Pyroclastic Flows Research Articles

Pumice cone eruptions at Aluto volcano, Ethiopia

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.

Cascading hazards in volcanic environments: monitoring, modelling and impact analysis of tsunamigenic flows for risk reduction

Volcanic environments present complex multi-hazard scenarios where primary volcanic activity can trigger cascading hazards or where multiple hazards can occur simultaneously, leading to cascading and compounding impacts on communities and ecosystems. Stromboli, one of the most active volcanoes globally, exemplifies these challenges with its frequent eruptions, pyroclastic density currents, landslides, and tsunamis. In the present study, the mechanisms behind tsunamigenic flows at Stromboli are investigated by using extensive monitoring data from previous studies and numerical modelling. Key findings from simulations and parametric analysis are presented, showing the relationships between mass flow dynamics, morphological factors, and tsunami generation. A more comprehensive context is then considered by drawing the impact chain related to tsunamigenic flows during a volcanic eruption. This includes a broad evaluation of the exposure, vulnerability and possible mitigation measures. Starting from the study of the hazard and then following up with the evaluation of the impacts, this study emphasizes the necessity of a holistic approach in multi-hazards environment, where accurate hazards modelling and monitoring, interdisciplinary collaboration, and community engagement need to be considered to reduce risk.

The ad 79 Vesuvius eruption revisited: the pyroclastic density currents

Seventeen pyroclastic density currents (PDCs) were produced before, during and after the Plinian phase of the ad 79 eruption of Vesuvius. Their deposits were correlated using the proportions of components, together with the recognition of distinctive intercalated regionally traceable fall marker layers, revealing sectoral and distance-dependent variations. During an extensive field analysis, 27 lithostratigraphic units were detected and mapped and the lateral and vertical variations of 15 lithofacies were documented, described and interpreted. The total volume of PDC units is 1.25 km 3 . We consider that the early PDCs were generated by partial collapses from the sustained Plinian eruption column, whereas the subsequent post-Plinian PDCs were generated by more sustained pyroclastic fountaining. New facies mapping revealed lateral migration and extended travel distances for some of the currents. Most of the lobed PDCs remained relatively uniform, whereas the radial PDCs exhibited fluctuating waxing and waning pulses and changed gradationally down-current. Re-evaluation of the timing of caldera collapse and the transition from a magmatic to a phreatomagmatic eruption style suggests that substrate fracturing during incremental caldera subsidence may have allowed the gradual ingress of groundwater into the erupting magma. These results provide a new chronology of the eruption, revealing that the post-Plinian collapse phase lasted c. 12 h.

The ad 79 Vesuvius eruption revisited: Plinian and post-Plinian falls

The well-exposed Plinian fall deposit of the ad 79 Vesuvius eruption is herein divided into 12 lithostratigraphic units: seven units in the white pumice deposit and five units in the grey pumice deposit. These distinct units are distinguished by significant variations in grain size and the ratio of lithic to juvenile clasts, enabling us to reconstruct the highly fluctuating dynamics of the eruptive column during the Plinian phase of the ad 79 eruption with previously undetected detail. These characteristics allow their distributions around the vent to be mapped, showing that the plume fluctuated between 14 and 34 km in height, depositing 6.4 km 3 of tephra in 17 h. To broaden the scope of our investigation, we extended our research to encompass five lithic-rich fall layers that occurred after the Plinian phase, providing information on the dispersion and eruptive parameters of these late fallout phases. Post-Plinian sustained column pulses persisted for several tens of minutes, with the first pulse being the longest, lasting for 44 min. This initial pulse possibly facilitated the attempts made by numerous Pompeians to flee the city following the arrival of the first two weak pyroclastic density currents.

Geology, Archaeology, and Historical Studies of the Late 16th Century Plinian Eruption of Raung Volcano: A Potential Case for Disaster Geotourism in Ijen UNESCO Global Geopark, East Java, Indonesia

The enigmatic major eruption in the late 16th century, believed to have originated from Raung, the most active stratovolcano in the Ijen UNESCO Global Geopark in East Java, Indonesia, has ignited significant debate among researchers and historians due to its profound impact on the region. This research aims to substantiate Raung as the likely source of the major eruption by integrating geological, archaeological, and historical data. This study synthesizes current findings and explores ongoing debates surrounding historical volcanic activities. Eruption parameters suggest that the late 16th century eruption exhibited a Plinian type, characterized by an explosive eruption column reaching the stratosphere, widespread pumiceous tephra fallout, and pyroclastic density current (PDC). Stratigraphic succession reveals that the eruption occurred in five phases, with deposits from 10 eruptive units. These deposits are mainly concentrated on the northwestern flank of Raung. Archaeological findings, historical records, and local legends converge to pinpoint the occurrence of this catastrophic event in the late 16th century. These diverse sources estimate that the eruption resulted in approximately 10,000 casualties, marking it as one of the most significant volcanic disasters in the past 500 years. The implications of this eruption extend beyond historical documentation, providing a critical case study for advancing disaster mitigation strategies through geotourism in the geopark area. Moreover, the eruption record outcrops identified in this study can be proposed as potential new geosites within the Ijen UNESCO Global Geopark, enhancing its educational and touristic value. We propose the Jebung Kidul, Alas Sumur, and Batu Sappar sites as potential disaster-based geosites, considering that these sites record the eruption process and preserve archaeological structures. This addition would not only commemorate the historical event but also promote awareness and preparedness for future volcanic activities in the region.

Insight into the 2021 Semeru volcano eruption from rapid monitoring of its pyroclastic deposits using Google Earth Engine and multi-sensor data

The objective of this study is to map the pyroclastic deposits resulting from the Semeru eruption in 2021 and to analyse the process of pyroclastic deposit formation, including the tephra and lithification phases, using multi-sensor data. The distribution of pyroclastic deposits was mapped using machine learning algorithms, Sentinel 2 and Sentinel 1 imagery on Google Earth Engine. Data acquisition in the Semeru volcano area was conducted both prior to and following the 2021 eruption. Additionally, field investigations were conducted to analyse the distribution of pyroclastic deposits, including the characteristics of individual layers, the lithification process of pyroclastic layers, and their relationship with the characteristics of the eruption. The results demonstrate that pyroclastic deposits in the proximal facies are composed of lithic, lapilli tuff, lava and tuff. The mapping results also indicate the presence of volcanic ash deposits in the central facies or summit area of Semeru, exhibiting distinctive characteristics associated with volcanic ash. The 2021 eruption has also resulted in rapid changes to river morphometry, as evidenced by notable shifts in a significant decrease in pixel values for NDVI (−0.0781-0.0625), a significant increase in pixel frequency of EVI (1800–6000), and MNDWI (1700–3000), respectively. The change of pyroclastic fall into consolidated tephra occurred from December 2021 to May 2023, where in May 2023 volcanic ash had changed into tuff and lapilli had changed into lapilli tuff. Furthermore, data from Sentinel-1 indicated that pyroclastic flows could be identified using both vertical and horizontal polarization. It can therefore be concluded that the 2021 eruption of Semeru exhibited distinctive characteristics of pyroclastic deposits, where some of the characteristics of the pyroclastic distribution can be monitored rapidly with Google Earth Engine. Therefore, the use of Google Earth Engine with integration of radar and optical data can be recommended to mapping pyroclastic deposits rapidly.

Satellite measurement of forest disturbance, recovery and deposit distribution following explosive volcanic eruptions

The characteristics and extent of forest damage, and the subsequent patterns of recovery, reflect the intensity of an explosive volcanic eruption and have the potential to be a novel proxy for eruption magnitude and impact. Using satellite measurements of vegetation damage and recovery patterns, following the 2015 explosive eruption of Calbuco, Chile, we assess the impact on surrounding temperate forests and how areas impacted by different deposit types recover post-eruption. The Calbuco eruption resulted in tephra deposition over hundreds of square kilometres, pyroclastic flows extending 6 km and lahars extending 15 km. We explore NDVI derived from optical imagery (June 2013–May 2023) as well as radar backscatter and phase coherence (October 2014–June 2023) through time series analysis, clustering and estimation of recovery timescales to find patterns in forest disturbance and recovery. We find that forest damage and recovery correspond primarily with deposit type, thickness and dispersal directions. The thickest tephra deposits (> 40 cm) correlate with the most vegetation loss, so our vegetation impact maps allow us to refine the spatial mapping of tephra fall-deposit isopachs to give a revised eruption volume of 0.28 km3. Vegetation recovery rates relate to initial impact type and intensity, but also local topography, aspect and altitude. Our results demonstrate a novel application of optical and radar satellite remote sensing to determine eruption extents and magnitudes through vegetation disturbance. We show that measuring vegetation disturbance, particularly in remote and densely vegetated environments, can help refine field-based analyses in inaccessible or intensely damaged zones.

New evidence of Holocene pyroclastic density currents at Galeras volcano, Colombia

The Galeras Volcanic Complex (GVC) is a composite volcano located between the Central and Western cordilleras in southern Colombia. It is considered one of the most active volcanoes in Colombia, with typically Vulcanian eruptions. The complex has been divided into different stages based on stratigraphic and geochronological differences. The most recent one is called the Galeras stage and is considered to have started ca. 4500 years. This study presents the results of new stratigraphic and geochronological analysis of the deposits that outcrop along the El Barranco river valley, NW of the GVC, which allowed us to identify newer and older deposits within the most recent stage (i.e., the Galeras stage). The deposits were analyzed via distribution, stratigraphy, geochronology, componentry and granulometry, as well as vesicularity and microtexture of the pumice fragments. We identified three previously unreported deposits, which results in a total of eight pyroclastic density current (PDC) deposits in the valley, which discordantly overlie andesitic lava flows of the previous stage (i.e., Genoy stage; 150–40 ka) of the GVC. They were named from Unit U1 to Unit U8, with units U1, U2 and U8 representing events not previously recorded in the eruptive history of Galeras volcano. Units U1 (8303 ± 97 and 8284.5 ± 90.5 cal BP), U2 (7667 ± 78 cal BP), U3 (5082 ± 198, 5096.5 ± 226.5, 5801.5 ± 481.5 and 5966 ± 235 cal BP) and U6 (2215.5 ± 101.5 and 2033 ± 91 cal BP) are interpreted as formed by PDCs generated by pumice-rich flows linked to the collapse of Subplinian eruptive columns, while units U5 (3201.5 ± 129 cal BP), U7 (1066.5 ± 109.5 and 944.5 ± 115.4 cal BP) and U8 (390.5 ± 80.5 cal BP) are interpreted as formed by PDCs generated by block and ash flows linked to the destruction of intracrater domes and the collapse of Vulcanian eruptive columns. U4 (4625 ± 181 cal BP) is associated with a “blast” type event, caused by the overpressure exerted by the gases of a viscous magma. The above mentioned record allows us to propose that the eruptive history of Galeras volcano began at the beginning of the Holocene (∼8300 years BP), and not 4500 BP, as previously established, which has hazard implications. Unit U8 in the town of La Florida as well as the nearby recorded deposits, indicates a probable PDC hazard for this population.

The subaqueous felsic volcanism from the Upper Member of the Cordón de Lila Complex, Antofagasta region, northern Chile

This contribution presents the study of an Ordovician subaqueous felsic succession, formed by the ~400 m-thick Upper Member of the Cordón de Lila Complex (CISL), northern Chile. From bottom to top, the succession starts with two dacitic sills that intruded into the sediments of the lowermost part of the Upper Member. Then, it is followed by a thick sedimentary deposit, two rhyolitic lavas, a volcanoclastic felsic breccia with pyroclastic clasts, and ends with a red rhyolitic lava. The first rhyolitic lava shows centimetric to metric folds with a north-northwestern vergence, evidence of flow in that direction. In the volcanoclastic breccia, an abundant pumice-and-fiamme-rich green matrix wraps around lithic clasts, giving the rock an eutaxitic texture at the outcrop scale. This matrix and texture evidence is characteristic of hot pyroclastic flows deposited under subaqueous conditions. The described section of the breccia is formed by four coarsening-up sequences, reflecting respectively four pulses of building up energy. The lack of internal erosional features points to a single and continuous explosive eruption. An accidental granite clast in the upper part of the breccia suggests a connection with a granitic body, possibly the Pingo-Pingo monzogranite. The geochemical character of the felsic succession is calc-alkaline. The tectonic setting diagram shows a within-plate setting for the succession. This suggests a shift from the arc position inferred for the Lower Member of the CISL to a forearc continental setting for the Upper Member of the CISL.

КАЛЬДЕРА КРАШЕНИННИКОВА (ВОСТОЧНАЯ КАМЧАТКА): ВОЗРАСТ И МАГНИТУДА ИЗВЕРЖЕНИЯ

New data on the composition of the pyroclastic deposits of the Krasheninnikov caldera allowed us to correlate it to the previously studied tephra horizon Geys30, which until recently was erroneously attributed to an eruption within the Geysernaya caldera. Pyroclastic flow deposits from the eruption that led to the formation of the Krasheninnikov caldera were found on the southern shore of Kronotsky Lake, and its distal tephra was found in the sediments of the Central Kamchatka Depression (CKD) at a distance of up to 200 km from the source (from Milkovo to Kliuchi villages). The age of this tephra was previously estimated at ~30 ka, which now allows us to accept this estimate for the Krasheninnikov caldera. The identification of the tephra of the caldera-forming eruption in distal sections allows a minimum estimate of the erupted pyroclastic volume of ~13 km3 and the eruption magnitude of 6.1.

Probabilistic, scenario-based hazard assessment for pyroclastic density currents at Tungurahua volcano, Ecuador

We assess the volcanic hazard posed by pyroclastic density currents (PDCs) at Tungurahua volcano, Ecuador, using a probabilistic approach based on the analysis of calibrated numerical simulations. We address the expected variability of explosive eruptions at Tungurahua volcano by adopting a scenario-based strategy, where we consider three cases: violent Strombolian to Vulcanian eruption (VEI 2), sub-Plinian eruption (VEI 3), and sub-Plinian to Plinian eruption (VEI 4–5). PDCs are modeled using the branching energy cone model and the branching box model, considering reproducible calibration procedures based on the geological record of Tungurahua volcano. The use of different calibration procedures and reference PDC deposits allows us to define uncertainty ranges for the inundation probability of each scenario. Numerical results indicate that PDCs at Tungurahua volcano propagate preferentially toward W and NW, where a series of catchment ravines can be recognized. Two additional valleys of channelization are observed in the N and NE flanks of the volcano, which may affect the city of Baños. The mean inundation probability calculated for Baños is small (6 ± 3%) for PDCs similar to those emplaced during recent VEI 2 eruptions (July 2006, February 2008, May 2010, July 2013, February 2014, and February 2016), and on the order of 13 ± 4% for a PDC similar to that produced during the sub-Plinian phase of the August 2006 eruption (VEI 3). The highest intensity scenario (VEI 4–5), for which we present and implement a novel calibration procedure based on a few control points, produces inundation areas that nearly always include inhabited centers such as Baños, Puela, and Cotaló, among others. This calibration method is well suited for eruptive scenarios that lack detailed field information, and could be replicated for poorly known active volcanoes around the world.

Pre-Choiyoi volcanism at Cordillera del Viento, southwestern margin of Gondwana (∼37° S): Geological characterisation, geochronology and regional implications

This contribution provides a comprehensive description and classification of fifteen lithofacies within the Carboniferous rocks attributed to the Arroyo del Torreón Formation and Sofía Dacite in order to understand the eruptive dynamics and the evolution of volcanism associated with the onset of the Gondwanan Orogenic Cycle at the Cordillera del Viento (Argentina). The outcrops of Carboniferous volcanic and volcaniclastic rocks linked to this cycle are restricted to the Cordilllera del Viento range. In consequence, they offer a valuable opportunity to research the volcanic arc products of the pre-Choiyoi magmatism.The Arroyo del Torreón Formation lithofacies interpretation and its distribution indicate that the volcanism commenced with local andesitic lava flows followed by a volcano-sedimentary sequence formed by multiple pumice-rich quasi-steady concentrated pyroclastic density currents alternating with episodes of epiclastic sedimentation. The latter are covered ignimbrites developed by boiling over eruptions. Crystal-rich tuffs overlie the ignimbrites and represent a transition to a plinian eruption. This eruption style continued, developing concentrated pyroclastic density currents with highly unsteadiness conditions and scarce fall-out deposits. Conversely, the Sofía Dacite, represent a notable shift in the volcanism style, characterized by dacitic to rhyolitic lava flows with minor pyroclastic beds. Zircon dating of a pumice-rich lapilli-tuff from the Arroyo del Torreón Formation yielded a minimum age of 327.77 ± 1.79 Ma that was interpreted as the maximum depositional age for this unit. Similarly, zircons from a porphyritic dacite representing the Sofía Dacite provided a Concordia age of 329.11 ± 1.31 Ma that was interpreted as the crystallisation age of this rock.Consequently, we propose a new stratigraphic division of the Arroyo del Torreón Formation into two members. The Cerro San Pedro Member will comprise the pyroclastic rocks at the base of the sequence, while the Sofía Member will include the upper lava-dominated portion of the unit. In this sense, the whole lithostratigraphic unit represents a distinctive Carboniferous basin associated with arc-related volcanism representative from the pre-Choiyoi magmatism.

VOLCANBOX: A software platform for volcanic hazard assessment

Volcanic eruptions have an intrinsic multi-hazard nature, in which a variety of volcanic products (lava flows, fallout, lahars, and pyroclastic flows) and associated hazards (seismic shocks, landslides, tsunamis, or floods) may interact and impact sequentially. Volcanic hazard assessment relies on probabilistic approaches based on the past eruptive history, from which scientists identify eruptive scenarios and their expected recurrence. However, not enough attempts have yet been made to address volcanic hazard assessment in a systematic way, based on principles that may be equally applicable to different volcanoes and volcanic zones regardless of their particular nature. Hence, we present VOLCANBOX, a new multiplatform (GNU/Linux, MacOS, Windows) system designed to conduct long-and short-term volcanic hazard assessment and risk analysis in a systematic and rational manner, aimed at reducing volcanic risk by anticipating future eruptions. VOLCANBOX includes several sets of software tools designed to evaluate long and short-term volcanic hazards, to conduct vulnerability analysis, and to assist decision-makers during the management of a volcanic crisis. VOLCANBOX can be implemented before an emergency, in order to identify optimum mitigating actions and how these may have to be adapted as new information is obtained. VOLCANBOX is aimed at experts in volcanic hazard and risk assessment and management and is designed to facilitate the interaction and cooperation between scientists, policy makers and civil protection agencies to anticipate volcanic disasters in a timely manner, by quantifying volcanic hazards, understanding volcanic unrest, forecasting volcanic eruptions, and identifying the most probable scenarios in a simple and clear manner.

Robust prediction models for flow and compressive strength of sustainable cement grouts for grouted macadam pavement using RSM

This study investigates the utilization of pumice stone ash in cementitious grouts for grouted macadam pavement, aiming to enhance flowability and compressive strength. Partial replacement of ordinary Portland cement (OPC) with varying percentages (5–20 %) of powdered pumice stone (PPS) ash was explored, alongside adjustments in water-to-cement (w/c) ratios. Experimental assessments, including flowability tests and compressive strength evaluations, were conducted on fresh and hardened grouts. Response surface methodology (RSM) and ANOVA analysis were employed to analyze the relationship between pumice stone ash content, w/c ratio, flow, and compressive strength. The results show that increasing the PPS content from 0 % to 20 % led to an increase in flow time from 23.6 to 34 seconds at a 0.3 w/c ratio, from 9 to 19 seconds at a 0.35 w/c ratio, and from 7 to 14 seconds at a 0.40 w/c ratio: indicating reduced flowability of the grouts. The 7-day compressive strength increased by approximately 2–17 % when 5–15 % of the cement was replaced with PPS, but a reduction occurred at 20 % PPS. Similarly, the 28-day compressive strength increased by about 4–23 % with 5–15 % PPS, while 20 % PPS led to a decrease in strength. The results highlight specific combinations of pumice stone ash content and w/c ratios, particularly 10 % PPS at 0.35 w/c and 15 % PPS at both 0.35 and 0.40 w/c, that meet grouted macadam standards, balancing flowability and strength. Fit statistics demonstrate the reliability of the predictive model. Optimization aims to maximize pumice stone ash content and w/c ratio, with graphical representation indicating an optimal composition at 17.25 % PPS and 0.35 w/c ratio for efficient grouted macadam construction. Additionally, Significant contribution towards sustainability can be achieved by replacing cement with pumice stone ash in pavement construction.

OpenFOAM-avalanche 2312: depth-integrated models beyond dense-flow avalanches

Abstract. Numerical simulations have become an important tool for the estimation and mitigation of gravitational mass flows, such as avalanches, landslides, pyroclastic flows, and turbidity currents. Depth integration stands as a pivotal concept in rendering numerical models applicable to real-world scenarios, as it provides the required efficiency and a streamlined workflow for geographic information systems. In recent years, a large number of flow models were developed following the idea of depth integration, thereby enlarging the applicability and reliability of this family of process models substantially. It has been previously shown that the finite area method of OpenFOAM® can be utilized to express and solve the basic depth-integrated models representing incompressible dense flows. In this article, previous work (Rauter et al., 2018) is extended beyond the dense-flow regime to account for suspended particle flows, such as turbidity currents and powder snow avalanches. A novel coupling mechanism is introduced to enhance the simulation capabilities for mixed-snow avalanches. Further, we will give an updated description of the revised computational framework, its integration into OpenFOAM, and interfaces to geographic information systems. This work aims to provide practitioners and scientists with an open-source tool that facilitates transparency and reproducibility and that can be easily applied to real-world scenarios. The tool can be used as a baseline for further developments and in particular allows for modular integration of customized process models.

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

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.

A Preliminary Hazard Assessment of Kolumbo Volcano (Santorini, Greece)

Volcanic eruptions stand as destructive threats to adjacent communities, unleashing multiple hazards such as earthquakes, tsunamis, pyroclastic flows, and toxic gases. The imperative for proactive management of volcanic risks and communities’ adaptation cannot be overstated, particularly in densely populated areas where the potential for widespread devastation looms large. Kolumbo, an active submarine volcano located approximately 7 km northeast of Santorini Island in Greece, serves as a pertinent case. Its historical record is characterised by an eruption in 1650 CE that produced a catastrophic tsunami. The aftermath witnessed havoc on neighbouring islands, coupled with casualties stemming from noxious gases in Santorini. Eyewitness accounts mention maximum water run-up heights of 20 m on the southern coast of Ios, inundation of an area of 240 m inland on Sikinos, and a flooding of up to 2 km2 inland on the eastern coast of Santorini. Recent studies suggest that a potential future eruption of Kolumbo poses a substantial hazard to the northern and eastern coasts of Santorini. Unfortunately, the absence of a concrete management protocol leaves these areas vulnerable to an impending threat that demands immediate attention. Therefore, it is recommended that a comprehensive approach be adopted, involving scientific research (active monitoring, hazard maps), community engagement, preparedness planning with government agencies, and the development of timely response strategies to reduce the associated risks, prevent casualties, and mitigate the potential consequences on the region’s economy and infrastructure.

Syn and post-glacial volcanic activity in the western retroarc area of the andean southern volcanic zone: Overo volcano

Located in a poorly studied zone of the rear arc in the Transitional Southern Volcanic Zone, the Overo volcano presents a complete record of syn-glacial, inter-glacial, and post-glacial activity, marked by significant changes in eruptive mechanisms over time. Following pre-glacial units, an effusive syn-glacial basaltic phase was succeeded by an extensive inter-glacial diking that fed andesitic monogenetic fields. Subsequently, an eruptive pulse, possibly coupled with the destabilization of the main edifice, resulted in a block and ash deposit channeled into a glacial valley towards the southwest, later covered by extensive basaltic lava flows. Then, different types of pyroclastic flows and glacial deposits covered these earlier units. Finally, these younger glacial deposits were overlain by a localized postglacial pyroclastic deposit and widespread lava flows, which ultimately reconstructed the deeply eroded glacial morphology of the Overo volcano. This volcanic record reveals the young and complex activity of this poorly known western rear-arc volcanic center in the Transitional Southern Volcanic Zone of the Andes, whose evolution is more akin to the arc front volcanoes to the west than to their eastern within-plate counterparts. We propose that this magmatic evolution was influenced by the Pleistocene-Holocene Last Glacial Maximum activity (LGM), beginning with an initial phase of volcanic activity encapsulated within glacial conditions. Glacial retreat then triggered isostatic uplift and crustal relaxation, resulting in dike formation, flank instability, and syn-eruptive collapse of the volcanic edifice. Subsequently, a lesser glacial pulse partially eroded the volcano morphology and produced the currently preserved glacial deposits. Finally, a latest and limited post-glacial pyroclastic eruption occurred simultaneously with the formation of an extensive monogenetic basaltic field, shaping the final morphology of the volcano.

Co-melting mechanisms for municipal solid waste incineration fly ash with fine slag from coal gasification and coal gangue

Vitrification is a promising treatment for municipal solid waste incineration fly ash (MSWI-FA); however, high energy consumption due to the high MSWI-FA fusion temperature limits the development and application of this technique. In this study, fine slag ash (FSA) derived from coal gasification and coal gangue ash (CGA) were mixed with MSWI-FA to reduce the ash fusion temperature. The transformation of minerals in ash during thermal treatment was examined via X-ray diffraction and thermodynamic equilibrium calculations. The ash flow behaviour was observed using a thermal platform microscope, and the silicate structure was quantified using Raman spectra. The co-melting mechanisms for the mixed ash were systematically investigated. Results indicate that the flow temperature (FT) of the mixed ash exhibited an initial decrease and subsequent increase as a function of the addition ratio of FSA or CGA. Lowest ash FT of 1215 °C and 1223 °C were recorded for addition of 50% FSA and 50% CGA, respectively; further, these temperatures were lowered by > 285 °C and >277 °C respectively, relative to FT of the MSWI-FA. The transformation of minerals and silicate structure during mixed ash heating was responsible for the variation in the ash fusion temperature. CaO in MSWI-FA tended to react with mullite, quartz and haematite in FSA and CGA, forming minerals such as anorthite, gehlenite, and andradite with relatively low melting points. The addition of FSA or CGA caused changes in the silicate network structure of the mixed ash. In particular, 50% FSA incorporation caused the transformation of Q4 and Q3 to Q2, whereas 50% CGA introduction resulted in the conversion of Q4 and Q2 into Q3 and Q1 + Q0, respectively. The silicate network depolymerised, causing reduction in the ash fusion temperature and increasing the melting rate.

Andesite magma genesis, conduit dynamics and variable decompression from shallow reservoirs drive contrasting PDC events at Volcán de Colima, Mexico

Volcán de Colima, one of the Earth's most active and hazardous andesitic stratovolcanoes, experienced its last major explosive eruption on July 2015 with two distinct events. The July-10 event comprised the collapse of a large summit dome, forming block-and-ash flow deposits of dense dome lava clasts. The July-11 event produced pyroclastic density currents (PDCs) that flowed to maximum 10.5 km-distance from the crater, burned the vegetation, and formed valley and overbank deposits of up to 30 vol% vesicular scoria clasts. Whereas the July-10 event fits well within the last 20 years' typical activity of Volcán de Colima, the July-11 PDCs were unprecedented. We present a close examination of the July-11 deposits via combined field, microtextural, and chemical analyses, including electron microscopy and X-ray microtomography. Results show that andesite magma (58–59 wt% SiO2) at 1021 °C and having 2 wt% H2O degassed and crystallized (102–105 mm−3 vesicles and 102–103 mm−3 microlite number densities) while ascending to the surface from ∼2 km-depth reservoirs, driven by decompression rates of 0.4–1.7 MPa s−1. These variable rates reflected heterogenous andesite magma rheology produced by different stages of melt genesis, mobility, stalling, crystallization and vesiculation. Prior to experiencing fragmentation, the andesite magma mingled with rhyolite melts produced from partial melting of silicic mush stored at depths from ∼2 to 5 km. Magmas fragmented at maximum strain rates of 10−3 s−1, powering the July-11 energetic (106–107 kg s−1) and pulsating PDCs that released 102–103 m3 s−1 on surface. The rapid <20 h transition from the July-10 to the July-11 events suggests only hours timescales from dome collapse to magma decompression and explosive eruption.