts from a single 32.9 ka eruption. We interpret that their surprisingly correlated Ba-rich and Ba-poor growth zones separated by resorption surfaces reflect frequent heat pulses with a uniform thermal history over >300 k.y. of growth. We infer extended storage in small (<400 m), shallow “hot” domains within a larger magma system. Our findings bear on the origin of K-feldspar megacrysts in plutonic rocks, thus linking volcanic and plutonic processes in shallow silicic magma systems, and support protracted residence of hot magma in small batches at upper-crustal levels to produce megacryst-bearing granitoid intrusive complexes.