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The islands of Sumatra and Sinabung are located southwest of the Sundaland Continent which is a convergence route between the Indian-Australian Plate that infiltrates to the west of the Eurasian/Sundaland Plate. The increase in activity of Mount Sinabung was preceded by large earthquakes to the west and south while the eruption of Mount Sinabung produced pyroclastics. The purpose of this study is to find out the analysis of coulomb stress from the Sumatra Island earthquake to the pyroclastic flow of Sinabung as data on volcanic disasters. This study used the coulomb stress method with coulomb 3.3. The earthquake data analyzed was Mw, depth, and focal mechanism. The results of the analysis in the form of the direction of the spread of stress and the value of increased coulomb stress in Sinabung in 2014-2016. Sinabung's positive stress coulomb value in 2014 was 0.113 bar with a positive coulomb stress spread angle of 90oagainst sinabung pyroclastic flow. Sinabung's positive stress coulomb value in 2015 was 0.235 bar with a positive coulomb stress spread angle of 90oagainst sinabung pyroclastic flow. Sinabung's positive stress coulomb value in 2016 was 0.118 bar with a positive coulomb stress spread angle of 90oagainst sinabung pyroclastic flow. Coulomb stress analysis affects the direction of prioclastic flow by as far as 180oalthough it is not the same as the results in the field. This is because the peak of Sinabung has landslides in the southeast-south, thus opening a pyroclastic flow road to the southeast-south.

The Lechmine N'kettane is a Quaternary volcano, located within the Middle Atlas Volcanic Field (MAVF) in central Morocco. It is built on the faulted contact between Liassic limestone and Plio-Quaternary fluvio-lacustrine deposits. In map-view it consists of an elliptical maar crater, surrounded by a tephra ring, within which a scoria cone is nested in its northern crater zone. The Lechmine N'Kettane volcano is monogenetic in the sense of its small eruptive product volume and lack of evidence of significant time breakthrough it grows. The volcano formed from an eruptive locus that migrated laterally and vertically within the short duration of the eruption in a zigzagging pattern, along a complex set of generally NE-SW and NW-SE-trending faults. It represents a perfect example of how a volcano form and evolve under the influence of a combination of specific factors such as the lithological characteristics of the substrate, its hydrogeological parameters, magma flux and the local structural framework of the country rocks. The petrographic, granulometric and morphological (including terrain modelling) analyses of the Lechmine N'kettane pyroclastic deposits show that it was constructed in four eruptive phases with variable eruptive styles. The first, relatively dry, phreatomagmatic phase, that took place on a NE-SW fault in the northeastern part of the crater, was generated by the interaction between the ascending basaltic magma with meteoric water in the karst aquifer hosted by the Liassic limestone. The second phase is represented by a magmatic scoria fallout deposit whose explosion locus moved westward, along the same NE-SW fault. During the third phase, the explosion center migrated southward, along a NNW-SSE fault, and produced the last phreatomagmatic event by interaction of magma and water-saturated Plio-Quaternary sediment. The fourth eruptive phase is a purely scoria event, corresponding to the construction of the nephelinitic scoria cone in the northwestern part of the tephra ring. Between eruptive products formed in respective eruptive phases no evidence was recognized to establish significant time gaps between their formation. published

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/m 2 . In the pyroclastic unaffected areas, were found 33 species and an abundance of 3865 individuals/m 2 . 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.

Volcanic pyroclastic deposits generally have a metastable and collapsible structure, which may lead to their liquefaction under monotonic, cyclic, and dynamic loading. Their structure could be partly attributed to the nature of the pyroclastic particles, especially their lightweight, fragile and porous features. In comparing the results of monotonic and cyclic undrained triaxial tests performed on Cervinara soil, the steady-state concept is used to define the occurrence of liquefaction. A significant part of the experimental program on Rangiriri soil is carried out to highlight the role of the fragility of pyroclastic particles on the occurrence of liquefaction. The comparison between the results obtained on the two types of pyroclastic soils shows the possibility of explaining the undrained mechanism of pore pressure buildup using the state parameter ψ. The parameter ψ seems to be useful also in comparing the results obtained on pyroclastic soils with those on ordinary sands. The state parameter has a clear physical significance that could be used to define a more reliable model of undrained pore pressure buildup for soils of different natures. © 2021 American Society of Civil Engineers.

International audience; Explosive volcanic vents are widespread on Mercury. Compound volcanic vents comprise multiple individual vents, and probably formed through multiple events. We demonstrate that ~70% of the volcanic vent sites on Mercury that have been imaged with sufficient resolution to resolve their internal features are compound vents that have probably undergone multiple eruptions. Interior characteristics of compound vents, such as crosscutting relationships, contrasts in small scale impact cratering, and other textural detail, as well as the asymmetry of surrounding faculae, suggest that activity occurred over a prolonged but so far unquantified period of time. We use multiple case studies to highlight the migration of eruption centres at these sites. At the Nathair Facula vent, small-scale interior pits suggest the location of the most recent activity.

Zircon is a main mineral used for dating rhyolitic magmas as well as reconstructing their differentiation. It is common that different populations of zircon grains occur in a single rhyolitic sample. The presence of both autocrystic and antecrystic zircon grains is reflected in their strongly varied chemical compositions and slight spread of ages. However, postmagmatic processes may induce lead loss, which is also recorded as a spread of zircon ages. Therefore, new approaches to identify different zircon populations in rhyolitic rocks are needed. In this study, we suggest that detailed examination of zircon positions in the thin sections of rhyolitic rocks provides valuable information on zircon sources that can be used to identify autocrystic and antecrystic zircon populations. Automated Scanning Electron Microscope (SEM) analyses are of great applicability in determining this, as they return both qualitative and quantitative information and allow for quick comparisons between different rhyolite localities. Five localities of Permo-Carboniferous rhyolites related to post-Variscan extension in Central Europe (Organy, Bieberstein, Halle, Chemnitz, Krucze) were analyzed by automated SEM (MLA-SEM). The samples covered a range of Zr whole rock contents and displayed both crystalline and glassy groundmass. Surprisingly, each locality seemed to have its own special zircon fingerprint. Based on comparisons of whole rocks, modal composition and SEM images Chemnitz ignimbrite was interpreted as containing mostly (or fully) antecrystic zircon, whereas the Bieberstein dyke was shown to possibly contain both types, with the antecrystic zircon being associated with disturbed cumulates. On the other hand, Organy was probably dominated by autocrystic zircon, and Krucze contained dismembered, subhedral zircon in its matrix, whereas Halle zircon was located partly in late veins, filling cracks in laccolith. Both localities may, therefore, contain zircon populations that represent later stages than the crystallization of the main rhyolitic body.

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.

Two of the largest known historic block-and-ash flow (BAF) fields are located on Shiveluch volcano, Kamchatka. The deposits were produced during retrogressive and pulsatory dome collapse events that occurred over 6-9 hour-long eruptions on 27-28 February 2005 and 27 October 2010. The BAFs that were produced by these partial dome collapse events extend up to 19 km from the dome and inundate areas of 24.1 and 22.3 km2. We used satellite and field data to investigate the surface morphology of the BAF deposits and their impact on the surrounding area. The deposit surfaces contain overlapping lobate deposits, compaction ridges, levees and channel morphologies, degassing structures, abundant large dome blocks, and large areas of syn- or immediately-post-depositional remobilization, as shown by bench scallops and arcuate scarps. The dome-collapse events produced flows with two components: the dense block-and-ash component of the flows, and the associated dilute pyroclastic surges. The surge components traveled beyond the main flow and killed vegetation to distances of nearly 300 m. The 2005 dome collapse event produced a BAF that extended 17.8 km from the dome and emplaced a large fan deposit and associated surge, which destroyed an area of forest 10 km2 in size. The October 2010 event also produced a large fan deposit with a distal channelized deposit that extended an additional 5.4 km beyond the main 2010 fan for a total distance from the dome of 19 km. Since deposition, fluvial erosion and deposition produced large areas comprised of dendritic and braided channel deposits. The surface morphology of the deposits as revealed in satellite imagery and observed in stratigraphic sections give insight into the pulsatory nature of the dome collapse events, the final moments of deposition, and the subsequent erosion of the deposits. Preservation of the deposits is exceptional due to the high-latitude location, where snow-cover is present for much of the year and erosion is limited. This detailed study of the Shiveluch deposits provides rare insight into the processes responsible for generation of large and long run-out dome-collapse BAFs in both channelized and non-channelized environments.

The 26 October-23 November 2010, eruption is Merapi's largest event (VEI 4) over the past 140 years. We tracked and identified the 2010 Merapi's PDC deposits in the most impacted catchment (South) using high-resolution optical (from GeoEye and SPOT-5 satellites as well as low altitude photograph) imagery. We show that high-resolution imagery enables mapping with unprecedented detail the effects of the 2010 eruption in the summit area and across the most devastated catchment on Merapi. We investigated the relationships between the morphology of the river channel, and the apparent behavior of the PDCs and lahars, as deduced from over-banking processes. The 2010 pyroclastic deposits cover an area of ∼27 km2 in the Gendol-Opak catchment, i.e. 35% of the total deposit area. We analyze how unconfined PDCs with over-bank and veneer facies, as well as two types of surges have mantled widespread areas on both sides of the Gendol valley which contain the confined PDC deposits. Geometric and geomorphic characteristics that allow over bank and veneer deposits beyond the main valley are: limited cross-sectional areas under 1500 m2 and the decreasing longitudinal rate of channel confinement. Subsequent lahars six months after the eruption have devastated several villages along the Gendol River 20km from the summit on the ring plain. Small areas down-valley was affected by over-bank lahars once pyroclastic deposits were remobilized 3.8km farther than the PDC front. The over-bank and avulsed lahars can be attributed to the limited capacity (200-250 m2) of river channels and meandering river (sinuosity index of 1.25) across the lowest-angle (

Field monitoring and laboratory results are presented for an unsaturated volcanic pyroclastic. The pyroclastic belongs to the latest plinian eruption of the Ilopango Caldera in the Metropolitan Area of San Salvador, and is constantly affected by intense erosion, collapse, slab failure, sand/silt/debris flowslide and debris avalanche during the rainy season or earthquakes. Being the flowslides more common but with smaller volume. During the research, preliminary results of rain threshold were obtained of flowslides, this was recorded with the TMS3 (a moisture sensor device using time domain transmission) installed in some slopes. TMS3 has been used before in biology, ecology and soil sciences, and for the first time was used for engineering geology in this research. This device uses electromagnetic waves to obtain moisture content of the soil and a calibration curve is necessary. With the behavior observed during this project is possible to conclude that not only climatic factors as rain quantity, temperature and evaporation are important into landslide susceptibility but also information of suction–moisture content, seepage, topography, weathering, ground deformation, vibrations, cracks, vegetation/roots and the presence of crust covering the surface are necessary to research in each site. Results of the field monitoring indicates that the presence of biological soil crusts a complex mosaic of soil, green algae, lichens, mosses, micro-fungi, cyanobacteria and other bacteria covering the slopes surface can protect somehow the steep slopes reducing the runoff process and mass wasting processes. The results obtained during the assessment will help explaining the mass wasting problems occurring in some pyroclastic soils and its possible use in mitigation works and early warning system.

International audience; We present the results of laboratory experiments on the behaviour of sustained, dense granular flows in a horizontal flume, in which high-gas pore pressure was maintained throughout the flow duration by continuous injection of gas through the flume base. The flows were fed by a sustained (0.5–30 s) supply of fine (75 ± 15 μm) particles from a hopper; the falling particles impacted an impingement surface at concentrations of ~3 to 45 %, where they densified rapidly to generate horizontally moving, dense granular flows. When the gas supplied through the flume base was below the minimum fluidization velocity of the particles (i.e. aerated flow conditions), three flow phases were identified: (i) an initial dilute spray of particles travelling at 1–2 m s−1, followed by (ii) a dense granular flow travelling at 0.5–1 m s−1, then by (iii) sustained aggradation of the deposit by a prolonged succession of thin flow pulses. The maximum runout of the phase 2 flow was linearly dependent on the initial mass flux, and the frontal velocity had a square-root dependence on mass flux. The frontal propagation speed during phase 3 had a linear relationship with mass flux. The total mass of particles released had no significant control on either flow velocity or runout in any of the phases. High-frequency flow unsteadiness during phase 3 generated deposit architectures with progradational and retrogradational packages and multiple internal erosive contacts. When the gas supplied through the flume base was equal to the minimum fluidization velocity of the particles (i.e. fluidized flow conditions), the flows remained within phase 2 for their entire runout, no deposit formed and the particles ran off the end of the flume. Sustained granular flows differ significantly from instantaneous flows generated by lock-exchange mechanisms, in that the sustained flows generate (by prolonged progressive aggradation) deposits that are much thicker than the flowing layer of particles at any given moment. The experiments offer a first attempt to investigate the physics of the sustained pyroclastic flows that generate thick, voluminous ignimbrites.

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2012, Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2012, İnceleme alanı Balıkesir iline bağlı Kepsut ilçesi ve çevresini kapsamaktadır. Bu çalışma ile inceleme alanında yüzeyleyen ve Kepsut volkanitleri olarak adlandırılan volkanik kayaçların iç ayırtları yapılmış, birbiri ile ve çevre kayaçlarla ilişkileri saptanmış, petrografik ve jeokimyasal (ana-iz element ve Sr-Nd izotop) özellikleri incelenmiştir. Bu veriler birlikte değerlendirilerek KB Anadolu’nun bu kesiminde magmatizmanın nasıl bir evrim geçirdiği ortaya konulmaya çalışılmıştır. Kepsut ilçesi ve çevresinde yaklaşık 160 km2’lik bir yayılıma sahip olan çalışma alanın içinde başlıca 4 kaya topluluğu yer almaktadır. Bunlar yaşlıdan gence doğru; a) Temel kayaları b) Kepsut Volkanitleri ve c) Çökel Topluluk d) Alüvyon’dur. Temel kayaları amfibolit-yeşilşist fasiyesinde metamorfizmaya uğramış Sakarya kıtaına ait Kara kaya kompleksi birimlerinden Nilüfer birimi ile temsil edilir. Erken Miyosen yaşlı Kepsut volkanitleri ve Çökel Topluluk temel kayalarını uyumsuzlukla örtmektedir. Kepsut volkanitleri andezit-bazaltik andezit ve dasit-riyolit bileşimli lavlar ve bunlarla ilişkili piroklastik kayaçlardan oluşur. Kepsut volkanitlerini oluşturan Andezit –bazaltik andezit grubu lavların çıkış merkezi Eyüpbükü civarında saptanan bir strato-volkandır. Dasit-Riyolit domları ise bu strato-volkanın çevresinde KB-GD ve KD-GB yönünde dizilmiş (kırık erüpsiyonları) domlarla ilişkilidir. Kepsut volkanitleri pliniyen-sub pliniyen türü patlamalarla üretilmiştir. Farklı volkanik grupları temsil eden kaya örneklerinden elde edilen ana-iz element ve Sr-Nd izotop verileri Kepsut volkanitlerinin zenginleşmiş manto kaynağından türemiş, kıta kabuğundan kirlenmiş melez bir bileşime sahip olduğuna işaret etmektedir. Melez bileşimli bu magma asimilasyon ve buna eşlik eden fraksiyonel kristallenme (AFC) yolu ile evrimleşerek bazaltik andezitten riyolite değişen bileşimdeki lavları oluşturmuştur. İnceleme alanında yer alan gerek felsik (dasit-riyolit grubu) gerekse ortaç-mafik (andezit-bazaltik andezit grubu) lavlar ortak kökenlidir ve Batı Anadolu çarpışma sonrası (post collisional) magmatizmasının ürünlerini temsil etmektedir., This study presents a detailed geology map, volcanic stratigraphy and major-trace element geochemistry (combined with Sr-Nd-Pb isotope compositions) of Kepsut volcanites exposed in and around the Kepsut town of Balıkesir. In Kepsut (Balıkesir) and surroundings four main rock groups are distinguished. These are from bottom to the top as follows; a) Basement rocks b) Kepsut volcanites and c)Sedimentary association d)Alluvion Kepsut volcanites have two main rock groups; andezite-basaltic andezit lavas and associated pyroclastic rocks and dacite-rhyolite lavas and related pyroclastic rocks. Petrographically, they display hemicrystalline porphritic texture. Andesite-basaltic andesite group shows hyalopilitic, pilotaxitic, intersertal, glameroporiphiric, trachytic textures, Dacite-rhyolite lavad have generally hyalopilitic and vitrophyric texture and as a consequence of devitrification, spherulitic texture was mainly found. The relationships between these volcano-stratigraphic groups and their areal distributions in the study area indicate that the Kepsut volcanites were produced by plinian-sub-plinian eruptions of strato volcanoes and small vents aligned along NW-SE and NE-SW around this strato volcano. Kepsut volcanites, geochemically, are basaltic andesite, andesite, dacite and rhyolitic in composition that is consistent with petrographical investigations on same samples. The studied volcanic rock samples are subalkaline and generally calc-alkaline in character. . Both andesite-basaltic andesite and dacite-rhyolite groups belonging to Kepsut volcanites have similar major-trace element characteristics and Sr-Nd-Pb isotope compositions indicating that they are co-genetic and were originated from a common magma. The Sr-Nd isotopic signatures and trace element characteristics of volcanic association indicate that the Kepsut volcanites originated from a hybrid magma which was derived from enriched lithospheric mantle and was contaminated by the continental crustal components. The compositional variations observed in these granitoids are interpreted as a result of open system processes (AFC) rather than a reflection of closed system processes (FC). New major-trace element geochemical data and Sr-Nd isotope compositions obtained from this study and geology of the study area together with regional correlations are in good agreement with enriched-mantle derived and crustally contaminated magmas of post collisional tectonic setting., Yüksek Lisans, M.Sc.

The Sattasvaara komatiite complex is part of an extensive zone of explosive komatiitic volcanism which may have been a significant stage in the Lapponian evolution regarded as Archean. This volcanism took place at the latest 2.43 Ga ago and appears to have been connected with cratonic rifting in the Baltic Shield. The complex was formed by fissure eruptions rather than central-vent eruptions, at the margin of a restricted depositional basin. Effusive, explosive and mixed eruption phases were separated by erosional periods and the komatiitic volcanism was succeeded by mafic effusions and explosive eruptions. The Sattasvaara complex is composed of interchanging amphibole rocks, or komatiitic basalts, and amphibole-chlorite rocks or (basaltic)komatiites, and encloses minor serpentinitic and peridotitic rocks as terminal komatiite flows and picrite plugs. However, main part of the komatiites has discharged earlier and is present as intercalations in graphitic slate zone beneath the Sattasvaara complex. The komatiitic rocks were originally co-magmatic according to their gradual rock suite. The komatiitic basalt (MgO 9‒18 wt.% anhydrous basis) shows signs of fractional crystallization of pyroxene and plagioclase, whereas the (basaltic) komatiite (MgO 18‒29 wt.% anhydrous basis) contains pyroxene and olivine phenocrysts and the komatiite (MgO>29 wt.% anhydrous basis) is olivine-pyroxene cumulate both in distinct flows and lower parts of the (basaltic)komatiite flows. The erupting lavas differed physically and discharged in unlike manner: eruptions of the fluid komatiitic basalt were Hawaiian-type and the ones of the viscous (basaltic)komatiite were Strombolian-type. The initial komatiite flows were most fluidal and flowed after the manner of flood eruptions. Pyroclasticity is associated with the (basaltic)komatiite that is dominantly fragmentary, consisting of lithic, vitric and crystal ejecta; subordinate lava flows are largely block lavas. The voluminous explosive eruptions appear to have been magmatic in origin. Also, a minor pyroclastic breccia is formed by the komatiitic basalt that is usually present in massive or pillowed lava flows; these exceptional volcanic explosions have possibly caused by hydromagmatic eruptions. The komatiitic rocks may have been source of the gold contained in chromian marbles and quartzite-conglomerates nearby the Sattasvaara complex and the komatiitic volcanism seems to have caused iron-manganoferrous emanations in its periphery.