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Fires can have devastating effects on cultural stone heritage. Micro and macro changes occur in building stones exposed to high temperatures. Micro changes also cause changes in the physical properties of rocks. These changes not only cause instant damage to the monuments, but also make them less resistant to atmospheric processes and increase the rate of deterioration. Modelling these changes in cultural heritage in a laboratory environment can play an important role in ensuring the continuity of monuments. For this purpose, pyroclastic rock taken from the Niğde (Turkey) region was subjected to heat-treatment and the changes in the samples were investigated with XRD, SEM-EDX, TGA, spectrophotometry, porosity, P-wave velocity, capillary water absorption, and heat treatment loss. It was determined that the mineralogical changes in the structure of the rock with the increase in temperature affected various micro and macro properties. [ABSTRACT FROM AUTHOR]

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This study aimed to investigate the usability of the Leeb hardness test in determining changes in strength as a result of atmospheric weathering in works of cultural heritage built with low-strength pyroclastic rocks. To this end, the effects of weathering processes on strength properties were investigated in two building stones commonly used in Niğde province located in the Cappadocia (Turkey) region, which contains the most important works of cultural heritage created using low-strength pyroclastic rocks. The index, strength, mineralogical, and petrographic properties of rocks were first investigated. Then, freeze–thaw (F-T) and salt crystallization (SC) tests, the weathering processes of which consisted of six periods, were performed on samples prepared in cubic form. After the F-T and SC processes, the macro change in the samples and changes in weight loss, uniaxial compressive strength (UCS), and Leeb hardness (HL) values were determined. Highly correlated linear relationships were obtained between the SC and F-T cycles of the samples and the UCS and HL values. The HL test was applied to samples for which the UCS test could not be applied due to the loss of sample integrity after the advancing cycles of the accelerated weathering tests. Linear relationships with high correlation were determined between the UCS and HL values obtained from the samples after the accelerated weathering test. This study revealed that the HL approach could be used as an alternative in modeling the strength parameters of the weathering processes of the structures of cultural heritage built using low-strength rocks. [ABSTRACT FROM AUTHOR]

Indigenous oral traditions of the Líl̓wat Nation recount observations of Qw̓elqw̓elústen (Mount Meager), a Garibaldi Volcanic Belt volcano in southwestern British Columbia, Canada; and associated eruptive activity, mass-wasting, and outburst flooding. We present Líl̓wat observations relating to Qw̓elqw̓elústen's ∼2360 cal year B.P. eruption and its aftermath, a devastating outburst flood down the Lillooet valley. The Copper Canoe story correlates with the event sequence of pyroclastic damming of the Lillooet River and an outburst flood traveling far downstream, interrupting salmon runs and displacing people. Other stories suggest an eruptive plume and fumaroles. Recounted valley-floor changes, with proximal scouring and downstream filling of marshes allowing human resettlement, closely parallel and augment geological evidence, showing that oral traditions are equally important in holding landscape history. Oral traditions portray dramatic landscape changes, some by the Transformers, said to have traveled this land to make imperfect things right. Geologically documented debris-flow delta progradation and infill of the upper 50 km of Lillooet Lake since ∼12 000 cal B.P. underscore the land's dynamism and the need for both sources to inform planning for future eruptive, mass-wasting, and flooding events. Traditional landscape knowledge, like Western science, is observational and evidence-based, though interpretations can differ given Indigenous belief in a sentient landscape, capable of acting with intention. Binding of stories to geographical locations has functioned as a powerful mnemonic device to preserve orally transmitted information across many generations. [ABSTRACT FROM AUTHOR]

Sebuku Island is located at the southeastern tip of Kalimantan Island and has geological similarities with the Bobaris-Meratus complex in distribution pattern and stratigraphic sequence. The pattern of straightness of geological structures between the two, both folds and faults, is generally directed from northeast-southwest to northwest-southeast. The previous geological research on Sebuku Island focused on the distribution of ultramafic rocks, which are speculated to contain iron, particularly from laterite soils. This research aims to determine the rock units in the study area to update the geological map of Sebuku Island, especially in the Sei Pinang and Halaban areas. The research method consists of fieldwork, laboratory analyses, and data analyses. The geological fieldwork collected 34 samples from detailed mapping on outcrops, trenching, and drilling. Geological structure observations were carried out on fresh outcrops and measured 57 structural geological elements from 6 locations. Petrographic analysis of 34 samples was carried out with the aim of determining rock type and mineralogical composition. Stereographic analysis of geological structure measurement data was used to define the general direction and type of geological structures in the investigated outcrops. The geological map is constructed on the basic topographic map in the scale 1:50,000 using Map-Info Pro v17.0.5. Based on petrographic observations and detailed field observations, especially in North Damar, from surface outcrops and drill core observations from Madang, the following results are revealed. In the geology of North Damar, in particular, and Sebuku Island, in general, the lithology can be described as an ultramafic rock unit (lherzolite, harzburgite, and dunite), pyroclastic rock unit (crystallo-lithoclastic tuff and crystalloclastic tuff), limestone unit, dike rock unit (microgabbro and diorite), sandstone unit, and alluvial deposit. Almost 60% of Sebuku Island outcrops belong to the ultramafic rock units, which are tectonically covered by crystalline lithic tuff and crystalline tuff and volcaniclastic rock units with interbedded limestone, unconformably covered by sandstone units, alluvial deposits, and swamp deposits. Microgabbro and diorite were observed from the drill core and were not exposed to the surface. Hydrothermal mineralization is indicated by quartz veins cross-cutting the pyroclastic rock group observed in drill cores. This research shows a more detailed geological description of the study area compared to previous research and regional geological map.

Four small scoria cones in the western outskirts of Al Madinah City, the Kingdom of Saudi Arabia, form a distinct young volcanic landmark. These volcanoes, despite their very small size, provide one of the most fundamental sources of information about the early eruption mechanism of rising mafic magma in the context of an active volcanic field located next to a city with over one million people. An initial study of the area in 2012–2013 confirmed that these sites had a significant phreatomagmatic phase in their opening stage, leaving behind characteristic pyroclastic successions likely to be covered by subsequent eruptive products. The fact that in this location, unequivocal evidence emerged to show that explosive magma-water interaction driven eruptions occurred in the largely magmatic (“dry”) explosive style, and volcanic field evolution confirmed that this site has high geoheritage value. Since the first research was 20 years ago, a restudy of the present-day condition of the scoria cone was conducted. Applying satellite imagery, remote sensing and direct site visit, we find that about a third of the cone surface area has been modified and at least a quarter of its volume has vanished. Further excavation for cone material however opened the entire western side of the cone, exposing a nearly 5-m-thick succession of accidental lithic pyroclast-dominated lapilli tuff and tuff breccia, confirming that this location had a significant phreatomagmatic phase in its opening eruptions. This location shows graphically the need for geoconservation to preserve such sites that are potentially the only, or best locations to show the potential eruptive styles and scenarios of future eruptions if they occur in similar environments.

Lunar Pyroclastic Deposits (LPDs) are sites of explosive volcanism and often occur in areas of effusive volcanism on the Moon. On Earth, it has been observed that most volcanism has both effusive and explosive phases, whereas on the Moon, these two types of volcanism have typically been considered separately. We hypothesize that the relationship between explosive and effusive volcanism on the Moon is similar to what is observed on the Earth, where individual eruptions can experience multiple phases rather than one type of volcanism always preceding another or occurring separately. We present observations from the Moon Mineralogy Mapper detailing compositional relationships between volcanic features in the lunar Montes Apenninus region. We evaluated whether co‐located LPDs and effusive features (e.g., rilles, mare) could have erupted from the same volcanic vent or even at the same time based on their compositional similarities and stratigraphic relationships. We found that the LPDs have varied stratigraphic relationships with co‐located effusive features. We identified LPDs near sinuous rilles that may be related to the formation of the rille, where explosive and effusive volcanism occurred at the same vent (e.g., Mozart Rille), and LPDs that may be unrelated to the rille (e.g., Rimae Bode and Rima Bode LPD). Our results suggest that lunar volcanism can mirror terrestrial volcanism, with explosive and effusive eruptions demonstrating more complex dynamics and relationships than previously thought. This variability suggests that the relationship between LPDs and nearby volcanic features cannot be generalized for studies on their resource potential, eruption styles, or deposit volume. Plain Language Summary: Volcanic eruptions can be explosive or non‐explosive (effusive), and sometimes both types of eruptions can be seen at a single volcanic site. This can be interpreted as two types of eruptions happening at the same time from the same vent, happening at the same time from different vents, or happening from the same vent at different times. Having different eruption types is common for volcanoes on Earth and often a volcano will erupt explosively and effusively at the same time. Even though we see signs of explosive and effusive volcanism on the Moon, there is currently no active volcanism to inform how these eruptions are correlated. To study this, we use the Moon Mineralogy Mapper, an instrument that helps identify minerals in the products of explosive volcanism called Lunar Pyroclastic Deposits (LPDs). We also included effusive features around these LPDs to understand whether these features could have erupted at the same time or from the same vent. We found that LPDs are complex—some of the explosive deposits originate from the same vents as the effusive features, but some explosive deposits completely cover nearby effusive features, so we could not determine a consistent pattern. Key Points: The mineralogy and stratigraphic relationships of explosive and effusive volcanic deposits are investigated in the Montes Apenninus regionExplosive and effusive deposits are identified at the same vent, indicating that individual eruptions can experience multiple phasesEruption dynamics and the volcanic history cannot be generalized to all deposits; detailed analysis of each individual deposit was necessary for this study [ABSTRACT FROM AUTHOR]

The remnants of explosive volcanism on Mercury have been observed in the form of vents and pyroclastic deposits, termed faculae, using data from the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) onboard the Mercury surface, space environment, geochemistry, and ranging (MESSENGER) spacecraft. Although these features present a wide variety of sizes, shapes, and spectral properties, the large number of observations and the lack of high-resolution hyperspectral images complicates their detailed characterisation. We investigate the application of unsupervised deep learning to explore the diversity and constrain the extent of the Hermean pyroclastic deposits. We use a three-dimensional convolutional autoencoder (3DCAE) to extract the spectral and spatial attributes that characterise these features and to create cluster maps constructing a unique framework to compare different deposits. From the cluster maps we define the boundaries of 55 irregular deposits covering 110 vents and compare the results with previous radius and surface estimates. We find that the network is capable of extracting spatial information such as the border of the faculae, and spectral information to altogether highlight the pyroclastic deposits from the background terrain. Overall, we find the 3DCAE an effective technique to analyse sparse observations in planetary sciences. [ABSTRACT FROM AUTHOR]

In the cultural stone heritage, progressive deteriorations develop over time with the effect of atmospheric processes. These deteriorations can reach to a significant degree that threaten the integrity of the monuments built from weak-strength rocks. In this study, it is aimed to determine the deteriorations caused by atmospheric processes on the monument surface in cultural heritage works built by carving into low-strength pyroclastic rocks by non-destructive tests (NDTs). To this end, two historic structures in the Kilistra Ancient City of Konya (Turkey) were selected. The index, strength, mineralogical and petrographic properties of the rocks, in which the monuments were carved, were first investigated. Then, contour scaling, crack, efflorescence and biodeterioration types were determined on the facades of the monuments. Later, NDT deterioration change maps were prepared based on the data obtained by performing the relative humidity, Schmidt hammer rebound (SHR), and P-wave velocity (V p) measurements on the facades of the monuments. In the deterioration maps, it was determined that the SHR and V p values of the rock were low in the capillary, infiltration, and crack zones with water penetration in the monuments built on low-strength pyroclastic rocks. However, deterioration was less in the regions with more limited water access according to zones. [ABSTRACT FROM AUTHOR]

Four small scoria cones in the western outskirts of Al Madinah City, the Kingdom of Saudi Arabia, form a distinct young volcanic landmark. These volcanoes, despite their very small size, provide one of the most fundamental sources of information about the early eruption mechanism of rising mafic magma in the context of an active volcanic field located next to a city with over one million people. An initial study of the area in 2012-2013 confirmed that these sites had a significant phreatomagmatic phase in their opening stage, leaving behind characteristic pyroclastic successions likely to be covered by subsequent eruptive products. The fact that in this location, unequivocal evidence emerged to show that explosive magma-water interaction driven eruptions occurred in the largely magmatic ("dry") explosive style, and volcanic field evolution confirmed that this site has high geoheritage value. Since the first research was 20 years ago, a restudy of the present-day condition of the scoria cone was conducted. Applying satellite imagery, remote sensing and direct site visit, we find that about a third of the cone surface area has been modified and at least a quarter of its volume has vanished. Further excavation for cone material however opened the entire western side of the cone, exposing a nearly 5-m-thick succession of accidental lithic pyroclast-dominated lapilli tuff and tuff breccia, confirming that this location had a significant phreatomagmatic phase in its opening eruptions. This location shows graphically the need for geoconservation to preserve such sites that are potentially the only, or best locations to show the potential eruptive styles and scenarios of future eruptions if they occur in similar environments. [ABSTRACT FROM AUTHOR]

Harrat Khaybar is an active monogenetic volcanic field in western Saudi Arabia that hosts spectacular monogenetic volcanoes and a Holocene volcanic cone with extensive lava fields. The volcanic region is a subject of intensive land use development, especially along tourism ventures, where the volcanic features are the key elements to utilize for increasing visitation rates to the region. The youngest eruption is suspected to be Holocene and occurred fewer than 5000 years ago based on the cross-cutting relationship between the youngest lava flows and archaeological sites. Lava flows are typical, from pāhoehoe to 'a'ā types with great diversity of transitional textural forms. Here, we recorded typical transitional lava flow surface textures from the youngest flows identified by digital-elevation-model-based terrain analysis, satellite imagery, and direct field observations. We performed lava flow simulations using the Q-LavHA plug-in within the QGIS environment. Lava flow simulations yielded satisfactory results if we applied eruptions along fissures, long simulation distances, and ~5 m lava flow thickness. In these simulations, the upper flow regimes were reconstructed well, but long individual lava flows were not possible to simulate, suggesting that morphological steps likely promoted lava ponding, inflation, and sudden deflation by releasing melts further along shallow syneruptive valley networks. [ABSTRACT FROM AUTHOR]

The eruption of the Cumbre Vieja volcano on 19 September 2021, resulted in the deposition of large quantities of volcanic ash (VA), causing a great impact on the citizens. This work aims to study the properties of this volcanic ash as pozzolanic raw materials to establish their potential use in the development of sustainable cement. Results of chemical and technical characterization are presented. To achieve this goal, Ordinary Portland Cement (OPC) was replaced with standardized percentages of OPC/VA: 10, 25, and 40%. Characterization studies were carried out using chemical analysis of X-ray fluorescence (XRF), chemical quality analysis (QCA), pozzolanicity test (PT) at 8 and 15 days, as well as determining the mechanical strength (MS) at 7, 28, and 90 days. The results obtained by XRF and QCA established that the chemical composition of the VA corresponds to that of the natural pozzolan typical of pyroclastic genesis. The PT test showed that the analyzed samples have a marked pozzolanic nature, both at 8 and 15 days, showing a significant increase in their hydraulic reactivity. Likewise, the MS tests confirmed a continuous increase in mechanical compressive strength, which increased significantly from 7 to 90 days of curing, reaching more than 58 MPa. On the other hand, mechanical tests showed that the three types of dosages used OPC/VA: 10, 25, and 40% were equally effective, with OPC/VA formulations: 10–25% being the most effective. The results obtained in this research could be used by local industries as a guide for the correct use of the volcanic materials of this island, both for the manufacture of construction materials, such as aggregates, and to produce pozzolanic cement with low CO2 emissions, thus having a positive impact on the environment. Finally, the great natural availability of natural VAs in the surrounding areas of La Palma could cover part of the needs for materials used in the construction and restoration of houses and infrastructures damaged during the volcanic eruption. [ABSTRACT FROM AUTHOR]

AbstractThis article is the first published example of the application of (tephra) event stratigraphy in the Qom Formation as well as the temporal and spatial distribution of the Qom Formation pyroclastic deposits. The presence of igneous (volcanic) associations is the most obvious facies change of the Qom Formation. The tuffaceous limestones and tuff units of both Bozdan and Kagharaki sections (in the southeast of Kerman province) are late Rupelian in age, indicating the occurrence of a volcanic event in NW Jazmourian at the same time. The pyroclastic deposits of the Qom Formation have a significant and regular extent in different areas of the formation realm (from Jazmourian to Mako). In general, it can be said that the pyroclastic units of the Qom Formation are mainly distributed in the following three areas: 1) Jazmourian–Jiroft–Sirjan (fore-arc); 2) Southwest of the Natanz–Kashan–Qom–Saveh belt (mainly in intra-arc); and 3) Zanjan region (SE, S, SW, W, and NW of Zanjan). The thickness and age of these deposits vary in different sections.Keywords: Qom Formation, Pyroclastic, Event stratigraphy, Tuff, Oligo–Miocene. IntroductionThe Qom Formation (Oligocene–Early Miocene) comprises thick successions of marine marls, limestones, gypsum and siliciclastics that were deposited on extensive mixed carbonate–siliciclastic ramps (Reuter et al. 2009), in the Sanandaj–Sirjan fore-arc basin, Urumieh–Dokhtar magmatic arc (Intra-arc basin) and Central Iran back-arc basin (Mohammadi et al. 2013, 2015, 2019, Mohammadi and Ameri 2015; Mohammadi 2022). The presence of igneous (volcanic) associations is the most obvious facies change of the Qom Formation. Carbonate deposition of the Qom Formation took place under conditions of periodic to almost continuous influx of pyroclastic material. The presence of pyroclastic material throughout some stratigraphic sections indicates that at the time of deposition an island-arc volcanic complex was active nearby (Okhravi and Amini 1988). This article is the first published example of the application of (tephra) event stratigraphy in the Qom Formation and also the first comprehensive study on the temporal and spatial distribution of the Qom Formation pyroclastic deposits. Although geological investigations on the Qom Formation started more than 160 years ago, surprisingly little information is available concerning the pyroclastic deposits of the Qom Formation. The aims of this study are therefore to: 1) investigate the relative age of the pyroclastic deposits of the Qom Formation in the southeastern Kerman province; 2) investigate the temporal and spatial distribution of the Qom Formation pyroclastic deposits; 3) present a map showing the distribution of the pyroclastic deposits of the Qom Formation; and 4) use the pyroclastic units as a key unit in event stratigraphy. Material & MethodsThis article consists of two parts. First, the Qom Formation pyroclastic deposits in two stratigraphic sections of Bozdan and Kagharaki (in the southeast of Kerman province) are discussed. Second, the temporal and spatial distribution of the Qom Formation pyroclastic deposits is discussed.Bozdan and Kagharaki (in the southeast of Kerman province) were studied bed by bed. Thin sections were prepared from lithified hard samples, while unconsolidated marly samples were washed, sieved, and screened for foraminifera contents. A total of 105 and 46 samples were collected from the Bozdan and Kagharaki section, respectively. All samples were studied in detail and particular attention has been paid to foraminifera. The age of the study sections as well as the age of the tuff/tuffaceous units was determined based on the vertical distribution of foraminifera, Qom Formation biozonation by Mohammadi (2022) and also the stratigraphic position. To accomplish the second part of the article, almost all related articles are reviewed and analyzed. Discussion of Results & Conclusions The Bozdan section is located 35 km northeast of south Roudbar City. Its lower contact with Eocene volcanic rocks is well exposed. Outcrops of the Qom Formation in the Bozdan section, 440 m thick, consist mainly of medium to thick-bedded and massive limestones, reefal limestones, marls, tuffaceous limestones, and tuffs. A tuff unit of90 m thickness is intercalated in the lower part and separates the lower (30 m) and upper carbonate unit ( 320 m).The Kagharaki section is located in the southeast of Jiroft City. In the Kagharaki section, the tuff and tuffaceous layers are present merely in the lower 56m which consist mainly of medium to thick-bedded and massive limestones, reefal limestones,tuffaceous limestones and tuffs.The presence of Nummulites in the tuffaceous limestones of the Kagharaki and Bozadan sections, as well as in the tuff unit of the Bozadan section is indicative of contemporaneous volcanic activity in the late Rupelian.The spatial distribution of the Qom Formation pyroclastic deposits is shown on a new map.In general, it can be said that the pyroclastic units of the Qom Formation are mainly distributed in the following three areas: 1) Jazmourian–Jiroft–Sirjan (fore-arc); 2) Southwest of the Natanz–Kashan–Qom–Saveh belt (mainly in intra-arc); and 3) Zanjan region (SE, S, SW, W, and NW of Zanjan).In general, the pyroclastic units of the Qom Formation are absent in the following areas: 1) 1) in the north and northwest of Abadeh; 2) in the areas where the evaporite deposits of the Qom Formation are present; 3) Hamadan–Sanandaj–South Bijar area; and 4) southeast, south and southwest of Urumieh Lake.

In extensional and transtensional basins, the dual action of basin‐forming tectonism and explosive volcanic activity results in deposition of complex volcano‐sedimentary successions. Since both aspects contemporaneously affect sediment‐dispersal systems, it is difficult to distinguish one from the other by analyzing volcano‐sedimentary successions. To discriminate tectonic influence, basin fills of the Miocene, pull‐apart Janggi Basin were investigated. Here, the contemporaneous influence of tectonic subsidence and explosive volcanism formed <966 m thick, conformable volcano‐sedimentary successions composed of laterally extensive, pumice‐bearing, unwelded pyroclastic deposits and nonmarine sedimentary rocks formed under humid climatic conditions. Based on Laser Ablation – Multiple Collector – Inductively Coupled Plasma Mass Spectrometry zircon U–Pb age data, these successions were deposited from 21.1 ± 0.2 to 20.1 ± 0.1 Ma. After deposition of basinwide, tens of metres thick, and unwelded pyroclastic deposits, the directly overlying facies successions (FS‐1 and FS‐2) show contrasting depositional features to the classical model of volcaniclastic sedimentation. Facies succession‐1 is represented by fluvial conglomerates composed mostly of (sub)rounded pebble and cobble sourced from basement. The supply of basement‐derived clasts through fluvial systems resulted from development of physiographic relief during or soon after the eruption by syndepositional tectonic subsidence. Facies succession‐2 occurs directly on pyroclastic deposits that cover FS‐1 and show coarsening‐upward trends, and is composed of basal lacustrine mudstones and overlying resedimented volcaniclastic sandstones showing a progradational geometry, interpreted as a result of progressive filling of the lake by remobilized volcaniclastic sediments. Occurrence of basal lacustrine laminated mudstones indicates that syndepositional creation of the accommodation by tectonic subsidence exceeded forceful input of pyroclastic and remobilized volcaniclastic sediments, resulting in a delayed sedimentary response to explosive volcanic eruptions. This study shows that, despite voluminous production of volcaniclastic sediments, tectonic activity controlled sediment type and stacking patterns. Therefore, these depositional features allow to discriminate tectonic effects from complex volcano‐sedimentary successions, enabling to reconstruct basin evolution. [ABSTRACT FROM AUTHOR]

Recognition of ancient pyroclastic rocks made up of particles of explosive volcanic origin and deposited by primary volcanic processes and/or rapid sedimentation of freshly erupted, texturally unmodified particles vis-a-vis secondary volcaniclastic deposits derived by significant reworking during transport of primary volcanic particles prior to deposition, but long after volcanism (epiclastic) remains a major challenge. A volcanic conglomerate having both rhyolitic clasts and matrix within the ~2.5 Ga Bijli Rhyolite in the Dongargarh large igneous province in the Bastar craton, is earlier interpreted to be of epiclastic origin, primarily because of the presence of large rounded rhyolite clasts imparting conglomeratic appearance to the deposit, and thereby considered representing a significant time break (unconformity) between explosive Bijli volcanism and the deposit. Based on new field and petrography studies, we identified the ~125 m thick volcanic conglomerate as rapidly sedimented texturally unmodified rhyolitic breccia-conglomerate linked to coeval incipiently welded pyroclastic flow that occurred during caldera collapse related to mafic-recharge-mediated Bijli volcanism, without significant time break. We ascribed the rounding of rhyolite clasts to surface tension of hot crystallising molten magma in plastic state and partly to mechanical interactions of particles on steep slopes in such volcanic settings. This study may help clarify origin of similar deposits in deformed metamorphosed provinces elsewhere. [ABSTRACT FROM AUTHOR]

Mount Kelud is located in the eastern part of Java in Indonesia, and an eruption occurred there in 2014. This eruption produced volcanic materials, particularly distributed on the northeast and southern slopes. This Plinian eruption and the new pyroclastic materials could possibly have influenced changes to the soil development and classification but to date there have been no investigations to determine the nature of such changes. The main objectives of this study were to determine these changes in soil characteristics and classification affected by pyroclastic materials which were thicker on the north-east compared to the south slopes. For each slope, north-east (PTL) and south (PS), five slope positions were studied, i.e., top (1), upper slope (2), middle slope (3), lower slope (4) and plains (5). The results show that the thickness of the new pyroclastic material is less than 50 cm (in fact always less than 30 cm occurred in field measurements), but having slight varia- tions in thickness depending on the sequence concerned. Hence the definitional requirement for a buried soil of 50 cm was not found following the 2014 eruption. Compared to the south (PS) slopes where no C horizon was developed, on the northeast (PTL) a varying thickness but less than 30 cm of new materials was found. This new pyroclastic material had a loose, single structure, light soil colour, high bulk density in the top layers but coarse texture, low organic carbon content and was low in exchangeable cations. The andic properties as defined in Soil Taxonomy (Soil Survey Staff, 2014) were not met in these new deposits. However based on this study, classification differences have occurred in the Upper Slope (PTL-2 Vitrandic Humudepts and PS-2 Humic Udivitrands), and in the Middle Slope (PTL-3 Vitrandic Humudepts and PS-3 Typic Udivitrands). The Lower Slope (PTL-4) and Plains (PS-5) were Fluvaquentic Endoaquepts and Fluvaquentic Humaquents respectively. [ABSTRACT FROM AUTHOR]

A study of Collembola on land affected by pyroclastic material of Kelud Volcano, Ngantang Malang was conducted to elucidate the abundance and diversity of soil Collembola in a volcanic environment at various elevations. The study area was divided into two habitats, affected and unaffected by pyroclastic materials at each altitude of 900 m above sea level (asl), 1000 m asl, and 1100 m asl. The research was carried out in June 2019 using a stratified purposive sampling method. Soil Collembola was collected on litter and soil layers using a square frame, length and width of 20 x 20 cm to a depth of 5 cm. Litter and soil layer samples were extracted using Modified Berlese Funnel. Collembola was identified based on morphospecies up to the genus level. Each genus was found only one species, therefore genus was considered as a species. Results of the study showed that soil Collembola on land affected by pyroclastic has 20 species and an abundance of 8790 individuals/m2. In the pyroclastic unaffected areas, were found 33 species and an abundance of 3865 individuals/m2. Entomobrya sp. was dominant in the litter and soil layers of all the study areas. This indicates that Entomobrya sp. is a species that is easy to adapt and has high habitat tolerance.

Natural geophysical mass flows are among the most complex granular systems and their dynamics are often modified by the presence of an interstitial fluid. Prediction of their runout requires the development of models estimating the solid stresses in these hazardous currents wherein excess pore-fluid pressure can develop. We use discrete element modelling (DEM-CFD) with a Coarse-Graining post-processing technique (CG) to investigate the rheology of unsteady gas-particle fluidized to non-fluidized granular beds placed on horizontal and inclined planes. Similar to fluidized beds immersed in viscous fluids, the effective friction coefficient of air-fluidized beds can be defined as a function of the classic μ(I)-rheology and the non-dimensional fluid or solid pressure to explain the failure and dynamics of granular flows with excess pore pressure on inclines. However, dilation imposed by fluid drag and particle collisions in gas-particle fluidized beds can drastically change its effective frictional properties. In contrast with the common assumption in water-particle flows that granular temperature is negligible, in our gas-particle simulations, the contribution of the velocity fluctuations to the stress tensor is significant. Hence, the shear stress is found to be non-zero even when the flow is fully fluidized in the inertial regime. These results suggest the need to better understand velocity fluctuations to predict the effective viscosity of sheared fluidized mixtures and are relevant for many applications. Notably, a unified approach is useful for many geophysical flows that encompass a range of fluidization conditions in a single flow such as pyroclastic density currents and snow avalanches. [ABSTRACT FROM AUTHOR]

Lamongan volcano is one of the unique volcanoes in the Sunda Volcano. This volcano has side eruption centers or on the slopes of the volcano. The morphology of parasitic eruptions in this volcanoes complex includes maars and boccas. There are about 64 parasitic eruption centers consisting of 37 volcanic cones (bocca) and 27 ranu (maar). The purpose of this research is to study the characteristics of lithology and petrogenesis of this volcano complex, especially in Ranu Pakis and surrounding areas. The analytical method used is to do geological mapping and petrographic analysis. The lithology found in this research area consists of magmatic and phreatomagmatic eruption deposits. Genetically this lithology includes pyroclastic flow, pyroclastic fall (scoria fall and phreatomagmatic scoria fall/accretionary lapili), tuff (phreatic) and basaltic lava. In some pyroclastic deposits, especially in maar there are fragments of accretionary lapilli, while in bocca there are basaltic lavas. Other fragments present in pyroclastic deposits are basalt scoria blocks and bombs embedded in the groundmass of volcanic ash. The results of petrographic analysis indicate that the volcanic rocks in the study area are calc alkaline affinity consisting of pyroxene andesite, basalt and pyroxene basalt lava. The pyroxene basalt lava is composed by plagioclase, clinopyroxene and little olivine embedded in the volcanic glass. Lavas are structured scoria and textured porphyritic, intersertal, trachytic, aphyric and pilotaxitic. Trachytic texture is found in the basalt fragments of pyroxene from the pyroclastic fall deposits in Ranu Pakis and Ranu Wurung. While pyroxene andesite lavas composed by plagioclase, clinopyroxene embedded in the volcanic glass. Lavas are structured scoria and textured porphyritic, intergranular, pilotaxitic and aphyric.

Potential volcano in several provinces in Indonesia played a significant role in the formation and quality of soil development. Soils that developed from the volcanic ashes are often thought to contribute greatly to improve soil fertility, without regard to the nature and composition of the volcanic ash produced. Volcanic ash generated from the results of volcanic activity has a different composition, there are basaltic, andesitic and granitic, thereby affecting the formation and characteristics of the soil. The objective of this study was to determine the soil development from different types of pyroclastic materials generated from the Lokon volcano in North Sulawesi. The study was carried out at the foot of Mount Lokon with three-point of coordinates, namely (1) 1o 21’18.0“ N and 124o 49' 20.2” E, (2) 1o 21’ 30.2“ N and 124o 49' 2.8” E, (3) 1o 24’ 23.70“ N and 124o 52' 17.30“ E. Arc-GIS 10.3 software was used for mapping the location of the study with the base maps of a regional geological map and the topography map. Soil characteristics including texture, pH, organic-C, Cation Exchange Capacity (CEC), and mineral contents were determined. The results show that there are two types of pyroclastic as the source of soil development from volcanic ash, namely; 1) basaltic pyroclastic with 43.26% SiO2 that is resulted from the first magmatic eruption and 2) andesitic pyroclastic with 5.09% SiO2 that is resulted from the late magmatic eruption. Basaltic pyroclastic contains Fe 37.63%, Al 11.35%, Ca 13.17% and Mg 5.69%, while andesitic pyroclastic contains Fe 38.35%, Al 6.87%, and Ca 8.61%. Rainfall ranges from 2000 to 3500 mm yr-1, which helped the soil formation and influenced the characteristics of the soil, such as sandy loam texture, soil organic-C content 3.08% , CEC 23.24 cmol (+) kg-1 and clay CEC 148.93 cmol(+) kg-1. The clay minerals in the soil consist of vermiculite, kaolinite and, halloysite. Cation supply from basaltic pyroclastic influences the formation of vermiculite mineral, whereas andesitic pyroclastic largely influences the formation of the kaolinite mineral. The formation of soil texture with a predominance of the sand fraction is more influenced by the type of andesitic pyroclastic that is more resistant to weathering processes.

Sabalan volcano is located in the northwest part of Iran and 25km south of Meshkinshahr in the west Alborz-Azerbaijan structural zone. The rocks forming the Sabalan and its eastern and northern slopes are covered with significant amounts of white-gray pyroclastic deposits, which is indicating a very intense explosive activity at the last stage of this huge volcano activity. After conducting field studies and analyzing the results obtained using the mathematical calculations, a Plinian eruption was detected, and the extrapolated volume of the latest pyroclastic fall eruption was estimated 3.24 km3, and the eruption of Sabalan rated a VEI of 5. Also, due to the shape of the isopach curve, the role of wind in dispersing these deposits is from the west to the east. Also based on geochemical data, the Sabalan’s ignimbrite was rhyodacitic with calc-alkaline signatures and the high ratios of Ba/Nb>28 and Ba/Ta>450 are consistent with subduction related zone.

Arabia Terra is an ancient, geologically complex region of Mars. It is not typically described as volcanic because it lacks prominent, easily recognizable shield volcanoes. However, Arabia Terra contains flood lavas and widespread layered materials that might represent airfall pyroclastics from unknown sources. Here we explore the geology of some complex topographic depressions in Arabia Terra previously hypothesized to represent collapse features termed "plains style caldera complexes," an enigmatic category of volcanic feature on Mars characterized by surface collapse rather than construction of topographic shields. Geomorphological observations and geologic mapping carried out here support a volcanic origin of these features, providing a possible source for volcaniclastic sediments. The identification of caldera complexes in Arabia Terra raises the questions of how they are linked to the geotectonic setting of the region and whether similar features might be much more abundant in the ancient Martian crust than is currently recognized. Plain Language Summary: The most recognizable volcanoes on Mars correspond to large topographic shields, similar to Hawaiian volcanoes. These are constructional features built by layer upon layer of lava, with a summit caldera. It is possible that Mars contains many other volcanoes that are less recognizable, however, because they consist only of the caldera complex without the topographic rise built by lava. These calderas could signify much more explosive volcanism or collapse due to migration of magma in the subsurface, or both. In this work, we describe more identifications of plains style caldera complexes, which are collapsed calderas without the easily recognizable shield topography. We describe the geology of these calderas in the Arabia Terra region, their possible links to tectonic setting there, and the possibility that similar features are much more common on Mars than is currently understood. Key Points: Collapsed calderas are recognized in eastern Arabia TerraAncient Martian crust may have far more collapsed calderas than commonly recognizedPlains style caldera complexes could be a source of huge volumes of volcaniclastic materials on Mars [ABSTRACT FROM AUTHOR]

Sedimentary structures deposited from dilute pyroclastic currents are largely dominated by the products of metre‐scale dune bedforms containing backset lamination. Since the first seminal works in the 1970s, the vast majority of the literature called these structures antidunes and chutes‐and‐pools. This consensus led to a loose terminology, either as descriptive terms for structures containing backset beds or as an interpretation of hydrodynamic conditions related to Froude‐supercritical flows. Here, the main characteristics of pyroclastic dune bedforms are summarized and classified under four categories. The literature is examined and a discussion is provided regarding a possible interpretation in terms of supercritical‐flow bedforms, including antidunes, chutes‐and‐pools and cyclic steps. The interpretation of pyroclastic dune bedforms as related to supercritical conditions is a possibility among others, yet open questions remain, and under the present state of knowledge alternative interpretations are equally valid. There is consensus that an interpretation of pyroclastic dune bedforms as related to supercritical flows implies deposition from a basal underflow supporting an internal free‐surface formed at a density interface within the overall current structure. Antidunes are likely to be limited to low‐angle, incipient bedforms. Chutes‐and‐pools may occur in the form of series of steep truncations formed by an erosive supercritical 'chute', with a depositional signature occurring exclusively in the subcritical 'pool' of a Froude jump. Rare examples of cyclic steps may be found as large‐scale undulations with superimposed metre‐scale bedforms, or for short‐scale, fully‐aggrading structures in periodic trains. Additionally, some pyroclastic bedforms may be formed by granular flows passing granular Froude jumps or as frozen granular stationary waves. The dominance of chute‐and‐pool structures over bedforms characterized by relatively more stable morphodynamics (antidunes and cyclic steps) could be the likely result of pulsating flow conditions and abrupt high‐rate deposition, impeding stable flow conditions. In a majority of cases, the growth of pyroclastic bedforms appears triggered by the influence of an inherited bed topography and by bed‐flow feedback effects. Apart from a possible interpretation as supercritical bedforms, other specific dynamics of dilute pyroclastic currents may well explain the characteristics of pyroclastic dune bedform structures. In particular, the inherent turbulence fluctuations, internal organization and highly depositional dynamics may be key to the formation of pyroclastic dune bedforms. In this respect, rather than solely focusing on the Froude dimensionless number of the formative current, theoretical considerations accounting for the Reynolds, Richardson and Rouse dimensionless parameters may be also implemented for the understanding of pyroclastic bedforms. [ABSTRACT FROM AUTHOR]

Dense, glassy pyroclasts found in products of explosive eruptions are commonly employed to investigate volcanic conduit processes through measurement of their volatile inventories. This approach rests upon the tacit assumption that the obsidian clasts are juvenile, that is, genetically related to the erupting magma. Pyroclastic deposits within the Yellowstone-Snake River Plain province almost without exception contain dense, glassy clasts, previously interpreted as hyaloclastite, while other lithologies, including crystallised rhyolite, are extremely rare. We investigate the origin of these dense, glassy clasts from a coupled geochemical and textural perspective combining literature data and case studies from Cougar Point Tuff XIII, Wolverine Creek Tuff, and Mesa Falls Tuff spanning 10 My of silicic volcanism. These results indicate that the trace elemental compositions of the dense glasses mostly overlap with the vesiculated component of each deposit, while being distinct from nearby units, thus indicating that dense glasses are juvenile. Textural complexity of the dense clasts varies across our examples. Cougar Point Tuff XIII contains a remarkable diversity of clast appearances with the same glass composition including obsidian-within-obsidian clasts. Mesa Falls Tuff contains clasts with the same glass compositions but with stark variations in phenocryst content (0 to 45%). Cumulatively, our results support a model where most dense, glassy clasts reflect conduit material that passed through multiple cycles of fracturing and sintering with concurrent mixing of glass and various crystal components. This is in contrast to previous interpretations of these clasts as entrained hyaloclastite and relaxes the requirement for water-magma interaction within the eruptive centres of the Yellowstone-Snake River Plain province. [ABSTRACT FROM AUTHOR]

We present a new geological map of Warrumbungle Volcano created from volcanic facies field mapping, new geophysical, geochemical and geochronological data as well as data from previous studies. Field mapping and petrography defined 19 volcanic and two mixed volcanic--sedimentary facies. Facies identification and distribution in conjunction with geochemical analyses indicate an early shield-forming phase of predominantly mafic and intermediate lavas and pyroclastic deposits, and minor felsic lavas deposited on an irregularly eroded basement of Surat and Gunnedah basin rocks. The shield was subsequently intruded by felsic intermediate to felsic magmas that formed dykes and other intrusions, including possible cryptodomes, and also erupted as lava domes and block-and-ash-flow deposits. A radial dyke swarm cross-cuts most units, although it is concentrated within basement sandstone surrounding the central area of the volcano, suggesting late inflation accompanied by dyke emplacement. Geochemistry indicates differentiation of a single although repeatedly recharged alkaline magmatic suite. Fractionation of olivine, Ti-magnetite and clinopyroxene occurred in mafic magmas, and after reaching 62 wt% SiO2, crystallisation of apatite and alkali feldspar took place. A new U–Pb zircon SHRIMP magmatic crystallisation age of 16.25 ± 0.12 Ma on a felsic block-and-ash flow deposit is in agreement with the recalculated 40Ar/39Ar isochron dates of previous workers. Based on our mapping and the use of volcanic facies to define mappable units, we recommend that the previous Warrumbungle Volcanics be elevated from formation to group status and renamed the Warrumbungle Volcanic Complex. New geological map of Warrumbungle Volcano based on volcanic facies mapping. The volcanic facies and their distribution suggest a complex alkaline shield volcano erupted along regional-scale basement lineaments over an intracontinental 'hot-spot' or heat plume, and intruded by lava domes, cryptodomes, dykes and a radial dyke swarm. New and previous geochemical data suggest differentiation of a single, although repeatedly recharged, alkaline magmatic suite. A new U–Pb zircon SHRIMP date of 16.25 ± 0.12 Ma is in agreement with the recalculated 40Ar/39Ar isochron dates of previous workers. [ABSTRACT FROM AUTHOR]

Volcanic tuffs are important in determining the stratigraphic age of sedimentary sequences, which is closely related to the tectonic, sedimentological, geomorphological, palaeoclimatic, and palaeo-ecological evolution of the sequences. However, it may be difficult practically to identify tuffs in stratigraphic sections, especially when they are altered after deposition. In this study, a series of petrographic, mineralogical, and geochemical analyses was deployed in the tuff layers cropping out in the Lunpola Basin of the central Tibetan Plateau, which is a crucial site for studying the dynamics and processes of the Cenozoic uplift of the Tibetan Plateau and its environmental impacts. In these pyroclastic layers, authigenic analcime is the main volcanic glass alteration product. The analcime-bearing samples are Na-enriched, in contrast to the K-abundant magmatic rocks in the central Tibetan Plateau. The distribution patterns of the rare earth elements (REEs) of the bulk analcime-bearing samples are similar to those of the magmatic rocks but different from those of the analcime-poor sediments and analogues of well-mixed upper continental material (e.g. the upper continental crust and post-Archaean Australian average shales). The distinct distributions of Na and REEs among analcime-bearing samples, analcime-poor sediments, and volcanic rocks reveal that analcime formed both from alteration of volcanic material and from mixing processes with non-volcanic sediments. It is proposed, therefore, that the discrimination plot of Na2O/Al2O3-(La/Yb)N may be used to distinguish the analcime-related pyroclastic rocks from the basin sedimentary sequence, and thus it may provide a means of discriminating between various volcanic material and of supporting age dating by tephrochronology in the central Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Lunar mare regolith is traditionally thought to have formed by impact bombardment of newly emplaced coherent solidified basaltic lava. We use new models for initial emplacement of basalt magma to predict and map out thicknesses, surface topographies and internal structures of the fresh lava flows, and pyroclastic deposits that form the lunar mare regolith parent rock, or protolith. The range of basaltic eruption types produce widely varying initial conditions for regolith protolith, including (1) autoregolith, a fragmental meter‐thick surface deposit that forms upon eruption and mimics impact‐generated regolith in physical properties, (2) lava flows with significant near‐surface vesicularity and macroporosity, (3) magmatic foams, and (4) dense, vesicle‐poor flows. Each protolith has important implications for the subsequent growth, maturation, and regional variability of regolith deposits, suggesting wide spatial variations in the properties and thickness of regolith of similar age. Regolith may thus provide key insights into mare basalt protolith and its mode of emplacement. Plain Language Summary: Following recent studies of how lava eruptions are emplaced on the lunar surface, we show that solid basalt is only one of a wide range of starting conditions in the process of forming lunar soil (regolith). Gas present in the lavas during eruption also produced bubbles, foams, and explosive products, disrupting the lava and forming other starting conditions for mare soil parent material. Key Points: New basalt magma emplacement models explore fresh lava flows that form the lunar mare regolith parent rock, or protolithSome conditions predict immediate formation of a fragmental meter‐thick "autoregolith" that mimics impact‐generated regolithLava flows with significant near‐surface vesicularity, macroporosity, and magmatic foams will create nontraditional regolith growth rates [ABSTRACT FROM AUTHOR]

Sabalan volcano is located in the northwest part of Iran, 25km south of Meshkinshahr in the west Alborz-Azerbaijan structural zone. The eastern and the northern slopes of Sabalan are predominantly covered with significant amounts of white-gray pyroclastic deposits indicating a very intense explosive activity at the last stage of this huge volcano activity. After conducting field studies and analyzing the results obtained using the mathematical calculations, a Plinian eruption was detected, and the extrapolated volume of the latest pyroclastic fall eruption was estimated 3.24 km3, and the eruption of Sabalan rated a VEI of 5. Also, due to the shape of the isopach curve, the role of wind is significant in dispersing these deposits from the west to the east. The overall geochemical features of the Sabalan’s ignimbrite including the rhyodacitic nature with calc-alkaline signatures as well as the high ratios of Ba/Nb>28 and Ba/Ta>450 are consistent with subduction related zone. [ABSTRACT FROM AUTHOR]

In this study, the effects of drying on Atterberg limits is investigated using 30 soil samples taken from 0.2 m to 4 m depths, from nine different landslide sites in pyroclastic deposits in Northern Turkey. Samples for Atterberg limits are prepared by (i) starting from in-situ moisture content without any drying, (ii) drying at 60 °C and (iii) drying at 110 °C. The range of liquid limit values is 35%–103% and plasticity index is 0%–37% when samples are prepared from their in-situ moisture content. Liquid limits of the samples, when they are prepared by drying at 110 °C oven, are 1%–30% lower than the liquid limits prepared from moist condition. The mineralogy of the samples is investigated via X-ray diffraction analyses and Scanning Electron Microscopy photographs, indicating existence of halloysite mineral. Organic contents of the samples, determined by loss on ignition test, is in the range of 4.3%–12.1%. It is concluded that drying significantly influences the results of Atterberg limits if the sample contains some organic material and/or halloysite mineral. Both liquid limit and plasticity index values of the soils decreased as the sample preparation method changed from moist preparation to drying at 110°C. Existing soil classification methods may fail to represent the influence of organic matter on soil behaviour for soils containing <15% organic material. [ABSTRACT FROM AUTHOR]

Abstract: The Medusae Fossae Formation (MFF) is one of the largest sedimentary deposits on Mars. The origin of the MFF is uncertain, though several processes including volcanic, eolian, and ice‐related mechanisms have been proposed in its formation. Here we localize the gravity and topography signature of the MFF and place the first direct constraint on its density. We find that the MFF is a relatively porous unit with a bulk density of 1,765 ± 105 kg m−3. When combined with previous radar measurements, our density constraint rules out the presence of ice as the cause of unusual radar permittivity. Rather, we find the joint radar and gravity constraints imply a dry and highly porous rock unit. Based on the relatively low density, lack of ice, and the previously known enrichment of volatile elements associated with volcanic emissions (Cl and S), we propose that the MFF was deposited by pyroclastic eruptions. Using our density estimate, the mass of the MFF is found to be 2 orders of magnitude greater than the largest terrestrial pyroclastic deposit, making it the largest known pyroclastic deposit in the solar system. Outgassing of volatiles such as CO2 and H2O from the MFF would have substantially contributed to the Martian atmosphere and hydrosphere. [ABSTRACT FROM AUTHOR]

Recent work is changing our understanding of phreatomagmatic maar-diatreme eruptions and resulting deposits. In previous models, explosions were often inferred to take place only at the base of a diatreme, with progressive downward migration due to a cone of depression in the host aquifer. However, diatremes themselves contain much water that is heterogeneously distributed, and field evidence supports the existence of explosion sites at many vertical and lateral locations within them. Crater sizes have been used to estimate explosion energies, but this only works for single-explosion craters where the depth of explosion is independently known, and has limited value for multi-explosion maar-diatremes. Deep-seated lithic clasts in tephra ring beds have been taken to indicate the depth of the explosion that produced that bed. However, only relatively shallow explosions actually vent to the surface, and deep-seated lithics are gradually brought to shallow depths through step-wise mixing of multiple subsurface explosions. Grain-size of tephra-ring deposits is often inferred to indicate fragmentation efficiency. However, other factors strongly influence deposit grain size, including the scaled depth of an explosion and the interaction of an erupting jet with topography around a vent (e.g., crater), along with long recognized effects of mechanical properties of host rocks and recycling within the vent/diatreme. These insights provide a foundation for future research into this important volcano type.

Abstract: Pyroclastic density currents (PDCs) are a significant volcanic hazard. However, their dominant transport mechanisms remain poorly understood, in part because of the large variability of PDC types and deposits. Here we combine field data with experimental and numerical simulations to illuminate the twofold fate of particles settling from an ash cloud to form the dense PDC basal flow. At solid fractions >1 vol %, heterogeneous drag leads to formation of mesoscale particle clusters that favor rapid particle settling and result in a mobile dense layer with significant bed weight support. Conversely, at lower concentrations the absence of particle clusters typically leads to formation of poorly mobile dense beds that deposit massive layers. Based on this transport dichotomy, we present a numerical dense‐dilute parameter that allows a PDC's dominant transport mechanism to be determined directly from the deposit geometry and grainsize characteristics. [ABSTRACT FROM AUTHOR]

To better understand the alteration of volcanic ash in different depositional environments, we measured the clay mineralogy, major and trace element geochemistry, and Sr and Nd isotopic composition of altered ashes in two Permian-Triassic boundary (PTB) successions in southern China. The Pengda and Xinmin sections, in Guizhou Province, represent different depositional settings, allowing us to investigate the role of the early burial environment on authigenic clay formation. The PTB ash beds in both sections consist predominantly of mixed-layer illite-smectite clays. Altered ashes in the relatively shallow Pengda section contain predominantly R2 and R3 I/S clays, with 70% to 85% illite layers, whereas their stratigraphic equivalents in the deeper Xinmin section contain only R3 I/S clays, which are of two types, with 88% and 99% illite layers, respectively. The two studied ash beds can be stratigraphically correlated between the Pengda and Xinmin sections, and show similar 143 Nd/ 144 Nd ratios (0.511991 for PD-1 and 0.511983 for XM-1; 0.512073 for PD-2 and 0.512074 for XM-2). REE distributions and immobile element cross plots are consistent in suggesting that the altered ashes may have originated via felsic volcanism. Altered ashes in the deep sea Xinmin section have notably high 87 Sr/ 86 Sr ratios (0.764209 and 0.795921) relative to those from equivalent horizons in shallower environments (0.728455 and 0.749953). This difference in 87 Sr/ 86 Sr ratios is likely attributable to different degrees of chemical weathering. Elemental ratios such as SiO 2 /Al 2 O 3 , K 2 O/Al 2 O 3 , Y/Sr and Zr/Sr all support more intensive chemical leaching in deep-water environments. The altered ashes at Xinmin contain substantially more K 2 O than those at Pengda, suggesting greater incorporation of K + into clay minerals due to lower pH during early diagenesis. Clay mineral assemblages and stacking structures of I/S clays in the altered ashes are consistent with a general sequence of smectite illitization during diagenesis and burial metamorphism in both sections. [ABSTRACT FROM AUTHOR]

The work presented here focuses on lobe shapes and clast populations within lobate termini of the 1993 pumice flow deposits at Lascar Volcano, Chile. A new method to analyze a coarse-tail grain size population with field photographs is presented. Using this method, > 33,000 (> 0.5 cm) clasts from the pumice lobes of the 1993 pumice flow deposits were measured at 36 sites, and the resultant grain size distributions were then related to lobe morphology. Lobe margins (i.e., levees, clefts, and snouts) were found to contain significantly larger pumice clasts and be more poorly sorted than lobe central channels (i.e., locations away from the margins). Previous laboratory experiments suggest lobe margins form by the floatation and deflection of larger clasts to the margins of an advancing flow lobe. Results here indicate that the same sorting process efficiently segregates clasts into two flow regimes: 1) a mobile central channel depleted in coarse clasts, and 2) friction-dominated margins enriched in clasts ≥ 15 cm. The lobe margins, 60% enriched in larger particles with matrix < 20%, slow and frictionally freeze from the base up and before the material in the central channel stops flowing. The advancing pumice lobes finally stop when the margins reach ~ 12 clasts thick and the central channel has insufficient mass flux or momentum to break through or over-top the static margins. These processes form a unique lobe and channel morphology deposit that is diagnostic of granular flow and typical of small to intermediate volume pumice flow emplacement. [ABSTRACT FROM AUTHOR]

Nearly forty years after the return of the first lunar samples to Earth, improvements in laboratory detection limits made possible the first definitive discovery of magmatic water in lunar volcanic samples. The intervening decade has seen an exponential increase in the amount of data on the abundance of magmatic water, and its hydrogen isotope composition, in various rock types recovered from the Moon. Here we review these data and describe how the abundance of water in the lunar interior places important constraints on models for the high-temperature origin and evolution of the Moon. [ABSTRACT FROM AUTHOR]

Salt crystallization is the most significant factor in the degradation of the natural stones used in cultural and historical structures. Stones decay partially or fully as a result of this exposure. This study is the investigation of the degradation of historical monuments (underground cities and semi-underground settlements) carved in pyroclastic rocks in Cappadocian Region which takes part in World Cultural Heritage List. Samples of pyroclastic rocks were collected from six different quarries in Cappadocia, Turkey. To understand the contribution of salt crystallization to this weathering, dry weight loss (DWL) tests were performed on these samples. To investigate the correlations between salt crystallization and other rock properties, porosity, water absorption, ultrasonic velocity, uniaxial compressive strength, Brazilian tensile strength, and point load index were also measured. During the SC process of weathering, the results showed that porosity and water absorption increased for all the samples whereas ultrasonic velocity, uniaxial compressive strength, tensile strength, and point load index values decreased. Evaluation of the data obtained from these tests showed very high logarithmic correlations between the dry weight loss values and the mechanical properties. [ABSTRACT FROM AUTHOR]

Either directly or indirectly, building stone is exposed to diverse atmospheric interactions depending on the seasonal conditions. Due to those interactions, objects of historic and cultural heritage, as well as modern buildings, partially or completely deteriorate. Among processes involved in rock deterioration, the freeze–thaw (F–T) cycle is one of the most important. Even though pyroclastic rocks have been used as building stone worldwide due to their easy workability, they are the building stone most affected by the F-T cycle. A historical region in Central Anatolia, Turkey, Cappadoia encompasses exceptional natural wonders characterized by fairy chimneys and unique historical and cultural heritage. Human-created caves, places of worship and houses have been dug into the pyroclastic rocks, which have in turn been used in architectural construction as building stone. Using 10 pyroclastic rock samples collected from Cappadocia, we determined the rock’s index-mechanical properties to develop a statistical model for estimating percentage loss of uniaxial compressive strength a critical parameter of F-T cycle’s important value. We used dry density (ρ d ), ultrasonic velocity (V p ), point load strengths (I S(50) ), and slake-durability test indexes (I d4 ) values of unweathered rocks in our model, which is highly reliable ( R 2 = 0.84 ) for predetermination of percentage loss of uniaxial compressive strengths of pyroclastic rocks without requiring any F-T tests. [ABSTRACT FROM AUTHOR]

Hydrated halloysite was discovered in books, a morphology previously associated exclusively with kaolinite. From ∼1.5 to ∼1500 μm in length, the books showed significantly greater mean Fe contents (Fe2O3 = 5.2 wt.%) than tubes (Fe2O3 = 3.2 wt.%), and expanded rapidly with formamide. They occurred, along with halloysite tubes, spheroids and plates, in highly porous yet poorly permeable, silt-dominated, Si-rich, pumiceous rhyolitic tephra deposits aged ∼0.93 Ma (Te Puna tephra) and ∼0.27 Ma (Te Ranga tephra) at three sites ∼10-20 m stratigraphically below the modern landsurface in the Tauranga area, eastern North Island, New Zealand. The book-bearing tephras were at or near saturation, but have experienced intermittent partial drying, favouring the proposed changes: solubilized volcanic glass + plagioclase→halloysite spheroids→halloysite tubes→halloysite plates→ halloysite books. Unlike parallel studies elsewhere involving both halloysite and kaolinite, kaolinite has not formed in Tauranga presumably because the low permeability ensures that the sites largely remain locally wet so that the halloysite books are metastable. An implication of the discovery is that some halloysite books in similar settings may have been misidentified previously as kaolinite. [ABSTRACT FROM AUTHOR]

Ulaş district of the Sivas province is Yeşildiyar (İtkıran) of the village, 1, 5 km southwest of the village, there are two closed depressions. These depressions are aligned northeast-southwest direction which located in watershed between the Kızılırmak River Basin and Karasu (Fırat) River Basin. Tepegöl I is in the northeast depression, 900 m mouth diameter, bottom diameter 400 metres and has a depth of approximately 130 m. The lake called Tepegöl is located at the base of the depression. The rest of the base is covered with alluvial deposit. Floor level elevation of Tepegöl II is 1851 m and a base diameter of 450 metres and the diameter of the mouth portion 250 meters. The depth of this depression having a circular shape is about 85 meters. It is 60 meters higher than the bottom of the depression in the northeast. These depressions have typical features of maar structures. Pyroclastics are disseminated due to severe gas pressure and deposited as concentric layers with slopes toward outside. Pyroclastics has a thickness of more than 30 metres. Pyroclastic material was partially destroyed as a result of erosive activities. Ophiolitic formation of the base of the rock fragments is observed in layered pyroclastics. Maars have probably occurred in the Plio-Quaternary. Depressions are developed in control of the left lateral strike-slip fault. The Tepegöl Lake, 1791 meters high above sea level, is typically a maar lake. [ABSTRACT FROM AUTHOR]

Maar–diatreme volcanoes in their simplest form are thought to result primarily from discrete, subsurface phreatomagmatic explosions. Tephra ring deposits around maar craters are commonly interpreted in terms of a framework wherein explosions begin at shallow levels and migrate downward, ejecting progressively deeper-seated lithic clasts that contribute to the tephra rings. Additionally, variations in grain size of the deposits are sometimes inferred to record different degrees of fragmentation, which are in turn related to variations in magma–water ratios at the explosion sites. Recent detailed studies of diatremes and of maar tephra rings suggest a different conceptual model wherein explosions can happen at various vertical and lateral locations within a diatreme during its eruptive lifetime, rather than being limited to simple downward migration. Experiments, numerical modeling, and field data indicate that most explosions deeper than about 200–250 m will not vent to the surface, but instead contribute to mixing within the diatremes. Arrival of deep-seated lithics at the surface is related to this mixing process. Experiments also indicate that explosion phenomena can result in a range of emplacement mechanisms and grain sizes in tephra rings, even in the absence of variations in explosion mechanisms (fragmentation efficiency). Here we document the tephra ring of Stracciacappa maar (central Italy), and interpret its eruption and emplacement history in terms of evolving conceptual models along with a comparison to more traditional interpretations. Because most elements of both conceptual models are viable, the work points to an important need to develop criteria to distinguish between the various inferred mechanisms. [ABSTRACT FROM AUTHOR]