Mode Of Eruption Research Articles

Dynamics of gas-driven eruption on Ceres as a probe to its interior

The mineralogy of localized bright deposits on Ceres observed by the DAWN mission suggests their brine-enriched cryovolcanic origin. Based on the morphological observations of these deposits, explosive and effusive styles have been proposed for their eruption. Because volcanic eruption style and velocity are controlled by the extent of gas expansion inside the conduit, constraints on the internal aqueous environment, such as gas concentration and temperature, could be placed based on the observations of localized deposits on Ceres. However, the way these properties control the eruption style and velocity is complex. Cryomagma ascending from a subsurface reservoir gains buoyancy due to both boiling of water and exsolution of dissolved gas, owing to decompression to the extremely low pressure near the Ceres surface. Gas–melt segregation should also affect the dynamics. Thus, it is not yet fully understood how the internal environment of Ceres affects the ascent dynamics of cryovolcanism and subsequently controls the styles (explosive versus effusive) and velocities of eruptions. To address this problem, we developed a one-dimensional steady-state two-phase flow model for the ascent dynamics of gas-driven cryomagma under the conditions of Ceres taking both water boiling and gas exsolution into account. We found that the velocity and explosivity of an eruption are strongly controlled by the following three parameters, which characterize the cryomagmatic environment of Ceres's interior: (a) conduit conductivity (CC; rc2/μ, where rc is the conduit radius and μ is the magma viscosity), (b) dissolved gas concentration c0, and (c) magma reservoir temperature T0. Our model results reveal that low CC always leads to effusive or low-explosivity eruptions. Higher CC allows explosive eruption when either c0 or T0 is sufficiently high. These dependences can be summarized as four modes of eruption under the following CC-c0-T0 conditions. (1) Exsolution-driven explosive eruptions (X1 type) occur with volatile-rich magma (CC ≳ 10−3 m2/(Pa·s) and c0 ≳ 0.1 wt% of CO2). (2) Boiling-driven explosive eruptions (X2 type) occur with warm magma (CC ≳ 10−3 m2/(Pa·s), c0 ≪ 0.1 wt% of CO2, and high T0). (3) Viscosity-induced effusive eruptions (F1 type) occur with a narrow conduit and/or high-viscosity magma (CC ≲ 10−3 m2/(Pa·s)). (4) Low-gas-production-induced effusive eruptions (F2 type) occur with low-temperature and low-volatile magma (CC ≳ 10−3 m2/(Pa·s), c0 ≪ 0.1 wt% of CO2, and low T0). Our model predicts that either c0 ≳ 0.5 wt% of CO2 or T0 ≳−5°C is required for explosive eruptions to achieve eruption velocities ≳30 m/s, which has been proposed based on the size of some large faculae on Ceres. Such gas-rich or warm magma condition is unlikely to be achieved by equilibrium within the shallow crust. Thus, our results suggest that magma needs to be supplied from a deeper subsurface. In contrast, low-velocity effusion of brines has also been proposed based on morphometric analyses of evaporites on Ceres. Our results show that magma of such brine effusions is viscous and transported to the surface through a narrow conduit or they are sourced from reservoirs equilibrated to the ambient material within the shallow crust. Because the effusive eruption origin of faculae in the Occator crater is consistent with small conduits, the effusive nature may not necessarily rule out relatively high-volatile or warm magma inside Ceres in the recent past. These results show that the morphometric properties of facula deposits can place important constraints on the internal conditions of Ceres when the relevant eruption style/velocity is known. Our modeling results indicate that detailed observations (e.g., vesicularity, cooling history, and inclusion of eroded conduit material) of deposits and the possible vent structure in faculae by landing missions allow us to further probe the interior conditions of Ceres (e.g., magma temperature, gas concentration, viscosity, and conduit size).

Analysis of Volcanic Development Model and Main Controlling Factors of Oil Distribution in the Third Member of Shahejie Formation in Zaoyuan Oilfield

In order to clarify the influence in the volcanic mode and structure on the oil reservoirs, the volcanic reservoir characteristics, volcanic eruption pattern, and volcanic eruption period of the third member of the Shahejie formation in the Dagang Oilfield Zao35 fault block are studied by combining logging, 3D seismic, and production data, and to provide geological basis for the subsequent development of volcanic reservoirs. The results show that the volcanic body of the Zao35 fault block is jointly controlled by the fissure-centered eruption mode, and there are three strings of bead-shaped eruption centers as well as a fault overflow channel. Based on the seismic response characteristics, the volcanic rocks can be divided into three main eruption cycles. Moreover, combined with the relatively stable mudstone interlayer encountered by the single well, it can be further divided into eight volcanic eruption periods. There are three different lava units in the overflow facies of each stage, namely thick layer dense basalt, basalt with pores developed at the top and dense at the bottom, and basalt with pores developed at the top and dense in the middle. Influenced by the volcanic development model, the oil is mainly distributed in the volcanic reservoir on the slope belt between the central eruption and the fracture eruption. Affected by volcanic eruption periods, the pore basalt at the top and bottom of each period controls the distribution of the oil reserves. Therefore, the thick layer stomatal basalt located between the two eruption modes is the key target of the next development.

Study on the Identification Method of Pyrogenetic Rock Based on N -DP Intersection Graph

Igneous rocks have the characteristics of “diversification of eruption mode, diversification of lithologic origin and multiple changes of mineral assemblages ", so it is difficult to identify fine. This study is based on a real case study of igneous carboniferous reservoir in Jinlong 10 block at Junggar basin. The distinguish of the reservoir-developed rocks are catalyzed to basalt, andesite, dacite, granite, tuff and volcanic breccia rock, based on a combination of core and thin sheet analysis data. Based on the characteristics of log response of different lithology, the basic basalt, neutral andesite and acidic granite are quickly distinguished by N-DP intersection map method, and the idea of “step by step stripping” is adopted in the interval, and tuff and volcanic breccia are identified by intersection map method. The results of lithology identification and the conclusion of core sheet analysis have a high degree of anastomosis, which effectively improves the accuracy of lithology identification.

A CO2-Driven Gas Lift Mechanism in Geyser Cycling (Uzon Caldera, Kamchatka)

Here, we report on a new geyser (named Shaman) formed in the Uzon caldera (Kronotsky Federal Nature Biosphere Reserve, Russia) in autumn 2008 from a cycling hot Na-Cl spring. The geyser is a pool-type CO2-gas lift driven. From 2012 to 2018, the geyser has shown a rather stable interval between eruptions (IBE) from 129 to 144 min with a fountain height up to 4 m, and the geyser conduit has gradually enlarged. In 2019, the Shaman geyser eruption mode significantly changed: cold water inflow from the adjacent stream was re-directed into the geyser conduit and the average IBE decreased to 80 min. We observed two eruptive modes: a cycling hot spring (June 2019) and a cycling geyser (after June 2019). Bottom-hole temperature recording was performed in the geyser conduit to understand its activity. The TOUGH2-EOS2 model was used to reproduce the obtained temperature records and estimate geyser recharge/discharge parameters in both modes. Modeling shows that a larger cold inflow into the conduit causes a switch from cycling geyser to hot cycling spring mode. It was also found that the switch to cycling geyser mode corresponds to a larger mass of CO2 release during the time of the eruption.

Characteristics of Mesoproterozoic Felsic Meta-Volcanics from the Shillong Group of Rocks, Meghalaya, North East India

Shillong Group comprises a thick meta-volcano-sedimentary sequence forming a part of Shillong Plateau and Mikir Hills. The litho variants of felsic meta-volcanics are characterized in detail based on their constituent material, textural variation, depositional feature and mode of eruption. Lava flows are characterized as porphyritic, spherulitic and aphyric type whereas pyroclastic deposits are classified as tuff breccia, lapilli tuff, tuffand ignimbrite. Fractured crystal and brecciated lithic fragments in tuff; fiamme and eutaxitic texture of ignimbrite suggest for subaerial eruption. The felsic meta-volcanics are rhyolitic to dacitic in composition and interbedded with tuffaceous phyllite, phyllite and quartzite.

Process Simulation of Carboniferous Volcanic in Jinlong Area, Junggar Basin

The Jinlong area is located in the northwestern margin of Junggar Basin. Volcanic is widely distributed in Carboniferous layers, showing well petroleum resources prospects. The distribution of volcanic reservoirs is obviously controlled by the distribution characteristics of volcanic lithofacies. Therefore, through the analysis of core observation, thin section identification, data of well logging and mud logging, and interpretation of seismic data, this paper studies process simulation of Carboniferous volcanic in the Jinlong area, which is located in the northwestern margin of Junggar Basin. Based on the characteristics of volcanic materials and comparison of profile facies, the paper restores distribution characteristics of lithofacies of Carboniferous in the study area: The study area mainly develops volcanic lithofacies such as effusive phase and explosive phase. The thickness between wells varies greatly, which is affected by eruption mode and fault development. The vertical and horizontal changes of lithofacies are discontinuous and the phase transformation is fast. The volcanic activity of Carboniferous gradually weakened. There are multiple volcanic eruption centers in each period, which are controlled by crack and distributed in beads. In addition, an intermediate-mafic composite volcanic-crack eruption edifice was developed in the southern zone of the study area. Because of strong tectonism in the area near the crater, there are many dissolvable components in volcanic, which can form favorable hydrocarbon reservoir bodies and become the most favorable target zone in the Jinlong area.

A shift in eruption mode of Hekla volcano, Iceland, 3000 years ago: two‐coloured Hekla tephra series, characteristics, dispersal and age

ABSTRACTHekla volcano is a major producer of large, widespread silicic tephras. About 3000 years ago, the dominant eruption mode shifted from infrequent large (>1 km3) to more frequent moderate (<1 km3) eruptions. In the following two millennia ≥20 explosive silicic‐to‐intermediate eruptions occurred, and six or more basaltic. Three categories can be identified with dacite/andesite to basaltic andesite in the oldest eruptions through basaltic andesite to basalt in the youngest eruptions. Ten tephra layers of the first category have distinct field characteristics: a pale lower unit and a dark upper unit (two coloured or TC‐layers). Colour separation is sharp indicating a stratified magma chamber origin. The lower unit is dominantly andesitic (61–63% SiO2), while the upper unit is basaltic andesite (53–57% SiO2). Volumes of the eight largest TC‐layers range from 0.2 to 0.7 km3 as freshly fallen. Radiocarbon and soil accumulation rate dates constrain the TC‐layers to between 3000 and 2200 years ago. Two of these (~2890 and ~2920 b2k) are likely to occur overseas. Low SiO2 in the last erupted tephra of the TC‐layers is comparable to that of historical Hekla lavas, implying a final effusive phase. The Hekla edifice may, consequently, be younger than 3000 years.

Clinopyroxene megacrysts from Marion Island, Antarctic Ocean: evidence for a late stage shallow origin

Clinopyroxene megacrysts (up to 5 cm) from a scoria cone on Marion Island, Antarctic Ocean are zoned, with compositionally distinct low (Al + Ti) and high (Al + Ti) patches arranged haphazardly throughout crystals. Inclusions of olivine, pyrrhotite, oxides, sulphides, and rounded inclusions with euhedral micro-crystals interpreted as former melt inclusions are observed. Olivine inclusions have variable compositions, ranging from primary Ti-poor crystals to Ti-rich crystals hosting secondary haematite crystals formed by hydrogenation. The crystals contain voids that are concentrated in the middle of each crystal indicating that the initial crystal growth was skeletal. Subsequent crystallisation filled in the skeletal framework creating the patchy zoning in the crystals. The Marion Island megacrysts are not homogenous, but the combination of crustal clinopyroxene compositions, primary and hydrogenated olivine, and the mode of eruption in scoria eruptions indicates that these crystals most likely formed in a shallow magma chamber. Primary olivines crystallised from a mafic magma and secondary altered olivines were incorporated into a rapidly growing megacryst in a super-saturated, fluid-rich environment, prior to being ejected onto surface in a scoria eruption.

25. 浅間山 1973 年活動における噴出物と噴火様式(その 1)(日本火山学会 1973 年度春季大会講演要旨)

25. 浅間山 1973 年活動における噴出物と噴火様式(その 1)(日本火山学会 1973 年度春季大会講演要旨)

Flow behavior of rapid thermal oscillation inside an asymmetric micro pulsating heat exchanger

This study has investigated the rapid thermal oscillatory flow in an asymmetric micro pulsating heat exchanger (MPHE). In the design and fabrication of the MPHE, a transparent acrylic plate was attached to the stainless steel plate on which 14 parallel rectangular channels were formed. As working fluids, FC-72 and ethanol were tested. The fluid inside the micro channel moves rapidly with pulsating motions by swelling and shrinking of liquid slug/gas plug at evaporation and condensation sections. By measuring the temperature variations from start-up to steady state operation, the effective thermal conductivities were evaluated. Since the filling ratio of working fluid plays an important role in heat exchanger efficiency, the optimum filling ratio was found for each working fluid. From the flow visualization inside the MPHE filled with FC-72, two different flow modes – oscillatory eruption mode and circulation mode – occurs according to the filling ratio. The circulating motion which occurs at the optimum filling ratio, helps the heat transfer into the cooling water more active than the oscillatory eruption mode.

Explosive volcanism on Mercury: Analysis of vent and deposit morphology and modes of eruption

The MESSENGER mission revealed, for the first time, conclusive evidence of explosive volcanism on Mercury. Several previous works have cataloged the appearance and location of explosive volcanism on the planet using a variety of identifying characteristics, including vent presence and deposit color as seen in multispectral image mosaics. We present here a comprehensive catalog of vents of likely volcanic origin; our classification scheme emphasizes vent morphology. We have analyzed the morphologies of all vents in our catalog, and recognize three main morphologies: “simple vent”, “pit vent”, and “vent-with-mound”. The majority of vents we identify are located within impact craters. The spatial distribution of vents does not correlate with the locations of volcanic smooth plains deposits, in contrast to the Moon, nor do vents correlate with the locations of large impact basins (except for the Caloris and Tolstoj basins). Using the degradation state of the vent host crater as a proxy for maximum age, we suggest that vent formation has been active through the Mansurian and into the Kuiperian periods, although the majority of vents were likely formed much earlier in mercurian history. The morphologies and locations of vents are used to investigate a set of plausible formation geometries. We find that the most likely and most prevalent formation geometry is that of a dike, stalled at depth, which then explosively vents to the surface. We compare the vent and deposit size of mercurian pyroclastic deposits with localized and regional lunar pyroclastic deposits, and find a range of possible eruption energies and corresponding variations in eruption style. Localized lunar pyroclastic deposits and the majority of mercurian pyroclastic deposits show evidence for eruption that is consistent with the magmatic foam at the top of a dike reaching a critical gas volume fraction. A subset of mercurian vents, including the prominent Copland-Rachmaninoff vent to the northeast of the Rachmaninoff basin, indicates eruption at enhanced gas volume fractions. This subset of vents shows a similar eruptive behavior to the lunar Orientale dark mantle ring deposit, suggesting that the dikes that formed these vents and deposits on Mercury underwent some form of additional volatile build-up either through crustal volatile incorporation or magma convection within the dike. There also exists a population of mercurian vents that no longer retain a visible associated pyroclastic deposit; we hypothesize that the visible signature of the pyroclastic deposit has been lost through space weathering and regolith mixing processes. Together, these results provide a comprehensive analysis of explosive volcanism on Mercury, and inform continued research on the thermal history of Mercury and magma composition and evolution.

Effusive silicic volcanism in the Paraná Magmatic Province, South Brazil: Physico-chemical conditions of storage and eruption and considerations on the rheological behavior during emplacement

Expressive occurrences of effusive deposits were identified in silicic units from the Paraná Magmatic Province outcropping in a key area in south Brazil where three units with different compositions occur (Caxias do Sul dacites, CSd, Barros Cassal andesites to dacites, BCs, and Santa Maria rhyolites, SMr). Textural and chemical characteristics of phenocrysts, microphenocrysts and microlites suggest that crystallization started in a shallow magma chamber and continued during ascent to the surface. These magmas had an unique character (e.g., very high temperatures ~1000°C and low H2O contents ~1–2wt%), and formed several types of deposits that are clearly indicative of locally fed lava flows and had physical properties consistent with this mode of eruption (e.g., viscosities as low as 104.2Pa·s at ca. 1000°C for the CSd). The very low estimated H2O contents are a consequence of their petrogenesis (i.e., fractionation from tholeiitic basalts plus assimilation of crustal melts from water-poor granitic sources), and was probably a key factor influencing the non-explosive nature of these deposits. The comparatively higher viscosity calculated for the Santa Maria rhyolite (>1–2 orders of magnitude greater than CSd) would make it a better candidate to generate expressive pyroclastic deposits, but this might be offset by its remarkably low H2O contents (≤1wt%) and low discharge ratios.

B2-08 新富士火山最近3000年間の噴火様式とマグマ含水量の関係(火山の岩石学1,口頭発表)

B2-08 新富士火山最近3000年間の噴火様式とマグマ含水量の関係(火山の岩石学1,口頭発表)

P24 黒曜岩片から見た鬼界アカホヤ噴火現象(日本火山学会2005年秋季大会)

P24 黒曜岩片から見た鬼界アカホヤ噴火現象(日本火山学会2005年秋季大会)

B1-05 西南日本,島根半島諸喰における水冷火山弾の産状と噴火様式(噴火ダイナミクス,口頭発表)

B1-05 西南日本,島根半島諸喰における水冷火山弾の産状と噴火様式(噴火ダイナミクス,口頭発表)

Caldera formation and varied eruption styles on North Pacific seamounts: the clastic lithofacies record

Detailed examination of volcaniclastic and sedimentary rocks collected from the Taney (30 Ma), President Jackson (4 Ma), Vance (3 Ma) and Alarcon (2 Ma) near-ridge seamount chains of the North Pacific reveals seven clastic lithofacies that record various modes of eruption, magma fragmentation, and particle dispersal. Lithofacies are distinguished by differences in lithology, bedding habit, compositional heterogeneity, and relationship to volcanic landforms. Breccia lithofacies were produced through mechanical fragmentation during caldera collapse (polymict) or effusive eruptions onto steep slopes (monomict). Rare globular lapilli mudstone lithofacies contain clasts with morphologies formed by magma-sediment mingling processes (peperite). Seamount summit pyroclastic deposits include proximal lapilli tuff with vesicular pyroclasts, and more distal limu o Pele tuff lithofacies. Much finer-grained hydrothermal mudstone/tuff lithofacies occurs around caldera rims and contains greenschist minerals, hydrothermal clays and basaltic ash that record subsurface phreatomagmatic fragmentation processes. Very fine-grained ash is transported to distal regions by oceanic currents and hydrothermal plumes, and is a component of the regional pelagic sediment budget. Pyroclastic lithofacies only occur on seamount summits suggesting formation during the latter stages of seamount evolution. As a seamount drifts away from an adjacent ridge axis and associated heat source, its magma supply is reduced allowing for magmatic gas buildup and mild explosive eruptions. During this stage, the diminished melt supply under the seamount is unable to fully compensate for extension along the ridge axis and vertical seamount growth. Lateral intrusion into spreading-related structures in this stage causes magma withdrawal and caldera formation. Formation of caldera ring faults also promotes seawater ingress into subseafloor hydrothermal cells, which interact with magma conduits causing phreatomagmatic fragmentation.

Cleidocranial dysplasia: maxillary alterations on the transverse plane. Presence of crown-radicular anomalies and multidisciplinary approach of a clinical case.

Cleidocranial Dysplasia (CCD) is a rare inherited autosomal dominant congenital syndrome that occurs in approximately one out of every one million individuals worldwide; it primarily affects bones that undergo intra-membranous ossification, generally the skull and clavicles. Other bones may be affected such as the long bones, spine, pelvis, bones of hands and feet showing hypoplasia of distal phalanges. Indispensable is the role of the gene Runx2, necessary for the differentiation of odontoblasts and osteoblasts; it regulates the expression of many genes related to the development of dental hard tissues. The aim of this study was to appraise the connection between the Cleidocranial Dysplasia and the appearance of skeletal and dental anomalies not much deepen to this day. With particular emphasis, it wants to describe the multidisciplinary therapeutic approach. The patient showed multiple skeletal features of CCD. A distinctive feature was the failed or delayed exfoliation of deciduous dentition and a delayed eruption of permanent teeth. The goal of the treatment is the improvement of both aesthetic and functional aspects. This objective can be achieved through an appropriate multidisciplinary treatment plan that arranges the orthodontic and surgical measures. Because of the involvement of facial bones, the altered mode of tooth eruption and the presence of numerous included supernumerary teeth, CCD is a pathology that all dentists should be familiar with. The patients have small faces compared to the skull and the hypoplasia of maxillary, tear, nasal and zygomatic bones. The orthodontic approach in literature seems to be reduced to the guided eruption of bad-positioned and impacted teeth. Knowledge of the clinical features of CCD allows for the early planning of the procedures necessary to resolve the dental pathologies observed in CCD patients.

P25 桜島大正噴出物中の硫化物の酸化反応 : 組織の多様性と噴火様式との関係について(ポスターセッション)

P25 桜島大正噴出物中の硫化物の酸化反応 : 組織の多様性と噴火様式との関係について(ポスターセッション)

The inception and progression of melting in a monogenetic eruption: Motukorea Volcano, the Auckland Volcanic Field, New Zealand

Compositional variation through basaltic monogenetic eruptive sequences provides a unique view into the processes and source heterogeneity of small-scale magmatic systems. A well-exposed, continuous sequence on Motukorea volcano in the Auckland Volcanic Field, New Zealand, consists of an early tuff ring, scoriaceous deposits and late lava flows which allow the evolution of the eruption to be studied at very high resolution. The deposits show a spectrum of basaltic compositions from Mg# 60 nephelinite (early tuff ring) to Mg# 70 alkalic basalt (lava). Within the deposits of each main eruptive phase (i.e. tuff, scoria and lava) very little variation is observed in major element chemistry, suggesting that fractional crystallisation has a limited effect. Systematic changes in trace element chemistry, however, are significant through the sequence. The major and trace element features observed through the sequence are inferred to be primarily due to the mixing of two magma batches, with a two-fold increase in the degree of melting between these. Variation in Pb-isotopic compositions up-sequence indicates subtle changes in mantle source with samples representing the start of the eruption displaying higher 207Pb/204Pb than the latter parts of the eruption. This chemical change coincides with a switch in the mode of eruption, with the arrival at the surface of magmas produced by larger degrees of partial melting resulting in the beginning of a more effusive eruption phase. The silica-undersaturated, high total alkali, low Al2O3 and higher 207Pb/204Pb nature of the samples from the tuff units suggests that these samples were produced by melting of relatively young eclogite domains. The lower 207Pb/204Pb, higher silica, lower total alkali nature of the samples from the scoria and lava reflects the exhaustion of these domains and the resultant melting of the surrounding garnet-peridotite matrix. This detailed study shows that the petrogenesis of small volcanic centres may be far more complex than their physical volcanology suggests.

Chemical and Isotopic Characteristics of the Kuroko‐Forming Volcanism

AbstractThe Miocene northeast Honshu magmatic arc, Japan, formed at a terrestrial continental margin via a stage of spreading in a back‐arc basin (23–17 Ma) followed by multiple stages of submarine rifting (19–13 Ma). The Kuroko deposits formed during this period, with most forming during the youngest rifting stage. The mode of magma eruption changed from submarine basalt lava flows during back‐arc basin spreading to submarine bimodal basalt lava flows and abundant rhyolitic effusive rocks during the rifting stage. The basalts produced during the stage of back‐arc basin spreading are geochemically similar to mid‐ocean ridge basalt, with a depleted Sr–Nd mantle source, whereas those produced during the rifting stage possess arc signatures with an enriched mantle source. The Nb/Zr ratios of the volcanic rocks show an increase over time, indicating a temporal increase in the fertility of the source. The Nb/Zr ratios are similar in basalts and rhyolites from a given rift zone, whereas the Nd isotopic compositions of the rhyolites are less radiogenic than those of the basalts. These data suggest that the rhyolites were derived from a basaltic magma via crystal fractionation and crustal assimilation. The rhyolites associated with the Kuroko deposits are aphyric and have higher concentrations of incompatible elements than do post‐Kuroko quartz‐phyric rhyolites. These observations suggest that the aphyric rhyolite magma was derived from a relatively deep magma chamber with strong fractional crystallization. Almost all of the Kuroko deposits formed in close temporal relation to the aphyric rhyolite indicating a genetic link between the Kuroko deposits and highly differentiated rhyolitic magma.