Pyroclastic Flows Research Articles

Numerical Modeling of the Ash Cloud Movement from the Catastrophic Eruption of the Sheveluch Volcano in November 1964

This paper reconstructs, for the first time, the motion dynamics of an eruptive cloud formed during the catastrophic eruption of the Sheveluch volcano in November 1964 (Volcanic Explosivity Index 4+). This became possible due to the public availability of atmospheric reanalysis data from the ERA-40 archive of the European Center for Medium-Range Weather Forecasts (ECMWF) and the development of numerical modeling of volcanic ash cloud propagation. The simulation of the eruptive cloud motion process, which was carried out using the FALL3D and PUFF models, made it possible to clarify the sequence of events of this eruption (destruction of extrusive domes in the crater and the formation of an eruptive column and pyroclastic flows), which lasted only 1 h 12 min. During the eruption, the ash cloud consisted of two parts: the main eruptive cloud that rose up to 15,000 m above sea level (a.s.l.), and the co-ignimbrite cloud that formed above the moving pyroclastic flows. The ashfall in Ust-Kamchatsk (Kamchatka) first occurred out of the eruptive cloud moving at a higher speed, then out of the co-ignimbrite cloud. In Nikolskoye (Bering Island, Commander Islands), ash fell only out of the co-ignimbrite cloud. Under the turbulent diffusion, the forefront of the main eruptive cloud rose slowly in the atmosphere and reached 16,500 m a.s.l. by 04:07 UTC on November 12. Three days after the eruption began, the eruptive cloud stretched for 3000 km over the territories of the countries of Russia, Canada, the USA, Mexico, and over both the Bering Sea and the Pacific Ocean. It is assumed that the well-known long-term decrease in the solar radiation intensity in the northern latitudes from 1963–1966, which was established according to the world remote sensing data, was associated with the spread of aerosol clouds formed not only by the Agung volcano, but those formed during the 1964 Sheveluch volcano catastrophic eruption.

Applicability of numerical two-layer depth-averaged models for pyroclastic density currents to powder snow avalanches: Toward developing a unified model for powder snow avalanches and pyroclastic density currents

Applicability of numerical two-layer depth-averaged models for pyroclastic density currents to powder snow avalanches: Toward developing a unified model for powder snow avalanches and pyroclastic density currents

Exploring pyroclastic density currents with analogue models

Exploring pyroclastic density currents with analogue models

Subaerial volcaniclastic deposits – influences of initiation mechanisms and transport behaviour on characteristics and distributions

Abstract Subaerial volcaniclastic deposits are produced principally by volcanic debris avalanches, pyroclastic density currents, lahars, and tephra falls. Those deposits have widely ranging geomorphic and sedimentologic characteristics; they can mantle, modify, or create new topography, and their emplacement and subsequent reworking can have an outsized impact on the geomorphic and sedimentologic responses of watersheds surrounding, and channels draining, volcanoes. Volcaniclastic deposits provide a wealth of information about eruptive histories, volcanic processes, and landscape responses to eruptions. The volcanic processes that produce these deposits, and consequently the character and sedimentary structures of the deposits themselves, are influenced by initiation mechanism. Deposit preservation is affected by deposit magnitude, texture, and composition, depositional environment, and climate regime. Innovative analyses of deposits from several modern eruptions and advancements in physical and numerical modelling have vastly improved our understanding of volcanic processes, interpretations of eruptive histories, and recognition of the hazards posed by volcanic eruptions. This contribution highlights and summarizes major advances that have occurred in the past few decades in understanding of volcaniclastic deposits and linkages with volcanic processes.

Long-runout pyroclastic density currents: Analysis and implications

Abstract Pyroclastic density currents are hazardous, ground-hugging, hot mixtures of gas and solid particles produced by volcanoes. Currents generated by the largest explosive eruptions have traveled distances on the order of 100 km, and their devastating impact has repeatedly marked Earth's geologic history. We show that pyroclastic density currents from super-eruptions during the Oligocene in the Great Basin of the United States had exceptional runout distances that may have exceeded 300 km. We present a quantitative analysis of the data from these currents and consider, in particular, the areal extent of their deposits (ignimbrites) as well as the relationship between their runout and the eruption mass discharge rate. The ignimbrites have elliptical distributions characterized by axis length ratios of ~2–6, in contrast to common subcircular ignimbrites, while the maximum runouts versus the discharge rates are clearly outside of the prediction intervals defined by other eruption data. We argue that the long runouts resulted from the channeling of concentrated currents in regional paleovalleys whose gentle slope worked to lengthen the travel distance. Our study demonstrates that these additional factors should be considered in assessing hazards posed by future super-eruptions.

Investigation on the regulation mechanism of Fe2O3 / SiO2 on ash melting and flow behavior under gasification conditions

ABSTRACT Stable flow and discharge of the slag in an entrained flow gasifier are the key factors to ensure the long-term stable operation of gasifier. In this work, the melting and flow behavior of coal ash with different Fe2O3/SiO2 ratios was studied in a reduced atmosphere. The results show that the viscosity of slag decreases significantly with the increase of Fe2O3/SiO2. And the critical viscosity-temperature (TCV) decreases from 1309°C to 1226°C. It is found that more than 90% of iron ions exist in the form of Fe2+ in liquid slag by chemical titration. There are more simple ion clusters with low bridge oxygen number (BO) with the increase of Fe2+ and lead to depolymerization of slag. Furthermore, the ash with high SiO2 content can be transformed into slag with high viscosity at a low melting rate by the analysis of the slag area curve and X-ray diffraction pattern, which is considered to be controlled by the “softening-melting” mechanism. The ash with high Fe2O3/SiO2 can be transformed rapidly into a low viscosity liquid at a short melting interval, which follows the “melting-dissolution” mechanism. And it is helpful to promote the formation of low-temperature eutectics with the increase in Fe2O3/SiO2 by thermodynamic calculation. Research on the melting mechanism of slag will provide theoretical support for the regulation of slag flow characteristics.

Detecting multiscale periodicity from the secular effusive activity at Santiaguito lava dome complex (Guatemala)

Santiaguito, Guatemala, represents one of the best cases of active lava dome complex in the world, producing lava flow effusion, weak explosive activity, and cycles of lava dome extrusion over varying timescales. Since the inception in 1922, it has shown a remarkable constant eruptive activity, characterized by effusion of blocky domes and lava flows punctuated by moderate explosions of gas-and-ash and pyroclastic flows. In this study, we reconstruct the time evolution of discharge rates of Santiaguito across one entire century, from 1922 to 2021, combining, for the more recent activity, new satellite thermal data. By using discrete Fourier transform (DFT) and Morlet wavelet analyses, we identify three fundamental periodicities in subsets of the 1922–2021 time-series: (i) long term (ca. 10 years), (ii) intermediate term (ca. 3.5 years), and (iii) short term (from ca. 1 year to ca. 3 months), which are comparable with those observed at other lava dome eruptions at calc-alkaline volcanoes. Such inferred periodicities provide a powerful tool for the interpretation of the non-linear eruptive behaviour and represent a pivotal benchmark for numerical modelling aimed to reconstruct the dynamics of the magma feeding system based on a time-averaged discharge rate dataset.Graphical

Advanced characterization of hydrothermal flows within recharge and discharge areas using rare earth elements, proved through a case study of two-phase reservoir geothermal field, in Southern Bandung, West Java, Indonesia

Rare earth element (REE) analysis is effective for tracing water–rock interactions and solute transport in geothermal and groundwater systems. This study aimed to clarify hydrothermal flows within recharge and discharge areas of a geothermal system. We selected a well-known high-temperature geothermal field with two-phase reservoir in Southern Bandung, West Java (Indonesia) as a case study target, and collected 31 river/spring samples and 8 well rock samples. The measured total REE series concentrations ranged widely in the water samples, i.e., rivers: 3.4–35 ppt, cold springs: 0.3–284 ppt, and hot springs: 1.4 ppt to 102 ppm. Enrichment of light REEs (LREEs) in the water samples was characterized more clearly by Post Archean Australian Shale normalization than by chondrite normalization. Speciation analysis derived the following interpretations: dissolved REEs in the river water originated from free ions or Ln3+ that are typically contained in near-surface groundwater, and the dominant components were carbonate (LnCO3+) and Ln3+ complexes in the cold springs and LnCO3+ complexation in the hot springs. Steam and gas condensation into less-oxygenated groundwater can be indicated by rich LnCO3+. Only one hot spring was interpreted as being directly connected with the reservoir by strong H2S condensation and LREE enrichment. The water of the other cold and hot springs probably underwent dilution, evaporation, and magmatic gas condensation through shallow, deep, and deep-perched aquifers, permeable zones, and a major fault within the recharge and discharge areas. REE results also suggest that the main constituents of the aquifers are carbonates and silicate minerals and hydrothermally altered lahars, andesitic lava, and pyroclastic flow deposits. REEs facilitate detailed interpretation of geochemistry facies in shallow–deep waters of a hydrothermal system. Finally, integration of the analysis results of REEs, major anions and cations, water isotopes, and strontium isotopes improved a conceptual model of groundwater flows and recharge–discharge interactions in aquifers feeding a geothermal reservoir.

Climate Change Impacts on Stream Water Temperatures in a Snowy Cold Region According to Geological Conditions

This study clarifies how climate change affects stream temperatures in snowy cold regions, where groundwater impacts vary with geological conditions. We developed a physics-based water circulation model that incorporates an atmospheric and land surface process model considering snow processes, a runoff model, and a water temperature estimation model. Small watersheds in the mountainous area of Hokkaido formed the study area, and the runoff model was assigned different parameters depending on the geological characteristics. Using these parameters, changes in water temperature were calculated with respect to changes in the meteorological data in historical and future simulations. Current water temperatures were effectively reproduced by the model, and following the IPCC RCP 8.5 scenario, future water temperatures in the distribution area for new pyroclastic flows were predicted to remain lower in summer than in the distribution area of older formations. The findings of this study will be useful in informing conservation measures for river ecosystems, including the prioritization of streams where cold-water fish need to be conserved.

Seismic Microzonation of the Pompeii Archaeological Park (Southern Italy): Local Seismic Amplification Factors

Pompeii Archaeological Park is the best laboratory for the study of the seismic site effects on cultural heritage: the ancient site was destroyed and buried by the 79 AD Vesuvian eruption and, furthermore, it was also affected by the 62–63 AD strong earthquake. Large sectors of the city were reconstructed after this earthquake while other parts were still under reconstruction when the fall-out and pyroclastic density currents of the eruption buried the Roman city. In order to evaluate the distribution of the damage and reconstructions due to the earthquake, detailed mappings of the structures were carried out using multidisciplinary approaches. In addition, analyses of the topographical features, subsoil stratigraphies, and geophysical surveys, responsible for local seismic amplification (site effects), allow us to define the sectors of the ancient city where the Amplification Factors (AFs) were the main ones responsible for damage. Selected areas and examples of compromised and reconstructed buildings show that the ancient topography and subsoil features (both lithological and seismic) are the main AFs. In particular, the damages caused by the 62–63 AD earthquakes seem to be mainly due to topographical factors such as steep scarps and slopes, ridges, peaks, and terraces, as well as to the major thickness of the soft sediments (loose volcanoclastic layers, paleosols, weathered lavas, and anthropogenic infillings) located over the well-lithified lavas. It is not uncommon to also have the combination of these two factors. For the first time, this multidisciplinary approach allows us to draw a seismic microzonation map for one of the most important archaeological sites of the world.

Depositional Processes of Pyroclastic Density Currents in Lacustrine Environments: An Example from the Cretaceous Jeonggaksan Formation in Danjang-myeon, Miryang City

Depositional Processes of Pyroclastic Density Currents in Lacustrine Environments: An Example from the Cretaceous Jeonggaksan Formation in Danjang-myeon, Miryang City

The Petrology and Volcano-Stratigraphy of The Muria-Peninsula High-K Volcanic Rocks, Central Java, Indonesia

The Muria-Peninsula is a Quaternary volcano located in the northern Sunda arc. Its activity was controlled under high potassic and very high potassic magma series resulting in leucite-rich trachyte and pyroxene-rich basaltic-andesite. It is a strato-type volcano that is composed of lava, breccia, and tuff layers, and some dikes have some volcanic craters and maars varying in age and composition. The study area is covering the volcanoes of Muria, Genuk, and Patiayam. This paper aims to describe the petrology, mineralogy, and volcano-stratigraphy of the different volcanic materials. The data and materials were sourced from the primary and secondary data. The methods are field mapping, stratigraphy measurements, collecting samples, thin section analyses, and major element geochemistry using X-Ray fluorescence (XRF). The results describe two groups of volcanic rocks consisting of pyroxene-rich andesitic-basaltic volcanic materials and leucite-rich trachytic volcanic materials. Augite presents in the andesitic basalt together with small grains of olivine and a few anorthite and foid minerals. Aegirine (Na-Pyroxene) is present in the leucite-rich trachyte that is often associated with biotite and hornblende. Na-Ca Plagioclase such as labradorite-andesine is often present in the basaltic-trachy-andesite that is usually rarely leucite. The major elements show high-K volcanic rocks with % K2O is 4-5.9% and very high-K volcanic rocks (with % K2O is between 6-8.24%) and low-K volcanic rocks that contain % K2O is 2-3,9%. There are two groups of high-K to very high-K volcanic materials consisting of silicic-rich volcanic materials (~57-64% of SiO2) and low-silicic volcanic materials (~46-50%). The TAS diagram identifies tephrite, phonolite, and trachyte. Stratigraphic data identifies calcareous sediments of the Bulu Formation as the basement rocks of the Muria trachyandesite. Beds of pumice-rich volcanic breccia of the Ujungwatu Formation are the basement rocks of the basanite-tephrite of the Genuk Volcano, and the tuff of the Ujungwatu is also exposed consisting of the basanite-tephritic-phonolite of the Patiayam Volcano. The leucite-like feldspars are very common in the andesite lava and dikes that compose the crater of Muria. Most of the Muria volcanic materials are rarely in leucite, while some maars contain pumice-rich pyroclastic flows and basaltic lava. The results of the major elemental analysis of the Muria materials indicate that the rock tends to be of medium to high K affinity (~2% K2O). The Genuk and older Muria are consisting of leucite-rich tephrite-phonolite. It was two periods of magmatic series developed in the Muria-Peninsula that was resulting in the high-K to very high-K magmatism and the medium K Kalk-alkaline magmatism.

Physical and morphological characterization of the 19 May 2021 ash cloud deposit at Stromboli (Italy)

We report on the ash cloud related to the gravitational collapse of a portion of the Stromboli volcano crater rim that occurred on 19 May 2021. The collapse produced a pyroclastic density current (PDC) that spread along the northwest flank of the volcano and propagated in the sea for about 1 km. The PDC was associated with a convective ash cloud that rapidly dispersed eastward and deposited a thin layer (< 1 mm) of very fine pinkish ash over the village of Stromboli. The deposit was sampled shortly after the emplacement (within a few hours) and prior to any significant reworking or re-sedimentation. We present a comprehensive description of the deposit including dispersal, sedimentological characteristics and textural and geochemical features. We also compare the 19 May 2021 deposit with fine-ash deposits connected to other PDCs and landslides previously occurring at Stromboli and with the distal ash of a paroxysmal explosive eruption of Mt. Etna volcano. Results indicate that the distributions of the mass on the ground and of the grain size are not correlated with the distance from the source. Also, the componentry reflects a preponderance of remobilized material ingested by the PDC. Therefore, the great amount of fine ash can be ascribed to clasts comminution processes, although the prevalence of dense crystalline components records an overall equiaxial shape, revealing a paucity of elongated clast with complex morphology. Furthermore, the outcomes of this work aim to create a collection of data of a co-PDC ash cloud that may prove useful for comparison with other deposits worldwide.

Influence of the topography of stratovolcanoes on the propagation and channelization of dense pyroclastic density currents analyzed through numerical simulations

We applied systematically the branching energy cone model to a large ( $$N=50$$ ) set of stratovolcanoes around the world in order to evaluate the main topographic characteristics that may control the propagation of dense pyroclastic density currents (PDCs). Results indicate that the channelization efficiency of a PDC is strongly controlled by the relative scale between flow size and volcano topographic features. Most of the studied stratovolcanoes topographies are able to induce significant PDC channelization in proximal domains, while strong channelization in distal zones is mainly observed for volcanoes with steep flanks, with long, uninterrupted valleys, and with catchments zones of pyroclastic material (i.e. the valleys heads) located near the source. From the statistical analysis of numerical results, we recognise five groups of stratovolcanoes in terms of the mode of interaction between their topographies and dense PDCs: (1) intense channelization through different valleys up to distal domains (e.g. Colima and Peteroa); (2) intense channelization through a single, dominant valley up to distal domains (e.g. Reventador and Mt. St. Helens); (3) intense channelization near the source and moderate distal channelization, frequently involving intertwined drainage networks (e.g. Tungurahua and El Misti); (4) potentially intense channelization only near the source, typically involving flat distal topographies (e.g. Sinabung and Mayon); and (5) weak channelization in proximal domains, resulting in efficient early energy dissipation and thus reduced PDC run-out distance (e.g. Kelut and Akagi). The relevance of this classification lies in the possibility of defining volcanic analogues (defined here as volcanoes that share a suite of topographic characteristics and may be considered comparable to a certain extent) and identifying the main processes that may affect PDC propagation in specific topographic contexts. These aspects are useful for studying poorly documented volcanic edifices and for volcanic hazard assessment. Additionally, we compare this classification with published morphometric characteristics of volcanoes, showing morphometric parameters such as the mean slope of the low flank, irregularity index, ratio of volcano height and basal width and ratio of crater width and basal width are useful variables for recognising the groups we defined. These parameters can be used as rough indicators of the expected interaction patterns between the topography of a given volcano and dense PDCs.

Global Tonga tsunami explained by a fast-moving atmospheric source

Volcanoes can produce tsunamis by means of earthquakes, caldera and flank collapses, pyroclastic flows or underwater explosions1–4. These mechanisms rarely displace enough water to trigger transoceanic tsunamis. Violent volcanic explosions, however, can cause global tsunamis1,5 by triggering acoustic-gravity waves6–8 that excite the atmosphere–ocean interface. The colossal eruption of the Hunga Tonga–Hunga Ha’apai volcano and ensuing tsunami is the first global volcano-triggered tsunami recorded by modern, worldwide dense instrumentation, thus providing a unique opportunity to investigate the role of air–water-coupling processes in tsunami generation and propagation. Here we use sea-level, atmospheric and satellite data from across the globe, along with numerical and analytical models, to demonstrate that this tsunami was driven by a constantly moving source in which the acoustic-gravity waves radiating from the eruption excite the ocean and transfer energy into it by means of resonance. A direct correlation between the tsunami and the acoustic-gravity waves’ arrival times confirms that these phenomena are closely linked. Our models also show that the unusually fast travel times and long duration of the tsunami, as well as its global reach, are consistent with an air–water-coupled source. This coupling mechanism has clear hazard implications, as it leads to higher waves along land masses that rise abruptly from long stretches of deep ocean waters.

Large-magnitude (VEI ≥ 7) ‘wet’ explosive silicic eruption preserved a Lower Miocene habitat at the Ipolytarnóc Fossil Site, North Hungary

During Earth’s history, geosphere-biosphere interactions were often determined by momentary, catastrophic changes such as large explosive volcanic eruptions. The Miocene ignimbrite flare-up in the Pannonian Basin, which is located along a complex convergent plate boundary between Europe and Africa, provides a superb example of this interaction. In North Hungary, the famous Ipolytarnóc Fossil Site, often referred to as “ancient Pompeii”, records a snapshot of rich Early Miocene life buried under thick ignimbrite cover. Here, we use a multi-technique approach to constrain the successive phases of a catastrophic silicic eruption (VEI ≥ 7) dated at 17.2 Ma. An event-scale reconstruction shows that the initial PDC phase was phreatomagmatic, affecting ≥ 1500 km2 and causing the destruction of an interfingering terrestrial–intertidal environment at Ipolytarnóc. This was followed by pumice fall, and finally the emplacement of up to 40 m-thick ignimbrite that completely buried the site. However, unlike the seemingly similar AD 79 Vesuvius eruption that buried Pompeii by hot pyroclastic density currents, the presence of fallen but uncharred tree trunks, branches, and intact leaves in the basal pyroclastic deposits at Ipolytarnóc as well as rock paleomagnetic properties indicate a low-temperature pyroclastic event, that superbly preserved the coastal habitat, including unique fossil tracks.

Damage assessment for the 2018 lower East Rift Zone lava flows of Kīlauea volcano, Hawaiʻi

Cataloguing damage and its correlation with hazard intensity is one of the key components needed to robustly assess future risk and plan for mitigation as it provides important empirical data. Damage assessments following volcanic eruptions have been conducted for buildings and other structures following hazards such as tephra fall, pyroclastic density currents, and lahars. However, there are relatively limited quantitative descriptions of the damage caused by lava flows, despite the number of communities that have been devastated by lava flows in recent decades (e.g., Cumbre Vieja, La Palma, 2021; Nyiragongo, Democratic Republic of Congo, 2002 and 2021; Fogo, Cape Verde, 2014–2015). The 2018 lower East Rift Zone (LERZ) lava flows of Kīlauea volcano, Hawaiʻi, inundated 32.4 km2 of land in the Puna District, including residential properties, infrastructure, and farmland. During and after the eruption, US Geological Survey scientists and collaborators took over 8000 aerial and ground photographs and videos of the eruption processes, deposits, and impacts. This reconnaissance created one of the largest available impact datasets documenting an effusive eruption and provided a unique opportunity to conduct a comprehensive damage assessment. Drawing on this georeferenced dataset, satellite imagery, and 2019 ground-based damage surveys, we assessed the pre-event typology and post-event condition of structures within and adjacent to the area inundated by lava flows during the 2018 LERZ eruption. We created a database of damage: each structure was assigned a newly developed damage state and data quality category value. We assessed 3165 structures within the Puna District and classified 1839 structures (58%) as destroyed, 90 structures (3%) as damaged, and 1236 (39%) as unaffected. We observed a range of damage states, affected by the structural typology and hazard characteristics. Our study reveals that structures may be damaged or destroyed beyond the lava flow margin, due to thermal effects from the lava flow, fire spread, or from exposure to a range of hazards associated with fissure eruptions, such as steam, volcanic gases, or tephra fall. This study provides a major contribution to the currently limited evidence base required to forecast future lava flow impacts and assess risk.

Deposit‐Derived Block‐and‐Ash Flows: The Hazard Posed by Perched Temporary Tephra Accumulations on Volcanoes; 2018 Fuego Disaster, Guatemala

AbstractThe impact of hazardous pyroclastic density currents (PDCs) increases with runout distance, which is strongly influenced by the mass flux. This article shows that the mass flux of a PDC may derive not only from vent discharge during the eruption, but also from partly hot, temporary stores (accumulations) of aerated pyroclastic material perched high on the volcano. The unforeseen PDC at Fuego volcano (Guatemala) on 3 June 2018 happened c.1.5 hr after the eruption climax. It overran the village of San Miguel Los Lotes causing an estimated 400+ fatalities. Analysis of the facies architecture of the deposit combined with video footage shows that a pulsatory block‐and‐ash flow flowed down the Las Lajas valley and rapidly waxed, the runout briefly increasing to 12.2 km as it filled and then spilled out of river channels, entered a second valley where it devastated the village and became increasingly erosive, prior to waning. Paleomagnetic analysis shows that the PDC contained only 6% very hot (&gt;590°C) clasts, 39% moderately hot (∼200°C–500°C) clasts, and 51% cool (&lt;200°C) clasts. This reveals that the block‐and‐ash flow mostly derived from collapse of loose and partly hot pyroclastic deposits, stored high on the volcano, gradually accumulated during the last 2–3 years. Progressive collapse of unstable deposits supplied the block‐and‐ash flow, causing a bulk‐up process, waxing flow, channel overspill and unexpected runout. The study demonstrates that deposit‐derived pyroclastic currents from perched temporary tephra stores pose a particular hazard that is easy to overlook and requires a new, different approach to hazard assessment and monitoring.

Progress in physicochemical properties of ash/slag from co-gasification of agroforestry waste biomass and coal

Co-gasification of agroforestry waste biomass and coal realizes energy-saving, low-carbon emission, clean and efficient raw material conversion by taking advantage of their similarities and complementarities. The physicochemical properties of ash slag for raw materials are one of the key factors affecting the stable operation of co-gasification. It is the focus of co-gasification research. This paper reviews the research status of physicochemical properties of ash slag from co-gasification of agroforestry waste biomass and coal. It mainly includes the similarity and difference between agroforestry waste biomass ash and coal ash, the fusion and viscosity-temperature characteristics of mixed ash, the effect of alkali/alkaline earth metals in mixed ash on co-gasification reactivity, and sintering behavior during the slagging process. The influence mechanism of adding agroforestry waste biomass on the melting flow and sintering behavior of mixed ash is discussed. The prediction models and methods of fusion characteristics, viscosity-temperature, and slagging characteristics of mixed ash are also summarized. Finally, the future research directions of ash slag from co-gasification of agroforestry waste biomass and coal are proposed.

Eocene mammals from volcaniclastic deposits of the Somun Cura Plateau: biostratigraphic implications for north Patagonia Paleogene

The Paleogene terrestrial faunal succession and its associated bearing volcaniclastic deposits has been exhaustively studied in central Patagonia, but there is still no acceptable litho-bio-chronostratigraphic ordering for the extra-Andean North Patagonia. The only references on Paleogene mammals bearing deposits north to Chubut River are imprecise and contradictory. West to Ingeniero Jacobacci (Río Negro Province, Argentina), the paleontologist and archaeologist Rodolfo Casamiquela reported a fossiliferous succession with Casamayoran or Mustersan (Eocene) and Deseadan (Oligocene) mammals from rocks currently mapped as the Las Chacras Formation. This unit includes acid to intermediate tuffs, ignimbrites, paleosols, conglomerates, and basalts originated in a perivolcanic fluvial system, under a seasonal subhumid-humid climate according to predominant pedogenic features. As a result of our fieldworks and fossil collection in the area of Ingeniero Jacobacci, and the revision of the materials collected by Casamiquela in the forties and fifties (with well-known stratigraphic origin), we identified a single mammal association from the lower section of the Las Chacras Formation (here named the Lower Las Chacras fauna) composed by: Plesiofelis schlosseri Roth, 1903 (Sparassodonta), Trigonostylops Ameghino, 1897, Astraponotus Ameghino, 1901 (Astrapotheria), Propyrotherium Ameghino, 1901 (Pyrotheria), Pseudhyrax eutrachytheroides Ameghino, 1901, Eohegetotherium priscum Ameghino, 1901, Puelia sigma (Ameghino, 1901), Periphragnis Roth, 1899 (Notoungulata), Isutaetus depictus Ameghino, 1902 (Cingulata), and a new member of Adianthidae (Litopterna) and probably of Pichipilidae (Paucituberculata). This assemblage is closer to that derived from the Rosado Member of the Sarmiento Formation at Gran Barranca, central Patagonia (type locality of the Mustersan Land Mammal Age) dated in ca. 38 Ma (late middle Eocene). A pyroclastic flow associated to the bearing deposits of Ingeniero Jacobacci was dated (K-Ar) in 39.2±2 Ma, value compatible with the Mustersan age here inferred for the Lower Las Chacras fauna. The alleged occurrence of Deseadan mammals in these levels was based on remains of an isotemnid notoungulate incorrectly identified as a leontinid. The presence of the Tinguirirican (early Oligocene) notoungulate Eohegetotherium priscum, with more apomorphic dental traits than in its Eocene allies, and of an astrapotheriid more derived than Astraponotus suggests that some advanced faunal elements would have been established in North Patagonia earlier than in central Patagonia.