Sample records for pumice

  1. Pumice (United States)

    Whitham, A. G.; Sparks, R. S. J.


    Cold pumice floating on water slowly absorbs water into the vesicles and eventually sinks. Experiments show that some pumice can remain afloat for over 1 1/2 years. The time taken for enough water to be adsorbed to sink depends on the pumice size, initial density, the size distribution of vesicles and the connectedness of the vesicles. Hot pumice often sinks immediately on immersion in water despite having a lower density than water. Experiments demonstrate that for any pumice there is a critical temperature above which the pumice will sink. Even pumice with a density of 0.2 g/cm3 will sink if the temperature exceeds 700 °C. The critical temperature correlates well with initial pumice density with lower-density pumice requiring higher temperatures to sink. The mechanism at low temperatures (contraction of hot air within the pumice. However, at higher temperatures conversion of absorbed water to steam in the hot pumice flushes out air, and further cooling results in condensation and absorption of water into the pumice. The experiments on hot and cold pumice suggest that all the vesicles in pumice are interconnected. This was confirmed by vacuum impregnation of pumice with resins. The behaviour of hot and cold pumice indicates that the deposits of hot and cold pyroclastic flow deposits may be distinguishable. Hot deposits will contain a significant proportion of low-density pumice, whereas cold deposits will not. Pumice falling hot onto water could also sink immediately to form subaqueous pumice-fall deposits. The physical properties of pumice were further examined by a nitrogen absorption technique and by mercury porosimetry. The former method shows that pumice has a typical surface area of 0,5 m2/g, corresponding to a sheet of material of 1 m2 and 0,87 µm Thick. Porosimetry shows that there are often three apparent vesicle-size populations in pumice. However, the porosimetry data gives surface areas which often greatly exceed those measured by the absorption

  2. Pumice, pumicite review (United States)

    Crangle, R.D.


    The article focuses on the industrial mineral pumice. It mentions the estimated production of pumice in the U.S. in 2010, price range, and total U.S. exports and imports. Described as an igneous volcanic rock, pumice has low density which allows it float on water and porous enough to be used as building aggregate. Pumice may also function as an absorbent material, a filter aid, and a polishing agent among others.

  3. Trapped bubbles keep pumice afloat and gas diffusion makes pumice sink (United States)

    Fauria, Kristen E.; Manga, Michael; Wei, Zihan


    Pumice can float on water for months to years - long enough for pumice to travel across oceans and facilitate the spread of species. Long-lived pumice floatation is unexpected, however, because pumice pores are highly connected and water wets volcanic glass. As a result, observations of long floating times have not been reconciled with predictions of rapid sinking. We propose a mechanism to resolve this paradox - the trapping of gas bubbles by water within the pumice. Gas trapping refers to the isolation of gas by water within pore throats such that the gas becomes disconnected from the atmosphere and unable to escape. We use X-ray microtomography to image partially saturated pumice and demonstrate that non-condensable gas trapping occurs in both ambient temperature and hot (500 °C) pumice. Furthermore, we show that the size distribution of trapped gas clusters matches predictions of percolation theory. Finally, we propose that diffusion of trapped gas determines pumice floatation time. Experimental measurements of pumice floatation support a diffusion control on pumice buoyancy and we find that floatation time τ scales as τ ∝ L2/Dθ2 where L is the characteristic length of pumice, D is the gas-water diffusion coefficient, and θ is pumice water saturation. A mechanistic understanding of pumice floatation is a step towards understanding how pumice is partitioned into floating and sinking components and provides an estimate for the lifetime of pumice rafts in the ocean.

  4. Pumice aggregates for internal water curing

    DEFF Research Database (Denmark)

    Pietro, Lura; Bentz, Dale P.; Lange, David A.;


    water absorption, but they release a greater percentage of their absorbed water at the equilibrium relative humidity of practical interest in early-age concrete, above 90%. Additionally, early-age properties of mortars with different contents of saturated pumice were investigated: a reference mix...... without pumice and mixes with 4% and 8% pumice by volume of mortar. By addition of pumice, mortars with improved strength, enhanced degree of hydration and reduced autogenous shrinkage were obtained. An important obstacle to the application of this kind of pumice for actual concrete production...

  5. Stranded pumice in the western Caribbean (United States)

    Herrick, J. A.; Henton De Angelis, S.; Toscano, M. A.


    Floating and washed-up pumices have been reported by scientific expeditions along the Caribbean Sea coast of the Central American Isthmus and the northern coast of South America since at least 1947. Local coastal communities have been utilizing this resource for many years. The rounded and buffered morphology of hand specimens is consistent with water-borne transit. The volcanically active Caribbean and Central American regions provide a number of candidates for source volcanoes and eruptions. We have attempted to identify this source using samples collected from Carrie Bow Cay and Placencia Beach, Belize; Tulum Beach, Mexico; Morrosquillo Bay, Colombia; and Galeta Point, Panama. We have tracked possible transport routes through the use of river drainage and ocean current maps. The criteria for comparing the products of potential source volcanoes (including Atitlán Caldera in Guatemala and Caribbean sources such as Mt. Pelée, Martinique and Soufrière Hills, Montserrat) were developed from the whole rock major and trace element geochemistry and the compositional and textural characteristics of pumice and their constituent minerals and glasses. The largest pumice sample collected from Carrie Bow Cay, Belize, was 18.5x12 cm with the typical, rounded morphology and distinctively stretched vesicles exhibited by this pumice collection.

  6. Fluoride Adsorption by Pumice from Aqueous Solutions

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    Amir Hossein Mahvi


    Full Text Available Drinking water provides many vital elements for the human body, but the presence of some dissolved elements more than permissible concentration can endanger human health. Among the dissolved elements in drinking water, fluoride is noticeable, because both the very low or very high concentrations have adverse health impacts such as dental caries. Therefore, fluoride concentration should be kept in acceptable levels. In this study Pumice was used for fluoride removal. It was found that Fluoride sorption kinetic was fitted by pseudo-second-order model. The maximum sorption capacity of Pumice was found to be 13.51 mg/g at laboratory temperature (24°C. Maximum sorption study occurred at pH= 3. Results of Isotherm showed the fluoride sorption has been well fitted with Freundlich isotherm model. This study has demonstrated that Pumice can be used as effective adsorbents for fluoride removal from aqueous solutions. The adsorbent prepared in this study was cheap and efficient in removal of fluoride than other adsorbents.

  7. Effects of pumice mining on soil quality (United States)

    Cruz-Ruíz, A.; Cruz-Ruíz, E.; Vaca, R.; Del Aguila, P.; Lugo, J.


    Mexico is the world's fourth most important maize producer; hence, there is a need to maintain soil quality for sustainable production in the upcoming years. Pumice mining is a superficial operation that modifies large areas in central Mexico. The main aim was to assess the present state of agricultural soils differing in elapsed time since pumice mining (0-15 years) in a representative area of the Calimaya region in the State of Mexico. The study sites in 0, 1, 4, 10, and 15 year old reclaimed soils were compared with an adjacent undisturbed site. Our results indicate that gravimetric moisture content, water hold capacity, bulk density, available phosphorus, total nitrogen, soil organic carbon, microbial biomass carbon and phosphatase and urease activity were greatly impacted by disturbance. A general trend of recovery towards the undisturbed condition with reclamation age was found after disturbance, the recovery of soil total N being faster than soil organic C. The soil quality indicators were selected using principal component analysis (PCA), correlations and multiple linear regressions. The first three components gathered explain 76.4 % of the total variability. The obtained results revealed that the most appropriate indicators to diagnose the quality of the soils were urease, available phosphorus and bulk density and minor total nitrogen. According to linear score analysis and the additive index, the soils showed a recuperation starting from 4 years of pumice extraction.

  8. 76 FR 69700 - Klamath National Forest; California; Pumice Vegetation Management Project (United States)


    ... Forest Service Klamath National Forest; California; Pumice Vegetation Management Project AGENCY: Forest... the environmental effects of implementing the Pumice Vegetation Management project. The project is... Haupt, Pumice Vegetation Management Project Team Leader, Goosenest Ranger District, 37805 Highway 97...

  9. Effects of pumice mining on soil quality (United States)

    Cruz-Ruíz, A.; Cruz-Ruíz, E.; Vaca, R.; Del Aguila, P.; Lugo, J.


    México is the worl's fourth most important maize producer; hence, there is a need to maintain soil quality for a sustainable production in the upcoming years. Pumice mining, a superficial operation, modifies large areas in Central Mexico. The main aim was to assess the present state of agricultural soils differing in elapsed-time since pumice mining (0-15 years), in a representative area of the Calimaya region in the State of Mexico. The study sites in 0, 1, 4, 10 and 15 year-old reclaimed soils were compared with adjacent undisturbed site. Our results indicate that soil organic carbon, total nitrogen, microbial biomass carbon and microbial quotients were greatly impacted by disturbance. A general trend of recovery towards the undisturbed condition with reclamation age was found after disturbance. Recovery of soil total nitrogen was faster than soil organic carbon. Principal components analysis was applied. The first three components together explain 71.72 % of the total variability. First factor reveals strong associations between total nitrogen, microbial biomass carbon and pH. The second factor reveals high loading of urease and catalase. The obtained results revealed that the most appropriate indicators to diagnose the quality of the soils were: total nitrogen, microbial biomass carbon and soil organic carbon.

  10. Effects of pumice mining on soil quality

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    A. Cruz-Ruíz


    Full Text Available México is the worl's fourth most important maize producer; hence, there is a need to maintain soil quality for a sustainable production in the upcoming years. Pumice mining, a superficial operation, modifies large areas in Central Mexico. The main aim was to assess the present state of agricultural soils differing in elapsed-time since pumice mining (0–15 years, in a representative area of the Calimaya region in the State of Mexico. The study sites in 0, 1, 4, 10 and 15 year-old reclaimed soils were compared with adjacent undisturbed site. Our results indicate that soil organic carbon, total nitrogen, microbial biomass carbon and microbial quotients were greatly impacted by disturbance. A general trend of recovery towards the undisturbed condition with reclamation age was found after disturbance. Recovery of soil total nitrogen was faster than soil organic carbon. Principal components analysis was applied. The first three components together explain 71.72 % of the total variability. First factor reveals strong associations between total nitrogen, microbial biomass carbon and pH. The second factor reveals high loading of urease and catalase. The obtained results revealed that the most appropriate indicators to diagnose the quality of the soils were: total nitrogen, microbial biomass carbon and soil organic carbon.

  11. Usage of pumice as bulking agent in sewage sludge composting. (United States)

    Wu, Chuandong; Li, Weiguang; Wang, Ke; Li, Yunbei


    In this study, the impacts of reused and sucrose-decorated pumice as bulking agents on the composting of sewage sludge were evaluated in the lab-scale reactor. The variations of temperature, pH, NH3 and CO2 emission rate, moisture content (MC), volatile solid, dissolved organic carbon, C/N and the water absorption characteristics of pumice were detected during the 25days composting. The MC of pumice achieved 65.23% of the 24h water absorptivity within the first 2h at the mass ratio of 0.6:1 (pumice:sewage sludge). Reused pumice increased 23.68% of CO2 production and reduced 21.25% of NH3 emission. The sucrose-decorated pumice reduced 43.37% of nitrogen loss. These results suggested that adding pumice and sucrose-decorated pumice in sludge composting matrix could not only adjust the MC of materials, but also improve the degradation of organic matters and reduce nitrogen loss. Copyright © 2015 Elsevier Ltd. All rights reserved.


    Institute of Scientific and Technical Information of China (English)


    Electrorheological (ER) properties of polyaniline (Pani), pumice and polyaniline/pumice composites (PAPC) were investigated. Polyaniline and Pani/pumice composite were prepared by oxidative polymerization. Pani/pumice particlesbased ER suspensions were prepared in silicone oil (SO), and their ER behavior was investigated as a function of shear rate, electric field strength, concentration and temperature. Sedimentation stabilities of suspensions were determined. It has been found that ER activity of all the suspensions increases with increasing electric field strength, concentration and decreasing shear rate. It has shown that the suspensions have a typical shear thinning non-Newtonian viscoelastic behavior. Yield stress of composite suspensions increased linearly with increasing applied electric field strength and with concentrations of the particles. The effect of high temperature on ER activity of pumice/silicone oil systems was also investigated.

  13. Alkali-silica reaction resistant concrete using pumice blended cement (United States)

    Ramasamy, Uma

    Durability of structures is a major challenge for the building industry. One of the many types of concrete deterioration that can affect durability is alkali-silica reaction (ASR). ASR has been found in most types of concrete structures, including dams, bridges, pavements, and other structures that are 20 to 50 years old. The degradation mechanism of ASR produces a gel that significantly expands in the presence of water as supplied from the surrounding environment. This expansion gel product can create high stresses and cracking of the concrete, which can lead to other forms of degradation and expensive structural replacement costs. The four essential factors that produce an expansive ASR gel in concrete are the presence of alkalis, siliceous aggregate, moisture, and free calcium hydroxide (CH). If concrete is starved of any one of these essential components, the expansion can be prevented. Reducing CH through the use of a supplementary cementitious material (SCM) such as natural pozzolan pumice is the focus of this research. By using a pozzolan, the amount of CH is reduced with time based on the effectiveness of the pozzolan. Many pozzolans exist, but one such naturally occurring pozzolanic material is pumice. This research focuses on determining the effect of a finely ground pumice as a SCM in terms of its resistance to ASR expansion, as well as improving resistance to other potential concrete durability mechanisms. In spite of having high alkali contents in the pumice, mixtures containing the SCM pumice more effectively mitigated the ASR expansion reaction than other degradation mechanisms. Depending on the reactivity of the aggregates and fineness of the pumice, 10-15% replacement of cement with the pumice was found to reduce the ASR expansion to the acceptable limits. The amount of CH remaining in the concrete was compared to the ASR expansion in order to improve understanding of the role of CH in the ASR reaction. Thermo-gravimetric analysis (TGA) and X

  14. Eruptive shearing of tube pumice: pure and simple (United States)

    Dingwell, Donald B.; Lavallée, Yan; Hess, Kai-Uwe; Flaws, Asher; Marti, Joan; Nichols, Alexander R. L.; Gilg, H. Albert; Schillinger, Burkhard


    Understanding the physicochemical conditions extant and mechanisms operative during explosive volcanism is essential for reliable forecasting and mitigation of volcanic events. Rhyolitic pumices reflect highly vesiculated magma whose bubbles can serve as a strain indicator for inferring the state of stress operative immediately prior to eruptive fragmentation. Obtaining the full kinematic picture reflected in bubble population geometry has been extremely difficult, involving dissection of a small number of delicate samples. The advent of reliable high-resolution tomography has changed this situation radically. Here we demonstrate via the use of tomography how a statistically powerful picture of the shapes and connectivity of thousands of individual bubbles within a single sample of tube pumice emerges. The strain record of tube pumice is modelled using empirical models of bubble geometry and liquid rheology, reliant on a constraint of magmatic water concentration. FTIR analysis reveals an imbalance in water speciation, suggesting post-eruption hydration, further supported by hydrogen and oxygen isotope measurements. Our work demonstrates that the strain recorded in the tube pumice dominated by simple shear (not pure shear) in the late deformational history of vesicular magma before eruption. This constraint in turn implies that magma ascent is conditioned by a velocity gradient (across the conduit) at the point of origin of tube pumice. Magma ascent accompanied by simple shear should enhance high eruption rates inferred independently for these highly viscous systems.

  15. A note on an occurrence of pseudo-pumice along the beaches of Goa and Karnataka

    Digital Repository Service at National Institute of Oceanography (India)

    Jumaila, C.P.U.; Pattan, J.N.; Mascarenhas, A.; Parthiban, G.; Moraes, C.; Khedekar, V.D.

    -anomaly These light weight fragments do not correspond with natural pumice, but rather appear to be similar to the chemical composition of foam glass/ artificial pumice available in the market Therefore, it is concluded that these pumice clasts are a waste product...

  16. Drift pumice in the central Indian Ocean Basin: Geochemical evidence

    Digital Repository Service at National Institute of Oceanography (India)

    Pattan, J.N.; Mudholkar, A.V.; JaiSankar, S.; Ilangovan, D.

    allow one to define two different origins linked to two separate eruptions. One group of pumice is a dacitic type characterized by high Fe, Ti, Mg, Al and Ca with comparatively low contents of Si, rare-earth elements (Sigma PREE, 69 ppm), Rb, Sr, U, Th...



    GONEN, Tahir


    Self compacting mortars have been used as repair mortar or to determine component rates of the self compacting concrete. In this study; self compacting lightweight mortars were produced with basaltic pumice and expanded perlite aggregate. Expanded perlite aggregate was used at rates 10, 20, 30, 40 and 50% by volume instead of pumice aggregate and compared with reference specimens made fully pumice aggregate. Self compacting lightweight mortars were compared with self compacting mortar with ri...

  18. Microbial Contamination of Pumice Powder and Slurry in Dental Laboratories of Hamadan

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    Full Text Available Background Using contaminated pumice in polishing process of dental prostheses may result in cross-contamination of dentists, laboratory technicians, and patients. Objectives This study aimed to determine the presence and level of microbial contaminants in pumice powder and slurry used in dental laboratories of Hamadan city. Materials and Methods Forty specimens, including 20 pumice powders and 20 pumice slurries were collected from 10 randomly selected dental laboratories and inoculated onto selective and non-selective media in order to count the total colony-forming units (CFU. Isolated fungi and bacteria were identified using Gram-stain and deferential diagnostic tests. Results Results of this study showed 85% contamination rate for pumice powders and 100% for pumice slurries. Frequencies of Gram-positive and Gram-negative bacteria isolated from the powders were 68% and 32% respectively. For the slurries the frequencies were 61% Gram-positive and 39% Gram-negative. Organisms detected in pumice powders composed of Staphylococcus epidermidis, E. coli, Acinetobacter, B. cereus, Enterobacter, Candida, and diphtheroids. Organisms detected in pumice slurries included Staphylococcus epidermidis, E. coli, Citrobacter, S. aureus, Enterobacter, B. cereus, B. proteus, Candida, and diphtheroids. Conclusions According to this study, pumice powder and slurry used in dental laboratories of Hamadan are contaminated. Therefore, the Laboratory staff should be aware of the hazards posed by the presence of pathogens in dental laboratories.

  19. Characterization and stability studies of emulsion systems containing pumice

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    Marilene Estanqueiro


    Full Text Available Emulsions are the most common form of skin care products. However, these systems may exhibit some instability. Therefore, when developing emulsions for topical application it is interesting to verify whether they have suitable physical and mechanical characteristics and further assess their stability. The aim of this work was to study the stability of emulsion systems, which varied in the proportion of the emulsifying agent cetearyl alcohol (and sodium lauryl sulfate (and sodium cetearyl sulfate (LSX, the nature of the oily phase (decyl oleate, cyclomethicone or dimethicone and the presence or absence of pumice (5% w/w. While maintaining the samples at room temperature, rheology studies, texture analysis and microscopic observation of formulations with and without pumice were performed. Samples were also submitted to an accelerated stability study by centrifugation and to a thermal stress test. Through the testing, it was found that the amount of emulsifying agent affects the consistency and textural properties such as firmness and adhesiveness. So, formulations containing LSX (5% w/w and decyl oleate or dimethicone as oily phase had a better consistency and remained stable with time, so exhibited the best features to be used for skin care products.

  20. Quenching of steam-charged pumice: Implications for submarine pyroclastic volcanism (United States)

    Allen, S. R.; Fiske, R. S.; Cashman, K. V.


    Huge quantities of silicic pumice have been deposited in intra-oceanic convergent margin settings throughout Earth's history. The association of submarine silicic calderas with thick proximal accumulations of pumice lapilli suggests that these pyroclasts were deposited as a direct result of submarine eruptions. Yet when first erupted, these highly vesicular, gas-filled clasts had densities significantly less than seawater. Experiments carried out 1-atm on heated pumice samples whose vesicles were charged with steam, the dominant component of magmatic volatiles show that buoyancy of freshly erupted submarine pumice is transient. Upon quenching, the phase change of steam-to-liquid water creates strong negative pore pressures within the pumice vesicles that accelerate the absorption of surrounding water, generating high-density pumice and promoting rapid clast sinking. Variations in the physical properties of steam with temperature and pressure have important implications for submarine pyroclastic eruptions. Firstly, highly vesicular pumice can be deposited on the seafloor at temperatures elevated significantly above ambient if they are erupted at sufficient depths to remain wholly submarine (> ˜ 200 m) and either the fluid in which they cool contains heated water and/or they only absorb sufficient water to sink. Secondly, the rapid increase in density of the eruption column caused by condensation and the transition from buoyant (gas-filled) to denser (water-saturated) pumice lapilli, together with turbulent mixing with the surrounding seawater favour collapse and transport of pyroclasts in water-supported gravity currents. Finally, this mixing of the ejecta with seawater and the ease of water ingestion into permeable pumice clasts suggest that water-supported transport mechanisms can operate as primary dispersal processes in explosive submarine eruptions.

  1. Physical properties, morphology and petrological characteristics of pumices from the Central Indian Ocean Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Kalangutkar, N.G.; Iyer, S.D.; Ilangovan, D.

    from a source nearer to the site of deposition, which could be within or near the CIOB. The experiments by Whitham and Sparks (1986) support the theory that hot pumice sinks immediately on immersion in water despite having a lower density than water... of the Ninety East Ridge and the absence of a 12 favourable surface current circulation patterns in this region (Fairbridge, 1966; Frick and Kent, 1984) cast doubt on the drift theory for the CIOB pumice. Although pumice recovered from deeper areas...

  2. Pumice from volcanoes: Its possible role for the iron and silica budget of the surface ocean and diatom growth (United States)

    Teschner, C.; Olgun, N.; Duggen, S.; Croot, P.; Dietze, H.


    Volcanic eruptions can inject pumice in major amounts into the oceans. Pumice can swim in seawater as pumice rafts or single pieces for years and contain relatively high concentrations of iron and silica, mainly found in seawater-reactive, metastable glass. Yet it is unknown to what extent pumice can release iron and silica, important for diatom growth, to surface ocean water. We examined the release of iron and silica of pumice from Central American volcanoes in contact with natural seawater by means of Cathodic Stripping Voltammetry and standard photometry. Based on our data we focus on evaluating how pumice from volcanoes in Central America may have contributed to the budget of the key nutrients iron and silica in the Central Pacific Ocean. Our study also provides new constraints on the importance of pumice for the marine biogeochemical iron- and silica-cycle.

  3. Morphology and petrography of pumice from the Central Indian Ocean Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Iyer, S.D.; Karisiddaiah, S.M.

    Majority of pumice are equant with high Corey's shape factor values. Petrographic studies indicate flow bands of isotropic nature, with varied vesicle shape and size, and the diffractograms show them to be mainly composed of amorphous silica...

  4. Investigation of Phenol Removal from Aqueous Solutions Using Copper-Impregnated Pumice

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    A.R. Rahmani


    Full Text Available Introduction & Objectives: Recently, treatment of industrial wastewaters has attracted much attention of many governments and also environmental experts. Basically, these wastewaters are polluted due to the different contaminants such as dyes, halogenated hydrocarbons, phenolic compounds etc. Among these pollutants, phenols are widely used in petroleum, petrochemical, coal production and pharmaceutical industries. There are several methods for removing phenol from water including adsorption, wet peroxide oxidation, wet air oxidation, ozonation etc. Each of these methods has advantages and disadvantages. Therefore, in this study the adsorption of phenol on Copper modified pumice as an adsorbent was investigated. Materials & Methods: In this experimental study, the pumice granules were collected from Qorveh region in Kordestan with mesh 20. The pumice granules were modified by CuSO4. Synthetic solution of phenol was prepared and different parameters including pH (3, 7, 12 initial concentration of phenol (25, 50, 75, 100, 150, 200, 300,400 mg/L, contact time (20, 40, 60, 80,100,120 min and the adsorbent dose of modified pumice (0.25, 0.5, 0.75, 1 were examined in a batch reactor, respectively. The chemical composition and solid structure of pumice was analyzed using X-ray diffraction (XRD, XRF, and scanning electronic microscopy (SEM. Also, Langmuir and Freundlich models were studied in the sorption of phenol onto the pumice. To determine the optimum pH of adsorption process, pHPZC of pumice was measured. Results: The results showed that phenol removal efficiency had been increased by increasing contact time, initial concentration of phenol and the amount of modified pumice. On the other hand, removal efficiency decreased with increasing pH. The sorption process showed a good agreement with the Freundlich model. Also, pHPZC of modified pumice was 7.7. Conclusion: The results show that modified pumice can be used effectively in removing phenol. Due

  5. Optical, spectral and thermal properties of natural pumice glass (United States)

    Correcher, V.; Gomez-Ros, J. M.; Dogan, T.; Garcia-Guinea, J.; Topaksu, M.


    Pumice is a natural Si-rich material displaying a complex cathodo- (CL) and thermoluminescence (TL) glow curves. The UV-IR CL emission consists of (i) a UV waveband in the range of 340-420 nm,(ii) blue band at 450-480 nm and (iii) a broad emission in the green-red region (at 550-650 nm) that could be respectively linked to Non Bridging Oxygen Hole Centers (tbnd Si-O•), self-trapped excitons and point defects (Mn2+ -0.03%- and Fe -1.15%-). Thermal treatments performed on the TL glow curves allowed us to determine that the trap system could be associated with a continuum in the trap distribution, since successive thermal pretreatments in the range of 200-310 °C induce an emission that shifts linearly to higher temperatures when the thermal pretreatment (Tstop) is increased, while the intensity of the maxima decreases similarly to the peak area. The evaluation of the Ea values, s value and the trap system calculated by VHR, IR and Glow curve fitting methods considering three possible distribution function for n(E): gaussian, exponential and uniform, has given matching values for the 280 °C TL peak.

  6. Heterogeneous vesiculation of 2011 El Hierro xeno-pumice revealed by X-ray computed microtomography (United States)

    Berg, S. E.; Troll, V. R.; Deegan, F. M.; Burchardt, S.; Krumbholz, M.; Mancini, L.; Polacci, M.; Carracedo, J. C.; Soler, V.; Arzilli, F.; Brun, F.


    During the first week of the 2011 El Hierro submarine eruption, abundant light-coloured pumiceous, high-silica volcanic bombs coated in dark basanite were found floating on the sea. The composition of the light-coloured frothy material (`xeno-pumice') is akin to that of sedimentary rocks from the region, but the textures resemble felsic magmatic pumice, leaving their exact mode of formation unclear. To help decipher their origin, we investigated representative El Hierro xeno-pumice samples using X-ray computed microtomography for their internal vesicle shapes, volumes, and bulk porosity, as well as for the spatial arrangement and size distributions of vesicles in three dimensions (3D). We find a wide range of vesicle morphologies, which are especially variable around small fragments of rock contained in the xeno-pumice samples. Notably, these rock fragments are almost exclusively of sedimentary origin, and we therefore interpret them as relicts an the original sedimentary ocean crust protolith(s). The irregular vesiculation textures observed probably resulted from pulsatory release of volatiles from multiple sources during xeno-pumice formation, most likely by successive release of pore water and mineral water during incremental heating and decompression of the sedimentary protoliths.

  7. Some Weeds Community Percent in Response to Pumice Application on Soil under Water Stress Conditions

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    Davoud Zarehaghi


    Full Text Available A factorial experiment (using RCBD design with three replications was conducted in 2014 at the University of Tabriz-Iran, in order to determine the effects of pumice application (P1, P2, P3 and P4: control, 30, 60 and 90 tons per ha on soil and water stress (I1, I2 and I3: 100%, 70% and 50% water requirement calculated from class A pan, respectively on dominante weeds community percent. Results showed that community percent of weed species changed as a result of water stress and pumice application on soil. Distributions of Chenopodium album and Malva sylvestris were sensitive to water stress but, Amaranthus retroflexus and Solanum nigrum were neutral to water stress. In contrast, Amaranthus retroflexus, Cardaria draba, Setaria viridis, Sisymbrium irio, Xanthium strumarium, Convolvulus arvensis and Salsola rigida distribution were resistant to water stress. Community percent of Chenopodium album as sensitive species to water stress and Salsola rigida as resistance species to water stress positively affected by pumice application especially under water stress condition. Amaranthus retroflexus, Xanthium strumarium and Convolvulus arvensis were positively affected by pumice application under well and limited water supply conditions. In contrast, Cardaria draba, Sisymbrium irio and Solanum nigrum negatively affected by pumice under water stress and it had positive effect on community of these species under well watering conditions. Thus, application of pumice and water stress are two factors which change weed community precent.

  8. Pumice deposits of the Santorini Lower Pumice 2 eruption on Anafi island, Greece: Indications for a Plinian event of exceptional magnitude (United States)

    Keller, Jörg; Gertisser, Ralf; Reusser, Eric; Dietrich, Volker


    Isolated patches of Santorini pumice deposits are analysed from the non-volcanic island of Anafi at a distance of 31-38 km east from the centre of the Santorini caldera. The deposits are Plinian fall profiles with a primary thickness at this distance of 1.2-1.5 m and MP (maximum pumice) and ML (maximum lithic) diameters of 5 and 4 cm, respectively. The characteristic profile sequence of the analysed Anafi deposits corresponds perfectly with the Plinian sequence of the Lower Pumice 2 (LP2) profiles on Thera, the main island of the Santorini group, with the sub-divisions into LP2-A2-1, LP2-A2-2 and LP2-A3. Pumice glass chemistry, phenocryst assemblage and the significant content of grey cauliform scoriae make the compositional correlation with the Plinian LP2 eruption of Santorini unambiguous. With the new identification of LP2 deposits on Anafi, together with an ~ 4-5 times greater thickness in the main axis of dispersal of the proximal Plinian LP2 deposits compared to the Minoan fallout on Thera, the Plinian opening phase of the 172 ka LP2 eruption (LP2-A) is regarded by far as the most voluminous of all Plinian eruptive phases on Santorini.

  9. Origin and significance of the 2011 El Hierro xeno-pumice (United States)

    Zaczek-Pedroza, Kirsten; Troll, Valentin R.; Deegan, Frances M.; Meade, Fiona C.; Burchardt, Steffi; Carracedo, Juan C.; Klügel, Andreas; Harris, Chris; Wiesmaier, Sebastian; Berg, Sylvia E.; Barker, Abigail K.


    During the first week of the 2011/2012 submarine eruption off El Hierro (Canary Islands), peculiar light-coloured pumiceous rocks (xeno-pumice) were found floating on the sea. The appearance of these rocks led to a potentially inappropriate response from the authorities, because the rocks were viewed as likely indicators of high-silica magma and possible explosive eruptive behaviour. However, the eruption remained a relatively minor and dominantly effusive event and the origin and significance of these peculiar xeno-pumice rocks for volcanic monitoring remains unresolved. Three contrasting models have been put forward, describing them as: a) recycled hydrothermally altered felsic magmatic rocks (Meletlidis et al., 2012, Geophys. Res. Lett., 39:L17302), b) sediment-contaminated high-silica magma (Sigmarsson et al., 2013, Contrib. Mineral. Petrol., 165:601-622) or c) frothy xenoliths from pre-island sedimentary strata that were melted while immersed in magma (Troll et al., 2012, Solid Earth, 3:97-110). Here, we combine the three available datasets to assess the origin of El Hierro xeno-pumice in the light of texture, mineralogy, major and trace element composition, and oxygen isotope characteristics in order to discuss their significance. We note that: 1) Sedimentary relicts occur frequently in xeno-pumice samples with occasionally observed relict bedding. 2) Vesicle sizes are extremely variable, which documents multiple degassing events. The vesicles are biggest especially close to sedimentary relicts, likely the result of a complex mix of minerals and porewaters originally present. 3) The mineral assemblage of xeno-pumice includes quartz, smectite, illite, wollastonite, jasper and mica (XRD) and is akin to marine sedimentary rocks in the region (Hoernle, 1998, J. Petrol.,39:859-880; Robertson & Stillman, 1979, J. Geol. Soc., 136:47 -60; Aparicio et al., 2006, Geol. Mag. 143:181 -193). 4) CIPW norms calculated from xeno-pumice major element compositions show the

  10. The origin of ferro-manganese oxide coated pumice from the Central Indian Ocean Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Pattan, J.N.; Pearce, N.J.G.; Parthiban, G.; Smith, V.C.; Mudholkar, A.V.; Rao, N.R.

    ). HDT samples have relatively low SiO 2 and Na2 O while the remaining oxides (TiO 2, Al2 O3, Fe2 O3, MgO and K2 O) are all enriched compared to CIOB coated pumice. Similarly analyses from the MTT, and OTT fiamme and welded tuff are also different from... of plagioclase but with low content of An of 45 ± 5 and 30 ± 5 and other sample has more of albite than anorthite with An content of 40 ± 5 and 25 ± 5. Spinel in partially coated pumice is of magnetite (FeO-83.1%, TiO 2-10.6%) where as, fully coated pumice have...

  11. Coexistence of pumice and manganese nodule fields-evidence for submarine silicic volcanism in the Central Indian Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Iyer, S.D.; Sudhakar, M.

    -generation mine-sites of manganese nodules, of high abundance and paramarginal ore grade, seem to be closely related to the pumice field. Circumstantial evidence, i.e. juxtaposed pumice and nodule fields in the vicinity of three major fracture zones (73 degrees E...

  12. Origin of reverse-graded bedding in air-fall pumice, Coso Range, California (United States)

    Duffield, W.A.; Bacon, C.R.; Roquemore, G.R.


    The origin of reverse grading in air-fall pyroclastic deposits has been ascribed to: (1) changing conditions at an erupting vent; (2) deposition in water; or (3) rolling of large clasts over smaller clasts on the surface of a steep slope. Structural features in a deposit of air-fall pumice lapilli in the Coso Range, California, indicate that reverse grading there formed by a fourth mechanism during flow of pumice. Reverse-graded beds in this deposit occur where pumice lapilli fell on slopes at or near the angle of repose and formed as parts of the blanket of accumulating pumice became unstable and flowed downslope. The process of size sorting during such flow is probably analogous to that which sorts sand grains in a reverse fashion during avalanching on the slip faces of sand dunes, attributed by Bagnold (1954a) to a grain-dispersive pressure acting on particles subjected to a shear stress. In view of the several ways in which air-fall pyroclastic debris may become reverse graded, caution is advised in interpretation of the origin of this structure both in modern and in ancient deposits. ?? 1979.

  13. Pesticide behaviour in pumice and rockwool growth media; adsorption and transformation of metalaxyl, oxamyl and carbendazim

    NARCIS (Netherlands)

    Matser, A.M.; Leistra, M.


    Interactions of pesticides with substrates were studied. The adsorption of metalaxyl, oxamyl and carbendazim on unused pumice and rock-wool is much weaker than that on soils. The transformation rate of the pesticides in nutrient solution in contact with unused substrates is low. Metalaxyl is

  14. Pumice in the interglacial Whidbey Formation at Blowers Bluff, central Whidbey Island, WA, USA (United States)

    Dethier, D.P.; Dragovich, J.D.; Sarna-Wojcicki, A. M.; Fleck, R.J.


    A new 40Ar/39Ar age of 128??9 ka and chemical analyses of pumice layers from interglacial alluvium at Blowers Bluff, Whidbey Island, WA, show that the deposits are part of the Whidbey Formation, a widespread, mainly subsurface unit. Glass chemistry of the dated dacitic pumice does not match any analyzed northern Cascade source, but upper Pleistocene dacites from Glacier Peak and early Pleistocene silicic rocks from the Kulshan caldera are chemically similar. The chemistry of pumiceous dacite in younger units, including the latest Pleistocene Partridge Gravel, is similar to that of the dated material. The deep troughs of the modern northern Puget lowland must have been filled during deposition of the Whidbey Formation, allowing volcanic-rich sediment to reach what is now Whidbey Island. Topographic analysis of LIDAR images demonstrates that extensive erosion occurred during latest Pleistocene ice retreat. The Partridge Gravel likely records subglacial fluvial erosion along an ice tunnel and ice-marginal deposition into adjacent marine waters. Pumice in the Partridge Gravel probably was reworked from stratigraphically and topographically lower deposits, including those at Blowers Bluff. ?? 2007 Elsevier Ltd and INQUA.

  15. Recharge of an Unconfined Pumice Aquifer: Winter Rainfall Versus Snow Pack, South-central Oregon (United States)

    Cummings, M. L.; Weatherford, J. M.; Eibert, D.


    Walker Rim study area, an uplifted fault block east of the Cascade Range, south-central Oregon, exceeds 1580 m elevation and includes Round Meadow-Sellers Marsh closed basin, and headwaters of Upper Klamath Basin, Deschutes Basin, and Christmas Lake Valley in the Great Basin. The water-bearing unit is 2.8 to 3.0 m thick Plinian pumice fall from the Holocene eruption of Mount Mazama, Cascade Range. The perched pumice aquifer is underlain by low permeability regolith and bedrock. Disruption of the internal continuity of the Plinian pumice fall by fluvial and lacustrine processes resulted in hydrogeologic environments that include fens, wet meadows, and areas of shallow water table. Slopes are low and surface and groundwater pathways follow patterns inherited from the pre-eruption landscape. Discharge for streams and springs and depth to water table measured in open-ended piezometers slotted in the pumice aquifer have been measured between March and October, WY 2011 through WY2015. Yearly occupation on same date has been conducted for middle April, June 1st, and end of October. WY2011 and WY2012 received more precipitation than the 30 year average while WY2014 was the third driest year in 30 years of record. WY2014 and WY2015 provide an interesting contrast. Drought conditions dominated WY2014 while WY2015 was distinct in that the normal cold-season snow pack was replaced by rainfall. Cumulative precipitation exceeded the 30-year average between October and March. The pumice aquifer of wet meadows and areas of shallow water table experienced little recharge in WY2015. Persistence of widespread diffuse discharge from fens declined by middle summer as potentiometric surfaces lowered into confining peat layers or in some settings into the pumice aquifer. Recharge of the perched pumice aquifer in rain-dominated WY2015 was similar to or less than in the snow-dominated drought of WY2014. Rain falling on frozen ground drove runoff rather than aquifer recharge.

  16. The effect of blast furnace slag on the self-compactability of pumice aggregate lightweight concrete

    Indian Academy of Sciences (India)

    Murat Kurt; Türkay Kotan; Muhammed Said Gül; Rüstem Gül; Abdulkadir Cüneyt Aydin


    This paper presents the results of an experimental study of the effects of blast furnace slag, different water/(cement+mineral additive) ratios and pumice aggregates on some physical and mechanical properties of self-compacting lightweight aggregate concrete. In this study, pumice was used as lightweight aggregate. Several properties of self-compacting pumice aggregate lightweight concretes, such as unit weight, flow diameter, T50 time, flow diameter after an hour, V-funnel time, and L-box tests, 7, 28, 90 and 180-day compressive strength, 28-day splitting tensile strength, dry unit weight, water absorption, thermal conductivity and ultrasonic pulse velocity tests, were conducted. For this purpose, 18 series of concrete samples were prepared in two groups. In the first group, pumice aggregate at 100% replacement of natural aggregate was used in the production of self-compacting lightweight aggregate concrete with constant w/(c+m) ratios as 0.35, 0.40, and 0.45 by weight. Furthermore, as a second group, pumice aggregate was used as a replacement of natural aggregate, at the levels of 0, 20, 40, 60, 80, and 100% by volume. Flow diameters, T50 times, paste volumes, 28-day compressive strengths, dry unit weights, thermal conductivities and ultrasonic pulse velocity of self-compacting lightweight aggregate concrete were obtained over the range of 600–770 mm, 3–9 s, 435–540 l/m3, 10.6–65.0 MPa, 845–2278 kg/m3, 0.363–1.694 W/mK and 2617–4770 m/s respectively, which satisfies not only the strength requirement of semistructural lightweight concrete but also the flowing ability requirements and thermal conductivity requirements of self-compacting lightweight aggregate concrete.

  17. The effect of fly ash to self-compactability of pumice aggregate lightweight concrete

    Indian Academy of Sciences (India)

    Murat Kurt; Abdulkadir Cüneyt Aydin; Muhammed Said Gül; Rüstem Gül; Türkay Kotan


    This paper presents the results of an experimental study on the effects of fly ash, different water/(cement + mineral additive) ratios and pumice aggregates to some physical and mechanical properties of self-compacting lightweight aggregate concrete. In this study, pumice had been used as lightweight aggregates. Several properties of self-compacting pumice aggregate lightweight concretes like the unit weight, flow diameter, T50 time, flow diameter after an hour, V-funnel time, and L-box tests, 7, 28, 90 and 180-day compressive strength, 28-day splitting tensile strength, dry unit weight, water absorption, thermal conductivity and ultrasonic pulse velocity tests were investigated. For this purpose, 18 series of concrete samples were prepared in two groups. Pumice aggregate was used as a replacement of natural aggregate, at the levels of 0, 20, 40, 60, 80, and 100% by volume. Furthermore, a second series of 100% pumice aggregate was used for the production of self-compacting lightweight aggregate concrete with constant w/(c+m) ratios as 0.35, 0.40, and 0.45 by weight. The flow diameters, T50 times, paste volumes, 28-day compressive strengths, dry unit weights and thermal conductivities of self-compacting lightweight aggregate concrete were obtained in the range of 600–800 mm, 2–8 s, 471–572 lt/m3, 9.2–53.26 MPa, 839–2156 kg/m3 and 0.321–1.508 W/mk, respectively, which satisfies not only the strength requirement of semi-structural lightweight concrete but also the flowing ability requirements and thermal conductivity requirements of self-compacting lightweight aggregate concrete.

  18. Constraining the dynamics of volcanic eruptions by characterization of pumice textures

    Directory of Open Access Journals (Sweden)

    M. Polacci


    Full Text Available We have characterized the textures of pumice clasts from Phlegraean Fields to gain insights into the conduit flow-dynamics of alkaline explosive eruptions. Vesicularities, vesicle number densities, and vesicle sizes and shapes were measured to obtain the bulk and groundmass properties of the juvenile fraction of Campanian Ignimbrite (CI and Agnano Monte Spina (AMS eruptions. The results report the coexistence of three end-member pumice types in the deposits of both eruptions, 1 microvesicular, 2 tube and 3 expanded, which differ according to clast morphology and the macro- to microscopic vesicle texture. Vesicularities (0.85-0.94 for CI, 0.51-0.91 for AMS and vesicle number densities (2-4×105 cm-2 in CI, 3×105-106 cm-2 in AMS span quite a wide range in all the three pumice types. Overall, tube pumices exhibit the highest bulk (0.89 and groundmass (CI 0.85, AMS 0.82 average vesicle volume fractions but the lowest average vesicle number densities (CI 2×105, AMS 4×105 cm-2. Comparison with textures of calc-alkaline pumices has revealed many similarities and points to a common origin and distribution of the products from both magma compositions within the volcanic conduit. In addition, the results of the textural analysis were interpreted in the light of the conduit flow modeling of Phlegraean Fields eruptions. The comparison of textural observations with results from simulations of conduit magma ascent has exhibited a good agreement between measured and numerically calculated vesicularities for both compositions, helping to constrain the overall dynamics of alkaline versus calc-alkaline eruptions.

  19. Retention of phosphorous ions on natural and engineered waste pumice: Characterization, equilibrium, competing ions, regeneration, kinetic, equilibrium and thermodynamic study

    Energy Technology Data Exchange (ETDEWEB)

    Karimaian, Kamal Aldin [Department of Environmental Health Engineering, Faculty of Health, Kurdistan University of Medical Sciences, Sannandaj (Iran, Islamic Republic of); Amrane, Abdeltif [Ecole Nationale Supérieure de Chimie de Rennes, Université Rennes 1, CNRS, UMR 6226, Avenue du Général Leclerc, CS 50837, 35708 Rennes Cedex 7 (France); Kazemian, Hossein [Department of Chemical and Biochemical Engineering, Western University, London, ON, Canada N6A 5B9 (Canada); Panahi, Reza [Department of Biotechnology, Faculty of Chemical Engineering, Tarbiat Modares University, Tehran (Iran, Islamic Republic of); Zarrabi, Mansur, E-mail: [Department of Environmental Health Engineering, Faculty of Health, Alborz University of Medical Sciences, Karaj (Iran, Islamic Republic of)


    Natural and Mg{sup 2+} modified pumice were used for the removal of phosphorous. The adsorbents were characterized using XRF, XRD, SEM and FTIR instrumental techniques. In the optimal conditions, namely at equilibrium time (30 min), for a phosphorus concentration of 15 mg/L and pH 6, 69 and 97% phosphorus removals were achieved using 10 g/L of natural and modified pumice adsorbents, respectively. Maximum adsorption capacities were 11.88 and 17.71 mg/g by natural and modified pumice, respectively. Pseudo-second order kinetic model was the most relevant to describe the kinetic of phosphorus adsorption. External mass transfer coefficient decreased for increasing phosphorous concentration and film diffusion was found to be the rate-controlling step. Only a very low dissolution of the adsorbent was observed, leading to a low increase in conductivity and turbidity. Removal efficiency decreased for increasing ionic strength. It also decreased in the presence of competing ions; however modified pumice remained effective, since 67% of phosphorus was removed, versus only 17% for the natural pumice. The efficiency of the modified pumice was confirmed during the regeneration tests, since 96% regeneration yield was obtained after 510 min experiment, while only 22% was observed for the raw pumice.

  20. Understanding the initiation and development of explosive Plinian eruptions: the conduit processes, eruption dynamics and dispersal processes of the ignimbrite and caldera-forming Lower Pumice 1 (184 ka) and Lower Pumice 2 (172 ka) eruptions, Santorini Caldera, Greece


    Simmons, Jack Michael


    In this thesis, the internal stratigraphy, facies, and facies architecture of the rhyodacitic 184 ka Lower Pumice 1 (LP1) and 172 ka Lower Pumice 2 (LP2) eruption sequences, erupted from Santorini Caldera, Greece, are reassessed as the basis for understanding the initiation and development of caldera-forming Plinian eruptions, including the changing conditions of the magmatic system, the conduit and eruption processes, the transition between eruption phases and ultimately the evolution of the...

  1. Isotopic Characteristics and Age Dating of the Pumice in Okinawa Trough

    Institute of Scientific and Technical Information of China (English)

    陈丽蓉; 翟世奎; 申顺喜


    The data on the isotope compositions of rubidium,strontium and oxygen in the pumice ofOkinawa Trough are reported for the first time.The ages of the pumice were successfully dated with themethod of U-series disequilibrium.Then,the material source,crystallization evolution of magma and activi-ty cycles of volcanos are explored.Isotopic data show that pumice magma was originally from the mantle,but had undergone a full crystal-lization differentiation and had been contaminated to a fair extent by crust-derived materials before the mag-ma was erupted out of the sea floor.According to the dating results available so far,the earliest volcaniceruption in Okinawa Trough occurred about 70,000 a ago and the latest eruption was about 10,000 a B.P.During this period,there were three volcanic eruption cycles which were respectively corresponding to themiddle Late Pleistocene,the late Late Pleistocene and the Early Holocene.

  2. Characterization and performance of a toluene-degrading biofilm developed on pumice stones

    Directory of Open Access Journals (Sweden)

    Sacceddu Pasquale


    Full Text Available Abstract Background Hydrocarbon-degrading biofilms in the treatment of contaminated groundwaters have received increasing attention due to the role played in the so-called "biobarriers". These are bioremediation systems in which a microbial consortium adherent to a solid support is placed across the flow of a contaminated plume, thus promoting biodegradation of the pollutant. Results A microbial consortium adherent to pumice granules (biofilm developed from a toluene-enriched microflora in a mini-scale system, following continuous supply of a mineral medium containing toluene, over a 12-month period. Observation by scanning electron microscopy, together with quantification of the biomass attached to pumice, evidenced the presence of abundant exopolymeric material surrounding the cells in the biofilm. Toluene removal monitored during 12-month operation, reached 99%. Identification of the species, based on comparative 16S ribosomal DNA (rDNA sequence analysis, revealed that Rhodococcus erythropolis and Pseudomonas marginalis were the predominant bacterial species in the microbial consortium. Conclusion A structurally complex toluene-degrading biofilm, mainly formed by Rhodococcus erythropolis and Pseudomonas marginalis, developed on pumice granules, in a mini-scale apparatus continuously fed with toluene.

  3. The Plinian Lower Pumice 2 eruption, Santorini, Greece: Magma evolution and volatile behaviour (United States)

    Gertisser, Ralf; Preece, Katie; Keller, Jörg


    The Plinian Lower Pumice 2 (LP2) eruption (172 ka) was one of the first major caldera-forming eruptions of the Santorini volcanic complex (Greece). The eruption shows some striking similarities to the caldera-forming Late Bronze Age (Minoan) eruption in terms of field, petrological and geochemical characteristics of its eruptive products, which are used to reveal the storage conditions of the LP2 magmas, pre-eruptive magmatic processes and the behaviour and degassing of volatiles prior to and during eruption. The LP2 eruption comprises four, predominantly rhyodacitic eruptive units (LP2-A, B, C, D). The lowermost unit of the Plinian LP2 deposits (LP2-A) consists of a basal phreatomagmatic bed (LP2-A1), which is overlain by three discrete pumice fall deposits (LP2-A2-1, A2-2, A3), the most prominent of which (LP2-A3) contains abundant, quench-textured scoriae that range in composition from basalt to basaltic andesite. The eruption proceeded with the deposition of pumice-rich pyroclastic flows (LP2-B) characterised by a lower, stratified and cross-bedded ignimbrite (LP2-B1) that may grade into a massive, non-welded ignimbrite (LP2-B2), a lithic-rich pumiceous breccia (LP2-C) and a co-ignimbrite lithic lag breccia (LP2-D). The main volume of rhyodacitic magma, which formed by fractionation of olivine, clinopyroxene, orthopyroxene, plagioclase, amphibole, Fe-Ti oxides, pyrrhotite and apatite from basaltic parental magmas and assimilation of crustal rocks, was held at mid-crustal levels (≤ 16 km depth), magmatic temperatures of 831 ± 12 °C and an oxygen fugacity slightly above the fayalite-magnetite-quartz (FMQ) oxygen buffer. Injection of ˜ 200 °C hotter mafic magma into the rhyodacitic reservoir and subsequent mingling and minor hybridisation with the resident magma helped to remobilise the rhyodacitic host magma and determined the final compositional range of the erupted products. Melt inclusion data show that sulphur concentrations were reduced to < 270 ppm in

  4. Evaluation of Iron and Manganese-Coated Pumice Application for the Removal of as(v from Aqueous Solutions

    Directory of Open Access Journals (Sweden)

    Leila Babaie Far


    Full Text Available Arsenic contamination of water has been recognized as a serious environmental issue and there are reports on its epidemiological problems to human health. The objective of this study was to evaluate the performances of iron-coated pumice and manganese-coated pumice as the adsorbents for removing arsenate from aqueous solutions. The effect of various parameters such as adsorbent dose, contact time, pH and initial concentration on removal efficiency of arsenate were evaluated in batch mode. The data obtained from the kinetic studies were analyzed using kinetic models of pseudo-first-order and pseudo-second-order. In addition, two isotherm models of Freundlich and Langmuir were used to fit the experimental data. The results showed that the optimum dosage of iron-coated pumice and manganese-coated pumice for arsenate removal were 40 and 80 g/L whereas the adsorption process reached equilibrium after 80 and 100 min, respectively. The maximum removal efficiency of arsenate using the two adsorbents were both recorded in pH=3 as the removal efficiency gradually declinedfollowing every increase in pH values of the solution. Iron-coated pumice also showed to have high removal efficiency when the initial concentration of arsenate was high while the low concentration of arsenate was efficiently removed by manganese-coated pumice. Moreover, it was depicted that the adsorption kinetics by bothadsorbents followed pseudo-second order equation and the uptake data of arsenate were well fitted with Langmuir isotherm model. Therefore, it could be concluded that iron and manganese-coated pumice could beconsidered as suitable adsorbents for arsenate removal from aqueous solutions.

  5. Evaluation of iron and manganese-coated pumice application for the removal of as(v from aqueous solutions

    Directory of Open Access Journals (Sweden)

    Far Leila


    Full Text Available Abstract Arsenic contamination of water has been recognized as a serious environmental issue and there are reports on its epidemiological problems to human health. The objective of this study was to evaluate the performances of iron-coated pumice and manganese-coated pumice as the adsorbents for removing arsenate from aqueous solutions. The effect of various parameters such as adsorbent dose, contact time, pH and initial concentration on removal efficiency of arsenate were evaluated in batch mode. The data obtained from the kinetic studies were analyzed using kinetic models of pseudo-first-order and pseudo-second-order. In addition, two isotherm models of Freundlich and Langmuir were used to fit the experimental data. The results showed that the optimum dosage of iron-coated pumice and manganese-coated pumice for arsenate removal were 40 and 80 g/L whereas the adsorption process reached equilibrium after 80 and 100 min, respectively. The maximum removal efficiency of arsenate using the two adsorbents were both recorded in pH=3 as the removal efficiency gradually declined following every increase in pH values of the solution. Iron-coated pumice also showed to have high removal efficiency when the initial concentration of arsenate was high while the low concentration of arsenate was efficiently removed by manganese-coated pumice. Moreover, it was depicted that the adsorption kinetics by both adsorbents followed pseudo-second order equation and the uptake data of arsenate were well fitted with Langmuir isotherm model. Therefore, it could be concluded that iron and manganese-coated pumice could be considered as suitable adsorbents for arsenate removal from aqueous solutions.

  6. Authigenic Mineral Cycling in Roman Seawater Concrete with Campi Flegrei Pumiceous Ash Pozzolan (United States)

    Jackson, M. D.; Mulcahy, S. R.; Chen, H.; Li, Q.; Cappelletti, P.; Carraro, C.; Wenk, H. R.


    Alteration of Campi Flegrei pumiceous ash in Roman concrete harbor structures along the central Italian coast produced zeolite and Ca-silicate minerals that have reinforced cementitious fabrics for >2000 years. X-ray microdiffraction experiments and electron microprobe analyses show that diverse alteration paths produced authigenic phillipsite and Al-tobermorite in the pyroclasts, pores, and cementing matrix of mortars in Romacons drill cores from Portus Cosanus, Portus Neronis, and Baianus Sinus. These minerals have cation exchange capabilities for some radionuclides and heavy metal cations and are candidate sorbents for concrete waste encapsulations. Compositions of phillipsite in certain Portus Cosanus and Portus Neronis pumice clasts are similar to those in the Neapolitan Yellow Tuff. Dissolution of this phillipsite and alkali feldspar produced new, authigenic phillipsite with less Si, greater Al and Ca, Al-tobermorite, and poorly-crystalline binder in pumice vesicles. Conversely, alteration of trachytic glass to clay mineral (nontronite) in a Baianus Sinus tuff clast is associated with new, authigenic phillipsite and Al-tobermorite in the tuff and cementing matrix. The Al-tobermorite has lower Al/(Si+Al) and Ca/(Si+Al) compared to Al-tobermorite in relict lime clasts. These more siliceous crystals, similar to those in hydrothermally-altered basalt, have 11.3 Å d-spacing in [001]. Raman spectra show symmetrical bending of Si-O-Si and Si-O-Al linkages, Si-O and Si-Al symmetrical stretching, and possible Q3 Si and Al tetrahedral peaks that suggest cross-linking of silicate chains-an important factor in cation exchange. The authigenic crystals refine pore space, contribute to binding in interfacial zones, and obstruct microcrack propagation. The well-constrained history of temperature variations and seawater immersion could provide further information for understanding alteration in volcanoclastic deposits and predicting regenerative processes in high performance

  7. Measurement of water transport from saturated pumice aggregates to hardening cement paste

    DEFF Research Database (Denmark)

    Lura, Pietro; Bentz, Dale; Lange, David A.;


    In internal water curing of High Performance Concrete, it is fundamental to know how and when the water contained in the internal curing agent is released into the hydrating cement paste. In this study, X-ray absorption measurements showed that considerable transport of water from saturated pumice...... stone to hydrating cement paste with water/cement ratio 0.3 took place in the first days after casting and covered a distance of at least 4 mm. As a consequence, the total amount of water released by the lightweight aggregates, rather than the spatial distribution of the aggregates, is in this case...

  8. Fresh pumice from the Central Indian Basin: A Krakatau 1883 signature

    Digital Repository Service at National Institute of Oceanography (India)

    Mudholkar, A.V.; Fujii, T.

    stream_size 32199 stream_content_type text/plain stream_name Mar_Geol_125_143.pdf.txt stream_source_info Mar_Geol_125_143.pdf.txt Content-Encoding UTF-8 Content-Type text/plain; charset=UTF-8 Marine Geology 125 (1995... were dredged from different types of surficial sediments (siliceous, terrigenous and red clay) of the CIB (Udintsev, 1975). The area from which the pumice were collected lies approxi- mately between 5’S and 12”S, and 70”E and 84”E at an average...

  9. Hybrid Adsorptive and Oxidative Removal of Natural Organic Matter Using Iron Oxide-Coated Pumice Particles

    Directory of Open Access Journals (Sweden)

    Sehnaz Sule Kaplan Bekaroglu


    Full Text Available The aim of this work was to combine adsorptive and catalytic properties of iron oxide surfaces in a hybrid process using hydrogen peroxide and iron oxide-coated pumice particles to remove natural organic matter (NOM in water. Experiments were conducted in batch, completely mixed reactors using various original and coated pumice particles. The results showed that both adsorption and catalytic oxidation mechanisms played role in the removal of NOM. The hybrid process was found to be effective in removing NOM from water having a wide range of specific UV absorbance values. Iron oxide surfaces preferentially adsorbed UV280-absorbing NOM fractions. Furthermore, the strong oxidants produced from reactions among iron oxide surfaces and hydrogen peroxide also preferentially oxidized UV280-absorbing NOM fractions. Preloading of iron oxide surfaces with NOM slightly reduced the further NOM removal performance of the hybrid process. Overall, the results suggested that the tested hybrid process may be effective for removal of NOM and control disinfection by-product formation.

  10. Dye Removal From Textile Waste Water Through The Adsorption By Pumice Used In Stone Washing

    Directory of Open Access Journals (Sweden)

    Körlü Aysegül Ekmekçi


    Full Text Available Because the waste production is inevitable in almost all industries, the elimination of these wastes is a requirement in terms of environmental regulations and welfare of all the creatures in the future. In this study, the use of the waste pumice stones of a denim washing mill is intended to eliminate the pollutant by a waste material and obtain economic benefits by converting it to the adsorbent. The pollutants in the effluents obtained from three different localisations of waste water treatment system of the same factory were removed through the adsorption. The experimental studies were carried out in three different steps; characterisation of adsorbent before and after adsorption; adsorption isotherm studies and biological oxygen demand (BOD, chemical oxygen demand (COD measurements. Characterisation studies showed that the waste pumice has almost the same structural properties with unused one except the existence of some organic residues coming from washing process. The results of adsorption studies conducted at the adsorbent concentrations changing from 5 to 35 g/l revealed that the decolourisation was initial dye-concentration dependent. According to the BOD and COD measurements, the supernatants obtained at the end of adsorption could be assumed as somewhat polluted and this result indicates that the organic impurities other than indigo were also removed through the adsorption.

  11. 浮石催化水中臭氧分解研究%Catalytic ozone aqueous decomposition promoted by pumice

    Institute of Scientific and Technical Information of China (English)

    袁磊; 沈吉敏; 陈忠林


    To investigate the influences of pumice chemical surface properties on catalytic ozonation,the decomposition rate of ozone in water was measured over pumice and the mechanism of ozone catalytic decomposition was discussed.The results showed that the pseudo-first order rate of ozone decomposition increased by 37.4 % for pumice catalysts.When t-BuOH was added,the rate constant decreased by 45.2 % for pumice catalysts,suggesting that the decomposition of ozone followed the mechanism of hydroxyl radical(·OH).The removal of ozone increased with the increasing of surface hydroxyl groups.High initial pH presented a positive effect in the ozone alone and ozone/pumice system.The pumice surface at nearly zero charged point was favorable for the decomposition of ozone in aqueous solution.Ozone aqueous decomposition in the presence of pumice takes place mainly on the natural material surface.The presence of metal oxides in pumice might catalyse ozone decomposition into more active radicals.%为考察浮石表面化学性质对水中臭氧分解的影响,测定了浮石催化水中臭氧分解的速率常数并探讨催化臭氧分解的途径.结果表明:浮石促进水中臭氧一级分解速率常数提高了37.4%;利用叔丁醇捕获生成的羟基自由基,催化臭氧分解速率常数降低了45.2%,浮石催化臭氧分解生成了羟基自由基;浮石表面羟基密度与催化臭氧分解率成正相关;随着溶液初始pH值增大,单独臭氧分解和浮石催化臭氧分解率均增加;由浮石pHpzc决定的表面电荷状态与催化臭氧分解效果有关,表面接近电中性时对催化臭氧分解有利.水中臭氧分解主要发生在浮石表面,浮石表面的金属氧化物可能是催化水中臭氧分解的活性物质。

  12. Pemanfaatan Batu Apung (Pumice Lombok dan Bakteri (Baccillus Subtilis sebagai Agent Perbaikan Kerusakan Retak Pada Beton

    Directory of Open Access Journals (Sweden)

    Ida Rochani


    Full Text Available Batu apung (pumice merupakan bahan lokal yang banyak terdapat di wilayah Lombok, Nusa Tenggara Barat. Komposisi batu apung mengandung silika tinggi yaitu antara 52,30% - 65,60% dapat digunakan sebagai pozolan. Penggunaan batu apung (pumice  sebagai campuran pada penyusunan beton ringan yang mempunyai kuat tekan dan kuat lentur yang baik. Beton juga rentan terhadap kerusakan yang dapat bersumber dari beban ekstrim, serangan kimia dan kondisi lingkungan. Faktor kualitas beton berpengaruh terhadap proses terjadinya keretakan beton. Produksi semen  dalam penggunaan campuran beton dapat memberikan kontribusi 10% emisi CO2 ke atmosfer. Retak mikro merupakan fenomena yang tidak dapat terhindari, akan tetapi retak kecil dapat di atasi yang disebut penyembuhan  autogenous atau self-healing beton. Metode yang digunakan dalam perbaikan mandiri pada keretakan beton adalah pemanfaatan peranan bakteri Bacillus subtilis yang terenkapsulasi. Tujuan dari penelitian ini untuk mengetahui pengaruh penambahan enkapsulasi bakteri B. subtilis dalam campuran beton dengan campuran pozolan batu apung (pumice terhadap kemampuan menutup retak beton. Metode analisis penelitian self-healing beton berdasarkan tinjauan kimia, mekanik, fisis dan keberlanjutan secara ekonomi, toksi lingkungan, sosial. Tinjauan kimia pozolan batu apung Lombok mengandung SiO2 sebesar 56,56% dan Al2O3 sebesar 14,77% apabila bercampur dengan B. subtilis kurang signifikan sebagai self-healing beton dengan kadar perbaikan hanya 5,6%. Kuat lentur tertinggi terjadi dalam persentase enkapsulasi 3% dan diameter enkapsulasi 4 mm sebesar 1.497 KPa. Kuat tekan beton sebesar 21,053 MPa dalam persentase enkapsulasi 3% dan diameter enkapsulasi 2 mm. Analisis SEM  menyatakan bahwa peranan bakteri B. subtilis dan pozolan batu apung terlihat adanya serabut - serabut kecil yang menghubungkan antar partikel beton. Kadar persentase perbaikan mandiri dalam retak beton mencapai 5,6% dalam diameter enkapsulasi 4 mm

  13. The 12.1 ka Middle Toluca Pumice: A dacitic Plinian subplinian eruption of Nevado de Toluca in Central Mexico (United States)

    Arce, J. L.; Cervantes, K. E.; Macías, J. L.; Mora, J. C.


    The Nevado de Toluca volcano erupted explosively approximately 12.1 ka ago, producing a Plinian-subplinian eruption that deposited the Middle Toluca Pumice (MTP). The MTP consists of white and gray juvenile pumice, gray dense juvenile lapilli, and red altered lithic lapilli. The pumice is dacitic (63.54-65.06 wt.% SiO 2) with phenocrysts of plagioclase > orthopyroxene > hornblende ± ilmenite and titanomagnetite, and biotite xenocrysts set in a groundmass of rhyolitic glass (70-71 wt.% SiO 2). The MTP has a dispersal axis to the ESE covering an area of 92 km 2, with a minimum volume of 1.8 km 3 (DRE). Stratigraphic relations, grain size, componentry, and vesicularity analyses suggest that the eruption occurred in five major phases: (1) an opening magmatic phase that generated a 20-km-high Plinian column dispersed to the SE; (2) a hydromagmatic explosion followed with the establishment of a subplinian eruptive column (18-19 km high) dispersed tephra to the SE and gradually waned; (3) hydromagmatic explosions emplaced dilute pyroclastic density currents followed by the formation of an eruptive column of unknown height; (4) immediately after, a new magmatic explosion established another eruptive column; and (5) the collapse of the latter column generated two pumiceous pyroclastic density currents that were fully dilute proximally, but transformed into two granular-fluid pyroclastic currents that traveled 19 km from the source.

  14. Pesticide behaviour in pumice and rockwool growth media; behaviour of metalaxyl and oxamyl in glasshouse cultivation systems

    NARCIS (Netherlands)

    Matser, A.M.; Dekker, A.; Leistra, M.


    The behaviour of pesticides in substrates is studied to attain adequate low-dosage and low-emission crop protection. The pesticide solution flowed relatively fast through the pumice systems, because less water had to be replaced than in the rock-wool systems. The concentrations in the substrate and

  15. [New data on pumice's structure and biological effects among miners and millers]. (United States)

    Spatari, G; Barbaro, M; Pira, E; Rossi, F; Massiccio, M; Romano, C


    Pleural plaques among pumice workers on Lipari Island have been described and the Authors have suggested the hypothesis that such biological effect could be related to the particles' morphology characterized by the presence of elements similar to fibers. Analysis on compact bulk materials and on dust samples from different sites of the Island have been performed to obtain information on the chemical composition of such materials. The Scan Electron Microscopy (SEM) analyses confirm the presence of fibrous particles with a chemical structure similar to the Refractory Ceramic Fibers (RCF) composition. These results could explain the presence of plural plaques among the workers and new clinical and epidemiological evaluations of the potential effects associated to this exposure are needed.

  16. The catalytic activity of the iron-coated pumice particles used as heterogeneous catalysts in the oxidation of natural organic matter by H2O2. (United States)

    Alver, Alper; Karaarslan, Mihrican; Kılıç, Ahmet


    The oxidative removal of natural organic matter (NOM) from waters was investigated by hydrogen peroxide (H2O2) and iron-coated pumice particles in heterogeneous catalytic oxidation process (HCOP). Removal of trihalomethane (THM) precursors, which is formed THM by the reacts with chloride, was performed with the hydroxyl radicals. Coating the original pumice particles with iron oxides significantly enhanced the removal of NOM with peroxide. The studies were carried out in two sections: (1) decomposition of hydrogen peroxide in pure water with iron-coated pumice and (2) oxidation of THM Precursor (NOM) by hydrogen peroxide with iron-coated pumice. The monitored parameters in this study include dissolved organic carbon and trihalomethanes formation potential. The results show that iron-coated pumice catalyst significantly increased the removal efficiency of NOM in the HCOP. The results show that iron-coated pumice catalyst significantly increased the removal efficiency of NOM in the HCOP. Results show that the oxidation of NOM and remaining NOM with H2O2 is improved by the addition of iron-coated pumice particles which activate the H2O2 molecule, leading to the formation of hydroxyl radicals in a Fenton-like process.

  17. High magma decompression rates at the peak of a violent caldera-forming eruption (Lower Pumice 1 eruption, Santorini, Greece) (United States)

    Simmons, J. M.; Carey, R. J.; Cas, R. A. F.; Druitt, T. H.


    We use the deposit sequence resulting from the first catastrophic caldera collapse event recorded at Santorini (associated with 184 ka Lower Pumice 1 eruption), to study the shallow conduit dynamics at the peak of caldera collapse. The main phase of the Lower Pumice 1 eruption commenced with the development of a sustained buoyant eruption column, producing a clast-supported framework of rhyodacitic white pumice (LP1-A). The clasts have densities of 310-740 kg m-3, large coalesced vesicles that define unimodal size distributions and moderate to high vesicle number densities (1.2 × 109-1.7 × 109 cm-3). Eruption column collapse, possibly associated with incipient caldera collapse, resulted in the development of pyroclastic flows (LP1-B). The resulting ignimbrite is characterised by rhyodacitic white pumice with a narrow density range (250-620 kg m-3) and moderate to high vesicle number densities (1.3 × 109-2.1 × 109 cm-3), comparable to clasts from LP1-A. An absence of deep, basement-derived lithic clast assemblages, together with the occurrence of large vesicles and relatively high vesicle number densities in pumice from the fallout and pyroclastic flow phases, suggests shallow fragmentation depths, a prolonged period of bubble nucleation and growth, and moderate rates of decompression prior to fragmentation (7-11 MPa s-1). Evacuation of magma during the pyroclastic flow phase led to under-pressurisation of the magma reservoir, the propagation of faults (associated with the main phase of caldera collapse) and the formation of 20 m thick lithic lag breccias (LP1-C). Rhyodacitic pumices from the base of the proximal lithic lag breccias show a broader range of density (330-990 kg m-3), higher vesicle number densities (4.5 × 109-1.1 × 1010 cm-3) and higher calculated magma decompression rates of 15-28 MPa s-1 than pyroclasts from the pre-collapse eruptive phases. In addition, the abundance of lithic clasts, including deeper, basement-derived lithic assemblages

  18. The initiation and development of a caldera-forming Plinian eruption (172 ka Lower Pumice 2 eruption, Santorini, Greece) (United States)

    Simmons, J. M.; Cas, R. A. F.; Druitt, T. H.; Carey, R. J.


    The rhyodacitic 172 ka Lower Pumice 2 (LP2) eruption terminated the first magmatic cycle at Santorini (Greece), producing a proximal caldera collapse, facilitated the ingress of water into the magmatic system, the development of widespread PDCs and the deposition of a caldera collapse, the enlargement of a pre-existing flooded caldera and the discharge of lithic-rich PDCs, depositing proximal < 9 m thick lithic lag breccias (LP2-D).

  19. Hybrid Reinforced Concrete Frame Building with Pumice Brick Masonry Infill under Static Lateral Loading

    Directory of Open Access Journals (Sweden)



    Full Text Available The purpose of this study is to investigate the behaviour of hybrid reinforced concrete frame with pumice brick masonry infill under static lateral loading. The term hybrid herein is referred to the frame composed of precast block masonry unit and cast in-place reinforced concrete beams. Parameters considered in this study were frame opening representing doors and windows commonly used in the wall system. Six types of frame namely FS, FB, FDE, FDC, FWE and FWC designation for solid frame, bare frame, frame with door opening at edge, frame with door opening at centre, frame with window opening at edge and frame with window opening at centre respectively were considered. Test results indicated that the FS has a maximum lateral strength greater than that of FB. The lateral strength of FS was about 3.68 of FB. The frames with various openings have lateral strength nearly 2.3 of lateral strength of the bare frame, FB. Ductility factor of the frames varied from 2.4 to 4.92. The residual strength of the frame with openings were varies between 2.33 and 3.35 of the bare frame. The stiffness of the infilled frames with opening were varied from 3.56 to 3.67 of the bare frame. The presence of openings in the infilled frame did not affect the frame stiffness considerably.

  20. Uranium and thorium adsorption from aqueous solution using a novel polyhydroxyethylmethacrylate-pumice composite. (United States)

    Akkaya, Recep


    Poly(hydroxyethylmethacrylate-pumice), [P(HEMA-Pum)], composite was synthesized by free radical polymerization in aqueous solution. The adsorptive features of P(HEMA-Pum) composite were investigated for UO2(2+) and Th(4+) using a range of pH, concentration, time (kinetics), temperature (thermodynamics), ionic strength and selectivity, and the related parameters were derived from the obtained results. These results indicated that all adsorbents had high affinity to the uranium and thorium ions. The parameters obtained from Langmuir, Freundlich and Dubinin-Radsushkevich models fit the data well. The values of enthalpy and entropy changes showed that the overall adsorption process was endothermic (ΔH > 0) and increasing entropy (ΔS > 0), and it was spontaneous (ΔG < 0) as expected. The adsorption kinetics following the pseudo-second order model indicated that the rate-controlling step was chemical adsorption that occurred by ion exchange process. Reusability of P(HEMA-Pum) was also investigated, and it was found that the composite could be used at least 5 times.


    Directory of Open Access Journals (Sweden)

    Figen Balo


    Full Text Available This paper reports the results of a study conducted to evaluate the influence of class C fly ash (FA, clay (C, expanded perlite (EP, pumice powder (PP and epoxidized castor oil (ECO on the density, thermal conductivity, compressive strength, tensile strength, abrasion loss and water absorption of building material. Density, thermal conductivity, compressive strength and tensile strength decreased with the increase of ECO and FA as replacement for building material. These properties also decreased with increasing process temperature. The addition of clay in the building material had an increasing effect on these properties. The addition of clay decreased abrasion loss and water absorption as a function of replacement percent. The minimum thermal conductivity and maximum water absorption observed for the sample made with minimum clay and maximum FA-ECO ratios processed at the highest process temperature. The maximum compression-tensile strengths and minimum abrasion loss observed for the sample with maximum clay and minimum FA-ECO ratios processed at the lowest process temperature.

  2. Hepatotoxic microcystin removal using pumice embedded monolithic composite cryogel as an alternative water treatment method. (United States)

    Gurbuz, Fatma; Ceylan, Şeyda; Odabaşı, Mehmet; Codd, Geoffrey A


    Microcystins are the most commonly encountered water-borne cyanotoxins which present short- and long-term risks to human health. Guidelines at international and national level, and legislation in some countries, have been introduced for the effective health risk management of these potent hepatotoxic, tumour-promoters. The stable cyclic structure of microcystins and their common production by cyanobacteria in waterbodies at times of high total dissolved organic carbon content presents challenges to drinking water treatment facilities, with conventional, advanced and novel strategies under evaluation. Here, we have studied the removal of microcystins using three different forms of pumice particles (PPs), which are embedded into macroporous cryogel columns. Macroporous composite cryogel columns (MCCs) are a new generation of separation media designed to face this challenging task. Three different MCCs were prepared by adding plain PPs, Cu(2+)-attached PPs and Fe(3+)-attached PPs to reaction media before the cryogelation step. Column studies showed that MCCs could be successfully used as an alternative water treatment method for successful microcystin removal.

  3. The Quetzalapa Pumice: a voluminous late Pleistocene rhyolite deposit in the eastern Trans-Mexican Volcanic Belt (United States)

    Rodríguez, Sergio-Raúl; Siebe, Claus; Komorowski, Jean-Christophe; Abrams, Michael


    The study area is located in the east part of the Trans-Mexican Volcanic Belt, in the Las Cumbres Volcanic Complex (LCVC) which lies between two large stratovolcanoes: Pico de Orizaba (5700 m a.s.l.) to the south, and Cofre de Perote (4200 m a.s.l.) to the NNE. The most conspicuous structure of the LCVC is a 4-km-diameter circular crater with a dacitic dome in the center, which constitutes the remains of a destroyed stratovolcano. The Quetzalapa Pumice (QP) was produced by a plinian eruption that was dated by the 14C method at 20 000 yr. BP. The eruptive sequence consists predominantly of pumice fall deposits and scarce intra-plinian pyroclastic flow deposits, which crop out on the west flank of the LCVC. The absence of post-plinian ignimbrite deposits is striking. The deposits are well sorted, clast-supported with reverse grading at the base, with a medium to high accessory lithics content. The maximum average thickness of the deposit in the proximal areas is about 15 m and has been divided into three members: the Basal Member (BM), 2 m thick with four submembers (BMf 1, BMf 2, BMf 3, and BMafl), the Intermediate Member (IM), 10 m thick with two submembers (IMpf and IMaf), and the Upper Member (UM), 3 m thick with four submembers (UMpl, UMsdf, UMwaf, and UMpls). The predominant component of the fall deposits is a white, highly vesiculated pumice with 71% SiO 2 content. Plagioclase is the most abundant mineral followed by 1-3-mm-long biotite phenocrysts. The accessory lithics are lavas mostly of andesitic composition. Their abundance increases toward the uppermost levels of the sequence. We calculate a minimum volume of 8.4 km 3 (2.22 km 3 dense rock equivalent), for the entire QP deposit. Isopach and isopleth maps show that the IM deposit has an elongated distribution with a NNE-SSW direction, whereas the UM deposit has a circular distribution. We estimate a maximum eruptive column height for the IM of 20 km. Field studies and isopach and isopleth maps indicate

  4. Giant rafted pumice blocks from the most recent eruption of Taupo volcano, New Zealand: Insights from palaeomagnetic and textural data (United States)

    von Lichtan, I. J.; White, J. D. L.; Manville, V.; Ohneiser, C.


    Giant blocks of pumice lie strewn along a former shoreline of intracaldera Lake Taupo, New Zealand, and are the sole subaerial evidence of the most recent volcanism at the Taupo supervolcano. Geochemically they are identical to material erupted during the complex and multiphase 1.8 ka Taupo eruption, which they post-date by one to two decades. The blocks, some of which are > 10 m long, show complex jointing patterns indicative of both surface chilling and continued interior expansion, as well as heterogeneous vesicularity, with dense rims (mean density 917 kg/m3) grading via an intervening transition zone (mean density 844 kg/m3) into a more highly vesicular interior (mean density 815 kg/m3). Analysis of thermal demagnetisation data indicates significant reorientation of the blocks as they cooled through a series of blocking temperatures. Some parts of block rims cooled to below 580 °C well before emplacement on the shore, whereas other parts in the interior and transition zones, which cooled more slowly, acquired different orientations before stranding. Some block interiors cooled after blocks were finally deposited, and record the direction of the 1.8 ka field. The blocks are believed to be derived from one or both of a pair of rhyolitic lava domes that developed on the bed of Lake Taupo several decades after the climactic Taupo eruption over the inferred vent area. These, and similar giant rafted pumice blocks in other marine and lacustrine settings raise a number of questions about how volatile-rich felsic magma can be erupted underwater with only limited thermal fragmentation. Furthermore, the prolonged flotation of out-sized fragments of vesiculated magma formed during subaqueous dome-growth contrasts with the rapid sinking of smaller pieces of hot plinian pumice under laboratory conditions. The genesis of pumice forming the blocks is not entirely clear. Most simply the blocks may represent part of a vesiculated carapace of a growing lava dome, broken loose

  5. Juvenile pumice and pyroclastic obsidian reveal the eruptive conditions necessary for the stability of Plinian eruption of rhyolitic magma (United States)

    Giachetti, T.; Shea, T.; Gonnermann, H. M.; McCann, K. A.; Hoxsie, E. C.


    Significant explosive activity generally precedes or coexists with the large effusion of rhyolitic lava (e.g., Mono Craters; Medicine Lake Volcano; Newberry; Chaitén; Cordón Caulle). Such explosive-to-effusive transitions and, ultimately, cessation of activity are commonly explained by the overall waning magma chamber pressure accompanying magma withdrawal, albeit modulated by magma outgassing. The tephra deposits of such explosive-to-effusive eruptions record the character of the transition - abrupt or gradual - as well as potential changes in eruptive conditions, such as magma composition, volatiles content, mass discharge rate, conduit size, magma outgassing. Results will be presented from a detailed study of both the gas-rich (pumice) and gas-poor (obsidian) juvenile pyroclasts produced during the Plinian phase of the 1060 CE Glass Mountain eruption of Medicine Lake Volcano, California. In the proximal deposits, a multitude of pumice-rich sections separated by layers rich in dense clasts suggests a pulsatory behavior of the explosive phase. Density measurements on 2,600 pumices show that the intermediate, most voluminous deposits have a near constant median porosity of 65%. However, rapid increase in porosity to 75-80% is observed at both the bottom and the top of the fallout deposits, suggestive of rapid variations in magma degassing. In contrast, a water content of pyroclastic obsidians of approximately 0.6 wt% does remain constant throughout the eruption, suggesting that the pyroclastic obsidians degassed up to a constant pressure of a few megapascals. Numerical modeling of eruptive magma ascent and degassing is used to provide constraints on eruption conditions.

  6. Glass shards, pumice fragments and volcanic aerosol particles - diagenesis a recorder of volcanic activity? (United States)

    Obenholzner, J. H.; Schroettner, H.; Poelt, P.; Delgado, H.


    Detailed SEM/EDS studies of Triassic (Southern Alps, A, I, Sl) and Miocene (Mixteca Alta, Mexico) tuffs revealed that volcanic glass shards can be replaced by zeolites (analcite), chlorites and smectites preserving the shape of primary shards (1). The Triassic pyroclastic deposits have been incorporated in the pre-Alpine burial diagenesis, the Miocene pyroclastic deposits are bentonites. The volcanologist is impressed by the circumstances that million years old pyroclast relict textures can be sized. Shape parameters obtained by image analysis can be compared with much younger pyroclastic deposits (2). Both deposits have not been effected by shearing. The alteration of pumice fragments of Triassic age is not a simple replacement process. Intergrowth of different illites and chlorites and probably vesicle filling by SiO2 and subsequent overgrowth make a reconstruction sometimes difficult. These processes are accompanied by the formation of REE-, Y- and Zr-bearing minerals as well as with the alteration of zircons. Studies of recently erupted ash from Popocatepetl volcano reveal the presence of a variety of µm-sized contact-metamorphosed clasts being a part of the volcanic ash (3). Such clasts should be present in many older pyroclastic deposits, especially where volcanoes had been situated on massive sedimentary units providing contact metamorphism in the realm of a magma chamber or during magma ascent. Volcanic aerosol particles collected in 1997 from the passively degassing plume of Popocatepetl volcano revealed in FESEM/EDS analysis (H. Schroettner and P. Poelt) a wide spectrum of fluffy, spherical and coagulated spherical particles (µm-sized). Under pre-vacuum conditions they remained stable for ca. 3 years (3). In nature the fate of these particles in the atmosphere is unknown. Are there relicts in marine, lacustrine sediments and ice cores, which could be used as proxies of volcanic activity? (1) Obenholzner &Heiken,1999. Ann.Naturhist.Mus.Wien, 100 A, 13

  7. Littoral blasts: Pumice-water heat transfer and the conditions for steam explosions when pyroclastic flows enter the ocean (United States)

    Dufek, J.; Manga, M.; Staedter, M.


    Steam explosions, or littoral blasts, generated when pyroclastic flows interact with seawater may be a common, although rarely documented, phenomena. The development of steam explosions rather than passive steam production is related to the rate of thermal energy transfer from hot pyroclasts to water. We conduct a series of laboratory experiments to quantify the heat transfer and steam production rates when hot pyroclasts encounter water. Hot pumice (>200°C) rapidly ingests water while remaining at the surface, producing measurable amounts of steam during the process. Approximately 10% of the thermal energy of the pumice particles is partitioned into the production of steam, and smaller particles have greater steam production rates. The laboratory experiments are used to develop a subgrid model for steam production that can be incorporated into a multiphase numerical framework. We use this model to study the critical steam production rates required to initiate explosive events. For conditions typical of many pyroclastic flows, particles smaller than ˜1-5 mm are required to initiate a littoral blast. A second set of two-dimensional numerical simulations is conducted to simulate the 12-13 July Soufrière Hills dome collapse event that reached the sea. The simulations predict that the focus of the blast is likely generated several hundred meters offshore and although the landward directed base surge is primarily dry (water vapor), the area immediately above the blast is steam-rich and may be a likely site for the production of accretionary lapilli.

  8. Magma degassing and eruption dynamics of the Avellino pumice Plinian eruption of Somma-Vesuvius (Italy). Comparison with the Pompeii eruption (United States)

    Balcone-Boissard, H.; Boudon, G.; Ucciani, G.; Villemant, B.; Cioni, R.; Civetta, L.; Orsi, G.


    The eruptive history of Mt. Somma-Vesuvius is characterised by large explosive events: Pomici di Base eruption (22,030 ± 175 yr cal BP), Mercato (8890 ± 90 yr cal BP), Avellino (3945 ± 10 yr cal BP) and Pompeii (79 AD). Pre-eruptive conditions and sin-eruptive degassing processes of the Avellino eruption, the highest-magnitude Plinian event, have been investigated, using volatile contents (F, Cl, H2O) in melt inclusions and residual glass, and textural characteristics of pumice clasts of the 9 fallout layers sampled in detail in a representative sequence. The sequence displays an up-section sharp colour change from white to grey, corresponding to variations in both magma composition and textural characteristics. The pre-eruptive conditions have been constrained by systematic measurements of Cl content in both melt inclusions and matrix glass of pumice clasts. The pumice glass composition varies from Na-rich phonolite (white pumice) to K-rich phonolite (grey pumice). The measured Cl values constantly cluster at 5200 ± 400 ppm (buffer value), whatever the composition of the melt, suggesting that the entire magma body was saturated with sub-critical fluids. This Cl saturation constrains the pre-eruptive pressures and maximum H2O contents at 200 ± 10 MPa and 6.3 ± 0.2 wt.% H2O for the white pumice melt and 195 ± 15 MPa and 5.2 ± 0.2 wt.% H2O for the grey pumice melt. The fluid phase, mainly composed of a H2O-rich vapour phase and brine, probably accumulated at the top of the reservoir and generated an overpressure able to trigger the onset of the eruption. Magma degassing was rather homogeneous for the white and grey eruptive units, mostly occurring through closed-system processes, leading to a typical Plinian eruptive style. A steady-state withdrawal of an H2O-saturated magma may explain the establishment of a sustained Plinian column. Variation from white to grey pumice is accompanied by decrease of mean vesicularity and increase of mean microcrystallinity

  9. Predicting the movement of pumice rafts in the South Pacific using GNOME for enhanced navigational warnings and coastal hazard management policies (United States)

    Kelly, J.; Bender, M.; Kelly, M.; Walters, C.


    Pumice rafts formed from explosive shallow submarine eruptions in the South Pacific pose a significant hazard to local maritime transportation and global coastal communities. Local concerns include the possibility of individual pumice clasts blocking seawater intake valves of ships, damaging the hull of smaller vessels, and inundating harbors bringing fishing and transport to a standstill. Additionally, pumice rafts can introduce harmful invasive species to delicate coastal communities around the world as they dramatically increase dispersal distances for otherwise benthic or relatively sedentary organisms. Two volcanoes in this region have recently formed pumice rafts: Home Reef volcano (Tonga) in 2006 and Havre Seamount (Kermadec Islands) in 2012. These raft events were used as case studies to test a trajectory prediction model since they occurred during times at which high spatial and temporal resolution satellite data were being collected and/or have been described in peer reviewed literature, both of which were necessary for providing model validation. The model was created using the General NOAA Observational Modeling Environment (GNOME), which utilizes sea surface winds and sea surface height (SSH) datasets to predict the possible trajectory a pollutant might follow on a body of water. Wind and ocean current data were acquired from the SeaWinds and Poseidon-3 sensors on board the NASA Earth Observing System (EOS) satellites QuikSCAT and Jason-2. Model outputs showed the 2012 Havre Seamount raft rapidly disperse as it drifted in an ENE direction and the 2006 Home Reef raft drifted quickly in a NW direction towards Papua New Guinea. The 2006 Home Reef prediction model was validated by comparing it to another published model that was based on an integrated surface velocity field in addition to in situ observations. The 2012 Havre Seamount prediction model was validated by spatially and temporally correlating the GNOME trajectory output with moderate

  10. Nuclear magnetic resonance analysis of freeze-thaw damage in natural pumice concrete

    Directory of Open Access Journals (Sweden)

    Wang, Xiaoxiao


    Full Text Available This paper presents an analysis of the damage propagation features of the pore structure of natural pumice lightweight aggregate concrete (LWC under freeze-thaw cyclic action. After freeze-thaw cycling, we conducted nuclear magnetic resonance (NMR tests on the concrete and acquired the porosity, distribution of transverse relaxation time T2, and magnetic resonance imaging (MRI results. The results showed the following. The T2 distribution of the LWC prior to freeze-thaw cycling presented four peaks representative of a preponderance of small pores. After 50, 100, 150, and 200 freeze-thaw cycles, the total area of the T2 spectrum and the porosity increased significantly. The MRI presented the changing spatial distribution of pores within the LWC during freeze-thaw cycling. Ultrasonic testing technology was applied simultaneously to analyze the NMR results, which verified that the new NMR technology demonstrated high accuracy and practicability for research regarding freeze-thaw concrete damage.En este trabajo se analiza la propagación de los daños que se producen en la estructura porosa de hormigón aligerado a base de piedra pómez natural sometido a la acción cíclica de hielo-deshielo. Después de realizarse los ensayos de hielo-deshielo, el hormigón se analizó mediante resonancia magnética nuclear (RMN, determinándose la porosidad y la distribución del tiempo de relajación transversal, T2, y registrándose las imágenes captadas por resonancia magnética. De acuerdo con los resultados obtenidos, antes de los ciclos de hielo-deshielo la distribución de T2 del hormigón aligerado presentaba cuatro picos, indicativos de un predominio de poros pequeños. Después de que se sometiera a 50, 100, 150, y 200 ciclos, se observó un aumento importante tanto de la porosidad como de la superficie total del espectro de T2. Las imágenes captadas por resonancia magnética evidenciaron la modificación de la distribución espacial de los poros del

  11. Opal-replaced "Phenocrysts" in Fresh Pumice from 1817 Phreatomagmatic Deposits from Kawah Ijen, East Java, Indonesia: Implications for Eruptive Timescales? (United States)

    Lowenstern, J. B.; Wright, H. M. N.; van Hinsberg, V.; Berlo, K.; Iacovino, K.; Bindeman, I. N.


    Pumice: Opal-replaced plagioclase and pyroxene are in apparently unaltered dacite pumice from the 1817 phreatomagmatic eruption at Kawah Ijen, an arc volcano with a hyperacidic crater lake. Some remnants of replaced phenocrysts are visible as cores within the euhedral opalcrysts (0.01 to 3 mm in size). The pumice matrix glass is microlite-free and shows no evidence of alteration. Fresh non-opaline phenocryst phases include pyroxene, Fe-Ti oxide, apatite, and sulfide. FTIR and TCEA analyses demonstrate that the opal contains > 2-4 wt.% H2O. D/H ratios range from -115 to -155 ‰, far below meteoric or crater lake waters ( 0) or the bulk dacite (-86±3), and higher in oxygen 18/16 than the pumice (12.6 vs. 7.2 ‰). Other opaline material is found as layered colloidal lithics ( 750°C for <24 hours, caused the opalcrysts to dehydrate and convert to crystalline SiO2 forms. The origin of the opalcrysts remains confounding, and we continue to explore options for their origin.

  12. Effects of Volcanic Pumice Inputs on Microbial Community Composition and Dissolved C/P Ratios in Lake Waters: an Experimental Approach. (United States)

    Modenutti, B E; Balseiro, E G; Bastidas Navarro, M A; Lee, Z M; Souza, M S; Corman, J R; Elser, J J


    Volcanic eruptions discharge massive amounts of ash and pumice that decrease light penetration in lakes and lead to concomitant increases in phosphorus (P) concentrations and shifts in soluble C/P ratios. The consequences of these sudden changes for bacteria community composition, metabolism, and enzymatic activity remain unclear, especially for the dynamic period immediately after pumice deposition. Thus, the main aim of our study was to determine how ambient bacterial communities respond to pumice inputs in lakes that differ in dissolved organic carbon (DOC) and P concentrations and to what extent these responses are moderated by substrate C/P stoichiometry. We performed an outdoor experiment with natural lake water from two lakes that differed in dissolved organic carbon (DOC) concentration. We measured nutrient concentrations, alkaline phosphatase activity (APA), and DOC consumption rates and assessed different components of bacterial community structure using next-generation sequencing of the 16S rRNA gene. Pumice inputs caused a decrease in the C/P ratio of dissolved resources, a decrease in APA, and an increase in DOC consumption, indicating reduced P limitation. These changes in bacteria metabolism were coupled with modifications in the assemblage composition and an increase in diversity, with increases in bacterial taxa associated with biofilm and sediments, in predatory bacteria, and in bacteria with gliding motility. Our results confirm that volcanic eruptions have the potential to alter nutrient partitioning and light penetration in receiving waterways which can have dramatic impacts on microbial community dynamics.

  13. Eruption dynamics of the 7.7 ka Driftwood pumice-fall suggest mafic injection is a common eruption mechanism for Makushin Volcano, Alaska (United States)

    Lerner, A.; Crowley, P.; Hazlett, R. W.; Nicolaysen, K. E.


    Makushin Volcano on Unalaska Island, AK is potentially the most threatening volcano in the Aleutian chain, being close to the largest Aleutian towns of Dutch Harbor and Unalaska. This study reports the eruption chronology and triggering mechanism for the most recent highly explosive event, the 7.7 ka Driftwood Pumice-fall event. The Driftwood Pumice reaches thicknesses of over 2 m, and isopach contours estimate a total deposit volume of 0.3-0.9 km3, covering an area of at least 8100 km2. These reconstructions show an eruption on the scale of the 1980 Mt. St. Helens eruption, with a VEI of 4-5. In the field, the deposit was divided into four stratigraphic horizons from bottom to top, and tephra within these layers becomes systematically more mafic upward through the section, ranging from a basal low-SiO2 dacite (64 wt.% SiO2) to an upper medium-SiO2 andesite (61.5 wt.% SiO2). High-Ca plagioclase (An75-83) and high-Mg olivine (Mg69-75) grains within the pumice are in great disequilibrium with the dacitic glass (64-69 wt.% SiO2), suggesting their origin in a more mafic magma. Geochemical trends, disequilibrium mineral populations, and mineral zonation patterns within these plagioclase and olivine xenocrysts show evidence of magma mixing between a bulk siliceous magma chamber and a mafic injection. The amount of the mafic component increases upward within the deposit, ranging from 0-25% throughout the section. The mafic injection is calculated to have been ~110-200 °C hotter than the siliceous magma chamber. The thermal pulse provided by the injection likely initiated convection and volatile exsolution within the siliceous magma body, ultimately causing the Driftwood Pumice eruption. Diffusion rates based on the thickness of lower-Mg rim zonations (<10 µm thick rims of Mg64) in the olivine xenocrysts show a lag-time of ~1 year between the basaltic injection and the resulting eruption. Similar delays between mafic injections and eruptions are seen in numerous other

  14. Determination of chromium, cadmium and manganese in water and fish samples after preconcentration using penicillium digitatum immobilized on pumice Stone

    Energy Technology Data Exchange (ETDEWEB)

    Baytak, Sitki [Nevsehir University, Science and Art Faculty, Chemistry Department, Nevsehir (Turkey); Tuerker, A.R. [Gazi University, Science and Art Faculty, Chemistry Department, Ankara (Turkey)


    This study presents a procedure for preconcentration of Cr(III), Cd(II) and Mn(II) from water and biological samples using Penicillium digitatum immobilized on pumice stone. Optimum conditions such as pH, flow rate were evaluated. The recoveries of Cr(III), Cd(II) and Mn(II) under optimum conditions were found to be 98{+-}2%, 100{+-}2%, and 97{+-}2%, respectively, at a 95% confidence level. Detection limits were 2.0, 1.6 and 1.5 ng/mL for Cr(III), Cd(II) and Mn(II), respectively. The proposed procedure was successfully applied for the determination of chromium, cadmium and manganese in dam water, spring water and fish (Carp) samples. The accuracy was evaluated through the analysis of the certified standard reference fish tissue samples (IAEA-407) and spiked fish and water samples. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  15. Source and significance of pumices in tsunami deposits: examples from Tenerife (Canary Islands), Santorini (Greece) and Krakatau (Indonesia) volcanoes. (United States)

    Paris, R.; Nauret, F.


    Volcanic eruptions are quite often associated with tsunamis, and particularly caldera-forming eruptions near the coasts (e.g. Santorini, Krakatau, Aniakchak, Kikai). The main tsunamigenic processes are the entrance of massive pyroclastic flows in water, and flank instability, even if other processes might be involved (e.g. explosions). Fresh tephras are often preserved in sedimentary deposits left inland by tsunamis associated with volcanic eruptions. We review the different sources and incorporation mechanisms of pumices in tsunami deposits, and their significance in terms of volcanic processes, hydrodynamic processes (tsunami inundation) and their possible interactions. Three examples are adressed: the Krakatau 1883 eruption, the Minoan Thera eruption, and the El Abrigo eruption / Teno tsunami in Tenerife.

  16. Complex variations during a caldera-forming Plinian eruption, including precursor deposits, thick pumice fallout, co-ignimbrite breccias and climactic lag breccias: The 184 ka Lower Pumice 1 eruption sequence, Santorini, Greece (United States)

    Simmons, J. M.; Cas, R. A. F.; Druitt, T. H.; Folkes, C. B.


    The 184 ka Lower Pumice 1 eruption sequence records a complex history of eruption behaviours denoted by two significant eruptive phases: (1) a minor precursor (LP1-Pc) and (2) a major Plinian phase (LP1-A, B, C). The precursor phase produced 13 small-volume pyroclastic fallout, surge and flow deposits, which record the transition from a dominantly magmatic to a phreatomagmatic eruptive style, and exhibit a normal (dacite to andesitic-dacite) to reverse (andesitic-dacite to dacite) compositional zonation of juvenile pyroclasts in the stratigraphy. Incipient bioturbation and variability in unit thickness and lithology reflect multiple time breaks and highlight the episodic nature of volcanism prior to the main Plinian eruption phase. The Plinian magmatic eruption phase is defined by three major stratigraphic divisions, including a basal pumice fallout deposit (LP1-A), an overlying valley-confined ignimbrite (LP1-B) and a compositionally zoned (rhyodacite to basaltic andesite) lithic-rich lag breccia (LP1-C), which caps the sequence. This sequence records the initial development of a buoyant convective eruption column and the transition to eruption column and catastrophic late-stage caldera collapse events. Similarities in pyroclast properties (i.e., chemistry, density), between the Plinian fallout (LP1-A) and pyroclastic flow (LP1-B) deposits, indicate that changes in magma properties exerted no influence on the dynamics and temporal evolution of the LP1 eruption. Conversely, lithic breccias at the base of the LP1-B ignimbrite suggest that the transition from a buoyant convective column to column collapse was facilitated by mechanical erosion of the conduit system and/or the initiation of caldera collapse, leading to vent widening, an increase in magma discharge rate and the increased incorporation of lithics into the eruption column, causing mass overload. Lithic-rich lag breccia deposits (LP1-C), which cap the eruption sequence, record incremental, high

  17. Magma evolution and volatile behaviour prior to and during the Plinian Lower Pumice 2 eruption, Santorini, Greece (United States)

    Gertisser, R.; Preece, K.; Keller, J.


    The Plinian Lower Pumice 2 (LP2) eruption (c. 180 ka) was the first major caldera-forming eruption of the Santorini volcanic complex (Greece). The eruption shows some striking similarities to the caldera-forming Late Bronze Age (Minoan) eruption in terms of field, petrological and geochemical characteristics of its eruptive products, which are discussed here to reveal the storage conditions of the LP2 magmas, pre-eruptive magmatic processes and the behaviour and degassing of volatiles prior to and during eruption. The LP2 eruption consists of four discrete eruption phases that produced pyroclastic fall and flow deposits of predominantly rhyodacitic composition [Druitt et al., 1999, Geol. Soc. Lond. Mem., 19]. A subordinate basaltic to andesitic juvenile component, represented by grey, quench-textured scoriae, occurs mainly in the Plinian airfall deposits of the first eruption phase. Petrological and geochemical data indicate that the main volume of rhyodacitic LP2 magma formed by fractionation of olivine, clinopyroxene, orthopyroxene, plagioclase, amphibole, Fe-Ti oxides, pyrrhotite and apatite from basaltic magma with compositional characteristics similar to the most mafic scoriae and assimilation of small amounts of crustal rocks. The magma was stored at mid-crustal levels, magmatic temperatures of 831 ± 12°C and an oxygen fugacity slightly above the fayalite-magnetite-quartz (FMQ) oxygen buffer. Injection of c. 200°C hotter mafic magma into the rhyodacitic reservoir and subsequent mingling and minor hybridisation with the resident magma helped remobilising the rhyodacitic host magma and ultimately determined the observed compositional range of the erupted products. Melt inclusion data show that sulphur concentrations were reduced to less than 200 ppm in the rhyodacite, primarily due to partitioning of sulphur into a crystallising sulphide phase (pyrrhotite) during magmatic differentiation at oxygen fugacities around the FMQ oxygen buffer. Sulphur

  18. AMS radiocarbon dating of wood trunks in the pumiceous deposits of the Kikai-Akahoya eruption in Yakushima Island, SW Japan

    Energy Technology Data Exchange (ETDEWEB)

    Okuno, Mitsuru, E-mail: [Department of Earth System Science, Faculty of Science, Fukuoka University, 814-0180 Fukuoka (Japan); AIG Collaborative Research Institute for International Study on Eruptive History and Informatics, Fukuoka University, 814-0180 Fukuoka (Japan); Nakamura, Toshio [Center for Chronological Research, Nagoya University, 464-8602 Nagoya (Japan); Geshi, Nobuo [Geological Survey of Japan, National Institute of Advanced Science and Technology, 305-8567 Tsukuba (Japan); Kimura, Katsuhiko [Division of Environment System Management, Faculty of Symbiotic System Science, Fukushima University, 960-1296 Fukushima (Japan); Saito-Kokubu, Yoko [Tono Geoscience Center, Japan Atomic Energy Agency (JAEA), 959-31 Jorinji, Toki, Gifu 509-5102 (Japan); Kobayashi, Tetsuo [Department of Earth and Environmental Sciences, Graduate School of Science and Engineering, Kagoshima University, 890-0065 Kagoshima (Japan)


    Radiocarbon dating using accelerator mass spectrometry (AMS) was performed on numerous wood trunks from pumiceous deposits along the Nagata, Isso and Miyanoura rivers on the northern side of Yakushima Island, 60 km south of Kyushu Island. The obtained {sup 14}C dates were around 6.5 ka BP, which, in combination with the geological characteristics of the pumiceous deposits indicates that these specimens were buried during the Kikai-Akahoya (K-Ah) eruption from the Kikai caldera. However, the fact that they are not charred suggests that the origin of these deposits are not pyroclastic flows. Fourteen taxa (Pinus subgen. Diploxylon, Tsuga, Cryptomeria, Chamaecyparis, Myrica, Castanea, Castanopsis, Quercus subgen. Cyclobalanopsis, Trochodendron, Phellodendron, Lagerstroemia, Rhododendron, Myrsine and Symplocos) were identified through anatomical characteristics. This is the first discovery of forest species on the Yakushima Island before the devastating eruption.

  19. The Evidence from Inclusions in Pumices for the Direct Degassing of Volatiles from the Magma to the Hydrothermal Fluids in the Okinawa Trough

    Institute of Scientific and Technical Information of China (English)

    YU Zenghui; ZHAI Shikui; ZHAO Guangtao


    This article presents the evidence in support of the direct magma degassing as the principal mechanism of volatilesreleasing into the hydrothermal fluids in the Okinawa Trough, as contrasted to the argument for the hydrothermal strippingof volatiles from the volcanic rocks.Laser Raman microprobe and stepped-heating techniques are employed to determine the compositions and contents of thevolatiles in pumices in the middle Okinawa Trough. The results show that the volatiles are similar to the gases in the hy-drothermal fluids and hydrothermal minerals in composition, the mean percent content of each component and variationtrend. This indicates the direct influence of magma degassing on the hydrothermal fluids. In addition, the contents ofvolatiles in pumices are rather low and do not support the hydrothermal stripping as the main mechanism to enrich the fluidswith gases. The results are consistent with the idea that the direct magma degassing is more important than hydrothermalstripping in supplying gases to the hydrothermal fluids in the Okinawa Trough.

  20. Sr-Nd isotopic variations in the 4,965 yr BP "Ochre Pumice" plinian fallout of Popocatépetl: Preliminary results and interpretation (United States)

    Orsi, G.; Arana-Salinas, L.; Civetta, L.; Siebe, C.


    Popocatépetl (5452 masl), a Quaternary andesitic stratovolcano located 70 km SE of Mexico City in the central part of the Trans-Mexican Volcanic Belt (TMVB), is regarded as one of Mexico's potentially most dangerous volcanoes due to the highly explosive Plinian eruptions that are evidenced in its geological record. So far, only two of these eruptions have been studied in greater detail: The 14,100 yr BP "Tutti Frutti" (Sosa et al., 2012) and the 4,965 yr BP "Ochre" (Arana et al., 2010) eruptions. The latter is the subject of the present study. Isopach and isopleth maps of the "Ochre Pumice" (OP) indicate an eruption column height of 40 km and winds toward the NNE, where an area of 300 km2 was covered by >6 cm of pumice and ash. A minimum erupted volume was estimated at 5 km3, which corresponds to 1.7 km3 of dense rock equivalent (DRE). Stratigraphic relations indicate four different eruptive phases: pre-Plinian, Plinian 1, Plinian 2, and post-Plinian. The eruption started with the emplacement of pyroclastic flows. This initial explosive phase was followed by the most violent Plinian phase that first produced surges and then culminated with the eruption of the OP fallout deposit. As the eruption advanced, discharge rates became more intermittent and the height of the column fluctuated. Finally, the eruption column collapsed generating pumice-and-ash flows that were emplaced around the volcano. The juvenile component in the OP is mainly pumice, whereas the accidental components consist of igneous, sedimentary, and metamorphic clasts from the walls of the magma chamber and/or conduit. The vesicularity of the pumice decreases from bottom to top of the stratigraphic sequence while the crystal content increases. Previous studies at Popocatépetl established that compositions generally range from calcalkaline andesitic to dacitic. Chemical analyses of the OP pumice fallout show slight but significant variations. At the base it is less evolved (SiO2 = 61 wt.%) and it

  1. AMS radiocarbon dating of wood trunks in the pumiceous deposits of the Kikai-Akahoya eruption in Yakushima Island, SW Japan (United States)

    Okuno, Mitsuru; Nakamura, Toshio; Geshi, Nobuo; Kimura, Katsuhiko; Saito-Kokubu, Yoko; Kobayashi, Tetsuo


    Radiocarbon dating using accelerator mass spectrometry (AMS) was performed on numerous wood trunks from pumiceous deposits along the Nagata, Isso and Miyanoura rivers on the northern side of Yakushima Island, 60 km south of Kyushu Island. The obtained 14C dates were around 6.5 ka BP, which, in combination with the geological characteristics of the pumiceous deposits indicates that these specimens were buried during the Kikai-Akahoya (K-Ah) eruption from the Kikai caldera. However, the fact that they are not charred suggests that the origin of these deposits are not pyroclastic flows. Fourteen taxa (Pinus subgen. Diploxylon, Tsuga, Cryptomeria, Chamaecyparis, Myrica, Castanea, Castanopsis, Quercus subgen. Cyclobalanopsis, Trochodendron, Phellodendron, Lagerstroemia, Rhododendron, Myrsine and Symplocos) were identified through anatomical characteristics. This is the first discovery of forest species on the Yakushima Island before the devastating eruption.

  2. Nature and composition of interbedded marine basaltic pumice in the ~52–50 Ma Vastan lignite sequence, western India: Implication for Early Eocene MORB volcanism offshore Arabian Sea

    Indian Academy of Sciences (India)

    Sarajit Sensarma; Hukam Singh; R S Rana; Debajyoti Paul; Ashok Sahni


    The recognition of pyroclasts preserved in sedimentary environments far from its source is uncommon. We here describe occurrences of several centimetres-thick discontinuous basaltic pumice lenses occurring within the Early Eocene Vastan lignite mine sedimentary sequence, western India at two different levels –one at ~5 m and the other at 10 m above a biostratigraphically constrained 52 Ma old marker level postdating the Deccan Volcanism. These sections have received global attention as they record mammalian and plant radiations. We infer the repetitive occurrence of pumice have been sourced from a ~52–50Ma MORB related to sea-floor spreading in the western Arabian Sea, most plausibly along the Carlsberg Ridge. Pyroclasts have skeletal plagioclase with horsetail morphologies ± pyroxene ± Fe–Ti oxide euhedral crystals, and typically comprise of circular polymodal (radii ≤10 to ≥30 μm), non-coalescing microvesicles (>40–60%). The pumice have undergone considerable syngenetic alteration during oceanic transport and post-burial digenesis, and are a composite mixture of Fe–Mn-rich clay and hydrated alteredbasaltic glass (palagonite). The Fe–Mn-rich clay is extremely low in SiO₂, Al₂ O₂, TiO₂ , MgO, alkalies and REE, but very high in Fe₂O₃, MnO, P, Ba, Sr contents, and palagonitization involved significant loss of SiO₂, Al₂O₃, MgO and variable gain in Fe₂O₃, TiO₂, Ni, V, Zr, Zn and REE. Bubble initiationto growth in the ascending basaltic magma (liquidus ~1200–1250◦C) may have occured in ~3 hr. Shortdistance transport, non-connected vesicles, deposition in inner shelf to more confined lagoonal condition in the Early Eocene and quick burial helped preservation of the pumice in Vastan. Early Eocene Arabian Sea volcanism thus might have been an additional source to marginal sediments along the passive margin of western India.

  3. Evaluation of volcanic pumice stone as media in fixed bed sequence batch reactor for atrazine removal from aquatic environments. (United States)

    Derakhshan, Zahra; Ehrampoush, Mohammad Hassan; Mahvi, Amir Hossein; Faramarzian, Mohammad; Mokhtari, Mehdi; Mazloomi, Seyed Mohammad


    Atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) is a component of S-triazine. Its characteristics make it a pollutant of ecosystems and a probable human carcinogen. The present study evaluated volcanic pumice stone as a suitable media for biological growth and biofilm development in a fixed-bed sequencing batch reactor (FBSBR) for atrazine removal from aquatic environments. The FBSBR was fed with synthetic wastewater containing sucrose and atrazine at four hydraulic retention times to assess biodegradation of atrazine by a microbial consortium for removal from aquatic environments. The maximum efficiency for atrazine and soluble chemical oxygen demand removal were 97.9% and 98.9%, respectively. The results of this research showed that the Stover-Kincannon model was a very good fit (R(2) > 99%) for loading atrazine onto the FBSBR. Increasing the initial concentration of atrazine increased the removal efficiency. There was no significant inhibition of the mixed aerobic microbial consortia by the atrazine. Atrazine degradation depended on its initial concentration in the wastewater and the amount of atrazine in the influent. Although this system shows good potential for atrazine removal from aqueous environments, that remaining in the effluent does not yet meet international standards. Further research is required to make this system effective for removal of atrazine from the environment.

  4. Which came first: the pumice or the obsidian? Complex degassing transitions during the 114ka trachytic Pu'u Wa'aWa'a eruption (Hawaii) (United States)

    Hammer, J. E.; Shea, T.; Hellebrand, E.


    Fragmental obsidian clasts are highly correlated with coeval pumice in eruptions that produce obsidian (e.g., Lipari, Aeolian Islands; Little Glass Mountain, California; Mono-Inyo chain, California; Taupo, New Zealand), implying that at least some magma is able to degas quiescently prior to or during the explosive stage of an eruption. However, gross stratigraphic relationships reveal a consistent pattern of explosive activity transitioning to effusive activity (e.g., obsidian flows), suggesting subsurface stratification of magmatic volatiles. A prevailing conceptual model of obsidian formation reconciles these observations through (1) formation of dense glassy material by collapse of vesicles in bubbly magma, occuring in the shallow conduit or at the surface, (2) subsequent ascent of gas-rich magma and fragmentation/assimilation of the previously-emplaced obsidian clasts, followed by (3) transition to dominantly effusive eruptive activity. The Pu'u Wa'aWa'a trachytic pumice cone is unique feature in the Hawaii island volcanic landscape, otherwise dominated by basaltic lava. Around 114 ka, a pulsating explosive eruption at Hualalai Volcano expelled trachytic pumice, forming a ~150-200 m high cone. This phase was immediately followed by the outpouring of a large trachyte flow (the most voluminous silicic lava flow identified in Hawaii ~5 km3), identical in bulk composition to the pumice. The tephra deposits of the cone contain abundant obsidian clasts, as well as pyroclasts bearing striking gradual textural transitions and discretely banded pumiceous, scoriaceous and aphanitic material. The intricate variations in glass H2O contents (measured by microRaman), microlite and vesicle abundances (textural analysis), along with the chemical traits (EMPA) displayed by glasses from the diverse textural end-members suggest a complex ascent and eruption history. We test three hypotheses: (a) the obsidian clasts formed during ascent, stalling and outgassing of the magma (i

  5. The 21,700 yr b.p. Lower Toluca Pumice Plinian Eruption of Nevado de Toluca Volcano (Mexico): Evidences of Magma Mixing Process as Triggering Mechanism. (United States)

    Capra, L.; Arce, J.; Macias, J.


    Approximately 21,700 yr B.P., after a period of quiescence of 4800 yr, Nevado de Toluca volcano erupted, producing the Lower Toluca Pumice deposit. The activity generated a 24-km-high Plinian column that lasted ~11 h and dispersed 2.3 km3 (0.8 km3 dense rock equivalent) of tephra toward the NE, blanketing the Lerma basin, an area occupied today by the city of Toluca, with up to 5 cm of ash. Subsequent eruptive pulses were sub-Plinian in style, accompanied by phreatomagmatic explosions that emplaced surge deposits. Finally, the column collapsed toward the NE with the emplacement of a pumice flow deposit. The high vesicularity of the pumice from the basal Plinian layer, up to 83% by volume, indicates that exsolution was dominantly magmatic, and that pressurization of the magma chamber was probably due to a magma mixing process. Evidence for this includes the compositional range of juvenile products (from 55 to 65 wt% SiO2), as well as the presence of two types of plagioclase, one in equilibrium and the other one with disequilibrium textures and reverse zoning. This suggests input of an andesitic liquid into the dacitic magma chamber. Based on the eruptive record, the most likely future eruptive activity at Nevado de Toluca volcano will be Plinian. Although quiet for more than 3250 yr, Plinian activity could occur after a long period of quiescence, and it could represent a hazard for the entire Toluca basin, where more than one million people live today.

  6. Three-dimensional analysis of vesicle and crystal fragment textures in pumice using high-resolution X-ray CT: Textural evidence of eruptive processes (United States)

    Ketcham, R. A.; Gardner, J. E.; Abbott, S.


    Three-dimensional analysis of high-resolution X-ray computed tomographic (CT) imagery of pumice from Popocatépetl Volcano in central Mexico yields fresh insights into processes of vesicle formation and coalescence and crystal fragmentation that occur during explosive volcanism. Six ~2 cm pumice fragments of varying bulk vesicularity were imaged at ~20 μm resolution. Three-dimensional blob and fabric analysis quantitatively document textural features, and visualization facilitated contextualization of measurements and overall interpretation. Vesicles range in size from mm-scale to below the resolution of the scan data. By comparing the whole-sample 3D vesicle size distributions derived from CT with more detailed distributions from sub-volumes obtained by standard petrographic analysis, we can discern two distinct, roughly log-normal populations in each sample. Vesicles in all samples have preferred orientations, and fabric analysis based on the star volume distribution and displayed as 3D rose diagrams documents a range of preferred shapes from elongate to flattened. Aspect ratios range from 1 to 6, and converge to values of ~2-3 with increasing size. Surface to volume ratios show increasing departure from sphericity with increasing size, which is probably attributable in large part to irregular shapes caused by coalescence. The vesicle fabric was strongest in the highest-vesicularity sample. Some pumices showed evidence of welding or poor mixing between two or more differently devolatilized portions of melt. Interfaces are in some cases apparently welded, with low-vesicularity glass contact zones, and in others are simply sub-planar intersections between distinct glasses. In one instance of the latter, correlated vesicle and phenocryst orientations across both melt portions and not parallel to their interface suggests that their juxtaposition took place before final eruption, while there was still time for fabric development. The pumices show abundant evidence of

  7. The geology and petrology of Volcán San Juan (Nayarit, México) and the compositionally zoned Tepic Pumice (United States)

    Luhr, James F.


    Volcán San Juan is the westernmost Quaternary composite volcano in the Mexican Volcanic Belt. Its activity is divided into three stages of decreasing eruptive volume. During stage-1 activity, the main cone of San Juan and the adjacent Cerro Alto grew to a combined volume of ˜60 km 3 through eruption of hornblende-bearing andesites, dacites, and rhyodacites. Stage 1 included explosive eruptions of hornblende-dacite and an andesite dated at 33,750 a (years ago) and 23,010 a. Stage-2 activity involved a major Plinian eruption 14,770 a that produced the hypersthene-hornblende-bearing, compositionally zoned, rhyodacitic-andesitic Tepic Pumice and led to formation of an oval-shaped caldera 4×1 km in diameter. Tepic, the capital city of Nayarit State, with a population of ˜250,000, lies at the NE foot of Volcán San Juan. This location was buried under 2-9 m of rhyodacitic pumice-fall deposits from the Tepic Pumice eruption. Erosion has since removed virtually all exposures of Tepic Pumice >15 km from the caldera. The estimated volume of erupted tephra is 5.6 km 3, equivalent to 1.2 km 3 of magma. Modeling of the eruption dynamics indicates that as the eruption evolved the column height increased from ˜15 km to ˜24 km and maximum mass discharge rate increased from ˜3×10 6 kg/s to ˜6×10 7 kg/s. During stage-3 activity, a hornblende-andesitic lava dome partially filled the caldera and sent block lava flows down the north slope of the cone; total erupted volume was ˜0.55 km 3. Compared to other composite volcanoes of the western Mexican Volcanic Belt, the products from San Juan have the highest Sr contents and the lowest Rb, Y, Yb, and Lu contents, resulting in high La/Yb and Sr/Y, with low Rb/Sr. These observations indicate a strong slab-melt component at San Juan, consistent with its proximity to the Middle America Trench where young, hot lithosphere is subducting. The San Juan andesites, dacites, and rhyodacites also have relatively high 87Sr/ 86Sr, 206Pb/ 204

  8. Probabilistic hazard assessment of tephra dispersal from the Ochre Pumice Plinian eruption at Popocatepetl, Mexico and implications for civil aviation (United States)

    Scaini, C.; Bonasia, R.; Capra, L.; Nathenson, M.; Araña-Salinas, L.; Siebe, C.; Folch, A.


    Popocatepetl volcano is one of the most active in the Mexican country. The historical record of the volcano shows an intense explosive activity with tephra dispersal and deposition jeopardizing the surrounding populations and infrastructures. In particular, far-range tephra dispersal in atmosphere can impact the Mexican air traffic network. There are several important airports in the surroundings, such as Benito Juarez and Puebla International Airports, located respectively at 70 and 50 km from Popocatepetl volcano. Moreover, several national and international aerial routes cross over the nearby airspace. An explosive event at Popocatepetl volcano may produce strong disruptions to relevant airports, with strong socio-economic consequences. An hazard assessment has already been carried out for several volcanic hazards at Popocatepetl volcano, and amongst them tephra deposition at ground. However, no hazard assessment of tephra dispersal has never been performed yet, and is therefore necessary to complete the multi-hazard assessment. Here, we present the first probabilistic tephra dispersal hazard assessment for Popocatepetl volcano. Probabilistic hazard assessment is carried out for a selected eruptive scenario, defined on the basis of the Ochre Pumice Plinian eruption. The definition of eruptive parameters is based on field data and literature. Moreover, eruptive parameters have been verified through the inversion process, performed with HAZMAP analytical model. Probabilistic hazard maps are produced with FALL3D numerical model. Having performed 500 numerical simulations at HORUS Supercomputer (Computational Geodynamics Laboratory, Queretaro, Mexico), results have been merged to produce probabilistic hazard maps of tephra dispersal at relevant flight levels (FL050 and FL300). The critical ash concentration thresholds considered are 0.2 and 2 mg per cubic meter, taking into account the current European regulation and the recent ICAO indications for Mexican airspace

  9. Application of Acidic Treated Pumice as an Adsorbent for the Removal of Azo Dye from Aqueous Solutions:kinetic, Equilibrium and Thermodynamic Studies

    Directory of Open Access Journals (Sweden)

    Saied Bashiri


    Full Text Available Colored effluents are one of the important environment pollution sources since they contain unused dye compounds which are toxic and less-biodegradable. In this work removal of Acid Red 14 and Acid Red 18 azo dyes was investigated by acidic treated pumice stone as anefficient adsorbent at various experimental conditions. Removal of dye increased with increase in contact time and initial dye concentration, while decreased for increment in solution temperature and pH. Results of the equilibrium study showed that the removal ofAR14 and AR18 followed Freundlich (r2>0.99 and Langmuir (r2>0.99 isotherm models.Maximum sorption capacities were 3.1 and 29.7 mg/g for AR 14 and AR18, namely significantly higher than those reported in the literature, even for activated carbon. Fitting of experimental data onto kinetic models showed the relevance of the pseudo-second order (r2>0.99 and intra-particle diffusion (r2>0.98 models for AR14 and AR18, respectively. For both dyes, the values of external mass transfer coefficient decreased for increasing initial dye concentrations, showing increasing external mass transfer resistance at solid/liquid layer.Desorption experiments confirmed the relevance of pumice stone for dye removal, since the pH regeneration method showed 86% and 89 % regeneration for AR14 and AR18,respectively.

  10. Application of acidic treated pumice as an adsorbent for the removal of azo dye from aqueous solutions: kinetic, equilibrium and thermodynamic studies

    Directory of Open Access Journals (Sweden)

    Samarghandi Mohammad


    Full Text Available Abstract Colored effluents are one of the important environment pollution sources since they contain unused dye compounds which are toxic and less-biodegradable. In this work removal of Acid Red 14 and Acid Red 18 azo dyes was investigated by acidic treated pumice stone as an efficient adsorbent at various experimental conditions. Removal of dye increased with increase in contact time and initial dye concentration, while decreased for increment in solution temperature and pH. Results of the equilibrium study showed that the removal of AR14 and AR18 followed Freundlich (r2>0.99 and Langmuir (r2>0.99 isotherm models. Maximum sorption capacities were 3.1 and 29.7 mg/g for AR 14 and AR18, namely significantly higher than those reported in the literature, even for activated carbon. Fitting of experimental data onto kinetic models showed the relevance of the pseudo-second order (r2>0.99 and intra-particle diffusion (r2>0.98 models for AR14 and AR18, respectively. For both dyes, the values of external mass transfer coefficient decreased for increasing initial dye concentrations, showing increasing external mass transfer resistance at solid/liquid layer. Desorption experiments confirmed the relevance of pumice stone for dye removal, since the pH regeneration method showed 86% and 89% regeneration for AR14 and AR18, respectively.

  11. Study on photo-catalyzing performance and durability of Ag-TiO2/pumice%载Ag-TiO2/浮石光催化性能及耐用性考察

    Institute of Scientific and Technical Information of China (English)

    赵玲; 郑勋超; 周铁海; 尹平河


    采用天然浮石作为TiO2的载体,以溶胶-凝胶法制备TiO2/浮石,并将银沉积在TiO2表面制得载Ag-TiO2/浮石光催化剂.利用XRD、SEM进行表征,考察了载Ag-TiO2/浮石的光催化性能及其耐用性能.结果表明,载Ag-TiO2浮石对质量浓度为10mg/L的亚甲基蓝溶液具有良好的光催化降解效果,30min时降解率超过90%.在反复使用30次之后,反应30min时的降解率由最初的91.5%下降到75.1%,但经再生后即可恢复其活性,说明所制备的催化剂在多次使用后存在一定程度的化学失活.扫描电镜下观察使用60次的载Ag-TiO2浮石表面的薄膜基本完好.%Ag-TiO2/pumice has been prepared by using natural pumice as the carrier of TiO2, TiO2/pumice prepared by sol-gel method and Ag loaded on the surface of the TiO2 film. It is characterized by XRD and SEM. The photocatalyzing performance and durability of loaded Ag-TiO2/pumice are studied and investigated. The results show that loaded Ag-TiO2/pumice has very good photo-catalysis/degradation efficiency on the 10 mg/L methylene blue solution. It takes 30 minutes to degrade above 90% of the methylene blue. After Ag-TiO2/pumice has been used repeatedly 30 times, and reacted for 30 min,the degrading rate of the catalyst decreases from 91.5% to 75.1% ,but after the regeneration, its activity can be recovered. It shows that the chemical deactivation of the photo-catalysts occurs to a certain extent after being used many times. It is observed under SEM that the surface film of loaded AgTiO2/pumice basically keeps intact, after having been used 60 times.

  12. FeTi oxide mineralogy and the origin of normal and reverse remanent magnetization in dacitic pumice blocks from Mt. Shasta, California (United States)

    Lawson, C.A.; Nord, G.L.; Champion, D.E.


    Detailed mineralogical analyses and rock magnetic experiments have made it possible to directly identify the FeTi oxide phases responsible for the normal and reverse magnetic components of two dacitic pumice blocks from Mt. Shasta, California. Both samples contain a normal component carried by 100 ??m size multi-domain (MD) titanomagnetite (Usp11-24). One sample also contains a second normal component carried by behavior of the ferrian ilmenite. (1) The disordered boundaries are the higher Curie point phase necessary for the operation of the self-reversal mechanism. (2) The disordered domain boundaries either inhibit the formation of magnetic domain walls or restrict magnetic domain wall movement accounting for the PSD or SD behavior of the ferrian ilmenite. ?? 1987.

  13. FeTi oxide mineralogy and the origin of normal and reverse remanent magnetization in dacitic pumice blocks from Mt. Shasta, California (United States)

    Lawson, Charles A.; Nord, Gordon L.; Champion, Duane E.


    Detailed mineralogical analyses and rock magnetic experiments have made it possible to directly identify the FeTi oxide phases responsible for the normal and reverse magnetic components of two dacitic pumice blocks from Mt. Shasta, California. Both samples contain a normal component carried by 100 μm size multi-domain (MD) titanomagnetite (Usp 11-24). One sample also contains a second normal component carried by behavior of the ferrian ilmenite. (1) The disordered boundaries are the higher Curie point phase necessary for the operation of the self-reversal mechanism. (2) The disordered domain boundaries either inhibit the formation of magnetic domain walls or restrict magnetic domain wall movement accounting for the PSD or SD behavior of the ferrian ilmenite.

  14. Penicillium digitatum immobilized on pumice stone as a new solid phase extractor for preconcentration and/or separation of trace metals in environmental samples

    Energy Technology Data Exchange (ETDEWEB)

    Baytak, Sitki [Department of Chemistry, Faculty of Science and Arts, Harran University, 63100 Sanliurfa (Turkey); Kenduezler, Erdal [Department of Primary Education, Faculty of Education, Ahi Evran University, 40100 Kirsehir (Turkey); Tuerker, Ali Rehber [Department of Chemistry, Faculty of Science and Arts, Gazi University, 06500 Ankara (Turkey)], E-mail:; Goek, Nuray [Department of Environmental Engineering, Faculty of Engineering, Harran University, 63000 Sanliurfa (Turkey)


    This study presents a column solid phase extraction procedure based on column biosorption of Cu(II), Zn(II) and Pb(II) ions on Penicillium digitatum immobilized on pumice stone. The analytes were determined by flame atomic absorption spectrometry (FAAS). The optimum conditions such as: pH values, amount of solid phase, elution solution and flow rate of sample solution were evaluated for the quantitative recovery of the analytes. The effect of interfering ions on the recovery of the analytes has also been investigated. The recoveries of copper, zinc and lead under the optimum conditions were found to be 97 {+-} 2, 98 {+-} 2 and 98 {+-} 2%, respectively, at 95% confidence level. For the analytes, 50-fold preconcentration was obtained. The analytical detection limits for Cu(II), Zn(II) and Pb(II) were 1.8, 1.3 and 5.8 ng mL{sup -1}, respectively. The proposed procedure was applied for the determination of copper, zinc and lead in dam water, waste water, spring water, parsley and carrot. The accuracy of the procedure was checked by determining copper, zinc and lead in standard reference tea samples (GBW-07605)

  15. the sub-Plinian Greenish Pumice eruption (19,065±105 yr cal BP) of Mount Somma - Vesuvius. Geochemical and textural constrains. (United States)

    Zdanowicz, Géraldine; Boudon, Georges; Balcone-Boissard, Hélène; Cioni, Raffaello; Mundula, Filippo; Orsi, Giovanni; Civetta, Lucia


    Researches are currently focused on large intensity and stable eruptive columns as for Plinian event. But the large variability in deposits issued from sub-Plinian eruptions needs more observations, theoretical and experimental investigations to be better described and enhances criteria of classification and the knowledge on processes at the origin of this unsteadiness of various timescales. Here, we focus on the well-known example of sub-Plinian eruption exhibiting by Mount Somma-Vesuvius: the Greenish Pumice eruption (GP). On the basis of coupled geochemical and textural analyses we investigate the volatile behavior (H2O, CO2 and halogen (F, Cl)) to better constrain (1) the magma reservoir location and pre-eruptive state and (2) the sub-Plinian eruptive style through a detailed study of the degassing processes in relation with the dynamic of the eruptive column. Results evidence that Cl act as a geobarometer for the trachytic-phonolitic melt involved during the eruption indicating that magma reservoir was at 100 MPa (Cl buffer value: 5300 ±130 ppm) and wholly H2O-saturated (pre-eruptive H2O content between 3.8 and 5.2 wt%). The eruption dynamic is clearly explained by open-system degassing processes responsible of the eruptive column instability, correlated to textural heterogeneities of the eruptive products reflecting conduit heterogeneity (smaller diameter and higher horizontal gradient in magma ascent velocity).

  16. From pumice to obsidian: eruptive behaviors that produce tephra-flow dyads. I- The AD1100 Big Glass Mountain eruption at Medicine Lake Volcano (California). (United States)

    Giachetti, T.; Shea, T.; Gonnermann, H. M.; Donnelly-Nolan, J. M.; Ramsey, D. W.


    Associations of tephra and lava flow/domes produced by eruptions involving evolved magmas are a common occurrence in various types of volcanic settings (e.g. Pu'u Wa'awa'a ~114ka, Hawaii; South Mono ~AD625, California; Newberry Big Obsidian flow ~AD700, Oregon; Big Glass Mountain ~AD1100, California; Inyo ~AD1350, California, Chaitén AD2008-2009, Chile; Cordón Caulle AD2011-2012, Chile), ejecting up to a few cubic km of material (tephra+flow/dome). Most, if not all, of these eruptions have in common the paradoxical coexistence of (1) eruptive styles which are inferred to be sustained in nature (subplinian and plinian), with (2) a pulsatory behavior displayed by the resulting fall deposits, and (3) the coeval ejection of vesicular tephra and pyroclastic obsidian. Through two case studies, we explore this apparent set of paradoxes, and their significance in understanding transitions from explosive to effusive behavior. In this first case study (also cf. Leonhardi et al., same session), we present a new detailed stratigraphy of the AD1100 Big Glass Mountain eruption (Medicine Lake Volcano), along with a series of density measurements of tephra collected from several key units identified in the proximal fall deposits. The geochemical character of pumice and obsidian clasts from both the tephra and the obsidian flow is used to trace the origins of the different lithologies involved. We find that tens of waxing and waning cycles occurred during this eruption with at least two protracted phases, and that perhaps the term (sub)plinian may not be completely adequate to describe this particular eruption style. We also review models for the formation of juvenile pyroclastic obsidian in the context of rhyolitic eruptions.

  17. Investigating syn- vs. post-eruption hydration mechanisms of the 2012 Havre submarine explosive eruption: Water speciation analysis of pumiceous rhyolitic glass (United States)

    Mitchell, S. J.; McIntosh, I. M.; Houghton, B. F.; Shea, T.; Carey, R.


    Volatiles preserved in volcanic glass can record the quenching, fragmentation and solubility conditions during an explosive eruption. The VEI-5 2012 eruption of Havre volcano, which produced >1.5 km3 of rhyolite, provides exciting new insight into deep-submarine explosive eruptions. With no direct observations of the eruption at the 900 mbsl vent, the analysis and interpretation of volatile concentrations and speciation within pyroclasts is essential to constraining the eruption style and quenching mechanisms in this understudied environment. We present here the first detailed water speciation data for a large submarine explosive eruption. Water concentrations were measured in pyroclasts from known deposit localities across the Havre stratigraphic succession after ROV collection in 2015. Variations in total water concentration (H2OT) within pyroclasts were determined using high spatial resolution (1 - 2 µm) micro-Raman spectroscopy and water speciation (molecular water (H2Om) and OH) concentrations were measured using Fourier-transform infrared spectroscopy. H2OT concentrations are consistent between Raman and FTIR analysis, ranging from 0.1 - 1.5 wt % H2OT over different stratigraphic units. Comparison of water speciation data with speciation models suggests the Havre pyroclasts experienced secondary, non-magmatic hydration. Since OH is unaltered by secondary hydration, OH concentrations aid in the interpretation of quench depths and inferring of eruption mechanisms. The variability of excess H2Om across units suggests a more complex glass-hydration mechanism during the eruption instead of exclusively post-eruption, low-temperature secondary rehydration. The young sample ages are inconsistent with our current understanding of low-temperature H2O-diffusivity timescales, implying faster secondary rehydration in a higher-temperature submarine setting. We here explore potentially novel syn-eruptive, higher-temperature hydration mechanisms for deep-submarine pumice.

  18. The 23,500 y 14C BP White Pumice Plinian eruption and associated debris avalanche and Tochimilco lava flow of Popocatépetl volcano, México (United States)

    Siebe, Claus; Salinas, Sergio; Arana-Salinas, Lilia; Macías, José Luis; Gardner, James; Bonasia, Rosanna


    The White Pumice (WP) is one of the thickest and most voluminous Plinian fallouts produced by Popocatépetl volcano in central Mexico during the Late Pleistocene-Holocene. Its eruption 23,500 14C y BP (27,800 cal BP) was triggered by the catastrophic failure of the SW flank of the volcano. The resulting debris avalanche was highly mobile reaching 72 km from the cone with an apparent coefficient of friction (L/H) of 0.06. The deposit covers an area of 1200 km2, and has a volume of 10.4 km3. This gigantic landslide, characterized by exceptionally large proximal hummocks (> 400 m) provoked the sudden decompression of the hydrothermal and magmatic systems, which produced an initial blast followed by the rise of a Plinian column that reached an altitude of 33 km. The isopach map allows the recognition of a dispersal axis pointing toward the south, where an area of 2490 km2 was covered by > 10 cm of pumice and ash. The total volume of the pumice fallout was estimated at 1.9 km3 DRE (Dense Rock Equivalent). Pumice clasts are dacitic (62-66 wt.% SiO2, anhydrous basis), highly vesicular (55-88 vol.%) and display a seriate texture with phenocrysts of plagioclase + hornblende + augite + hypersthene + oxides (Ti-magnetite and ilmenite) + apatite. As the eruption advanced, discharge rates became more intermittent and the height of the column fluctuated and finally collapsed, generating pumice-and-ash flows that were emplaced around the volcano. This short but intense activity was followed during subsequent years by rain-induced lahars that reached great distances from the volcano. At the same time, more degassed andesitic-dacitic (61-65 wt.% SiO2) magma was erupted effusively (4.4 km3, DRE) in the new horseshoe-shaped 5 km-wide crater from which the Tochimilco lava flow descended toward the SSE, where it inundated an area of 68 km2 and reached as far as 22 km from its source. Since then, multiple eruptions have reconstructed the summit cone, almost completely obliterating the

  19. Nature and composition of interbedded marine basaltic pumice in the ˜52-50 Ma Vastan lignite sequence, western India: Implication for Early Eocene MORB volcanism offshore Arabian Sea (United States)

    Sensarma, Sarajit; Singh, Hukam; Rana, R. S.; Paul, Debajyoti; Sahni, Ashok


    The recognition of pyroclasts preserved in sedimentary environments far from its source is uncommon. We here describe occurrences of several centimetres-thick discontinuous basaltic pumice lenses occurring within the Early Eocene Vastan lignite mine sedimentary sequence, western India at two different levels - one at ˜5 m and the other at 10 m above a biostratigraphically constrained 52 Ma old marker level postdating the Deccan Volcanism. These sections have received global attention as they record mammalian and plant radiations. We infer the repetitive occurrence of pumice have been sourced from a ˜52-50 Ma MORB related to sea-floor spreading in the western Arabian Sea, most plausibly along the Carlsberg Ridge. Pyroclasts have skeletal plagioclase with horsetail morphologies ± pyroxene ± Fe-Ti oxide euhedral crystals, and typically comprise of circular polymodal (radii ≤10 to ≥30 μm), non-coalescing microvesicles (>40-60%). The pumice have undergone considerable syngenetic alteration during oceanic transport and post-burial digenesis, and are a composite mixture of Fe-Mn-rich clay and hydrated altered basaltic glass (palagonite). The Fe-Mn-rich clay is extremely low in SiO 2, Al 2 O 3, TiO 2, MgO, alkalies and REE, but very high in Fe 2 O 3, MnO, P, Ba, Sr contents, and palagonitization involved significant loss of SiO 2, Al 2 O 3, MgO and variable gain in Fe 2 O 3, TiO 2, Ni, V, Zr, Zn and REE. Bubble initiation to growth in the ascending basaltic magma (liquidus ˜1200-1250 ∘C) may have occured in ˜3 hr. Short-distance transport, non-connected vesicles, deposition in inner shelf to more confined lagoonal condition in the Early Eocene and quick burial helped preservation of the pumice in Vastan. Early Eocene Arabian Sea volcanism thus might have been an additional source to marginal sediments along the passive margin of western India.


    Institute of Scientific and Technical Information of China (English)

    许建东; 于红梅; 赵波


    在长白山天池火口天文峰内壁发育数十m厚的爆炸式喷发堆积物,颜色各异.其中1套规模较大的黄色中弱熔结的粗粒浮岩空降堆积,堆积物碎屑粒径大,气孔大量发育,含有大粒径粗面岩岩块.文中对采于该套黄色堆积物的样品进行了全岩成分和显微结构特征分析,并与“千年大喷发”的空降浮岩进行了对比.研究结果表明:1)黄色浮岩与千年喷发的浮岩一样,属于碱性流纹岩,比千年喷发的灰白色浮岩略偏基性,可能由同一岩浆演化而来;2)黄色浮岩呈泡沫状,由不同大小的气孔、气孔壁和少量斑晶组成,部分较大的圆形气孔沿斑晶周围发育,呈串珠状排列,流动特征明显,黄色浮岩的斑晶类型和气孔结构与千年喷发的灰白色浮岩类似;3)已有扫描电镜和X射线衍射分析结果显示黄色浮岩中的长石参数与其他浮岩明显不同,可能是独立火山喷发事件的产物.上述岩石学证据表明,该套黄色堆积物是火山爆炸式喷发作用形成的浮岩空降堆积.%A series of deposits with tens of meters in thickness and in black,grey and yellow colors,from explosive eruptions in the Holocene,are developed at Tianwen peak,the north summit of Tianchi caldera of Changbaishan volcano.Among the deposits,a relatively large scale unit in yellow color,socalled "yellow pumice" by the previous studies,is characterized by coarse tephra and well-developed pores with large-sized trachyte blocks.In this study,we analyzed the petrographic and micro-textural features of the yellow pumice,as well as the grey pumice which is believed to be produced by the millennium eruption in 946 AD.Our results indicate that:1)the yellow pumice can be classified into alkaline rhyolite as like the grey pumice,but is slightly more basaltic than the grey pumice,suggesting that they all are probably from the identical magma source; 2)remarkably similar as the grey pumice in texture,the yellow

  1. Dynamics and evolution of the plumbing system source of three major pumiceous eruptions in Dominica (Lesser Antilles): crystal system analysis and diffusion modeling on orthopyroxenes. (United States)

    Solaro, Clara; Balcone-Boissard, Hélène; Boudon, Georges; Martel, Caroline; Morgan, Daniel


    Modern volcanology studies have demonstrated that the crystal "cargo" of magmas can be used to unravel the dynamics of magmatic plumbing systems and constrain timescales of magmatic processes. Specifically, several studies focusing on large silicic eruptions (10 to 100 km3 DRE/eruption) have shown that crystal populations may be rapidly re-mobilized over short timescales of decades to centuries prior to eruption, making these systems more dynamic than previously believed. We present a petrological study of three, major, pumiceous, dacitic eruptions produced on Dominica (Lesser Antilles Arc) in the last 50ky: Layou (~50ka), Roseau (~30ka) and Rosalie (~20ka). We combine crystal texture and chemical analyses with modeling of diffusional relaxation of chemical gradients in orthopyroxene crystals. A systems analysis approach is used to decipher remobilization processes of crystals before each eruption, and to map the plumbing system evolution over time. Timescales are calculated by Fe2+-Mg interdiffusion modeling on selected orthopyroxenes, by inter-calibration of high resolution BSE-images and EMPA analysis profiles. Textural analyses show that for each of the three eruptions about 80-85% of orthopyroxenes are unzoned, while about 15-20% exhibit normal, reverse and multiple zoning. Systems analysis of the zoned crystals reveals the presence of four different magmatic environments (ME): En46-51(ME1), En52-53(ME2), En54-58(ME3) and En59-63(ME4). During the eruptive history, the main magmatic environment, represented by the 80% of unzoned orthopyroxenes, moves from ME2 (for Layou and Roseau) to ME3 (for Rosalie), indicating a shift of the system to less-evolved compositions. For all eruptions, a main crystal transfer pathway can be identified between ME2-ME3, describing a progressive sinking of crystals from the main environment En52-53(ME2) to the less-evolved En54-58 (ME3), which receives crystals, and, by the Rosalie eruption, becomes the volumetrically most

  2. Microstructural Characteristics of the Holocene Pumice Erupted from Changbaishan Tianchi Volcano and Their Volcanological Implications%长白山天池火山全新世浮岩显微结构特征及其火山学意义

    Institute of Scientific and Technical Information of China (English)

    于红梅; 吴建平; 许建东; 林传勇; 史兰斌; 陈孝德


    In this paper,the component and microstructure of pumices from three times explosive eruptions in Holocene (5 000 a B.P.eruption,millennium eruption and the late eruption) of Changbaishan Tianchi volcano were quantitative studied in detail.The results show that,pumices from 5 000 a B.P.eruption and the millennium eruption are all pantellerite in composition,but those from the millennium eruption are more acid than those from 5 000 a B.P.eruption.The pumice from the late eruption is high-potassium trachyte in composition.The pumice from three times eruptions composes of vesicles with different sizes,vesicle wall and a small amount of phenocrysts (< 15%).The yellow pumice from 5 000 a B.P.eruption is small,and has the smallest vesicles (about 1 μm) but the largest number density (4.23 × 1016/m3).The sizes and numbers of vesicles in gray pumice from 5 000 a B.P.eruption and gray white pumice from millennium eruption are relatively similar,the smallest vesicles are several micrometers,and the number densities are (1.76-3.25) × 1015/m3.The vesicles in black pumice from the late eruption enlarge to centimeters,and are over 10 μm in size.The vesicle number (3.68 × 1014/m3) decreases and vesicle walls thicken.According to the components and vesicle number,such parameters as decompression rates,the height of eruption column and magma discharge rate have been obtained.%对长白山天池火山全新世3期爆炸式喷发(5000a前、千年大喷发和晚期喷发)产生的浮岩进行了详细的成分和结构定量研究.研究发现:5 000 a前和千年大喷发的浮岩均为碱流岩,后者略偏酸性,晚期喷发的黑色浮岩为高钾粗面岩.3期浮岩均由不同大小的气孔、气孔壁及少量的斑晶(<15%)组成.5000a前喷发的黄色浮岩气孔比较细密,最小气孔约为1 μm,气孔数量最多,为4.23×1016个/m3.5000a前喷发的灰色浮岩和千年大喷发的灰白色浮岩气孔大小和数量比较接近,最小气孔几

  3. Effect of ions in water on the catalytic ozonation by pumice supported zinc%水中常见离子对锌改性浮石催化臭氧化有机物效能的影响

    Institute of Scientific and Technical Information of China (English)

    袁磊; 杨帆; 倪红伟


    采用锌改性浮石为催化剂,催化臭氧氧化难降解的硝基类卤代芳香族有机化合物-对氯硝基苯,对水中常见无机离子对催化臭氧氧化去除水中微量对氯硝基苯的效能进行了比较。实验结果表明,水中阳离子Na+和 K+对去除效能影响较小,Ca2+和 Mg2+对去除效能略有促进作用。阴离子对去除效能影响较为明显,均有一定抑制作用,NO3-和Cl-影响不明显,其中以SO42-和PO43-的抑制影响最大。%The catalytic ozonation of p-chloronitrobenzene (p-CNB) in an aqueous solution using modification pumice as the catalysts was investigated. The effects of NO3-, Na+, and K+ on the catalytic ozonation of p-CNB can be ignored. Degradation effi-ciency was slightly promoted in the presence of Ca2+ and Mg2+. The ozonation of p-CNB was slightly inhibited by the high con-centration of Cl-. The removal efficiency of p-CNB decreased in the presence of SO42-, given that the hydroxyl inhibitors PO43- can significantly inhibit the catalytic degradation of p-CNB.

  4. From pumice to obsidian: eruptive behaviors that produce tephra-flow dyads. II- The 114ka trachyte eruption at Pu'u Wa'awa'a (Hawai'i). (United States)

    Shea, T.; Leonhardi, T. C.; Giachetti, T.; Larsen, J. F.; Lindoo, A. N.


    Associations of tephra and lava flow/domes produced by eruptions involving evolved magmas are a common occurrence in various types of volcanic settings (e.g. Pu'u Wa'awa'a ~114ka, Hawaii; South Mono ~AD625, California; Newberry Big Obsidian flow ~AD700, Oregon; Big Glass Mountain ~AD1100, California; Inyo ~AD1350, California, Chaitén AD2008-2009, Chile; Cordón Caulle AD2011-2012, Chile), ejecting up to a few cubic km of material (tephra+flow/dome). Most, if not all, of these eruptions have in common the paradoxical coexistence of (1) eruptive styles which are inferred to be sustained in nature (subplinian and plinian), with (2) a pulsatory behavior displayed by the resulting fall deposits, and (3) the coeval ejection of vesicular tephra and pyroclastic obsidian. Through two case studies, we explore this apparent set of paradoxes, and their significance in understanding transitions from explosive to effusive behavior. In this second case study (also cf. Shea et al., same session), we present new field, textural and geochemical data pertaining to the 114ka Pu'u Wa'awa'a trachyte eruption in Hawai'i. This large volume (>5 km3) event produced both a tephra cone (~1.6 km in diameter) and a thick (>250 m) lava flow, which have been largely covered by the more recent basaltic Mauna Loa and Hualalai lava flows. The trachyte tephra contains juvenile material displaying a large textural variety (pumice, scoria, obsidian, microcrystalline trachyte and banded-clasts), which can be linked with the extent of degassing and the formation of feldspar microlites. Notably, the abundance of microlites can be used to reconstruct an ascent and devolatilization history that accounts for all the seemingly contradictory observations.

  5. Pumices from the Central Indian Ocean Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Iyer, S.D.

    A better understanding of submarine volcanisms that result in pyroclastics is of universal importance for paleotectonic reconstruction, crustal growth estimates and location of volcanisms throughout the earth's history. Of the volcanogenic...

  6. wet oxidation of maleic acid by a pumice supported copper

    African Journals Online (AJOL)


    materials were tested in a wet oxidation of maleic acid using air or hydrogen peroxide as an oxidant. Results ... textile, pharmaceuticals, paper and pulp .... Fourier Transform Infrared (FTIR). The ... to analysis and then run at room temperature.

  7. Characterization and stability studies of emulsion systems containing pumice


    Marilene Estanqueiro; Jaime Conceição; Maria Helena Amaral; Delfim Santos; João Baptista Silva; José Manuel Sousa Lobo


    Emulsions are the most common form of skin care products. However, these systems may exhibit some instability. Therefore, when developing emulsions for topical application it is interesting to verify whether they have suitable physical and mechanical characteristics and further assess their stability. The aim of this work was to study the stability of emulsion systems, which varied in the proportion of the emulsifying agent cetearyl alcohol (and) sodium lauryl sulfate (and) sodium cetearyl su...

  8. Investigation of Phenol Removal from Aqueous Solutions Using Copper-Impregnated Pumice


    A.R. Rahmani; Gh. Asgari; F. Barjasteh Asgari; E. Hedayati Kamran; F. Alijani


    Introduction & Objectives: Recently, treatment of industrial wastewaters has attracted much attention of many governments and also environmental experts. Basically, these wastewaters are polluted due to the different contaminants such as dyes, halogenated hydrocarbons, phenolic compounds etc. Among these pollutants, phenols are widely used in petroleum, petrochemical, coal production and pharmaceutical industries. There are several methods for removing phenol from water including adsorption, ...

  9. Developing resilient ponderosa pine forests with mechanical thinning and prescribed fire in central Oregon's pumice region (United States)

    Matt D. Busse; P.H. Cochran; William E. Hopkins; William H. Johnson; Gregg M. Riegel; Gary O. Fiddler; Alice W. Ratcliff; Carol J. Shestak


    Thinning and prescribed burning are common management practices for reducing fuel buildup in ponderosa pine forests. However, it is not well understood if their combined use is required to lower wildfire risk and to help restore natural ecological function. We compared 16 treatment combinations of thinning, prescribed fire, and slash retention for two decades...

  10. Studies on Pumice Lightweight Aggregate Concrete with Quarry Dust Using Mathematical Modeling Aid of ACO Techniques

    Directory of Open Access Journals (Sweden)

    J. Rex


    Full Text Available The lightweight aggregate is an aggregate that weighs less than the usual rock aggregate and the quarry dust is a rock particle used in the concrete for the experimentation. The significant intention of the proposed technique is to frame a mathematical modeling with the aid of the optimization techniques. The mathematical modeling is done by minimizing the cost and time consumed in the case of extension of the real time experiment. The proposed mathematical modeling is utilized to predict four output parameters such as compressive strength (Mpa, split tensile strength (Mpa, flexural strength (Mpa, and deflection (in mm. Here, the modeling is carried out with three different optimization techniques like genetic algorithm (GA, particle swarm optimization (PSO, and ant colony optimization (ACO with 80% of data from experiment utilized for the training and the remaining 20% for the validation. Finally, while testing, the error value is minimized and the performance obtained in the ACO for the parameters such as compressive strength, split tensile strength, flexural strength, and deflection is 91%, 98%, 87%, and 94% of predicted values, respectively, in the mathematical modeling.

  11. Hydrothermal signature in ferromanganese oxide coatings on pumice from the Central Indian Ocean Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Kalangutkar, N.G.; Iyer, S.D.; Mascarenhas-Pereira, M.B.L.; Nath, B.N.

    at 72–80°E, 9–16°S during numerous cruises spanning the time period 1981–1996. In several cases, the samples were taken close to seamounts or fracture zones, and have up to 5-mm-thick FeMn oxides. Recently, Pattan et al (2013) reported the origin... of fault zones and seamounts located along N–S trending propagative fractures. The density of seamounts is higher near the 79°E fault zone, where the seamounts have an average height of 500 m and are multi-peaked, with an elongated base as well...

  12. Ectomycorrhizal communities of ponderosa pine and lodgepole pine in the south-central Oregon pumice zone. (United States)

    Garcia, Maria O; Smith, Jane E; Luoma, Daniel L; Jones, Melanie D


    Forest ecosystems of the Pacific Northwest of the USA are changing as a result of climate change. Specifically, rise of global temperatures, decline of winter precipitation, earlier loss of snowpack, and increased summer drought are altering the range of Pinus contorta. Simultaneously, flux in environmental conditions within the historic P. contorta range may facilitate the encroachment of P. ponderosa into P. contorta territory. Furthermore, successful pine species migration may be constrained by the distribution or co-migration of ectomycorrhizal fungi (EMF). Knowledge of the linkages among soil fungal diversity, community structure, and environmental factors is critical to understanding the organization and stability of pine ecosystems. The objectives of this study were to establish a foundational knowledge of the EMF communities of P. ponderosa and P. contorta in the Deschutes National Forest, OR, USA, and to examine soil characteristics associated with community composition. We examined EMF root tips of P. ponderosa and P. contorta in soil cores and conducted soil chemistry analysis for P. ponderosa cores. Results indicate that Cenococcum geophilum, Rhizopogon salebrosus, and Inocybe flocculosa were dominant in both P. contorta and P. ponderosa soil cores. Rhizopogon spp. were ubiquitous in P. ponderosa cores. There was no significant difference in the species composition of EMF communities of P. ponderosa and P. contorta. Ordination analysis of P. ponderosa soils suggested that soil pH, plant-available phosphorus (Bray), total phosphorus (P), carbon (C), mineralizable nitrogen (N), ammonium (NH4), and nitrate (NO3) are driving EMF community composition in P. ponderosa stands. We found a significant linear relationship between EMF species richness and mineralizable N. In conclusion, P. ponderosa and P. contorta, within the Deschutes National Forest, share the same dominant EMF species, which implies that P. ponderosa may be able to successfully establish within the historic P. contorta range and dominant EMF assemblages may be conserved.

  13. A note on chemical composition and origin of ferromanganese oxide coated and uncoated pumice samples from central Indian Ocean basin

    Digital Repository Service at National Institute of Oceanography (India)

    Pattan, J.N.; Parthiban, G.; Moraes, C.; Rajalakshmi, R.; Lekshmi, S.; Athira, S.; JaiSankar, S.

    other suggesting a same source. Tectonomagmatic discrimination diagrams (Nb vs Y: Yb vs. Ta), triangular plot (TiO2-Y) and High Field Strength Element ratios (La/Ta-25; Ta/Hf-0.2; Nb/Ta-9; Zr/Nb-22 and Ba/Ta-1084) indicate volcanic arc origin...

  14. Comparison of shear bond strength of self-etching fluoride releasing adhesives with and without pumice prophylaxis

    Directory of Open Access Journals (Sweden)

    V R Shobbana Devi


    Conclusions: Fluoride releasing adhesives combined with antibacterial monomer can play a vital role in reducing white spot lesions by enhancing the cariostatic effect especially in noncompliant\\medically compromised patients.

  15. Petrology and geochemistry of Late Holocene felsic magmas from Rungwe volcano (Tanzania), with implications for trachytic Rungwe Pumice eruption dynamics

    NARCIS (Netherlands)

    Fontijn, K.; Elburg, M.A.; Nikogosian, I.K.|info:eu-repo/dai/nl/323258255; van Bergen, M.J.|info:eu-repo/dai/nl/07009277X; Ernst, G.G.J.


    Rungwe in southern Tanzania is an active volcanic centre in the East African Rift System, characterised by Plinian-style explosive eruptions of metaluminous to slightly peralkaline trachytic silica-undersaturated magmas during its late Holocene history. Variations in whole-rock major and trace eleme

  16. Effect of the use nickeliferous laterite and pumice as additives in the performance and durability of the Portland cement

    Directory of Open Access Journals (Sweden)

    María Carolina Rueda-Gualdrón


    Full Text Available En este trabajo se evalúa el comportamiento puzolánico de la laterita niquelífera de Cerromatoso (Córdoba y la pumita de Cemex (Boyacá en la preparación de morteros según normas NTC para agregados finos. Los morteros se prepararon con adiciones de 2,5%, 5% y 10% como sustitutos del cemento Portland tipo I, los cuales fueron sometidos a ensayos de resistencia mecánica antes y después de ser sometidos a ambientes extremos (altas temperaturas y ataques químicos como H2 SO4 y MgSO4 . Los resultados demuestran cómo estos materiales alternativos incrementan o disminuyen su grado de puzolanidad, así como el efecto de estos aditivos al interior de las mezclas de mortero en el tiempo, demostrando propiedades similares con relación a los morteros preparados con cemento Portland tipo I. Por lo tanto, los morteros tienen una respuesta aceptable ante las condiciones evaluadas, aunque es posible mejorar su desempeño y durabilidad, colaborando no solo con el ahorro energético en la producción del cemento Portland tipo I sino también en el uso de aditivos alternativos que permitan mitigar el impacto ambiental provocado por la industria cementera.

  17. Petrology and geochemistry of Late Holocene felsic magmas from Rungwe volcano (Tanzania), with implications for trachytic Rungwe Pumice eruption dynamics

    NARCIS (Netherlands)

    Fontijn, K.; Elburg, M.A.; Nikogosian, I.K.; van Bergen, M.J.; Ernst, G.G.J.


    Rungwe in southern Tanzania is an active volcanic centre in the East African Rift System, characterised by Plinian-style explosive eruptions of metaluminous to slightly peralkaline trachytic silica-undersaturated magmas during its late Holocene history. Variations in whole-rock major and trace eleme


    Institute of Scientific and Technical Information of China (English)

    李燕; 申向东



  19. Time scales of magma recharge and crystal growth rate determined from Mg and Ti zoning in plagioclase phenocrysts from the Upper Toluca Pumice, Mexico (United States)

    Dohmen, Ralf; Smith, Victoria C.; Arce, Jose Luis; Blundy, Jonathan D.


    Major and trace element zoning in plagioclase phenocrysts has the potential to stores information on the temporal evolution of the chemical environment during crystal growth, i.e. the surrounding melt composition as well as the intensive parameters temperature (T) and pressure (P), provided that equilibrium partitioning accompanies growth. However, the problem is complicated by the fact that diffusion of mobile elements changes their initial concentrations due to re-equilibration with the surrounding melt at later stages, making estimation of the pre-diffusive element profiles fraught with uncertainty. Here we present a new approach that combines the information from immobile (e.g., Ca, Ti) and mobile (e.g., Mg) elements in plagioclase to unravel the growth history and time scales of magma recharge events from the 10.5 ka Upper Toluca plinian eruption of Nevado de Toluca volcano, Mexico. Since trace elements are less sensitive to intensive parameters their variations in plagioclase phenocrysts have been used to identify open-system processes in silicic systems [1]. These phenocrysts preserve complex element patterns, such as oscillatory zoning and overgrowths, indicating multiple magma recharging events. Based on available diffusion data major elements and, for example, the trace element Ba, are effectively unchanged since crystallization, but the mobility of Mg [2] is large enough to alter the initial concentration at later growth stages. We made attempts to model the Mg zoning using two endmember cases for the growth history of the plagioclase. In the model the growth rate can either be constant until the final crystal diameter is reached or involve various short growth stages with diffusion relaxation breaks in-between. The corresponding moving boundary problem of the diffusion equation was solved numerically using the method of finite differences and a front-tracking method [3]. A particular challenge of the modelling is to estimate the initial Mg concentration after an incremental growth step since the melt composition is unknown during each growth stage. We have tried two different approaches: In each case three calculation steps are involved, which are based on the assumption that Ti and the anorthite (An) content were not affected by diffusion and both correlated linearly with Mg in the plagioclase during growth. Both methods give a very similar result for the initial Mg profile, provided that the plagioclase-melt Mg partition coefficient is constant (independent of T and An) and of the order of 0.03 +/-0.01, which is consistent with the data of Bindeman et al. (1998) [4] and unpublished data of Blundy & Wood [5], and with the fact that the predicted MgO contents in the melt are consistent with observed melt inclusions in UTP rocks [1]. Our first modelling results are, in general, able to simulate the final observed Mg concentration profiles, but the time scale obtained is actually less sensitive to the choice for the growth history (constant or one-step growth). The time scales are on the order of hundred years to several thousand years subject to the assumption of Costa et al (2003) [6] that the diffusion coefficient of Mg has the same dependence on An as Sr, which has to be experimentally validated. Temperature was taken from two-oxide thermometry (830 °C). Other factors of uncertainty for the modelling are less significant (e.g., anisotropy) and lower than an order of magnitude. Our estimated magma residence times are consistent with steady refilling of the Toluca magma chamber since the previous eruption ~12 kyr at a rate of ≥ 6.e6 m3/yr. [1] Smith et al. (2009), J. Petrol. 50, 405. [2] LaTourette & Wasserburg (1998) Earth Plant. Sci. Let. 158, 91. [3] Crank (1975) Oxford Sci. Publ. 414p. [4] Bindeman et al. (1998), Geochim. Cosmochim. Acta 62, 1175. [5] Blundy & Wood, Nature, 372, 452. [6] Costa et al. , (2003), Geochim. Cosmochim. Acta 67, 2189.

  20. 浮石催化臭氧化去除水中pCNB的效能研究%Ozonation Catalyzed by Pumice for the Degradation of p-chloronitrobenzene in Aqueous Solution

    Institute of Scientific and Technical Information of China (English)

    袁磊; 张继舟; 王立民; 朱道光



  1. Comparison between phosphoric acid and hydrochloric acid in microabrasion technique for the treatment of dental fluorosis


    Mahshid Mohammadi Bassir; Golnaz Bagheri


    Purpose: To compare the effectiveness of phosphoric acid (H 3 PO 4 )-pumice compound with conventional hydrochloric acid (HCl)-pumice compound in treating different severities of dental fluorosis with the microabrasion technique. Materials and Methods: Sixty-seven anterior teeth from seven patients with different severities of dental fluorosis were treated. In each patient, half of the teeth were treated with HCl-pumice compound and the other half with H 3 PO 4 -pumice compound (split-mou...

  2. Petrology of ocean floor rocks from Central Indian Ocean basin

    Digital Repository Service at National Institute of Oceanography (India)

    Iyer, S.D.; Karisiddaiah, S.M.

    on the pumice is also a possibility IQ. The influence ofsubmarine volca noes as sources for pumice may be possible for CIOO samples, similar to those reported for the Atlantic Ocean 20 . It is envisaged that the uprising magma was basic and highly fluid...

  3. Conduciveness of different soilless growing media to Pythium root and crown rot of cucumber under near-commercial conditions

    NARCIS (Netherlands)

    Gaag, van der D.J.; Wever, G.


    Substrates made from rockwool, coir dust, pumice and perlite were compared for conduciveness to Pythium root and crown rot in cucumber under near-commercial conditions. Rockwool slabs of 7 cm height were more conducive to the Pythium disease than coir dust slabs, pumice or perlite under these condit

  4. Conduit enlargement during the precursory Plinian eruption of Aira Caldera, Japan (United States)

    Geshi, Nobuo; Miyabuchi, Yasuo


    Increase in magma flux as the result of conduit enlargement is one of the key processes that triggered caldera collapse and eruption of the Ito ignimbrite from Aira Caldera at ~29 ka. We examine the total volume of the pumice fall deposit, vertical variations in grain size of pumice, and the lithic content in the Osumi pumice deposit to investigate the trigger for caldera collapse. Wider distribution of the later-stage unit and the upward coarsening of grain size throughout the Osumi pumice fall deposit indicate an increase in magma discharge toward the onset of collapse. The total volume of lithic fragments in the Osumi pumice fall deposit is estimated as ~1.6 km3, based on the lithic content in several representative outcrops and the total volume of the Osumi pumice fall deposit. The lithic fragments in the Osumi pumice fall deposit indicate intense mechanical erosion of the conduit during the Plinian eruption prior to caldera collapse. Caldera collapse requires decompression of the magma chamber by withdrawal of magma; effective enlargement of the conduit diameter during precursory eruptive phases is one of the important processes that subsequently allow the rapid discharge of a large volume of magma, which in turn facilitates decompression of the reservoir and induces caldera collapse.

  5. Influence of calcium and silicon supplementation into Pleurotus ostreatus substrates on quality of fresh and canned mushrooms. (United States)

    Thongsook, T; Kongbangkerd, T


    Supplements of gypsum (calcium source), pumice (silicon source) and pumice sulfate (silicon and calcium source) into substrates for oyster mushrooms (Pleurotus ostreatus) were searched for their effects on production as well as qualities of fresh and canned mushrooms. The addition of pumice up to 30% had no effect on total yield, size distribution and cap diameters. The supplementation of gypsum at 10% decreased the total yield; and although gypsum at 5% did not affect total yield, the treatment increased the proportion of large-sized caps. High content (>10%) of pumice sulfate resulted in the lower yield. Calcium and silicon contents in the fruit bodies were not influenced by supplementations. The centrifugal drip loss values and solid content of fresh mushrooms, and the percentage of weight gained and firmness of canned mushrooms, cultivated in substrates supplemented with gypsum, pumice and pumice sulfate were significantly (p≤0.05) higher than those of the control. Scanning electron micrographs revealed the more compacted hyphae of mushroom stalks supplemented with silicon and/or calcium after heat treatment, compared to the control. Supplementation of P. ostreatus substrates with 20% pumice was the most practical treatment because it showed no effect on yield and the most cost-effective.

  6. Relationship between eruptive style and vesicularity of juvenile clasts during eruptive episode A of Towada Volcano, Northeast Japan (United States)

    Hiroi, Yoshimi; Miyamoto, Tsuyoshi


    It has been reported that juvenile pumice lapilli found in plinian eruptions have high vesicularity, while those found in phreatoplinian eruptions have low vesicularity. However, juvenile glass shards from phreatoplinian eruptions consist of large, expanded bubbles such as bubble wall-type glass. These glass shards seem to possess high vesicularity, unlike the pumice lapilli. This study examines the factors causing this difference, especially focusing on the temporal variations in the vesicularity of the juvenile pyroclasts from eruptive episode A of Towada Volcano, Northeast Japan. This examination was conducted through four analyses: density measurements of pumice lapilli, thin section texture classification of pumice lapilli, classification of glass shards, and surface texture classification of pumice lapilli. Further, pumice lapilli from plinian eruptions have a low density, and those from phreatoplinian eruptions are characterized by high density. The density of the pumice lapilli depends on the eruption style and is hence determined after the eruption. A progressive increase in the amount of large bubbles is observed in glass shards ejected during an eruptive magmatic to phreatomagmatic sequence. Because it does not hinge on the eruptive style, it is assumed that the vesicularity of the glass shards is kept from the conduit before contact with water, especially on fragmentation by magma vesiculation in the conduit. The surfaces of the pumice lapilli show a similar increase in vesicularity with time as glass shards. However, this increase is not successive throughout, but decreases temporarily at the phreatomagmatic stage of the eruption, as in the case of density. This indicates that the successive bubble growth continues within the pumice, and additional vesiculation is superposed when the magmatic eruption comes into contact with water. Because of this, different juvenile clasts exhibit different vesicularities upon cooling. Interestingly, magma

  7. New occurrence of Youngest Toba Tuff in abyssal sediments of the Central Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Pattan, J.N.; Shane, P.; Banakar, V.K.

    Volcanic glass and pumice found in siliceous abyssal sediments of the Central Indian Basin, south of the Equator, have previously been assigned various origins including intra-basin volcanism, Indonesian arc, and Krakatau. Rhyolitic glass shards...

  8. suitability of murram for phosphorus sorption in constructed wetlands

    African Journals Online (AJOL)


    significantly influence phosphorus sorption on 1-2mm grain. Moshi Pumice has high ... properties of the substrate (Fe, Mg, Al-, Ca-minerals, specific surface area and .... incubator (WTB binder type, model 720, German) for twenty-four hours.

  9. Textural and geochemical constraints on eruptive style of the 79AD eruption at Vesuvius (United States)

    Balcone-Boissard, Hélène; Boudon, Georges; Villemant, Benoît.


    The 79AD eruption of Vesuvius, also known as the "Pompeii eruption", is the reference for one of the explosive eruptive styles, the plinian-type eruption. The eruption involved H2O-rich phonolitic magmas and is commonly divided into three phases: an initial phreatomagmatic phase, followed by a plinian event which produced a thick pumice fallout deposit and a final phase that was dominated by numerous column-collapse events. During the plinian phase, a first white pumice fallout was produced from a high steady eruptive column, followed by a grey pumice fallout originated by an oscillatory eruptive column with several partial column collapse events. This study focuses on the pumice fallout deposits, sampled in a proximal thick section, at the Terzigno quarry, 6 km southeast of the present crater. In order to constrain the degassing processes and the eruptive dynamics, major element compositions, residual volatile contents (H2O, Cl) and textural characteristics (vesicularity and microcrystallinity) were studied. A previous study that we performed on the pre-eruptive Cl content has shown that Cl may be used as an indicator of magma saturation with Cl-rich fluids and of pre-eruptive pressures. Cl contents measured in melt inclusions show that only the white pumice and the upper part of the grey pumice magma were H2O saturated prior eruption. Large variations in residual volatile contents exist between the different eruptive units and textural features strongly differ between white and grey pumice clasts but also within the grey pumice clasts. The degassing processes were thus highly heterogeneous: the white pumice eruptive units represent a typical closed-system degassing evolution whereas the first grey pumice one, stored in the same pre-eruptive saturation conditions, follows a particular open-system degassing evolution. Here we propose a new model of the 79AD eruption where pre-eruptive conditions (H2O saturation, magma temperature and viscosity) are the critical

  10. Influence of particle density on flow behavior and deposit architecture of concentrated pyroclastic density currents over a break in slope: Insights from laboratory experiments (United States)

    Rodriguez-Sedano, L. A.; Sarocchi, D.; Sulpizio, R.; Borselli, L.; Campos, G.; Moreno Chavez, G.


    Geological granular flows are highly complex, gravity-driven phenomena whose different behaviors depend on the mechanical properties, density and granulometric distributions of the constituent materials. Years of research have produced significant advances in understanding transport and deposition processes in granular flows. However, the role and effects of clast densities and density contrast in a granular flow are still not fully understood. In this paper we show the effect that pumice has on dry granular flows; specifically on flow velocity and longitudinal segregation of the deposits. Our work confirms, by experimental results, field observations on pumice/lithic segregation and longer pumice runout. We report results of velocity decay and deposit architecture for a granular flow passing over a break in slope (from 38° to 4° inclination). The 30 experimental runs were carried out in a five-meter long laboratory flume equipped with a series of sensors that include laser gates and high-speed cameras (400 fps). We used two polydisperse mixtures of dacitic lithics and rhyolitic pumice in varying amounts, with Weibull and Gaussian particle size distributions. The pumice/lithic ratio changes the flow response passing over a break in slope. This effect is particularly evident starting from 10% of pumice volume into the flow mixture, independently of its granulometric distribution. Runout relates to mass following a power law, with an exponent close 0.2. The experiments confirm that pumice segregation affects polydispersed mixtures, similarly to what has been observed in real field deposits, where density decoupling produces lithic-enriched proximal areas and pumice-enriched distal areas. The results obtained prove that the presence of low-density materials in a dense granular flow has a strong influence on its behavior.

  11. Resistivity, ESR, and Radiation Shielding Properties of the Volcanic Rock Materials

    Directory of Open Access Journals (Sweden)

    Çiğdem Nuhoğlu


    Full Text Available Pumices have been used in cement, concrete, brick, and ceramic industries as an additive and aggregate material. It will be important to study pumice types by using a different tool as EPR which is a new technique for related material to be used for industrial aims. Electron spin resonance (ESR spectra of the pumice types were taken by EMX-type spectrometer. Also, the current-voltage (I-V and surface resistivity probe stand of the thin films was studied using a four-point probe measurements. The relationship between radiation shielding properties of the pumice samples and their surface resistivity, chemical, and electrokinetic properties was evaluated using simple regression analysis. Simple regression analysis indicated a strong correlation between surface resistivity and density and SiO2, Fe2O3, CaO, MgO, and TiO2 content of pumice samples in this study. It is found that a correlation between determined g-factor by EPR spectroscopy and radiation shielding is established for pumice samples.

  12. An unusual syn-eruptive bimodal eruption: The Holocene Cuicuiltic Member at Los Humeros caldera, Mexico (United States)

    Dávila-Harris, Pablo; Carrasco-Núñez, Gerardo


    The Cuicuiltic Member (CM) at Los Humeros Caldera, eastern Mexican Volcanic Belt is a Holocene (6.4 ka B.P.) succession of alternated fallout deposits of contrasting composition (trachydacite pumice and basaltic andesite scoria). The CM covers approximately 250 km2 on its proximal facies and its thickness ranges from 1.5 m to 8.0 m. It postdates two caldera-forming ignimbrites (Xaltipan and Zaragoza) and numerous Plinian successions. It is subdivided in 9 units (C1 to C9) according to its textural and chemical characteristics. Sub-horizontal, topography-draping layers of trachydacite pumice lapilli, andesitic pumice lapilli and basaltic-andesite scoria lapilli with sporadic one-meter blocks are common lithofacies. The base is formed by coarse trachydacite pumice lapilli (C1 and C2), overlain by a layer with banded pumice (C3). Thin layers of ash and ash-tuff are intermittent on lower units, whilst continuous at the base of C4. The middle units, C4 and C6 are basaltic-andesite pumice, and scoria lapilli to blocks; C5 is in-between the two mafic units and it is represented by a layer of pale grey pumice lapilli. Units C7 and C8 are a mixture of white trachydacite pumice, scoria lapilli and banded pumice. The uppermost layer, C9, is a brown to grey andesitic pumice lapilli. Extensive fieldwork allowed a close and reliable correlation of layers that helps to understand the complexity of stratigraphic relations and sources for those layers. The distribution of these units is varied across the caldera, with the trachydacite layers dispersal from the centre towards the NW, whilst the andesitic units have maximum thicknesses over the SE and NE sectors of the caldera. Isopach and isopleth maps, combined with detailed mapping of near-vent spatter facies, orientation of local bomb sags and variation of mean clasts size for some layers were very useful to determine the vent location, particularly for the andesitic-basaltic layers.

  13. Effects of thermal quenching on the breakup of pyroclasts (United States)

    Patel, A.; Manga, M.; Carey, R. J.; Degruyter, W.; Dufek, J.


    It is often assumed that magma fragments when it contacts water. Obsidian chips and glass spheres crack when quenched. Vesicular pyroclasts are made of similar glass, so thermal quenching may cause them to break more easily. We performed a set of experiments on air fall pumice from Medicine Lake, California. Density and texture of similar samples are described in Manga et al., Bull Volc 2010. We made "quenched" samples by heating natural pyroclasts to 600 °C, quenching them in water at 21 °C, drying them at 105 °C, and then cooling them to room temperature. We compare these samples with untreated air fall pumice from the same deposit, hereafter referred to as "regular" pumice. We tested whether quenched pumice would 1) shatter more easily in collisions and 2) abrade faster. Our collision experiment methods are described in Dufek et al., Nature Geoscience 2012. Our abrasion experiment methods are described in Manga et al., Bull Volc 2010. We also tested whether individual clasts lose mass upon quenching and whether they increase in effective wet density. Effective wet density is defined as underwater density of a clast when water occupies part of the pore space. Effective wet density, measured as a function of time after immersion, indicates the volume fraction of the pore space that becomes occupied by water. We compare effective wet density of individual clasts pre-quenching with effective wet density after having been quenched, thoroughly dried and then cooled to room temperature. An increase in effective wet density would suggest that bubble walls had been damaged during quenching, allowing water to occupy the pore space faster. We also compare pre-quenching and post-quenching textures using X-Ray Tomography (XRT) and SEM images. Results from collision experiments show no obvious difference between quenched pumice and regular pumice. Quenched pumice abraded more quickly than regular pumice. We find that 1 to 2 % of mass was lost during quenching. Effective

  14. A glimpse into Augustine volcano's pre-glacial past: Insight from a massive rhyolite deposit (United States)

    Nadeau, P. A.; Webster, J. D.; Mandeville, C. W.; Goldoff, B. A.; Shimizu, N.; Monteleone, B. D.


    Augustine is a very high threat island volcano located on the west side of Cook Inlet, Alaska, and is the most historically active volcano in the region. As a result, Augustine has been almost wholly resurfaced by deposits from the last ~2000 years BP and little is known about older activity. Erosive pyroclastic flows associated with the 2006 eruption of Augustine created new exposures within the drainage of Augustine Creek, to the southwest of the summit. Among the newly exposed deposits is a >30 m-thick coarse pumice fall unit, which underlies ~8 m of glacial till. The lower 6 m of the deposit contain lithics 1-2 cm in diameter, while the upper 25 m of the fall are lithic-poor but contain pumice blocks up to 2 m in diameter. The majority of the unit is white pumice, with ~10% volume percent denser gray banded pumices. Yellowed, slightly weathered pumices are found at the base of the section. A similar deposit was also found on the north side of the island and may represent the same eruptive unit. Samples from the newly-discovered unit include slightly rounded and weathered pumice from the base of the unit (yellow pumice), a large fragment from near the deposit top (white pumice), and gray, banded pumice (flow-banded pumice), also from near the top of the unit. Plagioclase, orthopyroxene, amphibole, quartz, Fe-Ti oxides, and minor apatite comprise the phenocryst assemblage. Amphiboles in the white and flow-banded pumices are split into two distinct populations: a low-Al, high-Mg cummingtonite population and a high-Al population that ranges from magnesio-hornblende to ferri-tschermakite. Yellow pumices contain only cummingtonite. Analyses of melt inclusions in each of the main phenocryst phases indicate mostly rhyolitic melt compositions with water, carbon dioxide, and sulfur contents comparable to, and chlorine contents slightly lower than, more recent (Augustine melt inclusions. A single olivine and a single clinopyroxene, both from the white pumice sample, and

  15. Are Avellino (4365 cal BP) and Pompeii twin plinian eruptions? Pre-eruptive constraints and degassing history (United States)

    Boudon, Georges; Balcone-Boissard, Hélène; Villemant, Benoît.; Ucciani, Guillaume; Cioni, Raffaello


    Somma-Vesuvius activity started 35 ky ago and is characterized by numerous eruptions of variable composition and eruptive style, sometimes interrupted by long periods of unrest. The main explosive eruptions are represented by four plinian eruptions: Pomici di Base eruption (22 cal ky), Mercato (~8900 cal BP), Avellino (4365 cal BP) and Pompeii (79 AD). The 79 AD eruption embodies the most famous eruption since it's responsible of the destruction of Pompeii and Herculanum and it's the first described eruption. The Avellino eruption represents the last plinian event that preceded the Pompeii eruption. The eruptive sequence is similar to the 79 AD plinian eruption, with an opening phase preceding a main plinian fallout activity which ended by a phreatomagmatic phase. The fallout deposit displays a sharp colour contrast from white to grey pumice, corresponding to a magma composition evolution. We focus our study on the main fallout deposit that we sampled in detail in the Traianello quarry, 9 km North-North East of the crater, to investigate the degassing processes during the eruption, using volatile content and textural observations. Density and vesicularity measurements were obtained on a minimum of 100 pumice clasts sampled in 10 stratigraphic levels in the fallout deposit. On the basis of the density distribution, bulk geochemical data, point analytical measurements on glasses (melt inclusions and residual glass) and textural observations were obtained simultaneously on a minimum of 5 pumice clasts per eruptive unit. The glass composition, in particular the Na/K ratio, evolves from Na-rich phonolite for white pumices to a more K-rich phonolite for grey pumices. The pre-eruptive conditions are constrained by systematic Cl measurements in melt inclusions and matrix glass of pumice clasts. The entire magma was saturated relative to sub-critical fluids (a Cl-rich H2O vapour phase and a brine), with a Cl melt content buffered at ~6000 ppm, and a mean pre-eruptive H2O

  16. Tsunami generation by pyroclastic flow during the 3500-year B.P. caldera-forming eruption of Aniakchak Volcano, Alaska (United States)

    Waythomas, Christopher F.; Neal, Christina A.


    A discontinuous pumiceous sand, a few centimeters to tens of centimeters thick, is located up to 15 m above mean high tide within Holocene peat along the northern Bristol Bay coastline of Alaska. The bed consists of fine-to-coarse, poorly to moderately well-sorted, pumice-bearing sand near the top of a 2-m-thick peat sequence. The sand bed contains rip-up clasts of peat and tephra and is unique in the peat sequence. Major element compositions of juvenile glass from the deposit and radiocarbon dating of enclosing peat support correlation of the pumiceous sand with the caldera-forming eruption of Aniakchak Volcano. The distribution of the sand and its sedimentary characteristics are consistent with emplacement by tsunami. The pumiceous sand most likely represents redeposition by tsunami of climactic fallout tephra and beach sand during the approximately 3.5 ka Aniakchak caldera-forming eruption on the Alaska Peninsula. We propose that a tsunami was generated by the sudden entrance of a rapidly moving, voluminous pyroclastic flow from Aniakchak into Bristol Bay. A seismic trigger for the tsunami is unlikely, because tectonic structures suitable for tsunami generation are present only south of the Alaska Peninsula. The pumiceous sand in coastal peat of northern Bristol Bay is the first documented geologic evidence of a tsunami initiated by a volcanic eruption in Alaska.

  17. Late Pleistocene Holocene stratigraphy and radiocarbon dating of La Malinche volcano, Central Mexico (United States)

    Castro-Govea, Renato; Siebe, Claus


    Previous studies of La Malinche identified and radiocarbon dated several volcanic layers, the youngest of which yielded an age of ca. 7.5 ka. An additional ash fallout layer that crops out at high altitudes was considered the most recent deposit, with an estimated age of 6 ka. In the present work 38 new radiocarbon ages are presented. From these, several date the young ash fallout layer and lie around 3.1 ka. With the aid of these dates a new and comprehensive stratigraphy documenting the Late Pleistocene-Holocene eruptive history of La Malinche is presented. The stratigraphy indicates two main stages of volcanic activity: Pre-Malinche and Malinche. The first undoubtedly comprises the major part of the eruptive history, but its deposits are largely covered by the products of the latter stage, on which this study is focused. The Malinche stage was subdivided into three eruptive periods. Period 1 started with the emplacement of the Huamantla Pumice more than 45 ka ago. This deposit consists of a thick pumice fallout overlain by pyroclastic flow deposits. Subsequently, several episodes of construction and collapse of summit domes occurred. The oldest dome was dated at ca. 45 ka. Period 2 started 21.5 ka ago with the Malinche Pumice I, a widespread pumice fallout covering the entire slopes of the volcano. Pyroclastic flows and lahars related to this eruption were channeled along deep barrancas and reached considerable distances. Deposits produced by partial sector collapse and dated at ca. 20.9 ka, and a pumice-and-ash flow deposit dated at 15.9 ka were also generated during this period. The last period started with the eruption of the Malinche Pumice II, a distinctive fallout deposit overlain by ash flow deposits on the NE slope of the volcano. The age of this pumice layer is estimated between 12 and 9 ka. Formation of block-and-ash flows, lahars and pumice-and-ash flows followed during this period, and peaked in a most intensive episode that was dated at 7.5 ka

  18. Shallow conduit processes during the 1158 AD explosive eruption of Hekla volcano, Iceland (United States)

    Janebo, Maria; Houghton, Bruce; Thordarson, Thor; Larsen, Gudrun


    Hekla is one of the most frequently active silicic volcanic systems in the world, with multiple pre-historic large Plinian eruptions and 18 historical subplinian-Plinian eruptions. The common view is that the Plinian phases of the largest Hekla eruptions are all relatively homogeneous in style. Of the historical eruptions, only two were silicic: a Plinian eruption in 1104 and a smaller, less well characterized, eruption in 1158. We examine the dynamics of the 1158 eruption in detail with focus on the modulating role of shallow conduit processes. Grain size analysis, componentry, and density were used to characterize gradual and abrupt changes during the course of the eruption and quantitative vesicularity analysis was used to constrain the influence of bubble nucleation and coalescence. The 1158 eruption was a relatively steady, dry eruption with a more powerful opening phase followed by a lower intensity, waning phase accompanied by destabilization and collapse of the conduit walls. The juvenile pyroclasts are comprised of three types of microvesicular ragged pumice: white, grey, and banded. The abundance of grey pumice decreases as the eruption reaches maximum intensity, and then increases again during the waning phase of the eruption. The white pumices are more vesicular than the grey pumice, and the banded pumices have vesicularities that span predictably the range of the two end-members. The macroscopic differences between the white and grey pumice are accompanied by differences on a microscopic scale, most notably in a decrease in vesicle number density (VND) and a broadening of the vesicle size distribution, as well as increased crystal content. VND values of 0.5 to 1 E+6 mm-3 are similar to those recorded for the more powerful and sustained Plinian phases of the Novarupta 1912 and Taupo 181 eruptions in our laboratory. The 1158 pumice clasts display complex textures with adjacent domains of contrasting texture, alluding to complex nucleation, growth and

  19. Late Holocene Andesitic Eruptions at Mount Rainier (United States)

    Sisson, T. W.; Vallance, J. W.


    Holocene Mt. Rainier erupted much more frequently than is recorded by its 11 pumiceous tephras. In the 2.6-2.2 ka Summerland eruptive period, 6 groups of thin (1-5 mm) Sparsely Vesicular Glassy (SVG) ashes were deposited (S1-S6), followed by the 0.3 km3 C-tephra. Two groups of andesitic lava flows and one andesitic block-and-ash flow (2.45 ka) also erupted in the Summerland period (ice conceals any other products). Based on glass composition the pyroclastic flow correlates with S4 ashes that also contain pumiceous grains and rare pumice lapilli. The first of the lava groups, exposed in windows through the Emmons and Winthrop glaciers, is Sr-rich for Mt. Rainier eruptives and correlates with S5 & S6 ashes based on similar high-Sr plagioclase. The ensuing C-tephra formed by plinian eruption of mixed and mingled magma comprising 4 juvenile components: mixed porphyritic andesite pumice, crystal-poor andesite scoria, vesicular high-Sr dacite blebs in pumice and scoria, and poorly inflated crystal-rich high-Sr dacite. High-Sr components were probably entrained conduit linings and segregations from the preceding high-Sr eruptions. The youngest lava group, exposed at the summit, is normal-Sr andesite lacking mixing textures of the C-tephra, and represents eruption of another small batch of andesitic magma perhaps just after the C event. SVG ash grains have blocky-to-fluidal shapes, are rich in plagioclase microlites, and their glasses are high-SiO2 (66-78%) and low-Al2O3 (15-11%). Melting experiments yield apparent equilibration pressures <50MPa for SVG liquids. SVG ashes likely result from shallow hydromagmatic explosions as largely degassed magmas transited the upper-edifice hydrothermal system during effusive eruptions. Rare pumice lapilli codeposited with S1, S2, and S4 ashes have microlite-free dacitic glasses, one with nonreacted hbl phenocrysts. These pumice formed from magmas that ascended rapidly from reservoir depths, synchronous with or closely between effusive

  20. Clinical evaluation of the effect of a herbal compound made for treatment of discolorations caused by dental fluorosis

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    Mahshid Mohammdi Basir


    Full Text Available   Background and Aims: The purpose of this study was research on a new herbal compound (Seidlitzia Rosmarinus made by Traditional Medicine Research Group, University of shahed to find a safer alternative to HCL-Pumice compound technique.   Materials and Methods: In this randomized clinical trial seventy two anterior teeth from 9 patients were divided in to three groups according to fluorosis severity: mild (34 teeth, moderate (14 teeth, and sever (24 teeth. In each patient, half of the teeth were treated with “Shahed” compound and other half treated with HCL-Pumice compound. Before and after treatment, photographs were taken in both groups. HCL-Pumice treatment compound was applied for 30 seconds periods and continued for 10 minutes if necessary. In case of herbal Shahed compound the time was determined by clinical symptoms or when labial contour was dismissed, If the result was not esthetistically acceptabale for the patient, HCL-Pumice compound was applied on teeth. NaF was applied after mouth washing. The photographs of the teeth before and after treatment were reviewed by two experienced observer unaware of the treatment modality. The results were analyzed using willcoxon’s, kruskal-wallis and scheffe test.   Results: There was over 81.3% acceptance between two observers and no significant differences in intraobservers evaluation (P>0.05. Improvement in beauty indexes were observed in all degrees of dental fluorosis by 18% with HCL-Pumice compound application, but “Shahed” herbal compound induced significant reduction in the amount of white spots in mild fluorosis and stain intensity of moderate fluorosis (P<0.05 , while the reduction in the severity of discoloration in group 2, these two techniques were statistically equivalent but in the remainder, HCL-Pumice compound was more significantly effective (P<0.05 .   Conclusion: HCL-Pumice compound reduces the severity of the discoloration of the teeth. Shahed herbal compound

  1. Volcaniclastic facies architecture of a long-lived, nested silicic tuff ring: the Los Loros volcano, Mendoza, Argentina (United States)

    Németh, Károly; Risso, Corina; Nullo, Francisco


    Los Loros is a small, well-preserved volcanic depression. New K/Ar age dating revealed that the volcano is least 1 million years old. The circular morphology of the ~50 m deep and ~ 1 km broad crater of Los Loros was initially inferred to be of phreatomagmatic origin. Recent work, however, concluded that Los Loros is a far more complex volcano than originally thought; with multiple eruptive phases produced by magmatic and minor phreatomagmatic explosive fragmentation-dominated eruptive processes that consequently formed a low aspect ratio volcano. Previous work also suggested that volcanic rocks of Los Loros were entirely basaltic in composition (Puente Formation) and their age was mid-upper Pleistocene. Newly obtained geochemical data, alongside a new age determination, underlies the fact that the volcano is far older than had been expected from its morphology, and its composition shows no signs of basalt, instead it is trachytic. The volcanic succession forms a ~100 m thick pile sitting directly on Cretaceous continental red beds. The base of the volcanic succession is a polymict volcaniclastic conglomerate with variable bed thickness and occasional cross stratification, indicating a channel-filling nature and an origin from a braided river system. The diversity of the clasts suggests that they likely have been transported from a nearby Miocene back-arc volcanic complex, the Sierra Cachahuén (~40 km), which is a lava dome dominated multiple volcano with thick silicic pyroclastic successions. The volcaniclastic conglomerate is covered by a trachytic pumiceous unit thickening toward the SSE. They are composed of loosely packed rounded pumice lapilli. These beds have a well-sorted texture with no characteristic internal stratification, indicating that they are fall in origin and the bed thickness variation is inferred to reflect the paleo-wind direction. A thick pile of pumiceous tuff (up to 20 m) overlies the basal pumice fall unit. It is stratified, cross

  2. 76 FR 50971 - Endangered and Threatened Wildlife and Plants; 90-Day Finding on a Petition To List the Leona's... (United States)


    ... submission-- including any personal identifying information--will be posted on the Web site. If your... very deep alluvium derived from pumice and other volcanic rock.'' The Leona's little blue butterfly... mining, and the potential development of a biomass energy facility may have deleterious impacts on...

  3. Soil moisture depletion in three lodgepole pine stands in northeastern Oregon. (United States)

    Daniel M. Bishop


    A 1-year study in the Blue Mountains of northeastern Oregon indicates that substantial amounts of soil moisture are consumed during the growing season in lodgepole pine stands. Dual purposes of the study were to estimate the quantities of water that can be stored in basalt-pumice soils typical of the Blue Mountains, and to determine the rate and amount of moisture...

  4. Robust date for the Bronze Age Avellino eruption (Somma-Vesuvius) : 3945 +/- 10 calBP (1995 +/- 10 calBC)

    NARCIS (Netherlands)

    Sevink, Jan; van Bergen, Manfred J.; van der Plicht, Johannes; Feiken, Hendrik; Anastasia, Carmela; Huizinga, Annika; Maroto, Julià; Vaquero, Manuel; Arrizabalaga, Álvaro; Baena, Javier; Baquedano, Enrique; Jordá, Jesús; Julià, Ramon; Montes, Ramón; Rasines, Pedro; Wood, Rachel; Walsma, A.


    We found Bronze Age lake sediments from the Agro Pontino graben (Central Italy) to contain a thin (2-3 cm) continuous tephra layer composed of lithics, crystals and minor volcanic glass. Tephrochronological and compositional constraints strongly suggest that this layer represents the Avellino pumice

  5. 26 CFR 1.613-2 - Percentage depletion rates. (United States)


    ... percent—Ball clay, bentonite, china clay, metal mines, 1 sagger clay, rock asphalt, vermiculite. 1 Not... clay, gravel, mollusk shells (including clam shells and oyster shells), peat, pumice, sand, scoria.... Clay, refractory and fire. 6 Diatomaceous earth. Dolomite. Fedlspar. Flake Graphite. 5 Applicable only...

  6. 25 years of ecological change at Mount St. Helens. (United States)

    V.H. Dale; C.M. Crisafulli; F.J. Swanson


    18 May 2005 marks the 25th anniversary of the massive eruption of Mount St. Helens. This eruption involved diverse geological processes (1) that disturbed forests, meadows, lakes, an drivers (2) (see the figure). A huge landslide and searing flows of hot gases and pumic framents (pyroclastic flows) inundated 60 km2 of land, obliterating...

  7. The Northern Territories: Case Study in Japanese-Soviet Relations. (United States)


    be used in cellulose production. Pumice and perlite are ex- tracted for use in construction materials and road-building. Titanium-magnetic sands are...types (watermelons and tomatoes ) due to the relatively warm climatic conditions. Pigs, sheep, and horses populate most all settlements, and dairy

  8. Coupling eruption and tsunami records: the Krakatau 1883 case study, Indonesia (United States)

    Paris, Raphaël; Wassmer, Patrick; Lavigne, Franck; Belousov, Alexander; Belousova, Marina; Iskandarsyah, Yan; Benbakkar, Mhammed; Ontowirjo, Budianto; Mazzoni, Nelly


    The well-documented 1883 eruption of Krakatau volcano (Indonesia) offers an opportunity to couple the eruption's history with the tsunami record. The aim of this paper is not to re-analyse the scenario for the 1883 eruption but to demonstrate that the study of tsunami deposits provides information for reconstructing past eruptions. Indeed, though the characteristics of volcanogenic tsunami deposits are similar to those of other tsunami deposits, they may include juvenile material (e.g. fresh pumice) or be interbedded with distal pyroclastic deposits (ash fall, surges), due to their simultaneity with the eruption. Five kinds of sedimentary and volcanic facies related to the 1883 events were identified along the coasts of Java and Sumatra: (1) bioclastic tsunami sands and (2) pumiceous tsunami sands, deposited respectively before and during the Plinian phase (26-27 August); (3) rounded pumice lapilli reworked by tsunami; (4) pumiceous ash fall deposits and (5) pyroclastic surge deposits (only in Sumatra). The stratigraphic record on the coasts of Java and Sumatra, which agrees particularly well with observations of the 1883 events, is tentatively linked to the proximal stratigraphy of the eruption.

  9. A simple method of monitoring carbon dioxide output in anaesthetized patients. (United States)

    Christensen, K N


    The mean CO2 output during anaesthesia in paralyzed patients can be monitored by continuous capnographic analysis of the total exhaled gases, the latter being mechanically integrated by pumice canisters. The gas is evacuated from the Hafnia A circuit via an ejector flowmeter. The results are not influenced by the flow rates employed.

  10. A Survey of Ant Species in Three Habitats at Mount St. Helens National Volcanic Monument

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    Jessamy J. Rango


    Full Text Available Ants were surveyed in three habitats at Mount St. Helens in 2008. The area most impacted by the 1980 eruption is the Pumice Plain. Less impacted is the Blowdown Zone where trees were toppled due to the blast. Two habitats were surveyed in the Pumice Plain varying in vegetation density (Pumice Plain Low-Vegetation (PPLV and Pumice Plain High-Vegetation (PPHV, and one habitat was surveyed in the Blowdown Zone (BDZ. Ten ant species were collected with the most species collected from the BDZ habitat and the least from the PPLV habitat. Ant abundance was higher at the BDZ and PPHV habitats than at the PPLV habitat. Ant biodiversity was highest at the BDZ habitat than at the PPHV and PPLV habitats. Significant correlations between ant community parameters and plant community parameters were also found. Few plants in the PPLV habitat may contribute to the lack of ants. High ant species richness at the BDZ habitat may be due to complex plant architecture. Results from this study suggest that ants are important focal species in tracking biotic recovery following disturbances.

  11. 36 CFR 228.41 - Scope. (United States)


    ... wood and common varieties of sand, gravel, stone, pumice, pumicite, cinders, clay, and other similar... or for: Paint fillers or extenders; flagstone, ashlar, rubble, mortar, brick, tile, pipe, pottery... materials. This category includes, but is not limited to, minerals such as sand, gravel, clay, crushed...

  12. Transport properties of pyroclastic rocks from Montagne Pelée volcano (Martinique, Lesser Antilles) (United States)

    Bernard, Marie-Lise; Zamora, Maria; GéRaud, Yves; Boudon, Georges


    The hydraulic and electrical properties of pyroclastic rocks have been investigated in laboratory on a representative sampling of Montagne Pelée (Martinique, France) deposits with renewed interest in geophysical applications. This sampling covers all the lithologic units of this volcano: lava dome and lava flows, pumices from ash-and-pumice fall and flow deposits, lava blocks from block-and-ash flow and Peléean "nuées ardentes" deposits, scoriae from scoria flow deposits. The connected porosity varies over a wide range from 3 to 62%. The unconnected porosity is important only on pumices where it can reach 15%. The permeability covers more than 5 orders of magnitude, ranging from 10-16 to 35 × 10-12 m2. The higher values are obtained on lava blocks and the scoriae, even if these rocks are less porous than the pumices. The formation factor ranges from 7 to 1139. The transport properties of these rocks are slightly correlated with porosity. This indicates that these properties are not only controlled by the connected porosity. To connect the transport properties to the textural characteristics of the pore network of pyroclastic rocks, different models, based on geometrical considerations or percolation theory, were tested. The pore access radius distribution and the tortuosity control the transport properties of pyroclastic rocks. Consequently, the models (electric and hydraulic) based on the concept of percolation (e.g., the models of Katz and Thompson), apply better than the equivalent channel model of Kozeny-Carman. In addition, the difference in transport properties observed on lava blocks and pumices confirms that the mechanisms of degassing and vesiculation are different for these two types of rock.

  13. Volcanostratigraphic Sequences of Kebo-Butak Formation at Bayat Geological Field Complex, Central Java Province and Yogyakarta Special Province, Indonesia

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    Sri Mulyaningsih


    Full Text Available Bayat Complex is usually used as a work field for students of geology and other geosciences. The study area is located in the southern part of the Bayat Complex. Administratively, it belongs to Central Java Province and Yogyakarta Special Province. The lithology of Bayat is very complex, composed of various kinds of igneous, sedimentary, metamorphic, and volcanic rocks. Most of previous researchers interpreted Bayat as a melange complex constructed within a subduction zone. Kebo-Butak is one of formations that forms the Bayat field complex. The formation is composed of basalt, layers of pumice, tuff, shale, and carbonaceous tuff. Most of them are known as volcanic rocks. These imply that volcanic activities are more probable to construct the geology of Bayat rather than the subducted melange complex. The geological mapping, supported by geomorphology, petrology, stratigraphy, and geological structures, had been conducted in a comprehensive manner using the deduction-induction method. The research encounters basalt, black pumice, tuff with basaltic glasses fragments, zeolite, argilic clay, as well as feldspathic- and pumice tuff. Petrographically, the basalt is composed of labradorite, olivine, clinopyroxene, and volcanic glass. Black pumice and tuff contain prismatic clinopyroxene, granular olivine, and volcanic glasses. Feldspathic tuff and pumice tuff are crystal vitric tuff due to more abundant feldspar, quartz, and amphibole than volcanic glass. Zeolite comprises chlorite and altered glasses as deep sea altered volcanic rocks. The geologic structure is very complex, the major structures are normal faults with pyrite in it. There were two deep submarine paleovolcanoes namely Tegalrejo and Baturagung. The first paleovolcano erupted effusively producing basaltic sequence, while the second one erupted explosively ejecting feldspathic-rich pyroclastic material. The two paleovolcanoes erupted simultaneously and repeatedly.

  14. Progressive assembly of a massive layer of ignimbrite with a normal-to-reverse compositional zoning: the Zaragoza ignimbrite of central Mexico (United States)

    Carrasco-Núñez, Gerardo; Branney, Michael J.


    The Zaragoza ignimbrite and two enclosing rhyodacite pumice fall layers were emplaced during the 15 km3 (DRE), ˜0.1 Ma Zaragoza eruption from Los Humeros volcanic centre, 180 km east of Mexico City. The ignimbrite comprises several massive flow-units, the largest of which locally exceeds 20 m in thickness and is regionally traceable. It comprises massive lapilli-ash with vertical elutriation pipes, and has a fine-grained inverse-graded base and a pumice concentration zone at the top. It also exhibits an unusual gradational ‘double’ vertical compositional zonation that is widely traceable. A basal rhyodacitic (67.6-69 wt% SiO2) zone grades up via a mixed zone into a central andesitic (58-62 wt% SiO2) zone, which, in turn, grades up into an upper rhyodacitic (67.6-69 wt% SiO2) zone. Zoning is also defined by vertical variations in lithic clast populations. We infer that pyroclastic fountaining fed initially rhyodacite pumice clasts to a sustained granular fluid-based pyroclastic density current. The composition of the pumice clasts supplied to the current then gradually changed, first to andesite and then back to rhyodacite. Inverse grading at the base of the massive layer may reflect initial waxing flow competence. The pumice concentration at the top of the massive layer is entirely rhyodacitic and was probably deposited during waning stages of the current, when the supply of andesitic pumice clasts had ceased. The return to rhyodacitic composition may have been the result of eruption-conduit modification during collapse of Los Potreros caldera, marked in the ignimbrite by a widespread influx of hydrothermally altered lithic blocks, and/or a decrease in draw-up depth from a compositionally stratified magma chamber as the eruptive mass flux waned. The massive layer of ignimbrite thins locally to less than 2 m, yet it still shows the double zonation. Correlation of the zoning suggests that the thin massive layer is stratigraphically condensed, and aggraded

  15. Holocene tephra succession of Puyehue-Cordón Caulle and Antillanca/Casablanca volcanic complexes, southern Andes (40-41°S) (United States)

    Naranjo, J. A.; Singer, B. S.; Jicha, B. R.; Moreno, H.; Lara, L. E.


    Puyehue-Cordón Caulle and Antillanca volcanic complexes are two of at least 50 active frontal arc volcanoes that define the 1400 km-long Southern Volcanic Zone of Chile. Holocene tephra deposits in Chile and Argentina (40-41°S) up to 100 km east of these volcanoes comprise at least five voluminous ( 1 to 8 km3) pyroclastic-fall layers that preceded several recently deposited Cordón Caulle pumice fallouts. Field observations of proximal, medium, and distal facies of the deposits, in conjunction with geochronology and geochemistry of the volcanic complexes, indicate that three fall layers are derived from Puyehue volcano (Puyehue 1 and 2, and Mil Hojas), whereas two are sourced from the Antillanca complex (Playas Blanca-Negra, and Nahuel Huapi Tephra), 20 km to the south. The oldest tephra (calibrated 14C age 10.49 ± 0.12 ka, 2σ), found only at medium-distal facies, is deposited directly on granitic moraine boulders and consists of deeply weathered, orange dacitic pumice lapilli. The next prominent tephra at 7 ka comprises dacitic pumice and its age is equivalent to a rhyodacitic dome exposed in the Puyehue summit crater. Above these deposits there are phases of a complex eruption consisting of a conspicuous compositionally-zoned tephra. It also comprises a pyroclastic density current, together with lithic rich and scoriaceous fallout deposits. Mineralogical, geochemical, and Sr isotope evidence, plus the isopach maps, confirm that this sequence of eruptive events is sourced from Antillanca at 1932 ± 68 yrBP. The total volume of this eruptive sequence exceeds 8 km3, making it the largest Holocene eruption from either volcanic complex. This eruption was likely responsible for the destruction of an ancestral Antillanca volcano and the formation of a 4.5 km diameter caldera. A distinctive younger unit in the region is a voluminous rhyodacitic pumice fall (calibrated 14C age 1.11 ± 0.07 ka), above which a series of several alternating dark lithic and pumice

  16. The Sarikavak Tephra, Galatea, north central Turkey: a case study of a Miocene complex plinian eruption deposit (United States)

    Schumacher, Rolf; Mues-Schumacher, Ulrike; Toprak, Vedat


    The Sarikavak Tephra from the central Galatean Volcanic Province (Turkey) represents the deposit of a complex multiple phase plinian eruption of Miocene age. The eruptive sequence is subdivided into the Lower-, Middle-, and Upper Sarikavak Tephra (LSKT, MSKT, USKT) which differ in type of deposits, lithology and eruptive mechanisms. The Lower Sarikavak Tephra is characterised by pumice fall deposits with minor interbedded fine-grained ash beds in the lower LSKT-A. Deposits are well stratified and enriched in lithic fragments up to >50 wt% in some layers. The upper LSKT-B is mainly reversely graded pumice fall with minor amounts of lithics. It represents the main plinian phase of the eruption. The LSKT-A and B units are separated from each other by a fine-grained ash fall deposit. The Middle Sarikavak Tephra is predominantly composed of cross-bedded ash-and-pumice surge deposits with minor pumice fall deposits in the lower MSKT-A and major pyroclastic flow deposits in the upper MSKT-B unit. The Upper Sarikavak Tephra shows subaerial laminated surge deposits in USKT-A and subaqueous tephra beds in USKT-B. Isopach maps of the LSKT pumice fall deposits as well as the fine ash at the LSKT-A/B boundary indicate NNE-SSW extending depositional fans with the source area in the western part of the Ovaçik caldera. The MSKT pyroclastic flow and surge deposits form a SW-extending main lobe related to paleotopography where the deposits are thickest. Internal bedding and lithic distribution of the LSKT-A result from intermittent activity due to significant vent wall instabilities. Reductions in eruption power from (partial) plugging of the vent produced fine ash deposits in near-vent locations and subsequent explosive expulsion of wall rock debris was responsible for the high lithic contents of the lapilli fall deposits. A period of vent closure promoted fine ash fall deposition at the end of LSKT-A. The subsequent main plinian phase of the LSKT-B evolved from stable vent

  17. Clast comminution during pyroclastic density current transport: Mt St Helens (United States)

    Dawson, B.; Brand, B. D.; Dufek, J.


    Volcanic clasts within pyroclastic density currents (PDCs) tend to be more rounded than those in fall deposits. This rounding reflects degrees of comminution during transport, which produces an increase in fine-grained ash with distance from source (Manga, M., Patel, A., Dufek., J. 2011. Bull Volcanol 73: 321-333). The amount of ash produced due to comminution can potentially affect runout distance, deposit sorting, the volume of ash lofted into the upper atmosphere, and increase internal pore pressure (e.g., Wohletz, K., Sheridan, M. F., Brown, W.K. 1989. J Geophy Res, 94, 15703-15721). For example, increased pore pressure has been shown to produce longer runout distances than non-comminuted PDC flows (e.g., Dufek, J., and M. Manga, 2008. J. Geophy Res, 113). We build on the work of Manga et al., (2011) by completing a pumice abrasion study for two well-exposed flow units from the May 18th, 1980 eruption of Mt St Helens (MSH). To quantify differences in comminution from source, sampling and the image analysis technique developed in Manga et al., 2010 was completed at distances proximal, medial, and distal from source. Within the units observed, data was taken from the base, middle, and pumice lobes within the outcrops. Our study is unique in that in addition to quantifying the degree of pumice rounding with distance from source, we also determine the possible range of ash sizes produced during comminution by analyzing bubble wall thickness of the pumice through petrographic and SEM analysis. The proportion of this ash size is then measured relative to the grain size of larger ash with distance from source. This allows us to correlate ash production with degree of rounding with distance from source, and determine the fraction of the fine ash produced due to comminution versus vent-fragmentation mechanisms. In addition we test the error in 2D analysis by completing a 3D image analysis of selected pumice samples using a Camsizer. We find that the roundness of PDC

  18. Waduk Parangjoho dan Songputri: Alternatif Sumber Erupsi Formasi Semilir di daerah Eromoko, Kabupaten Wonogiri, Jawa Tengah

    Directory of Open Access Journals (Sweden)

    Sutikno Bronto


    Full Text Available Semilir Formation was typically originated from products of a very explosive volcanic activity, i.e. breccias, lapillistones, and tuffs containing abundant pumice. It has a light grey to white colour and high silica andesite to dacite in composition, mainly rich in volcanic glass and quartz. Sedimentary structures of these volcanic rocks are massive, grading, planar bedding, and cross-bedding to antidunes, with grain size varies from ash (≤ 2 mm to lapilli (2 – 64 mm to bomb and block (> 64 mm. The formation is widely distributed from the west side (Pleret and Piyungan areas, Bantul Regency, Special Province of Yogyakarta until Eromoko area in the east (Wonogiri Regency, Jawa Tengah Province. Stratigraphically, the Semilir Formation underlies the Nglanggeran Formation, and overlies the Mandalika Formation in the eastern part and Kebo-Butak Formation in the western part. Geomorphological- and lithological analyses of the Semilir Formation in areas of Parangjoho and Song- putri Dams, Eromoko Sub-regency, Wonogiri Regency indicate that the two depressions were alternatively volcanic sources of the Semilir Formation in the Eromoko area. This is proved by the presence of co-ignimbrite breccias(co-ignimbrite lag fall deposits, that descriptively they are polymict breccias. This rock is characterized by a mixing of pumice and various hard rock fragments that primarily are juvenile materials (volcanic blocks, bombs, accessory-, and accidental rock fragments set in pumice-rich volcanic ash and lapilli sizes. The accessory materials came from older volcanic rocks, whereas the accidental ones were originated from basement rocks. During a caldera forming event or a destruction period of an older composite volcanic cone(s, all older rocks resting above the magma chamber were ejected to the surface by a very high magmatic pressure. Since they were heavier than the juvenile material, most accessory and

  19. Preexplosive conduit conditions during the 2010 eruption of Merapi volcano (Java, Indonesia) (United States)

    Drignon, Mélissa J.; Bechon, Tonin; Arbaret, Laurent; Burgisser, Alain; Komorowski, Jean-Christophe; Martel, Caroline; Miller, Hayden; Yaputra, Radit


    The 2010 eruption is the largest explosive event at Merapi volcano since 1872. The high energy of the initial 26 October explosions cannot be explained by simple gravitational collapse, and the paroxysmal explosions were preceded by the growth of a lava dome not large enough to ensure significant pressurization of the system. We sampled pumice from these explosive phases and determined the preexplosive depths of the pumices by combining textural analyses with glass water content measurements. Our results indicate that the magma expelled was tapped from depths of several kilometers. Such depths are much greater than those involved in the pre-2010 effusive activity. We propose that the water-rich magma liberated enough gas to sustain the explosivity. Our results imply that the explosive potential of volcanoes having dome-forming, effusive activity is linked to the depth from which fresh magma can be evacuated in a single explosion, regardless of the evacuated volume.

  20. Subaqueous explosive eruption and welding of pyroclastic deposits. (United States)

    Kokelaar, P; Busby, C


    Silicic tuffs infilling an ancient submarine caldera, at Mineral King in California, show microscopic fabrics indicative of welding of glass shards and pumice at temperatures >500 degrees C. The occurrence indicates that subaqueous explosive eruption and emplacement of pyroclastic materials can occur without substantial admixture of the ambient water, which would cause chilling. Intracaldera progressive aggradation of pumice and ash from a thick, fast-moving pyroclastic flow occurred during a short-lived explosive eruption of approximately 26 cubic kilometers of magma in water >/=150 meters deep. The thickness, high velocity, and abundant fine material of the erupted gas-solids mixture prevented substantial incorporation of ambient water into the flow. Stripping of pyroclasts from upper surfaces of subaqueous pyroclastic flows in general, both above the vent and along any flow path, may be the main process giving rise to buoyant-convective subaqueous eruption columns and attendant fallout deposits.

  1. Late Holocene history of Chaitén Volcano: new evidence for a 17th century eruption (United States)

    Lara, Luis E.; Moreno, Rodrigo; Amigo, Álvaro; Hoblitt, Richard P.; Pierson, Thomas C.


    Prior to May 2008, it was thought that the last eruption of Chaitén Volcano occurred more than 5,000 years ago, a rather long quiescent period for a volcano in such an active arc segment. However, increasingly more Holocene eruptions are being identified. This article presents both geological and historical evidence for late Holocene eruptive activity in the 17th century (AD 1625-1658), which included an explosive rhyolitic eruption that produced pumice ash fallout east of the volcano and caused channel aggradation in the Chaitén River. The extents of tephra fall and channel aggradation were similar to those of May 2008. Fine ash, pumice and obsidian fragments in the pre-2008 deposits are unequivocally derived from Chaitén Volcano. This finding has important implications for hazards assessment in the area and suggests the eruptive frequency and magnitude should be more thoroughly studied.

  2. Cultural Resources Survey of Smithville Lake, Missouri. Volume 1: Archeology (United States)


    seeds from plants of the goosefoot family. Clinkers — a pumice-like stone which erodes from the South Dakota area and is carried (it floats) down the...Excavation of the Moore Site, Yampa, Colorado. 1973 Non-metric analysis work in South and East Africa and Israel. 1974 Director of Kansas State...PROGRAM ELEMENT NO. PROJECT NO. TASK NO. WORK UNIT ACCESSION NO. 11. TITLE (Include Security Classification) VOLUME 1: ARCHEOLOGY



    Chung, Heajoo; Song, Youngsun


    The Yucatan peninsula is a limestone based karst region. However, most of the pottery fragments from the Mayan Postclassic period of Chichen Itza, Yucatan, Mexico, contain volcanic materials as temper. Petrographic thin section analysis of pottery from Chichen Itza and related Yucatan archaeological sites shows that volcanic materials in the paste composition have two distinguishing characteristics. The glass shards and pumice frag-ments found in the pottery are fresh in form, mineralogically...

  4. Effects of different substrates and salinity on growth and yield of broccoli (Brassica oleracea var. italica in soilless culture

    Directory of Open Access Journals (Sweden)


    Full Text Available Salinity is a very serious problem for agricultural development, especially in arid and semi-arid regions. On the other hand, many benefits of soilless culture have caused the expansion of these systems in these areas. In this research, in order to investigate the effects of different substrates and salinity stress on physiological characteristics and yield of broccoli, an experiment was conducted as factorial, in which the main factor was substrate (cocopeat, perlite, sand, 25% cocopeat+75% perlite, 25% perlite+75% cocopeat and 50% peat+50% pumice and the sub factor was salinity stress (0, 100 and 150 mM NaCl with 4 replications. Results indicated that substrate, different levels of salinity and their interaction had significant effects on morphological characteristics, days to flowering, fresh and dry weight of leaves, nutrients concentration and weight of the broccoli head. Maximum values of the aforementioned factors were observed in the zero salinity level and 50% peat+50% pumice substrate. This means that substrate can be effective on the effect of salinity on plants. High levels of salinity caused a reduction in growth and yield of broccoli and this growth reduction was accompanied by the reduction of chlorophyll and content of Ca, K, and Fe and increased Na and Cl concentration in leaf tissue. The best growing medium, either in saline or non-saline conditions, was 50% peat+50% pumice. Although broccoli growth was not suitable in perlite medium, this substrate caused its early maturing. In this experiment, salinity treatment reduced the head weight of broccoli, in addition to decreasing the quality of yield. According to the results, 50% peat+50 pumice is recommended as a proper substrate for production of broccoli.

  5. Orthodontic bracket bonding to glazed full-contour zirconia


    Kwak, Ji-Young; Jung, Hyo-Kyung; Choi, Il-Kyung; Kwon, Tae-Yub


    Objectives This study evaluated the effects of different surface conditioning methods on the bond strength of orthodontic brackets to glazed full-zirconia surfaces. Materials and Methods Glazed zirconia (except for the control, Zirkonzahn Prettau) disc surfaces were pre-treated: PO (control), polishing; BR, bur roughening; PP, cleaning with a prophy cup and pumice; HF, hydrofluoric acid etching; AA, air abrasion with aluminum oxide; CJ, CoJet-Sand. The surfaces were examined using profilometr...

  6. Evidences for disruption of a crystallizing front in a magma chamber during caldera collapse: an example from the Breccia Museo unit (Campanian Ignimbrite eruption, Italy) (United States)

    Fulignati, P.; Marianelli, P.; Proto, M.; Sbrana, A.


    This work is focused on juvenile components and some cognate xenoliths of the Breccia Museo (BM) unit. The BM is a coarse-grained proximal unit of the caldera-forming phase of the Ignimbrite Campana (IC) eruption, southern Italy. The BM products show some peculiar characteristics that distinguish them from the other IC deposits. In particular, different types of pumice fragments constitute the juvenile fraction and their crystal contents are remarkably higher than the other IC units. Slightly porphyritic and highly porphyritic trachytic to phonolitic pumices were distinguished in each sample and investigated separately for mineralogy, matrix glass composition, melt and fluid inclusion studies. Most feldspar crystals may have formed at the margins of the magma chamber and the crystal content of both types of pumice fragments can be ascribed to variable entrainment of these crystals (from the solidification front) by the melt. Variably porphyritic (<5 to 30 vol% phenocrysts) pumice and completely crystallized nodules may represent samples of progressively crystallized magma at the chamber walls. Crystallization temperatures of magmas and xenoliths were estimated using two independent methods: a two-feldspar geothermometer and the homogenization temperatures of melt and fluid inclusions in clinopyroxene and K-feldspar. The decrease in the estimated crystallization temperatures from the melt (980-850°C) to the nodules (840-820°C) is consistent with a model of decreasing temperature at a magma chamber solidification front. The study of xenoliths revealed that exsolution of a hypersaline aqueous fluid phase occurred at the peripheral parts of the magma chamber.

  7. The eruption of the Breccia Museo (Campi Flegrei, Italy): Fractional crystallization processes in a shallow, zoned magma chamber and implications for the eruptive dynamics (United States)

    Melluso, Leone; Morra, Vincenzo; Perrotta, Annamaria; Scarpati, Claudio; Adabbo, Mariarosaria


    The Breccia Museo Member (BMM) was formed by an explosive eruption that occurred in the SW sector of Campi Flegrei about 20 ka ago. The eruptive sequence consists of the Lower Pumice Flow Unit and the overlying Upper Pumice Flow Unit with its associated lithic Breccia Unit. Interlayered with the Breccia Unit is a welded deposit that mainly consists of spatter clasts (Spatter Unit). The products of this eruption range in composition from trachytic to trachyphonolitic with K 2O decreasing from 9.5 to 7 wt.%; Na 2O correspondingly increases from 2.6 to 7.2 wt.% with increasing differentiation (Nb from 23 to 122 ppm). The phenocrysts are mostly sanidine (Or 88-63) with subordinate plagioclase (An 33-27), clinopyroxene (Ca 47Mg 44Fe 9 to Ca 46Mg 35Fe 19), biotite, titanomagnetite, and apatite. The observed major- and trace-element variations are fully consistent with about 80% fractional crystallization of a sanidine-dominated assemblage starting from the least differentiated trachytes. The compositions of the erupted products are compatible with the progressive tapping of a shallow magma chamber that was thermally and chemically zoned. The incompatible trace elements indicate a slightly different magma composition with respect to trachytes of the Campi Flegrei mainland. The geochemical stratigraphy suggests that after an early eruptive phase during which the upper, most differentiated level of the magma chamber was tapped, the sudden collapse of the roof of the reservoir triggered drainage of the remaining magma, which ranged in composition from trachyte to trachyphonolite, and formed the Breccia Unit and the Upper Pumice Flow Unit. The strongly differentiated trachyphonolite composition of the spatter clasts also suggests that they likely originated from the uppermost part of the reservoir soon after the eruption of Lower Pumice Flow Unit and the collapse of the chamber roof. This is in agreement with the eruptive model proposed by Perrotta and Scarpati (1994).

  8. Removal of selenium species from waters using various surface-modified natural particles and waste materials

    Energy Technology Data Exchange (ETDEWEB)

    Yigit, Nevzat O.; Tozum, Seda [Department of Environmental Engineering, Suleyman Demirel University, Isparta (Turkey)


    Waste red mud and natural pumice/volcanic slag particles were surface modified and their selenium adsorption from waters was investigated. Acid activation/heat treatment of original red mud (ORM) particles significantly increased their micropore and external surface area and cumulative volume of pores. Iron oxide coating of pumice/slags and acid activation of ORM decreased their pH{sub pzc} values and increased surface acidity. Selenite/selenate adsorption on iron oxide surfaces and acid activated red mud (AARM) was very fast with approximately first-order adsorption kinetics. Iron oxide coating of pumice/slag and acid activation of ORM particles significantly enhanced their selenite and selenate uptakes. Maximum Se adsorption capacities as high as 6.3 (mg Se/g adsorbent) were obtained by AARM. The extent of selenate uptakes by the surface modified particles was generally lower than those of selenite. Due to competition among Se species and other background water matrix for iron oxide adsorption sites, reduced selenite/selenate uptakes were found in natural water compared to single solute tests. Higher Se uptakes by iron oxide surfaces were found at pH 7.5 compared to pH 8.9, due to increased electrostatic repulsion among iron oxides and Se species at higher pH. The most effective adsorbents among the tested 17 different particles for Se uptake were AARM and iron oxide coated pumice. Se concentrations less than drinking water standards (5-10 {mu}g/L) can be achieved by these particles. These low-cost, natural, or recyclable waste particles appear to be promising adsorbents for Se removal after their surface modification. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Controlling Corrosion in Defence Equipment - Technical Meeting, (United States)


    corrosion of Ni/Al bronze in neutral solution, (2) the inhibited corrosion of mild steel in sulphuric acid, (3) comparison and ranking of a number of... electropolish : alkaline clean: pumice scrub: anodic etch: chromium plate. It must be remembered that mild steel is not being used, but a low alloy steel ...Wolsley shows no such damage. After all they are both made - from similar steels and both have been exposed to the two essential ingredients required

  10. Coarse fraction components in a red-clay sedimemt core, Central Indian Ocean Basin: Their occurrence and significance

    Digital Repository Service at National Institute of Oceanography (India)

    Iyer, S.D.; Fernandes, G.Q.; Mahender, K.

    , phillipsite, clinoptilolite and nontronite also occur (Kastner and Stonecipher, 1978; Iyer et al., 1997; Mascarenhas-Pereira and Nath, 2010). Diagenetically, well-formed phillipsite crystals form within manganese micronodules of the CIOB (Banerjee and Iyer... twinned crystals that show 2 or more intersecting twin planes. The crystals are either fresh and while a few show features of dissolution in the form of pores or pits. The pumices have ellipsoidal, elongated and spherical vesicles and also form nuclei...

  11. New proximal tephras at Somma-Vesuvius: evidences of a pre-caldera, large (?) explosive eruption (United States)

    Sparice, Domenico; Scarpati, Claudio; Mazzeo, Fabio Carmine; Petrosino, Paola; Arienzo, Ilenia; Gisbert, Guillem; Petrelli, Maurizio


    A 5 m thick pyroclastic and volcaniclastic sequence, never reported before, comprising a pumice fall deposit has been recognized in a disused quarry near Pollena Trocchia, on the NW slope of Somma-Vesuvius. It is composed of three stratigraphic units: a pumice fall deposit that underlies a pyroclastic density current deposit; they are overlain by a volcaniclastic unit emplaced during a quiescent period of the volcano. The pyroclastic deposits are separated by a horizon of reworked material indicating the emplacement from two distinct eruptive events. The pumice fall deposit has been subject of a detailed investigation. It consists of an ash bed overlaid by a roughly stratified pumice fall layer. The presence of ballistic clasts indicates the proximal nature of this deposit and its stratigraphic position below the Pomici di Base (22 ka) Plinian deposit allows constraining its age to the pre-caldera period (22-39 ky) of activity of Somma-Vesuvius. Samples have been collected in order to perform sedimentological (grain size and componentry), geochemical and isotopic analyses. Samples range from moderately to poorly sorted and show a trachytic composition. The comparison with literature data of compatible deposits vented from Somma-Vesuvius (Schiava, Taurano and Codola eruptions as well as borehole data) allows excluding any correlation with already known Vesuvian products suggesting that the analysed products are ascribable to a new, pre-caldera, explosive eruption. We name this new event ;Carcavone eruption;. Based on thickness, maximum lithic clasts and orientation of impact sags, showing a provenance from SE, we envisage the emplacement from a Plinian style eruption vented in the northern sector of the current caldera.

  12. Dental enamel roughness with different acid etching times: Atomic force microscopy study



    Objective: An important characteristic of human dental enamel not yet studied in detail is its surface roughness in mesoscopic scale. This study evaluated quantitatively and qualitatively the surface topography of acid etched enamel with different etching times. Materials and Methods: Ninety-six human maxillary bicuspids were randomly distributed into three groups (n=32): T0 (control), pumiced; T15, 35% phosphoric acid etched enamel for 15 s; T30, 35% phosphoric acid etched enamel for 30 s. R...

  13. In situ formation of welded tuff-like textures in the carapace of a voluminous silicic lava flow, Owyhee County, SW Idaho (United States)

    Manley, C. R.


    The Badlands rhyolite, on the Owyhee Plateau of southwestern Idaho, can be demonstrated to be a large lava flow on the basis of its geometry of large and small flow lobes, its well-exposed near-vent features, and its response to pre-existing topography. However, samples of the dense upper vitrophyre of the unit reveal a range of annealed fragmental textures, including material which closely resembles the compressed, welded glass shards which are characteristic of ignimbrites. Formation of these tuff-like textures involved processes probably common to emplacement of most silicic lava flow units. Decompression upon extrusion causes inflation of pumice at the surface of the lava flow; some of this pumice is subsequently comminuted, producing loose bubble-wall shards, bits of pumice, chips of dense glass, and fragments of phenocrysts. This debris sifts down around loose blocks and into open fractures deeper in the flow, where it can be reheated, compressed, and annealed to varying degrees. The end result is a dense vitrophyre layer (beneath the true upper, non-welded carapace breccia) which can be extremely texturally heterogeneous, with areas of flow-foliated lava occurring very near lava which in many aspects looks like welded ignimbrite, complete with flattened pumices. Identical textures in other silicic units have been cited by previous workers as evidence that those units erupted as pyroclastic flows which then underwent sufficient rheomorphism to create a flow-foliated rock which otherwise appears to be lava. The textures described herein indicate that lava flows can come to mimic rheomorphic ignimbrites, at least at scales ranging from thin sections to outcrops. Voluminous silicic units with scattered fragmental textures, but with otherwise lava-like features, are probably true effusive lava flows.

  14. Mineral resource of the month: perlite (United States)



    The article talks about perlite, which is a mineral used as an aggregate for lightweight construction products, filler for paints and horticultural soil blends. Perlite comes from viscous lava, mined and processed to produce lightweight material that competes with pumice, exfoliated vermiculite and expanded clay and shale. It is mined in about 35 countries that include Greece, Japan and the U.S. Other uses include insulation, concrete and plaster aggregate, and stonewashing.

  15. Microabrasion as treatment of enamel fluorosis

    Directory of Open Access Journals (Sweden)

    Ana Caroline Brito


    Full Text Available There is currently a trend in favor of using fluoride as a coadjuvant in reducing caries indexes, as much in underdeveloped as in developedcountries. However, simultaneously the indexes of dental fluorosis seem to grow in an inverse proportion. This is brought about by chronic ingestion of fluoride for a prolonged length of time or in high concentration. Enamel microabrasion is an effective method to remove superficial stains caused by this condition, which affects esthetics of that tissue. The use of 18% hydrochloric acid in association with pumice, despite being a simple and low cost method, has been gradually replaced due to its potential of causing damage to periodontal tissues. Thus, this article reports the treatment of a fluorosis clinical case solved with microabrasion using phosphoric acid 37%, because its costbenefit is supposedly better than with chloridric acid. The deliberate ingestion of toothpaste was the probable cause of the tooth stains. Due to the location of the teeth and to the patient’s smile, only the six upper anterior teeth were selected to receive the proposed treatment. Four clinical sessions, with a seven days interval between each other, were carried out using 37% phosphoric acid and pumice. Under rubber dam isolation, the two first sessions consisted of rubbing the acid-pumice mix on enamel surface using a rubber cup on slow speed, and abrasive paper strips on the interproximal tooth surfaces. On the two final sessions, only finishing touches were performed using a wooden spatula to manually rub the acid-pumice paste.

  16. Recent eruptive history of Mount Hood, Oregon, and potential hazards from future eruptions (United States)

    Crandell, Dwight Raymond


    Each of three major eruptive periods at Mount Hood (12,000-15,000(?), 1,500-1,800, and 200-300 years ago) produced dacite domes, pyroclastic flows, and mudflows, but virtually no pumice. Most of the fine lithic ash that mantles the slopes of the volcano and the adjacent mountains fell from ash clouds that accompanied the pyroclastic flows. Widely scattered pumice lapilli that are present at the ground surface on the south, east, and north sides of Mount Hood may have been erupted during the mid-1800's, when the last known activity of the volcano occurred. The geologically recent history of Mount Hood suggests that the most likely eruptive event in the future will be the formation of another dome, probably within the present south-facing crater. The principal hazards that could accompany dome formation include pyroclastic flows and mudflows moving from the upper slopes of the volcano down the floors of valleys. Ash clouds which accompany pyroclastic flows may deposit as much as a meter of fine ash close to their source, and as much as 20 centimeters at a distance of 11 kilometers downwind from the pyroclastic flows. Other hazards that could result from such eruptions include laterally directed explosive blasts that could propel rock fragments outward from the sides of a dome at high speed, and toxic volcanic gases. The scarcity of pumiceous ash erupted during the last 15,000 years suggests that explosive pumice eruptions are not a major hazard at Mount Hood; thus, there seems to be little danger that such an eruption will significantly affect the Portland (Oregon) metropolitan area in the near future.

  17. Scanning Electron Microscopy and Petrography of Glassy Particles Produced by Lava Fountain Eruptions. Ph.D. Thesis - Final Report (United States)

    Ladle, G. H.


    A conceptual model of a lava fountain consists of a vent, spatter ramparts, fountain column, downwind plume and associated pumice deposits. Glassy particles produced by lava fountain eruptions consist primarily of sideromelane glass and minor to moderate amounts of vesicles and crystals. Particles are classified on the basis of morphology as: (1) spherical, (2) elongate, (3) glass-coated mineral grain, (4) shard, (5) reticulite, (6) composite particle, and (7) lithic fragment.

  18. Geology and geothermal potential of Alid Volcanic Center, Eritrea, Africa

    Energy Technology Data Exchange (ETDEWEB)

    Clynne, M.A.; Duffield, W.A.; Fournier, R.O.; Janik, C.J. [and others


    Alid volcanic center is a 700-meter-tall mountain in Eritrea, northeast Africa. This mountain straddles the axis of an active crustal-spreading center called the Danakil Depression. Though volcanism associated with this crustal spreading is predominantly basaltic, centers of silicic volcanism, including Alid, are present locally. Silicic centers imply a magma reservoir in the crust and thus a possible potent shallow heat source for a hydrothermal-convection system. Boiling-temperature fumaroles are common on Alid, and their gas compositions indicate a reservoir temperature of at least 250{degrees}C. Alid is a 7-km x 5-km structural dome. The domed rocks, in decreasing age, are Precambrian schist and granite, a sequence of intercalated sedimentary rocks and basaltic lavas, and a sequence of basaltic and rhyolitic lava flows. Though isotopic ages are not yet determined, the domed volcanic rocks of Alid appear to be late Tertiary and/or Quaternary. Doming was likely caused by intrusion of relatively low density silicic magma into the upper crust. Subsequent to dome formation, a substantial volume of this magma was erupted from a vent near the west end of the summit area of the dome. This eruption produced a blanket of plinian rhyolite pumice over most, if not all, of the dome and fed pyroclastic flows that covered the part of the Danakil Depression around the base of the dome. The pumice deposits contain abundant inclusions of granophyric, miarolitic pyroxene granite, chemically indistinguishable from the pumice. This granite likely represents the uppermost part of the magma reservoir, which crystallized just prior to the pumice eruption.

  19. Divergent late-stage crystal records in melt domains from the Youngest Toba Tuff, Sumatra, Indonesia (United States)

    Tierney, C. R.; Reid, M. R.; Vazquez, J. A.; Chesner, C. A.


    The voluminous 74 ka Youngest Toba Tuff (YTT) ejected an enormous >1000 km3 of high-silica (>74 wt.% SiO2) rhyolite (HSR). Based on melt inclusion morphology, quartz crystallized at least several thousand years before eruption in the dominant HSR melt domain represented by moderately crystalline pumices (HSR-A; 12-25% crystals). Quartz crystallized within a couple thousand years of eruption in melts represented by rare crystal-poor pumices (HSR-B; 175 kyr before eruption for HSR-A zircon and allanite, and to 100 kyr (zircon) and 75 kyr (allanite) for the HSR-B. Additionally, HSR-B pumices have a higher proportion of crystals with detectable eruption-aged rim growth than HSR-A in zircon ( 60 vs 50%) and especially allanite ( 80 vs 40%). Rim compositions, except for HSR-B allanite, are heterogeneous, even in crystals that date to within error of eruption. Shallow depth profiles reveal that rim and near-rim growth may either be relatively continuous, or mantle distinctly older and different interior zones. The diversity in rim ages shows that individual crystals were not always at conditions suitable for detectable growth, either due to stagnation of magmatic conditions, or inclusion in other phases or crystal aggregates. Heterogeneity in rim ages and compositions of zircon and allanite within the same HSR pumice reveals a dynamic system involving migration and mixing of crystals with diverse histories. Coupled with the distinct differences in quartz crystallization, the relative youthfulness of rims and greater affinity of allanites to each other indicate the HSR-B may have experienced different conditions of magmatic storage than the HSR-A. In addition, there may have been less mixing of non-cognate crystals into the HSR-B domain. Although growth of individual crystals was sometimes interrupted, the diverse and continuous distribution of rim ages imply a sustained 175 ka history of melt residence and accumulation for the YTT overall.

  20. Isogloss: language and legacy on Mount St. Helens (United States)

    E. Dodd


    Nothing standing aboveground today was here thirty years ago. The ground itself wasn't here. Oh, there was ground, but much of it lay below the surface where my boot soles slip a little in the loose pebbles of pumice. Rolling on loose rock and big ideas, for a moment I lose my sense of balance, glancing first at the sky above, then at the nearby peak of Mount St...

  1. Effects of microabrasion on substance loss, surface roughness, and colorimetric changes on enamel in vitro


    Paic, M; Sener, B.; Schug, J.; Schmidlin, P.R


    OBJECTIVES: To determine in vitro the effects of 2 commercially available microabrasion compounds (Prema [Premiere Dental Products] and Opalustre [Ultradent]) on human enamel under standardized conditions after treatment periods of 10, 20, 30, and 40 seconds. Nonacidified pumice served as an abrasive control compound. METHOD AND MATERIALS: Mean substance loss was determined by measuring dissolved Ca2+ using atomic absorption spectrophotometry. Differences in the mean surface roughness were pr...

  2. Enamel microabrasion: An overview of clinical and scientific considerations


    Pini, Núbia Inocencya Pavesi; Sundfeld-Neto, Daniel; Aguiar, Flavio Henrique Baggio; Sundfeld, Renato Herman; Martins, Luis Roberto Marcondes; Lovadino, José Roberto; Lima, Débora Alves Nunes Leite


    Superficial stains and irregularities of the enamel are generally what prompt patients to seek dental intervention to improve their smile. These stains or defects may be due to hypoplasia, amelogenesis imperfecta, mineralized white spots, or fluorosis, for which enamel microabrasion is primarily indicated. Enamel microabrasion involves the use of acidic and abrasive agents, such as with 37% phosphoric acid and pumice or 6% hydrochloric acid and silica, applied to the altered enamel surface wi...

  3. Age and whole rock glass compositions of proximal pyroclastics from the major explosive eruptions of Somma-Vesuvius: A review as a tool for distal tephrostratigraphy (United States)

    Santacroce, Roberto; Cioni, Raffaello; Marianelli, Paola; Sbrana, Alessandro; Sulpizio, Roberto; Zanchetta, Giovanni; Donahue, Douglas J.; Joron, Jean Louis


    A review of compositional data of the major explosive eruptions of Vesuvius is presented, comparing compositions (major elements) of whole rock with glass shards from the proximal deposits, hopefully useful for long-distance correlation. A critical review of published and new geochronological data is also provided. All available 14C ages are calibrated to give calendar ages useful for the reconstruction of the volcanological evolution of the volcanic complex. The pyroclastic deposits of the four major Plinian eruptions (22,000 yr cal BP "Pomici di Base", 8900 yr cal BP "Mercato Pumice", 4300 yr cal BP "Avellino Pumice", and A.D. 79 "Pompeii Pumice") are widely dispersed and allow a four-folded, Plinian to Plinian, stratigraphic division: 1. B-M (between Pomici di Base and Mercato); 2. M-A (between Mercato and Avellino); 3. A-P (between Avellino and Pompeii); 4. P-XX (from the Pompeii Pumice to the last erupted products of the XXth century). Within each interval, the age, lithologic and compositional features of pyroclastic deposits of major eruptions, potentially useful for tephrostratigraphic purposes on distal areas, are briefly discussed. The Vesuvius rocks are mostly high Potassic products, widely variable in terms of their silica saturation. They form three groups, different for both composition and age: 1. slightly undersaturated, older than Mercato eruption; 2. mildly undersaturated, from Mercato to Pompeii eruptions; 3. highly undersaturated, younger than Pompeii eruption. For whole rock analyses, the peculiar variations in contents of some major and trace elements as well as different trends in element/element ratios, allow a clear, unequivocal, easy diagnosis of the group they belong. Glass analyses show large compositional overlap between different groups, but selected element vs. element plots are distinctive for the three groups. The comparative analysis of glass and whole rock major element compositions provides reliable geochemical criteria helping

  4. A Technique for Staining Extracted Teeth: A Research and Teaching Aid for Bleaching. (United States)


    anterior teeth with intact crowns were scaled with an ultrasonic scalero and polished with a rubber cup and pumice to remove all extrinsic debris. A 35mm...patient and the dentist.4 Hence, the bleaching of these discolored non-vital teeth becomes an extremely important phase of endodontic therapy. 1-6...dentists at the Edward C. Penick Endodontic Study Club stated they never bleached a tooth as an undergraduate. Six chairmen of dental school

  5. State summaries: Idaho (United States)

    Gillerman, V.S.; Weaver, M.J.; Bennett, E.H.


    According to the United States Geological Survey (USGS), Idaho's preliminary nonfuel mineral production value jumped to $893 million in 2005. Principal minerals by value included molybdenum concentrates, phosphate rock, sand and gravel, silver and portland cement. The state ranked second in phosphate and garnet production, third in silver and pumice, fourth in molybdenum concentrate production, and 21st overall. Majority of mining increases for the year were spurred by demand for metals by China's growing economy.

  6. Management of Post-orthodontic White Spot Lesions and Subsequent Enamel Discoloration with Two Microabrasion Techniques

    Directory of Open Access Journals (Sweden)

    Arezoo Jahanbin


    Full Text Available Statement of the Problem: Demineralization of enamel adjacent to orthodontic appliances frequently occurs, commonly due to insufficient oral hygiene. Purpose: The aim of this study was to compare two microabrasion techniques on improving the white spot lesions as well as subsequent enamel discoloration. Materials and Method: Sixty extracted premolar teeth without caries and hypo-plasia were selected for this study. White spot lesions were artificially induced on the buccal surface of each tooth. Teeth were randomly assigned to three treatment groups, each treated with pumice powder as the control, microabrasion with 18% HCl, and microabrasion with 37% H3PO4. Subsequently, the three groups were daily immersed for five minutes in a tea-coffee solution for a period of one week. Colorimetric evaluation was done before and after formation of white spot lesions, after microabrasion, and after immersion in the colored solution; then the color differences (∆E were calculated. Statistical analysis was performed by multiple measurement analysis and the Tukey’s test. Results: This study showed that ∆E between the stages of white spot formation and microabrasion for H3PO4 was more than other groups and for the pumice powder group it was less than the others. Furthermore, there was a significant difference between ∆E of the three study groups (p= 0.017. Additionally, ∆E after placing the teeth in the colored solution and microabrasion was the highest for the HCl group and the lowest for the pumice powder group. There was also a significant difference between the three groups (p= 0.000. Conclusion: Pumice powder alone had similar effects as 18% HCl on removing the white spot lesions. Nevertheless, 18% HCl makes the enamel susceptible for subsequent color staining more than the other microabrasion methods.


    Directory of Open Access Journals (Sweden)

    Darsigunta Seshaiah


    Full Text Available Blended aggregate in concrete and arriving at the structural properties of blended aggregate concrete is a thrust area. Pumice is very light and porous igneous rock that is formed during volcanic eruptions.Cinder is a waste material obtained from steel manufacturing units. Shear strength is a property of major significance for wide range of civil engineering materials and structures. Shear and punching shear failures particularly in deep beams, in corbels and in concrete flat slabs are considered to be more critical and catastrophic than other types of failures. This area has received greater attention in recent years. For investigating shear type of failures, from the literature it is found that double central notched (DCN specimen geometry proposed by Prakash Desai and V.Bhaskar Desai is supposed the best suited geometry. In this present experimental investigation an attempt is made to study the Mode-II fracture property of light weight blended aggregate cement concrete combining both the pumice and cinder in different proportions, and making use of DCN test specimen geometry . By blending the pumice and cinder in different percentages of 0, 25, 50, 75 and 100 by volumeof concrete, a blended light weight aggregate concrete is prepared. By using this the property such as in plane shear strength is studied. Finally an analysis is carried out regarding Mode-II fracture properties of blended concrete. It is concluded that the Ultimate load in Mode-II is found to decrease continuously with the percentage increase in Pumice aggregate content. It is also observed that the ultimate stress in Mode II is found to increase continuously with percentage increase in cinder aggregate content.

  8. Late Quaternary Tephrostratigraphy of South-Central Chile (~ 38 - 40 °S) (United States)

    Fontijn, K.; Rawson, H. L.; Van Daele, M. E.; Moernaut, J.; Abarzúa, A. M.; Pyle, D. M.; Mather, T. A.; De Batist, M. A. O.; Moreno-Roa, H.; Naranjo, J. A.


    The volcanoes of the Siete Lagos region ("Lake District") in South-Central Chile form part of the Southern Volcanic Zone of the Andes and include some of the most active volcanoes in South America, i.e. Villarrica and Llaima. The Late Quaternary (~ last 15 ka) regional tephrostratigraphic record for this region is however still poorly developed. We combine detailed stratigraphic logging of terrestrial sections in the vicinity of Llaima, Sollipulli, Villarrica, Quetrupillan, Mocho-Choshuenco and Puyehue-Cordón Caulle volcanoes with petrological, whole-rock and glass geochemical data, and 14C dating on charcoal entrained in volcanic deposits, and correlate the on-land sequences with tephra layers in existing 14C-dated lacustrine records of Laguna Las Ranas and Lagos Villarrica, Calafquén and Riñihue. The combined record includes previously described major eruptions, e.g. Llaima Pumice (Llaima) and Alpehue Pumice (Sollipulli), which help to constrain the relative timing of events. These correlations suggest that several widespread volcanic units are several hundreds to thousands of years older than previously thought. The record also includes newly described pumice-producing events, e.g. for the poorly studied Quetrupillan volcano, and provides new insights into the post-glacial eruptive frequency in the Southern Volcanic Zone. The newly updated stratigraphy with high-quality geochemical data also contributes to the regional tephrochronological framework which helps to significantly improve age models for lacustrine palaeoseismological and palaeoenvironmental archives.

  9. Natural microbial populations in a water-based biowaste management system for space life support (United States)

    Bornemann, Gerhild; Waßer, Kai; Tonat, Tim; Moeller, Ralf; Bohmeier, Maria; Hauslage, Jens


    The reutilization of wastewater is a key issue with regard to long-term space missions and planetary habitation. This study reports the design, test runs and microbiological analyses of a fixed bed biofiltration system which applies pumice grain (16-25 mm grain size, 90 m2 /m3 active surface) as matrix and calcium carbonate as buffer. For activation, the pumice was inoculated with garden soil known to contain a diverse community of microorganisms, thus enabling the filtration system to potentially degrade all kinds of organic matter. Current experiments over 194 days with diluted synthetic urine (7% and 20%) showed that the 7% filter units produced nitrate slowly but steadily (max. 2191 mg NO3-N/day). In the 20% units nitrate production was slower and less stable (max. 1411 mg NO3-N/day). 84% and 76% of the contained nitrogen was converted into nitrate. The low conversion rate is assumed to be due to the high flow rate, which keeps the biofilm on the pumice thin. At the same time the thin biofilm seems to prevent the activity of denitrifiers implicating the existence of a trade off between rate and the amount of nitrogen loss. Microbiological analyses identified a comparatively low number of species (26 in the filter material, 12 in the filtrate) indicating that urine serves as a strongly selective medium and filter units for the degradation of mixed feedstock have to be pre-conditioned on the intended substrates from the beginning.

  10. Comparison of different methods of cleaning and preparing occlusal fissure surface before placement of pit and fissure sealants: An in vivo study

    Directory of Open Access Journals (Sweden)

    Rahul J Hegde


    Full Text Available Aim: To evaluate an individual method of cleaning and preparing occlusal fissure surface before placement of pit and fissure sealant and to determine a method for better retention of the sealant. Materials and Methods: The present study consisted of 100 young permanent molar teeth divided into four equal groups: Group 1-Brushing only, Group 2-Application of pumice slurry, Group 3-Surface conditioning, and Group 4-Control (without any preparation. Subsequent to fissure preparation, the fissures were etched using 37% phosphoric acid except for Group 3, which was etched using 10% maleic acid for 30 s. The samples were then rinsed for 10 s using air water spray of the three-way syringe and dried using oil-free compressed air with a hand pump air pressure syringe. After ensuring a frosted appearance of the enamel at the fissure entrance, pit and fissure sealants were applied on the surface according to manufacturer′s instructions. All the cases were clinically evaluated for retention after 3 months, 6 months, and 12 months of application and the retention rate was assessed based on the criteria proposed by Simonsen. Results: The pumice slurry group and surface conditioning group showed results with 100%, 96%, and 92% complete retention seen at 3 months, 6 months, and 12 months, respectively. Conclusion: The pumice slurry group and surface conditioning group showed a significantly higher retention when compared to the brushing group, whereas the control group (without any preparation showed the least retention when compared to all the other groups.

  11. Effects of Microabrasion on non Active White Spots in Primary Teeth

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    Carolina Júdica RAMOS


    Full Text Available Objective: The aim of this study was to verify the enamel micromorphology with non active white spot lesions after the application of two different compounds used in microabrasion technique. Method: Thirty primary molars with non active white spot lesions in approximal surfaces were selected. Samples were randomly divided into three groups. G1 (n=10: control, untreated. G2 (n=10: compound (35% phosphoric acid and pumice mixed - 1:1 was applied on stain enamel. G3 (n=10: compound Opalustre, a slurry containing 6.6% HCl (hydrochloric acid and silicon carbide microparticles was applied. After this, all specimens were dehydrated, mounted on metal stubs, coated with gold and examined under scanning electron microscope (Jeol, JSM - 6100. Results: Eletronmicrographs analysis showed that the G1 samples (control, without treatment had a smooth surface with the presence of pumice residue. G2 samples (phosphoric acid and pumice presented rugous enamel surface with areas of enamel prisms demineralization. In G3 samples (Opalustre it were observed the formation of scratchs and grooves, beyond the presence of compound residue. Conclusion: The application of different types of compounds led to the formation of different aspects in micromorphology of primary teeth enamel.

  12. Eruptive dynamics of the “Citlaltépetl Pumice” at Citlaltépetl volcano, Eastern Mexico (United States)

    Rossotti, Andrea; Carrasco-Núñez, Gerardo; Rosi, Mauro; Di Muro, Andrea


    Citlaltépetl (Pico de Orizaba) is Mexico's highest (5675 m a.s.l.) potentially active volcano, which is presently in a dormant state. Between 9.0 and 8.5 ky B.P., a sequence of volcanic eruptions occurred at Citlaltépetl volcano as part of the most explosive Holocene episode. This sequence is associated with the deposition of an intercalation of pumice fallout and scoria and pumice-rich pyroclastic flow deposits, named here as "Citlaltépetl Pumice" (C.P.). Detailed stratigraphic and petrographic correlation of over 100 measured sections, in conjunction with the analysis of the physical characteristics of the juvenile and lithic portions of each main layer of the sequence, provided the basis to reconstruct the eruptive episodes and to assert the eruptive dynamics of the whole sequence, which was divided into eight main eruptions separated by three brief periods of quiescence. The eruption sequence started with a phreatic phase that soon developed into a bread-crusted, bomb-bearing phase. This was followed by a sequence of vigorous Plinian explosive eruptions separated by brief periods of repose and a short dome-collapse activity. It was followed by another cycle of alternated scoria pyroclastic flows-forming and Plinian activity. This eruptive sequence shows the complexity of single eruptive events with alternated contrasting styles suggested by the compositional differences between the pyroclastic flow and fallout products.

  13. Hybrid fall deposits in the Bishop Tuff, California: A novel pyroclastic depositional mechanism (United States)

    Wilson, C.J.N.; Hildreth, W.


    Hybrid fall deposits in the Bishop Tuff show features common to both archetypal fall and surge deposits. Like normal-fall deposits, they have an overall plane-parallel bedding and flat-lying pumice clasts but also, like surge deposits, they show variable development of cross-bedding, some crystal and pumice sorting, and some rounding of pumice clasts. All variations exist from normal-fall deposits, through streaky material with incipient development of cross-bedding, to the hybrid fall deposits with well-developed cross-bedding. The streaky and hybrid deposits are interpreted as fall material contemporaneously redeposited by strong (up to 40 m/s) swirling winds, comparable to firestorm whirlwinds, generated by air currents associated with coeval emplacement of pyroclastic flows. Recognition of hybrid fall deposits is important in interpreting the dynamics of explosive eruptions and correctly assessing volcanic hazards. However, although such deposits may be commonly produced by explosive eruptions, especially where pyroclastic flows accompany fall activity, they are likely to be overlooked, or wrongly interpreted as surge deposits or secondary, reworked material.

  14. Pyroclastic deposits as a guide for reconstructing the multi-stage evolution of the Somma-Vesuvius Caldera (United States)

    Cioni, Raffaello; Santacroce, Roberto; Sbrana, Alessandro

    The evolution of the Somma-Vesuvius caldera has been reconstructed based on geomorphic observations, detailed stratigraphic studies, and the distribution and facies variations of pyroclastic and epiclastic deposits produced by the past 20,000years of volcanic activity. The present caldera is a multicyclic, nested structure related to the emptying of large, shallow reservoirs during Plinian eruptions. The caldera cuts a stratovolcano whose original summit was at 1600-1900m elevation, approximately 500m north of the present crater. Four caldera-forming events have been recognized, each occurring during major Plinian eruptions (18,300 BP "Pomici di Base", 8000 BP "Mercato Pumice", 3400 BP "Avellino Pumice" and AD 79 "Pompeii Pumice"). The timing of each caldera collapse is defined by peculiar "collapse-marking" deposits, characterized by large amounts of lithic clasts from the outer margins of the magma chamber and its apophysis as well as from the shallow volcanic and sedimentary units. In proximal sites the deposits consist of coarse breccias resulting from emplacement of either dense pyroclastic flows (Pomici di Base and Pompeii eruptions) or fall layers (Avellino eruption). During each caldera collapse, the destabilization of the shallow magmatic system induced decompression of hydrothermal-magmatic and hydrothermal fluids hosted in the wall rocks. This process, and the magma-ground water interaction triggered by the fracturing of the thick Mesozoic carbonate basement hosting the aquifer system, strongly enhanced the explosivity of the eruptions.

  15. Textural analysis of tephra from a rhyodacitic eruption sequence, Thira (Santorini), Greece

    Energy Technology Data Exchange (ETDEWEB)

    Heiken, G.


    The Minoan eruption sequence of 1390 B.C. produced a minimum volume of 13 km/sup 3/ of rhyodacitic tephra (dense rock equivalent). The eruptions evolved from magmatic to phreatomagmatic and back to a mix of both processes. Thin section and scanning electron micrograph analysis of the tephra sequence provide information about eruption processes that is critical to interpretation of the field data. The eruptions began at a vent located above sea level and produced a coarse-grained Plinian pumice deposit. All later phases of the eruption involved propagating vent(s) into an older flooded caldera and flooding of the sea into a collapsing Minoan caldera. Interaction of magma and water produced fine-grained tephra that consist mostly of slightly curved, nearly flat shards and small pumice pyroclasts. These were derived during fragmentation of a heterogeneous, vesicular magma containing large compound vesicles and smaller, elongate vesicles. The vesiculated magma was thoroughly comminuted during magma-water interactions. The last eruptive phase is interpreted as having involved both magmatic and phreatomagmatic processes. Hot pyroclastic flows from this phase contained a bimodal mixture of pumice pyroclasts and finely comminuted shards.

  16. Pre-eruptive conditions of the ~31 ka rhyolitic magma of Tlaloc volcano, Sierra Nevada Volcanic Range, Central Mexico (United States)

    Macias, J.; Arce, J.; Rueda, H.; Gardner, J.


    Tlaloc volcano is located at the northern tip of the Sierra Nevada Volcanic Range in Central Mexico. This Pleistocene to Recent volcanic range consists from north to south of Tlaloc-Telapón-Teyotl-Iztaccíhuatl-and- Popocatépetl volcanoes. While andesitic to barely dacitic volcanism dominates the southern part of the range (i.e. Popocatépetl and Iztaccíhuatl); dacitic and rare rhyolithic volcanism (i.e. Telapón, Tlaloc) dominates the northern end. The known locus of rhyolitic magmatism took place at Tlaloc volcano with a Plinian-Subplinian eruption that occurred 31 ka ago. The eruption emplaced the so-called multilayered fallout and pumiceous pyroclastic flows (~2 km3 DRE). The deposit consists of 95% vol. of juvenile particles (pumice + crystals) and minor altered lithics 5% vol. The mineral association of the pumice fragments (74-76 % wt. SiO2) consists of quartz + plagioclase + sanidine + biotite and rare oxides set in a glassy groundmass with voids. Melt inclusions in quartz phenocrysts suggest that prior to the eruption the rhyolitic contain ~7% of H2O and Toluca volcano (~6 km) some 50 km to the southwest.

  17. Melt extraction in mush zones: The case of crystal-rich enclaves at the Sabatini Volcanic District (central Italy) (United States)

    Masotta, M.; Mollo, S.; Gaeta, M.; Freda, C.


    A peculiar feature of the Sabatini Volcanic District (SVD, central Italy) is the occurrence of crystal-poor pumices and crystal-rich enclaves within the same eruptive host-deposit. The stratigraphic sequence of pumices and enclaves indicates the tapping of a stratified magma chamber, where a crystal-poor phonolitic magma lay on top of a more primitive crystal-rich magma. The crystal-rich enclaves are genetically related to the pumices and record the evolution of a solidification front, in which a more differentiated melt was produced, extracted and eventually erupted. We collected and analyzed crystal-rich enclaves from one of the largest phonolitic eruptions at the SVD and used their petrological and geochemical features to reconstruct magma differentiation and crystal-melt separation in the solidification front. On this basis, three groups of enclaves have been identified: porphyritic enclaves, holocrystalline enclaves and sanidinites. The mineralogical variability faithfully reproduces the spatial and temporal evolution expected of a solidification front, from early-to-intermediate crystallization conditions (porphyritic and holocrystalline type) to the late stage of solidification (sanidinites), in which the percolation of a more differentiated melt through the crystal mush triggered the instability of the solidification front. Results from numerical models indicate that gravitational instability is the most efficient mechanism to explain melt extraction in mush zones of medium-sized (~ 10 km3), short-lived (~ 104 years) magma chambers.

  18. Mapping the distribution of vesicular textures on silicic lavas using the Thermal Infrared Multispectral Scanner (United States)

    Ondrusek, Jaime; Christensen, Philip R.; Fink, Jonathan H.


    To investigate the effect of vesicularity on TIMS (Thermal Infrared Multispectral Scanner) imagery independent of chemical variations, we studied a large rhyolitic flow of uniform composition but textural heterogeneity. The imagery was recalibrated so that the digital number values for a lake in the scene matched a calculated ideal spectrum for water. TIMS spectra for the lava show useful differences in coarsely and finely vesicular pumice data, particularly in TIMS bands 3 and 4. Images generated by ratioing these bands accurately map out those areas known from field studies to be coarsely vesicular pumice. These texture-related emissivity variations are probably due to the larger vesicles being relatively deeper and separated by smaller septa leaving less smooth glass available to give the characteristic emission of the lava. In studies of inaccessible lava flows (as on Mars) areas of coarsely vesicular pumice must be identified and avoided before chemical variations can be interpreted. Remotely determined distributions of vesicular and glassy textures can also be related to the volatile contents and potential hazards associated with the emplacement of silicic lava flows on Earth.

  19. The evaluation of the growth and nutrition conditions of the garden nursery material Prunus and Thuja according to the use of various cultivating substrates and systems of fertilization

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    Tomáš Meisl


    Full Text Available The influence of different peat-based cultivating substrates and the system of fertilization on the nutrition conditions and growth characteristics of garden nursery material Prunus kurilensis ‘Brillant’ and Thuja occidentalis ‘Smaragd’ were observed during a three-year experiment. Three kinds of substrates were tested: peat + pumice (pemza proportioned 8:2, fermented bark + peat + clay proportioned 4:4:2, fermented bark + peat + clay proportioned 4:4:2. Two fertilizers were used: granular controlled-release fertilizer – Osmocote, and watersoluble with irrigation – Kristalon.A higher content of macroelements was observed in the leaves of Prunus. The only exception was potassium, the quantity of which was demonstrably higher in the assimilative organs of Thuja. On the contrary, Thuja had a higher content of trace elements except for copper and iron. The highest contents of nitrogen, potassium, and iron were statistically proved in leaves of woods grown in the substrate of peat and pumice due to its higher sorption capability. A better nutrition conditions in almost all nutrients were observed at plants where the gradually effective Osmocote was applied. The exceptions were calcium, molybdenum and iron, the content of which was, on the contrary, higher where Kristalon with irrigation were used. Physical characteristics of the growing substrates that contained bark were significantly worse at the end of the experiment. This was even intensified by clay. The substrate containing peat and pumice were less stable. The best growth was observed in woods grown in the substrate of peat and pumice, ie where peat was not substituted by bark, and, at the same time, expanded clay was used instead of classic clay. Higher values of growth characteristics were demonstratively observed after the Osmocote fertilizer was applied.The results of the experiment reveal that pumice should be recommended, pemza with a high sorption capability and the

  20. Remote Analysis of Grain Size Characteristic in Submarine Pyroclastic Deposits from Kolumbo Volcano, Greece (United States)

    Smart, C.; Whitesell, D. P.; Roman, C.; Carey, S.


    Grain size characteristics of pyroclastic deposits provide valuable information about source eruption energetics and depositional processes. Maximum size and sorting are often used to discriminate between fallout and sediment gravity flow processes during explosive eruptions. In the submarine environment the collection of such data in thick pyroclastic sequences is extremely challenging and potentially time consuming. A method has been developed to extract grain size information from stereo images collected by a remotely operated vehicle (ROV). In the summer of 2010 the ROV Hercules collected a suite of stereo images from a thick pumice sequence in the caldera walls of Kolumbo submarine volcano located about seven kilometers off the coast of Santorini, Greece. The highly stratified, pumice-rich deposit was likely created by the last explosive eruption of the volcano that took place in 1650 AD. Each image was taken from a distance of only a few meters from the outcrop in order to capture the outlines of individual clasts with relatively high resolution. Mosaics of individual images taken as the ROV transected approximately 150 meters of vertical outcrop were used to create large-scale vertical stratigraphic columns that proved useful for overall documentation of the eruption sequence and intracaldera correlations of distinct tephra units. Initial image processing techniques, including morphological operations, edge detection, shape and size estimation were implemented in MatLab and applied to a subset of individual images of the mosiacs. A large variety of algorithms were tested in order to best discriminate the outlines of individual pumices. This proved to be challenging owing to the close packing and overlapping of individual pumices. Preliminary success was achieved in discriminating the outlines of the large particles and measurements were carried out on the largest clasts present at different stratigraphic levels. In addition, semi-quantitative analysis of the

  1. Perhitungan Volume dan Karakterisasi Material Endapan Erupsi Gunungapi Kelud Tahun 2014, di Sungai Bladak Bagian Hulu Dengan Metode Geofisika

    Directory of Open Access Journals (Sweden)

    Anastasia Neni Candra Purnamasari


    Full Text Available ABSTRAK Erupsi Gunungapi Kelud pada 13 Februari 2014 menghasilkan material endapan di hulu Sungai Bladak dalam jumlah yang sangat besar.Endapan hasil erupsi yang terdapat di hulu sungai berpotensi sebagai material lahar bagi wilayah di hilir.Upaya mitigasi untuk mengurangi bencana banjir lahar memerlukan informasi volume material endapan. Selain itu, informasi karakteristik fisik material endapan juga penting untuk pemanfaatannya bagi masyarakat. Penelitian untuk mengetahui volume material endapan dilakukan dengan menggunakan metode geofisika pada pengukuran ketebalan dari material endapan.Metode geofisika yang digunakan adalah metode mikroseismik dan metode seismik refraksi.Hasil yang didapatkan dari pengolahan data lapangan mikroseismik adalah nilai frekuensi natural (f0 dari setiap titik pengukuran mikroseismik. Hasil yang didapatkan dari pengolahan data lapangan seismik refraksi adalah kecepatan gelombang P dari material endapan, dimana kecepatan gelombang P akan diturunkan sehingga didapatkan kecepatan gelombang S. Kecepatan gelombang S akan digunakan untuk penghitungan ketebalan material endapan yang digabungkan dengan nilai frekuensi natural dengan rumus h=Vs/4f0. Berdasarkan ketebalan material endapan yang didapatkan dari hasil penghitungan setiap titik mikroseismik, kemudian dibuat kontur ketebalan material endapan dan dilakukan penghitungan volume material endapan. Karakterisasi material endapan dilakukan dengan cara menghitung persentase pumice dan nonpumice secara fisual menggunakan foto lapangan. Ketebalan endapan pumice di permukaan lahan dianalisis persebarannya menurut satuan-satuan lereng. Volume material endapan yang didapatkan dari hasil penelitian sebesar 27,6 juta m3. Hasil karakterisasi material diketahui bahwa pumice pada material endapan yang ada di hulu Sungai Bladak 91,82 % dan sisanya 7,18 % adalah nonpumice. Jumlah pumice yang sangat banyak tersebut merupakan sumberdaya alam yang bernilai ekonomi tinggi. Pumice dapat

  2. Combining Experimental Petrology and 3D Imaging to Gain Insight into Syn-eruptive Conditions of the Bishop Tuff, California (United States)

    Chattin, Archer; Pamukcu, Ayla; Gardner, James; Gualda, Guilherme


    The Bishop tuff is a rhyolitic ignimbrite deposited by a supereruption 0.76 million years ago that formed the Long Valley Caldera in California, USA. Pamukcu et. al (2012) identifies two distinct crystal populations present in the Bishop Tuff, the first being a long-lived, large phenocryst population that records storage conditions, and the second a rapidly nucleated, quickly staunched microlite population thought to result from eruptive decompression. Laboratory experiments to reproduce this quickly grown population may help constrain the conditions and rates under which decompression took place. Rapid nucleation of microlites is accompanied by just as rapid bubble nucleation when volatiles exsolve during decompression; the size distribution of vesicles in eruptive products may thus provide important information on syn-eruptive processes. In this study we combine information from vesicle size distributions on natural pumice with data on experimentally produced microlite crystals with the goal of better understanding the syn-eruptive evolution of a supereruption-forming magma body. Decompression experiments are run using a natural Bishop tuff pumice clast ground and melted in the presence of water to obtain a melt representative of late-erupted Bishop Tuff (LBT) magmas. Experimental charges were subjected to decompression at varying rates and initial temperatures. At this time five experiments have been completed. All decompression experiments start at 130MPa, consistent with water concentration in LBT glass inclusions, and end at 10 MPa. Initial temperatures are either 710°C or 785°C, while decompression rates are 20 MPa/hr, 5.5MPa/hr, or 1.7MPa/hr Experimental products were compared to natural products using Scanning Electron Microscopy to document eventual crystal rims and microlites. We have been successful in causing limited feldspar crystallization, but have yet to generate quartz microlites. Bubble size distributions are obtained by analyzing x

  3. New stratigraphic, chronologic, and magnetic fabric constraints for Neogene and Quaternary ignimbrites in the Central Andes (South Peru) (United States)

    De La Rupelle, A.; Thouret, J. C.; Cubukcu, H. E.; Jicha, B.; Bréard, E.; Gerbe, M.-C.; Le Pennec, J.-L.; Diot, H.; Boivin, P.


    Central Andean deformation history in southern Peru is recorded in Neogene volcanic units of Ocoña and Cotahuasi canyons that cut across the western Cordillera. Acceleration (100 km3) Nazca (c.24.6 Ma), Alpabamba (19.4-18.0 Ma), and Huaylillas (14.25-12.7 Ma) ignimbrite sheets preceded the canyon incision, whereas sheets of smaller volume (welded, eutaxitic, crystal-rich facies overlain by a thick, multi-bedded ash-flow tuff and a lithic-rich, indurated flow unit. The Huaylillas ignimbrite sheet comprises a strongly welded, crystal-rich, lithic-poor, columnar lithofacies, with devitrified pumice. The Caraveli ignimbrite sheet has a jointed vitrophyre overlain by a welded, blocky, crystal-rich flow unit. A vacuolar, saccharolytic unit forms the top of the sequence. The Lower Sencca ignimbrite sheet comprises of a basal vitrophyre and a slightly welded, fibrous pumice-rich flow unit, which grades into a welded, vapor-phase unit that contains more crystals than pumice and lithics. The Upper Sencca ignimbrite sheet consists of a black vitrophyre, grading into a strongly welded, crystal-rich, eutaxitic cooling unit. The latter is capped by a slightly welded unit, and an indurated pumice-rich, crystal-poor vapour-phase facies. Quaternary valley-fill termed Las Lomas consists of unwelded, crystal-poor pumice-flow deposits. Eighteen new 40Ar/39Ar analyses have been carried out on feldspar/glass separates from pumice and lavas. Results for the Caraveli ignimbrite (9.35±0.06 Ma), Upper Barroso lavas (2.24±0.45 Ma) and Upper Sencca ignimbrite (2.00-2.06±0.09 Ma) are in good agreement with previous data. New ages for the Lower Barroso lavas (7.32±0.05; 5.36±0.12 Ma) and Lower Sencca ignimbrites (5.13±0.01, 5.09±0.03, 4.65±0.11, 4.36 ± 0.16) extend their temporal history towards older times. Lower Barroso lava flow activity occurred as early as~7.3 and lasted until 5.4 Ma just before the Lower Sencca eruptions. The Lower Sencca ignimbrites spanned at least 1.5 Ma and

  4. An Early Holocene Eruptive Period at Mount Rainier, Washington (United States)

    Byman, J.; Vallance, J. W.


    Tephrochronologic studies indicate that the Cowlitz Park eruptive period at Mount Rainier began about 7500 years ago and continued intermittently until about 6800 years ago. Stratigraphic evidence suggests that Cowlitz Park time comprises four distinct eruptive episodes, each of which occurred during a relatively brief interval. The eruptions produced subplinian falls, several small ash falls, pyroclastic flows, and lahars, the largest of which swept down the White River valley to Puget Sound lowland. Tephra layers are of two types: vesicle rich (chiefly pumice lapilli, scoria, and ash) and vesicle poor (chiefly fine-grained glass and lithic fragments). Pumice and glass shards in vesicle-rich deposits are microlite-poor and derive from larger explosive eruptions. Glass shards in vesicle-poor ashes have variable microlite contents and derive from smaller explosions, or from ash clouds that billow up from block-and-ash pyroclastic flows. Although the Pleistocene record indicates considerable effusive activity at Mount Rainier, no record remains of lavas that might have erupted during Cowlitz Park time. The oldest eruption, ca 7500 cal yr BP, produced vesicular tephra "A," distributed to the east, with a volume of 5 x 106 m3. Layer A is pumiceous, but fine-grained, glassy layers, suggestive of ash-clouds derived from pyroclastic flows, bracket it stratigraphically. About 7300 cal yr BP, within a short interval of time, a more complex eruptive episode occurred that produced a subplinian fall, at least 3 minor ash layers and an avalanche of hydrothermally altered rock on the south flank of the volcano that generated a lahar. The subplinian layer, "L," was among the most voluminous in the Holocene 30 x 106 m3 at Mount Rainier. This tephra occurs to the southeast and chiefly contains pumice along with subordinate, juvenile, lithic clasts. Related fine-to-coarse-grained ash layers derive from small explosions that occurred shortly before and after the eruption of layer L

  5. Natural microbial populations in a water-based biowaste management system for space life support. (United States)

    Bornemann, Gerhild; Waßer, Kai; Tonat, Tim; Moeller, Ralf; Bohmeier, Maria; Hauslage, Jens


    The reutilization of wastewater is a key issue with regard to long-term space missions and planetary habitation. This study reports the design, test runs and microbiological analyses of a fixed bed biofiltration system which applies pumice grain (16-25 mm grain size, 90 m(2)/m(3) active surface) as matrix and calcium carbonate as buffer. For activation, the pumice was inoculated with garden soil known to contain a diverse community of microorganisms, thus enabling the filtration system to potentially degrade all kinds of organic matter. Current experiments over 194 days with diluted synthetic urine (7% and 20%) showed that the 7% filter units produced nitrate slowly but steadily (max. 2191 mg NO3-N/day). In the 20% units nitrate production was slower and less stable (max. 1411 mg NO3-N/day). 84% and 76% of the contained nitrogen was converted into nitrate. The low conversion rate is assumed to be due to the high flow rate, which keeps the biofilm on the pumice thin. At the same time the thin biofilm seems to prevent the activity of denitrifiers implicating the existence of a trade off between rate and the amount of nitrogen loss. Microbiological analyses identified a comparatively low number of species (26 in the filter material, 12 in the filtrate) indicating that urine serves as a strongly selective medium and filter units for the degradation of mixed feedstock have to be pre-conditioned on the intended substrates from the beginning. Copyright © 2015 The Committee on Space Research (COSPAR). Published by Elsevier Ltd. All rights reserved.

  6. The flow dynamics of an extremely large volume pyroclastic flow, the 2.08-Ma Cerro Galán Ignimbrite, NW Argentina, and comparison with other flow types (United States)

    Cas, Ray A.F.; Wright, Heather M.; Folkes, Christopher B.; Lesti, Chiara; Porreca, Massimiliano; Giordano, Guido; Viramonte, Jose G.


    The 2.08-Ma Cerro Galán Ignimbrite (CGI) represents a >630-km3 dense rock equivalent (VEI 8) eruption from the long-lived Cerro Galán magma system (∼6 Ma). It is a crystal-rich (35–60%), pumice (multiple depositional units, often separated by pyroclastic surge deposits. The CGI preserves a widespread sub-horizontal fabric, defined by aligned elongate pumice and lithic clasts, and minerals (e.g. biotite). A sub-horizontal anisotropy of magnetic susceptibility fabric is defined by minute magnetic minerals in all localities where it has been analysed. The CGI is poor in both vent-derived (‘accessory’) lithics and locally derived lithics from the ground surface (‘accidental’) lithics. Locally derived lithics are small (order to explain the contemporaneous maintenance of high particle concentration, high sedimentation rate at the depositional boundary layer and a high level of mobility, it is also proposed that the flow(s) was continuously supplied at a high mass feeding rate. It is also proposed that internal gas pressure within the flow, directed downwards onto the substrate over which the flow was passing, reduced the friction between the flow and the substrate and also enhanced its mobility. The pervasive sub-horizontal fabric of aligned pumice, lithic and even biotite crystals indicates a consistent horizontal shear force existed during transport and deposition in the basal granular flow, consistent with the existence of a laminar, shearing, granular flow regime during the final stages of transport and deposition.

  7. Bulk rock composition and geochemistry of olivine-hosted melt inclusions in the Grey Porri Tuff and selected lavas of the Monte dei Porri volcano, Salina, Aeolian Islands, southern Italy (United States)

    Doherty, Angela L.; Bodnar, Robert J.; De Vivo, Benedetto; Bohrson, Wendy A.; Belkin, Harvey E.; Messina, Antonia; Tracy, Robert J.


    The Aeolian Islands are an arcuate chain of submarine seamounts and volcanic islands, lying just north of Sicily in southern Italy. The second largest of the islands, Salina, exhibits a wide range of compositional variation in its erupted products, from basaltic lavas to rhyolitic pumice. The Monte dei Porri eruptions occurred between 60 ka and 30 ka, following a period of approximately 60,000 years of repose. The bulk rock composition of the Monte dei Porri products range from basaltic-andesite scoria to andesitic pumice in the Grey Porri Tuff (GPT), with the Monte dei Porri lavas having basaltic-andesite compositions. The typical mineral assemblage of the GPT is calcic plagioclase, clinopyroxene (augite), olivine (Fo72−84) and orthopyroxene (enstatite) ± amphibole and Ti-Fe oxides. The lava units show a similar mineral assemblage, but contain lower Fo olivines (Fo57−78). The lava units also contain numerous glomerocrysts, including an unusual variety that contains quartz, K-feldspar and mica. Melt inclusions (MI) are ubiquitous in all mineral phases from all units of the Monte dei Porri eruptions; however, only data from olivine-hosted MI in the GPT are reported here. Compositions of MI in the GPT are typically basaltic (average SiO2 of 49.8 wt %) in the pumices and basaltic-andesite (average SiO2 of 55.6 wt %) in the scoriae and show a bimodal distribution in most compositional discrimination plots. The compositions of most of the MI in the scoriae overlap with bulk rock compositions of the lavas. Petrological and geochemical evidence suggest that mixing of one or more magmas and/or crustal assimilation played a role in the evolution of the Monte dei Porri magmatic system, especially the GPT. Analyses of the more evolved mineral phases are required to better constrain the evolution of the magma.

  8. Heating Stage Experimental Study of Melt Inclusions in Feldspars from Three Holocene Eruptions of Changbaishan Tianchi Volcano

    Institute of Scientific and Technical Information of China (English)

    Li Ni; Nicole Métrich; Fan Qicheng


    There occurred several eruptions from Changbaishan Tianchi volcano in Holocene, and at least three of them were believed to be true according to the formal studies. The products of three eruptions were yellow comenditic pumice of - 5000a B.P. (Eruption Ⅰ), gray comenditic pumice and pyroclastic flow of - 1000a B.P. (Eruption Ⅱ, i.e. the millennium explosive eruption), black trachy pumice and welded tuff of-300a B.P. (Eruption Ⅲ) respectively. There were a large number of melt inclusions found in phenocrysts, which differ in size and color. The Leitz 1350 heating stage experiments for melt inclusions in host feldspars from three Holocene eruptions of Changbaishan Tianchi volcano imply that there were little differences between the homogenization temperatures of melt inclusions from Eruptions Ⅰ and Ⅲ, whereas it was rather complicated for Eruption Ⅱ, i.e. there might be two kinds of melt with different homogenization temperature periods, which gave the evidence for the assumption that the explosive millennium eruption of Tianchi volcano was triggered by injection and mixing of two different magmas. The experimental results also indicate that (1) small melt inclusion is easy to be homogenized, while the large one, especially the one with lots of daughter crystals, is rather difficult to be homogenized; (2) homogenization temperature closely correlates with the size of melt inclusion within host crystal, with the temperature point switching from high heating rate to low heating rate, and correlates with whether it is the first time to obtain homogenization as well; and (3) a melt inclusion can get different homogenization temperatures when it is repeatedly heated. Even more, the next homogenization temperature is usually higher than the former one, which testifies the phenomenon that hydrogen migration occurs during repeated heating.

  9. Optimization and evaluation of a bottom substrate denitrification tank for nitrate removal from a recirculating aquaculture system. (United States)

    Pungrasmi, Wiboonluk; Playchoom, Cholticha; Powtongsook, Sorawit


    A bottom substrate denitrification tank for a recirculating aquaculture system was developed. The laboratory scale denitrification tank was an 8 L tank (0.04 m2 tank surface area), packed to a depth of 5 cm with a bottom substrate for natural denitrifying bacteria. An aquarium pump was used for gentle water mixing in the tank; the dissolved oxygen in the water was maintained in aerobic conditions (e.g. > 2 mg/L) while anoxic conditions predominated only at the bottom substrate layer. The results showed that, among the four substrates tested (soil, sand, pumice stone and vermiculite), pumice was the most preferable material. Comparing carbon supplementation using methanol and molasses, methanol was chosen as the carbon source because it provided a higher denitrification rate than molasses. When methanol was applied at the optimal COD:N ratio of 5:1, a nitrate removal rate of 4591 +/- 133 mg-N/m2 tank bottom area/day was achieved. Finally, nitrate removal using an 80 L denitrification tank was evaluated with a 610 L recirculating tilapia culture system. Nitrate treatment was performed by batch transferring high nitrate water from the nitrification tank into the denitrification tank and mixing with methanol at a COD:N ratio of 5:1. The results from five batches of nitrate treatment revealed that nitrate was successfully removed from water without the accumulation of nitrite and ammonia. The average nitrate removal efficiency was 85.17% and the average denitrification rate of the denitrification tank was 6311 +/- 945 mg-N/m2 tank bottom area/day or 126 +/- 18 mg-N/L of pumice packing volume/day.

  10. Optimization and evaluation of a bottom substrate denitrification tank for nitrate removal from a recirculating aquaculture system

    Institute of Scientific and Technical Information of China (English)

    Wiboonluk Pungrasmi; Cholticha Playchoom; Sorawit Powtongsook


    A bottom substrate denitrification tank for a recirculating aquaculture system was developed.The laboratory scale denitrification tank was an 8 L tank (0.04 m2 tank surface area),packed to a depth of 5 cm with a bottom substrate for natural denitrifying bacteria.An aquarium pump was used for gentle water mixing in the tank; the dissolved oxygen in the water was maintained in aerobic conditions (e.g.> 2 mg/L) while anoxic conditions predominated only at the bottom substrate layer.The results showed that,among the four substrates tested (soil,sand,pumice stone and vermiculite),pumice was the most preferable material.Comparing carbon supplementation using methanol and molasses,methanol was chosen as the carbon source because it provided a higher denitrification rate than molasses.When methanol was applied at the optimal COD∶N ratio of 5∶1,a nitrate removal rate of 4591 ± 133 mg-N/m2 tank bottom area/day was achieved.Finally,nitrate removal using an 80 L denitrification tank was evaluated with a 610 L recirculating tilapia culture system.Nitrate treatment was performed by batch transferring high nitrate water from the nitrification tank into the denitrification tank and mixing with methanol at a COD∶N ratio of 5∶1.The results from five batches of nitrate treatment revealed that nitrate was successfully removed from water without the accumulation of nitrite and ammonia.The average nitrate removal efficiency was 85.17% and the average denitrification rate of the denitrification tank was 6311 ± 945 mg-N/m2 tank bottom area/day or 126 ± 18 mg-N/L of pumice packing volume/day.

  11. Origin of silicic volcanic rocks in Central Costa Rica: a study of a chemically variable ash-flow sheet in the Tiribí Tuff (United States)

    Hannah, Rachel; Vogel, Thomas; Patino, Lina; Alvarado, Guillermo; Pérez, Wendy; Smith, Diane


    Chemical heterogeneities of pumice clasts in an ash-flow sheet can be used to determine processes that occur in the magma chamber because they represent samples of magma that were erupted at the same time. The dominant ash-flow sheet in the Tiribí Tuff contains pumice clasts that range in composition from 55.1 to 69.2 wt% SiO2. It covers about 820 km2 and has a volume of about 25 km3 dense-rock equivalent (DRE). Based on pumice clast compositions, the sheet can be divided into three distinct chemical groupings: a low-silica group (55.1-65.6 wt% SiO2), a silicic group (66.2-69.2 wt% SiO2), and a mingled group (58.6-67.7 wt% SiO2; all compositions calculated 100% anhydrous). Major and trace element modeling indicates that the low-silica magma represents a mantle melt that has undergone fractional crystallization, creating a continuous range of silica content from 55.1-65.6 wt% SiO2. Eu/Eu*, MREE, and HREE differences between the two groups are not consistent with crystal fractionation of the low-silica magma to produce the silicic magma. The low-silica group and the silicic group represent two distinct magmas, which did not evolve in the same magma chamber. We suggest that the silicic melts resulted from partial melting of relatively hot, evolved calc-alkaline rocks that were previously emplaced and ponded at the base of an over-thickened basaltic crust. The mingled group represents mingling of the two magmas shortly before eruption. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at

  12. Digging into Augustine Volcano's Silicic Past (United States)

    Nadeau, P. A.; Webster, J. D.; Goldoff, B. A.


    Activity at Augustine Volcano, Alaska, has been marked by intermediate composition domes, flows, and tephras during the Holocene. Erosive lahars associated with the 2006 eruption exposed voluminous rhyolite pumice fall beneath glacial tills. The rhyolite is both petrologically and mineralogically different from more recent eruptions, with abundant amphibole (both calcium-amphiboles and cummingtonite) and quartz, both rare in more recent products. Three distinct lithologies are present, with textural and chemical variations between the three. Fe-Ti oxide equilibria indicate temperatures of ~765°C and oxygen fugacities of NNO +1.5. Melt inclusions indicate that the stratigraphically lowest lithology began crystallizing isobarically at ~260 MPa with the contemporary mixed H2O-CO2 fluid phase becoming progressively H2O-rich. The other lithologies were likely crystallized under more H2O-dominated conditions, as indicated by the presence of cummingtonite. Apatites and melt inclusions have generally lower chlorine contents than more recently erupted material, which is typically high in chlorine. Xenocrysts of olivine and clinopyroxene in two of the three lithologies contain mafic (basalt to basaltic andesite) melt inclusions that indicate the likelihood of mixing and/or mingling of magmas as an eruption trigger. We interpret the three lithologies as representative of a smaller pumiceous rhyolite eruption, with subsequent extrusion of a rhyodacite banded lava dome or flow. This was followed by a large-scale rhyolitic pumice eruption that entrained portions of the banded flow as lithic inclusions. The unique qualities of this pre-glacial rhyolite and the potential hazards of a similarly large eruption in modern times indicate that further study is warranted.

  13. Rejuvenation of shallow-crustal silicic magma bodies at Augustine and Hayes volcanoes, Alaska (United States)

    Coombs, M. L.; Vazquez, J. A.; Hayden, L. A.; Calvert, A. T.; Lidzbarski, M. I.; Andersen, N. L.; Till, C. B.


    Rejuvenation of crystal-rich magma bodies leading to eruption can occur on a variety of scales and in varied tectonic settings. Two examples from the Aleutian arc highlight 1) segregation of silicic melt from an intermediate mush, and 2) "defrosting" of a shallowly emplaced intrusion. Augustine Volcano erupted a late Pleistocene rhyolite pumice fall that we link through zircon geochronology to cumulate dioritic blocks, ripped from Augustine's shallow magmatic plumbing system and ejected during the 2006 eruption. Unpolished zircon rims from the rhyolite yield a U-Th age of ~25 ka, and interiors yield a dominant age population of ~26 ka. Zircons from diorites have interior ages and compositions indistinguishable from those of the rhyolite. The diorites, rhyolite, and early Holocene dacites define whole-rock linear unmixing trends consistent with melt (rhyolite) extraction from a mush (dacites), leaving behind a cumulate residue (diorites). A volatile-rich basalt erupted just prior to the rhyolite likely facilitated melt extraction from the mush. The rhyolitic Hayes River ignimbrite, erupted from Hayes volcano, contains dense porphyry blocks that match pumices in composition and phenocryst content and are samples of a shallow intrusion. Autocrystic monazite accommodated up to several weight % Th and significantly affected the U-Th ratio of the magma during differentiation. An isochron for early melt and low-U monazites yields an age of ~67 ka, whereas one for late melt and high-U monazites yields ~42 ka. This younger age is indistinguishable from the laser single crystal Ar-Ar age for sanidine of 41±2 ka (1 sigma). We interpret the apparent ~25 k.y. crystallization interval to represent the assembly and differentiation timescale associated with the Hayes magma body. Sharp reverse zoning in sanidine from pumice (but not porphyry) records a thermal pulse not seen in the more slowly reacting phases, suggesting that a rejuvenation event occurred just prior to eruption.

  14. Petrology and Geochemistry of Hydrothermally Altered Volcanic Rocks in the Iheya North Hydrothermal Field, Middle Okinawa Trough (United States)

    Yamasaki, T.


    The Iheya North hydrothermal field is located in the middle Okinawa Trough, a young and actively spreading back-arc basin extending behind the Ryukyu arc-trench system in the southeastern margin of the East China Sea. In this hydrothermal field, two scientific drilling expeditions (IODP Exp 331 and SIP CK14-04) were conducted using a deep-sea drilling vessel "Chikyu," and samples from a total of 27 holes were taken. Through these expeditions, Kuroko-type volcanogenic massive sulfide deposits (VMS), hydrothermally altered volcanic rocks, and pumiceous and pelagic sediments were recovered. The recovered core provided important information about the relationship between hydrothermal activity, alteration, and ore mineralization. Whole-rock major element composition and trace element (TE) patterns of pumices were very similar to those of rhyolites in the middle Okinawa Trough (RMO). However, pumices were relatively enriched in chalcophile elements Sr and Nb, which suggest incipient mineralization. Volcanic rock generally demonstrated strong silicification and was greenish pale gray in color. Regardless of severe alteration, some rock displayed major element composition broadly similar to the RMO. Alteration was evidenced by an increase in the content of SiO2 and MgO, and decrease in Al2O3, Na2O, and K2O content. The most striking geochemical feature of altered volcanic rock was the discordance between texture and the degree of modification of TEs. Some samples showed decussate texture occupied by petal-like quartz with severe silicification, but no prominent disturbance of concentration and patterns of TEs were observed. In contrast, samples with well-preserved igneous porphyritic texture showed very low TE content and modification of TE patterns. These results suggest that the modification of texture and composition of TEs, as well as silicification, do not occur by a uniform process, but several processes. This may reflect the differences in temperature and the

  15. Degassing history of a mid-ocean ridge rhyolite dome on the Alarcon Rise, Gulf of California (United States)

    Portner, R. A.; Dreyer, B. M.; Clague, D. A.; Lowenstern, J. B.; Head, J. W., III; Saal, A. E.


    A 2350 meter deep rhyolite lava dome and surrounding intermediate-mafic complex on the Alarcon Rise mid-ocean ridge in the Gulf of California was sampled extensively during a 2012 MBARI expedition. The dome is predominantly composed of sparsely vesicular (obsidian with local deposits of pumiceous breccia. Pumiceous lapilli comprise highly vesicular (40-60%) fracture networks that separate non-vesicular obsidian "pseudoclasts". Textures and major element geochemistry suggest that both lithologies originated from the same magma that formed the majority of the dome. This is corroborated by comparable major element compositions (~75% SiO2) and near-equilibrium phenocryst assemblages including olivine (Fo10) and plagioclase (An17). Attenuated total reflectance (ATR) and transmission FTIR spectroscopy was used to measure H2O concentrations in olivine and plagioclase melt inclusions as well as host glasses (CO2 was below detection, <30 ppm). Rhyolite host glass contains 1.5-2.0 wt% H2O, similar to nearby andesite and dacite. These concentrations agree with saturation limits for H2O (1.7%) at the depth of Alarcon Rise, but are slightly less than what is predicted by fractional crystallization modeling. Melt inclusions from plagioclase and olivine in rhyolite contain a maximum of 3.5-4.5% H2O suggesting that up to 3.0% H2O exsolved into bubbles during a 3 km ascent. Hydrostatic pressures (23 MPa) at the eruptive vent would have permitted 53% vesiculation in agreement with petrographic observations. Although ~50% vesiculation and exsolved H2O contents of 3.0 wt% are less than the ideal threshold for magmatic fragmentation, the presence of highly vesicular ash particles representing fragmented pumiceous breccia argues otherwise. We posit that decoupled volatiles from a deeper magma body migrated through fracture networks to the surface causing mild explosivity.

  16. The 1982 eruptions of El Chichon volcano, Mexico (3): Physical properties of pyroclastic surges (United States)

    Sigurdsson, H.; Carey, S. N.; Fisher, R. V.


    Two major pyroclastic surges generated during the 4 April 1982 eruption of El Chichon devastated an area of 153 km2 with a quasi-radial distribution around the volcano. The hot surge clouds carbonized wood throughout their extent and were too hot to allow accretionary lapilli formation by vapor condensation. Field evidence indicates voidage fraction of 0.99 in the surge cloud with extensive entrainment of air. Thermal calculations indicate that heat content of pyroclasts can heat entrained air and maintain high temperatures in the surge cloud. The dominant bed form of the surge deposits are sand waves shaped in dune forms with vertical form index of 10 20, characterized by stoss-side erosion and lee-side deposition of 1 10 cm reversely graded laminae. A systematic decrease in maximum lithic diameter with distance from source is accompanied by decrease in wavelength and amplitude. Modal analysis indicates fractionation of glass and pumice from the surge cloud relative to crystals, resulting in loss of at least 10% 25% of the cloud mass due to winnowing out of fines during surge emplacement. Greatest fractionation from the -1.0 0.0-∅ grain sizes reflects relatively lower pumice particle density in this range and segregation in the formative stages of the surge cloud. Extensive pumice rounding indicates abrasion during bed-load transport. Flow of pyroclastic debris in the turbulent surge cloud was by combination of bed-load and suspended-load transport. The surges are viewed as expanding pyroclastic gravity flows, which entrain and mix with air during transport. The balance between sedimentation at the base of the surge cloud and expansion due to entrainment of air contributed to low cloud density and internal turbulence, which persisted to the distal edge of the surge zone.

  17. The 1631 eruption of Vesuvius (United States)

    Rolandi, G.; Barrella, A. M.; Borrelli, A.


    Contemporary accounts of the violent eruption of Vesuvius in 1631 are reviewed, and recorded events are correlated with resulting volcanic deposits. Field study of the deposits in the proximal area revealed the presence of tephra falls, pyroclastic flows and lava, with subordinate surge deposits. A total volume of 1.1 km 3 (0.55 km 3 DRE) of phono-tephritic to phonolitic magma was ejected during 24 hours. The different magma compositions correspond with a transition from a lower, white, aphyric, highly vesiculated pumice (layer 1) to an upper, gray, crystal-rich, poorly vesiculated pumice (layer 3), showing reverse grading. Isopach and isopleth maps of the tephra-falls have been constructed to determine changes in the eruptive style and temporal evolution of the eruption column which reached a maximum height of 16 to 28 km. The recorded column height variations show a change in the mass discharge rate (8.9 × 10 6 kg/s to 8.2 × 10 7 kg/s) and the occurrence of pyroclastic flows during the deposition of the weakly vesiculated, dense pumice of the upper part of layer 3. Pyroclastic flows are crystal-rich and show St. Vincent-type features. The explosive phase demolished the upper part of the pre-existing cone, and debris flows invaded the southern side of the volcano. In the afternoon of December 17, 1631 an outbreak of lava flow from a southern lateral fracture system occurred, and effusion of lava continued up to midnight of December 18. Intermittent steam blasts continued to the end of December, when the eruption ended and Mount Vesuvius entered a solfataric phase. The earthquakes that had marked both the pre-eruptive and eruptive phases, continued, however, well into March 1632.

  18. Ignimbrite Analyses of Batur Caldera, Bali, based on 14C Dating

    Directory of Open Access Journals (Sweden)

    Igan S. Sutawidjaja


    Full Text Available Batur Caldera, in the northeastern part of Bali Island, is an elliptical collapse structure 13.8 by 10 km in size and another circular composite collapse structure with a diameter of 7.5 km in its centre. Two stages of the collapse were interrupted by silicic andesite lavas and domes. The first collapse was initiated by the eruption of about 84 km3 of the dacitic "Ubud Ignimbrite", about 29,300 years B.P., which caused a steep-walled depression about 1 km deep. The second ignimbrite was erupted from a large crater about the present lake, and it  produced about 19 km3 of a similar voluminous dacitic ignimbrite, called the "Gunungkawi Ignimbrite" about 20,150 years B.P. This second eruption trig- gered a second collapse, which created the central circular caldera, and formed a basin structure. Both the Ubud and Gunungkawi Ignimbrites consist of a similar dacitic composition, white to red (the most abundant nearly 90 % and dark grey to black dacitic pumice clasts. The large clasts, up to 20 cm in diameter, are in the non-welded ignimbrite, particularly in the upper part of the Gunungkawi Ignimbrite. The intracaldera ignimbrite, called the "Batur Ignimbrite" about 5 km3  in volume is a densely welded ignimbrite and generally shows typical welded features. The ignimbrite comprises at least five different flow units, separated by thin (15 - 40 cm welded pumiceous airfall deposits, with flattened pumice clasts. Another large eruption occurred about 5,500 years B.P., producing around 0.09 km3  andesitic ignimbrite. This was initiated by phreatomagmatic eruptions, indicated by thick phreatomagmatic and surge deposits, underlying the ignimbrite. The caldera and its vicinity are partly filled, and variably mantled by later eruptive products of dacitic and andesitic phreatomagmatic and airfall deposits.  

  19. Pyroclastic flow hazard assessment at Somma-Vesuvius based on the geological record (United States)

    Gurioli, L.; Sulpizio, R.; Cioni, R.; Sbrana, A.; Santacroce, R.; Luperini, W.; Andronico, D.


    During the past 22 ka of activity at Somma-Vesuvius, catastrophic pyroclastic density currents (PDCs) have been generated repeatedly. Examples are those that destroyed the towns of Pompeii and Ercolano in AD 79, as well as Torre del Greco and several circum-Vesuvian villages in AD 1631. Using new field data and data available from the literature, we delineate the area impacted by PDCs at Somma-Vesuvius to improve the related hazard assessment. We mainly focus on the dispersal, thickness, and extent of the PDC deposits generated during seven plinian and sub-plinian eruptions, namely, the Pomici di Base, Greenish Pumice, Pomici di Mercato, Pomici di Avellino, Pompeii Pumice, AD 472 Pollena, and AD 1631 eruptions. We present maps of the total thickness of the PDC deposits for each eruption. Five out of seven eruptions dispersed PDCs radially, sometimes showing a preferred direction controlled by the position of the vent and the paleotopography. Only the PDCs from AD 1631 eruption were influenced by the presence of the Mt Somma caldera wall which stopped their advance in a northerly direction. Most PDC deposits are located downslope of the pronounced break-in slope that marks the base of the Somma-Vesuvius cone. PDCs from the Pomici di Avellino and Pompeii Pumice eruptions have the most dispersed deposits (extending more than 20 km from the inferred vent). These deposits are relatively thin, normally graded, and stratified. In contrast, thick, massive, lithic-rich deposits are only dispersed within 7 to 8 km of the vent. Isopach maps and the deposit features reveal that PDC dispersal was strongly controlled by the intensity of the eruption (in terms of magma discharge rate), the position of the vent area with respect to the Mt Somma caldera wall, and the pre-existing topography. Facies characteristics of the PDC deposits appear to correlate with dispersal; the stratified facies are consistently dispersed more widely than the massive facies.

  20. Mineral and chemical variations within an ash-flow sheet from Aso caldera, Southwestern Japan (United States)

    Lipman, P.W.


    Although products of individual volcanic eruptions, especially voluminous ash-flow eruptions, have been considered among the best available samples of natural magmas, detailed petrographic and chemical study indicates that bulk compositions of unaltered Pleistocene ash-flow tuffs from Aso caldera, Japan, deviate significantly from original magmatic compositions. The last major ash-flow sheet from Aso caldera is as much as 150 meters thick and shows a general vertical compositional change from phenocryst-poor rhyodacite upward into phenocryst-rich trachyandesite; this change apparently reflects in inverse order a compositionally zoned magma chamber in which more silicic magma overlay more mafic magma. Details of these magmatic variations were obscured, however, by: (1) mixing of compositionally distinct batches of magma during upwelling in the vent, as indicated by layering and other heterogeneities within single pumice lumps; (2) mixing of particulate fragments-pumice lumps, ash, and phenocrysts-of varied compositions during emplacement, with the result that separate pumice lenses from a single small outcrop may have a compositional range nearly as great as the bulk-rook variation of the entire sheet; (3) density sorting of phenocrysts and ash during eruption and emplacement, resulting in systematic modal variations with distance from the caldera; (4) addition of xenocrysts, resulting in significant contamination and modification of proportions of crystals in the tuffs; and (5) ground-water leaching of glassy fractions during hydration after cooling. Similar complexities characterize ash-flow tuffs under study in southwestern Nevada and in the San Juan Mountains, Colorado, and probably are widespread in other ash-flow fields as well. Caution and careful planning are required in study of the magmatic chemistry and phenocryst mineralogy of these rocks. ?? 1967 Springer-Verlag.

  1. Stratigraphy of Pyroclastic Deposits of EL Aguajito Caldera, Baja California Sur, MÉXICO (United States)

    Osorio Ocampo, L. S.; Macias, J. L.; García Sánchez, L.; Pola, A.; Saucedo, R.; Sánchez, J. M.; Avellán, D. R.; Cardona, S.; Reyes-Agustín, G.; Arce, J. L.


    El Aguajito caldera is located in the State of Baja California Sur, it comprises an area of 450 km2 and sits within the Santa Rosalía Basin which is controlled by NE-SW extensional structures and the NW-SE Cimarron Fault that transects the caldera structure. The oldest rocks are ~90 Ma granodiorites covered by an Oligocene-Miocene volcano-sedimentary sequence, the Miocene Santa Lucia Formation and La Esperanza basalt. Pliocene volcanism is represented by La Reforma caldera, El Aguajito caldera, and the Tres Vírgenes Volcanic complex. This study focuses on the cartography and stratigraphy of area in order to understand the evolution of the volcanic system. The stratigraphy from base to top consists of a series of shallow marine sediments (fossiliferous sandstones) covered by a thick sequence of ignimbrites and pyroclastic flows interbedded with volcaniclastic deposits (Gloria and El Infierno Formations). On top of these deposits is El Aguajito caldera, it consists of a 2 m thick pumice fallout followed by an ignimbrite with three transitional lithofacies: a ≤30-m thick light-pink pyroclastic flow enriched in pumice at the base that gradually becomes enrich in lithics towards the top with the occurrence of degasing pipes. On top rests a 15 m-thick light-purple ignimbrite slightly welded with fiammes and a sequence of pumiceous pyroclastic flows and fallouts. These deposits have been associate to the caldera formation with a collapse diameter of ~8 km marked by rhyolitic domes exposed along a ring collapse crowned the sequence as well as NW-SE aligned rhyolitic domes parallel to the seashore. This cartography allowed to present a preliminary new geological map with four stratigraphic units recognized so far, that were emplaced under subaerial conditions beginning with a Plinian column followed by the emplacement of El Aguajito ignimbrite with its subsequent caldera collapse and finally the extrusion of resurgent domes.

  2. Comenditic and pantelleritic ash-flow tuffs from Volcan Las Navajas, Nayarit, Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, S.A.; Hebre, J.A.


    Two distinctive ash-flow tuffs occur around the base of Volcan Las Navajas, a Pleistocene trachyte - peralkaline rhyolite center located in the northwestern segment of the Mexican Volcanic belt. The lower ash-flow unit is locally up to 65 m thick, is lithic rich and contains pumice blocks of comenditic rhyolite. The unit is not extensively exposed, and thus its areal extent and volume cannot be determined. Its chemical characteristics and stratigraphic relationship to other products erupted from Las Navajas suggest that it is related to the formation of the older of the two calderas which occur on Las Navajas. Unconformably overlying this unwelded ash-flow is a pantelleritic airfall pumice unit which is locally welded. This airfall unit is conformably overlain by a welded as-flow tuff that contains fiamme of pantelleritic composition (72 %SiO/sub 2/, 8% FeO*, 900 ppm Zr, agpaitic index of 1.7) as well as pumice blocks that show evidence of various degrees of mixing between pantellerite and trachyte. This suggests eruption from a chemically zoned magma chamber. This unit is locally up to 20 m thick, although its top has been removed by erosion. It is found on all sides of Las Navajas except on the south where it may be covered by Volcan Sanganguey, a Pleistocene to Recent calc-alkaline volcano. The welded ash-flow has been dated by K - Ar at 0.2+/-0.1 m.y. Stratigraphically and chemically this ash-flow appears to be related to the formation of younger of the two calderas.

  3. Degassing of Cl, F, Li and Be during extrusion and crystallization of the rhyolite dome at Volcán Chaitén, Chile during 2008 and 2009 (United States)

    Lowenstern, Jacob B.; Bleick, Heather; Vazquez, Jorge A.; Castro, Jonathan M.; Larson, Peter B.


    We investigated the distribution of Cl, F, Li, and Be in pumices, obsidians, and crystallized dome rocks at Chaitén volcano in 2008–2009 in order to explore the behavior of these elements during explosive and effusive volcanic activity. Electron and ion microprobe analyses of matrix and inclusion glasses from pumice, obsidian, and microlite-rich dome rock indicate that Cl and other elements were lost primarily during crystallization of the rhyolitic dome after it had approached the surface. Glass in pumice and microlite-free obsidian has 888 ± 121 ppm Cl, whereas residual glass in evolved microlite-rich dome rock generally retains less Cl (as low as 0.7 Mt Cl, with a potential maximum of 1.8 Mt for the entire 0.8-km3 dome. Elemental variations reflect an integrated bulk distribution ratio for Cl > 1.7 (1.7 times more Cl was degassed or incorporated into crystals than remained in the melt). Because Cl is lost dominantly as the very last H2O is degassed, and Cl is minimally (if at all) partitioned into microlites, the integrated vapor/melt distribution ratio for Cl exceeds 200 (200 times more Cl in the evolved vapor than in the melt). Cl is likely lost as HCl, which is readily partitioned into magmatic vapor at low pressure. Cl loss is accelerated by the change in the composition of the residual melt due to microlite growth. Cl loss also may be affected by open-system gas fluxing. Integrated vapor-melt distribution ratios for Li, F, and Be all exceed 1,000. On degassing, an unknown fraction of these volatiles could be immediately dissolved in rainwater.

  4. Effect of acupuncture on the pain perception thresholds of human teeth

    DEFF Research Database (Denmark)

    Bakke, Merete


    The effect of acumpuncture on the pain perception threshold of maxillary incisors and canines as determined by a Bofors Pulp Tester was studied in 33 dental students 19-30 years of age. Test teeth were cleaned with pumice and 10% alcohol, air-dried, and insulated at the approximal surfaces......), or S44 (foot). Compared with control threshold (8.44 muA) acupuncture was accompanied by a small increase, most pronounced after 45 min (1.51 muA, P less than 0.0005). However, the hypalgesia observed was insufficient to justify acupuncture as a means of pain control in conservative dentistry....

  5. 混合骨料混凝土抗冻性能试验研究%Experimental Study on Frost Resistance Properties of Mixed Aggregate Concrete

    Institute of Scientific and Technical Information of China (English)

    储建军; 霍俊芳


    通过混合骨料混凝土的快速冻融循环试验,研究了浮石替代率、聚丙烯纤维、冻融循环次数对混合骨料混凝土抗冻性能的影响.结果表明:相对动弹性模量随着浮石替代率增加而增加;对于一定范围浮石替代率的混凝土,聚丙烯纤维的掺入能够改善混凝土的抗冻性能,浮石替代率为30%,聚丙烯纤维掺量为0.9 kg/m3的混合骨料混凝土,质量损失最小;聚丙烯纤维的掺入能够抑制混合骨料混凝土的冻融损伤,提高混凝土的密实度,减小混合骨料混凝土相对动弹性模量的损失.%Through the fast freeze-thaw cycle tests of mixed aggregate concrete, the effect of pumice replacement rate, polypropylene fibers and freeze-thaw cycle time on the frost resistance properties of mixed aggregate concrete was investigated. The results show that the relative dynamic elastic modulus increase with the increase of the pumice replacement rate, and the introduction of the polypropylene fibers could improve the frost resistance of the concrete to a certain scope of the pumice replacement rate. As for this experiment, when concrete was mixed with the pumice replacement rate of 30% and the polypropylene fibers of 0. 9 kg/m3, quality loss rate was the smallest. The addition of the polypropylene fibers could refrain from the concrete freeze-thaw damage, improve the density of the concrete and reduce the relative dynamic elastic modulus loss of the concrete.

  6. 古淀江潟の予察的検討


    中村, 唯史; 徳岡, 隆夫; 赤坂, 正秀


    A glassy fine volcanic ash layer and a diatomite bed were discovered to intercalate in the Holocene sediments from several boring cores in the Yodoe Plain,Tottori Prefecture.The volcanic ash layer,about 0.2cm thick,intercalates in organic mudstone.It is rich in bubble-type volcanic glasses,containing subordinate pumice-type volcanic glasses and rare phenocrysts of hyperthene and augite.The glasses are mostly brown in color.On the basis of EPMA analysis,these are safely idetified to the Akahoy...

  7. Impact of the AD 79 explosive eruption on Pompeii, II. Causes of death of the inhabitants inferred by stratigraphic analysis and areal distribution of the human casualties (United States)

    Luongo, Giuseppe; Perrotta, Annamaria; Scarpati, Claudio; De Carolis, Ernesto; Patricelli, Giovanni; Ciarallo, Annamaria


    Detailed descriptions of the effects of explosive eruptions on urban settlements available to volcanologists are relatively rare. Apart from disease and starvation, the largest number of human deaths caused by explosive eruptions in the twentieth century are due to pyroclastic flows. The relationship between the number of victims related to a specific hazard and the presence of urban settlements in the area covered by the eruption has been shown. However, pyroclastic falls are also extremely dangerous under certain conditions. These conclusions are based on archaeological and volcanological studies carried out on the victims of the well-known AD 79 eruption of Vesuvius that destroyed and buried the Roman city of Pompeii. The stratigraphic level in the pyroclastic deposit and the location of all the casualties found are described and discussed. The total number of victims recovered during the archaeological excavations amounts to 1150. Of these, 1044 well recognisable bodies plus an additional group of 100 individuals were identified based on the analysis of several groups of scattered bones. Of the former, 394 were found in the lower pumice lapilli fall deposit and 650 in the upper stratified ash and pumice lapilli pyroclastic density currents (PDCs) deposits. In addition, a tentative evaluation suggests that 464 corpses may still be buried in the unexcavated part of the city. According to the reconstruction presented in this paper, during the first phase of the eruption (August 24, AD 79) a huge quantity of pumice lapilli fell on Pompeii burying the city under 3 m of pyroclastic material. During this eruptive phase, most of the inhabitants managed to leave the city. However, 38% of the known victims were killed during this phase mainly as a consequence of roofs and walls collapsing under the increasing weight of the pumice lapilli deposit. During the second phase of the eruption (August 25, AD 79) 49% of the total victims were on the roadways and 51% inside

  8. Composition and diagenetic processes of sandstone and tuff deposits of the Cenomanian Cardiel Formation, Cardiel Lake area, province of Santa Cruz

    Directory of Open Access Journals (Sweden)

    R.R. Andreis


    Full Text Available The Cardiel Formation (Cenomanian, around 200 m in thickness in the studied area, includes different types of volcaniclastic deposits, mainly represented by fine tuffs and massive bentonites, and subordinated epiclastics such as lithic sandstones of yellowish-brown, dusky yellow, or light olive hues, siltstones and claystones. Reddened paleosols with some small axial roots and weak prismatic structures appear on top of siltstones, tuffs and bentonites. Tufites and tuffs contain the same neovolcanic components, abundant glass shards and minor pumices. Different types of glass shards can be differentiated whitin this unit, whereas pumice fragments are represented by different vesicular varieties. Vitreous tuffaceous clasts are abundant in the tufites. Almost all samples contain not only diagenetically-derived, but also pedogenetically-infiltrated montmorillonite, as well as zeolites. Predominant Ca-Na-K clinoptilolite (Si/Al>4 and minor analcime (Si/Al near 3 were identified. Smectite and clinoptilolite may either replace glass-shards or pumices, or fill pore spaces, whereas smectite also appears as thin cutans. The sequence of diagenetic processes includes the conversion (hydrolysis of glass to smectite, and later to zeolites. Furthermore, zeolites preceded calcite growth (sometimes replacing glass-shards or pumices, which in turn, formed prior to pervading ferric oxides-hydroxides. The vertical distribution of zeolites can be explained taking into account the presence of percolating waters in an open hydrologic system. The zeolite content throughout the whole profile links the mineralogical association observed within the sediments of the Cardiel Formation to the clinoptilolite zone. Paleoenvironmental reconstructions for the Cardiel Formation point out to tidal currents taking place in wide lagoons; tuffaceous and bentonitic deposits covered those ancient lagoons forming wide, flat plains on which paleosols developed. Paleocurrents measured on

  9. 40Ar/39Ar ages of the AD 79 eruption of Vesuvius, Italy (United States)

    Lanphere, Marvin; Champion, Duane; Melluso, Leone; Morra, Vincenzo; Perrotta, Annamaria; Scarpati, Claudio; Tedesco, Dario; Calvert, Andrew


    The Italian volcano, Vesuvius, erupted explosively in AD 79. Sanidine from pumice collected at Casti Amanti in Pompeii and Villa Poppea in Oplontis yielded a weighted-mean 40Ar/39Ar age of 1925±66 years in 2004 (1σ uncertainty) from incremental-heating experiments of eight aliquants of sanidine. This is the calendar age of the eruption. Our results together with the work of Renne et al. (1997) and Renne and Min (1998) demonstrate the validity of the 40Ar/39Ar method to reconstruct the recent eruptive history of young, active volcanoes.

  10. A documentation on burrows in hard substrates of ferromanganese crusts and associated soft sediments from the Central Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Banerjee, R.

    , the photographic records of recent bioturbation (Figure 4 a and b) on soft sediments were taken using a deep-towed camera. Extensive fossil burrows are seen in the cla ystone and altered pumice substrates of many ferromanganese en- crustations and nodules...). One of the associated organisms collected with these samples is Echinodermata (Figure 3 i). The diameter of the fossil burrows varies from 3 to 10 mm. Their length ranges between 1 and 10 cm in different substrates (Figure 3 a?g). Some burrows...

  11. Field-trip guide for exploring pyroclastic density current deposits from the May 18, 1980, eruption of Mount St. Helens, Washington (United States)

    Brand, Brittany D.; Pollock, Nicholas; Sarocchi, Damiano; Dufek, Josef; Clynne, Michael A.


    Pyroclastic density currents (PDCs) are one of the most dangerous phenomena associated with explosive volcanism. To help constrain damage potential, a combination of field studies, laboratory experiments, and numerical modeling are used to establish conditions that influence PDC dynamics and depositional processes, including runout distance. The objective of this field trip is to explore field relations that may constrain PDCs at the time of emplacement.The PDC deposits from the May 18, 1980, eruption of Mount St. Helens are well exposed along the steep flanks (10–30° slopes) and across the pumice plain (5–12° slopes) as far as 8 km north of the volcano. The pumice plain deposits represent deposition from a series of concentrated PDCs and are primarily thick (3–12 m), massive, and poorly sorted. In contrast, the steep east-flank deposits are stratified to cross-stratified, suggesting deposition from PDCs where turbulence strongly influenced transport and depositional processes.The PDCs that descended the west flank were largely nondepositional; they maintained a higher flow energy and carrying capacity than PDCs funneled through the main breach, as evidenced by the higher concentration of large blocks in their deposits. The PDC from the west flank collided with PDCs funneled through the breach at various points along the pumice plain. Evidence for flow collision will be explored and debated throughout the field trip.Evidence for substrate erosion and entrainment is found (1) along the steep eastern flank of the volcano, which has a higher degree of rough, irregular topography relative to the west flanks where PDCs were likely nonerosive, (2) where PDCs encountered debris-avalanche hummocks across the pumice plain, and (3) where PDCs eroded and entrained material deposited by PDCs produced during earlier phases of the eruption. Two features interpreted as large-scale (tens of meters wide) levees and a large (~200 m wide) channel scour-and-fill feature

  12. A microcosmos study on the effects of Cd-containing wood ash on the coniferous humus fungal community and the Cd bioavailability

    Energy Technology Data Exchange (ETDEWEB)

    Fritze, H.; Perkioemaeki, J.; Pennanen, T. [Finnish Forest Research Inst., Vantaa (Finland); Petaenen, T.; Romantschuk, M.; Yrjaelae, K. [Dept. of Biosciences, Div. of General Microbiology, 56 (Biocenter 1 C), Univ. of Helsinki (Finland); Karp, M. [Dept. of Biotechnology, Univ. of Turku, Turku (Finland)


    Background and Aims. The use of wood ash in forestry has been questioned because the cadmium (Cd) concentration of ash, which varies between 1 and 20 mg kg{sup -1} ash, exceeds the level allowed for fertilizers (3 mg kg{sup -1}) used in agriculture. To investigate the effects of Cd and ash on the fungal community composition and Cd bioavailability of the humus layer of boreal, coniferous forests, pumice or wood ash, spiked with a water soluble (CdCl{sub 2}) or insoluble (CdO) form of Cd at three levels (0, 400 and 1000 mg kg{sup -1}), were applied at a fertilization level of 5000 kg ha{sup -1} in a laboratory microcosm study. Methods. After 2 months, the humus in the microcosms was sampled and extracted for total DNA to detect changes in the fungal community by using polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) techniques. PCR was performed using the fungal 18S rDNA primers FR1 + FF390 and FR1 + NS1. The bioavailability of Cd was measured with a bacterial biosensor (Bacillus subtilis BR 151/pT0024) emitting light in the presence of Cd. Results. Using the primer pairs FR1 + FF390 and FR1 + NS1, resulted in over 35 and 15 DGGE bands, respectively. Both primer pairs detected an ash, but no Cd effect. When using FR1 + FF390, a higher fluorescence was observed in one DGGE band of all ashed samples compared to the pumiced samples. With the primer pair FR1 + NS1, the ashed samples had a DGGE band which was not visible or only faintly visible in the pumiced samples. In addition, one DGGE band disappeared from the ashed samples. Humus layer water extracts showed that the Cd added with the pumice was in a bioavailable form. The luminescence intensity of the biosensor was dependent on the form and level of the Cd added. No luminescence was detected when the Cd was added with the ash. Conclusions. Ash fertilization altered the humus layer fungal community, whereas the level and form of additional Cd in the ash had no influence because it

  13. 桜島大正II二次溶岩流の形成プロセス


    横尾,亮彦 / 谷口,宏充; ヨコオ,リョウスケ / タニグチ,ヒロミツ; YOKOO,Ryosuke / TANIGUCHI,Hiromitsu


    In January 1914, a large eruption occurred at Sakurajima volcano with large quantities of pumice release, and the issues of lava flow followed it. The issues of lava flow can be divided into two stages; the first stage lava flow and the second stage. The volcanic activity was thought to be over by the summer of 1914, however, in the next spring, a new lava flow was found to issue from the end of second stage lava flow. Fukuyama (1978) called this new lava flow as "secondary lava flow" and dis...

  14. Rhyolitic calderas and centers clustered within the active andesitic belt of Ecuador's Eastern Cordillera

    Energy Technology Data Exchange (ETDEWEB)

    Mothes, Patricia A; Hall, Minard L [Instituto Geofisico, Escuela Politecnica Nacional, Quito (Ecuador)], E-mail:


    In the Ecuadorian volcanic arc a cluster of scattered rhyolitic and dacitic centers within the mainly andesitic Eastern Cordillera includes large caldera structures (Chalupas, Chacana, Cosanga) as well as smaller edifices, built upon the Paleozoic-Mesozoic metamorphic basement. At the Chacana caldera magmatism dates from 2.7 Ma to historic times. These centers erupted enormous ash flows and thick pumice lapilli falls that covered the InterAndean Valley near Quito. The role of the 50-70 km-thick crust with a notable negative gravity anomaly appears to be related to the generation of this highly silicic magmatism occurring along the crest of the Andes in the NVZ.

  15. Occurrence of volcanic ash in the Quaternary alluvial deposits, lower Narmada basin, western India

    Indian Academy of Sciences (India)

    Rachna Raj


    This communication reports the occurrence of an ash layer intercalated within the late Quaternary alluvial succession of the Madhumati River, a tributary of the lower Narmada River. Petrographic, morphological and chemical details of glass shards and pumice fragments have formed the basis of this study. The ash has been correlated with the Youngest Toba Tuff. The finding of ash layer interbedded in Quaternary alluvial sequences of western Indian continental margin is significant, as ash being datable material, a near precise time-controlled stratigraphy can be interpreted for the Quaternary sediments of western India. The distant volcanic source of this ash requires a fresh re-assessment of ash volume and palaeoclimatic interpretations.

  16. The Amazcala caldera, Queretaro, Mexico. Geology and geochronology (United States)

    Aguirre-Díaz, Gerardo J.; López-Martínez, Margarita


    The Amazcala caldera is located 30 km NE of Querétaro City, near Amazcala, state of Querétaro. This caldera is the northernmost caldera within the central sector of the Mexican Volcanic Belt (MVB). It has a 11×14 km 2 elliptical shape, and was formed 7.3-6.6 Ma ago. All caldera products are rhyolites. The oldest caldera unit, the Ezequiel Montes pumice (EMP), is a widespread pumice fallout emplaced around 7.3 Ma ago. An isopach map of the EMP shows two dispersal axes, oriented to the SW and SE with respect to the caldera. The EMP is 5 m thick 40 km to the SW and 35 km to the SE of the caldera. An isopleth map of the EMP shows that pumice fragments increase in size toward the caldera, from 1 cm at 40 km to 25 cm near the caldera rim. The EMP is a regional stratigraphic marker. The Colón ignimbrite, dated at 7.3±0.5 Ma, is stratigraphically above the EMP. It consists of several ash-flow units interbedded with minor pumice fall lapilli and ash, with a minimum thickness of about 80 m at Colón. The caldera rim is occupied by several rhyolite lava domes and flows, some of which extend 10 km from the rim. These domes contain parts of fresh, aphyric obsidian. The last caldera event is an intracaldera rhyolitic dome near the NE rim at about 6.6 Ma. The dome is 4×2 km 2 and is elongated in the NE direction. The Amazcala caldera is 480 km from the Middle America Trench and represents the farthest inland caldera in the central sector of the MVB. Its age of 7.3-6.6 Ma indicates that it is the oldest caldera of the MVB so far reported. This confirms the general view that the volcanic activity of the MVB initiated at its northern margin, and then migrated southward in time.

  17. Late Holocene stratigraphy of the Tetimpa archaeological sites, northeast flank of Popocatepetl volcano, central Mexico (United States)

    Panfil, M.S.; Gardner, T.W.; Hirth, K.G.


    Late Holocene (240 km2 on the east side of the volcano with >25 cm of tephra. Lavas from eruptive sequence I dammed drainage in the lowland area near the town of San Nicolas and caused local upstream deposition of as much as 30 m of lacustrine silts, clays, and sands. These lacustrine deposits record an eruptive hiatus for the Tetimpa area of about 750 14C yr: between ca. 2100 and ca. 1350 yr B.P., no major tephras were deposited in the Tetimpa area. In upland areas, this time period is represented by an unconformity and by Entisols formed in the top of pumice deposits and lavas from eruptive sequence I. Artifacts, agricultural furrows, and dwellings record human reoccupation of this surface. At the end of this hiatus, several lahars were deposited above the lacustrine sequence and locally above the Entisol in upland positions adjacent to streams. Between ca. 1350 and ca. 1200 yr B.P., tephras from eruptive sequence II buried these paleosols, occupation sites, lacustrine sediments, and lahars. Andesitic (~62% SiO2) pumice lapilli deposits in the Tetimpa area record three pumice-fall eruptions directed northeast and east of the crater. The first and smallest of these (maximum Tetimpa area thickness = 12 cm; >52 km2 covered by >25 cm) took place at ca. 1350 yr B.P. and was accompanied by pyroclastic surge events preserved in the Tetimpa area by charcoal, sand waves, and cross-stratified sand-sized tephra. At ca. 1200 yr B.P., the products of two Plinian-style events and additional pyroclastic surges reached the Tetimpa area. The largest of these tephra-fall events covered the Tetimpa area with 0.5-1 m of tephra and blanketed an area of >230 km2 with a thickness of >25 cm. The Tetimpa record confirms two of the four periods of explosive volcanism recognized by studies conducted around Popocatepetl in the past 30 yr. Eruptive sequence I corresponds to the explosive period between 2100 and 2500 yr B.P., and eruptive sequence II corresponds to the period between 900 and

  18. Interplinian explosive activity of Santorini volcano (Greece) during the past 150,000 years (United States)

    Vespa, M.; Keller, J.; Gertisser, R.


    The eruptive history of Santorini was dominated by twelve major Plinian eruptions. Six of these (Middle Pumice, Vourvoulos, Upper Scoriae 1, Upper Scoriae 2, Cape Riva and Minoan) occurred during the past ˜150 ky. This study focuses on the stratigraphy and geochemistry of the interplinian pyroclastic deposits between 145 ka (Middle Pumice) and 3.6 ka (Minoan). Five interplinian eruptive intervals were identified between these major eruptions and are numbered M8-M12. The Upper Scoriae 1/Upper Scoriae 2 (M10) and Upper Scoriae 2/Cape Riva (M11) intervals are divided into sub-intervals by voluminous interplinian lava formations, the Skaros and Andesites of Oia and Therasia lavas, respectively. Each interval lasted between ˜17 and ˜45 ky and contains pyroclastic deposits of numerous eruptions indicating considerable volcanic activity between the major Plinian events. Most of these interplinian eruptions produced scoria-fall and ash-fall deposits predominantly from subplinian-type eruptions. Surge deposits, resulting from phreatomagmatic activity, are predominant in the Upper Scoriae 1/Skaros sub-interval (M10a). The Andesites of Oia/Cape Riva sub-interval (M11b) is entirely composed of subplinian pumice-fall and ash deposits. Other subplinian pumice-fall deposits occur in the intervals Vourvoulos/Upper Scoriae 1 (M9) and Upper Scoriae 1/Upper Scoriae 2 (M10). The Upper Scoriae 1/Skaros sub-interval (M10a) belongs to one of the longest interplinian intervals (M10) that is characterized by the thickest eruptive units and the largest number of eruptions. A further prominent interplinian pyroclastic formation in northern Thera is the Megalo Vouno cinder cone deposit, which occurred in a time span between the Vourvoulos eruption and the formation of the Skaros lava shield. The interplinian deposits vary from 50 to 70 wt.% SiO 2 and are classified as basalt, basaltic andesite, andesite and dacite with a typical calc-alkaline affinity in accordance with the general

  19. Floating stones off El Hierro, Canary Islands: xenoliths of pre-island sedimentary origin in the early products of the October 2011 eruption

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    V. R. Troll


    Full Text Available A submarine eruption started off the south coast of El Hierro, Canary Islands, on 10 October 2011 and continues at the time of this writing (February 2012. In the first days of the event, peculiar eruption products were found floating on the sea surface, drifting for long distances from the eruption site. These specimens, which have in the meantime been termed "restingolites" (after the close-by village of La Restinga, appeared as black volcanic "bombs" that exhibit cores of white and porous pumice-like material. Since their brief appearance, the nature and origin of these "floating stones" has been vigorously debated among researchers, with important implications for the interpretation of the hazard potential of the ongoing eruption. The "restingolites" have been proposed to be either (i juvenile high-silica magma (e.g. rhyolite, (ii remelted magmatic material (trachyte, (iii altered volcanic rock, or (iv reheated hyaloclastites or zeolite from the submarine slopes of El Hierro. Here, we provide evidence that supports yet a different conclusion. We have analysed the textures and compositions of representative "restingolites" and compared the results to previous work on similar rocks found in the Canary Islands. Based on their high-silica content, the lack of igneous trace element signatures, the presence of remnant quartz crystals, jasper fragments and carbonate as well as wollastonite (derived from thermal overprint of carbonate and their relatively high oxygen isotope values, we conclude that "restingolites" are in fact xenoliths from pre-island sedimentary layers that were picked up and heated by the ascending magma, causing them to partially melt and vesiculate. As they are closely resembling pumice in appearance, but are xenolithic in origin, we refer to these rocks as "xeno-pumice". The El Hierro xeno-pumices hence represent messengers from depth that help us to understand the interaction between ascending magma and crustal lithologies

  20. Long term storage of explosively erupted magma at Nevado de Toluca volcano, Mexico (United States)

    Arce, J. L.; Gardner, J.; Macias, J. L.


    Dacitic magmas production is common in subduction-related volcanoes, occurring in those with a long period of activity as a result of the magmatic evolution. However, in this evolution many factors (i.e. crystal fractionation, assimilation, magma mixing) can interact to produce dacites. Nevado de Toluca volcano (4,680 masl; 19°09'N; 99°45'W) Central Mexico has recorded a long period of time producing dacites explosively, at least during 42 ka of activity, involving several km3 of magma, with two important Plinian-type eruptions occurred at ~21.7 ka (Lower Toluca Pumice) and ~10.5 ka (Upper Toluca Pumice). Questions like, what was the mechanism responsible to produce voluminous dacitic magma and how the volatiles and pressure changed in the Nevado de Toluca system, remain without answers. Dacites from the Lower Toluca Pumice (LTP) contain plagioclase, amphibole, iron-titanium oxides, and minor resorbed biotite, set in a glassy-vesicular matrix and the Upper Toluca Pumice (UTP) dacites contain the same mineral phases plus orthopyroxene. Ilmenite- ulvospinel geothermometry yielded a temperature of ~860°C for the LTP dacite, a little hotter than the UTP (~ 840°C). Based on hydrothermal experiments data, amphibole is stable above 100 MPa under 900°C, while plagioclase crystallizes up to 250-100 MPa at temperatures of 850-900°C. Pyroxene occurs only at pressures of 200-100 MPa with its respective temperatures of 825-900°C. Water contents in the LTP magma (2-3.5 wt %) are similar to that calculated for the UTP magma (1.3-3.6 wt %). So, there are only small changes in temperature and pressure from ~21.7 ka to 10.5 ka. It is noteworthy that orthopyroxene is absent in the LTP, however reaction-rimmed biotite (probably xenocrystic) is commonly observed in all dacites. Hence, almost all dacitic magmas seem to be stored at relatively similar pressures, water contents, and temperatures. All of these data could suggest repetitive basic magma injections producing the

  1. New insights into the initiation and venting of the Bronze-Age eruption of Santorini (Greece), from component analysis (United States)

    Druitt, T. H.


    The late-seventeenth century BC Minoan eruption of Santorini discharged 30-60 km3 of magma, and caldera collapse deepened and widened the existing 22 ka caldera. A study of juvenile, cognate, and accidental components in the eruption products provides new constraints on vent development during the five eruptive phases, and on the processes that initiated the eruption. The eruption began with subplinian (phase 0) and plinian (phase 1) phases from a vent on a NE-SW fault line that bisects the volcanic field. During phase 1, the magma fragmentation level dropped from the surface to the level of subvolcanic basement and magmatic intrusions. The fragmentation level shallowed again, and the vent migrated northwards (during phase 2) into the flooded 22 ka caldera. The eruption then became strongly phreatomagmatic and discharged low-temperature ignimbrite containing abundant fragments of post-22 ka, pre-Minoan intracaldera lavas (phase 3). Phase 4 discharged hot, fluidized pyroclastic flows from subaerial vents and constructed three main ignimbrite fans (northwestern, eastern, and southern) around the volcano. The first phase-4 flows were discharged from a vent, or vents, in the northern half of the volcanic field, and laid down lithic-block-rich ignimbrite and lag breccias across much of the NW fan. About a tenth of the lithic debris in these flows was subvolcanic basement. New subaerial vents then opened up, probably across much of the volcanic field, and finer-grained ignimbrite was discharged to form the E and S fans. If major caldera collapse took place during the eruption, it probably occurred during phase 4. Three juvenile components were discharged during the eruption—a volumetrically dominant rhyodacitic pumice and two andesitic components: microphenocryst-rich andesitic pumices and quenched andesitic enclaves. The microphenocryst-rich pumices form a textural, mineralogical, chemical, and thermal continuum with co-erupted hornblende diorite nodules, and together

  2. Volcanic activity in the Acambay Graben: a < 25 Ka subplinian eruption from the Temascalcingo volcano and implications for volcanic hazard. (United States)

    Pedrazzi, Dario; Aguirre Díaz, Gerardo; Sunyé Puchol, Ivan; Bartolini, Stefania; Geyer, Adelina


    The Trans-Mexican Volcanic Belt (TMVB) contains a large number of stratovolcanoes, some well-known, as Popocatepetl, Iztaccihuatl, Nevado de Toluca, or Colima and many others of more modest dimensions that are not well known but constitute the majority in the TMVB. Such volcanoes are, for example, Tequila, San Juan, Sangangüey, Cerro Culiacán, Cerro Grande, El Zamorano, La Joya, Palo Huerfano, Jocotitlán, Altamirano and Temascalcingo, among many others. The Temascalcingo volcano (TV) is an andesitic-dacitic stratovolcano located in the Trans-Mexican Volcanic Belt (TMVB) at the eastern part of the Acambay Graben (northwest portion of Estado de México). The TV is composed mainly by dacitic, porphyritic lavas, block and ash deposits and subordinate pumice fall deposits and ignimbrites (Roldán-Quintana et al., 2011). The volcanic structure includes a summit caldera that has a rectangular shape, 2.5×3.5 km, with the largest side oriented E-W, parallel to major normal faults affecting the edifice. The San Mateo Pumice eruption is one of the greatest paroxysmal episodes of this volcano with pumice deposits mainly exposed at the scarp of the Acambay-Tixmadeje fault and at the northern and northeastern flanks of TV. It overlies a paleosol dated at 25 Ka. A NE-trending dispersion was obtained from field data covering an area of at least 80 km2. These deposits overlie older lava flows and mud flows and are discontinuously covered and eroded by younger reworked deposits of Temascalcingo volcano. This event represents a highly explosive phase that generated a relatively thick and widespread pumice fallout deposit that may occur again in future eruptions. A similar eruption today would have a significantly impact in the region, overall due to the fact that there has been no systematic assessment of the volcanic hazard in any of the studies that have been conducted so far in the area. So, this is a pending and urgent subject that must be tackled without delay. Financed by

  3. Prediction of Heavy Metal Removal by Different Liner Materials from Landfill Leachate: Modeling of Experimental Results Using Artificial Intelligence Technique (United States)

    Turan, Nurdan Gamze; Gümüşel, Emine Beril; Ozgonenel, Okan


    An intensive study has been made to see the performance of the different liner materials with bentonite on the removal efficiency of Cu(II) and Zn(II) from industrial leachate. An artificial neural network (ANN) was used to display the significant levels of the analyzed liner materials on the removal efficiency. The statistical analysis proves that the effect of natural zeolite was significant by a cubic spline model with a 99.93% removal efficiency. Optimization of liner materials was achieved by minimizing bentonite mixtures, which were costly, and maximizing Cu(II) and Zn(II) removal efficiency. The removal efficiencies were calculated as 45.07% and 48.19% for Cu(II) and Zn(II), respectively, when only bentonite was used as liner material. However, 60% of natural zeolite with 40% of bentonite combination was found to be the best for Cu(II) removal (95%), and 80% of vermiculite and pumice with 20% of bentonite combination was found to be the best for Zn(II) removal (61.24% and 65.09%). Similarly, 60% of natural zeolite with 40% of bentonite combination was found to be the best for Zn(II) removal (89.19%), and 80% of vermiculite and pumice with 20% of bentonite combination was found to be the best for Zn(II) removal (82.76% and 74.89%). PMID:23844384

  4. Surface morphology changes of acrylic resins during finishing and polishing phases

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    Glaucio Serra


    Full Text Available INTRODUCTION: The finishing and polishing phases are essential to improve smoothness and shining on the surface of acrylic resins used to make removable orthodontic appliances. A good surface finishing reduces roughness, which facilitates hygiene, prevents staining and provides greater comfort to the patients. OBJECTIVE: The aim of this paper was to analyze the changes on surface morphology of acrylic resins during finishing and polishing phases. METHODS: Thirty discs (10 mm in diameter and 5 mm in length were made with acrylic resin and randomly divided into ten groups. The control group did not receive any treatment while the other groups received gradual finishing and polishing. The last group received the entire finishing and polishing procedures. Surface morphology was qualitatively analyzed through scanning electron microscopy and quantitatively analyzed through a laser profilometer test. RESULTS: The acrylic resin surfaces without treatment showed bubbles which were not observed in the subsequent phases. Wearing out with multilaminated burs, finishing with wood sandpaper and finishing with water sandpaper resulted in surfaces with decreasing irregularities. The surfaces that were polished with pumice and with low abrasive liquids showed high superficial smoothness. CONCLUSION: Highly smooth acrylic resin surfaces can be obtained after mechanical finishing and polishing performed with multilaminated burs, wood sandpaper, water sandpaper, pumice and low abrasive liquids.

  5. Tephra dispersal during the Campanian Ignimbrite (Italy) eruption: implications for ultra-distal ash transport during the large caldera-forming eruption (United States)

    Smith, Victoria C.; Isaia, Roberto; Engwell, Sam L.; Albert, Paul. G.


    The Campanian Ignimbrite eruption dispersed ash over much of the central eastern Mediterranean Sea and eastern Europe. The eruption started with a Plinian phase that was followed by a series of pyroclastic density currents (PDCs) associated with the collapse of the Plinian column and the caldera. The glass compositions of the deposits span a wide geochemical range, but the Plinian fallout and PDCs associated with column collapse, the Lower Pumice Flow, only erupted the most evolved compositions. The later PDCs, the Breccia Museo and Upper Pumice Flow, erupted during and after caldera collapse, tap a less evolved component, and intermediate compositions that represent mixing between the end-members. The range of glass compositions in the Campanian Ignimbrite deposits from sites across the central and eastern Mediterranean Sea allow us to trace the dispersal of the different phases of this caldera-forming eruption. We map the fallout from the Plinian column and the plumes of fine material associated with the PDCs (co-PDCs) across the entire dispersal area. This cannot be done using the usual grain-size methods as deposits in these distal regions do not retain characteristics that allow attribution to either the Plinian or co-PDC phases. The glass compositions of the tephra at ultra-distal sites (>1500 km from the vent) match those of the uppermost PDC units, suggesting that most of the ultra-distal dispersal was associated with the late co-PDC plume that was generated during caldera collapse.

  6. LA-ICP-MS Pb-U Dating of Young Zircons from the Kos-Nisyros Volcanic Centre, SE Aegean Arc (Greece) (United States)

    Guillong, M.; Von Quadt, A.; Peytcheva, I.; Bachmann, O.


    Zircon Pb-U dating has become a key technique for answering many important questions in geosciences. This paper describes a new LA-ICP-MS approach. We show, using previously dated samples of a large quaternary rhyolitic eruption in the Kos-Nisyros volcanic centre (the 161 ka Kos Plateau Tuff), that the precision of our LA-ICP-MS method is as good as via SHRIMP, while ID-TIMS measurements confirm the accuracy. Gradational age distribution over >140 ka of the Kos zircons and the near-absence of inherited cores indicate near-continuous crystallisation in a growing magma reservoir with little input from wall rocks. Previously undated silicic eruptions from Nisyros volcano (Lower Pumice, Nikia Flow, Upper Pumice), which are stratigraphically constrained to have happened after the Kos Plateau Tuff, are dated to be younger than respectively 124 ± 35 ka, 111 ± 42 ka and 70 ± 24 ka. Samples younger than 1 Ma were corrected for initial thorium disequilibrium using a new formula that also accounts for disequilibrium in 230Th decay. Guillong, M. et al., 2014, JAAS, 29, p. 963-967; doi: 10.1039/c4ja00009a.

  7. Secular variation study from non-welded pyroclastic deposits from Montagne Pelée volcano, Martinique (West Indies) (United States)

    Genevey, A.; Gallet, Y.; Boudon, G.


    We present palaeomagnetic data obtained from large clasts collected in non-welded pyroclastic deposits from Montagne Pelée volcano (Martinique Island, West Indies). These deposits, dated by the 14C method from 5000 yr BP to the present, comprise block- and ash-flows, ash- and pumice-flows and pumice fallouts. Alternating fields treatment was as a routine chosen to demagnetise large samples for which the magnetisation was measured with a specially designed inductometer. The mean directions obtained from block- and ash-flow deposits of the 1902 and 1929 eruptions are in good agreement with the expected geomagnetic directions at these times in Martinique. The so-called P1 eruption (˜1345 AD), which is characterised by a rarely observed transition from a Peléean to a Plinian eruptive style, allows a direct comparison of the palaeomagnetic directions obtained from the three types of pyroclastic deposits. All deposits provide identical mean directions, which further demonstrates the suitability of the non-welded pyroclastic deposits for geomagnetic secular variation study with a very good accuracy and precision. The possibility of using pyroclastic deposits is promising for obtaining a wider distribution of sampling sites, which may better allow us to constrain our knowledge on the geomagnetic secular variation. We find that large geomagnetic changes occurred in Martinique during the last millennium, while the variations appear more limited prior to this period.

  8. Caldera types and collapse styles (United States)

    Aguirre-Diaz, G. J.


    Three main types of collapse calderas can be defined, 1) summit caldera, 2) classic caldera, and 3) graben caldera. Summit calderas are those formed at the top of large volcanoes and are related to relatively small- volume pyroclastic products that include plinian fallouts and ignimbrites, such as Crater Lake, Las Cañadas, and Somma-Vesuvio. Classic calderas are semi-circular to irregular-shaped large structures, several km in diameter that are related to relatively large-volume pyroclastic products including pumice fallouts and widespread ignimbrites, such as Long-Valley, Campi Flegrei, and Los Humeros. Graben calderas are explosive volcano-tectonic collapse structures from which large-volume, ignimbrite-forming eruptions occurred through several vents along the graben walls and the intra-graben block faults causing the collapse of the graben or of a sector of the graben. The main products of graben calderas are surge-deposits and large-volume widespread ignimbrite sheets. Pumice fallouts are practically absent. Examples include the Sierra Madre Occidental in Mexico, La Pacana (Andes), Catalan Pyrenees, and perhaps Scafell (United Kingdom). Any of the three caldera types mentioned above could have collapsed at least in three different ways, 1) piston, when the collapse occurs as a single crustal block; 2) trap-door, when collapse occurs unevenly along one side while the opposite side remains with no collapse; 3) piece-meal, when collapse occurs as broken pieces of the crust on top of the magma chamber.

  9. Study on Soil Mobility of Two Neonicotinoid Insecticides

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    Mária Mörtl


    Full Text Available Movement of two neonicotinoid insecticide active ingredients, clothianidin (CLO and thiamethoxam (TMX, was investigated in different soil types (sand, clay, or loam and in pumice. Elution profiles were determined to explore differences in binding capacity. Soil characterized by high organic matter content retained the ingredients, whereas high clay content resulted in long release of compounds. Decrease in concentration was strongly influenced by soil types: both CLO and TMX were retained in loam and clay soils and showed ready elution through sandy soil and pumice. Elution capability of the active ingredients in sandy soil correlated with their water solubility, indicating approximately 30% higher rapidity for TMX than for CLO. Soil organic carbon-water partitioning coefficients (Koc determined were in good agreement with literature values with somewhat lower value for CLO in sandy soil and substantially higher values for TMX in clay soil. High mobility of these neonicotinoid active ingredients in given soil types urges stronger precautionary approach taken during their application.

  10. Evaluation of integrated anaerobic/aerobic fixed-bed sequencing batch biofilm reactor for decolorization and biodegradation of azo dye acid red 18: comparison of using two types of packing media. (United States)

    Hosseini Koupaie, E; Alavi Moghaddam, M R; Hashemi, S H


    Two integrated anaerobic/aerobic fixed-bed sequencing batch biofilm reactor (FB-SBBR) were operated to evaluate decolorization and biodegradation of azo dye Acid Red 18 (AR18). Volcanic pumice stones and a type of plastic media made of polyethylene were used as packing media in FB-SBBR1 and FB-SBBR2, respectively. Decolorization of AR18 in both reactors followed first-order kinetic with respect to dye concentration. More than 63.7% and 71.3% of anaerobically formed 1-naphthylamine-4-sulfonate (1N-4S), as one of the main sulfonated aromatic constituents of AR18 was removed during the aerobic reaction phase in FB-SBBR1 and FB-SBBR2, respectively. Based on statistical analysis, performance of FB-SBBR2 in terms of COD removal as well as biodegradation of 1N-4S was significantly higher than that of FB-SBBR1. Spherical and rod shaped bacteria were the dominant species of bacteria in the biofilm grown on the pumice stones surfaces, while, the biofilm grown on surfaces of the polyethylene media had a fluffy structure.

  11. Sapropels and the age of hominins Omo I and II, Kibish, Ethiopia. (United States)

    McDougall, Ian; Brown, Francis H; Fleagle, John G


    The provenance and age of two Homo sapiens fossils (Omo I and Omo II) from the Kibish Formation in southern Ethiopia have been much debated. Here we confirm that Omo I and the somewhat more primitive-looking Omo II calvariae are from similar stratigraphic levels in Member I of the Kibish Formation. Based on (40)Ar/(39)Ar age measurements on alkali feldspar crystals from pumice clasts in the Nakaa'kire Tuff, a tuffaceous bed in Member I just below the hominin levels, we place an older limit of 198+/-14 ka (weighted mean age=196+/-2 ka) for the hominins. A younger limit of 104+/-7 ka (weighted mean age=104+/-1 ka) is provided by feldspars separated from pumice clasts in the Aliyo Tuff in Member III. Geological evidence indicates rapid deposition of each member of the Kibish Formation, concurrent with deposition of sapropels in the Mediterranean Sea. The (40)Ar/(39)Ar age measurements, together with correlations with sapropels, indicate that the hominin fossils are close in age to the older limit. Our preferred estimate of the age of the hominins is 195+/-5 ka, making them the earliest well-dated anatomically modern humans yet described.

  12. Catastrophic debris avalanche deposit of Socompa volcano, northern Chile (United States)

    Francis, P. W.; Gardeweg, M.; Ramirez, C. F.; Rothery, D. A.


    Between 10,000 and 500 yr ago the Socompa volcano in northern Chile experienced a catastrophic collapse of a 70 deg sector of the original cone, causing a debris avalanche that descended nearly 3000 m vertically and traveled more than 35 km from the volcano. The deposits cover some 490 sq km and have a minimum volume of 15 cu km. Parts of the original cone slumped in a nearly coherent form and are now preserved as large blocks more than 400 m high. The primary avalanche traveled northwestward over sloping ground before coming to rest transiently, forming a prominent marginal ridge, and then slid away northeastward to form a secondary flow, overriding much of the primary avalanche deposit. Abundant, prismatic, jointed dacite blocks within the debris avalanche deposit and a thin, fine-grained pumiceous deposit beneath it suggest that the collapse was triggered by magmatic activity and may have been accompanied by a violent lateral blast. Collapse was followed by eruption of pumiceous pyroclastic flows and extrusion of voluminous dacite domes.

  13. Paleomagnetic and AMS studies of the El Castillo ignimbrite, central-east Mexico: Source and rock magnetic nature (United States)

    Alva-Valdivia, L. M.; Agarwal, A.; Caballero-Miranda, C.; García-Amador, B. I.; Morales-Barrera, W.; Rodríguez-Elizarraráz, S.; Rodríguez-Trejo, A.


    Lithological, petromagnetic, paleomagnetic and magnetic fabric studies are employed to determine the flow direction and the location of the source of the, 2.44 to 2.21 Ma, El Castillo ignimbrite in the central-east Mexico. Based on the increasing matrix to pumice ratio and decreasing pumice size, the ignimbrite field is divided into the northwestern, central and south-southeastern sectors. Lithological comparisons among the three sectors reveal that the ignimbrite had flowed from NW to SE, and the source is in the NW part of the study area. Thermomagnetic results concur with the increasing matrix proportions from the proximal to the distal sector. The coercivity and magnetization ratios of the hysteresis parameters are lower in the SE sector than in the NW and central sectors. The dominant flow direction inferred through magnetic fabrics, at most sites, is NW to SE, which coincides with the direction inferred from lithological comparisons. However, at some sites magnetic fabrics demonstrate flow towards ENE or other various directions. The paleomagnetic analysis and field observations reveal that these anomalous directions are a consequence of anticlockwise block rotation and tilting due to normal and lateral faulting in the region.

  14. Robust date for the Bronze Age Avellino eruption (Somma-Vesuvius): 3945 ± 10 calBP (1995 ± 10 calBC) (United States)

    Sevink, Jan; van Bergen, Manfred J.; van der Plicht, Johannes; Feiken, Hendrik; Anastasia, Carmela; Huizinga, Annika


    We found Bronze Age lake sediments from the Agro Pontino graben (Central Italy) to contain a thin (2-3 cm) continuous tephra layer composed of lithics, crystals and minor volcanic glass. Tephrochronological and compositional constraints strongly suggest that this layer represents the Avellino pumice eruption, which has also been identified in Central Italian lake cores. Its provenance is corroborated by electron-microprobe analyses performed on juvenile pumice grains, showing that the tephra layer is probably the distal equivalent of the EU2 event of the Avellino eruption. We used multiple 14C age estimations of two lacustrine sequences with intercalated tephra layer, from the western border zone (Migliara 44.5) and the centre of the former lake (Campo Inferiore), for in tandem dating of this eruption, employing the OxCal code, which yielded a robust age of 3945 ± 10 calBP (1995 ± 10 calBC). To date, this is the only study providing both a terminus post and terminus ante quem of this precision, also demonstrating the advantage of dating distal tephra layers in a clear stratigraphic context over proximal deposits in sequences with major stratigraphic hiatuses. Our new results underscore the importance of the Avellino tephra layer as a precise time marker for studies on the Early Bronze Age of Central Italy.

  15. Qualitative and quantitative evaluation of human dental enamel after bracket debonding: a noncontact three-dimensional optical profilometry analysis. (United States)

    Ferreira, Fabiano G; Nouer, Darcy F; Silva, Nelson P; Garbui, Ivana U; Correr-Sobrinho, Lourenço; Nouer, Paulo R A


    The aim of this study was to undertake a qualitative and quantitative evaluation of changes on enamel surfaces after debonding of brackets followed by finishing procedures, using a high-resolution three-dimensional optical profiler and to investigate the accuracy of the technique. The labial surfaces of 36 extracted upper central incisors were examined. Before bonding, the enamel surfaces were subjected to profilometry, recording four amplitude parameters. Brackets were then bonded using two types of light-cured orthodontic adhesive: composite resin and resin-modified glass ionomer cement. Finishing was performed by three different methods: pumice on a rubber cup, fine and ultrafine aluminum oxide discs, and microfine diamond cups followed by silicon carbide brushes. The samples were subsequently re-analyzed by profilometry. Wilcoxon signed-rank test, Kruskal-Wallis test (p enamel roughness when diamond cups followed by silicon carbide brushes were used to finish surfaces that had remnants of resin-modified glass ionomer adhesive and when pumice was used to finish surfaces that had traces of composite resin. Enamel loss was minimal. The 3D optical profilometry technique was able to provide accurate qualitative and quantitative assessment of changes on the enamel surface after debonding. Morphological changes in the topography of dental surfaces, especially if related to enamel loss and roughness, are of considerable clinical importance. The quantitative evaluation method used herein enables a more comprehensive understanding of the effects of orthodontic bonding on teeth.

  16. Submarine pyroclastic deposits in Tertiary basins, NE Slovenia

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    Polona Kralj


    Full Text Available In Tertiary basins of NE Slovenia, Upper Oligocene volcanic activity occurred in a submarine environment that experienced contemporaneous clastic sedimentation. Pyroclastic deposits are essentially related to gas- and watersupported eruption-fed density currents. At Trobni Dol, the Lako Basin, an over 100 m thick deposit formed by a sigle sustained volcanic explosion that fed gas-supported pyroclastic flow. Diagnostic features are large matrixshard content, normal grading of pumice lapilli, collapsed pumice lapilli and the presence of charcoal. In the Smrekovec Volcanic Complex, several but only up to 5 m thick deposits related to eruption-fed gassupported pyroclastic flows occur. Deposits settled from water-supported eruption-fed density currents form fining- and thinning-upward sedimentary units which resemble the units of volcaniclastic turbidites. Pyroclastic deposits related to gas- and water-supported density currents occur in an up to 1000 m thick succession composed of coherent volcanics, autoclastic, pyroclastic, reworked volcaniclastic and mixed volcaniclastic-siliciclastic deposits that indicate a complex explosive and depositional history of the Smrekovec Volcanic Complex.

  17. Tsunami deposits at high altitudes on the flanks of volcanic islands (United States)

    Paris, Raphael


    It is actually difficult to infer the mechanisms and dynamics of giant mass failures of oceanic shield volcanoes and to evaluate related tsunami hazards. Marine conglomerates and gravels found at unusually high elevations in Hawaii, Cape Verde, Mauritius and Canary Islands are often interpreted as being the result of tsunami waves generated by such massive flank failures. In the first part of this contribution, we document tsunami deposits (marine gravels with pumices) attached to the northwestern slopes of Tenerife, Canary Islands, at altitudes up to 132 m asl. Stratigraphy of the deposits and composition of the pumices allows identifying sources of the successive tsunamis and proposing a new scenario for the Icod flank failure and El Abrigo caldera-forming eruption ca. 170 ka. Then we propose a litterature review of tsunami deposits at high altitudes on the flanks of volcanic islands, and especially oceanic shield volcanoes. These deposits are discussed in terms of texture, structure, composition and particularly the juvenile volcanic material, and implications for better understanding the mechanisms controlling massive flank failures.

  18. Stratigraphy and alteration, 15 shallow thermal gradient holes, Roosevelt Hot Springs KGRA and vicinity, Millard and Beaver Counties, Utah

    Energy Technology Data Exchange (ETDEWEB)

    Hulen, J.B.


    Fifteen shallow thermal gradient drill holes were recently completed by Geothermal Power Corporation (GPCR) in the vicinity of the Roosevelt Hot Springs KGRA. Five holes penetrated Tertiary granitic rocks and Precambrian gneiss east of the KGRA. Seven holes completed entirely in alluvium near the southwestern corner of the KGRA encountered a near-surface marker horizon of Pleistocene pumice and perlite. Maximum calculated alluvial sedimentation rates since initial deposition of this pumice and perlite range from 1 foot in 12,500 years to 1 foot in 2,300 years. Three holes east of the Mineral Mountains penetrated late Cenozoic basaltic andesite beneath a thin veneer of alluvium. All 15 GPCR drill holes appear to be peripheral to a central zone of anomalously high thermal gradient and low resisitivity delineated by previous investigations. GPCR-8 and -14, however, are characterized by high heat flow and relatively abundant manganese oxide mineralization, which may reflect a favorable hydrologic system controlling thermal fluid flow at depth. These holes thus seem most encouraging for discovery of a deeper high-temperature geothermal resource.

  19. Eruption of a major Holocene pyroclastic flow at Citlaltépetl volcano (Pico de Orizaba), México, 8.5 9.0 ka (United States)

    Carrasco-Núñez, Gerardo; Rose, William I.


    Multiple volcanic eruptions occurred between 8500 and 9000 yr. B.P. from the central crater of Citlaltépetl Volcano generating a series of pyroclastic flows that formed a deposit with a total volume of about 0.26 km 3 (D.R.E.). The flows descended in all directions around the crater, but they were mostly controlled by topography and deposited in valleys or local topographic depressions up to about 30 km from vent. Although the flows were apparently emplaced without much violence, some features of the deposits reveal local turbulent conditions and an expanded fluidization that can be related to moderate flow velocities. The deposit has two members: the lower one consists of multiple flow units, and the upper one includes a single flow unit and a thin basal pumice-fall. Both members are lithologically similar and dominated by dense, andesitic scoriae with minor amounts of different pumice types (andesitic, dacitic, and banded), and lithics in a silty matrix. The eruption probably had a low-pressure 'boiling-over' mechanism and was possibly triggered by mixing of dacitic and andesitic magmas. Juvenile material in the pyroclastic-flow deposit is compositionally similar to that of Holocene lava flows at Citlaltépetl, which have apparently resulted from magma homogenization of mafic and silicic end members. Because the system is continuously injected with new basaltic-andesitic magma, a recurrence of explosive activity is possible in future eruptions.

  20. BAHAN PENYERAP KMnO4 DAN ASAM L-ASKORBAT DALAM PENGEMASAN AKTIF (ACTIVE PACKAGING UNTUK MEMPERPANJANG MASA SIMPAN DAN MEMPERTAHANKAN MUTU BUAH DUKU (Lansium domesticum Corr. [Adsorbers for KMnO4 and L-Ascorbic Acid in the Active Packaging to Prolong the Shelve-Life and Maintain the Quality of Lanzone (Lansium domesticum Corr. Fruits

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    Soesiladi E Widodo


    Full Text Available To develop an active packaging of lanzone (Lansium domisticum Corr. Fruits, KmnO4 as an ethylene scavenger and L-ascorbic acid as an oxygent scavenger were inserted into packaging. As direct contact of KmnO4 with agricultural product was not recommended and due to the liquid characteristic of both scavenger was carried out. This research was aimed at finding out the best adsorbers for KmnO4, L-ascorbic acid, and their combination in an active packaging to prolog the shelve-life and to maintain the quality of lanzone fruits. The result showed that 1 among the four adsorbers tested, pumice could was the best alternative as a KmnO4 or L-ascorbic acid adsorbers, and 2 spon and pumice were the best alternative adsorber for the combination of KmnO4 or L-ascorbic acid. Both adsorber were effective in prolonging the shelve-live (8-11 days longer than with out packaging and as good as using silica gel and vermiculite and maintaining the quality of lanzone fruits.

  1. The Avellino plinian eruption of Somma-Vesuvius (3760 y.B.P.): the progressive evolution from magmatic to hydromagmatic style (United States)

    Rolandi, G.; Mastrolorenzo, G.; Barrella, A. M.; Borrelli, A.


    A detailed stratigraphic analysis of the Avellino plinian deposit of the Somma-Vesuvius volcano shows a complicated eruptive sequence controlled by a combination of magmatic and hydromagmatic processes. The role of external water on the eruptive dynamics was most relevant in the very early phase of the eruption when the groundwater explosively interacted with a rising, gas-exolving magma body creating the first conduit. This phase generated pyroclastic surge and phreatoplinian deposits followed by a rapidly increasing discharge of a gas-rich, pure magmatic phase which erupted as the most violent plinian episode. This continuing plinian phase tapped the magma chamber, generating about 2.9 km 3 of reverse-graded fallout pumice, more differentiated at the base and more primitive at the top (white and gray pumice). A giant, plinian column, rapidly grew up reaching a maximum height of 36 km. The progressive magma evacuation at a maximum discharge rate of 10 8 kg/s that accompanied a decrease of magmatic volatile content in the lower primitive magma allowed external water to enter the magma chamber, resulting in a drastic change in the eruptive style and deposit type. Early wet hydromagmatic events were followed by dry ones and only a few, subordinated magmatic phases. A thick, impressive sequence of pyroclastic surge bedsets of over 430 km 2 in area with a total volume of about 1 km 3 is the visible result of this hydromagmatic phase.

  2. Secondary hydroeruptions in pyroclastic-flow deposits: Examples from Mount St. Helens (United States)

    Moyer, T.C.; Swanson, D.A.


    Secondary hydroeruptions occur in pyroclastic-flow deposits when water or ice is trapped beneath hot pyroclastic debris and rapidly heated to steam. These eruptions display various styles of activity including fumarolic degassing, tephra fountaining, and explosive cratering. The deposits, which occupy the layer 3 stratigraphic position on the top of pyroclastic-flow units, can be distinguished from ash-cloud material by lateral thickness variation, clast composition, and other sedimentary features. The ejecta of secondary hydroeruptions comprise a subset of hydrovolcanic pyroclastic deposits. A small secondary hydroeruption observed on the Mount St. Helens pumice plain in 1981 produced tephra that was emplaced ballistically, by deposition from base surges, and by fallout from an eruption column. Stratigraphic descriptions and grain-size analysis of the ejecta from several secondary craters on the pumice plain demonstrate that the bedforms produced by a hydroeruption change with crater diameter. In particular, craters of small diameter are surrounded by interbedded ripple-laminated ash horizons and nonstratified, fines-depleted units; large craters have ejecta ramparts comprised of coarse dunes and antidunes. These bedform changes are related to a progressive increase in eruptive energy, which produces base surges of greater power and eruptive columns of greater height. We suggest that the style of activity displayed during a secondary hydroeruption is controlled by both the total thermal energy of the system and the permeability of the pyroclastic overburden. ?? 1987.

  3. Gunung Api purba Watuadeg: Sumber erupsi dan posisi stratigrafi

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    Sutikno Bronto


    Full Text Available lava flows of pyroxene basalt containing 50 wt.% SiO are exposed at Opak River, west of Watuadeg Village, Sleman - Yogyakarta. The length of flow structures is between 2 – 10 m, with diameter of 0.5 – 1.0 m and it has a glassy skin at the surface body. Flow directions vary from N70E in the northern side, through N 120E in the middle to N 150E in the southern side. About 150 m away from the river to the west, there is a small hill about 15 m high, that has a similar composition with the pillow lavas. Both lava flows and the small hill are composed of pyroxene basalt, dark grey in color, hypocrystalline vitrophyre to porphyritic texture, with fine-grained phenocrysts of pyroxene (10 % and plagioclase (25 % set in glassy groundmass. These data indicate that the small hill was the eruption source of the basaltic pillow lavas. The lavas are overlain by pumice-rich volcaniclastic rocks, composed of tuff, lapillistones and pumice breccias, that are known as the Semilir Formation. Near the contact with lavas, the volcaniclastic rocks contain some fragments of pyroxene basalt, similar composition with the pillow lavas. This fact, together with analyses of petrology, volcanology, and radiometric dating show that the basaltic pillow lavas are unconformably overlain by the Semilir Formation.  

  4. Observations and modelling of soil slip-debris flow initiation processes in pyroclastic deposits: the Sarno 1998 event

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    G. B. Crosta


    Full Text Available Pyroclastic soils mantling a wide area of the Campanian Apennines are subjected to recurrent instability phenomena. This study analyses the 5 and 6 May 1998 event which affected the Pizzo d’Alvano (Campania, southern Italy. More than 400 slides affecting shallow pyroclastic deposits were triggered by intense and prolonged but not extreme rainfall. Landslides affected the pyroclastic deposits that cover the steep calcareous ridges and are soil slip-debris flows and rapid mudflows. About 30 main channels were deeply scoured by flows which reached the alluvial fans depositing up to 400 000 m3 of material in the piedmont areas. About 75% of the landslides are associated with morphological discontinuities such as limestone cliffs and roads. The sliding surface is located within the pyroclastic cover, generally at the base of a pumice layer. Geotechnical characterisation of pyroclastic deposits has been accomplished by laboratory and in situ tests. Numerical modelling of seepage processes and stability analyses have been run on four simplified models representing different settings observed at the source areas. Seepage modelling showed the formation of pore pressure pulses in pumice layers and the localised increase of pore pressure in correspondence of stratigraphic discontinuities as response to the rainfall event registered between 28 April and 5 May. Numerical modelling provided pore pressure values for stability analyses and pointed out critical conditions where stratigraphic or morphological discontinuities occur. This study excludes the need of a groundwater flow from the underlying bedrock toward the pyroclastic cover for instabilities to occur.

  5. Evaluación de la dureza superficial en amalgamas en función de tipos de aleaciones, momentos y tipos de pulimentos

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    Juliana Panazzolo Ramos


    Full Text Available The aim of this study was to analyze in vitro surface hardness (micro-indentation tester Wolpert of different types of amalgam alloys varying the technique and polishing time. Tested were the amalgam: Velvalloy, Permite e Dispersalloy. For each material, 2 polishing techniques were accomplished: T1 (bladed finishing burs + abrasive rubber points + pumice-water slurry in Robinson polishing brush and; T2 (abrasive rubber points + pumice-water slurry in Robinson polishing brush, at 2 periods of time: P1 (immediately - 15 min after condensation and P2 (after 24 h. For each experimental condition, 5 samples were prepared. For each sample, 2 indentations were taken and the average was determined. Were made analysis using ANOVA and Tukey test. Were concluded that: a using the Permite alloy with polishing after 24 h the surface hardness of restoration will be higher; b the technique T2 enhances the hardness of dental amalgams and c alloy Permite with polished immediately were statisticaly equal than Velvalloy polished after 24 h.

  6. Observations and modelling of soil slip-debris flow initiation processes in pyroclastic deposits: the Sarno 1998 event (United States)

    Crosta, G. B.; Dal Negro, P.

    Pyroclastic soils mantling a wide area of the Campanian Apennines are subjected to recurrent instability phenomena. This study analyses the 5 and 6 May 1998 event which affected the Pizzo d'Alvano (Campania, southern Italy). More than 400 slides affecting shallow pyroclastic deposits were triggered by intense and prolonged but not extreme rainfall. Landslides affected the pyroclastic deposits that cover the steep calcareous ridges and are soil slip-debris flows and rapid mudflows. About 30 main channels were deeply scoured by flows which reached the alluvial fans depositing up to 400 000 m3 of material in the piedmont areas. About 75% of the landslides are associated with morphological discontinuities such as limestone cliffs and roads. The sliding surface is located within the pyroclastic cover, generally at the base of a pumice layer. Geotechnical characterisation of pyroclastic deposits has been accomplished by laboratory and in situ tests. Numerical modelling of seepage processes and stability analyses have been run on four simplified models representing different settings observed at the source areas. Seepage modelling showed the formation of pore pressure pulses in pumice layers and the localised increase of pore pressure in correspondence of stratigraphic discontinuities as response to the rainfall event registered between 28 April and 5 May. Numerical modelling provided pore pressure values for stability analyses and pointed out critical conditions where stratigraphic or morphological discontinuities occur. This study excludes the need of a groundwater flow from the underlying bedrock toward the pyroclastic cover for instabilities to occur.

  7. Volcanic ash: What it is and how it forms

    Energy Technology Data Exchange (ETDEWEB)

    Heiken, G.


    There are four basic eruption processes that produce volcanic ash: (1) decompression of rising magma, gas bubble growth, and fragmentation of the foamy magma in the volcanic vent (magmatic), (2) explosive mixing of magma with ground or surface water (hydrovolcanic), (3) fragmentation of country rock during rapid expansion of steam and/or hot water (phreatic), and (4) breakup of lava fragments during rapid transport from the vent. Variations in eruption style and the characteristics of volcanic ashes produced during explosive eruptions depend on many factors, including magmatic temperature, gas content, viscosity and crystal content of the magma before eruption, the ratio of magma to ground or surface water, and physical properties of the rock enclosing the vent. Volcanic ash is composed of rock and mineral fragments, and glass shards, which is less than 2 mm in diameter. Glass shard shapes and sizes depend upon size and shape of gas bubbles present within the magma immediately before eruption and the processes responsible for fragmentation of the magma. Shards range from slightly curved, thin glass plates, which were broken from large, thin-walled spherical bubble walls, to hollow needles broken from pumiceous melts containing gas bubbles stretched by magma flow within the volcanic vent. Pumice fragments make up the coarser-grained portions of the glass fraction. Particle sizes range from meters for large blocks expelled near the volcanic vent to nanometers for fine ash and aerosol droplets within well-dispersed eruption plumes. 18 refs., 6 figs., 1 tab.

  8. How to dose powdered activated carbon in deep bed filtration for efficient micropollutant removal. (United States)

    Altmann, Johannes; Ruhl, Aki S; Sauter, Daniel; Pohl, Julia; Jekel, Martin


    Direct addition of powdered activated carbon (PAC) to the inlet of a deep bed filter represents an energy- and space-saving option to remove organic micropollutants (OMPs) during advanced wastewater treatment or drinking water purification. In this lab-scale study, continuous dosing, preconditioning a filter with PAC and combinations thereof were investigated as possible dosing modes with respect to OMP adsorption efficiency. Continuous dosing resulted in decreasing effluent concentrations with increasing filter runtime due to adsorption onto accumulating PAC in the filter bed. Approximately constant removal levels were achieved at longer filter runtimes, which were mainly determined by the dose of fresh PAC, rather than the total PAC amount embedded. The highest effluent concentrations were observed during the initial filtration stage. Meanwhile, preconditioning led to complete OMP adsorption at the beginning of filtration and subsequent gradual OMP breakthrough. PAC distribution in the pumice filter was determined by the loss on ignition of PAC and pumice and was shown to be relevant for adsorption efficiency. Preconditioning with turbulent upflow led to a homogenous PAC distribution and improved OMP adsorption significantly. Combining partial preconditioning and continuous dosing led to low initial effluent concentrations, but ultimately achieved concentrations similar to filter runs without preconditioning. Furthermore, a dosing stop prior to the end of filtration was suitable to increase PAC efficiency without affecting overall OMP removals.

  9. Geology of the region of Guadalajara, Mexico, and its relationships with processes of subsidence (United States)

    Suarez-Plascencia, C.; Delgado-Argote, L. A.; Nuñez-Cornu, F. J.; Sanchez, J. J.


    The city of Guadalajara, Mexico, began an accelerated urban growth in early 1950. During a span of 25 years a large number of gullies were artificially filled, with the aim of incorporating new areas for urbanization, particularly in the areas north and west of the city. These gullies originally formed a complex dendritic-type system, whose evolution may be associated with faults or fracture zones whose current identification are only possible based on escarpments along the Canyon of the Rio Grande de Santiago (CRGS), north of Guadalajara. Reports of affectations documented in the 80's described subsidence in buildings and infrastructure, a process that has been continued during 2008. We present the results of work done in the CRGS, which is a tectonic erosive-depression with an average depth of 500 m and exhibits a sequence of volcanic and sedimentary deposits with rapid lateral facies changes. The stratigraphic column spans a 15 km-long section along the Matatlán-Arcediano road, and, from top to bottom contains: 1) Unconsolidated pumice and tuffs with an average thickness of 12 m; 2) basaltic lavas with average thickness of 60 m; 3) the San Gaspar ignimbrite; 4) fluvial- sedimentary deposits with a thickness of approximately 20 meters that include both sub-rounded and angular volcanic clasts, with sizes up to 0.15 m; 5) a thick sequence of ignimbrites and dacitic lavas. At a depth of 1200 m.a.s.l. in the town of Arcediano, the basal sequence is composed of dacites and andesites with interbedded pumice-rich ignimbrites with 10-20 m thickness. The Rio Grande de Santiago talweg to 1018 m.a.s.l. (apparently the base of the sequence) is formed by andesite lava. In the area of San Gaspar we identified oblique-normal left-lateral faults in lavas, with a strike 191° and a dip 89°. In the Colimilla dam, 1297 m.a.s.l., we observed normal faulting (strike 267° and dip 81°), with 20-30 m jumps with reference to a unit of tephra of 3-10 m thickness. The lavas in this

  10. Compositional zoning of the bishop tuff (United States)

    Hildreth, W.; Wilson, C.J.N.


    Compositional data for >400 pumice clasts, organized according to eruptive sequence, crystal content, and texture, provide new perspectives on eruption and pre-eruptive evolution of the >4600 km3 of zoned rhyolitic magma ejected as the BishopTuff during formation of Long Valley caldera. Proportions and compositions of different pumice types are given for each ignimbrite package and for the intercalated plinian pumice-fall layers that erupted synchronously. Although withdrawal of the zoned magma was less systematic than previously realized, the overall sequence displays trends toward greater proportions of less evolved pumice, more crystals (0-5 24 wt %), and higher FeTi-oxide temperatures (714-818??C). No significant hiatus took place during the 6 day eruption of the BishopTuff, nearly all of which issued from an integrated, zoned, unitary reservoir. Shortly before eruption, however, the zoned melt-dominant portion of the chamber was invaded by batches of disparate lower-silica rhyolite magma, poorer in crystals than most of the resident magma but slightly hotter and richer in Ba, Sr, andTi. Interaction with resident magma at the deepest levels tapped promoted growth ofTi-rich rims on quartz, Ba-rich rims on sanidine, and entrapment of near-rim melt inclusions relatively enriched in Ba and CO2.Varied amounts of mingling, even in higher parts of the chamber, led to the dark gray and swirly crystal-poor pumices sparsely present in all ashflow packages. As shown by FeTi-oxide geothermometry, the zoned rhyolitic chamber was hottest where crystal-richest, rendering any model of solidification fronts at the walls or roof unlikely.The main compositional gradient (75-195 ppm Rb; 0.8-2.2 ppm Ta; 71-154 ppm Zr; 0.40-1.73% FeO*) existed in the melt, prior to crystallization of the phenocryst suite observed, which included zircon as much as 100 kyr older than the eruption.The compositions of crystals, though themselves largely unzoned, generally reflect magma temperature and

  11. The dynamics of the Breccia Museo eruption (Campi Flegrei, Italy) and the significance of spatter clasts associated with lithic breccias (United States)

    Perrotta, Annamaria; Scarpati, Claudio


    The Breccia Museo Member is a pyroclastic deposit produced during an eruptive event that occurred in the southwestern sector of Campi Flegrei about 20,000 years ago. Two depositional units divided by a co-ignimbrite ash-fall deposit have been recognized. Facies variations in the deposits resulted from the interaction between the flow and paleomorphology, from the relative abundance of the lithic and juvenile components supplied by the source, and from the variations of the flow regime. The Lower Depositional Unit is a pyroclastic flow deposit characterized by a thick, coarse valley facies laterally grading into a thin, layered and fine-grained overbank facies. These different facies are due to the interaction between a density-stratified flow and topography. The more basal, high-concentration part of the flow was deposited along the axis of the paleovalleys (valley facies), whereas the upper, low-concentration part was deposited on the slopes (overbank facies). Vertical variations of the structures observed in the deposits of the Lower Depositional Unit resulted from flow unsteadiness during emplacement and, hence, on the variations of the suspended load fallout from the low-concentration upper part of the flow to the high-concentration boundary layer. The Upper Depositional Unit, made up of the Breccia, Spatter and Upper Pumice Flow Units, consists of horizons of lithic breccias and coarse welded spatter which thicken into the valleys. They are closely related to a gas-pipe-rich ash and pumice flow deposit. The strongly fines-poor character of the breccias and spatter beds is due to a very rapid segregation of the dense and coarse clasts and to the high rates of gas ascent through the hindered-settling zone in the basal part of the flow. After deposition of the majority of the dense and coarse material, the subsequent high-density depositional system came to rest immediately, thus yielding a pyroclastic flow deposit that is closely associated with the breccia. The

  12. Eruptive History of the Rhyolitic Guangoche Volcano, Los Azufres Volcanic Field, Central Mexico (United States)

    Rangel Granados, E.; Arce, J. L.; Macias, J. L.; Layer, P. W.


    Guangoche is a rhyolitic and polygenetic volcano with a maximum elevation of 2,760 meters above sea level. It is situated to the southwest of the Los Azufres Volcanic Field (LAVF), in the central sector of the Trans-Mexican Volcanic Belt. Guangoche volcano is the youngest volcano described within the LAVF. It shows a horseshoe shaped crater open to the south, with a central lava dome. Its eruptive history during late Pleistocene has been intense with six explosive eruptions that consists of: 1) A southwards sector collapse of the volcano that generated a debris avalanche deposit with megablocks of heterogenous composition; 2) A plinian-type eruption that generated a pumice fall deposit and pyroclastic density currents by column collapse at 30.6 ka; 3) A plinian-type eruption "White Pumice Sequence" (29 ka) that developed a 22-km-high eruptive column, with a MDR of 7.0 x 107 kg/s (vol. = 0.53 km3); 4) A dome-destruction event, "Agua Blanca Pyroclastic Sequence" at 26.7 ka, that deposited a block-and-ash flow deposit; 5) A subplinian-plinian type eruption "Ochre Pyroclastic Sequence" (<26 ka) with an important initial phreatomagmatic phase, that generated pyroclastic density currents and pumice fallouts. The subplinian-plinian event generated a 16-km-high eruptive column, with a MDR of 1.9 x 107 kg/s, and magma volume of 0.38 km3; 6) The eruptive history ended with a subplinian eruption (<<26 ka), that generated a multilayered fall deposit, that developed a 11-km-high eruptive column, with a MDR of 2.9 x 106 kg/s and a magma volume of 0.26 km3. Volcanic activity at Guangoche volcano has been intense and future activity should not be discarded. Unfortunately, the last two events have not been dated yet. Guangoche rhyolitic magma is characterized by low-Ba contents suggesting crystal mush extraction for their genesis.

  13. Assessment of farm soil, biochar, compost and weathered pine mulch to mitigate methane emissions. (United States)

    Syed, Rashad; Saggar, Surinder; Tate, Kevin; Rehm, Bernd H A


    Previous studies have demonstrated the effective utility of volcanic pumice soil to mitigate both high and low levels of methane (CH4) emissions through the activity of both γ-proteobacterial (type I) and α-proteobacterial (type II) aerobic methanotrophs. However, the limited availability of volcanic pumice soil necessitates the assessment of other farm soils and potentially suitable, economical and widely available biofilter materials. The potential biofilter materials, viz. farm soil (isolated from a dairy farm effluent pond bank area), pine biochar, garden waste compost and weathered pine bark mulch, were inoculated with a small amount of volcanic pumice soil. Simultaneously, a similar set-up of potential biofilter materials without inoculum was studied to understand the effect of the inoculum on the ability of these materials to oxidise CH4 and their effect on methanotroph growth and activity. These materials were incubated at 25 °C with periodic feeding of CH4, and flasks were aerated with air (O2) to support methanotroph growth and activity by maintaining aerobic conditions. The efficiency of CH4 removal was monitored over 6 months. All materials supported the growth and activity of methanotrophs. However, the efficiency of CH4 removal by all the materials tested fluctuated between no or low removal (0-40 %) and high removal phases (>90 %), indicating biological disturbances rather than physico-chemical changes. Among all the treatments, CH4 removal was consistently high (>80 %) in the inoculated farm soil and inoculated biochar, and these were more resilient to changes in the methanotroph community. The CH4 removal from inoculated farm soil and inoculated biochar was further enhanced (up to 99 %) by the addition of a nutrient solution. Our results showed that (i) farm soil and biochar can be used as a biofilter material by inoculating with an active methanotroph community, (ii) an abundant population of α-proteobacterial methanotrophs is essential

  14. Genesis of low-Ba rhyolite by reheating of a crystal mush: The case of the 29 ka White Pyroclastic Sequence, Guangoche stratovolcano, Trans-Mexican Volcanic Belt, central Mexico (United States)

    Rangel Granados, E.; Arce, J. L.; Macias, J. L.


    Rhyolitic magmas are commonly related to explosive eruptions, and its precursors are almost absent that makes the volcanoes very dangerous for the communities around them. The knowledge of pre-eruptive conditions of such magmas is important to decipher the mechanisms capable to produce explosive eruptions. In this work we studied the Guangoche stratovolcano located to the southwest of the Los Azufres Volcanic Field in central Mexico. Guangoche has a horse-shoe shaped (1.6 km wide) crater, opened to the south, and a central rhyolitic dome. During late Pleistocene the volcano produced several explosive eruptions one of which occurred 29 ka and deposited the so-called White Pyroclastic Sequence (WPS). This sequence was emplaced by a Plinian-subplinian eruption of moderate size (VEI 5). This eruption ejected 0.5 km3 of rhyolitic magma and deposited a pumice fallout followed by three pumice rich pyroclastic flow deposits. White and banded juvenile pumice, used to determine pre-eruptive storage conditions with hydrothermal experiments, have similar mineralogy and chemical composition. Petrography, coupled with mineral chemical data and hydrothermal experiments, suggest that prior to eruption, the melt was a high-silica rhyolite (77.3 + 0.3 wt. % SiO2) stagnated at a water pressure of 130-170 MPa (assuming vapor saturation at depth), at a temperature of 762-793°C (on the basis of Fe-Ti oxide thermometry) and had a mineral assemblage of sanidine, plagioclase, biotite, hornblende, Fe-Ti oxides and zircon. Quartz-hosted melt inclusions indicate the presence of a relatively cold (536-759°C; TitaniQ geothermometer) quartz-feldespathic crystal body (crystal mush), stored at depths between 3.2 and 8.9 km (74-204 MPa), thus quartz probably represents partially assimilated xenocrysts. We propose that the 29 ka rhyolitic WPS magma was produced by reheating of a crystal mush that partially melted and incorporated quartz xenocrysts. This rhyolitic low-Ba, Eu, and Sr melt was stored

  15. Evolution of the 120 ka caldera-forming eruption of Kutcharo volcano, eastern Hokkaido, Japan: Geologic and petrologic evidence for multiple vent systems and rapid generation of pyroclastic flow (United States)

    Hasegawa, Takeshi; Matsumoto, Akiko; Nakagawa, Mitsuhiro


    We investigated the eruptive sequence and temporal evolution of juvenile materials during the 120 ka Kutcharo pumice flow IV (Kp IV) eruption, which was the most voluminous (175 km3: bulk volume) caldera-forming eruption of Kutcharo volcano. The eruptive deposits are divided into four units in ascending order. Unit 1 is widely dispersed and consists of silt-sized, cohesive ash. Unit 2 is a thin, moderately sorted pumice fall deposit with a restricted distribution and small volume (caldera. Juvenile materials consist mainly of rhyolite pumice (74%-78% SiO2) associated with a minor amount of scoria (52%-73% SiO2) that are found only northwest of the caldera in Unit 3 and Unit 4. These scoriae can be classified on the basis of the P2O5 contents of their matrix glass into low-P, medium-P, and high-P types, which are almost entirely restricted to the lower part of Unit 3, Unit 4, and the upper part of Unit 3, respectively. These three types display distinct mixing trends with the rhyolitic compositions in SiO2-P2O5 variation diagrams. This evidence indicates that three distinct mafic magmas were independently and intermittently injected into the main body of silicic magma to erupt from the northwestern part of the magma system. Mafic injections did not occur in the southern part of the magma system. This petrologic evidence implies that the northwestern and southeastern flows of Unit 3 are heterotopic, contemporaneous products derived from multiple vent systems. Although Unit 2 was derived from an eruptive column, its volume is very small compared to Plinian fall deposits of typical caldera-forming eruptions. In our interpretation, the activity of the Kp IV eruption reached its climax rapidly, depositing Unit 3, without first producing a stable Plinian column. The presence of multiple vent systems could have allowed the system to bypass an initial eruptive stage with a stable Plinian column and begin its climactic stage, represented by Unit 3, rapidly. Multiple vents

  16. Hydrologic Tests at Characterization Well R-14

    Energy Technology Data Exchange (ETDEWEB)

    S. McLin; W. Stone


    Well R-14 is located in Ten Site Canyon and was completed at a depth of 1316 ft below ground surface (bgs) in August 2002 within unassigned pumiceous deposits located below the Puye Formation (fanglomerate). The well was constructed with two screens positioned below the regional water table. Individual static depths measured for each isolated screen after the Westbay{trademark} transducer monitoring system was installed in mid-December 2002 were nearly identical at 1177 ft bgs, suggesting only horizontal subsurface flow at this time, location, and depth. Screen 1 straddles the geologic contact between the Puye fanglomerate and unassigned pumiceous deposits. Screen 2 is located about 50 ft deeper than screen 1 and is only within the unassigned pumiceous deposits. Constant-rate, straddle-packer, injection tests were conducted at screen 2, including two short tests and one long test. The short tests were 1 minute each but at different injection rates. These short tests were used to select an appropriate injection rate for the long test. We analyzed both injection and recovery data from the long test using the Theis, Theis recovery, Theis residual-recovery, and specific capacity techniques. The Theis injection, Theis recovery, and specific capacity methods correct for partial screen penetration; however, the Theis residual-recovery method does not. The long test at screen 2 involved injection at a rate of 10.1 gallons per minute (gpm) for 68 minutes and recovery for the next 85 minutes. The Theis analysis for screen 2 gave the best fit to residual recovery data. These results suggest that the 158-ft thick deposits opposite screen 2 have a transmissivity (T) equal to or greater than 143 ft{sup 2}/day, and correspond to a horizontal hydraulic conductivity (K) of at least 0.9 ft/day. The specific capacity method yielded a T value equal to or greater than 177 ft{sup 2}/day, and a horizontal K of at least 1.1 ft/day. Results from the injection and recovery phases of the

  17. Pyroclastic density currents associated with the 2008-2009 eruption of Chaitén Volcano (Chile): forest disturbances, deposits, and dynamics (United States)

    Major, Jon J.; Pierson, Thomas C.; Hoblitt, Richard P.; Moreno, Hugo


    Explosive activity at Chaitén Volcano in May 2008 and subsequent dome collapses over the following nine months triggered multiple, small-volume pyroclastic density currents (PDCs). The explosive activity triggered PDCs to the north and northeast, which felled modest patches of forest as far as 2 km from the caldera rim. Felled trees pointing in the down-current direction dominate the disturbance zones. The PDC on the north flank of Chaitén left a decimeters-thick, bipartite deposit having a basal layer of poorly sorted, fines-depleted pumice-and-lithic coarse ash and lapilli, which transitions abruptly to fines-enriched pumice-and-lithic coarse ash. The deposit contains fragments of mostly uncharred organics near its base; vegetation protruding above the deposit is uncharred. The nature of the forest disturbance and deposit characteristics suggest the PDC was dilute, of relatively low temperature (-1. It was formed by directionally focused explosions throughout the volcano's prehistoric, intracaldera lava dome. Dilute, low-temperature PDCs that exited the caldera over a low point on the east-southeast caldera rim deposited meters-thick fill of stratified beds of pumice-and-lithic coarse ash and lapilli. They did not fell large trees more than a few hundred of meters from the caldera rim and were thus less energetic than those on the north and northeast flanks. They likely formed by partial collapses of the margins of vertical eruption columns. In the Chaitén River valley south of the volcano, several-meter-thick deposits of two block-and-ash flow (BAF) PDCs are preserved. Both have a coarse ash matrix that supports blocks and lapilli predominantly of lithic rhyolite dome rock, minor obsidian, and local bedrock. One deposit was emplaced by a BAF that traveled an undetermined distance downvalley between June and November 2008, apparently triggered by partial collapse of a newly effused lava dome on that started growing on 12 May. A second, and larger, BAF related

  18. Culture-Independent Identification of Manganese-Oxidizing Genes from Deep-Sea Hydrothermal Vent Chemoautotrophic Ferromanganese Microbial Communities Using a Metagenomic Approach (United States)

    Davis, R.; Tebo, B. M.


    Microbial activity has long been recognized as being important to the fate of manganese (Mn) in hydrothermal systems, yet we know very little about the organisms that catalyze Mn oxidation, the mechanisms by which Mn is oxidized or the physiological function that Mn oxidation serves in these hydrothermal systems. Hydrothermal vents with thick ferromanganese microbial mats and Mn oxide-coated rocks observed throughout the Pacific Ring of Fire are ideal models to study the mechanisms of microbial Mn oxidation, as well as primary productivity in these metal-cycling ecosystems. We sampled ferromanganese microbial mats from Vai Lili Vent Field (Tmax=43°C) located on the Eastern Lau Spreading Center and Mn oxide-encrusted rhyolytic pumice (4°C) from Niua South Seamount on the Tonga Volcanic Arc. Metagenomic libraries were constructed and assembled from these samples and key genes known to be involved in Mn oxidation and carbon fixation pathways were identified in the reconstructed genomes. The Vai Lili metagenome assembled to form 121,157 contiguous sequences (contigs) greater than 1000bp in length, with an N50 of 8,261bp and a total metagenome size of 593 Mbp. Contigs were binned using an emergent self-organizing map of tetranucleotide frequencies. Putative homologs of the multicopper Mn-oxidase MnxG were found in the metagenome that were related to both the Pseudomonas-like and Bacillus-like forms of the enzyme. The bins containing the Pseudomonas-like mnxG genes are most closely related to uncultured Deltaproteobacteria and Chloroflexi. The Deltaproteobacteria bin appears to be an obligate anaerobe with possible chemoautotrophic metabolisms, while the Chloroflexi appears to be a heterotrophic organism. The metagenome from the Mn-stained pumice was assembled into 122,092 contigs greater than 1000bp in length with an N50 of 7635 and a metagenome size of 385 Mbp. Both forms of mnxG genes are present in this metagenome as well as the genes encoding the putative Mn

  19. Geological evolution of a pleistocene rhyolitic center — Sierra La Primavera, Jalisco, México (United States)

    Mahood, Gail A.


    The Sierra La Primavera volcanic complex consists of late Pleistocene comenditic lava flows and domes. ash-flow tuff, air-fall pumice, and cold caldera-lake sediments. The earliest lavas were erupted about 120,000 years ago, and were followed approximately 95,000 years ago by the eruption of about 20 km 3 of magma as ash flows that form the compositionally-zoned Tala Tuff. Collapse of the roof zone of the magma chamber led to the formation of a shallow 11-km-diameter caldera. It soon filled with water, forming a caldera lake in which sediment began to collect. At about the same time, two central domes erupted through the middle of the lake and a "giant pumice horizon", an important stratigraphic marker, was deposited. Shortly thereafter ring domes erupted along two parallel arcs: one along the northeast portion of the ring fracture, and the other crossing the middle of the lake. All these events occurred during a period of approximately 5,000-10,000 years. Sedimentation continued and a period of volcanic quiescence was marked by the deposition of some 30 m of fine-grained ashy sediments virtually free from pumice lapilli. Approximately 75,000 years ago, a new group of ring domes erupted at the southern margin of the lake. These domes are lapped by only 10-20 m of sediments, as uplift resulting from renewed insurgence of magma brought an end to the lake. This uplift culminated in the eruption, beginning approximately 60,000 years ago, of aphyric lavas along a southern arc. The youngest of these lavas erupted approximately 20,000-30,000 years ago. The four major fault systems in the Sierra La Primavera are related to caldera collapse or to uplift caused by the insurgence of the southern are magma. Steam vents and larga-discharge 65°C hot springs are associated with the faulting. Calculated equilibrium temperatures of the geothermal fluids are ˜170°C, but temperatures in excess of 240°C have been encountered in an exploratory drill hole. A seismic survey showed

  20. The A.D. 472 ``Pollena'' eruption: volcanological and petrological data for this poorly-known, plinian-type event at vesuvius (United States)

    Rosi, Mauro; Santacroce, Roberto


    The pyroclastic products of a poorly-known eruption of Vesuvius (ascribed by a combination of historic and radiocarbon data to A.D. 472) have been investigated from both volcanological and petrological points of view. The eruptive sequence starts with pumice-fall deposits (three units can be recognized) that darken upwards where there are sandwave interbeds. Surge deposits cover the pumice-fall bed and thick pyroclastic-flow deposits represent the uppermost levels of the deposit. Isopach maps of both the pumice-fall and pyroclastic-flow deposits led to an estimate of the total volume of tephra of about 0.32 km 3. The eruptive sequence and the distribution of lithic ejecta are similar to those of the major Plinian eruptions of Somma-Vesuvius (although the volume involved is significantly lower) and reflect an increase in the hydromagmatic character of the eruption with time. The products range in composition from phonolites (first-erupted) to phonolitic leucitites with gradual changes upwards. Whole rock chemistry and microprobe mineralogy indicate that the Pollena sequence represents a liquid line of descent towards the phonolitic minimum of petrogeny's residua system. Fractionation occurred within a shallow magma chamber (P H 2O probably slightly higher than 1 kb) and was mainly controlled by leucite and clinopyroxene. The basic parental magma approached the composition of the recent period (A.D. 1631-1944), tephritic leucitites of Vesuvius. The phonolitic magma can be derived from a leucititic parent by fractionating about 50% solid phases. A two-stage fractionation model is suggested: the first stage occurred during the rise of magma from the deep source and the second within the shallow magma chamber. The rate of magma introduction during the 150 to 200 year repose time preceeding the eruption probably averaged 1.2 to 1.7 × 10 -3 km 3-yr -1. These conditions were probably favorable for the occurrence of magma-mixing within the convecting zone of the magma

  1. Eyewitness, stratigraphy, chemistry, and eruptive dynamics of the 1913 Plinian eruption of Volcán de Colima, México (United States)

    Saucedo, R.; Macías, J. L.; Gavilanes, J. C.; Arce, J. L.; Komorowski, J. C.; Gardner, J. E.; Valdez-Moreno, G.


    Based on the stratigraphic record of the deposits, analysis of previous works, historic archives, and eyewitness accounts the 1913 eruption of Volcán de Colima was reconstructed. The eruption started in 17 January and peaked in 20 January, 1913. It occurred in three main phases: 1) An opening phase with the generation of Merapi-type pyroclastic flows (units F 1, F 2, F 3) and a pyroclastic surge (S 1), 2) A vent-clearing phase with strong explosions that produced Vulcanian-Soufriere-type pyroclastic flows (F 4) and a pyroclastic surge (S 2) which destroyed the summit dome decompressing the magma system, and 3) a Plinian phase with the establishment of a ˜ 23 km high column dispersing a fallout (C 1) to the NE followed by the collapse of the column that generated a pyroclastic surge (S 3) and 15-km long pumice-rich pyroclastic flows (F 5). After the eruption, remobilization of the pyroclastic material generated lahars in main gullies around the crater. Fallout C 1 blanketed an area of ˜ 191,318 km 2 covering the cities of Guzman, Guadalajara, and Saltillo (Coahuila) located at 725 km from the source. It had a volume of 1.4 km 3 (0.57 km 3 DRE = Dense Rock Equivalent). The total volume of pyroclastic flow and surge deposits was 0.26 km 3 (0.07 km 3 DRE) giving a total volume of the eruption of 1.66 km 3 (0.64 km 3 DRE). The Plinian column lasted 4.6 h with a total mass of 1.5 × 10 12 kg and a mass eruption rate of 9.02 × 10 7 kg/s. The column height and the ejected magma volume indicate that the 1913 eruption had a VEI = 5 being the largest event in the historical record of Colima Volcano. Juvenile scoria and pumice consisted of Pl > Opx > Cpx > Hbl + accessory titanomagnetite + Ap and Ol with reaction rims. Chemistry of juvenile scoria and pumice samples is andesitic very homogeneous (58.3 ± 0.5 wt.% SiO 2) and similar to the 1818 juvenile products (58.9 ± 0.2 wt.% SiO 2). The presence of banded scoria, olivine phenocrysts with reaction rims, and trace

  2. Eruption Depths, Magma Storage and Magma Degassing at Sumisu Caldera, Izu-Bonin Arc: Evidence from Glasses and Melt Inclusions (United States)

    Johnson, E. R.


    Island arc volcanoes can become submarine during cataclysmal caldera collapse. The passage of a volcanic vent from atmospheric to under water environment involves complex modifications of the eruption style and subsequent transport of the pyroclasts. Here, we use FTIR measurements of the volatile contents of glass and melt inclusions in the juvenile pumice clasts in the Sumisu basin and its surroundings (Izu-Bonin arc) to investigate changes in eruption depths, magma storage and degassing over time. This study is based on legacy cores from ODP 126, where numerous unconsolidated (250 m), massive to normally graded pumice lapilli-tuffs were recovered over four cores (788C, 790A, 790B and 791A). Glass and clast geochemistry indicate the submarine Sumisu caldera as the source of several of these pumice lapilli-tuffs. Glass chips and melt inclusions from these samples were analyzed using FTIR for H2O and CO2 contents. Glass chips record variable H2O contents; most chips contain 0.6-1.6 wt% H2O, corresponding to eruption depths of 320-2100 mbsl. Variations in glass H2O and pressure estimates suggest that edifice collapse occurred prior-to or during eruption of the oldest of these samples, and that the edifice may have subsequently grown over time. Sanidine-hosted melt inclusions from two units record variably degassed but H2O-rich melts (1.1-5.6 wt% H2O). The lowest H2O contents overlap with glass chips, consistent with degassing and crystallization of melts until eruption, and the highest H2O contents suggest that large amounts of degassing accompanied likely explosive eruptions. Most inclusions, from both units, contain 2-4 wt% H2O, which further indicates that the magmas crystallized at pressures of ~50-100 MPa, or depths ~400-2800 m below the seafloor. Further glass and melt inclusion analyses, including major element compositions, will elucidate changes in magma storage, degassing and evolution over time.

  3. Equilibrium and Disequilibrium of 230Th-238U in Zircon from the Minoan Eruption, Santorini, Aegean Sea, Greece (United States)

    Schmitt, A. K.; Stockli, D. F.; Song, E. J.; Storm, S.


    The Minoan eruption (ca. 1600 BCE; 40-80 km3 dense rock equivalent) occurred after a ca. 18 ka period of dormancy followed by rapid reinvigoration through arrival of new magma from deep reservoirs colliding with evolved magmas in shallow storage. Although zoned phenocrysts indicate brief timescales ranging between years to decades for final pre-eruptive magma recharge and mixing, it remains unclear how magma accumulation vs. crystallization were balanced in the subvolcanic reservoir during the preceding inter-eruptive cycle. To directly probe magma presence over the repose interval prior to the Minoan eruption and further back in time, we reconnoitered the potential of U-Th zircon geochronology to date the crystallization of individual zircon crystals from pumice from the Minoan eruption. Zircon crystals were extracted from composite pumice samples (several kg each) from basal fall out deposits using gravity and magnetic separation. Etching in cold HF removed adherent glass and revealed the shape of crystals, which were pressed into indium metal to expose unpolished rims to the ion beam of a CAMECA IMS 1270 secondary ionization mass spectrometer. Adherent glass was ubiquitous, indicating that crystals were in contact with melt at the time of eruption. Six of 18 crystals were in 230Th/238U secular equilibrium, two crystals yielded ages of ca. 160 ka, and the remaining rims dated between eruption age and ca. 20 ka. Low Th/U of some secular equilibrium zircon suggests recycling of metamorphic basement zircon, which is also indicated by the presence of rutile in heavy mineral separates. U-Th dates also reveal recycling of zircon from Pleistocene intrusions that likely represent left-over magma from antecedent eruption cycles. We tentatively interpret the dominant zircon population with near-eruption to ca. 20 ka ages to indicate continuous melt presence underneath Santorini during the last repose interval. Distinguishing a hiatus in zircon crystallization between 20 ka

  4. 40Ar/(39)Ar dating of the Kapthurin Formation, Baringo, Kenya. (United States)

    Deino, Alan L; McBrearty, Sally


    The(40)Ar/(39)Ar radiometric dating technique has been applied to tuffs and lavas of the Kapthurin Formation in the Tugen Hills, Kenya Rift Valley. Two variants of the(40)Ar/(39)Ar technique, single-crystal total fusion (SCTF) and laser incremental heating (LIH) have been employed to date five marker horizons within the formation: near the base, the Kasurein Basalt at 0.61+/-0.04 Ma; the Pumice Tuff at 0.543+/-0.004 Ma; the Upper Kasurein Basalt at 0.552+/-0.015 Ma; the Grey Tuff at 0.509+/-0.009 Ma; and within the upper part of the formation, the Bedded Tuff at 0.284+/-0.012 Ma. The new, precise radiometric age determination for the Pumice Tuff also provides an age for the widespread Lake Baringo Trachyte, since the Pumice Tuff is the early pyroclastic phase of this voluminous trachyte eruption. These results establish the age of fossil hominids KNM-BK 63-67 and KNM-BK 8518 at approximately 0.510-0.512 Ma, a significant finding given that few Middle Pleistocene hominids are radiometrically dated. The Kapthurin hominids are thus the near contemporaries of those from Bodo, Ethiopia and Tanzania. A flake and core industry from lacustrine sediments in the lower part of the formation is constrained by new dates of 0.55-0.52 Ma, a period during which the Acheulian industry, characterized by handaxes, is known throughout East Africa. Points, typical of the Middle Stone Age (MSA), are found in Kapthurin Formation sediments now shown to date to between 0.509+/-0.009 Ma and 0.284+/-0.012 Ma. This date exceeds previous estimates for the age of the MSA elsewhere in East Africa by 49 ka, and establishes the age of Acheulian to MSA transition for the region. Evidence of the use of the Levallois technique for the manufacture of both small flakes and biface preforms, the systematic production of blades, and the use and processing of red ochre also occurs in this interval. The presence of blades and red ochre at this depth is important as blades signify a high degree of technical

  5. Quaternary volcanism in the Acambay graben, Mexican Volcanic Belt: Re-evaluation for potential volcanic danger in central Mexico (United States)

    Aguirre-Diaz, G. J.; Pedrazzi, D.; Lacan, P.; Roldan-Quintana, J.; Ortuňo, M.; Zuniga, R. R.; Laurence, A.


    The Mexican Volcanic Belt (MVB) is best known for the major active stratovolcanoes, such as Popocatépetl, Citlaltépetl and Colima. The most common stratovolcanoes in this province are modest-size cones with heights of 800 to 1000 m. Examples are Tequila, Sangangüey, Las Navajas, Culiacán, La Joya, El Zamorano, Temascalcingo and Altamirano; these last two were formed within the Acambay Graben in central MVB. The Acambay graben (20 x 70 km) is 100 km to the NW of Mexico City, with E-W trending seismically active normal faults; in particular the Acambay-Tixmadejé fault related to a mB =7 earthquake in 1912. Within the graben there are many volcanic structures, including calderas, domes, cinder cones and stratovolcanoes; Temascalcingo and Altamirano are the largest, with about 800 and 900 m heights, respectively. Temascalcingo is mostly composed of dacitic lavas and block and ash flow deposits. Includes a 3 x 2.5 km summit caldera and a magmatic sector collapse event with the associated debris avalanche deposit. 14C ages of 37-12 ka correspond to the volcano's latest phases that produced pyroclastic deposits. A major plinian eruption formed the San Mateo Pumice with an age of <20 Ka. Altamirano volcano is poorly studied; it is andesitic-dacitic, composed of lavas, pyroclastic flow deposits, and pumice fallouts. Morphologically is better preserved than Temascalcingo, and it should be younger. 14C ages of 4.0-2.5 ka were performed in charcoal within pyroclastic flow deposits that apparently were erupted from Altamirano. An undated 3 m thick pumice fallout on the flanks of Altamirano volcano could be also Holocene. It represents a major explosive event. The relatively young ages found in volcanic deposits within the Acambay graben raise the volcanic danger level in this area, originally thought as an inactive volcanic zone. The two major volcanoes, Temascalcingo and Altamirano, should be considered as dormant volcanoes that could restart activity at any time. We

  6. The Laramide Mesa formation and the Ojo de Agua caldera, southeast of the Cananea copper mining district, Sonora, Mexico (United States)

    Cox, Dennis P.; Miller, Robert J.; Woodbourne, Keith L.


    The Mesa Formation extends from Cananea, Mexico, southeast to the Sonora River and is the main host rock of Laramide porphyry copper deposits in the Cananea District and at the Alacran porphyry prospect to the east. The Mesa consists of two members-a lower andesite and an upper dacite. The lowest part of the dacite member is a crystal tuff about 100 m thick. This tuff is the outfall of a caldera centered near the village of Ojo de Agua, dated by 40Ar/39Ar at 65.8 Ma ?0.4. The Ojo de Agua Caldera is about 9 km in diameter and is filled by a light gray biotite dacite tuff with abundant flattened pumice fragments. The volume of the caldera is estimated to be 24 km3.

  7. Beauty and the body: the origins of cosmetics. (United States)

    Blanco-Dávila, F


    Ancient cultures were as preoccupied with the aesthetics of appearance as individuals are today. Dermabrasion for skin resurfacing has been performed with salt, pumice, ground grains, bone, and horn. Chemical peels have been performed with acids, metals, botanical extracts, or animal fats. Tattoos, ear piercing, makeup, skin treatments, and massages have existed for the past 5000 years. According to history, when the rise of more complex societies brought an ever-increasing demand for cosmesis, perfumers, cosmetologists, barbers, and gentlewomen became pioneers, undertaking and developing the cosmetic practices that had evolved through the ages. With the consolidation of medical specialties concerned with the management of skin care, the scientific method has been applied to adapt and perfect many of the procedures that had been carried out with only empirical knowledge. To have a better perspective from which to envision future technical and technological developments, plastic surgeons should be familiar with the origins of cosmetics and some cosmetology practices that society demands.

  8. Caracterización morfoscópica de los materiales piroclásticos sálicos del sur de Tenerife (Islas Canarias

    Directory of Open Access Journals (Sweden)

    Alonso, J. J.


    Full Text Available In this work, several morphological aspects of volcanic ash grains from southern Tenerife are studied by S.E.M. Important variations in vesiculation, fracture and wheathering of pyroclasts are observed. It's possible to characterize diferent types of deposits (pyroclastic falIs, pyroclastic flow, surges, etc. in function of the pumice fragments surface.En este trabajo se estudian mediante M.E.B. (Microscopio Electrónico de Barrido diversos aspectos morfológicos de granos de cenizas volcánicas del sur de Tenerife. Son observadas importantes variaciones en la vesiculación, fracturación y alteraciones de los piroclastos. Es posible caracterizar distintos tipos de depósitos (piroclastos de caída, coladas piroclásticas, surges, etc. en función de las características superficiales de los fragmentos pumíticos.

  9. Interpreting compositional zonation of the Zaragoza ignimbrite from Los Humeros caldera, Central Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Carrasco-Nunez, Gerardo [Centro de Geociencias, UNAM, Campus Juriquilla, Queretaro, Qro. (Mexico); McCurry, Michael [Department of Geology, Idaho State University, Pocatello, ID (United States); Branney, Michael J [Department of Geology, University of Leicester, Leicester (United Kingdom)


    Compositional zonation in ignimbrites is relatively common, and is often inferred to record gradual withdrawal by an eruption of a density-stratified magma chamber (with silicic magma towards the top and more dense, mafic magma at the bottom). We show that this model does not match observations at the ca. 0.1 Ma Zaragoza ignimbrite from Los Humeros caldera in central Mexico. Detailed petrologic studies reveal a more complex scenario: the ignimbrite exhibits a 'double' vertical zonation based on the compositions of pumice lapilli. We present evidence for mingling and limited mixing occurred during or immediately before the caldera-forming eruption. One possibility to explain the observations is that the ignimbrite eruption occurred in response to intrusion of a hybridized andesitic magma into a rhyodacitic magma chamber.

  10. Interpreting compositional zonation of the Zaragoza ignimbrite from Los Humeros caldera, Central Mexico (United States)

    Carrasco-Núñez, Gerardo; McCurry, Michael; Branney, Michael J.


    Compositional zonation in ignimbrites is relatively common, and is often inferred to record gradual withdrawal by an eruption of a density-stratified magma chamber (with silicic magma towards the top and more dense, mafic magma at the bottom). We show that this model does not match observations at the ca. 0.1 Ma Zaragoza ignimbrite from Los Humeros caldera in central Mexico. Detailed petrologic studies reveal a more complex scenario: the ignimbrite exhibits a `double' vertical zonation based on the compositions of pumice lapilli. We present evidence for mingling and limited mixing occurred during or immediately before the caldera-forming eruption. One possibility to explain the observations is that the ignimbrite eruption occurred in response to intrusion of a hybridized andesitic magma into a rhyodacitic magma chamber.

  11. Geochemistry of the 1989-1990 eruption of redoubt volcano: Part I. Whole-rock major- and trace-element chemistry (United States)

    Nye, C.J.; Swanson, S.E.; Avery, V.F.; Miller, T.P.


    The 1989-1990 eruption of Redoubt Volcano produced medium-K calc-alkaline andesite and dacite of limited compositional range (58.2-63.4% SiO2) and entrained quenched andesitic inclusions (55% SiO2) which bear chemical similarities to the rest of the ejecta. The earliest (December 15) magmas are pumiceous, often compositionally banded, and the majority is relatively mafic ( 60 wt.%). They have Mg, Cr, Ni, Sc, and V contents higher than the andesites, but lower than Redoubt basalts and basaltic andesites. Thus, they may be crystallization products of andesites, but do not represent the cumulate residue of basalt fractionation. The xenoliths were probably derived from a shallow or intermediate crustal chamber. ?? 1994.

  12. The beginning of explosive eruptions on a location lacking volcanoes: A case study on the Hijiori volcano, Northeastern Japan (United States)

    Miyagi, I.


    The volcanic activity of Hijiori volcano (N38 36°f 35°f°f, E140 9°f 20°f°f, WGS84) is reported in detail as a case study to understand how a new felsic volcano commences the activity. Hijiori volcano, a small caldera with approximately 2 km in diameter, is one of the 108 active volcanoes in Japan, which erupted at about 12,000 years ago (in Calendar age) on the location where no volcanic body existed before the activity. From the field survey, it turns out that the suite of activities initiated by the major eruption that deposited a valley filling non-welded pumice flows. Finally the pumice flows covered the range 5 km to the southward and 9 km to the northward with total maximum thickness of about 150 m. The accompanying pumice fall and ash fall extends 60 km to the eastward. Although span of the activity is as short as the resolving power of radiocarbon dating, there recognized a quiescence for three times. After the every quiescence, phreatic (or phreatomagmatic) activities deposited lapilli falls and flows in the proximity. Total volume of the valley filling pyroclastic flows and the air falls are estimated to be 1.4 and 0.6 cubic km, respectively. All the pumices from the three major eruptions are similar in their phenocryst content (50- vol. percent), phenocryst assemblages (Pl, Qz, OPx, Hb, and Mt), bulk chemistry (c.a. 64 wt. percent SiO2), and in isotopic (Sr, Nd) compositions. Mt phenocrysts have no zoning profiles and their chemical compositions (Al2O3, Mg/Mn) are mostly unique through the eruptive sequences, suggesting that the physicochemical conditions of the magma were the same just before the each eruption. On the contrary Pl, Qz, OPx and Hb phenocrysts showed distinct zoning, suggesting that the magma chamber of Hijiori volcano had been disturbed repeatedly by such as magma mixing that continued intermittently before and during the eruptive activities. The observed difference between Mt and the other phenocrysts implies that there were

  13. Postglacial eruptive history, geochemistry, and recent seismicity of Aniakchak volcano, Alaska Peninsula (United States)

    Bacon, Charles R.; Neal, Christina A.; Miller, Thomas P.; McGimsey, Robert G.; Nye, Christopher J.


    Aniakchak is a Pleistocene to Holocene composite volcano of the Alaska–Aleutian arc that suffered at least one caldera-forming eruption in postglacial time and last erupted in 1931. The oldest recognized postglacial eruption, Aniakchak I, produced andesite ignimbrite ca. 9,500–7,500 14C yr B.P. Subsequently, a vent northeast of the summit issued dacite–rhyodacite magma ca. 7,000 14C yr B.P. mainly as the Black Nose Pumice falls. The ca. 3,430 14C yr B.P. Aniakchak II eruption produced rhyodacite plinian fall followed by rhyodacite and andesite ignimbrite extending ≥50 km to the Bering Sea and Pacific coasts and resulted in collapse of the 10-km-diameter caldera.

  14. Effect of prophylactic treatments on the superficial roughness of dental tissues and of two esthetic restorative materials Efeito de tratamentos profiláticos na rugosidade superficial de tecidos dentais e de dois materiais restauradores estéticos

    Directory of Open Access Journals (Sweden)

    Daniele Salami


    Full Text Available Dental prophylaxis is a common way to remove dental plaque and stain, both undesirable factors in most dentistry procedures. However, besides cleaning the tooth surface, prophylactic techniques may increase the surface roughness of restorations and dental tissues, which, in turn, may result in plaque accumulation, superficial staining and superficial degradation. This study evaluated the effect of three prophylactic techniques - sodium bicarbonate jet, pumice paste and whiting paste - on the superficial roughness of two restorative materials - a composite resin and a compomer - and on the superficial roughness of two dental surfaces - enamel and cementum/dentin - through rugosimetric and scanning electron microscopy (SEM analysis. Statistical analysis of the rugosimetric data showed that the use of pumice paste on enamel produced a significantly smoother surface than the natural surface. However, comparing the effect of the three techniques, prophylaxis with the pumice paste produced a rougher surface than did the other techniques as regards enamel and cementum/dentin probably due to its abrasiveness. On composite resin, the pumice paste only produced a rougher surface than did the whiting paste. On compomer, all of the applied treatments produced similar results. Based on rugosimetric and SEM analysis, we could conclude that the prophylactic treatments employed did not improve roughness of the studied surfaces. As to the effects of the techniques, they were different depending on the surfaces on which the prophylactic treatments were applied.A profilaxia dental é uma prática comum para a remoção de placa bacteriana e outros indutos que dificultam a realização dos procedimentos restauradores. Entretanto, como efeito secundário à limpeza, pode-se ter uma superfície mais rugosa e sujeita a manchamentos e degradações. O presente estudo avaliou os efeitos de três técnicas de profilaxia - jato de bicarbonato de sódio, pasta de pedra


    Witkind, Irving J.; Ridenour, James


    A mineral survey conducted within the Centennial Mountains Wilderness study area in Montana and Idaho showed large areas of probable and substantiated resource potential for phosphate. Byproducts that may be derived from processing the phosphate include vanadium, chromium, uranium, silver, fluorine, and the rare earths, lanthanum and yttrium. Results of a geochemical sampling program suggest that there is little promise for the occurrence of base and precious metals in the area. Although the area contains other nonmetallic deposits, such as coal, building stone, and pumiceous ash they are not considered as mineral resources. There is a probable resource potential for oil and gas and significant amounts may underlie the area around the Peet Creek and Odell Creek anticlines.

  16. Constructing a reference tephrochronology for Augustine Volcano, Alaska (United States)

    Wallace, K.; Coombs, M. L.


    Augustine Volcano is the most historically active volcano in Alaska's populous Cook Inlet region. Past on-island work on pre-historic tephra deposits mainly focused on using tephra layers as markers to help distinguish among prevalent debris-avalanche deposits on the island (Waitt and Beget, 2009, USGS Prof Paper 1762), or as source material for petrogenetic studies. No comprehensive reference study of tephra fall from Augustine Volcano previously existed. Numerous workers have identified Holocene-age tephra layers in the region surrounding Augustine Island, but without well-characterized reference deposits, correlation back to the source volcano is difficult. The purpose of this detailed tephra study is to provide a record of eruption frequency and magnitude, as well as to elucidate physical and chemical characteristics for use as reference standards for comparison with regionally distributed Augustine tephra layers. Whole rock major- and trace-element geochemistry, deposit componentry, and field context are used to correlate tephra units on the island where deposits are coarse grained. Major-element glass geochemistry was collected for use in correlating to unknown regional tephra. Due to the small size of the volcanic island (9 by 11 km in diameter) and frequent eruptive activity, on-island exposures of tephra deposits older than a couple thousand years are sparse, and the lettered Tephras B, M, C, H, I, and G of Waitt and Beget (2009) range in age from 370-2200 yrs B.P. There are, however, a few exposures on the south side of the volcano, within about 2 km of the vent, where stratigraphic sections that extend back to the late Pleistocene glaciation include coarse pumice-fall deposits. We have linked the letter-named tephras from the coast to these higher exposures on the south side using physical and chemical characteristics of the deposits. In addition, these exposures preserve at least 5 older major post-glacial eruptions of Augustine. These ultra

  17. Repetitive mixing events and Holocene pyroclastic activity at Pico de Orizaba and Popocatepetl, Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Cantagrel, J.M.; Gourgaud, A.; Robin, C.


    The Holocene volcanic activity which built up the present terminal cones of Pico de Orizaba and Popocatepetl in eastern Mexico, was characterized by repeated pyroclastic Saint-Vincent type eruptions. Radiocarbon data show that these paroxysmal events occurred at more or less regular intervals, and were followed by moderate activity producing ash and pumice falls and andesitic lava flows from the summit craters. Typical ash and scoria pyroclastic flows exhibit a heterogeneous composition given by the interaction of a dacitic component with a more basic andesitic one. Scoria bombs are characterized by banded to emulsified textures, mineralogical disequilibrium assemblages and linear chemical variations on element-element plots as exemplified by the Loma Grande flow at Pico. Periodic replenishments of the magmatic reservoir could be the major phenomenon that started mixing and consequently triggered the pyroclastic eruptions. 22 references.

  18. Repetitive mixing events and holocene pyroclastic activity at Pico de Orizaba and Popocatepetl (Mexico) (United States)

    Cantagrel, J. M.; Gourgaud, A.; Robin, C.


    The Holocene volcanic activity which built up the present terminal cones of Pico de Orizaba and Popocatepetl in eastern Mexico, was characterized by repeated pyroclastic Saint-Vincent type eruptions. Radiocarbon data show that these paroxysmal events occurred at more or less regular intervals, and were followed by moderate activity producing ash and pumice falls and andesitic lava flows from the summit craters. Typical ash and scoria pyroclastic flows exhibit a heterogeneous composition given by the interaction of a dacitic component with a more basic andesitic one. Scoria bombs are characterized by banded to emulsified textures, mineralogical desequilibrium assemblages and linear chemical variations on element-element plots as exemplified by the Loma Grande flow at Pico. Periodic replenishments of the magmatic reservoir could be the major phenomenon that started mixing and consequently triggered the pyroclastic eruptions.

  19. Radiocarbon dates for lava flows and pyroclastic deposits on Sao Miguel, Azores (United States)

    Moore, R.B.; Rubin, M.


    We report 63 new radiocarbon analyses of samples from Sao Miguel, the largest island in the Azores archipelago. The samples are mainly carbonized tree roots and other plant material collected from beneath 20 mafic lava flows and spatter deposits and from within and beneath 42 trachytic pyroclastic flow, pyroclastic surge, mudflow, pumice-fall and lacustrine deposits and lava flows. One calcite date is reported. These dates establish ages for 48 previously undated lava flows and pyroclastic deposits, and revise three ages previously reported. These data are critical to deciphering the Holocene and late Pleistocene eruptive history of Sao Miguel and evaluating its potential volcanic hazards. Average dormant intervals during the past 3000 years are about 400 years for Sete Cidades volcano, 145 years for volcanic Zone 2, 1150 years for Agua de Pau volcano and 320 years for Furnas volcano. No known eruptions have occurred in volcanic Zone 4 during the past 3000 years. -from Authors

  20. Mobility of pyroclastic flows and surges at the Soufriere Hills Volcano, Montserrat (United States)

    Calder, E.S.; Cole, P.D.; Dade, W.B.; Druitt, T.H.; Hoblitt, R.P.; Huppert, H.E.; Ritchie, L.; Sparks, R.S.J.; Young, S.R.


    The Soufriere Hills Volcano on Montserrat has produced avalanche-like pyroclastic flows formed by collapse of the unstable lava dome or explosive activity. Pyroclastic flows associated with dome collapse generate overlying dilute surges which detach from and travel beyond their parent flows. The largest surges partially transform by rapid sedimentation into dense secondary pyroclastic flows that pose significant hazards to distal areas. Different kinds of pyroclastic density currents display contrasting mobilities indicated by ratios of total height of fall H, run-out distance L, area inundated A and volume transported V. Dome-collapse flow mobilities (characterised by either L/H or A/V 2/3) resemble those of terrestrial and extraterrestrial cold-rockfalls (Dade and Huppert, 1998). In contrast, fountain-fed pumice flows and fine-grained, secondary pyroclastic flows travel slower but, for comparable initial volumes and heights, can inundate greater areas.

  1. Geological Results from Drilling in the Poihipi (Western) Sector of the Wairakei Geothermal Field, NZ

    Energy Technology Data Exchange (ETDEWEB)

    Bogie, I.; Lawless, J.V.; MacKenzie, K.M.


    Four wells drilled into the Poihipi Sector on the Western margin of the Wairakei geothermal field have found a similar lithostratigraphy to that encountered in wells previously drilled in the general area. Young pumice breccias overly the Huka Falls Formation, with the latter containing intercalations of the Rautehuia Breccia. This in turn overlies ignimbrites and tuffaceous sediments of the Waiora Formation, which contains flows of Haparangi Rhyolite. This sequence is cut by steeply dipping normal faults which strike to the northeast and for the most part dip towards the northwest. Hydrothermal alteration is virtually limited to the Waiora and Haparangi units where a sequence of interlayered illite-smectite and illite clays are found along with chlorite, quartz, pyrite and calcite. There is a minor occurrence of zeolites. Despite large changes in the area's hydrology in response to exploitation, changes in alteration are limited to a comparatively deep occurrence of kaolinite and minor overprinting of epidote by illitic clay.

  2. 月球的起源和演进%On the Origin and Evolution of the Moon

    Institute of Scientific and Technical Information of China (English)



    由于月球是环绕地球运行的唯一的一颗自然卫星。对月球起源的研究不仅能够发现太阳系星球卫星的形成规律。而且可以揭示字宙星系的演进规律,进而控制星球的演进。因此许多人研究过月球,但是关于月球的起源仍然是一个不解之谜。于是本文作者通过分析和研究地球的演进过程,发现了地球卫星的形成机制.即地球岩石圈在水的长期侵蚀下分裂成一些断块.有的断块外部被溶蚀成许多溶洞,而内部又变成浮石结构,以致比重很小;当共中一个这样的断块的岩基被海水蚀透。使大量的水进入地慢与炽热的岩浆接触时.就会产生巨大的爆炸,将断块炸裂成多个浮石碎块,其中有些浮石碎块在巨大的岩浆喷射力的推动下经过大而深的岩洞可获得第一宇宙速度以上的飞行速度.从而进入绕地球运行的轨道。在这些进入绕地轨道的浮石碎块中有一块体积最大的浮石碎块就是后来形成月球的雏形。后来月雏不断地吸收地球周围的残余物质而变得越来越大.并渐渐地远离地球。%Since the Moon is the only natural satellite of the Earth, the research on the origin of the Moon can not only find out the formation law of the satellites of solar system planets but also reveal the evolution law of galaxies in the universe. Hence many people have studied the Moon, but the origin of the Moon remains a mystery. The authors of this paper, through an analysis on the evolu- tion of the Earth, revealed the formation mechanism of the Moon, that is, some lithospheric fault blocks suffering erosion of water over long periods of time eventually developed many limestone caves, while their inner part became pumice stone, so they had low specific gravity. When the rock foundation of such a fault block was eroded so seriously that a large amount of water entered the mantle to contact super hot magma, a tremendous

  3. The eruption of Vesuvius of 79 AD and its impact on human environment in Pompeii

    Institute of Scientific and Technical Information of China (English)

    LisettaGiacomelli; AnnamariaPerrotta; RobertoScandone; ClaudioScarpati


    The eruption of Vesuvius of 79 AD caused extensive destructions all over the Campanian area, engulfing the cities of Pompeii, Herculaneum, Oplonti and Stabiae.The eruption followed a long quiescence period and the inhabitants of the area were surprised by the volcanic events. The first part of the eruption was characterized by a widespread dispersal of pumices from a high erup-tive column. The second part of the eruption, character-ized by pyroclastic flows emplacement, caused the major damages with extensive life losses in most of the towns surrounding the volcano. In Pompeii, the major casual-ties during the first phase resulted from roof collapses;during the second phase, people were killed either by physical trauma due to the kinetic energy of the flow or by suffucation because of the ash-rich atmosphere.

  4. Petrographic and geochemical characteristics of a section through the Tiva Canyon Tuff at Antler Ridge, Yucca Mountain, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Singer, F.R.; Widmann, B.L.; Dickerson, R.P. [Science Applications International Corp., Golden, CO (United States); Byers, F.M. Jr. [Geological Survey, Denver, CO (United States)


    The Tiva Canyon Tuff of the Paintbrush Group of Miocene age caps much of Yucca Mountain, Nevada and is a compositionally zoned, compound cooling, pyroclastic flow that ranges from a dominantly high-silica rhyolitic base to a quartz-latitic caprock. Petrographic and geochemical studies have focused on rigorously defining the internal stratigraphy of this unit to support the detailed mapping of the Ghost Dance fault and other structures in the central fault block of Yucca Mountain. This study shows that devitrification textures and vapor phase mineralogy, in addition to other physical attributes such as pumice variability (flattening) and crystal content, can be used as distinguishing criteria to better define lithologic zones within the Tiva Canyon Tuff. In addition, the study also shows that the petrographic textures and chemistry of the groundmass vary systematically within recognizable lithologic zones and may be used to characterize and vertically divide litho-stratigraphic zones within the Tiva Canyon Tuff.

  5. Heat Induced Damage Detection by Terahertz (THz) Radiation (United States)

    Rahani, Ehsan Kabiri; Kundu, Tribikram; Wu, Ziran; Xin, Hao


    Terahertz (THz) and sub-terahertz imaging and spectroscopy are becoming increasingly popular nondestructive evaluation techniques for damage detection and characterization of materials. THz radiation is being used for inspecting ceramic foam tiles used in TPS (Thermal Protection System), thick polymer composites and polymer tiles that are not good conductors of ultrasonic waves. Capability of THz electromagnetic waves in detecting heat induced damage in porous materials is investigated in this paper. Porous pumice stone blocks are subjected to long time heat exposures to produce heat induced damage in the block. The dielectric properties extracted from THz TDS (Time Domain Spectroscopy) measurements are compared for different levels of heat exposure. Experimental results show noticeable and consistent change in dielectric properties with increasing levels of heat exposure, well before its melting point.

  6. An evaluation of the geothermal potential of the Tecuamburro Volcano area of Guatemala

    Energy Technology Data Exchange (ETDEWEB)

    Heiken, G.; Duffield, W. (eds.)


    Radiometric ages indicate that the Tecuamburro Volcano and three adjacent lava domes grew during the last 38,300 years, and that a 360-m-wide phreatic crater, Laguna Ixpaco, was formed near the base of these domes about 2900 years ago. Laguna Ixpaco is located within the Chupadero crater, from which pyroxene pumice deposits were erupted 38,300 years ago. Thus, the likelihood is great for a partly molten or solid-but-still-hot near-surface intrusion beneath the area. Fumaroles and hot springs issue locally from the Tecuamburro volcanic complex and near Laguna Ixpaco. Analyses of gas and fluid samples from these and other nearby thermal manifestations yield chemical-geothermometer temperatures of about 150{degree} to 300{degree}C, with the highest temperatures at Ixpaco. The existence of a commercial-grade geothermal reservoir beneath the Ixpaco area seems likely. 84 refs., 70 figs., 12 tabs.

  7. Volcanic succession of the Borovnik Member (Mohorje Formation, Bloke Plateau area, Central Slovenia

    Directory of Open Access Journals (Sweden)

    Stevo Dozet


    Full Text Available A 75 m thick volcanic succession of the Borovnik Member, Mohorje Formation in the Bloke Plateau area consistsof dacitic and rhyolitic rocks deposited in a shallow-marine environment. Volcanic activity begun with lavaflows that underwent extensive disintegration, autobrecciation and mixing with the underlying unconsolidated fine-grained clastic sediments producing dacite/rhyolite-siltstone peperites. Peperites are very rich in fractured plagioclase phenocrysts, and owing to the incorporation of clastic material, they are commonly depleted in silica.The overlying fining-upward pyroclastic sequence is monotonous. Basal parts mainly consist of coarse-grained vitric tuffs that may contain some smaller pumice lapilli. The overlying volcaniclastics are fine-grained vitric tuffs,and in the uppermost parts of the sequence, they are interbedded with cherts.The study confirms the existence of primary volcaniclastic succession in the Bloke Plateau area and excludes its epiclastic or reworked origin.

  8. Volcanic Ash fall Impact on Vegetation, Colima 2005 (United States)

    Garcia, M. G.; Martin, A.; Fonseca, R.; Nieto, A.; Radillo, R.; Armienta, M.


    An ash sampling network was established arround Colima Volcano in 2005. Ash fall was sampled on the North, Northeast, East, Southeast, South, Southwest and West of the volcano. Samples were analyzed for ash components, geochemistry and leachates. Ash fall ocurred on April (12), May (10, 23), June (2, 6, 9, 10, 12, 14), July (27), September (27), October (23) and November (24). Most of the ash is made of andesitic dome-lithics but shows diferences in crystal, juvenile material and lithic content. In May, some samples contained grey and dark pumice (scoria). Texture varies from phi >4 to phi 0. Leachate concentration were low: SO4 (7.33-54.19) Cl- (2.29-4.97) and F- (0.16-0.37). During 2005, Colima Volcano's ash fall rotted some of the guava and peach fruits and had a drying effect on spearment and epazote plants. Even these small ash amounts could have hindered sugar cane and agave growth.

  9. Keeping watch over Colombia’s slumbering volcanoes (United States)

    Ordoñez, Milton; López, Christian; Alpala, Jorge; Narváez, Lourdes; Arcos, Dario; Battaglia, Maurizio


    Located in the Central Cordillera (Colombian Andes), Nevado del Ruiz is a volcanic complex, topped by glaciers, rising 5,321 m above sea level. A relatively small explosive eruption from Ruiz's summit crater on November 13, 1985, generated an eruption column and sent a series of pyroclastic flows and surges across the volcano's ice-covered summit. Pumice and meltwater produced by the hot pyroclastic flows and surges swept into gullies and channels on the slopes of Ruiz as a series of lahars. Within two hours of the beginning of the eruption, lahars had traveled 100 km and left behind a wake of destruction: more than 25,000 people were killed (23,000 in the town of Armero and 2,000 in the town of Chinchiná), about 5,000 injured, and more than 5,000 homes destroyed along the Chinchiná, Gualí, and Lagunillas rivers.

  10. Shallow-storage conditions for the rhyolite of the 1912 eruption at Novarupta, Alaska (United States)

    Coombs, Michelle L.; Gardner, James E.


    Recent studies have proposed contrasting models for the plumbing system that fed the 1912 eruption of Novarupta, Alaska. Here, we investigate the conditions under which the rhyolitic part of the erupted magma last resided in the crust prior to eruption. Geothermometry suggests that the rhyolite was held at ∼800-850 °C, and analyses of melt inclusions suggest that it was fluid saturated and contained ∼4 wt% water. Hydrothermal, water-saturated experiments on rhyolite pumice reveal that at those temperatures the rhyolite was stable between 40 and 100 MPa, or a depth of 1.8-4.4 km. These results suggest that pre-eruptive storage and crystal growth of the rhyolite were shallow; if the rhyolite ascended from greater depths, it did so slowly enough for unzoned phenocrysts to grow as it passed through the shallow crust.

  11. Transitions between explosive and effusive phases during the cataclysmic 2010 eruption of Merapi volcano, Java, Indonesia (United States)

    Preece, Katie; Gertisser, Ralf; Barclay, Jenni; Charbonnier, Sylvain J.; Komorowski, Jean-Christophe; Herd, Richard A.


    Transitions between explosive and effusive activity are commonly observed during dome-forming eruptions and may be linked to factors such as magma influx, ascent rate and degassing. However, the interplay between these factors is complex and the resulting eruptive behaviour often unpredictable. This paper focuses on the driving forces behind the explosive and effusive activity during the well-documented 2010 eruption of Merapi, the volcano's largest eruption since 1872. Time-controlled samples were collected from the 2010 deposits, linked to eruption stage and style of activity. These include scoria and pumice from the initial explosions, dense and scoriaceous dome samples formed via effusive activity, as well as scoria and pumice samples deposited during subplinian column collapse. Quantitative textural analysis of groundmass feldspar microlites, including measurements of areal number density, mean microlite size, crystal aspect ratio, groundmass crystallinity and crystal size distribution analysis, reveal that shallow pre- and syn-eruptive magmatic processes acted to govern the changing behaviour during the eruption. High-An (up to ˜80 mol% An) microlites from early erupted samples reveal that the eruption was likely preceded by an influx of hotter or more mafic magma. Transitions between explosive and effusive activity in 2010 were driven primarily by the dynamics of magma ascent in the conduit, with degassing and crystallisation acting via feedback mechanisms, resulting in cycles of effusive and explosive activity. Explosivity during the 2010 eruption was enhanced by the presence of a `plug' of cooled magma within the shallow magma plumbing system, which acted to hinder degassing, leading to overpressure prior to initial explosive activity.

  12. Collapse calderas (United States)

    Aguirre-Diaz, G. J.; Marti, J.


    A collapse caldera is a volcanic explosive structure that forms during the collapse of crustal blocks on top of a shallow magma chamber. During this collapse, a large volume of magma is evacuated, first explosively, in the form of pyroclastic fallouts and pyroclastic flows, and then effusively, as lava domes or flows after collapse. The result is a catastrophic explosive volcanic collapse that forms a depression that could end with different shapes, circular, oval, rectangular, or irregular. Three main types of collapse calderas can be defined, 1) summit caldera, 2) classic caldera, and 3) graben caldera. Summit calderas are those formed at the top of large volcanoes and are related to relatively small-volume pyroclastic products that include plinian fallouts and ignimbrites, such as Crater Lake, Las Cañadas, and Somma-Vesuvio. Classic calderas are semi-circular to irregular-shaped large structures, several km in diameter that are related to relatively large-volume pyroclastic products including pumice fallouts and widespread ignimbrites, such as Long-Valley, Campi Flegrei, and Los Humeros. Graben calderas are explosive volcano-tectonic collapse structures from which large-volume, ignimbrite-forming eruptions occurred through several vents along the graben walls and the intra-graben block faults causing the collapse of the graben or of a sector of the graben. The main products of graben calderas are surge-deposits and large-volume widespread ignimbrite sheets. Pumice fallouts are practically absent. Examples include the Sierra Madre Occidental in Mexico, La Pacana (Andes), Catalan Pyrenees, and perhaps Scafell (United Kingdom). Any of the three caldera types mentioned above could have collapsed in three different ways, 1) piston, when the collapse occurs as a single crustal block; 2) trap-door, when collapse occurs unevenly along one side while the opposite side remains with no collapse; 3) piece-meal, when collapse occurs as broken pieces of the crust on top of

  13. Source of the tsunami generated by the 1650 AD eruption of Kolumbo submarine volcano (Aegean Sea, Greece) (United States)

    Ulvrova, Martina; Paris, R.; Nomikou, P.; Kelfoun, K.; Leibrandt, S.; Tappin, D. R.; McCoy, F. W.


    The 1650 AD explosive eruption of Kolumbo submarine volcano (Aegean Sea, Greece) generated a destructive tsunami. In this paper we propose a source mechanism of this poorly documented tsunami using both geological investigations and numerical simulations. Sedimentary evidence of the 1650 AD tsunami was found along the coast of Santorini Island at maximum altitudes ranging between 3.5 m a.s.l. (Perissa, southern coast) and 20 m a.s.l. (Monolithos, eastern coast), corresponding to a minimum inundation of 360 and 630 m respectively. Tsunami deposits consist of an irregular 5 to 30 cm thick layer of dark grey sand that overlies pumiceous deposits erupted during the Minoan eruption and are found at depths of 30-50 cm below the surface. Composition of the tsunami sand is similar to the composition of the present-day beach sand but differs from the pumiceous gravelly deposits on which it rests. The spatial distribution of the tsunami deposits was compared to available historical records and to the results of numerical simulations of tsunami inundation. Different source mechanisms were tested: earthquakes, underwater explosions, caldera collapse, and pyroclastic flows. The most probable source of the 1650 AD Kolumbo tsunami is a 250 m high water surface displacement generated by underwater explosion with an energy of ~ 2 × 1016 J at water depths between 20 and 150 m. The tsunamigenic explosion(s) occurred on September 29, 1650 during the transition between submarine and subaerial phases of the eruption. Caldera subsidence is not an efficient tsunami source mechanism as short (and probably unrealistic) collapse durations (< 5 min) are needed. Pyroclastic flows cannot be discarded, but the required flux (106 to 107 m3 · s- 1) is exceptionally high compared to the magnitude of the eruption.

  14. Evidence from cosmic-ray exposure dating based on 36Cl for the pre-Minoan caldera on Santorini, Greece (United States)

    Athanassas, Constantin; Bourlès, Didier; Braucher, Regis; Druitt, Tim; Nomikou, Paraskevi; Léanni, Laetitia


    The physiography of Santorini prior to the Minoan (Late Bronze Age) eruption (17th century BCE) is of great archaeological interest, given the importance of Santorini as a commercial centre and port in the Minoan empire. However, the paleogeography of the pre-Minoan caldera has been a point of controversy: Heiken and McCoy (1984) advocated the existence, in the southern part of the present-day caldera, of a pre-existing caldera formed during the 172 ka Lower Pumice eruption, whereas Druitt and Francaviglia (1992), based on the presence of in situ plinian pumice from the Minoan eruption adhering to the modern cliff, conceived the pre-Minoan (22 ka) caldera as having occupied much of the northern basin of the present-day caldera. With the goal of settling the debate we performed cosmic ray exposure dating employing in situ-produced cosmogenic 36Cl to date different generations of caldera cliffs at Santorini, and hence to identify those cliffs predating the Minoan eruption. Our methodology involved the determination of the in situ-produced cosmogenic 36Cl in basaltic and andesitic rocks cropping out in the cliffs. The samples returned 36Cl CRE ages consistent with previously published field mapping of cliff populations based on geomorphological and stratigraphic arguments (Druitt and Francaviglia 1992), suggesting that much of the present cliff line of northern Santorini predated the Minoan eruption, or was superficially modified by landslips and rockfalls during that eruption. The 36Cl CRE ages enable us to better define the paleogeography of the pre-Minoan caldera. References [1] Druitt, T. H. and Francaviglia, V.1992. Caldera formation on Santorini and the physiography of the islands in the Late Bronze Age. Bulletin of Volcanology 54, 484-493. [2] Heiken G and McCoy F (1984) Caldera development during the Minoan eruption, Thira, Cyclades, Greece. Journal of Geophysical Research: 89 (B10), 8841-8862.

  15. Lichen Persistence and Recovery in Response to Varied Volcanic Disturbances (United States)

    Nelson, P.; Wheeler, T. B.


    Volcanic eruptions produce many ecological disturbances that structure vegetation. While lichens are sensitive to disturbances, little is known about their responses to volcanic disturbances, except for colonization of lava. We examined lichen community responses through time to different disturbances produced by the May 1, 2008 eruption of Volcan Chaiten in south-central Chile. Pre-eruption vegetation near the volcano was old-growth Valdivian temperate rainforest dominated by closed-canopy Nothofagus sp... In 2012, we installed thirteen 1-acre plots across volcanic disturbance zones on which a time-constrained search was done for all macrolichen species, each of which was assigned an approximate log10 categorical abundance. We also installed a 0.2 m2 quadrat on two representative trees per plot for repeat photography of lichen cover. We remeasured at least one plot per disturbance zone in 2014 and re-photographed tree quadrats in 2013 and 2014. We then analyzed species composition and abundance differences among disturbance zones. In 2012, the blast (pyroclastic density flow), scorch (standing scorched forest at the edge of the blast) and deep tephra (>10 cm) zones had the lowest lichen species richness (5-13 species), followed by reference (unimpacted) and shallow (lichen species since 2012 while the light tephra and reference were essentially unchanged. Gravel rain, gravel rain + pumice and flooded forest plots all had about the same number of species in 2014 as 2012. Lichen colonization and growth in tree quadrats varied widely, from very little colonization in the blast to prolific colonization in the gravel rain + pumice zone. Lichen's varied responses to different volcanic disturbances were attributable to varying degrees of mortality and subsequent availability of substrate, quantity of light and removal of competitors. While sensitive to disturbance, lichens are apparently resilient to and can quickly recolonize after a variety of large, violent volcanic

  16. Transporting and Deposition Dynamics in the Plinian Column of Tianchi Volcano, Changbaishan

    Institute of Scientific and Technical Information of China (English)

    Wei Haiquan; Liu Ruoxin; Song Shengrong; Yang Qingfu


    The huge comendite ignimbrite- forming eruption of Tianchi Volcano maintained a stable plinian column during its earlier stage of eruption, and succeeded a collapsing of the column producing pumiceous ignimbrite deposits. It is estimated that the column height (Hb) varied from 20km to 10km in its eruption period, with a maximum height of 25km in the eruption peak. Its umbrella cloud spread into the stratosphere with a top height of 35km (Ht). The dense lithics whose diameter exceeded 8cm followed a ballistics trajectory in a 3km - high gas thrust region, while the smaller lithics and pumices entered the convection region in the column. The initial magma temperature was 780℃. The comendite magma had an exit velocity of 300m/s, volatile content of about 1wt% and lithics of 8.5wt%. From a 400m - wide vent the magma was expelled out with a mass eruption rate of 108.36kg/s, corresponding to a volume rate of 104.95m3/s. Over 1. 3436 × 1019J of energy had been released from Tianchi Volcano, of which the kinetic proportion was about 8 %. The plume had a temperature of -50℃ at the base focus of the cloud and a upward speed of 215m/s. The cloud spread out at a gradually downspeed with the increasement of distance from its center. For example, at a distance of 25km from its center the spreading velocity is about 250m/s, and is about 60m/s at distance of 100km. The main part of the plinian column, that is the convection region, once occurred in the height between 3 to 25km, and its maximum width was about 13km in radius.

  17. Microbial colonization in diverse surface soil types in Surtsey and diversity analysis of its subsurface microbiota (United States)

    Marteinsson, V.; Klonowski, A.; Reynisson, E.; Vannier, P.; Sigurdsson, B. D.; Ólafsson, M.


    Colonization of life on Surtsey has been observed systematically since the formation of the island 50 years ago. Although the first colonisers were prokaryotes, such as bacteria and blue-green algae, most studies have been focused on the settlement of plants and animals but less on microbial succession. To explore microbial colonization in diverse soils and the influence of associated vegetation and birds on numbers of environmental bacteria, we collected 45 samples from different soil types on the surface of the island. Total viable bacterial counts were performed with the plate count method at 22, 30 and 37 °C for all soil samples, and the amount of organic matter and nitrogen (N) was measured. Selected samples were also tested for coliforms, faecal coliforms and aerobic and anaerobic bacteria. The subsurface biosphere was investigated by collecting liquid subsurface samples from a 181 m borehole with a special sampler. Diversity analysis of uncultivated biota in samples was performed by 16S rRNA gene sequences analysis and cultivation. Correlation was observed between nutrient deficits and the number of microorganisms in surface soil samples. The lowest number of bacteria (1 × 104-1 × 105 cells g-1) was detected in almost pure pumice but the count was significantly higher (1 × 106-1 × 109 cells g-1) in vegetated soil or pumice with bird droppings. The number of faecal bacteria correlated also to the total number of bacteria and type of soil. Bacteria belonging to Enterobacteriaceae were only detected in vegetated samples and samples containing bird droppings. The human pathogens Salmonella, Campylobacter and Listeria were not in any sample. Both thermophilic bacteria and archaea 16S rDNA sequences were found in the subsurface samples collected at 145 and 172 m depth at 80 and 54 °C, respectively, but no growth was observed in enrichments. The microbiota sequences generally showed low affiliation to any known 16S rRNA gene sequences.

  18. Microbial colonisation in diverse surface soil types in Surtsey and diversity analysis of its subsurface microbiota (United States)

    Marteinsson, V.; Klonowski, A.; Reynisson, E.; Vannier, P.; Sigurdsson, B. D.; Ólafsson, M.


    Colonisation of life on Surtsey has been observed systematically since the formation of the island 50 years ago. Although the first colonisers were prokaryotes, such as bacteria and blue-green algae, most studies have been focusing on settlement of plants and animals but less on microbial succession. To explore microbial colonization in diverse soils and the influence of associate vegetation and birds on numbers of environmental bacteria, we collected 45 samples from different soils types on the surface of the island. Total viable bacterial counts were performed with plate count at 22, 30 and 37 °C for all soils samples and the amount of organic matter and nitrogen (N) was measured. Selected samples were also tested for coliforms, faecal coliforms aerobic and anaerobic bacteria. The deep subsurface biosphere was investigated by collecting liquid subsurface samples from a 182 m borehole with a special sampler. Diversity analysis of uncultivated biota in samples was performed by 16S rRNA gene sequences analysis and cultivation. Correlation was observed between N deficits and the number of microorganisms in surface soils samples. The lowest number of bacteria (1 × 104-1 × 105 g-1) was detected in almost pure pumice but the count was significant higher (1 × 106-1 × 109 g-1) in vegetated soil or pumice with bird droppings. The number of faecal bacteria correlated also to the total number of bacteria and type of soil. Bacteria belonging to Enterobacteriaceae were only detected in vegetated and samples containing bird droppings. The human pathogens Salmonella, Campylobacter and Listeria were not in any sample. Both thermophilic bacteria and archaea 16S rDNA sequences were found in the subsurface samples collected at 145 m and 172 m depth at 80 °C and 54 °C, respectively, but no growth was observed in enrichments. The microbiota sequences generally showed low affiliation to any known 16S rRNA gene sequences.

  19. Remnant colloform pyrite at the haile gold deposit, South Carolina: A textural key to genesis (United States)

    Foley, N.; Ayuso, R.A.; Seal, R.R.


    Auriferous iron sulfide-bearing deposits of the Carolina slate belt have distinctive mineralogical and textural features-traits that provide a basis to construct models of ore deposition. Our identification of paragenetically early types of pyrite, especially remnant colloform, crustiform, and layered growth textures of pyrite containing electrum and pyrrhotite, establishes unequivocally that gold mineralization was coeval with deposition of host rocks and not solely related to Paleozoic tectonic events. Ore horizons at the Haile deposit, South Carolina, contain many remnants of early pyrite: (1) fine-grained cubic pyrite disseminated along bedding; (2) fine- grained spongy, rounded masses of pyrite that may envelop or drape over pyrite cubes; (3) fragments of botryoidally and crustiform layered pyrite, and (4) pyritic infilling of vesicles and pumice. Detailed mineral chemistry by petrography, microprobe, SEM, and EDS analysis of replaced pumice and colloform structures containing both arsenic compositional banding and electrum points to coeval deposition of gold and the volcanic host rocks and, thus, confirms a syngenetic origin for the gold deposits. Early pyrite textures are present in other major deposits of the Carolina slate belt, such as Ridgeway and Barite Hill, and these provide strong evidence for models whereby the sulfide ores formed prior to tectonism. The role of Paleozoic metamorphism was to remobilize and concentrate gold and other minerals in structurally prepared sites. Recognizing the significance of paragenetically early pyrite and gold textures can play an important role in distinguishing sulfide ores that form in volcanic and sedimentary environments from those formed solely by metamorphic processes. Exploration strategies applied to the Carolina slate belt and correlative rocks in the eastern United States in the Avalonian basement will benefit from using syngenetic models for gold mineralization.

  20. Exposed Dentin: Influence of Cleaning Procedures and Simulated Pulpal Pressure on Bond Strength of a Universal Adhesive System (United States)


    Purpose To compare various pre-treatments serving as cleaning procedures of dentin on the bond strength of resin composite promoted by a universal adhesive system applied either in the absence or presence of simulated pulpal pressure. Materials and Methods Prior to application of the adhesive system (Scotchbond Universal) and resin composite (Filtek Z250), ground dentin surfaces were given one of five pre-treatments either without or with simulated pulpal pressure: 1) no pre-treatment, adhesive system in “self-etch” mode, 2) phosphoric acid etching, adhesive system in “total-etch” mode, 3) polishing with pumice on prophylaxis cup, 4) air abrasion with AIR-FLOW PLUS powder, 5) air abrasion with AIR-FLOW PERIO powder; n = 20/group of pre-treatment. After storage (37°C, 100% humidity, 24 h), micro shear bond strength was measured and data analyzed with parametric ANOVA including Bonferroni-Holm correction for multiple testing followed by Student’s t tests (significance level: α = 0.05). Results The ANOVA found type of pre-treatment and simulated pulpal pressure to have no significant effect on dentin bond strength. The explorative post-hoc tests showed a negative effect of simulated pulpal pressure for phosphoric acid etching (adhesive system in “total-etch” mode; p = 0.020), but not for the other four pre-treatments (all p = 1.000). Conclusion Air abrasion with powders containing either erythritol and chlorhexidine (AIR-FLOW PLUS) or glycine (AIR-FLOW PERIO) yielded dentin bond strengths similar to no pre-treatment, phosphoric acid etching, or polishing with pumice. Simulated pulpal pressure reduced the bond strength only when the self-etch adhesive system was used in total-etch mode. PMID:28081572

  1. Igneous rocks identification on well-log data; Classificacao de rochas igneas em perfis eletricos

    Energy Technology Data Exchange (ETDEWEB)

    Souza-Lima, Wagner [PETROBRAS S.A., Salvador, BA (Brazil). Unidade de Negocio de Exploracao e Producao de Sergipe e Alagoas. Ativo de Exploracao], E-mail:; Pinho, Gustavo de Carvalho; Silva, Patricia Martins; Paraizo, Paulo Lopes Brandao


    An attempt to discriminate and characterise igneous rocks on well-log data is made in a well drilled on the Cabo Sub-basin (JG-1 well, Sergipe- Alagoas Basin), situated on the northeastern coast of Brazil. Log data from the twelve drilled igneous intervals were analysed on RHOBxPHIN and DTxGRxResistivity cross plots. Similar diagrams were constructed for igneous data from the 1-CPE-1-PE well, drilled on the same basin, and with igneous data from other Brazilian basins. At the RHOBxPHIN cross plot, twelve lithologic fields were discriminated, and their characteristics verified against petrographic data. Two trends are perceptible: the basic rocks set (olivine-basalt, andesite, basaltic pumice and basaltic andesite) distributed along the dolomite line, and the acid rocks set (trachyandesite/quartz-latite, trachyandesite, trachyte, olivine-trachyandesite and acid pumice) coincident with the calcite line. At the DTxGRxResistivity cross plot, the basic set occurs around low-GR field, and the acid set is distributed around high-GR field. The JG-1 well's log data were submitted to discriminant analysis, and the results were checked against the CPE-1 well's curves, for validation. For the first well, the hits ranged from 82 and 100%. For the second well, a perfect lithologic identification was obtained, except for those cases where the lithotypes does not exist in the JG-1 well. One of the main applications for this technique is the stratigraphic correlation for the volcanic successions from sedimentary basins, mainly in the absence of good biostratigraphic markers. (author)

  2. The eruptive history and magmatic evolution of Aluto volcano: new insights into silicic peralkaline volcanism in the Ethiopian rift (United States)

    Hutchison, William; Pyle, David M.; Mather, Tamsin A.; Yirgu, Gezahegn; Biggs, Juliet; Cohen, Benjamin E.; Barfod, Dan N.; Lewi, Elias


    The silicic peralkaline volcanoes of the East African Rift are some of the least studied volcanoes on Earth. Here we bring together new constraints from fieldwork, remote sensing, geochronology and geochemistry to present the first detailed account of the eruptive history of Aluto, a restless silicic volcano located in a densely populated section of the Main Ethiopian Rift. Prior to the growth of the Aluto volcanic complex (before 500 ka) the region was characterized by a significant period of fault development and mafic fissure eruptions. The earliest volcanism at Aluto built up a trachytic complex over 8 km in diameter. Aluto then underwent large-volume ignimbrite eruptions at 316 ± 19 ka and 306 ± 12 ka developing a 42 km2 collapse structure. After a hiatus of 250 ka, a phase of post-caldera volcanism initiated at 55 ± 19 ka and the most recent eruption of Aluto has a radiocarbon age of 0.40 ± 0.05 cal. ka BP. During this post-caldera phase highly-evolved peralkaline rhyolite lavas, ignimbrites and pumice fall deposits have erupted from vents across the complex. Geochemical modelling is consistent with rhyolite genesis from protracted fractionation (> 80%) of basalt that is compositionally similar to rift-related basalts found east of the complex. Based on the style and volume of recent eruptions we suggest that silicic eruptions occur at an average rate of 1 per 1000 years, and that future eruptions of Aluto will involve explosive emplacement of localised pumice cones and effusive obsidian coulees of volumes in the range 1-100 × 106 m3.

  3. Analisis stratigrafi awal kegiatan Gunung Api Gajahdangak di daerah Bulu, Sukoharjo; Implikasinya terhadap stratigrafi batuan gunung api di Pegunungan Selatan, Jawa Tengah

    Directory of Open Access Journals (Sweden)

    Hill Gendoet Hartono


    Full Text Available, Tertiary volcanisms in the Southern Mountains, Central Jawa were started with the formation of pillow lavas having basalt to basaltic andesite in composition. This initial stage volcanism developed into a  construction period of composite volcanoes that consist of alternating basaltic to andesitic lava flows, breccias, and tuffs. The construction period could be followed by a destructive phase, producing pumice-rich pyroclastic breccias, lapillistones, and tuffs of high silica andesite to dacite, or even rhyolite in composition. A stratigraphic measuring section at Bulu area, Sukoharjo Regency, presents an alternat- ing fine-grained andesitic volcaniclastic material and some limestones, with the total thickness is 143.33 m. The thickness of bedded volcaniclastic material tends to be thickening upward from 35 m until 90 m. The grain size of the volcaniclastic material also tends to be coarsening upward from clay size through silt and fine sand to coarse sand and granules. Paleontological analysis on fossils contained in the lime- stone gives an age of Early Miocene (N7 - N9. The volcaniclastic rocks is conformably overlain by the Mandalika Formation, comprising alternating andesitic breccias, lavas, and tuffs. These data imply that the fine-grained volcaniclastic material is an initial product of the construction period of Gajahdangak Volcano in the area, that formed the Mandalika Formation. This Formation is overlain by the Semilir Formation, composed of pumice-rich pyroclastic breccias and tuffs with dacitic composition. This as- sociated volcanic rock reflects a product of a caldera explosion or a destructive phase. Based on the characteristics of lithology of volcanic products from the initial stage, to a construction and destruction period, and compiled age data, the Southern Mountains represent formal volcanic rock units that are able to be divided into many formations.  

  4. Primary and secondary fragmentation of crystal-bearing intermediate magma (United States)

    Jones, Thomas J.; McNamara, Keri; Eychenne, Julia; Rust, Alison C.; Cashman, Katharine V.; Scheu, Bettina; Edwards, Robyn


    Crystal-rich intermediate magmas are subjected to both primary and secondary fragmentation processes, each of which may produce texturally distinct tephra. Of particular interest for volcanic hazards is the extent to which each process contributes ash to volcanic plumes. One way to address this question is by fragmenting pyroclasts under controlled conditions. We fragmented pumice samples from Soufriere Hills Volcano (SHV), Montserrat, by three methods: rapid decompression in a shock tube-like apparatus, impact by a falling piston, and milling in a ball mill. Grain size distributions of the products reveal that all three mechanisms produce fractal breakage patterns, and that the fractal dimension increases from a minimum of 2.1 for decompression fragmentation (primary fragmentation) to a maximum of 2.7 by repeated impact (secondary fragmentation). To assess the details of the fragmentation process, we quantified the shape, texture and components of constituent ash particles. Ash shape analysis shows that the axial ratio increases during milling and that particle convexity increases with repeated impacts. We also quantify the extent to which the matrix is separated from the crystals, which shows that secondary processes efficiently remove adhering matrix from crystals, particularly during milling (abrasion). Furthermore, measurements of crystal size distributions before (using x-ray computed tomography) and after (by componentry of individual grain size classes) decompression-driven fragmentation show not only that crystals influence particular size fractions across the total grain size distribution, but also that free crystals are smaller in the fragmented material than in the original pumice clast. Taken together, our results confirm previous work showing both the control of initial texture on the primary fragmentation process and the contributions of secondary processes to ash formation. Critically, however, our extension of previous analyses to characterisation

  5. Analisis stratigrafi awal kegiatan Gunung Api Gajahdangak di daerah Bulu, Sukoharjo; Implikasinya terhadap stratigrafi batuan gunung api di Pegunungan Selatan, Jawa Tengah

    Directory of Open Access Journals (Sweden)

    Hill Gendoet Hartono


    Full Text Available, Tertiary volcanisms in the Southern Mountains, Central Jawa were started with the formation of pillow lavas having basalt to basaltic andesite in composition. This initial stage volcanism developed into a  construction period of composite volcanoes that consist of alternating basaltic to andesitic lava flows, breccias, and tuffs. The construction period could be followed by a destructive phase, producing pumice-rich pyroclastic breccias, lapillistones, and tuffs of high silica andesite to dacite, or even rhyolite in composition. A stratigraphic measuring section at Bulu area, Sukoharjo Regency, presents an alternat- ing fine-grained andesitic volcaniclastic material and some limestones, with the total thickness is 143.33 m. The thickness of bedded volcaniclastic material tends to be thickening upward from 35 m until 90 m. The grain size of the volcaniclastic material also tends to be coarsening upward from clay size through silt and fine sand to coarse sand and granules. Paleontological analysis on fossils contained in the lime- stone gives an age of Early Miocene (N7 - N9. The volcaniclastic rocks is conformably overlain by the Mandalika Formation, comprising alternating andesitic breccias, lavas, and tuffs. These data imply that the fine-grained volcaniclastic material is an initial product of the construction period of Gajahdangak Volcano in the area, that formed the Mandalika Formation. This Formation is overlain by the Semilir Formation, composed of pumice-rich pyroclastic breccias and tuffs with dacitic composition. This as- sociated volcanic rock reflects a product of a caldera explosion or a destructive phase. Based on the characteristics of lithology of volcanic products from the initial stage, to a construction and destruction period, and compiled age data, the Southern Mountains represent formal volcanic rock units that are able to be divided into many formations.  

  6. Identifying the volcanic eruption depicted in a neolithic painting at Catalhoyuk, Central Anatolia, Turkey.

    Directory of Open Access Journals (Sweden)

    Axel K Schmitt

    Full Text Available A mural excavated at the Neolithic Çatalhöyük site (Central Anatolia, Turkey has been interpreted as the oldest known map. Dating to ∼6600 BCE, it putatively depicts an explosive summit eruption of the Hasan Dağı twin-peaks volcano located ∼130 km northeast of Çatalhöyük, and a birds-eye view of a town plan in the foreground. This interpretation, however, has remained controversial not least because independent evidence for a contemporaneous explosive volcanic eruption of Hasan Dağı has been lacking. Here, we document the presence of andesitic pumice veneer on the summit of Hasan Dağı, which we dated using (U-Th/He zircon geochronology. The (U-Th/He zircon eruption age of 8.97±0.64 ka (or 6960±640 BCE; uncertainties 2σ overlaps closely with (14C ages for cultural strata at Çatalhöyük, including level VII containing the "map" mural. A second pumice sample from a surficial deposit near the base of Hasan Dağı records an older explosive eruption at 28.9±1.5 ka. U-Th zircon crystallization ages in both samples range from near-eruption to secular equilibrium (>380 ka. Collectively, our results reveal protracted intrusive activity at Hasan Dağı punctuated by explosive venting, and provide the first radiometric ages for a Holocene explosive eruption which was most likely witnessed by humans in the area. Geologic and geochronologic lines of evidence thus support previous interpretations that residents of Çatalhöyük artistically represented an explosive eruption of Hasan Dağı volcano. The magmatic longevity recorded by quasi-continuous zircon crystallization coupled with new evidence for late-Pleistocene and Holocene explosive eruptions implicates Hasan Dağı as a potential volcanic hazard.

  7. New insights into the evolution of the magmatic system of a composite andesite volcano revealed by clasts from distal mass-flow deposits: Ruapehu volcano, New Zealand (United States)

    Tost, M.; Price, R. C.; Cronin, S. J.; Smith, I. E. M.


    Stratovolcanoes characteristically build large composite edifices over long periods with stacked lavas intercalated with pyroclastic deposits. In most cases, only the most recent volcanic products are exposed on the flanks of the volcano, and consequently the search for deposits recording an older eruptive and magmatic history is typically focussed far from the cone, within distal tephra deposits. Clasts within lahar and debris avalanche deposits may also provide unique insights into the earliest eruptive and magmatic history of long-lived volcanoes, especially when widespread fallout is absent. Careful sampling and subsequent petrological and geochemical analyses of lava and pumice clasts from six distal mass-flow deposit sequences (hyperconcentrated flow, debris flows and debris avalanche deposits) from Mt. Ruapehu (New Zealand), combined with detailed stratigraphic studies and radiometric age dating, give new perspectives on the pre-50 ka magmatic system of this complex volcano. A conglomerate emplaced between 340 and 310 ka contains evidence for the oldest episode of Mt. Ruapehu volcanism, and unusually for the composite cone, pumice clasts from this unit contain amphibole-bearing xenoliths. Chemical and petrological data for these oldest Ruapehu clasts indicate that a deep (˜40 km) crustal storage system had already developed under Mt. Ruapehu before ˜340 ka. From the very earliest stages, evolution was largely controlled by magma mixing, along with decoupled assimilation and fractional crystallization within numerous isolated small-scale magma batches stored throughout the crust. From around 340 to 160 ka, there was a progressive shift towards more primitive compositions, suggesting that during this period large-scale replenishment events involving mantle-derived basaltic magmas occurred within the mid- to upper crustal storage system. Subsequent magmas became progressively more evolved due to decoupled fractional crystallization and assimilation processes

  8. Pre-eruptive conditions of dacitic magma erupted during the 21.7 ka Plinian event at Nevado de Toluca volcano, Central Mexico (United States)

    Arce, J. L.; Gardner, J. E.; Macías, J. L.


    The Nevado de Toluca volcano in Central Mexico has been active over the last ca. 42 ka, during which tens of km3 of pyroclastic material were erupted and two important Plinian-type eruptions occurred at ca. 21.7 ka (Lower Toluca Pumice: LTP) and ca. 10.5 ka (Upper Toluca Pumice: UTP). Samples from both the LTP and UTP contain plagioclase, amphibole, iron-titanium oxides, and minor anhedral biotite, set in a vesicular, rhyolitic, glassy matrix. In addition, UTP dacites contain orthopyroxene. Analysis of melt inclusions in plagioclase phenocrysts yields H2O contents of 2-3.5 wt.% for LTP and 1.3-3.6 wt.% for UTP samples. Ilmenite-ulvospinel geothermometry yields an average temperature of ~ 868 °C for the LTP magma (hotter than the UTP magma, ~ 842 °C; Arce et al., 2006), whereas amphibole-plagioclase geothermometry yields a temperature of 825-859 °C for the LTP magma. Water-saturated experiments using LTP dacite suggest that: (i) amphibole is stable above 100 MPa and below 900 °C; (ii) plagioclase crystallizes below 250-100 MPa at temperatures of 850-900 °C; and (iii) pyroxene is stable only below pressures of 200-100 MPa and temperatures of 825-900 °C. Comparison of natural and experimental data suggests that the LTP dacitic magma was stored at 150-200 MPa (5.8-7.7 km below the volcano summit). No differences in pressure found between 21.7 ka and 10.5 ka suggest that these two magmas were stored at similar depths. Orthopyroxene produced in lower temperature LTP experiments is compositionally different to those found in UTP natural samples, suggesting that they originated in two different magma batches. Whole-rock chemistry, petrographic features, and mineral compositions suggest that magma mixing was responsible for the generation of the dacitic Plinian LTP eruption.

  9. Shallow conduit processes during the ad 1158 explosive eruption of Hekla volcano, Iceland (United States)

    Janebo, Maria H.; Houghton, Bruce F.; Thordarson, Thorvaldur; Larsen, Gudrun


    Hekla is one of the most frequently active felsic volcanic systems in the world, with several known pre-historic large Plinian eruptions and 18 historical subplinian to small Plinian eruptions. A common view is that Plinian eruptions of Hekla are relatively short lived and purely explosive events. In detail, these events exhibit subtle differences in terms of deposit characteristics, reflecting significant differences in eruption behaviour. Of the 18 historical eruptions, two had bulk magma compositions with >66 wt% SiO2: a Plinian eruption in ad 1104 and a smaller, less well characterised, but atypical subplinian eruption in ad 1158. The ad 1158 eruption was a relatively sustained, dry (magmatic) eruption with a more powerful opening phase followed by a lower intensity, waning phase accompanied by minor destabilisation and collapse of the conduit walls. We examine here the dynamics of the ad 1158 eruption, focussing on the role of shallow conduit processes in modulating eruption dynamics. Vesicularity data constrain the relative influence of bubble nucleation, growth, and coalescence. The juvenile pyroclasts are composed of two types of microvesicular pumice (white and grey) with contrasting vesicle number density, vesicle-size distribution, and phenocryst and microlite contents. Textural analysis shows that these pumices reflect heterogeneity developed pre- to syn-eruptively in the conduit and that entrainment of longer resident magma by faster ascending magma permitted magma of contrasting maturity to be fragmented simultaneously. In this regard, the mixed melt of the ad 1158 eruption contrasts with the compositionally homogeneous melt phase of the more powerful ad 1104 Plinian event, which was typified by more uniform conduit and eruption dynamics accompanying higher average ascent rates.

  10. Stromboli volcano (Aeolian Archipelago, Italy): An open window on the deep-feeding system of a steady state basaltic volcano (United States)

    Bertagnini, A.; MéTrich, N.; Landi, P.; Rosi, M.


    Paroxysms at Stromboli are the most violent manifestations of the persistent activity and are related to the emission of small volumes (103-105 m3) of nearly aphyric HK-basaltic pumices. They offer the exceptional opportunity to detail the mixing-crystallization-degassing processes that occur in a steady state basaltic arc volcano. We present mineralogy, major, volatile, and trace element geochemistry of olivine-hosted melt inclusions of these pumices. In all the paroxysms, melt inclusions hosted in olivines Fo88-91 have recorded the parental melts rich in CaO (up to 14.5 wt %) but low in FeO (6-7 wt %). They demonstrate recurrent variations in the K2O content (1.6-1.3 wt %) and S/Cl ratios (1.2-0.8) of the melts that entered the deep system. Dynamic magma mixing between melts slightly distinct by their degree of evolution, rapid crystallization, and entrapment of gas-oversaturated melts during decompression are indicated by (1) the high density of irregular, clear melt inclusions, and embayments in homogeneous olivines (Fo87±0.5-Fo83±0.5), (2) the variable ratio between melt and gas bubble, and (3) the variability of melt inclusion compositions in both major (CaO/Al2O3 = 1-0.59) and volatile (3.4-1.8 wt % H2O, 1582-1017 ppm CO2) elements. FeO-rich melt inclusions in patchy, reversely zoned olivines also demonstrate interactions between ascending melt blobs and inherited olivine crystals. We propose a model involving a vertically extended dike-like system, where magmas progress and differentiate. On the basis of olivine growth rate calculations the volatile-rich magma blobs may ascend within few hours to few tenths of hours. Finally, we propose that sulfur degassing is possibly initiated during the early stage of magma differentiation.

  11. Transport and deposition of pyroclastic material from the ˜1000 A.D. caldera-forming eruption of Volcán Ceboruco, Nayarit, Mexico (United States)

    Browne, B. L.; Gardner, J. E.


    The complex eruption sequence from the ˜1000 A.D. caldera-forming eruption of Volcán Ceboruco, known as the Jala Pumice, offers an exceptional opportunity to examine how pyroclastic material is transported and deposited from pyroclastic density currents over variable topography. Three main pyroclastic surge deposits (S1, S2, and S3) and two pyroclastic flow deposits (Marquesado and North-Flank PFDs) were emplaced during this eruption. Pyroclastic surge deposits are massive, planar, or cross-bedded, poor-to-well sorted, and display fluctuations in thickness, median diameter, sorting, and lithology as a function of distance, topography, and flow dynamics. Marquesado pyroclastic flow deposits reveal lateral variations from massive, poorly sorted deposits located within 5 km of Ceboruco to planar bedded, moderately well sorted deposits located >15 km away over the nearly horizontal topography to the south of Ceboruco. North-Flank pyroclastic flow deposits also reveal lateral variations from massive, poorly sorted deposits located within 4 km of Ceboruco to planar bedded, moderately well sorted deposits located 8 km away atop an escarpment that steeply rises 230 m from the northern valley floor. Field observations, granulometric analyses, component analyses, and crystal sedimentation calculations along flow-parallel sampling transects all suggest that both surges and flows were density stratified currents, where deposition occurred from a basal region of higher particle concentration that was supplied from an overlying dilute layer that transports particles in suspension. This supports the idea of a transition between “flow” and “surge” end members with variations in particle concentration. Topography greatly affects the transport and depositional capacity of the pyroclastic density currents as a result of “blocking”, either by topographic obstacles or by abrupt breaks at the base of volcano slopes, whereas the origin of Jala Pumice surge deposits

  12. Identifying the Volcanic Eruption Depicted in a Neolithic Painting at Çatalhöyük, Central Anatolia, Turkey (United States)

    Schmitt, Axel K.; Danišík, Martin; Aydar, Erkan; Şen, Erdal; Ulusoy, İnan; Lovera, Oscar M.


    A mural excavated at the Neolithic Çatalhöyük site (Central Anatolia, Turkey) has been interpreted as the oldest known map. Dating to ∼6600 BCE, it putatively depicts an explosive summit eruption of the Hasan Dağı twin-peaks volcano located ∼130 km northeast of Çatalhöyük, and a birds-eye view of a town plan in the foreground. This interpretation, however, has remained controversial not least because independent evidence for a contemporaneous explosive volcanic eruption of Hasan Dağı has been lacking. Here, we document the presence of andesitic pumice veneer on the summit of Hasan Dağı, which we dated using (U-Th)/He zircon geochronology. The (U-Th)/He zircon eruption age of 8.97±0.64 ka (or 6960±640 BCE; uncertainties 2σ) overlaps closely with 14C ages for cultural strata at Çatalhöyük, including level VII containing the “map” mural. A second pumice sample from a surficial deposit near the base of Hasan Dağı records an older explosive eruption at 28.9±1.5 ka. U-Th zircon crystallization ages in both samples range from near-eruption to secular equilibrium (>380 ka). Collectively, our results reveal protracted intrusive activity at Hasan Dağı punctuated by explosive venting, and provide the first radiometric ages for a Holocene explosive eruption which was most likely witnessed by humans in the area. Geologic and geochronologic lines of evidence thus support previous interpretations that residents of Çatalhöyük artistically represented an explosive eruption of Hasan Dağı volcano. The magmatic longevity recorded by quasi-continuous zircon crystallization coupled with new evidence for late-Pleistocene and Holocene explosive eruptions implicates Hasan Dağı as a potential volcanic hazard. PMID:24416270

  13. Source of the great A.D. 1257 mystery eruption unveiled, Samalas volcano, Rinjani Volcanic Complex, Indonesia. (United States)

    Lavigne, Franck; Degeai, Jean-Philippe; Komorowski, Jean-Christophe; Guillet, Sébastien; Robert, Vincent; Lahitte, Pierre; Oppenheimer, Clive; Stoffel, Markus; Vidal, Céline M; Surono; Pratomo, Indyo; Wassmer, Patrick; Hajdas, Irka; Hadmoko, Danang Sri; de Belizal, Edouard


    Polar ice core records attest to a colossal volcanic eruption that took place ca. A.D. 1257 or 1258, most probably in the tropics. Estimates based on sulfate deposition in these records suggest that it yielded the largest volcanic sulfur release to the stratosphere of the past 7,000 y. Tree rings, medieval chronicles, and computational models corroborate the expected worldwide atmospheric and climatic effects of this eruption. However, until now there has been no convincing candidate for the mid-13th century "mystery eruption." Drawing upon compelling evidence from stratigraphic and geomorphic data, physical volcanology, radiocarbon dating, tephra geochemistry, and chronicles, we argue the source of this long-sought eruption is the Samalas volcano, adjacent to Mount Rinjani on Lombok Island, Indonesia. At least 40 km(3) (dense-rock equivalent) of tephra were deposited and the eruption column reached an altitude of up to 43 km. Three principal pumice fallout deposits mantle the region and thick pyroclastic flow deposits are found at the coast, 25 km from source. With an estimated magnitude of 7, this event ranks among the largest Holocene explosive eruptions. Radiocarbon dates on charcoal are consistent with a mid-13th century eruption. In addition, glass geochemistry of the associated pumice deposits matches that of shards found in both Arctic and Antarctic ice cores, providing compelling evidence to link the prominent A.D. 1258/1259 ice core sulfate spike to Samalas. We further constrain the timing of the mystery eruption based on tephra dispersal and historical records, suggesting it occurred between May and October A.D. 1257.

  14. The compositionally zoned eruption of 1912 in the Valley of Ten Thousand Smokes, Katmai National Park, Alaska (United States)

    Hildreth, Wes


    On June 6-8, 1912, ˜ 15 km 3 of magma erupted from the Novarupta caldera at the head of the Valley of Ten Thousand Smokes (VTTS), producing ˜ 20 km 3 of air-fall tephra and 11-15 km 3 of ash-flow tuff within ˜ 60 hours. Three discrete periods of ash-fall at Kodiak correlate, respectively, with Plinian tephra layers designated A, CD, and FG by Curtis (1968) in the VTTS. The ash-flow sequence overlapped with but outlasted pumice fall A, terminating within 20 hours of the initial outbreak and prior to pumice fall C. Layers E and H consist mostly of vitric dust that settled during lulls, and Layer B is the feather edge of the ash flow. The fall units filled and obscured the caldera, but arcuate and radial fissures outline a 6-km 2 depression. The Novarupta lava dome and its ejecta ring were emplaced later within the depression. At Mt. Katmai, 10 km east of the 1912 vent, a 600-m-deep caldera of similar area also collapsed at about this time, probably owing to hydraulic connection with the venting magma system; but all known ejecta are thought to have erupted at Novarupta. Mingling of three distinctive magmas during the eruption produced an abundance of banded pumice, and mechanical mixing of chilled ejecta resulted in deposits with a wide range of bulk composition. Pumice in the initial fall unit (A) is 100% rhyolite, but fall units atop the ash flow are > 98% dacite; black andesitic scoria is common only in the ash flows and in near-vent air-fall tephra. Pumice counts show the first half of the ash-flow deposit to be 91-98% rhyolite, but progressive increases of dacite and andesite eventually reduced the rhyolitic component to 20 km to the lowermost VTTS, and deposited 1-8 m of debris there. Rhyolitic ejecta contain only 1-2% phenocrysts but andesite and dacite have 30-45%. Quartz is present and augite absent only in the rhyolite, but all ejecta contain plagioclase, orthopyroxene, titanomagnetite, ilmenite, apatite, and pyrrhotite; rare olivine occurs in the

  15. A multidisciplinary approach for high-resolution reconstruction of the eruptive past of La Soufrière (Guadeloupe) over the last 12 000 years: Implications for hazards assessment. (United States)

    Legendre, Yoann; Komorowski, Jean-Christophe; Boudon, Georges


    105 new 14C age dates of wood, charcoal, and paleosoil samples that complete the existing 14C database (total of about 261 dates). A multidisciplinary analysis (sedimentology, lithology, microtextures, magnetic susceptibility) of the sediment cores and field data has allowed us to identify hidden, and missing eruptions, and to re-interpret mis-identified eruptions. For the last 12 000 years we have identified at least 5 distinct new pumice fallout deposits, some of which are associated with pumice pyroclastic flow deposits. We also identified several deposits formed by magmatic turbulent pyroclastic density currents (blasts) mostly associated with flank-collapse events. Thus, the number of Holocene magmatic eruptions has significantly increased compared to previous knowledge. More over we have identified eruptive sequences that consist of a diverse range of phenomena including edifice-collapse, associated laterally directed explosions (blasts), pumice fallout with column-collapse and dome growth similar to the AD1530 most recent magmatic eruption. The magmatic eruptive rate could be twice as important with 11-13 magmatic eruptions in 12 000 years, a rate of about 0.92-1.08 magmatic eruption by 1000 years. This new data will allow a better determination of the recurrence, magnitude, intensity, and the spatio-temporal evolution of deposit types that define different eruptive scenarios. Hence, this high-resolution reconstruction of the eruptive past will provide the basis for an improved probabilistic hazard and risk assessment for La Soufrière of Guadeloupe, a dangerous volcano, currently experiencing prolongued unrest since 1992.


    Suarez-Plascencia, C.; Delgado-Argote, L. A.; Nunez-Cornu, F. J.


    The Metropolitan Area of Guadalajara (MAG) was built over pumice deposits generated during Quaternary activity in the Sierra la Primavera, that covered a thick sequence of basaltic, dacitic, rhyolitic lava flows, ignimbrites and fluvial-lacustrine deposits. The most complete stratigraphic section is observed in different sections of the Rio Grande de Santiago cliff, located north of the city. Five distinctive geoforms were identified: 1) the cliff of the Rio Grande de Santiago (CRGS) is a tectonic erosive depression with average depth of 500 m and 3.5 km width. Structurally, in the San Gaspar zone, south of the union of Verde river with Santiago river, we identified normal faults with left-lateral motion and oriented 191°/89° on basaltic lavas. In the Colimilla dam, 1297 meters above sea level, we observed lateral faulting with normal component (267°/81°) where jumps as high as 30 m were observed. Lava flows are sheared parallel to the Verde river. In the Puente Arcediano zone, where the base of the sequence is apparent, faults have a dominant orientation of 188°/75° on andesitic flows, whereas on pumice ignimbrites they show a shearing with a direction of 92°/84° parallel to the Verde river. 2) The Sierra la Primavera, to the southwest of MAG is a caldera formed by a series of domes, flows, and pyroclastic deposits with rhyolitic composition. 3) The southern Guadalajara volcanic chain system, which is formed by several volcanic cones and flows of basaltic-andesitic composition and Plio-Pleistocene age, oriented NW-SE, developed over the San Gaspar ignimbrite (4.8 m.a.). 4) Los Colomos and Alcalde-Barranquitas cliff system, which form dendrite networks developed on pumice deposits, where most of the cliffs were deep and narrow. The origin of the cliffs might be associated with observed faults or fracture zones in the CRGS. 5) Wavy plains of Atemajac and Tesistán valleys, which are characterized by hills and wide plains. The system of cliffs controlled the

  17. A decadal view of magma fragmentation (United States)

    Cashman, K. V.; Rust, A.


    Although the past decade has seen fundamental advances in studies of explosive volcanism, the disruption to air traffic caused by the 2010 eruption of Eyjafjallajökull, Iceland, highlights the need for improved understanding of magmatic fragmentation in general, and of fine ash generation in particular. To develop a theoretical basis for predicting the fine ash content of eruptive plumes, we need to understand not only fragmentation mechanisms but also the dependence of those mechanisms on conditions of magma ascent and degassing. Experimental and analytical approaches to this problem include experimental studies of vesiculation and permeability development in silicic melts, quantitative textural studies of pyroclasts to constrain conditions that reduce fragmentation efficiency (that is, allow vesicular clasts to be preserved), direct experiments on fragmentation in both natural and analog materials, and determination of total grain size distributions (TGSDs) of pyroclastic deposits. Experiments on silicic melts have demonstrated that very high supersaturations (overpressures ΔP) may be achieved in silicic melts prior to homogeneous bubble nucleation, and that the high bubble number densities of silicic pumice require not only homogeneous nucleation but also nucleation of a mixed H2O-CO2 gas phase. In most pumice and scoria clasts, resulting vesicle populations form power law size distributions; power law exponents >3 in silicic tephras indicate that small vesicles comprise most of the vesicle volume (consistent with rapid late-stage vesiculation at high ΔP), while exponents 60-70%) and show no dependence on either melt composition or mass eruption rate; this suggests that melt porosity is more important than either decompression rate or magma rheology for clast preservation. These pyroclasts also have uniformly high permeabilities, high pore connectivity, and simple porous pathways, all of which suggest that ease of gas escape also contributed to clast

  18. Horizontal and low-angle cross-stratifications from volcaniclastic sedimentary sequences: Outburst flood deposits, Numazawa and Ontake volcanoes, Japan (United States)

    Kataoka, Kyoko


    This talk focuses on the formation and preservation of sedimentary structures such as horizontal and low-angle cross-stratifications in volcaniclastic sedimentary (lahar) sequences. The 5 ka outburst flood deposits in the Tadami river catchment, Numazawa volcano, Japan is presented as a first example. The flood, with a peak discharge of > 37,000-58,000 m^3/s from ignimbrite-dammed valley left pumiceous gravelly sediments with meter-sized boulders in the flow path (Kataoka et al., 2008). Up to 30 m thick sequence attributed to the flood formed a low gradient fan of 10 km long and 1.5-3 km wide, covering an area of 18 km2 with a total volume of > 0.5 km3 at the downstream end of the Tadami River. Outcrop observations accompanied with extensive surveys of Ground Penetrating Radar (GPR) along 200 to 500 m lateral and longitudinal transects over the flood fan revealed bedforms of the deposits. The profiles show large internal cross structures with 2-5 m amplitude and 10s m wavelength indicating lateral/downstream accretion in flood fan deposits. Some of them are slightly inclined towards upstream (backsets) which may suggest upstream migration of bedforms. These cross stratifications in the GPR profiles correspond to low-angle cross-stratifications or horizontal stratifications observed in outcrops. In outcrops, the stratified flood deposits mainly comprises rounded pumice pebble and cobble gravel and sand sized mineral grains. Bedding structures include horizontal stratifications and low-angle, low-amplitude, long wavelength cross-stratifications that occasionally climb. Individual 5 cm to decimeters-thick bed sets are commonly inversely graded. The deposits imply 1) high sediment concentration within a flow and 2) aggradation and bedform migration occurred in relation with traction carpet sedimentation. Especially thick traction carpets were probably formed because of 1) high stream power to drive near bed layer deeper and 2) a density contrast among volcaniclastic

  19. Rifting, volcanism, and magma genesis at the northern end of the Danakil Depression: The Alid volcanic center of Eritrea (Invited) (United States)

    Lowenstern, J. B.; Clynne, M. A.; Duffield, W. A.; Smith, J. G.; Woldegiorgis, L.


    The Alid volcanic center, Eritrea, is a structural dome formed by subvolcanic intrusion of pyroxene-bearing rhyolite, subsequently erupted as pumice and lava, during the period 40,000 to 15,000 years ago. The northern Danakil Depression is thought to be the most recently developed part of the Afar, and represents an active continental rift subparallel to the Red Sea spreading center. The location of Alid may be controlled by the intersection of the structural grain of the NE trending Senafe-Alid lineament with the NW trending Danakil Depression. Our work began as a geothermal assessment (Duffield et al., 1997, USGS Open-file 97-291) that found evidence for 300 meters of vertical offset of early Pleistocene basalt flows over the past 1.1 million years. Structural uplift at Alid reveals Proterozoic metamorphic basement rocks overlain by Quaternary marine sediments including siltstone, and sandstones interbedded with pillow lavas and hyaloclastites. These units are overlain by subaerial amphibole-bearing rhyolites (dated at ~200 ka), basalts, and andesites that were deposited on a relatively flat surface and before significant growth of a large volcanic edifice. About 1 km of structural uplift of the marine sediments began 40 ka when pyroxene-bearing rhyolitic magma intruded close to the surface. Uplift was accompanied by contemporaneous eruptions of pumice falls and more common obsidian domes and lava flows over the next 20,000 years. Uplift apparently ceased after eruption of pyroclastic flows and vent-clogging lava about 15 ka. The pumice deposits contain cognate xenoliths of granophyric pyroxene-granite (Lowenstern et al., 1997, J. Petrol. 38:1707). Our geochronology of the uplift is consistent with the idea that growth of the Alid volcanic center played a role in isolating the southern Danakil Depression from the Red Sea, helping to initiate dessication of the rift and producing the young evaporites found today at Baddha and further south at Dallol. U

  20. The c.2030 yr BP Plinian eruption of El Misti volcano, Peru: Eruption dynamics and hazard implications (United States)

    Cobeñas, Gisela; Thouret, Jean-Claude; Bonadonna, Costanza; Boivin, Pierre


    'El Misti' volcano near the city of Arequipa in south Peru produced a Plinian eruption c.2030 yr BP that resulted in a tephra deposit consisting of three fallout layers, several pyroclastic density current (PDC) deposits, a late stage, small debris-avalanche deposit, and lahar deposits. This VEI 4 Plinian eruption of El Misti has been selected as one of the reference eruptions for the hazard assessment and risk mitigation plan for the city of Arequipa. The Plinian column of this eruption rose up to 21-24 km and produced a tephra deposit over an area of at least 2580 km2 within the 5 cm-isopach line. The dispersal axis is oriented SW, i.e. towards the area of the basin and city of Arequipa. Later pumice- and lithic-rich PDC deposits were emplaced into radial valleys extending from the volcano up to a distance of at least 13 km. The eruption produced a minimum total bulk volume of 1.2 km3 (0.71 km3 DRE volume) of tephra and PDC deposits. Components of the tephra deposit consist of beige, gray and banded pumices, lithic fragments, a minor amount of cogenetic dacite clasts, and free crystals. The minimum volume of the tephra deposit varies between 0.2 and 0.6 km3 (exponential, power-law integration and inversion of TEPHRA2 analytical model). The tephra deposit is characterized by a bulk density of 1500 kg/m3 which results in a mass of 2.5-9.0 × 1011 kg. The maximum mass discharge rate (MDR) is 1.1 × 108 kg/s based on a plume height of 24 km. The estimated duration of the Plinian eruption ranges between 0.6 and 2.3 h. Grain size distribution, componentry, and SEM analyses of both the tephra and PDC deposits, combined with the reconstructed stratigraphic sequence of the deposit, suggest that the eruption took place in five stages: (1) generation of a 21-24 km-high eruptive column that deposited the lower tephra layer; (2) collapse of the crater walls and partial obstruction of the vent during a period of decreased intensity, which led to the formation of a thin sand

  1. Le Pico de Orizaba (Mexique): Structure et evolution d'un grand volcan andesitique complexe (United States)

    Robin, C.; Cantagrel, J. M.


    Volcan Pico de Orizaba, which marks the eastern end of the Trans-Mexican Volcanic Belt, is one of the largest andesitic composite volcanoes in America. It is located above a series of crustal distensive faults making the boundary of the Coast Plains of the Gulf of Mexico from the Altiplano. For this reason, the volcano shows an asymmetry: from the west, its elevation is about 3,000 m whereas on the eastern side it reaches 4,000 to 4,500 m from its base. The Pico de Orizaba is composed of a primitive stratovolcano raised by a recent summit cone. It has been built by three very distinct volcanic and magmatic phases. 1. The first one, probably discontinuous effusive activity, lasted more than one million years. It is mainly composed of two pyroxenes-andesites with scarce associated basaltic and dacitic lava-flows. Amphibole is an accessory mineral in most differentiated lavas. On the eastern flank, numerous massive and autobrecciated lava-flows pass outward into thick conglomeratic formations. This effusive phase has built a primitive central volcano and a parasitic cone: the Sierra Negra. 2. The second phase is of short duration — about 100,000 years or less — in comparison with the first period. It seems that this period began with the formation of a caldera followed by the extrusion of amphibole dacite domes and the overflow of viscous silica-rich (andesite to dacite) lava flows on the northern flank. An intense explosive activity develops: pelean nuées ardentes are associated with extrusion of the domes; numerous plinian eruptions leading to widespread dacitic pumiceous air-falls are produced by both the central and the adventive volcanoes. This sequence of events is interpreted as the progressive emptying of a superficial chamber containing differenciated magma. A rhyolite flow erupted during this phase. 3. The age of the recent phase is better defined. It started 13,000 years B.P. with the eruption of a dacitic ash-flow containing pumice and scoria

  2. Impact of the AD 79 explosive eruption on Pompeii, I. Relations amongst the depositional mechanisms of the pyroclastic products, the framework of the buildings and the associated destructive events (United States)

    Luongo, Giuseppe; Perrotta, Annamaria; Scarpati, Claudio


    A quantitative and qualitative evaluation of the damage caused by the products of explosive eruptions to buildings provides an excellent contribution to the understanding of the various eruptive processes during such dramatic events. To this end, the impact of the products of the two main phases (pumice fallout and pyroclastic density currents) of the Vesuvius AD 79 explosive eruption onto the Pompeii buildings has been evaluated. Based on different sources of data, such as photographs and documents referring to the archaeological excavations of Pompeii, the stratigraphy of the pyroclastic deposits, and in situ inspection of the damage suffered by the buildings, the present study has enabled the reconstruction of the events that occurred inside the city when the eruption was in progress. In particular, we present new data related to the C.J. Polibius' house, a large building located inside Pompeii. From a comparison of all of the above data sets, it has been possible to reconstruct, in considerable detail, the stratigraphy of the pyroclastic deposits accumulated in the city, to understand the direction of collapse of the destroyed walls, and to evaluate the stratigraphic level at which the walls collapsed. Finally, the distribution and style of the damage allow us to discuss how the emplacement mechanisms of the pyroclastic currents are influenced by their interaction with the urban centre. All the data suggest that both structure and shape of the town buildings affected the transport and deposition of the erupted products. For instance, sloping roofs 'drained' a huge amount of fall pumice into the 'impluvia' (a rectangular basin in the centre of the hall with the function to collect the rain water coming from a hole in the centre of the roof), thus producing anomalous deposit thicknesses. On the other hand, flat and low-sloping roofs collapsed under the weight of the pyroclastic material produced during the first phase of the eruption (pumice fall). In addition

  3. Comparison of the terminal fall velocity, surface roughness and erosion threshold for volcanic particles. (United States)

    Douillet, G. A.; Seybold, L.; Rasmussen, K. R.; Kueppers, U.,; Lo Castro, D.; Dingwell, D. B.


    Pyroclasts are particles emitted during explosive volcanic eruptions. They exhibit highly variable porosities, shapes, and densities. As such, their behaviors differ from the wind-blown and fluvial sand usually studied in clastic sedimentology. In order to better constrain the specificities of pyroclastic material, and gain insights into the flow and depositional processes within dilute pyroclastic density currents, the terminal fall velocity was experimentally measured in air and compared to surface roughness and saltation threshold data obtained from wind tunnel experiments as well as with shape parameters. Two types of particles were investigated (scoriaceous material and pumices), as well as different grain sizes (0.125-4mm for scoria and 0.125-16mm for pumices in half phi fractions). The terminal fall velocity corresponds to the velocity for which the drag exerted by air on a particle counteracts its weight, so that acceleration becomes null and the velocity constant. In order to measure the terminal fall velocity, particles were dropped in a closed and large vertical tube (to avoid any perturbation by air movement present in the lab) and the velocity derived from high speed video recorded near the bottom of the tube. By repeating the experiments from different heights, the velocity was seen to increase with increasing drop-height, until reaching a constant value, taken as the terminal fall velocity. The surface roughness is a value that defines how rough a bed of particles is seen by a wind. The saltation threshold corresponds to the near-bed shear-stress necessary for particles to leave the surface and begin to bounce on the bed. Both are derived from wind profiles experimentally measured in a wind tunnel in Aarhus (Denmark; see abstract 2128). Shape parameters were measured with a Camsizer (from Retsch) in Catania (Italy) and the sphericity, symmetry, aspect ratio, and convexity derived. Since the surface roughness, saltation threshold, and terminal fall

  4. Silicon Isotopic Fractionation in a Tropical Soil-Plant System (United States)

    Opfergelt, S.; Delstanche, S.; Cardinal, D.; Andre, L.; Delvaux, B.


    Silica fluxes to soil solutions and water streams are controlled by both abiotic and biotic processes occurring in a Si soil-plant cycle that can be significant in comparison with Si weathering input and hydrological output. The quantification of Si-isotopic fractionation by these processes is highly promising to study the Si soil-plant cycle. Therein, the fate of aqueous monosilicic acid H4SiO4, as produced by silicate weathering, may take four paths: (1) uptake by plants and recycling through falling litter, (2) formation of clay minerals, (3) specific adsorption onto Al and Fe oxides, (4) leaching in drainage waters and export from watersheds. Here we report on detailed Si-isotopic compositions of various Si pools in a tropical soil-plant system involving old stands of banana (Musa acuminata Colla, cv Grande Naine) cropped on a weathering sequence of soils derived from andesitic volcanic ash and pumice deposits in Cameroon, West Africa. Si-isotopic compositions were measured by MC-ICP-MS in dry plasma mode with external Mg doping with a reproducibility of 0.08 permil (2stdev). Results were expressed as delta29Si vs NBS28. The compositions were determined in plant parts, bulk soils, clay fractions (less than 2um) and stream waters used for crop irrigation. Of the weathering sequence, we selected young (Y) and old (O) volcanic soils (vs). Yvs are rich in weatherable minerals, and contain large amounts of pumice gravels; their clay fraction (10-35 percent) contains allophane, halloysite and ferrihydrite. Oppositely, Ovs are strongly weathered and fine clayey soils (75-96 percent clay) rich in halloysite, kaolinite, gibbsite and goethite. Intra-plant fractionation between roots and shoots and within shoots confirmed our previous data measured on banana plants grown in hydroponics. The bulk plant isotopic composition was heavier at Ovs than at Yvs giving a fractionation factor per atomic mass unit between plants and their irrigation water Si source (+0.61 permil) of

  5. The hydrological response to precipitations of a layered shallow sloping deposit: physical experiments and mathematical modeling (United States)

    Damiano, Emilia; Greco, Roberto; Guida, Andrea; Olivares, Lucio; Picarelli, Luciano


    Although rainfall-induced landslides are frequent, so that they can be probably considered the most widespread natural hazards, fortunately the occurrence of an extreme rainfall event only rarely corresponds to the triggering of landslides. This is due to the fact that slopes, although often considered as separated systems in the stability analyses, are actually part of a larger, more complex hydrological system, with which continuously exchange water. Indeed, most of the slopes do not fail, and when they are subjected to heavy precipitation, effective draining mechanisms spontaneously develop, such as overland and subsurface runoff, and sometimes even new preferential flow paths originated by mechanical processes, such as piping erosion or deformation cracks. Hence, the triggering of a rainfall-induced landslide requires these dynamically evolving (non-linear) drainage processes to be incapable of releasing the excess of water (and pressure) accumulating within the slope. For the case of shallow sloping covers, the capability of the slope to effectively drain the infiltrating water depends on the hydraulic properties of the involved soils (hydraulic conductivity and water retention curves) and on the hydraulic boundary conditions (at the base of the cover, where it lays upon the bedrock, and at the foot of the slope), which are in turn strongly influenced by the initial moisture state (often indicated as a predisposing cause), owing to the non-linearity of the hydraulic processes. Such an already complex picture is furthermore complicated by heterogeneity. In this study, we focus our attention onto the effects of a layered soil cover with contrasting hydraulic properties on the infiltration and drainage processes in a shallow pyroclastic deposit. This is a typical situation along many pyroclastic-covered slopes of Campania (southern Italy), which present alternations of ashes (silty sands) and pumices (sands with gravel) deposited by volcanic eruptions, and where

  6. Long runout mechanism of recent earthquake-triggered landslides in Japan and China (United States)

    Fukuoka, Hiroshi; Wang, Gonghui; Miyagi, Toyohiko; Cui, Peng; Igwe, Ogbonnaya; Georgieva, Ekaterina


    1. Rapid, long runout mechanism on horizontal sliding surface The 2008 Iwate-Miyagi Nairiku Earthquake, Japan of Ms 7.2 caused uncountable landslides in the epicenter area. Largest was the Aratozawa Dam Landslide and its volume is estimated as 70 million cubic meters. It ran rapidly for about 300 m in less than 5 minutes on almost horizontal (1 - 2 degrees) sliding surface. Authors sampled weathered pumice and sand/siltstone from surface of the landslide toe part for ring shear tests and obtained following results; (1) The cyclic loading ring shear test on weathered pumice using observed earthquake main shock acceleration waveform showed limited residual shear displacement. (2) Repeated undrained cyclic loading ring shear tests on saturated siltstone sample finally showed unlimited shear displacement behavior even though the shear stress was as small as about 5 degrees (3) Undrained monotonic loading ring shear test on same pumice proved that the steady state strength is only 30 kPa for shear displacement larger than about 100 mm. Because the steady-state strength is independent of initial normal stress, smallest apparent friction angle of 1 - 2 degrees can be expected. 2. Long runout mechanism of limestone detachment type landslide Many limestone detachment-type landslides have been triggered by the gigantic 2008 Wenchuan Earthquake, China. The Chaping landslides is the largest one and blocked the downslope river to create temporal reservoir, which was, then removed by the army. Authors sampled the landslide debris of crashed limestone near the toe part and conducted ring shear test. The specimen was fully saturated and sheared under undrained condition and constant-shear-speed condition to obtain the long-distance shear behavior. Stress path reached failure at peak friction angle of 41.8 degrees and then went down along the failure line until shear displacement reached about 100 mm. The stress condition stayed the ultimate steady state thereafter. This stress

  7. Late Holocene Eruptions of Mount Rainier, Washington (United States)

    Vallance, J. W.; Sisson, T. W.; Gardner, C. A.; McGeehin, J. P.; Champion, D. E.; Byman, J. A.


    Detailed stratigraphy, more than 20 radiocarbon ages, and paleomagnetic secular variation measurements indicate that eruptions of Mount Rainier clustered in three major periods during the past 3000 years. Products include a plinian fall deposit, several vulcanian falls, several fine ash falls that are associated with block-and-ash flows, and lahars that descended all major drainages that head on the volcano. Tephra layers are of two types: vesicle rich (chiefly pumice lapilli, scoria, and ash) and vesicle poor (chiefly fine-grained glass and lithic fragments). Pumice and glass shards in vesicle-rich deposits are microlite-poor and derive from explosive eruptions. Glass shards in vesicle-poor ashes have variable microlite contents and derive from minor explosions, or from ash clouds that billow up from block-and-ash pyroclastic flows. These findings contrast with those of previous studies that document only two eruptions, each associated with a pumiceous tephra layer, during the last 3000 years. The oldest eruptive period, called Summerland, began after 2700 cal yr BP with a vesicle-poor tephra and a collapse of hydrothermally altered rock on the west flank of the volcano that generated the Round Pass mudflow. Lava flows, fine ash falls and a pyroclastic flow erupted ca 2400 to 2500 cal yr BP. Intermittent eruptions produced more fine-grained ash falls, a possible pyroclastic flow and more lahars, then culminated in the plinian "C" fall to the NE and large lahars that flowed south, southeast, and west about 2200 cal yr BP. The Summerland period ended before 1600 cal yr BP with minor fall deposits and lahars. About 1000 cal yr BP, the Deadman Flat eruptions produced large lahars that contain distinctive prismatically-jointed glassy clasts, interpreted as juvenile components from pyroclastic flows, and co- ignimbrite ash in the headwaters of the White River. The lahars descended valleys to the NE and flowed 100 km to Puget Sound. Aggradation shortly after emplacement

  8. Effect of different prophylaxis methods on sound and demineralized enamel Efeito de diferentes métodos de profilaxia sobre o esmalte hígido e desmineralizado

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    Heitor Marques Honório


    Full Text Available Considering the importance of professional plaque control for caries prevention, this study comprised an in vitro evaluation of wear by two prophylaxis methods (sodium bicarbonate jet - Profident and pumice and brush on sound bovine enamel and with artificial carious lesions. Sixty enamel fragments were employed (4x4mm, which were divided into 4 groups: GI - 15 sound blocks treated with pumice and brush; GII - 15 sound blocks treated with Profident; GIII - 15 demineralized blocks treated with pumice and brush, and GIV - 15 demineralized blocks treated with Profident. In the fragments of Groups III and IV, artificial carious lesions were simulated by immersion in 0.05M acetic acid solution 50% saturated with bovine enamel powder at 37ºC for 16h. The specimens were submitted to the prophylactic treatments for 10 seconds. Wear analysis was performed by profilometer and revealed the following results: 0.91µm - GI; 0.42µm - GII; 1.6µm - GIII, and 0.94µm - GIV. The two-way ANOVA and Tukey's test (pTendo em vista a importância do controle profissional da placa na prevenção da cárie, este estudo avaliou in vitro o desgaste de dois métodos de profilaxia (jato de bicarbonato de sódio-Profident e escova de Robinson com pasta de pedra pomes sobre o esmalte bovino hígido e com lesões artificiais de cárie. Foram utilizados 60 fragmentos de esmalte (4 X 4mm, divididos em 4 grupos: GI- 15 blocos hígidos tratados com escova de Robinson e pasta de pedra pomes; GII- 15 blocos hígidos tratados com Profident; GIII- 15 blocos desmineralizados tratados com escova de Robinson e pedra pomes e GIV- 15 blocos desmineralizados tratados com Profident. Nos fragmentos dos grupos III e IV foram simuladas lesões artificiais de cárie através da imersão em solução de ácido acético 0,05M, 50% saturada com pó de esmalte bovino, a 37ºC por 16 h. Os espécimes foram submetidos aos tratamentos profiláticos durante 10 segundos. A análise do desgaste foi

  9. Hydrogeologic investigations of the Miocene Nogales Formation in the Nogales Area, Upper Santa Cruz Basin, Arizona (United States)

    Page, William R.; Gray, Floyd; Bultman, Mark W.; Menges, Christopher M.


    Hydrogeologic investigations were conducted to evaluate the groundwater resource potential for the Miocene Nogales Formation in the Nogales area, southern Arizona. Results indicate that parts of the formation may provide new, deeper sources of groundwater for the area. Geologic mapping determined the hydrogeologic framework of the formation by defining lithologic, mineralogic, and stratigraphic characteristics; identifying potential aquifers and confining units; and mapping faults and fractures which likely influence groundwater flow. Geophysical modeling was used to determine the basin geometry and thickness of the Nogales Formation and younger alluvial aquifers and to identify target areas (deep subbasins) which may prove to be productive aquifers.Volcaniclastic sandstone samples from the formation were analyzed for porosity, bulk density, saturated hydraulic conductivity, and fabric. Effective porosity ranges from 16 to 42 percent, bulk density from 1.6 to 2.47 grams per cubic centimeter, and saturated hydraulic conductivity (SHC) from 4 to 57 centimeters per day (4.9×10-5 to 6.7×10-4 centimeters per second). Thin sections show that sandstone framework grains consist of quartz, feldspar, biotite, hornblende, pumice, volcanic glass, and opaque minerals. The matrix in most samples consists of pumice fragments, and some contain predominantly silt and clay. Samples with a mostly silt and clay matrix have lower porosity and SHC compared to samples with mostly pumice, which have higher and wider ranges of porosity and SHC. Pore space in the Nogales Formation sediments includes moldic, intercrystalline, and fracture porosity. Some intercrystalline pore space is partially filled with calcite cement. About one third of the samples contain fractures, which correspond to fractures noted in outcrops in all members of the formation.Scanning electron microscope (SEM) and x-ray diffraction (XRD) analyses indicate that most of the samples contained the zeolite clinoptilolite

  10. New high-capacity, calcium-based sorbents, calcium silicate sorbents. Final report, 1993--August 31, 1994

    Energy Technology Data Exchange (ETDEWEB)

    Kenney, M.C.; Chiang, R.K.; Fillgrove, K.L. [Case Western Reserve Univ., Cleveland, OH (United States)


    A search is being carried out for new calcium-based S0{sub 2} sorbents for induct injection. More specifically, a search is being carried out for induct injection calcium silicate sorbents that are highly cost effective. The objectives for the current year include the study of sorbents made from Ca(OH){sub 2}, from mixtures of Ca(OH){sub 2} and SiO{sub 2}, and from portland cement. They also include the study of sorbents made from model compounds. During this year, sorbents prepared from Ca(OH){sub 2} and from mixtures of Ca(OH){sub 2} and fumed SiO{sub 2} were investigated. The results show that very good SiO{sub 2}-modified Ca(OH){sub 2} sorbents in which the Si-to-Ca reactant ratio is low can be prepared from Ca(OH){sub 2} and fumed SiO{sub 2}. Sorbents prepared from Ca(OH){sub 2} and natural SiO{sub 2} or natural SiO{sub 2} sources were also studied. The results obtained show that very good SiO{sub 2}-modified Ca(OH){sub 2} sorbents and calcium silicate hydrate sorbents, C-S-H sorbents, can be prepared from Ca(OH){sub 2} and diatomite, pumice or perlite, minerals that are readily available. In addition. sorbents prepared from Ca{sub 3}SiO{sub 5} and {beta}-Ca{sub 2}SiO{sub 4} and from mixtures of these compounds and SiO{sub 2} were studied. The results secured demonstrate that very good C-S-H rich sorbents can be prepared from these compounds and from mixtures of them with SiO{sub 2}. They also provide information useful for interpreting the cement sorbent results. Sorbents prepared from cement and from mixtures of cement and natural SiO{sub 2} or SiO{sub 2} sources were investigated as well. The results secured show that cement and mixtures of it with diatomite, pumice or perlite rapidly yield excellent sorbents with the proper reaction conditions.

  11. Accurate dating of fluvial deposits in the Lateglacial Niers Valley system (Germany) using a multiple dating strategy (United States)

    Hoek, W. Z.; Kasse, C.; Peeters, J.; Wallinga, J.


    The River Rhine occupied the Niers Valley (Germany) from the Saalian Glaciation (MIS 6) until the Early Holocene (Kasse et al., Journal of Quaternary Science 2005). The fluvial landscape of the time of abandonment has been exceptionally well preserved, leaving a series of cut-off meanders and residual channels. This unique preservation provides the possibility to investigate Late Weichselian fluvial dynamics of the River Rhine. We combined several dating techniques to accurately determine the age of the deposits. We developed a sampling strategy based on detailed field survey and cross sectioning. 1) The geomorphological relationships of the cut-off meanders gave a relative age for the successive stages of meandering. 2) The occurrence of Laacher See Pumice in the point bar deposits gave a maximum age for these deposits. 3) Optically Stimulated Luminescence (OSL)-dating on sandy point bar and channel-fill deposits yielded absolute ages for active meandering and channel abandonment. 4) AMS-14C dates on terrestrial macrofossils from the basal fills of the residual channels yielded minimum ages for abandonment. 5) Biostratigraphy of the organic channel fills using palynology gave a relative chronology, which could be linked to the well-dated regional biostratigraphy of the nearby Netherlands and is cross-checked by additional AMS-14C dates. By combining these dating techniques we obtained a firm chronological framework that allows linkage to climate records and above the cross-validation of the different dating techniques. All techniques gave consistent ages that confirm the Lateglacial age and Early Holocene abandonment of the Niers Valley by the River Rhine. Palynology and 14C-dating on the channels fills supported the relative chronology indicated by the cross-cut relationships. The presence of the Laacher See Pumice in the point bar deposits, which has an unambiguous age of 12.9 ka cal. BP concurs with the organic channel fill ages. Because OSL signals in some

  12. Permeability of alkaline magmas: a study from Campi Flegrei, Italy (United States)

    Polacci, M.; Bouvet de Maissoneuve, C.; Giordano, D.; Piochi, M.; Degruyter, W.; Bachmann, O.; Mancini, L.


    Knowledge of permeability is of paramount importance for understanding the evolution of magma degassing during pre-, syn- and post-eruptive volcanic processes. Most permeability estimates existing to date refer to magmas of calc-alkaline compositions. We report here the preliminary results of permeability measurements performed on alkali-trachyte products erupted from the Campanian Ignimbrite (CI) and Monte Nuovo (MTN), two explosive eruptions from Campi Flegrei (CF), an active, hazardous caldera west of Naples, Southern Italy. Darcian (viscous) permeability spans a wide range between 10^-11 and 10^-14 m^2. We observe that the most permeable samples are the scoria clasts from the upper units of MTN; pumice samples from the Breccia Museo facies of CI are instead the least permeable. Non-Darcian (inertial) permeability follows the same trend as Darcian permeability. The first implication of this study is that porosity in alkaline as well as calc-alkaline magmas does not exert a first order control on permeability (e.g. the MTN samples are the most permeable but not the most porous). Second, sample geometry exhibits permeability anisotropy (higher permeability in the direction of vesicle elongation), suggesting stronger degassing in the vertical direction in the conduit. In addition, inertial effects are higher across the sample. As inertial effects are potentially generated by tortuosity (or tortuous vesicle paths), tortuosity is likely higher horizontally than vertically in the conduit. Finally, the measured CF permeability values overlap with those of rhyolitic pumice clasts from the Kos Plateau Tuff (Bouvet de Maisonneuve et al., 2009), together with CI one of the major Quaternary explosive eruptions of the Mediterranean region. This indicates that gas flow is strongly controlled by the geometry of the porous media, which is generated by the bubble dynamics during magma ascent. Therefore, permeability will depend on composition through the rheological properties

  13. The Ignimbrite Campana Magma Chamber: Pre-eruptive P-t-x Conditions From Melt Inclusion Data (United States)

    Marianelli, P.; Proto, M.; Sbrana, A.

    The Ignimbrite Campana (36 ka) represents the most powerful eruption characterizing the volcanic history of the Campi Flegrei caldera. The eruption was fed by a stratified magma chamber (Civetta et al., 1997). This study, based on melt inclusion investigations in phenocrysts of pumice, is aimed to better constrain depth, thermal conditions and composition of magmas hosted in the magma chamber. Samples from the Breccia Museo products (proximal deposits of the Ignimbrite Campana) were selected, due to their sin-eruptive and sin-depositional quenching. On the basis of melt inclusions investigations important informations about crystallization conditions (P, T, X) and volatile contents have been obtained. Glass compositions fall in the trachyte field close to the trachyte-phonolite boundary, similarly to the others Ignimbrite Campana products. The temperature of homogenization ranges between 850 and 1135°C. These values of temperature, that can be assumed as crystallization temperatures, correlate to the host crystal compositions with the highest one corresponding to melt inclusions trapped in less Fe-rich pyroxene. FTIR analyses on double -polished melt inclusions were carried out in order to investigate H2O and CO2 contents. Preliminary results indicate values of H2O that range from about 2 up to 8.0wt%, whereas CO2 was not detected. Lowest values of H2O (modal value = 2- 3wt%) correspond to the melt inclusions from layers at the top of the Breccia Museo (pumice flow deposits). Minimum pressures of crystallization are estimated in the range 100-200 MPa, assuming saturation conditions for the trapped melts and calculating the solubility of H2O in trachytic magmas according to the model of Moore et al. (1998). References Civetta L., Orsi G., Pappalardo L., Fisher R.V., Heiken G., Ort M. (1997): Geochemical zoning, mingling, eruptive dynamics and depositional processes ­ the Campanian Ignimbrite, Campi Flegrei caldera, Italy. J. Volcanol. Geoth. Res., 75: 183

  14. Unusual ice diamicts emplaced during the December 15, 1989 eruption of redoubt volcano, Alaska (United States)

    Waitt, R. B.; Gardner, C. A.; Pierson, T. C.; Major, J. J.; Neal, C. A.


    Ice diamict comprising clasts of glacier ice and subordinate rock debris in a matrix of ice (snow) grains, coarse ash, and frozen pore water was deposited during the eruption of Redoubt Volcano on December 15, 1989. Rounded clasts of glacier ice and snowpack are as large as 2.5 m, clasts of Redoubt andesite and basement crystalline rocks reach 1 m, and tabular clasts of entrained snowpack are as long as 10 m. Ice diamict was deposited on both the north and south volcano flanks. On Redoubt's north flank along the east side of Drift piedmont glacier and outwash valley, ice diamict accumulated as at least 3 units, each 1-5 m thick. Two ice-diamict layers underlie a pumice-lithic fall tephra that accumulated on December 15 from 10:15 to 11:45 AST. A third ice diamict overlies the pumiceous tephra. Some of the ice diamicts have a basal 'ice-sandstone' layer. The north side icy flows reached as far as 14 km laterally over an altitude drop of 2.3 km and covered an area of about 5.7 km 2. On Crescent Glacier on the south volcano flank, a composite ice diamict is locally as thick as 20 m. It travelled 4.3 km over an altitude drop of 1.7 km, covering about 1 km 2. The much higher mobility of the northside flows was influenced by their much higher water contents than the southside flow(s). Erupting hot juvenile andesite triggered and turbulently mixed with snow avalanches at snow-covered glacier heads. These flows rapidly entrained more snow, firn, and ice blocks from the crevassed glacier. On the north flank, a trailing watery phase of each ice-diamict flow swept over and terraced the new icy deposits. The last (and perhaps each) flood reworked valley-floor snowpack and swept 35 km downvalley to the sea. Ice diamict did not form during eruptions after December 15 despite intervening snowfalls. These later pyroclastic flows swept mainly over glacier ice rather than snowpack and generated laharic floods rather than snowflows. Similar flows of mixed ice grains and pyroclastic

  15. Seismic properties of volcanic rocks from Montagne Pelée (Martinique, Lesser Antilles) and their relations to transport properties (United States)

    Bernard, M.-L.; Zamora, M.


    Numerous laboratory and theoretical studies on the physical properties of rocks and their relationships - lead mainly in the framework of petroleum exploration - show that rock physics is necessary for an accurate quantitative interpretation of geophysical observations. Moreover joint inversion of different geophysical datasets is emerging as an important tool to enhance resolution and decrease inversion artifacts in imaging of structurally complex areas such as volcanoes. In many cases, the coupling between the inverted parameters is based on empirical or theoretical relationships derived from laboratory data. Consequently rock physics can be used to: interpret simultaneously several geophysical datasets on volcanoes when they are available, improve the imaging of volcano structures, and better understand the coupled processes that can occur during volcanic unrest. It's in this context that we lead a laboratory study on the transport properties (permeability, thermal and electrical conductivities) and seismic properties (velocity and attenuation of P and S waves) of volcanic rocks representative of Montagne Pelée (Martinique) deposits. In this presentation we will focus on (1) the seismic properties and (2) the relations between seismic and transport properties. The 43 samples collected are representative of the main lithological units of this volcano: vesicular lava blocks and indurated ashed from indurated block-and-ash flows also called breccias, vesicular lava blocks from "Pelean nuee ardente" flows, scoriae from scoria flows, pumices from ash-and-pumices flows, and dense lava blocks from lava flows and lava domes. Their total porosity varies over a wide range from 4 to 73%. Since the samples present similar chemical and mineralogical compositions (andesites), the main difference between the samples comes from their pore structure and reflects differences in the mechanisms of magma degassing and vesiculation during their formation (Bernard et al., 2007). This

  16. Probing permeability and microstructure: Unravelling the role of a low-permeability dome on the explosivity of Merapi (Indonesia) (United States)

    Kushnir, Alexandra R. L.; Martel, Caroline; Bourdier, Jean-Louis; Heap, Michael J.; Reuschlé, Thierry; Erdmann, Saskia; Komorowski, Jean-Christophe; Cholik, Noer


    Low permeability dome rocks may contribute to conduit overpressure development in volcanic systems, indirectly abetting explosive activity. The permeability of dome-forming rocks is primarily controlled by the volume, type (vesicles and/or microcracks), and connectivity of the void space present. Here we investigate the permeability-porosity relationship of dome-forming rocks and pumice clasts from Merapi's 1888 to 2013 eruptions and assess their possible role in eruptive processes, with particular emphasis on the 2010 paroxysmal eruption. Rocks are divided into three simple field classifications common to all eruptions: Type 1 samples have low bulk density and are pumiceous in texture; Type 2 samples, ubiquitous to the 2010 eruption, are dark grey to black in hand sample and vary greatly in vesicularity; and Type 3 samples are weakly vesicular, light grey in hand sample, and are the only samples that contain cristobalite. Type 2 and Type 3 rocks are present in all eruptions and their permeability and porosity data define similar power law relationships, whereas data for Type 1 samples are clearly discontinuous from these trends. A compilation of permeability and porosity data for andesites and basaltic andesites with published values highlights two microstructural transitions that exert control on permeability, confirmed by modified Bayesian Information Criterion (BIC) analysis. Permeability is microcrack- and diktytaxitic-controlled at connected porosities, φc, 31 vol.%. Type 3 basaltic andesites, the least permeable of the measured samples and therefore the most likely to have originated in the uppermost low-permeability dome, are identified as relicts of terminal domes (the last dome extruded prior to quiescence). Cristobalite commonly found in the voids of Type 3 blocks may not contribute significantly to the reduction of the permeability of these samples, mainly because it is associated with an extensive microporous, diktytaxitic texture. Indeed, the low

  17. Primary and redeposited facies from a large-magnitude, rhyolitic, phreatomagmatic eruption: Cana Creek Tuff, Late Carboniferous, Australia (United States)

    McPhie, J.


    The Cana Creek Tuff is one of four rhyolitic ignimbrite members of the Late Carboniferous Currabubula Formation, a volcanogenic conglomeratic braidplain sequence exposed along the western margin of the New England Orogen in northeastern New South Wales. The source is not exposed but was probably located tens of kilometres to the west of existing outcrops. The medial to distal parts of the tuff average about 70 m in thickness, are widespread (minimum present area ˜ 1400 km 2), and comprise a primary pyroclastic facies (ignimbrite, ash-fall tuff) and a redeposited volcaniclastic facies (sandstone, conglomerate). Both facies are composed of differing proportions of crystal fragments (quartz, plagioclase, K-feldspar), pumiceous clasts (pumice, shards, fine ash), and accidental lithics. The eruption responsible for this unit was explosive and of large magnitude (dense rock equivalent volume about 100 km 3). That it was also phreatomagmatic in character is proposed on the basis of: the intimate association of primary and redeposited facies; the presence of accretionary lapilli both in ignimbrite and in ash-fall tuff; the fine grain size of juvenile pyroclasts; the low grade of the ignimbrite; and the close similarity in facies, composition and magnitude to the deposits from the 20,000y. B.P. phreatomagmatic eruption at Taupo, New Zealand (the Wairakei and parts of the Hinuera Formations). The eruption began and ended from a vent with excess water available, possibly submersed in a caldera lake, and generated volcaniclastic sheet floods and debris flows. The emplacement of the primary pyroclastic facies is correlated with an intervening stage when the water:magma mass ratio was lower. The deposits from a large-magnitude, phreatomagmatic eruption are predicted to show systematic lateral variations in facies. Primary pyroclastic facies predominate near the source although the preserved stratigraphy is an incomplete record because of widespread contemporaneous erosion

  18. Magma Chamber Model of Batur Caldera, Bali, Indonesia: Compositional Variation of Two Facies, Large-Volume Dacitic Ignimbrites

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    Igan S. Sutawidjaja


    Full Text Available DOI:10.17014/ijog.2.2.111-124Batur is one of the finest known calderas on Earth, and is the source of at least two major ignimbrite eruptions with a combined volume of some 84 km3 and 19 km3. These ignimbrites have a similar compositions, raising the question of whether they are geneticaly related. The Batur Ignimbrite-1 (BI-1 is crystal poor, containing rhyodacitic (68 - 70wt % SiO2, white to grey pumices and partly welded and unwelded. The overlying Batur Ignimbrite-2 (BI-2 is a homogeneous grey to black dacitic pumices (64 - 66 wt % SiO2, unwelded and densely welded (40 - 60% vesicularity, crystal and lithic rich. Phase equilibria indicate that the Batur magma equilibrated at temperatures of 1100 - 1300oC with melt water contents of 3 - 6 wt%. The post-eruptive Batur magma was cooler (<1100oC and it is melt more water rich (> 6 wt % H2O. A pressure of 20 kbar is infered from mineral barometry for the Batur magma chamber. Magmatic chamber model is one in which crystals and melt separate from a convecting Batur magma by density differences, resulting in a stratified magma chamber with a homogeneous central zone, a crystal-rich accumulation zone near the walls or base, and a buoyant, melt-rich zone near the top. This is consistent with the estimated magma temperatures and densities: the pre-eruptive BI-1 magma was hoter (1300oC and more volatile rich (6 wt % H2O with density 2.25 g/cm3 than the BI-2 magma (1200oC; 4 wt % H2O in density was higher (2.50 g/cm3. Batur melt characteristics and intensive parameters are consistent with a volatile oversaturation-driven eruption. However, the higher H2O content, high viscosity and low crystal content of the BI-1 magma imply an external eruption trigger.

  19. Unusual ice diamicts emplaced during the December 15, 1989 eruption of redoubt volcano, Alaska (United States)

    Waitt, R.B.; Gardner, C.A.; Pierson, T.C.; Major, J.J.; Neal, C.A.


    Ice diamict comprising clasts of glacier ice and subordinate rock debris in a matrix of ice (snow) grains, coarse ash, and frozen pore water was deposited during the eruption of Redoubt Volcano on December 15, 1989. Rounded clasts of glacier ice and snowpack are as large as 2.5 m, clasts of Redoubt andesite and basement crystalline rocks reach 1 m, and tabular clasts of entrained snowpack are as long as 10 m. Ice diamict was deposited on both the north and south volcano flanks. On Redoubt's north flank along the east side of Drift piedmont glacier and outwash valley, ice diamict accumulated as at least 3 units, each 1-5 m thick. Two ice-diamict layers underlie a pumice-lithic fall tephra that accumulated on December 15 from 10:15 to 11:45 AST. A third ice diamict overlies the pumiceous tephra. Some of the ice diamicts have a basal 'ice-sandstone' layer. The north side icy flows reached as far as 14 km laterally over an altitude drop of 2.3 km and covered an area of about 5.7 km2. On Crescent Glacier on the south volcano flank, a composite ice diamict is locally as thick as 20 m. It travelled 4.3 km over an altitude drop of 1.7 km, covering about 1 km2. The much higher mobility of the northside flows was influenced by their much higher water contents than the southside flow(s). Erupting hot juvenile andesite triggered and turbulently mixed with snow avalanches at snow-covered glacier heads. These flows rapidly entrained more snow, firn, and ice blocks from the crevassed glacier. On the north flank, a trailing watery phase of each ice-diamict flow swept over and terraced the new icy deposits. The last (and perhaps each) flood reworked valley-floor snowpack and swept 35 km downvalley to the sea. Ice diamict did not form during eruptions after December 15 despite intervening snowfalls. These later pyroclastic flows swept mainly over glacier ice rather than snowpack and generated laharic floods rather than snowflows. Similar flows of mixed ice grains and pyroclastic

  20. Micro-seismic Signals Recorded During Fast Depressurization of Natural Volcanic Samples in a Shock Tube Apparatus (United States)

    Arciniega-Ceballos, A.; Alatorre-Ibargüengoitia, M.; Dingwell, D. B.; Scheu, B.; Delgado Granados, H.; Navarrete Montesinos, M.; Richard, D.; Kueppers, U.; Lavallée, Y.


    Volcanic eruptions generate different types of seismic signals in a wide frequency bandwidth. Volcano seismology studies have dealt with analyzing seismic signals characteristics and waveform patterns in order to discriminate between source, path and site effects and reconstruct the volcanic source dynamics. The source may involve brittle failure, magma transport, magma fragmentation, bubble collapse, fluid depressurization, fluid instabilities, degassing or a combination of these processes. Given the complexity of the volcanic source dynamics and the impossibility to undertake direct observations of the source, laboratory experiments provide a promising approach to investigate the source process. In this study we present preliminary results of an experimental approach in a shock tube apparatus. The apparatus consists of two serial steel pipes separated by a diaphragm: the autoclave which represents the "source mechanism", where the samples are pressurized and fragmented, and a tank which represents a conduit. The physical mechanism consists of the slow pressurization (using Argon gas) followed by rapid depressurization of natural samples of ash (> 0.5 mm), pumice (with average porosity of 63%,) and fragmented particles of pumice. Several experiments were designed under controlled pressure conditions (ranging from 4 to 20 MPa), at room temperature. Micro-seismic signals were detected during the depressurization process using high dynamic piezo film sensors (PDF, 0.001 - 10 G Hz analog bandwidth, low impedance), fixed and distributed along the tube system. In addition, two laser beams (wavelength 532 nm) measure the speed of the ejected materials; all sensors were correlated and synchronized with two dynamic pressure sensors located at the autoclave. The resonance of the empty tube apparatus was characterized in order to distinguish between natural resonance of the tank due to the pressure shock wave and the signals generated by depressurization of the system and

  1. Partial self-reversal of TRM in baked soils and ceramics from Ecuador (United States)

    Roperch, Pierrick; Chauvin, Annick; Valdez, Francisco


    Partial self-reversed thermoremanent magnetizations (SRTRMs) were observed in samples of baked soils, hearths and ceramics from the Rumipamba archeological site near Quito (Ecuador) and ceramics from sites near the town of Esmeraldas (Ecuador). The SRTRMs were recognized at room temperature on few samples but cooling the samples in liquid nitrogen enhanced the intensity of the SRTRM and measurement at 77°K enables its rapid detection in many samples from these sites. Alternating field demagnetization of the SRTRM indicate median destructive field of the order of 50 mT and thermal demagnetization give unblocking temperatures in the temperature range 280-380 °C. The magnetic carriers of the SRTRM are stable to heating in air or in vacuum up to 600 °C suggesting that titanomaghemite should not be the magnetic carrier of the SRTRM. The studied baked clays and ceramics contain detrital material of mainly volcanic origin. Ti-poor titanomagnetite is the main magnetic carrier identified by strong field data or susceptibility measurements versus temperature. Ilmeno-hematite grains were recognized with microscope observations under reflected light. Scanning electron microscope observations with energy dispersive X-ray spectrometry indicate a Ti/Fe ratio corresponding to an ilmenite content of ˜0.55. We also compared the magnetic properties of the partially self-reversed baked clays with those of the self-reversed Pinatubo pumices. The SRTRMs were measured upon cooling from room temperature to 20°K with the MPMS. Upon cooling to 20°K the SRTRM show a nearly tenfold increase in intensity with respect to the room temperature measurement. The baked clay and ceramics from Ecuador carrying the SRTRM share similar magnetic properties with the Pinatubo pumices (unblocking temperatures, low temperature behavior) supporting the interpretation that detrital hemoilmenite originating from the Holocene activity of the numerous Ecuadorian volcanoes is the main carrier of the SRTRM in

  2. Dynamics of an unusual cone-building trachyte eruption at Pu`u Wa`awa`a, Hualālai volcano, Hawai`i (United States)

    Shea, Thomas; Leonhardi, Tanis; Giachetti, Thomas; Lindoo, Amanda; Larsen, Jessica; Sinton, John; Parsons, Elliott


    The Pu`u Wa`awa`a pyroclastic cone and Pu`u Anahulu lava flow are two prominent monogenetic eruptive features assumed to result from a single eruption during the trachyte-dominated early post-shield stage of Hualālai volcano (Hawaíi). Púu Wa`awa`a is composed of complex repetitions of crudely cross-stratified units rich in dark dense clasts, which reversely grade into coarser pumice-rich units. Pyroclasts from the cone are extremely diverse texturally, ranging from glassy obsidian to vesicular scoria or pumice, in addition to fully crystalline end-members. The >100-m thick Pu`u Anahulu flow is, in contrast, entirely holocrystalline. Using field observations coupled with whole rock analyses, this study aimed to test whether the Pu`u Wa`awa`a tephra and Pu`u Anahulu lava flows originated from the same eruption, as had been previously assumed. Crystal and vesicle textures are characterized along with the volatile contents of interstitial glasses to determine the origin of textural variability within Pu`u Wáawáa trachytes (e.g., magma mixing vs. degassing origin). We find that (1) the two eruptions likely originated from distinct vents and magma reservoirs, despite their proximity and similar age, (2) the textural diversity of pyroclasts forming Pu`u Wa`awa`a can be fully explained by variable magma degassing and outgassing within the conduit, (3) the Pu`u Wa`awa`a cone was constructed during explosions transitional in style between violent Strombolian and Vulcanian, involving the formation of a large cone and with repeated disruption of conduit plugs, but without production of large pyroclastic density currents (PDCs), and (4) the contrasting eruption styles of Hawaiian trachytes (flow-, cone-, and PDC-forming) are probably related to differences in the outgassing capacity of the magmas prior to reaching the surface and not in intrinsic compositional or temperature properties. These results further highlight that trachytes are "kinetically faster" magmas compared

  3. Chronology of the 2007 eruption of Stromboli and the activity of the Scientific Synthesis Group (United States)

    Barberi, Franco; Civetta, Lucia; Rosi, Mauro; Scandone, Roberto


    On 27 February 2007, at 12.49 GMT, a new eruption of Stromboli took place with the effusion of a lava flow from a fracture cutting the flank of the NE cone, which rapidly reached the sea. The eruption had been heralded by an increase in the amplitude of tremor and flank movement since at least the 14th of February. Short-term precursors were an increase in the rate of occurrence of small landslides within the "Sciara del Fuoco" scar on the North-western flank of the volcano. A new effusive vent opened at 18.30 GMT on the Sciara del Fuoco at an height of 400 m asl. The new lava emission caused the sudden termination of the summit flow and initiated a period of non-stationary lava outpouring which ended on 2 April, 2007. The eruption has been characterized by a rapid decrease in the eruption rate after the first days and subsequently by episodic pulse increases. On the 15th of March, the increase in lava outpouring, monitored by a thermal camera, heralded by 9 min the occurrence of a violent paroxysmal explosion with the formation of an impulsive eruption column and the emission of small pumices mingled with black scoriae. The pumice had a bulk composition similar to that of the lava and of the black scoriae, but with a distinct lower content of phenocrysts. A similar feature has been repeatedly observed during the major explosive paroxysms of Stromboli. Short term precursors of the paroxysm were recorded by strainmeter and tiltmeter stations. The volcano monitoring activity has been made by a joint team of researchers from the INGV sections of Catania, Napoli, Palermo and Rome, along with researchers from the Universities of Florence, Pisa, Roma Tre, and Palermo. The scientific activity was coordinated by a Synthesis Group made up by scientists responsible for the different monitoring techniques of INGV and Universities and by the volcanic experts of Commissione Nazionale Grandi Rischi of the Prime Minister Office (Civil Protection Department). The group made a

  4. Subglacial Silicic Eruptions: Wet Cavities and Moist Cavities. (United States)

    Stevenson, J. A.; McGarvie, D. W.; Gilbert, J. S.; Smellie, J. L.


    Comparing the deposits of subglacial eruptions with those of subaerial and subaqueous eruptions enables the influence of magma-water-ice interactions to be explored. In this presentation, the Icelandic subglacial rhyolite tuyas of Kerlingarfjöll and Prestahnúkur are compared with subaerial and subaqueous rhyolite formations at Sierra La Primavera, México. Prestahnúkur formed by the subglacial lava effusion and thick lava flows with steep termini are products of confinement by ice walls. Basal deposits of perlitised obsidian lobes suggest a water-saturated environment, and the extremely abundant microvesicular lava blocks surrounding these lobes and throughout the edifice are broadly similar to the carapaces of silicic lava domes at La Primavera known to have a subaqueous origin. Although bedded and sorted deposits are present at Prestahnúkur, they are trivial compared to the thick and extensive caldera-lake deposits of La Primavera, which even contain a "giant pumice" marker bed formed by the lake-wide deposition of once-bouyant blocks. The Kerlingarfjöll rhyolite tuyas formed during explosive subglacial eruptions. The first-erupted material forms structureless beds of phreatomagmatically-fragmented ash; ash from subaqueous eruptions at La Primavera is similarly fine grained, but in contrast is well-bedded (due to lacustrine deposition). Later-erupted material at Kerlingarfjöll typically consists of massive unconsolidated lapilli-tuffs. The lapilli themselves are similar to those within the well-sorted subaerially-formed pumice cones La Primavera, however Kerlingarfjöll's lapilli- tuffs have grain-size characteristics of proximal pyroclastic flows. These observations suggest that although similar fragmentation mechanisms operated in both locations, transport and consequent sorting was limited at Kerlingarfjöll. The different products of the two Icelandic subglacial tuyas are related to their different eruption rates and magma volatile contents. Melting of

  5. Somma-Vesuvius Plinian Eruptions fed by mafic magma: insights from bubbles in melt inclusions (United States)

    Esposito, R.; Redi, D.; Cannatelli, C.; Danyushevsky, L. V.; Lima, A.; Bodnar, R. J.; De Vivo, B.


    Mt. Somma-Vesuvius Plinian eruptions were first described by Pliny the younger in 79 AD during the infamous eruption that destroyed Pompeii. Today, such eruptions are still a concern to the nearly 3 million people living in the Naples metropolitan area. Understanding the source for Mt. Somma-Vesuvius magma and the coexisting volatile phase is vital to better constrain the long-term eruptive behavior of this volcano. In the present study, ~ 50 olivine phenocrysts were selected from lavas and pumices produced during mild effusive events referred to as inter-Plinian eruptions, and from highly explosive Plinian eruptions that occurred at Mt. Somma-Vesuvius between 33000 ka and 1631 AD. Selected olivine phenocrysts containing MI were examined petrographically and analyzed for Fo content. Fo varies from 69 to 73 mole% for inter-Plinian olivine crystals and from 84 to 90 mole% with one zoned olivine containing 76-81 mole% Fo, for Plinian olivine crystals. Investigated MI vary from slightly crystallized to highly crystallized. Selected crystallized MI were reheated using the Vernadsky stage, and quenched to a homogeneous glass (Group 1) or glass plus a vapor bubble (Group 2). On one hand, MI of Group 1 are hosted in olivine ranging from Fo72 to Fo76 and were all erupted from the Pompeii eruption (white pumice deposit). On the other hand, MI of Group 2 are trapped in olivine ranging from Fo69 to Fo81 and from Fo84 to Fo90, and the hosts are representative of both Plinian and inter-Plinian events. The only eruption where Group-1 and Group-2 MI coexist is the Pompeii eruption. Group 2 MIs were further analyzed by Raman to test for the presence of volatiles (CO2 or H2O) in the vapor bubbles. CO2 was detected in all MI analyzed. CO2 density was determined using the distance between the two Fermi-diad peaks, and ranges between 0.14 and 0.55 g/cm3. Six MI also showed evidence for H2O in the vapor bubble. In addition, carbonates were detected at the glass-vapor interface of five

  6. Distribution of tephra from the 1650 AD submarine eruption of Kolumbo volcano, Greece (United States)

    Fuller, S. A.; Carey, S.; Nomikou, P.


    Kolumbo submarine volcano, located 7 km northeast of Santorini in the Aegean Sea, last erupted in 1650 AD resulting in about 70 fatalities on Thera from gas discharge and significant coastal destruction from tsunamis. Extensive pumice rafts were reported over a large area surrounding Santorini, extending as far south as Crete. Tephra from the 1650 AD submarine eruption has been correlated in sediment box cores using a combination of mineralogy and major element composition of glass shards. The biotite-bearing rhyolite of Kolumbo can be readily discriminated from other silicic pyroclastics derived from the main Santorini complex. In general the tephra deposits are very fine grained (silt to fine sand-size), medium gray in color, and covered by about 10 cms of brown hemipelagic sediment. This corresponds to an average background sedimentation rate of 29 cm/kyr. The distribution of the 1650 AD Kolumbo tephra extends over an area larger than previously inferred from seismic profiles on the volcano's slopes and in adjacent basins. The cores indicate tephra deposits at least 19 km from the caldera, more than double the approximate 9 km inferred from seismic data. The preferential occurrence of the tephra within basins and sedimentological features such as cross bedding and laminations suggests that emplacement was dominated by sediment gravity flows generated from submarine and subaerial eruption plumes. We suggest that generation of the sediment gravity flows took place by collapse of submarine eruption columns and by Rayleigh-Taylor instabilities that formed on the sea surface as subaerial fallout accumulated from parts of the columns that breached the surface. Additionally, SEM imaging reveals particle morphologies that can be attributed to fragmentation by both primary volatile degassing (bubble wall shards) and phreatomagmatic activity (blocky equant grains). It is likely that phreatomagmatic activity became more important in the latter stages of the eruptive

  7. Magma plumbing system at the beginning of repeated caldera eruption: A case study on Aso-1 erupted about 270 ky ago from Aso caldera, SW Japan (United States)

    Miyagi, I.; Hoshizumi, H.; Miyabuchi, Y.


    In order to understand the commencement of magma plumbing system of a polygenetic caldera, we started petrological study on the earliest eruptive product of Aso caldera, SW Japan. Aso caldera is one of the active volcano in Japan which have produced four stages (Aso-1, -2, -3, -4) of large-scale pyroclastic flow deposits 270 to 90 ky. ago. A suite of samples were collected from the bottom of Aso-1 pyroclastic flow deposit and from the underlying tephra layer (Ono et al., 1979). The tephra comprises more than 10 pumice fall units inter-layered by dark gray volcanic ash. For whole rock chemistry, coarser pumice fragments were separated. For mineral and glass chemistry, phenocrysts and glass particles were handpicked from the sieved 500-1000 um fractions under a binocular microscope. This fraction consist of plagioclase, orthopyroxene, variably vesiculated volcanic glass fragments, and clinopyroxene phenocrysts. They were analyzed using an electron micro-probe. The suite of samples are similar and major temporal change is the chemical composition of orthopyroxenes; those from upper horizon are relatively Mg rich. Anorthite content of plagioclase phenocryst is bimodal 49-53 mol. % (major) and 57-70 mol. % (minor). Silica content of matrix glass fall in a narrow range 68-70 wt. %. Temperature and oxygen fugacity were estimated to be 865-905 deg-C and FMQ+2 log unit, respectively, using ILMAT (Lepage, 2003). Pressure and water content of the magma are estimated to be 5-7 kbar and 0.5-1 wt. % H2O, respectively, using rhyolite-MELTS (Gualda et al., 2012) on the most undifferentiated tholeiitic basalt of Aso 4KC-03 (Hunter, 1998) to reproduce the observed composition of matrix glass (68-70 wt. % SiO2) and plagioclase (An 49-53 mol. %). The calcic plagioclase (An 57-70 mol. %), however, suggest that the basalt was initially hydrous and require magma degassing before the differentiation. If we assume degassing by magma convection in a conduit (Kazahaya et al., 1994), the

  8. Dune development and migration to damage long established vegetation colonies in the lahar deposition zone of Ruapehu Volcano, New Zealand (United States)

    Ohno, Y.; Kasai, M.; Marutani, T.


    This study reports migration of dunes that mainly originate from lahar deposits and gully erosion, in the Rangipo Desert on the skirts of the Ruapehu Volcano, New Zealand. Although the Rangipo Desert is not a dry desert (average annual rainfall: 1100mm), the occasional supply of volcanic materials from Ruapehu, strong wind (average maximum speed in a day: 12 m/s) together with low winter temperatures has created a desert-like landscape. The study site consists of a flood plain with sporadic tussock and alpine to sub-alpine vegetation colonies which often form mound-like structures and sand dunes on terraces on the flanks of the volcano. The accretionary mounds and dunes comprise layers of tephra and pumice of various ages, together with interstitial wind-blown materials. While shrubs thrive on these terrace tops, it was observed that migrating dunes of 3 m in height have progressively buried and killed vegetation at two sites. Aerial photographs taken in 2000 and 2011 indicated that the dunes originated from pockets of lahar deposits and gully out-wash materials on the flood plain and were migrating in the major leeward wind direction (Northeast), or towards the sites. The migration rate at one site was estimated at 5 m/year from the photography. The flood plain pockets had formed at points where the floor slope changed from steep to gentle. As they contain finer materials than their surroundings, they have produced a series of sequential dunes. The exposed floor between the dunes comprises pumice layers of low infiltration capacity, suggesting that dunes migrate and develop as they strip off floor deposits. Subsequent exposure of the layers induces surface flow concentration in wet weather to cause gully incision. In conclusion, lahar occurrence is a major controlling factor in development in the landscape of the Rangipo Desert, by not only directly flowing at times into the flood plain, but also by producing migrating dunes that impact on existing vegetation

  9. Dynamics of explosive paroxysms at open andesitic systems: high-resolution mass distribution analyses of 2006 tephra from Tungurahua volcano (Ecuador) (United States)

    Le Pennec, J.; Eychenne, J.; Ramon, P.; Yepes, H.


    Many andesitic volcanoes at subduction plate margins can experience in the course of their evolution periods of sub-continuous eruption during years, decades, or centuries. Such long-lived periods may embrace more or less intense outgassing events, extrusion of viscous lava flows and domes (e.g. Colima in Mexico, Merapi in Indonesia, Arenal in Costa Rica), and explosive activity of uneven intensity (e.g. Semeru in Indonesia, Sakurajima in Japan, Sangay in Ecuador). In addition, strong explosive events of short duration may occur, with potential generation of pyroclastic flows on the flanks and beyond, which can pose significant hazards in populated regions. The origin and dynamics of such violent eruptions remain poorly known and may involve a combination of different factors. Tungurahua volcano, Ecuador, reawaken in 1999 and is an example of such open-system behaviour that experienced a strong and deadly andesitic pyroclastic flow-forming event in August 2006. Inspection of the deposits suggested that the event could have been triggered by magma mixing (silicic pumices in the tephra), magma-water interaction (presence of xenolithic clasts) or deep andesitic magma reinjection (based on mineral chemistry). Here we investigate these options by performing a high-resolution mass budget analysis of the scoria fall deposit. This is achieved by analysing componentry compositions and their mass distribution pattern in the layer, which allow us to document and integrate exponential and power laws mass decay rates over wide areas. The results yield a total mass for the tephra layer of ~2 x 1010kg. The pumice mass fraction is far too small (< 0.4 %) to account for the high explosivity of the 2006 event. Similarly, the xenoclastic mass fraction is small (0.2%) and suggests limited magma-water interaction. Instead, we interpret these xenoclasts as a result of upper conduit erosion at a rate of ~30 cm/hour during the paroxysm. Altogether our results support an explosive event

  10. 3D Petrography - Serendipitous Discovery of Magmatic Vapor Deposition of Anhydrite at Mount Pinatubo by SEM Imaging of Outer Crystal Surfaces (United States)

    Fournelle, J. H.; Jakubowski, R. T.; Welch, S.; Swope, R. J.


    A standard petrographic technique focuses upon examination of surfaces or planes cut through rock samples, with one approach studying chemical variations in a core to rim traverse using various microprobes, and more recently, another determining the distribution of crystal sizes to obtain information about nucleation and growth. We show that another mineral domain deserves petrographic attention: the outer surfaces of crystals, which are normally relegated to nearly invisible thin lines in a cut section. In studying anhydrite phenocrysts from the 1991 climactic eruption of Mt. Pinatubo, SEM examination of "raw" pumice fragments showed the existence of a Ca-sulfur-rich phase with hexagonal morphology residing upon plagioclase phenocryst surfaces in vesicles (Fournelle et al,1996, Fig 9). In 1992, Terry Gerlach suggested that the Pinatubo anhydrite phenocrysts should be evaluated with XRD to determine if they were indeed orthorhombic anhydrite (β -CaSO4), and not a lower temperature polymorph (i.e., α or γ ). In 1998, we recommenced this project, mounting several dozen 100-200 micron-size phenocrysts of the proper density fraction on tape (minerals had been separated from the pumices using standard techniques). They were examined by low resolution SEM with EDS to distinguish the anhydrite from apatite, prior to single-crystal XRD. We were surprised to find that many of the anhydrite surfaces were decorated with small mounds, which upon examination by high resolution SEM turned out to be micron and smaller pyramids, with some surfaces bearing hundreds. Single-crystal XRD verified that the phenocrysts were orthorhombic anhydrite, and EBSD verified that the small pyramids were the same. Eventually we found that these surface pyramids are common phenomena in experimental or industrial chemical vapor deposition processes when nucleation overwhelms growth. Textural relations were consistent with these pyramids being deposited in situ, within the Pinatubo magma chamber

  11. Tropical cyclone Pam field survey in Vanuatu (United States)

    Fritz, Hermann M.; Pilarczyk, Jessica E.; Kosciuch, Thomas; Hong, Isabel; Rarai, Allan; Harrison, Morris J.; Jockley, Fred R.; Horton, Benjamin P.


    Severe tropical cyclone Pam (Cat. 5, SSHS) crossed the Vanuatu archipelago with sustained winds of 270 km/h on March 13 and 14, 2015 and made landfall on Erromango. Pam is the most intense tropical cyclone to make landfall on Vanuatu since the advent of satellite imagery based intensity estimates in the 1970s. Pam caused one of the worst natural disaster in Vanuatu's recorded history. Eleven fatalities were directly attributed to cyclone Pam and mostly due to lack of shelter from airborne debris. On March 6 Pam formed east of the Santa Cruz Islands causing coastal inundation on Tuvalu's Vaitupu Island located some 1100 km east of the cyclone center. Pam intensified while tracking southward along Vanuatu severely affecting the Shefa and Tafea Provinces. An international storm surge reconnaissance team was deployed to Vanuatu from June 3 to 17, 2015 to complement earlier local surveys. Cyclone Pam struck a remote island archipelago particularly vulnerable to the combined cyclonic multi-hazards encompassing extreme wind gusts, massive rainfall and coastal flooding due to a combination of storm surge and storm wave impacts. The team surveyed coastal villages on Epi, the Shepherd Islands (Tongoa and Mataso), Efate (including Lelepa), Erromango, and Tanna. The survey spanned 320 km parallel to the cyclone track between Epi and Tanna encompassing more than 45 sites including the hardest hit settlements. Coastal flooding profiles were surveyed from the shoreline to the limit of inundation. Maximum coastal flood elevations and overland flow depths were measured based on water marks on buildings, scars on trees, rafted debris and corroborated with eyewitness accounts. We surveyed 91 high water marks with characteristic coastal flood levels in the 3 to 7 m range and composed of storm surge with superimposed storm waves. Inundation distances were mostly limited to a few hundred meters but reached 800 m on Epi Island. Wrack lines containing pumice perfectly delineated the

  12. Surficial Geology of Mount Rainier National Park, Washington (United States)

    Crandell, Dwight Raymond


    Much of the ground surface around Mount Rainier volcano is directly underlain by loose geologic deposits that veneer the hard rock formations. Examples of these deposits are sand and gravel bars along the rivers, ridges of loose rock debris beside the glaciers, and sloping aprons of rock fragments beneath almost every cliff. Even though they are generally thin and inconspicuous when compared with the rock formations, these surficial deposits are clues to geologic events that have profoundly influenced the shape of the park's landscape. Thus, from the character and extent of glacial deposits one can judge the age and size of former glaciers that carved the cirques and deep canyons of the park; from the mudflows which streamed down nearly every valley one can infer the age and size of huge landslides of the past that helped determine Mount Rainier's present shape; and from the pumice deposits some of the volcano's recent eruptive activity can be reconstructed. The map (plate 1, in pocket) that accompanies this description of the surficial deposits of Mount Rainier National Park shows the location of the various geologic formations, and the explanation shows the formations arranged in order of their relative age, with the oldest at the bottom. The text describes the surficial deposits in sequence from older to younger. A discussion of the pumice deposits of the park, which were not mapped, is followed by a description of the formations shown on the geologic map. Inspection of the geologic map may lead the viewer to question why the surficial deposits are shown in more detail in a zone several miles wide around the base of the volcano than elsewhere. This is partly because the zone is largely near or above timberline, relatively accessible, and the surficial deposits there can be readily recognized, differentiated, and mapped. In contrast, access is more difficult in the heavily timbered parts of the park, and surficial deposits there are generally blanketed by a dense

  13. Minimal alterations on the enamel surface by micro-abrasion: in vitro roughness and wear assessments

    Directory of Open Access Journals (Sweden)

    Marcela Charantola Rodrigues


    Full Text Available Objective: To evaluate the in vitro changes on the enamel surface after a micro-abrasion treatment promoted by different products. Material and Methods: Fifty (50 fragments of bovine enamel (15 mm × 5 mm were randomly assigned to five groups (n=10 according to the product utilized: G1 (control= silicone polisher (TDV, G2= 37% phosphoric acid (3M/ESPE + pumice stone (SS White, G3= Micropol (DMC Equipment, G4= Opalustre (Ultradent and G5= Whiteness RM (FGM Dental Products. Roughness and wear were the responsible variables used to analyze these surfaces in four stages: baseline, 60 s and 120 s after the micro-abrasion and after polishing, using a Hommel Tester T1000 device. After the tests, a normal distribution of data was verified, with repeated ANOVA analyses (p≤0.05 which were used to compare each product in different stages. One-way ANOVA and Tukey tests were applied for individual comparisons between the products in each stage (p≤0.05. Results: Means and standard deviations of roughness and wear (µm after all the promoted stages were: G1=7.26(1.81/13.16(2.67, G2=2.02(0.62/37.44(3.33, G3=1.81(0.91/34.93(6.92, G4=1.92(0.29/38.42(0.65 and G5=1.98(0.53/33.45(2.66. At 60 seconds, all products tended to produce less surface roughness with a variable gradual decrease over time. After polishing, there were no statistically significant differences between the groups, except for G1. Independent of the product utilized, the enamel wear occurred after the micro-abrasion. Conclusions: In this in vitro study, enamel micro-abrasion presented itself as a conservative approach, regardless of the type of the paste compound utilized. These products promoted minor roughness alterations and minimal wear. The use of phosphoric acid and pumice stone showed similar results to commercial products for the micro-abrasion with regard to the surface roughness and wear.

  14. Time correlation by palaeomagnetism of the 1631 eruption of Mount Vesuvius. Volcanological and volcanic hazard implications (United States)

    Carracedo, J. C.; Principe, C.; Rosi, M.; Soler, V.


    The 1631 eruption of Mount Vesuvius was the most destructive episode in the recent volcanic history of Vesuvius and the last in which large pyroclastic flows were emitted. The controversy about whether lava flows were also generated in this eruption, as sustained in the mapping by Le Hon (1866) and by the interpretation by some authors (Burri et al., 1975; Rolandi et al., 1991) of eyewitness accounts, is important not only for a better understanding of the eruption but also for the implications in the prediction of volcanic hazards of this volcano, set in an overpopulated area with more than 3 million people potentially at risk. Short-period palaeomagnetic techniques (secular variation curve) have been applied to correlate lava flows interpreted as produced in the event of 1631 with the pyroclastic flow of this same eruption and other lava flows unquestionably emitted prior to this eruptive event. The model that best fits the results obtained suggests that the presumed 1631 lava flows were not the result of a single eruptive event but were, in fact, produced by several different eruptions. These lava flows also have a better palaeomagnetic correlation with the medieval lava flows than with the pyroclastic flow of 1631, whose juvenile pumice clasts have a well-defined single component magnetization that fits in the expected corresponding position of the secular variation curve for that age. The palaeomagnetic characteristics of the 1631 pyroclastic flow are compatible with a "hot" depositional temperature (apparently above the Curie point of magnetite, 585 °C) for the juvenile pumice fragments (magmatic fraction) and a "cold" deposition for the non-magmatic fraction. This suggests the lack of thermal equilibration during transport of the larger clasts, probably due to the short distance travelled by the pyroclastic flows. The main volcanological and volcanic hazard issues of this work are that the 1631 event was entirely explosive and that pyroclastic flow activity

  15. Petrology and geochemistry of three early Holocene eruptions from Makushin volcano, Alaska (United States)

    Larsen, J. F.; Schaefer, J. R.


    Makushin volcano is an 1800-meter-high stratovolcano with an ice-filled, 2x3 km summit crater, 25 km west of Dutch Harbor and Unalaska, Alaska on Unalaska Island. This study examines the petrology and geochemistry of the three largest, early Holocene eruptions from Makushin: "CFE", (ca. 9000 BP), "Nateekin" (ca. 8700 BP), and "Driftwood" (ca. 8200 BP). The CFE eruption produced thick scoria fall deposits to the northeast and pyroclastic-flow deposits in upper Makushin and "Waterfall" valleys extending >12 km to the east and north. The Nateekin eruption produced fine ash to fine lapilli deposits that are up to 20 cm thick in the Unalaska town area. The Driftwood eruption produced tan pumice and dense, black scoriaceous fall deposits, up to 2 m thick, primarily in the Driftwood valley area to the northeast. Whole rock major (XRF) and trace element (LA-ICPMS) compositions were collected from the CFE and Driftwood samples. Samples from the Nateekin unit were too fine-grained for whole-rock analyses. Analyses of glass, phenocryst, and microlite phases from all three units were collected at UAF using the JEOL JXA-8530F electron microcprobe. The CFE and Driftwood eruptions produced medium K2O, tholeiitic andesites: CFE = 56 to 60 wt. % SiO2; Driftwood = 60 to 63 wt. % SiO2. The three units have andesite to rhyodacite glass compositions: CFE= 57 to 64 wt. % SiO2; Nateekin = 59 to 61 wt. % SiO2; Driftwood = 67 to 70 wt. % SiO2. The CFE and Driftwood samples have plagioclase, clinopyroxene and orthopyroxene phenocrysts, with minor olivine in the CFE fall deposit scoria. The pyroxenes are uniform in composition: Opx = Wo4.6En58.7Fs36.7 (n=58) and Cpx = Wo39.7En41.9Fs18.4 (n=132). Plagioclase phenocrysts from Driftwood pumice have An52-54 cores and An48-49 rims. CFE plagioclase phenocrysts are bimodal, with a lower An50-54 group and a higher An70-89 group. Nateekin glass compositions are similar to CFE scoria analyses from the middle to top of the unit, indicating little

  16. Magma Storage, Recharge and the Caldera Cycle at Rabaul, Papua New Guinea (United States)

    Fabbro, G.; Bouvet de Maisonneuve, C.; Sindang, M.


    Many calderas have a history of repeated caldera-forming eruptions, interspersed with periods of more minor activity. Rabaul, for instance, has had at least 11 ignimbrite-forming eruptions over the last 200 ky. The most recent of these was the '1400 BP' eruption, which led to caldera collapse. Since then, there has been multiple smaller eruptions, including the ongoing activity from Tavurvur and Vulcan. An important question facing volcanology today is what controls the size of eruptions at calderas such as Rabaul.Detailed stratigraphic sampling of the 1400BP eruption reveals that prior to eruption, the magma reservoir below Rabaul contained a well-mixed dacite with whole-rock SiO2 contents of 65.0-66.4 wt%. The dacite contains a single phenocryst assemblage of plag (An44-52), cpx (En43-46Fs13-15Wo40-41), opx (En69-71Fs25-28Wo3) and magnetite, along with minor apatite. The homogeneity of the dacite is underscored by the narrow range of compositions of both the matrix glass and the melt inclusions (67.8-69.0 wt% SiO2). The only exception to this is at the top of the ignimbrite, representing some of the last magma to have been withdrawn. Dispersed throughout the dacitic pumices are darker, more mafic blebs. Streaks of mingled magma with a range of SiO2 contents, down to 59.9 wt% SiO2 are also found in the pumice, suggesting that a mafic recharge magma was intruded into the base of the reservoir shortly before eruption. High TiO2 contents rule out the direct involvement of basalt, and instead imply the magma that intruded into the reservoir was an andesite with at least 56 wt% SiO2. Phenocrysts related to this recharge magma are rare, and the crystals found in the dark blebs are identical in composition to those found in the dacite, indicating that the recharge was aphyric. The present-day, post-caldera recharge magma is different to the pre-1400 BP recharge magma: it is basaltic. This suggests that the plumbing system of Rabaul is different during the pre-caldera and

  17. Tephrochronology of the Mont-Dore volcanic Massif (Massif Central, France): new 40Ar/39Ar constraints on the Late Pliocene and Early Pleistocene activity (United States)

    Nomade, Sébastien; Pastre, Jean-François; Nehlig, Pierre; Guillou, Hervé; Scao, Vincent; Scaillet, Stéphane


    The Mont-Dore Massif (500 km2), the youngest stratovolcano of the French Massif Central, consists of two volcanic edifices: the Guéry and the Sancy. To improve our knowledge of the oldest explosive stages of the Mont-Dore Massif, we studied 40Ar/39Ar-dated (through single-grain laser and step-heating experiments) 11 pyroclastic units from the Guéry stratovolcano. We demonstrate that the explosive history of the Guéry can be divided into four cycles of explosive eruption activity between 3.09 and 1.46 Ma (G.I to G.IV). We have also ascertained that deposits associated with the 3.1-3.0-Ma rhyolitic activity, which includes the 5-km3 "Grande Nappe" ignimbrite, are not recorded in the central part of the Mont-Dore Massif. All the pyroclastites found in the left bank of the Dordogne River belong to a later explosive phase (2.86-2.58 Ma, G.II) and were channelled down into valleys or topographic lows where they are currently nested. This later activity also gave rise to most of the volcanic products in the Perrier Plateau (30 km east of the Mont-Dore Massif); three quarters of the volcano-sedimentary sequence (up to 100 m thick) was emplaced within less than 20 ky, associated with several flank collapses in the northeastern part of the Guéry. The age of the "Fournet flora" (2.69 ± 0.01 Ma) found within an ash bed belonging to G.II suggests that temperate forests already existed in the French Massif Central before the Pliocene/Pleistocene boundary. The Guéry's third explosive eruption activity cycle (G.III) lasted between 2.36 and 1.91 Ma. It encompassed the Guéry Lake and Morangie pumice and ash deposits, as well as seven other important events recorded as centimetric ash beds some 60 to 100 km southeast of the Massif in the Velay region. We propose a general tephrochronology for the Mont-Dore stratovolcano covering the last 3.1 My. This chronology is based on 44 40Ar/39Ar-dated events belonging to eight explosive eruption cycles each lasting between 100 and 200

  18. Proposed stratigraphic nomenclature and macroscopic identification of lithostratigraphic units of the Paintbrush Group exposed at Yucca Mountain, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Buesch, D.C.; Spengler, R.W.; Moyer, T.C.; Geslin, J.K.


    This paper describes the formations of the Paintbrush Group exposed at Yucca Mountain, Nevada, presents a detailed stratigraphic nomenclature for the Tiva Canyon and Topopah spring Tuffs, and discusses the criteria that define lithostratigraphic units. The Tiva Canyon and Topopah Spring Tuffs are divided into zones, subzones, and intervals on the basis of macroscopic features observed in surface exposures and borehole samples. Primary divisions reflect depositional and compositional zoning that is expressed by variations in crystal content, phenocryst assemblage, pumice content and composition, and lithic content. Secondary divisions define welding and crystlalization zones, depositional features, or fracture characteristics. Both formations are divided into crystal-rich and crystal-poor members that have an identical sequency of zones, although subzone designations vary slightly between the two units. The identified lithostratigraphic divisions can be used to approximate thermal-mechanical and hydrogeologic boundaries in the field. Linking these three systems of nomenclature provides a framework within which to correlate these properties through regions of sparse data.

  19. Lithostratigraphy of the Calico Hills Formation and Prow Pass Tuff (Crater Flat Group) at Yucca Mountain, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Moyer, T.C.; Geslin, J.K. [Science Applications International Corp., Las Vegas, NV (United States)


    Lithostratigraphic relations within the Calico Hills Formation and Prow Pass Tuff (Crater Flat Group) were reconstructed from analysis of core samples and observation of outcrop exposures. The Calico Hills Formation is composed of five nonwelded pyroclastic units (each formed of one or more pyroclastic-flow deposits) that overlie an interval of bedded tuff and a basal volcaniclastic sandstone unit. The Prow Pass Tuff is divided into four pyroclastic units and an underlying interval of bedded tuff. The pyroclastic units of the Prow Pass Tuff are distinguished by the sizes and amounts of their pumice and lithic clasts and their degree of welding. Pyroclastic units of the Prow Pass Tuff are distinguished from those of the Calico Hills Formation by their phenocryst assemblage, chemical composition, and ubiquitous siltstone lithic clasts. Downhole resistivity tends to mirror the content of authigenic minerals, primarily zeolites, in both for-mations and may be useful for recognizing the vitric-zeolite boundary in the study area. Maps of zeolite distribution illustrate that the bedded tuff and basal sandstone units of the Calico Hills Formation are altered over a wider area than the pyroclastic units of both the Calico Hills Formation and the upper Prow Pass Tuff.

  20. New 1.5 million-year-old Homo erectus maxilla from Sangiran (Central Java, Indonesia). (United States)

    Zaim, Yahdi; Ciochon, Russell L; Polanski, Joshua M; Grine, Frederick E; Bettis, E Arthur; Rizal, Yan; Franciscus, Robert G; Larick, Roy R; Heizler, Matthew; Aswan; Eaves, K Lindsay; Marsh, Hannah E


    Sangiran (Solo Basin, Central Java, Indonesia) is the singular Homo erectus fossil locale for Early Pleistocene Southeast Asia. Sangiran is the source for more than 80 specimens in deposits with (40)Ar/(39)Ar ages of 1.51-0.9 Ma. In April 2001, we recovered a H. erectus left maxilla fragment (preserving P(3)- M(2)) from the Sangiran site of Bapang. The find spot lies at the base of the Bapang Formation type section in cemented gravelly sands traditionally called the Grenzbank Zone. Two meters above the find spot, pumice hornblende has produced an (40)Ar/(39)Ar age of 1.51 ± 0.08 Ma. With the addition of Bpg 2001.04, Sangiran now has five H. erectus maxillae. We compare the new maxilla with homologs representing Sangiran H. erectus, Zhoukoudian H. erectus, Western H. erectus (pooled African and Georgian specimens), and Homo habilis. Greatest contrast is with the Zhoukoudian maxillae, which appear to exhibit a derived pattern of premolar-molar relationships compared to Western and Sangiran H. erectus. The dental patterns suggest distinct demic origins for the earlier H. erectus populations represented at Sangiran and the later population represented at Zhoukoudian. These two east Asian populations, separated by 5000 km and nearly 800 k.yr., may have had separate origins from different African/west Eurasian populations.

  1. SURFACE AREA AND MICRO-ROUGHNESS OF VOLCANIC ASH PARTICLES: A case study, Acigol Volcanic Complex, Cappadocia, Central Turkiye (United States)

    Ersoy, O.; Aydar, E.; Sen, E.; Atici, G.


    Every single ash particle may convey information about its own formation environment and conditions. Certain features on particles may give a hint about the fragmentation regime, the intensity of fragmentation and quantity of water that partakes in the fragmentation process, etc. On this account, this study majored in the analysis on finer pyroclastic material, namely volcanic ash particles. Here, we used volcanic ash particles from Quaternary Acigol Volcanic complex (West of Nevsehir, Cappadocia, Central Turkiye). Quaternary Acigol Volcanic complex lies between the towns of Nevsehir and Acigol. It consists of a shallow caldera, a thick pyroclastic apron, seven obsidian dome clusters, and scattered cinder cones and associated lavas (Druitt et al., 1995). The products of explosive volcanism of the region were distinguished as two main Quaternary tuffs by a recent study (Druitt et al., 1995). Samples are from ashfall beds in a sequence of intercalated pumice fall, ashfall, and ignimbrite beds. In this study in order to achieve surface properties of volcanic ash particles, surface areas and micro-roughness of ash particles were measured on digital elevation models (DEM) reconstructed from stereoscopic images acquired on Scanning Electron Microscope (SEM) at varying specimen tilt angles. Correlation between surface texture of volcanic ash particles and eruption characteristics was determined.

  2. Spectroscopic and Microscopic Characterization of Volcanic Ash from Puyehue-(Chile Eruption: Preliminary Approach for the Application in the Arsenic Removal

    Directory of Open Access Journals (Sweden)

    Irma Lia Botto


    Full Text Available Volcanic ash from Puyehue Cordon Caulle Volcanic Complex (Chile, emitted on June 4, 2011, and deposited in Villa La Angostura at ~40 km of the source, was collected and analyzed by Raman spectroscopy, optical and scanning electron microscopy (SEM-EDS, X-ray diffraction (XRD, surface area (BET, and chemical analysis (ICP-AES-MS technique. The mineralogical and physicochemical study revealed that the pyroclastic mixture contains iron oxides in the form of magnetite and hematite as well as pyroxene and plagioclase mineral species and amorphous pumiceous shards. Carbonaceous material was also identified. Physicochemical techniques allow us to select two representative samples (average composition and Fe-rich materials which were used to analyze their performances in the adsorption process to remove arsenic from water. Additional iron activation by means of ferric salts was performed under original sample. Results showed that the low-cost feedstock exhibited a good adsorption capacity to remove the contaminant, depending on the iron content and the water pH.

  3. A chemostratigraphic study of the Campanian Ignimbrite eruption (Campi Flegrei, Italy): Insights on magma chamber withdrawal and deposit accumulation as revealed by compositionally zoned stratigraphic and facies framework (United States)

    Fedele, L.; Scarpati, C.; Sparice, D.; Perrotta, A.; Laiena, F.


    Petrochemical analyses of juvenile samples from twenty stratigraphic sections of the Campanian Ignimbrite medial deposits, located from 30 to 79 km from the vent, are presented here. Sampling has accurately followed a well-defined stratigraphic framework and the new component facies scheme. The Campanian Ignimbrite succession is formed by a basal plinian pumice fall deposit, overlain by a complex architecture of pyroclastic density current deposits emplaced from a single sustained pyroclastic density current through a mechanism of vertical and lateral accretion. The deposit is broadly zoned, from more evolved trachyte at its base to less evolved trachyte at its top, and is similarly less evolved with increasing distance from the area of emission. Irregular chemical trends are locally observed and interpreted to represent only a limited, "patchy" record of the entire vertical geochemical trend. The petrochemical variation observed horizontally was ascribed to changes in the flow dynamics and interaction between the advancing flow and the underlying topography. The results of this study were used to propose a unified volcanological-petrological model for the Campanian Ignimbrite eruption, taking into account the emplacement of both the proximal (i.e., the "Breccia Museo" formation) and medial deposits.

  4. Repeated volcanic disasters in Prehispanic time at Popocatépetl, central Mexico: Past key to the future? (United States)

    Siebe, Claus; Abrams, Michael; Macías, José Luis; Obenholzner, Johannes


    The Holocene eruptive history of Popocatépetl volcano is characterized by recurrent voluminous Plinian eruptions every 1000 to 3000 yr, the most recent of which destroyed human settlements. Major eruptions occurred between 3195 and 2830 B.C., 800 and 215 B.C., and A.D. 675 and 1095. The three eruptions followed a similar pattern and started with minor ash fall and ash flows. The eruptions reached their peak with a main Plinian pulse that produced deposition of a pumice fall, the emplacement of hot ash flows, and finally extensive mudflows. Each time the area of devastation had become repopulated, before being devastated once again. During the last eruption several settlements, including Cholula (a major urban center), were inundated by lahars. A scenario of the possible recurrence of an eruption of similar magnitude, which would have disastrous consequences for the now highly populated areas around Popocatépetl, should be considered seriously in any volcano emergency contingency plan. This is especially important because more than one million people are living within a radius of 35 km around the volcano (the outskirts of Mexico City are at a distance of 40 km), and Popocatépetl resumed emitting ash on December 21, 1994, after decades of dormancy.

  5. The contaminant removal efficiency of an air cleaner using the adsorption/desorption effect

    Energy Technology Data Exchange (ETDEWEB)

    Matsumoto, Hiroshi [Toyohashi University of Technology, 1-1 Hibariga-oka, Tempakucho, Toyohashi 441-8580 (Japan); Shimizu, Masayuki [Sala Housing Corporation, Toyohashi 441-8021 (Japan); Sato, Hiroyasu [TOENEC Corporation, Nagoya 460-0008 (Japan)


    The adsorption and desorption of volatile organic compounds (VOCs) in relation to material surfaces were conducted to control indoor air quality. The VOC removal performance of building materials using sorption effects was validated in cases related to poor indoor air quality that occurred during non-ventilation periods during intermittent-ventilation situations. The objective of this investigation is to present the contaminant removal efficiency and practicality of a prototype air cleaner which uses sorption effects. Toluene and formaldehyde were used as pollutant sources and were continuously emitted into the test chamber. Effects due to the number of sorption units, operation time and mode of contaminant removal performance were examined. The sorption materials evaluated in this investigation were a porous material, zeolite, pumice stone and hydro-corn. As a result of the experiments, zeolite exhibited relatively high contaminant removal efficiency with toluene, and zeolite and the porous material exhibited high removal efficiency with formaldehyde for both one-cycle and two-cycle sorption modes. Moreover, significant removal performances were observed in the numerical analysis of the continuous-operation mode. (author)

  6. Confirmation of a late middle Pleistocene age for the Omo Kibish 1 cranium by direct uranium-series dating. (United States)

    Aubert, Maxime; Pike, Alistair W G; Stringer, Chris; Bartsiokas, Antonis; Kinsley, Les; Eggins, Stephen; Day, Michael; Grün, Rainer


    While it is generally accepted that modern humans evolved in Africa, the specific physical evidence for that origin remains disputed. The modern-looking Omo 1 skeleton, discovered in the Kibish region of Ethiopia in 1967, was controversially dated at ~130 ka (thousands of years ago) by U-series dating on associated Mollusca, and it was not until 2005 that Ar-Ar dating on associated feldspar crystals in pumice clasts provided evidence for an even older age of ~195 ka. However, questions continue to be raised about the age and stratigraphic position of this crucial fossil specimen. Here we present direct U-series determinations on the Omo 1 cranium. In spite of significant methodological complications, which are discussed in detail, the results indicate that the human remains do not belong to a later intrusive burial and are the earliest representative of anatomically modern humans. Given the more archaic morphology shown by the apparently contemporaneous Omo 2 calvaria, we suggest that direct U-series dating is applied to this fossil as well, to confirm its age in relation to Omo 1. Copyright © 2012 Elsevier Ltd. All rights reserved.

  7. Young cumulate complex beneath Veniaminof caldera, Aleutian arc, dated by zircon in erupted plutonic blocks (United States)

    Bacon, Charles R.; Sisson, Thomas W.; Mazdab, Frank K.


    Mount Veniaminof volcano, Alaska Peninsula, provides an opportunity to relate Quaternary volcanic rocks to a coeval intrusive complex. Veniaminof erupted tholeiitic basalt through dacite in the past ˜260 k.y. Gabbro, diorite, and miarolitic granodiorite blocks, ejected 3700 14C yr B.P. in the most recent caldera-forming eruption, are fragments of a shallow intrusive complex of cumulate mush and segregated vapor-saturated residual melts. Sensitive high-resolution ion microprobe (SHRIMP) analyses define 238U-230Th isochron ages of 17.6 ± 2.7 ka, 5 +11/-10 ka, and 10.2 ± 4.0 ka (2σ) for zircon in two granodiorites and a diorite, respectively. Sparse zircons from two gabbros give 238U-230Th model ages of 36 ± 8 ka and 26 ± 7 ka. Zircons from granodiorite and diorite crystallized in the presence of late magmatic aqueous fluid. Although historic eruptions have been weakly explosive Strombolian fountaining and small lava effusions, the young ages of plutonic blocks, as well as late Holocene dacite pumice, are evidence that the intrusive complex remains active and that evolved magmas can segregate at shallow levels to fuel explosive eruptions.

  8. SHRIMP U-Pb dating of the preeruption growth history of zircons from the 340 ka Whakamaru Ignimbrite, New Zealand: Evidence for >250 k.y. magma residence times (United States)

    Brown, Stuart J. A.; Fletcher, Ian R.


    The Whakamaru group ignimbrites are products of one of the largest caldera-forming eruptions from the central Taupo Volcanic Zone, New Zealand, ca. 340 ka. Imaging of zircons separated from low-silica rhyolite pumice from Whakamaru group ignimbrite reveals a complex magmatic crystallization history; some grains contain resorbed cores. Cores and rims of individual zircons were dated using the sensitive high-resolution ion microprobe. Due to the high U contents of the zircons, 206Pb count rates were sufficiently high to obtain 206Pb/238U ages with precisions of 5% 10% (1 σS) using longer than usual 206Pb+ count times, and this has allowed zircon core and rim ages to be distinguished. Zircon rim and outer growth zone ages range from within 1 σS error of the eruption age to 449 ± 20 ka, whereas zircon cores produced ages to 608 ± 20 ka, indicating magmatic residence times exceeding 250 k.y. for some zircons. The data are consistent with a prolonged evolution of the magma system over hundreds of thousands of years, involving magma replenishment and mixing with residual phases of older silicic magma chambers, in addition to crystal fractionation processes, prior to eruption. The study has shown that 206Pb/238U dating using high-resolution ion microprobe can be used to determine zircon preeruptive growth histories in Quaternary lavas and pyroclastic rocks.

  9. Pleistocene volcaniclastic units from North-Eastern Sicily (Italy): new evidence for calc-alkaline explosive volcanism in the Southern Tyrrhenian Sea (United States)

    Di Bella, Marcella; Italiano, Francesco; Sabatino, Giuseppe; Tripodo, Alessandro; Baldanza, Angela; Casella, Sergio; Pino, Paolo; Rasa', Riccardo; Russo, Selma


    A well-preserved volcaniclastic sequence crops out in Pleistocene marine sediments along the Tyrrhenian coastline of the Calabrian-Peloritani arc (Sicily, Italy), testifying the occurrence of Lower-Middle Pleistocene volcanic activity in Southern Tyrrhenian Sea. The presence of dominant highly vesicular and minor blocky glassy particles indicates that the volcanic clasts were originated by explosive events related to the ascent and violent emission of volatile-rich magmas accompanied by and/or alternated with hydromagmatic fragmentation due to magma-sea water interaction. Field investigations and sedimentological features of the studied volcaniclastic units suggest a deposition from sediment-water density flows. The chemical classification of the pumice clasts indicates prevalent rhyolitic and dacitic compositions with calc-alkaline to high-K calc-alkaline affinity. The geochemical features of immobile trace elements together with the presence of orthopyroxene are indicative of a provenance from an arc-type environment. The age (from 980-910 to 589 ka), the chemical composition and the evidence of subaerial explosive volcanic activity constrain the origin nature and temporal evolution of the arc-type volcanism in the Southern Tyrrhenian domain. Finally, the new information here provided contribute to a better understanding of the temporal geodynamic evolution of this sector of the Mediterranean domain.

  10. Human corpses as time capsules: new perspectives in the study of past mass disasters. (United States)

    Petrone, Pier Paolo


    Looking at the corpses of past natural catastrophes can change completely the conception of how to study human bone remains. The recovery of the Herculaneum victims of the 79 AD Vesuvius eruption was an opportunity for me to adopt a new approach in the study of human skeletons and their context of discovery. During two years of field work, my first aim was to investigate the effects of pyroclastic surges on people and things. The conservation of skeletons and their replacement by fiberglass casts were also provided. This "field laboratory" has developed into a palaeoforensic investigation of the mass disaster caused by the 79 AD natural event. Field and laboratory research, later extended to Pompeii plaster-cast corpses, were also carried out on the victims' remains, footprints, huts and objects found in the sites buried by the prehistoric "Avellino pumices" eruption (3780 ± 100 BP). The new results obtained from the study of the causes of death of people hit by pyroclastic surges produced by past Vesuvius eruptions have proved essential in hazard evaluation in the Neapolitan district and other volcanic areas.

  11. Tephrochronology of a 72 ka-long marine record: implications for the southern Tyrrhenian explosive volcanism (United States)

    Tamburrino, Stella; Insinga, Donatella; Pelosi, Nicola; Kissel, Catherine; Laj, Carlo; Capotondi, Lucilla; Sprovieri, Mario


    Several discrete tephra layers occur in a Marion Dufresne 13.9 m-long deep-sea core (MD01-2474G) from the southern Tyrrhenian Sea. Major, minor and trace element data (EMPA-WDS and LA-ICP-MS analyses) from fresh micro-pumices and glass shards allow to correlate them with the volcanic activity from Aeolian Islands (Lipari, Vulcano, Salina), Campanian Plain (Ischia), Pantelleria and Mt. Etna. The chronology of the succession is provided by a high-resolution age-model based on isotope stratigraphy and AMS radiocarbon dating, which places the succession in a time interval spanning the last 72 kyrs BP. According to a detailed proximal-distal and distal-distal correlation, a precise chronological framework is established and some main markers tephras of the central Mediterranean area (Y-1, Y-6, Y-7 and Y-8) are recognised. In additions, the succession is a precious archive to record multiple volcanic events occurred at Ischia volcano and the Aeolian Arc (Lipari and Vulcano). This latter, in particular, erupted several products which exhibits strong compositional variations otherwise non detectable from terrestrial counterparts. The results of the present study, hence, provide new data for a detailed analytical reference database of the Tyrrhenian Sea tephrochronology and may contribute to a better chronostratigraphic reconstruction of the Aeolian arc explosive events.

  12. On the properties of the pyroclastic deposit in Fukushima prefecture as a raw material of teh micro shirasuballoons. Biryu shirasuballoon no genryo to shite no Fukushimakensan shirado no tekisei shiken

    Energy Technology Data Exchange (ETDEWEB)

    Kimura, K. (Government Industrial Research Institute, Kyushu, Fukuoka (Japan)); Jinnai, K. (Kagoshima Prefectural Industrial Technology Center, Kagoshima (Japan))


    Properties of the pyroclastic deposit in Fukushima Prefecture, Japan were studied from the viewpoint as raw material of micro shirasuballoons. The pyroclastic deposit was composed of shirasu and natural glass like pearlite including crystalline minerals in some specimens. Weathered surfaces effective in thermal foaming were scarcely found in a grain size range over 10 {mu}m, and there was no effect of grain size on bulk density or grain density because of nearly no existence of pumice grains. Because there were much massive glass and less thin plane glass most suitable as raw material of micro shirasuballoons in the pyroclastic deposit, multi-foamed grains were probably formed by thermal foaming. Because specimens including only grains below 10 {mu}m in size were scarcely foamed, the least grain size suitable for the raw material seemed to be 10 {mu}m. The shirasuballoons recovered from specimens offered lower recovery rates in spite of both their sufficient densities and higher strengths. 5 refs., 13 figs., 6 tabs.

  13. Effect of adhesive remnant removal on enamel topography after bracket debonding

    Directory of Open Access Journals (Sweden)

    Larissa Adrian Meira Cardoso


    Full Text Available INTRODUCTION: At orthodontic treatment completion, knowledge about the effects of adhesive remnant removal on enamel is paramount.OBJECTIVE: This study aimed at assessing the effect of different adhesive remnant removal methods on enamel topography (ESI and surface roughness (Ra after bracket debonding and polishing.METHODS: A total of 50 human premolars were selected and divided into five groups according to the method used for adhesive remnant removal: high speed tungsten carbide bur (TCB, Sof-Lex discs (SL, adhesive removing plier (PL, ultrasound (US and Fiberglass burs (FB. Metal brackets were bonded with Transbond XT, stored at 37oC for 24 hours before debonding with adhesive removing plier. Subsequently, removal methods were carried out followed by polishing with pumice paste. Qualitative and quantitative analyses were conducted with pre-bonding, post-debonding and post-polishing analyses. Results were submitted to statistical analysis with F test (ANOVA and Tukey's (Ra as well as with Kruskal-Wallis and Bonferroni tests (ESI (P < 0.05.RESULTS: US Ra and ESI were significantly greater than TCB, SL, PL and FB. Polishing minimized Ra and ESI in the SL and FB groups.CONCLUSION: Adhesive remnant removal with SL and FB associated with polishing are recommended due to causing little damage to the enamel.

  14. Hourglass inclusions: Theory and application to the Bishop rhyolitic tuff

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, A.T. Jr. (Univ. of Chicago, IL (United States))

    Hourglass inclusions are bodies of bubble-bearing glass in volcanic phenocrysts that extend to the crystal rim through a narrow neck. Compared to enclosed inclusions, hourglass inclusions are less devitrified, contain more gas, but contain less dissolved H{sub 2}O, CO{sub 2}, and Cl. A quantitative model of rhyolitic hourglass emptying is developed and applied to Bishop Tuff hourglass inclusions. Those in plinian pumice suggest rapid ascent at 10 m/s consistent with theoretical eruption models. Hourglass inclusions from the Mono ash-flow lobe of the Bishop Tuff suggest (1) initial crystallization of quartz, formation of some enclosed and some hourglass inclusions at approximately 2,400 bars; (2) magma decompression to approximately 1,100 bars for at least a week (duration of eruption for the Bishop Tuff ) while hourglass inclusions further evolved and bubbles of gas attained a 50{mu}m diameter; (3) magma ascent from 1,100 to approximately 700 bars at approximately 1 m/s, consistent with theory for ash-flow-producing (collapsing) eruption columns; (4) entrainment of some crystals that had decompressed to a pressure of 400 bars for several weeks; (5) thermal quenching of hourglass evolution as magmatic foam disrupted into fast-moving spray, erupted, and entrained cold air. Uncertainties are large but can be reduced by future studies of postdepositional cooling, hourglass volatile compositions, temperature, and viscosity to obtain estimates of eruptive and preeruptive magma movement and crystallization rate.

  15. [Combination of phosphorus solubilizing and mobilizing fungi with phosphate rocks and volcanic materials to promote plant growth of lettuce (Lactuca sativa L.)]. (United States)

    Velázquez, María S; Cabello, Marta N; Elíades, Lorena A; Russo, María L; Allegrucci, Natalia; Schalamuk, Santiago


    Arbuscular mycorrhizal fungi (AMF) increase the uptake of soluble phosphates, while phosphorus solubilizing fungi (S) promote solubilization of insoluble phosphates complexes, favoring plant nutrition. Another alternative to maintaining crop productivity is to combine minerals and rocks that provide nutrients and other desirable properties. The aim of this work was to combine AMF and S with pyroclastic materials (ashes and pumices) from Puyehue volcano and phosphate rocks (PR) from Rio Chico Group (Chubut) - to formulate a substrate for the production of potted Lactuca sativa. A mixture of Terrafertil®:ashes was used as substrate. Penicillium thomii was the solubilizing fungus and Rhizophagus intraradices spores (AMF) was the P mobilizer (AEGIS® Irriga). The treatments were: 1) Substrate; 2) Substrate+AMF; 3) Substrate+S; 4) Substrate+AMF+S; 5) Substrate: PR; 6) Substrate: PR+AMF; 7) Substrate: PR+S and 8) Substrate: PR+AMF+S. Three replicates were performed per treatment. All parameters evaluated (total and assimilable P content in substrate, P in plant tissue and plant dry biomass) were significantly higher in plants grown in substrate containing PR and inoculas with S and AMF. This work confirms that the combination of S/AMF with Puyehue volcanic ashes, PR from the Río Chico Group and a commercial substrate promote the growth of L. sativa, thus increasing the added value of national geomaterials. Copyright © 2017 Asociación Argentina de Microbiología. Publicado por Elsevier España, S.L.U. All rights reserved.

  16. How to associate with volcanoes. Mitigation of volcanic hazards; Kazan tono tsukiaikata. Kazan saigai wo doyatte herasuka

    Energy Technology Data Exchange (ETDEWEB)

    Kawabe, Y. [Geological Survey of Japan, Tsukuba (Japan)


    This paper describes how to deal with volcanic hazards. Basaltic lave such as in the Kilauea volcano flows quickly, while andesite lava such as in Mt. Asama and Mt. Sakurajima in Japan flows slowly. The pyroclastic flow in the Unzen area was a flow of high-temperature lava, pumice stones and gas driven to a high speed by gravity. The flow is so dangerous as it flows so quickly as allowing no time to escape from. Pyroclastic fall-outs and volcanic gases also give damages of different forms. Mountain collapse and debris avalanche in which a volcanic mountain collapses by eruption and earthquake acting as a trigger can also cause a large disaster. A debris flow may also do the same. Knowing the history of volcanic activities by making geological surveys may help judge what type of eruptive activities is prone to occur. On the other hand, the current conditions must be kept observed by performing seismic observations. Eruption itself, a large-scale lava flow and a pyroclastic flow cannot be prevented by using any hardware technique. Software measures are important to utilize more adequately areas and soil natures with high risks. The National Land Agency has prepared recently a guideline for making hazard prediction maps. It is important that both the administration and general residents utilize this guideline. 11 refs., 3 figs., 3 tabs.

  17. Orthodontic bracket bonding to glazed full-contour zirconia (United States)

    Kwak, Ji-Young; Jung, Hyo-Kyung; Choi, Il-Kyung


    Objectives This study evaluated the effects of different surface conditioning methods on the bond strength of orthodontic brackets to glazed full-zirconia surfaces. Materials and Methods Glazed zirconia (except for the control, Zirkonzahn Prettau) disc surfaces were pre-treated: PO (control), polishing; BR, bur roughening; PP, cleaning with a prophy cup and pumice; HF, hydrofluoric acid etching; AA, air abrasion with aluminum oxide; CJ, CoJet-Sand. The surfaces were examined using profilometry, scanning electron microscopy, and electron dispersive spectroscopy. A zirconia primer (Z-Prime Plus, Z) or a silane primer (Monobond-S, S) was then applied to the surfaces, yielding 7 groups (PO-Z, BR-Z, PP-S, HF-S, AA-S, AA-Z, and CJ-S). Metal bracket-bonded specimens were stored in water for 24 hr at 37℃, and thermocycled for 1,000 cycles. Their bond strengths were measured using the wire loop method (n = 10). Results Except for BR, the surface pre-treatments failed to expose the zirconia substructure. A significant difference in bond strengths was found between AA-Z (4.60 ± 1.08 MPa) and all other groups (13.38 ± 2.57 - 15.78 ± 2.39 MPa, p application of silane to the cleaned surface is recommended. A zirconia primer should be used only when the zirconia substructure is definitely exposed. PMID:27200278

  18. The Novarupta-Katmai eruption of 1912 - largest eruption of the twentieth century; centennial perspectives (United States)

    Hildreth, Wes; Fierstein, Judy


    The explosive outburst at Novarupta (Alaska) in June 1912 was the 20th century's most voluminous volcanic eruption. Marking its centennial, we illustrate and document the complex eruptive sequence, which was long misattributed to nearby Mount Katmai, and how its deposits have provided key insights about volcanic and magmatic processes. It was one of the few historical eruptions to produce a collapsed caldera, voluminous high-silica rhyolite, wide compositional zonation (51-78 percent SiO2), banded pumice, welded tuff, and an aerosol/dust veil that depressed global temperature measurably. It emplaced a series of ash flows that filled what became the Valley of Ten Thousand Smokes, sustaining high-temperature metal-transporting fumaroles for a decade. Three explosive episodes spanned ~60 hours, depositing ~17 km3 of fallout and 11±2 km3 of ignimbrite, together representing ~13.5 km3 of zoned magma. No observers were nearby and no aircraft were in Alaska, and so the eruption narrative was assembled from scattered villages and ship reports. Because volcanology was in its infancy and the early investigations (1915-23) were conducted under arduous expeditionary conditions, many provocative misapprehensions attended reports based on those studies. Fieldwork at Katmai was not resumed until 1953, but, since then, global advances in physical volcanology and chemical petrology have gone hand in hand with studies of the 1912 deposits, clarifying the sequence of events and processes and turning the eruption into one of the best studied in the world. To provide perspective on this century-long evolution, we describe the geologic and geographic setting of the eruption - in a remote, sparsely inhabited wilderness; we review the cultural and scientific contexts at the time of the eruption and early expeditions; and we compile a chronology of the many Katmai investigations since 1912. Products of the eruption are described in detail, including eight layers of regionwide fallout

  19. Effect of two bleaching agents on enamel morphology: a SEM study

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    Ghavam M.


    Full Text Available Statement of Problem: Bleaching materials are able to change the surface morphology as well as mineral and organic content of tooth structure. Considering that bleaching is done for aesthetic purpose, awareness of the possible effect of these materials on hard tissue is important, because it may affect the restorative treatments. Purpose: The aim of this study was comparing the effect of two bleaching materials, Kimia and Ultradent both containing 35% H2O2, on tooth enamel by SEM. Materials and Methods: Five intact central incisors were cut into three sections vertically and each part was randomly divided into three groups. Group 1 (control, without any bleaching. Group 2, bleached with Kimia 35% H2O2. Group 3, bleached with Ultradent 35% H2O2. Each tooth served as its own control. Then the samples were observed by SEM with 250 and 500 magnifications. Results: In the control group some scratches and small white grains were observed which seems to be the result of mastication trauma and pumice powder. In the other groups, morphologic changes like increased surface roughness, deepening of cracks, rod exposure and presence of new cracks were observed. The two experimental materials did not differ in these regards. Conclusion: It seems that both studied materials have limited destructive effects on tooth enamel which seems to be of no clinical importance.

  20. Material and elastic properties of Al-tobermorite in ancient roman seawater concrete

    KAUST Repository

    Jackson, Marie D.


    The material characteristics and elastic properties of aluminum-substituted 11 Å tobermorite in the relict lime clasts of 2000-year-old Roman seawater harbor concrete are described with TG-DSC and 29Si MAS NMR studies, along with nanoscale tomography, X-ray microdiffraction, and high-pressure X-ray diffraction synchrotron radiation applications. The crystals have aluminum substitution for silicon in tetrahedral bridging and branching sites and 11.49(3) Å interlayer (002) spacing. With prolonged heating to 350°C, the crystals exhibit normal behavior. The experimentally measured isothermal bulk modulus at zero pressure, K0, 55 ±5 GPa, is less than ab initio and molecular dynamics models for ideal tobermorite with a double-silicate chain structure. Even so, K0, is substantially higher than calcium-aluminum-silicate-hydrate binder (C-A-S-H) in slag concrete. Based on nanoscale tomographic study, the crystal clusters form a well connected solid, despite having about 52% porosity. In the pumiceous cementitious matrix, Al-tobermorite with 11.27 Å interlayer spacing is locally associated with phillipsite, similar to geologic occurrences in basaltic tephra. The ancient concretes provide a sustainable prototype for producing Al-tobermorite in high-performance concretes with natural volcanic pozzolans. © 2013 The American Ceramic Society.

  1. Spatial distribution of damage around faults in the Joe Lott Tuff Member of the Mount Belknap Volcanics, Utah: A mechanical analog for faulting in pyroclastic deposits on Mars (United States)

    Okubo, Chris H.


    Volcanic ash is thought to comprise a large fraction of the Martian equatorial layered deposits and much new insight into the process of faulting and related fluid flow in these deposits can be gained through the study of analogous terrestrial tuffs. This study identifies a set of fault-related processes that are pertinent to understanding the evolution of fault systems in fine-grained, poorly indurated volcanic ash by investigating exposures of faults in the Miocene-aged Joe Lott Tuff Member of the Mount Belknap Volcanics, Utah. The porosity and granularity of the host rock are found to control the style of localized strain that occurs prior to and contemporaneous with faulting. Deformation bands occur in tuff that was porous and granular at the time of deformation, while fractures formed where the tuff lost its porous and granular nature due to silicic alteration. Non-localized deformation of the host rock is also prominent and occurs through compaction of void space, including crushing of pumice clasts. Significant off-fault damage of the host rock, resembling fault pulverization, is recognized adjacent to one analog fault and may reflect the strain rate dependence of the resulting fault zone architecture. These findings provide important new guidelines for future structural analyses and numerical modeling of faulting and subsurface fluid flow through volcanic ash deposits on Mars.

  2. Effect of Tensile Reinforcement Ratio on the Effective Moment of Inertia of Reinforced Lightweight Concrete Beams for Short Term Deflection Calculation

    Directory of Open Access Journals (Sweden)



    Full Text Available This paper presents an improvement model of the effective moment of inertia to predict the short term deflection of reinforced lightweight concrete beam. The models were developed using 9 beams of reinforced pumice-lightweight concrete tested under two symmetrical-point loads. The presence of steel reinforcement in the beam was taken into consideration in the developed model. The models were verified by test carried out on other 9 beams. Those beams subjected to various-point loads and compressive strength. The results of investigation revealed that crack moment of inertia increased with the increased tensile reinforcement ratio. Thus, the reinforcement ratio significantly affects the value of effective moment of inertia of reinforced lightweight concrete beam. All the beam test results produced considerable deflection in comparison to that obtained using current Codes either ACI or SNI. The proposed model demonstrated a good agreement to the experimental results and in some cases have similar trend to that of the ACI or SNI prediction.

  3. Comparative study of resin sealant and resin modified glass ionomer as pit and fissure sealant

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    Shirin Malek


    Full Text Available The purpose of the present study was to compare the marginal integrity of resin modified glass ionomer cement with that of resin sealant, in vitro. Forty artificial pit and fissure cavities were prepared in occlusal surface of extracted premolar teeth by using ¼ round carbide bur. Cavities were condensed with artificial organic debris followed by cleaning with prophylaxis pumice brush and paste and then separated into two treatment groups. In Group A, 15 fissure cavities were sealed by resin sealant and in Group B, 15 fissure cavities were sealed by resin modified glass ionomer sealant. These specimens were subjected to thermo-cycling followed by dye penetration test. The remaining 5 cavities from each group were analyzed for debris score by the SEM. The results of the microleakage test showed that the efficacy of preventing microleakage of samples sealed by resin modified glass ionomer sealant was higher than the samples sealed by resin sealant. However, no significant differences were found. It can be concluded that use of resin modified glass ionomer sealant is a good alternative for sealing pits and fissures.

  4. 生物栅-复合人工湿地系统对黑臭河水的中试处理%Pilot Scale Experiment of Malodorous River Water Treatment Combined with Biofilm Grid and Integrated Vertical Flow Constructed Wetlands(BFG-IVCWs)

    Institute of Scientific and Technical Information of China (English)

    潘震; 张勇; 黄民生; 何岩; 程庆霖


    Considering low dissolved oxygen and heavy organic pollution in malodorous river water, biofilm grid technology and integrated vertical flow constructed wetlands (BFG-IVCWs) was used to purify malodorous river water. The results of experiments show that fiber filter on COD removal rate is 30 %~40 %, wetland on COD removal rate is 45 %, the effect of Pontederia cordata and Pumice on COD removal is obvious. During operation of the system, TP removal rate is 58.13 %~83.25 %, TN removal efficiency is much better in early operation, which is 58.14 %.%针对黑臭河水溶解氧极低、有机物污染重的特点,充分利用生物栅技术和人工湿地技术组合而成生物栅-复合人工湿地系统(BFG-IVCWs),来净化黑臭河水降低COD等污染物质.试验结果表明:软性填料槽对COD的去除率为30%~40%,人工湿地对COD的去除率保持在45%,梭鱼草及蜂巢石对COD去除效果明显.该系统运行期间TP去除率为58.13%~83.25%,对TN去除效果初期较好,达到58.14%.

  5. Moisture Transfer in Concrete: Numerical Determination of the Capillary Conductivity Coefficient

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    Simo Elie


    Full Text Available We numerically investigated moisture transfer in buildings made of concrete. We considered three types of concrete: normal concrete, pumice concrete and cellular concrete. We present the results of a 1-D liquid water flow in such materials. We evaluated the moisture distribution in building materials using the Runge-Kutta fourth-and-fifth-order method. The DOPRI5 code was used as an integrator. The model calculated the resulting moisture content and other moisture-dependent physical parameters. The moisture curves were plotted. The dampness data obtained was utilized for the numerical computation of the coefficient of the capillary conductivity of moisture. Different profiles of this coefficient are represented. Calculations were performed for four different values of the outdoor temperature: -5°C, 0°C, 5°C and 10°C. We determined that the curves corresponding to small time intervals of wetting are associated with great amplitudes of the capillary conductivity . The amplitudes of the coefficient of the capillary conductivity decrease as the time interval increases. High outdoor temperatures induce high amplitudes of the coefficient of the capillary conductivity.

  6. A Study on the Forming Conditions of Basalts in Seamounts of the South China Sea

    Institute of Scientific and Technical Information of China (English)

    李兆麟; 梁德华; 等


    Volcanic rocks in seamounts of the South China Sea consist mainly of alkali basalt, tholeiitic basalt, trachyandesitic pumice, dacite, etc.Inclusions in the minerals of the volcanic rocks are main-ly amorphors melt inclusions, which reflects that the volcanic rocks are characterized by submarine eruption and rapid cooling on the seafloor .Furthermore, fluid-melt inclusions have been discovered for the first time in alkali basalts and mantle-derived xenoliths,indicating a process of differentiation between magma and fluid in the course of mantle partial melting .Alkali basalts and inclusions may have been formed in this nonhomogeneous system.Rock-forming temperatures of four seamouns estimated as follows:the Z hongnan seamount alkali basalt 1155-1185℃; the Xianbei seamount alkali basalt 960-1200℃; tholeiitic basalt 1040-1230℃; the Daimao seamount tholeiitic basalt 1245-1280℃; and the Jianfeng seamount trachandestic prmice 880-1140℃. Equilibrium pressures of alkali basalts in the Zhongnan and Xianbei seamounts are 13.57 and 8.8×108 Pa ,respectively. Pyroxene equilibrium tem-peratures of mantle xenoliths from the Xianbei seamount were estimated at 1073-1121℃, and pres-sures ar (15.58-22.47)×108Pa, suggesting a deep-source (e.g.the asthenosphere )for the alkalibasalts.

  7. Green roofs in Germany : yesterday, today and tomorrow

    Energy Technology Data Exchange (ETDEWEB)

    Herman, R. [Anhalt Univ., Bernburg (Germany)


    This presentation provided a historical overview of the development of green roofs in Germany. Real interest in green roof technology in Germany began in the 1970s at which time specific guidelines for correct installation were established. In the past 20 years there has been a dramatic increase in the number of green roofs. The main market drivers were ecological concerns, energy and cost saving potential, as well as the need to manage storm water. Green roofs have an insulating effect, leading to energy savings. Some cities in Germany have implemented an incentive program whereby reductions on city water fees are allocated to owners of green roofs. Many business opportunities have been created by an increased interest in green roofs. The demand for lava, pumice, expanded clay, recycled roof tiles, crushed brick and other materials is being met by a new industry. There has been a noted increase in green roof systems and components, as well as installation and maintenance companies. It is expected that the ever increasing price for land in German cities along with an increasing population density will spur an even greater demand for green roofs. Germany is considered one of the greenest countries in the world, due to public concern for all forms of pollution, the maintenance of ecological balance, the preservation of flora and fauna, and a respect for nature. 6 refs.


    Directory of Open Access Journals (Sweden)

    Catur Wasonowati


    Full Text Available Tomato is vegetable that has high economic and nutritional value. Hydroponics is the cultivation of plants without soil but using rice husk charcoal, rockwool, pumice, sand, gravel, perlite water and air media. This research aims to study the effect of nutrients and polybag size on growth and yield of hydroponic tomatoes. The experiment was conducted in Kassa House of Agroekoteknologi Departement Faculty of Agriculture Trunojoyo University. Fertilizers used were Hidrogroup and Greentonik while polybag size are 30x30 cm, 30x40 cm and 40x40 cm. The design of this study using Complete Randomized Design (CRD with 3 replications. The result showed that this research affect to the vegetative phase. No interaction between type of nutrition and polybag size on plant height, leaf number, stem diameter, number of flowers, flowering time of tomato. Type of nutrition significantly affect plant height, leaf number, stem diameter, flower number and wet and dry weight of stems and leaves, whereas the size of polybags significantly affects in the number of leaves, wet and dry weight of stems and leaves of tomato.

  9. Lake sediments provide the first eruptive history for Corbetti, a high-risk Main Ethiopian Rift volcano (United States)

    Martin-Jones, Catherine M.; Lane, Christine S.; Pearce, Nicholas J. G.; Smith, Victoria C.; Lamb, Henry F.; Schaebitz, Frank; Viehberg, Finn; Brown, Maxwell C.; Frank, Ute; Asrat, Asfawossen


    A recent World Bank report found that 49 of Ethiopia's 65 known Holocene volcanoes pose a high-risk to the surrounding population. One of these volcanoes, Corbetti, located in the densely populated Main Ethiopian Rift (MER), has only one documented Holocene eruption. Any risk assessment for Corbetti is therefore highly uncertain. Reliable hazard forecasting is dependent on the completeness of volcanic records. In the case of Ethiopian Rift volcanoes complete records are hindered by frequently poorly exposed, buried and inaccessible proximal outcrops. Lake sediments can yield comprehensive, stratigraphically-resolved dossiers of past volcanism. Here we use volcanic ash (tephra) layers preserved in sediments from three MER lakes to provide the first record of Holocene volcanism for Corbetti. It shows that Corbetti has erupted explosively throughout the Holocene at an average return period of 800 years. Based on the thickness and dispersal of the tephras, at least six eruptions were of a large magnitude, and there were four eruptions in the past 2000 years. Future explosive eruptions are likely and these could have significant societal impacts, they could blanket nearby Awassa and Shashamene, home to 260,000 people, with pumice deposits. Our data indicate that the threat posed by Corbetti has been significantly underestimated. These data can be used to refine regional volcano monitoring and develop evacuation plans. This lake sediment-tephrostratigraphic approach shows significant potential for application throughout the East African Rift system, and is essential to understanding volcanic hazards in this rapidly developing region.

  10. Composition and diagenetic processes of sandstone and tuff deposits of the Cenomanian Cardiel Formation, Cardiel Lake area, province of Santa Cruz Composición y procesos diagenéticos de los depósitos de arenisca y toba de la Formación Cardiel (Cenomaniano, área Lago Cardiel, provincia de Santa Cruz

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    R.R. Andreis


    Full Text Available The Cardiel Formation (Cenomanian, around 200 m in thickness in the studied area, includes different types of volcaniclastic deposits, mainly represented by fine tuffs and massive bentonites, and subordinated epiclastics such as lithic sandstones of yellowish-brown, dusky yellow, or light olive hues, siltstones and claystones. Reddened paleosols with some small axial roots and weak prismatic structures appear on top of siltstones, tuffs and bentonites. Tufites and tuffs contain the same neovolcanic components, abundant glass shards and minor pumices. Different types of glass shards can be differentiated whitin this unit, whereas pumice fragments are represented by different vesicular varieties. Vitreous tuffaceous clasts are abundant in the tufites. Almost all samples contain not only diagenetically-derived, but also pedogenetically-infiltrated montmorillonite, as well as zeolites. Predominant Ca-Na-K clinoptilolite (Si/Al>4 and minor analcime (Si/Al near 3 were identified. Smectite and clinoptilolite may either replace glass-shards or pumices, or fill pore spaces, whereas smectite also appears as thin cutans. The sequence of diagenetic processes includes the conversion (hydrolysis of glass to smectite, and later to zeolites. Furthermore, zeolites preceded calcite growth (sometimes replacing glass-shards or pumices, which in turn, formed prior to pervading ferric oxides-hydroxides. The vertical distribution of zeolites can be explained taking into account the presence of percolating waters in an open hydrologic system. The zeolite content throughout the whole profile links the mineralogical association observed within the sediments of the Cardiel Formation to the clinoptilolite zone. Paleoenvironmental reconstructions for the Cardiel Formation point out to tidal currents taking place in wide lagoons; tuffaceous and bentonitic deposits covered those ancient lagoons forming wide, flat plains on which paleosols developed. Paleocurrents measured on

  11. Microabrasion: An Effective Method for Improvement of Esthetics in Dentistry

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    Biji Balan


    Full Text Available Enamel microabrasion can eliminate enamel irregularities and discoloration defects, thus improving the appearance of teeth. This paper presents the latest treatment protocol of enamel microabrasion to remove stains on the enamel surface. It has been verified that teeth submitted to microabrasion acquire a yellowish colour because of the thinness of the remaining enamel, revealing the colour of dentinal tissue to a greater degree. Enamel microabrasion is a technique that can be used to correct discoloured enamel. Enamel microabrasion was developed in the mid-1980s as a method of eliminating enamel discolouration defects and improving the appearance of teeth. Several years after the method was developed, much has been learned about this technique, long-term results of treatment, and microscopic changes to the enamel surface that have distinguishable clinical implications. In addition, certain patients can benefit from enamel microabrasion to yield attractive cosmetic results. The aim of this study was to report the clinical case of a male patient of 25 years with moderate fluorosis, whose smile was re-established by the use of an enamel microabrasion technique, with 18% hydrochloric acid and pumice slurry shown to be a safe and efficient method for removing fluorosis stains.

  12. In Vitro Comparison of Microleakage of Two Materials Used as Pit and Fissure Sealants

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    Zahra Bahrololoomi


    Full Text Available Background and aims. Marginal seal of the material is extremely important in fissure sealant therapy. The aim of this study was to investigate microleakage of flowable composite resins and conventional fissure sealants with or without dentin bonding agent. Materials and methods. The occlusal surface of 60 intact extracted human premolars, divided into four groups, were cleaned with pumice/slurry, etched with 37% phosphoric acid for 15 seconds, rinsed and dried. Groups were treated differently: Excite bonding agent followed by Helioseal F fissure sealant in group1; Helioseal F alone in group 2; Excite bonding agent followed by Tetric Flow in group 3; and Tetric Flow alone in group 4. Light-curing was done after each application. After thermocycling, the whole surface of each specimen was coated with nail varnish except for one millimeter around the fissure sealant. The teeth were immersed in 2% basic fuchsin for 24 hours and then sectioned buccolingually. The sections were analyzed for leakage under a stereomicroscope. Data was analyzed by Kruskal-Wallis and Mann-Whitney tests at a significance level of P 0.05, except for groups 2 and 4 (P = 0.002 and groups 3 and 4 (P = 0.033. Conclusion. Use of a flowable composite with bonding agent is a good alternative for sealing pits and fissures; however, further in vitro and in vivo studies are necessary.

  13. Abrasion of 6 dentifrices measured by vertical scanning interference microscopy (United States)



    Objectives The abrasion of dentifrices is well recognized to eliminate the dental plaque. The aims of this study were to characterize the abrasive powders of 6 dentifrices (3 toothpastes and 3 toothpowders) and to measure the abrasion on a test surface by Vertical Scanning Interference microscopy (VSI). Material and Methods Bright field and polarization microscopy were used to identify the abrasive particles on the crude dentifrices and after prolonged washes. Scanning electron microscopy and microanalysis characterized the shape and nature of the particles. Standardized and polished blocks of poly(methylmethacrylate) were brushed with a commercial electric toothbrush with the dentifrices. VSI quantified the mean roughness (Ra) and illustrated in 3D the abraded areas. Results Toothpastes induced a limited abrasion. Toothpowders induced a significantly higher roughness linked to the size of the abrasive particles. One powder (Gencix® produced a high abrasion when used with a standard testing weight. However, the powder is based on pumice particles covered by a plant homogenate that readily dissolves in water. When used in the same volume, or after dispersion in water, Ra was markedly reduced. Conclusion Light and electron microscopy characterize the abrasive particles and VSI is a new tool allowing the analysis of large surface of abraded materials. PMID:24212995

  14. Fall velocity of multi-shaped clasts (United States)

    Le Roux, Jacobus P.


    Accurate settling velocity predictions of differently shaped micro- or macroclasts are required in many branches of science and engineering. Here, a single, dimensionally correct equation is presented that yields a significant improvement on previous settling formulas for a wide range of clast shapes. For smooth or irregular clasts with known axial dimensions, a partially polynomial equation based on the logarithmic values of dimensionless sizes and settling velocities is presented, in which the values of only one coefficient and one exponent need to be adapted for different shapes, irrespective of the Reynolds number. For irregular, natural clasts with unknown axial dimensions, a polynomial equation of the same form is applied, but with different coefficients. Comparison of the predicted and measured settling velocities of 8 different shape classes as well as natural grains with unknown axial dimensions in liquids, representing a total of 390 experimental data points, shows a mean percentage error of - 0.83% and a combined R2 value of 0.998. The settling data of 169 differently shaped particles of pumice, glass and feldspar falling in air were also analyzed, which demonstrates that the proposed equation is also valid for these conditions. Two additional shape classes were identified in the latter data set, although the resultant equations are less accurate than for liquids. An Excel spreadsheet is provided to facilitate the calculation of fall velocities for grains settling individually and in groups, or alternatively to determine the equivalent sieve size from the settling velocity, which can be used to calibrate settling tubes.

  15. Tecuamburro Volcano, Guatemala geothermal gradient core hole drilling, operations, and preliminary results

    Energy Technology Data Exchange (ETDEWEB)

    Goff, S.; Heiken, G.; Goff, F.; Gardner, J. (Los Alamos National Lab., NM (USA)); Duffield, W. (Geological Survey, Flagstaff, AZ (USA)); Martinelli, L.; Aycinena, S. (Swissboring Overseas Corp. Ltd., Guatemala City (Guatemala)); Castaneda, O. (Unidad de Desarrollo Geotermico, Guatemala City (Guatemala). Inst. Nacional de Electrificacion)


    A geothermal gradient core hole (TCB-1) was drilled to a depth of 700+ m at the Tecuamburro geothermal site, Guatemala during February and March, 1990. The core hole is located low on the northern flank of the Tecuamburro Volcano complex. Preliminary analysis of cores (>98% core recovery) indicates that the hydrothermal system may be centered in the 4-km-diameter Chupadero Crater, which has been proposed as the source of pyroxene pumice deposits in the Tecuamburro area. TCB-1 is located 300 m south of a 300-m-diameter phreatic crater, Laguna Ixpaco; the core hole penetrates the thin edge of a tuff ring surrounding Ixpaco and zones of hydrothermal brecciation within the upper 150 m may be related to the phreatic blast, dated at 2,910 {sup 14}C years. At the time of this writing, the unequilibrated temperature at a depth of 570m was 180{degree}C. Data on fracturing, permeability, hydrothermal alteration, and temperature will be presented. 3 refs., 3 figs.

  16. REE and Sr-Nd isotope characteristics of hydrothermal chimney at Jade area in the Okinawa Trough

    Institute of Scientific and Technical Information of China (English)

    LIU Yanguang; MENG Xianwei; FU Yunxia


    Hydrothermal chimney is a product of hydrothermal activity on the seabed. Chimney samples dredged from Jade hydrothermal area in Izena depression of the Okinawa Trough, are characterized by relatively enriched light rare earth elements (LREE) and strongly positive Eu anomalies. 87Sr/86Sr and 143Nd/144Nd of these samples are exactly between those of seawater and of acidic pumice, averaged at 0.708928 and 0.512292, respectively. These characteristics imply that the main source of hydrothermal sulfide at Jade area is possibly the undersurface acidic rocks. The mineralizing mechanism can be summarized as follows: Large amount of mineralized material would be leached out and LREEenriched hydrothermal solution would be subsequently produced as a result of thermo-chemical exchange reaction between acidic volcanic rocks and heated seawater that penetrated in advance from upper water mass. The spurting out from the seabed and quickly crystallizing in the seawater of hydrothermal solution are responsible for the formation of Cu-Zn sulfide and barite-amorphous SiO2 minerals that are characterized by enriched LREE and positively strong Eu anomalies.

  17. Monitoring Monitoring Evolving Activity at Popocatepetl Volcano, Mexico, 2000-2001 (United States)

    Martin-DelPozzo, A.; Aceves, F.; Bonifaz, R.; Humberto, S.


    After 6 years of small eruptions, activity at Mexico's 5,452m high Popocatepetl Volcano in central Mexico, peaked in the December 2000-January 2001 eruptions. Precursors included an important increase in seismicity as well as in magmatic components of spring water and small scale deformation which resulted in growth of a new crater dome from January 16 on. Evacuation of the towns nearest the volcano over Christmas was decided because of the possibility of pyroclastic flows. During the previous years, crater dome growth, contraction and explosive clearing has dominated the activity. The January 22 eruption produced an eruption column approximately 17km high with associated pyroclastic flows. Ejecta was composed of both basic and evolved scoria and pumice and dome lithics. A large proportion of the juvenile material was intermediate between these 2 endmenbers (59-63percent SiO2 and 3.5 to 5.5 MgO) consistent with a small basic pulse entering a more evolved larger batch of magma. The January eruption left a large pit which has been partially infilled by another crater dome this August 2001.

  18. Isotopic Constraints (U, Th, Pb, Sr, Ar) on the Timing of Magma Generation, Storage and Eruption of a Late-Pleistocene Subvolcanic Granite, Alid Volcanic Center, Eritrea (United States)

    Lowenstern, J. B.; Charlier, B. L.; Wooden, J. L.; Lanphere, M. A.; Clynne, M. A.; Bullen, T. D.


    Isotopic analyses demonstrate that a shallow granophyric intrusion from the Alid volcanic center (AVC) was generated, intruded and crystallized over a 20,000-year period in the latest Pleistocene. The granophyre is not exposed, but was ejected as unmelted blocks within a ~1 km3 pyroclastic flow deposit around 15 ka and is a subvolcanic equivalent of the erupted rhyolitic pumice (Lowenstern et al., 1997: J Petrol 12, p. 1707-1721). The rock contains 2.59) is 15.2+/- 5.8 ka (all errors are 2 σ ). Two other splits with lower density (thus higher in Na) yielded ages older than 24 ka, and may retain some excess Ar. Thus, the time between intrusion and complete crystallization for the granophyre was Danakil Depression and are found as unmelted lithic xenoliths in lavas and tuffs of the AVC. Pb isotopes also rule out significant assimilation of Precambrian basement during genesis of the young granophyre. Similarly zircon grains, analyzed with the Stanford-USGS SHRIMP-RG, show little evidence for inheritance, with only a single 760 Ma zircon (U-Pb age) that was also petrographically different from the 130 other zircons in the mount. The other zircons yielded SHRIMP 238U230Th disequilibrium ages of Alidpage.html

  19. Latest Pleistocene crustal cannibalization at Baekdusan (Changbaishan) as traced by oxygen isotopes of zircon from the Millennium Eruption (United States)

    Cheong, Albert Chang-sik; Sohn, Young Kwan; Jeong, Youn-Joong; Jo, Hui Je; Park, Kye-Hun; Lee, Youn Soo; Li, Xian-Hua


    The silicic volcanism of Baekdusan (Changbaishan), which is on the border between North Korea and China, was initiated in the Late Pleistocene and culminated in the 10th century with a powerful (volcanic explosivity index = 7) commendite-trachyte eruption commonly referred to as the ;Millennium Eruption.; This study presents oxygen isotope data of zircon in trachydacitic pumices ejected during the Millennium Eruption, together with whole-rock geochemical and Sr-Nd-Pb isotopic data that manifest once again the A-type and EM1 affinities of the Millennium Eruption magma. The zircon crystals, dated by previous studies at ca. 12-9 ka, show a moderate inter-grain variation in δ18O from 3.69‰ to 5.03‰. These values are consistently lower than the normal mantle range, and interpreted to have resulted from the digestion of meteoric-hydrothermally altered intracaldera rocks in the shallow magma chamber beneath Baekdusan just prior to the crystallization of the zircons, rather than from derivation from low-δ18O sources deep in the mantle. The whole-rock geochemical/isotopic considerations suggest that the magma mainly self-cannibalized the earlier erupted volcanic carapace around the magma chamber. This study highlights the usefulness of zircon oxygen isotopes for characterizing past volcanic activity that has now been commonly eroded away and implies that the generation of Yellowstone-type low-δ18O magma is not a rare phenomenon in large-volume silicic eruptions.

  20. Timescales of magmatic processes prior to the ˜4.7 ka Agnano-Monte Spina eruption (Campi Flegrei caldera, Southern Italy) based on diffusion chronometry from sanidine phenocrysts (United States)

    Iovine, Raffaella Silvia; Fedele, Lorenzo; Mazzeo, Fabio Carmine; Arienzo, Ilenia; Cavallo, Andrea; Wörner, Gerhard; Orsi, Giovanni; Civetta, Lucia; D'Antonio, Massimo


    Barium diffusion chronometry applied to sanidine phenocrysts from the trachytic Agnano-Monte Spina eruption (˜4.7 ka) constrains the time between reactivation and eruption of magma batches in the Campi Flegrei caldera. Backscattered electron imaging and quantitative electron microprobe measurements on 50 sanidine phenocrysts from representative pumice samples document core-to-rim compositional zoning. We focus on compositional breaks near the crystal rims that record magma mixing processes just prior to eruption. Diffusion times were modeled at a magmatic temperature of 930 °C using profiles based on quantitative BaO point analyses, X-ray scans, and grayscale swath profiles, yielding times ≤60 years between mixing and eruption. Such short timescales are consistent with volcanological and geochronological data that indicate that at least six eruptions occurred in the Agnano-San Vito area during few centuries before the Agnano-Monte Spina eruption. Thus, the short diffusion timescales are similar to time intervals between eruptions. Therefore, the rejuvenation time of magma residing in a shallow reservoir after influx of a new magma batch that triggered the eruption, and thus pre-eruption warning times, may be as short as years to a few decades at Campi Flegrei caldera.

  1. Volcanological constraints of Archaean tectonics (United States)

    Thurston, P. C.; Ayres, L. D.


    Volcanological and trace element geochemical data can be integrated to place some constraints upon the size, character and evolutionary history of Archean volcanic plumbing, and hence indirectly, Archean tectonics. The earliest volcanism in any greenhouse belt is almost universally tholeitic basalt. Archean mafic magma chambers were usually the site of low pressure fractionation of olivine, plagioclase and later Cpx + or - an oxide phase during evolution of tholeitic liquids. Several models suggest basalt becoming more contaminated by sial with time. Data in the Uchi Subprovince shows early felsic volcanics to have fractionated REE patterns followed by flat REE pattern rhyolites. This is interpreted as initial felsic liquids produced by melting of a garnetiferous mafic source followed by large scale melting of LIL-rich sial. Rare andesites in the Uchi Subprovince are produced by basalt fractionation, direct mantle melts and mixing of basaltic and tonalitic liquids. Composite dikes in the Abitibi Subprovince have a basaltic edge with a chill margin, a rhyolitic interior with no basalt-rhyolite chill margin and partially melted sialic inclusions. Ignimbrites in the Uchi and Abitibi Subprovinces have mafic pumice toward the top. Integration of these data suggest initial mantle-derived basaltic liquids pond in a sialic crust, fractionate and melt sial. The inirial melts low in heavy REE are melts of mafic material, subsequently melting of adjacent sial produces a chamber with a felsic upper part underlain by mafic magma.

  2. Volcanic Processes and Geology of Augustine Volcano, Alaska (United States)

    Waitt, Richard B.; Beget, James E.


    Augustine Island (volcano) in lower Cook Inlet, Alaska, has erupted repeatedly in late-Holocene and historical times. Eruptions typically beget high-energy volcanic processes. Most notable are bouldery debris avalanches containing immense angular clasts shed from summit domes. Coarse deposits of these avalanches form much of Augustine's lower flanks. A new geologic map at 1:25,000 scale depicts these deposits, these processes. We correlate deposits by tephra layers calibrated by many radiocarbon dates. Augustine Volcano began erupting on the flank of a small island of Jurassic clastic-sedimentary rock before the late Wisconsin glaciation (late Pleistocene). The oldest known effusions ranged from olivine basalt explosively propelled by steam, to highly explosive magmatic eruptions of dacite or rhyodacite shed as pumice flows. Late Wisconsin piedmont glaciers issuing from the mountainous western mainland surrounded the island while dacitic eruptive debris swept down the south volcano flank. Evidence is scant for eruptions between the late Wisconsin and about 2,200 yr B.P. On a few south-flank inliers, thick stratigraphically low pumiceous pyroclastic-flow and fall deposits probably represent this period from which we have no radiocarbon dates on Augustine Island. Eruptions between about 5,350 and 2,200 yr B.P. we know with certainty by distal tephras. On Shuyak Island 100 km southeast of Augustine, two distal fall ashes of Augustinian chemical provenance (microprobe analysis of glass) date respectively between about 5,330 and 5,020 yr B.P. and between about 3,620 and 3,360 yr B.P. An Augustine ash along Kamishak Creek 70 km southwest of Augustine dates between about 3,850 and 3,660 yr B.P. A probably Augustinian ash lying within peat near Homer dates to about 2,275 yr B.P. From before 2,200 yr B.P. to the present, Augustine eruptive products abundantly mantle the island. During this period, numerous coarse debris avalanches swept beyond Augustine's coast, most


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    Full Text Available A number of geopolymer cement mixes were designed and produced by alkali-activation of a pumice-type natural pozzolan. Effects of blast-furnace slag on basic engineering properties of the mixes were studied. Different engineering properties of the mixes such as setting times and 28-day compressive strength were studied at different amounts of blast-furnace slag, sodium oxide content, and water-to-cement ratio. The mix comprising of 5 wt.% blast-furnace slag and 8 wt.% Na2O with a water-to-dry binder ratio of 0.30 exhibits the highest 28-day compressive strength, i.e. 36 MPa. Mixes containing 5 wt.% of ground granulated blast furnace slag showed the least efflorescence or best soundness. Laboratory techniques of X-ray diffractometry (XRD, fourier transform infrared spectroscopy (FTIR, and scanning electron microscopy (SEM were utilized for characterizing a number of mixes and studying their molecular and micro-structure. Investigations done by scanning electron microscopy confirm that smaller blast-furnace slag particles react totally while the larger ones react partially with alkaline activators and contribute to the formation of a composite microstructure.

  4. Estimation of AM fungal colonization - Comparability and reliability of classical methods. (United States)

    Füzy, Anna; Biró, Ibolya; Kovács, Ramóna; Takács, Tünde


    The characterization of mycorrhizal status in hosts can be a good indicator of symbiotic associations in inoculation experiments or in ecological research. The most common microscopic-based observation methods, such as (i) the gridline intersect method, (ii) the magnified intersections method and (iii) the five-class system of Trouvelot were tested to find the most simple, easily executable, effective and objective ones and their appropriate parameters for characterization of mycorrhizal status. In a pot experiment, white clover (Trifolium repens L.) host plant was inoculated with 6 (BEG144; syn. Rhizophagus intradices) in pumice substrate to monitor the AMF colonization properties during host growth. Eleven (seven classical and four new) colonization parameters were estimated by three researchers in twelve sampling times during plant growth. Variations among methods, observers, parallels, or individual plants were determined and analysed to select the most appropriate parameters and sampling times for monitoring. The comparability of the parameters of the three methods was also tested. As a result of the experiment classical parameters were selected for hyphal colonization: colonization frequency in the first stage or colonization density in the later period, and arbuscular richness of roots. A new parameter was recommended to determine vesicule and spore content of colonized roots at later stages of symbiosis.


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    Cepeda Héctor


    Full Text Available Paipa volcano products are mainly pyroclastic pumice and ash flow tuffs, lava domes and pyroclastic block and ash flow tuffs. They are classified as alkaline rhyolites and trachytes and high-K calcalkaline rhyolites. Chemical data show SiO2 values between 68 and 72%, and alkalis (Na2O+K2O content of 7%-10%. Essential minerals are phenocrysts and glomerocrysts of anorthoclase, sanidine up to 1,5 cm and anorthoclase-mantled plagioclase; accessory minerals are red biotite, and hastingsite while trace minerals are augite, zircon, sphene and magnetite. Crystals have disequilibrium textures, such as dissolution embayments, corrosion and reabsortion borders, normal, inverse, oscillating and patchy zonation, together with fibrous borders intercalated with euhedral borders. In correlation with published data of Iza volcanic rocks, Paipa rocks chemical composition confirms that acid and alkaline magmas that have erupted in the Eastern Cordillera of Colombia during the Neogene are strongly different from the calc-alkaline magmas that erupt in the westward active arc (Central Cordillera. Detailed structural, geochemical and geophysical research has to be done in future research to establish the geodynamic framework that governs the volcanism of the Eastern Cordillera.

  6. Evaluation of physical properties of enamel after microabrasion, polishing, and storage in artificial saliva

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    Fragoso, L S M; Lima, D A N L; De Alexandre, R S; Bertoldo, C E S; Aguiar, F H B; Lovadino, J R, E-mail: [Department of Restorative Dentistry, Piracicaba Dental School, PO BOX 52 University of Campinas-UNICAMP 13414-903, Piracicaba, Sao Paulo (Brazil)


    This study evaluated the effect of microabrasion and polishing on the microhardness and roughness of bovine enamel, and the effect of artificial saliva on the hardness of enamel. Bovine enamel blocks were used, forming the groups (n = 48): GI-37% phosphoric acid and pumice, GII--Opalustre, and GIII--Whiteness RM. The groups were divided into different subgroups: (a) diamond paste, (b) fluoride prophylactic paste, and (c) without polishing. Hardness tests were carried out at the following set times: (T1) initial, (T2) after microabrasion and polishing, (T3) after immersion in artificial saliva for 24 h; and (T4) after seven days of immersion. Surface roughness tests were performed. The obtained data were analyzed by two-factor ANOVA and Tukey's test with significance of 5%. Microhardness increased in T2; without polishing, only groups GII and GIII showed an increased microhardness. T3 did not differ from T4; GI, GII and GIII did not provide surface roughness that differed from each other; and all microabrasive systems followed by polishing showed a higher surface smoothness compared with the control groups. It is concluded that microabrasion followed by polishing provided higher hardness and better surface smoothness of the enamel. However, immersion in artificial saliva was not able to increase the enamel hardness.

  7. The Characteristics of Lahar in Merapi Volcano, Central Java as the Indicator of the Explosivity during Holocene

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    Adjat Sudradjat


    Full Text Available DOI: 10.17014/ijog.v6i2.116Merapi Volcano in Central Java has been the most active volcano during Holocene time. As a strato volcano, Merapi exhibits alternating volcanic activities of effusive and explosive characters and self destruction. The explosivity index has evolved during the last ten thousand years. The effusive activities were characterized by the occurrence of lava flows, the development of lava dome, and the production of the “nuee ardente d’avalanche” called Merapi type. The explosive stage is frequently accompanied by the occurence of pyroclastic flows. The present investigation is attempted to reveal the relationship between the characteristics of lahar and the evolution of the activity of Merapi Volcano. The quantitative analysis was focused on the size and shape of the lahar components particularly that of pumice as the main indicators in 73 measured stratigraphic columns of lahar deposits. In addition, the main chemical element rim structures of hornblende identified in lahar components indicate the different lahar units. There are five lahar units and five groups of Merapi activities which can be distinguished. It can be concluded that the characteristics of lahar reflect the evolution of the activities in the past. The risk analyses of Merapi Volcano therefore can be enlarged to cover the possible hazard based on the lahar characteristics.

  8. Fluvial and glacial implications of tephra localities in the western Wind River basin, Wyoming, U. S. A

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    Jaworowski, C. (Univ. of Wyoming, Laramie, WY (United States). Dept. of Geology)


    Examination of Quaternary fluvial and glacial deposits in the western Wind River Basin allows a new understanding of the Quaternary Wind River fluvial system. Interbedded fluvial sediments and volcanic ashes provide important temporal information for correlation of Quaternary deposits. In the western Wind River Basin, six mid-Pleistocene localities of tephra, the Muddy Creek, Red Creek, Lander, Kinnear, Morton and Yellow Calf ashes are known. Geochronologic studies confirm the Muddy Creek, Red Creek, Kinnear and Lander ashes as the 620--650ka Lava Creek tephra from the Yellowstone region in northwestern Wyoming. The stratigraphic position and index of refraction of volcanic glass from the Morton and Yellow Calf ashes are consistent with identification as Lava Creek tephra. Approximately 350 feet (106 meters) above the Wind River and 13 miles downstream from Bull Lake, interbedded Wind River fluvial gravels, volcanic glass and pumice at the Morton locality correlate to late (upper) Sacajawea Ridge gravels mapped by Richmond and Murphy. Associated with the oxygen isotope 16--15 boundary, the ash-bearing terrace deposits reveal the nature of the Wind River fluvial system during late glacial-early interglacial times. The Lander and Yellow Calf ashes, are found in terrace deposits along tributaries of the Wind River. Differences in timing and rates of incision between the Wind River and its tributary, the Little Wind River, results in complex terrace development near their junction.

  9. Effects of sucrose amendment on ammonia assimilation during sewage sludge composting. (United States)

    Meng, Liqiang; Li, Weiguang; Zhang, Shumei; Wu, Chuandong; Wang, Ke


    The aim of this study was to evaluate the laboratory-scale composting of sewage sludge and pumice mixtures that were amended with sucrose. The variation in temperature, pH, NH4(+)-N, ammonia emission, bacterial community, ammonia assimilating bacteria (AAB) populations and enzymatic activity related to ammonia assimilation were detected. The addition of sucrose increased the AAB population by 2.5-3.5 times, reduced ammonia emission by 24.7-31.1% compared with the control treatment, and promoted the growth of Bacillus and Wautersiella. The activities of glutamate dehydrogenase (GDH), glutamate synthase (GS) and glutamine synthetase (GOGAT), were enhanced by the addition of sucrose. GDH made a substantial contribution to ammonia assimilation when the ammonia concentration was high (⩾1.5g/kg) in the thermophilic phase. The GS/GOGAT cycle played an important role at low ammonia concentrations (⩽1.1g/kg) in the cooling phase. These results suggested that adding sucrose to sludge compost could promote ammonia assimilation and reduce ammonia emission.

  10. Evaluation of surface physical properties of acrylic resins for provisional prosthesis

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    Sérgio Paulo Hilgenberg


    Full Text Available Acrylic resins used for provisional prostheses should have satisfactory superficial characteristics in order to ensure gingival health and low bacterial attachment. The purpose of the present study was to evaluate the superficial roughness and contact angle after two types of polishing and the Vickers hardness of three acrylic resins (Duralay - G1, Dencrilay - G2, and Dencor - G3, all shade 66, indicated for provisional fixed prostheses. Five 20 x 3 ± 1 mm diameter discoid specimens were obtained for each group. One side of the specimens was subjected to standard polishing (pumice and whiting slurry, and the opposite side was polished with special tips. The mean roughness and contact angles of the materials were measured. The specimens were subjected to the Vickers microhardness test, which indicated that standard polishing produced a surface roughness equivalent to that of the special tips. The contact angles obtained with the standard polishing were equivalent to those observed in the special tips group. The microhardness of G1 and G3 resins showed statistical differences.

  11. Petro-chemical features and source areas of volcanic aggregates used in ancient Roman maritime concretes (United States)

    Marra, F.; Anzidei, M.; Benini, A.; D'Ambrosio, E.; Gaeta, M.; Ventura, G.; Cavallo, A.


    We present and discuss data from petrographic observation at the optical microscope, electron microprobe analyses on selected glass shards, and trace-element analyses on 14 mortar aggregates collected at the ancient harbors and other maritime structures of Latium and Campania, spanning the third century BCE through the second CE, aimed at identify the volcanic products employed in the concretes and their area of exploitation. According to Latin author Vitruvius assertion about the ubiquitous use of Campanian pozzolan in the ancient Roman sea-water concretes, results of this study show a very selective and homogeneous choice in the material employed to produce the concretes for the different investigated maritime structures, evidencing three main pumice compositions, all corresponding to those of the products of the post-Neapolitan Yellow Tuff activity of the Phlegraean Fields, and a systematic use of the local Neapolitan Yellow Tuff to produce the coarse aggregate of these concretes. However, mixing with local products of the Colli Albani volcanic district, located 20 km east of Rome, has been evidenced at two fishponds of Latium, in Punta della Vipera and Torre Astura. Based on these petrographic and geochemical data, we conclude that the selective use of pozzolan from Campania, rather than of unproved different chemical properties, was the consequence of a series of logistic, economic, industrial and historical reasons.

  12. Geologic factors contributing to landslide generation in a pyroclastic area: August 1998 Nishigo Village, Japan (United States)

    Chigira, Masahiro


    Vertical contrasts in permeability, particularly where permeable surface materials overlie impermeable materials that prohibit the downward infiltration of groundwater, concentrate the groundwater and become an important focus of landslides that are triggered by intense rainfall. Just such a hydrogeological structure is present within the pyroclastics in Nishigo Village in Fukushima Prefecture, Japan, where intense rainfall of 1200 mm in 6 days generated more than 1000 landslides in August 1998. Three types of landslides occurred. The first type occurred along the edges of small plateaus, where horizontal beds of permeable ash, scoria, and pumice overlie impermeable mudflow deposits consisting of tuffaceous fines and andesite blocks, and massive, weakly consolidated ignimbrites. The rainfall on the plateaus infiltrated downward first, then laterally within the permeable beds, finally gushing out at the plateau edges and triggering landslides. The second type of landslide occurred where weathered tuff of the same ignimbrite was present with a slip surface at the base of the heavily weathered zone. Within this heavily weathered zone, the tuff exfoliated into thin weak plates running parallel to the slope surface. The third type of landslide involved failure of colluvium or ash that filled hollows. This type occurred as a result of subsurface erosion caused by the groundwater infiltrating the superficial beds above the impermeable tuff.

  13. The Avellino 3780-yr-B.P. catastrophe as a worst-case scenario for a future eruption at Vesuvius. (United States)

    Mastrolorenzo, Giuseppe; Petrone, Pierpaolo; Pappalardo, Lucia; Sheridan, Michael F


    A volcanic catastrophe even more devastating than the famous anno Domini 79 Pompeii eruption occurred during the Old Bronze Age at Vesuvius. The 3780-yr-B.P. Avellino plinian eruption produced an early violent pumice fallout and a late pyroclastic surge sequence that covered the volcano surroundings as far as 25 km away, burying land and villages. Here we present the reconstruction of this prehistoric catastrophe and its impact on the Bronze Age culture in Campania, drawn from an interdisciplinary volcanological and archaeoanthropological study. Evidence shows that a sudden, en masse evacuation of thousands of people occurred at the beginning of the eruption, before the last destructive plinian column collapse. Most of the fugitives likely survived, but the desertification of the total habitat due to the huge eruption size caused a social-demographic collapse and the abandonment of the entire area for centuries. Because an event of this scale is capable of devastating a broad territory that includes the present metropolitan district of Naples, it should be considered as a reference for the worst eruptive scenario at Vesuvius.

  14. Evidence for water influx from a caldera lake during the explosive hydromagmatic eruption of 1790, Kilauea volcano, Hawaii (United States)

    Mastin, L.G.


    In 1790 a major hydromagmatic eruption at the summit of Kilauea volcano, Hawaii, deposited up to 10 m of pyroclastic fall and surge deposits and killed several dozen Hawaiian natives who were crossing the island. Previous studies have hypothesized that the explosivity of this eruption was due to the influx of groundwater into the conduit and mixing of the groundwater with ascending magma. This study proposes that surface water, not groundwater, was the agent responsible for the explosiveness of the eruption. That is, a lake or pond may have existed in the caldera in 1790 and explosions may have taken place when magma ascended into the lake from below. That assertion is based on two lines of evidence: (1) high vesicularity (averaging 73% of more than 3000 lapilli) and high vesicle number density (105-107 cm-3 melt) of pumice clasts suggest that some phases of the eruption involved vigorous, sustained magma ascent; and (2) numerical calculations suggest that under most circumstances, hydrostatic pressure would not be sufficient to drive water into the eruptive conduit during vigorous magma ascent unless the water table were above the ground surface. These results are supported by historical data on the rate of infilling of the caldera floor during the early 1800s. When extrapolated back to 1790, they suggest that the caldera floor was below the water table.

  15. August 2008 eruption of Kasatochi volcano, Aleutian Islands, Alaska-resetting an Island Landscape (United States)

    Scott, W.E.; Nye, C.J.; Waythomas, C.F.; Neal, C.A.


    Kasatochi Island, the subaerial portion of a small volcano in the western Aleutian volcanic arc, erupted on 7-8 August 2008. Pyroclastic flows and surges swept the island repeatedly and buried most of it and the near-shore zone in decimeters to tens of meters of deposits. Several key seabird rookeries in taluses were rendered useless. The eruption lasted for about 24 hours and included two initial explosive pulses and pauses over a 6-hr period that produced ash-poor eruption clouds, a 10-hr period of continuous ash-rich emissions initiated by an explosive pulse and punctuated by two others, and a final 8-hr period of waning ash emissions. The deposits of the eruption include a basal muddy tephra that probably reflects initial eruptions through the shallow crater lake, a sequence of pumiceous and lithic-rich pyroclastic deposits produced by flow, surge, and fall processes during a period of energetic explosive eruption, and a fine-grained upper mantle of pyroclastic-fall and -surge deposits that probably reflects the waning eruptive stage as lake and ground water again gained access to the erupting magma. An eruption with similar impact on the island's environment had not occurred for at least several centuries. Since the 2008 eruption, the volcano has remained quiet other than emission of volcanic gases. Erosion and deposition are rapidly altering slopes and beaches. ?? 2010 Regents of the University of Colorado.

  16. Paleomagnetically Determined Emplacement temperatures of the Explosive cycles of Santorini (United States)

    Mac Niocaill, C.; Dodd, S. C.; McClelland, E.; Muxworthy, A. R.; Paterson, G. A.


    Santorini volcano preserves two major eruptive cycles in the past 300ka. These span 12 pyroclastic eruptions, which are visible as layers in the caldera walls, with the first cycle spanning from 300-180ka and the second spanning from 180-3.6ka. These cycles begin with mafic to intermediate magmas but the terminating pair of eruptions of each cycle involve silicic magmas and major caldera forming events. We present new palaeomagnetic determinations of emplacement temperatures for the Minoan, Upper Scoria, Lower Pumice and Cape Therma deposits, which, in conjunction with published work, means that we now have constraints on the emplacement temperatures of all major pyroclastic deposits within the two grand cycles. Our work establishes that the final two eruptions of each cycle show predominantly lower temperatures than those of intermediate eruptions although there is no 'perfect' cyclic temperature variation seen which would clearly define the cycles. The lower temperatures seen within the intermediate eruptions suggest that composition, and slight differences in the initial magmatic temperature, play very little role in controlling the emplacement temperature. The dominant control on the pyroclastic emplacement temperatures of Santorini appears to be the degree of water interaction into the vent and the percentage of lithics, both of which, when increasing, lower the unit temperature. It may be that the more viscous form of silicic magmas, which causes them to be inherently more explosive, results in the increased likelihood of these eruptions causing higher degrees of water interaction and caldera collapse, and therefore lowering emplacement temperatures.

  17. Ranking welding intensity in pyroclastic deposits (United States)

    Quane, Steven L.; Russell, James K.


    Welding of pyroclastic deposits involves flattening of glassy pyroclasts under a compactional load at temperatures above the glass transition temperature. Progressive welding is recorded by changes in the petrographic (e.g., fabric) and physical (e.g., density) properties of the deposits. Mapping the intensity of welding can be integral to studies of pyroclastic deposits, but making systematic comparisons between deposits can be problematical. Here we develop a scheme for ranking welding intensity in pyroclastic deposits on the basis of petrographic textural observations (e.g., oblateness of pumice lapilli and micro-fabric orientation) and measurements of physical properties, including density, porosity, point load strength and uniaxial compressive strength. Our dataset comprises measurements on 100 samples collected from a single cooling unit of the Bandelier Tuff and parallel measurements on 8 samples of more densely welded deposits. The proposed classification comprises six ranks of welding intensity ranging from unconsolidated (Rank I) to obsidian-like vitrophyre (Rank VI) and should allow for reproducible mapping of subtle variations in welding intensity between different deposits. The application of the ranking scheme is demonstrated by using published physical property data on welded pyroclastic deposits to map the total accumulated strain and to reconstruct their pre-welding thicknesses.

  18. Anisotropy of magnetic susceptibility in welded tuffs: application to a welded-tuff dyke in the tertiary Trans-Pecos Texas volcanic province, USA (United States)

    Wolff, John A.; Ellwood, Brooks B.; Sachs, Scott D.


    Consideration of published anisotropy of magnetic susceptibility (AMS) studies on welded ignimbrites suggests that AMS fabrics are controlled by groundmass microlites distributed within the existing tuff fabric, the sum result of directional fabrics imposed by primary flow lineation, welding, and (if relevant) rheomorphism. AMS is a more sensitive indicator of fabric elements within welded tuffs than conventional methods, and usually yields primary flow azimuth estimates. Detailed study of a single densely welded tuff sample demonstrates that the overall AMS fabric is insensitive to the relative abundances of fiamme, matrix and lithics within individual drilled cores. AMS determinations on a welded-tuff dyke occurring in a choked vent in the Trans-Pecos Texas volcanic field reveals a consistent fabric with a prolate element imbricated with respect to one wall of the dyke, while total magnetic susceptibility and density exhibit axially symmetric variations across the dyke width. The dyke is interpreted to have formed as a result of agglutination of the erupting mixture on a portion of the conduit wall as it failed and slid into the conduit, followed by residual squeezing between the failed block and in situ wallrock. Irrespective of the precise mechanism, widespread occurrence of both welded-tuff dykes and point-welded, aggregate pumices in pyroclastic deposits may imply that lining of conduit walls by agglutionation during explosive volcanic eruptions is a common process.

  19. Radiogenic Heat Production in the Gölcük Caldera and Direkli, Isparta Angle (Southwest Anatolia) (United States)

    Ayten Uyanık, Nurten; Öncü, Ziya; Akkurt, İskender


    The radiogenic heat is one of the important parameter due to the radioactivity has existed since beginning of universe as prediction of Big-Bang theory. In this study the radiogenic heat production of the Gölcük caldera and Direkli fields of the Isparta-Turkey, has been investigated. Total of 1390 data were obtained in the study area. The study area is included of the Gölcük volcanism and its around that is located in Isparta province of Turkey's Mediterranean region. The Gölcük volcanism is a young volcanism. Around this volcanism the andesite, trachy andesite, tuff, pumice and such a geological units is available. The data were collected using in-situ measurements with gamm-ray spectrometer. These measurements were covered natural radioactive elements (Uranium U, Thorium Th and Potassium K). Radiogenic heat production values were calculated using the literature relationships and in-situ measurement values of these radioactive elements. Radiogenic heat map of study area were obtained using radiogenic heat production values. In the map the red zone areas shows highest heat values while green zones areas of the map presents lowest heat values. Key words: Radioactive elements, radiogenic heat, map, Gölcük-Direkli(Isparta), Turkey

  20. Volcanic hazard zonation of the Nevado de Toluca volcano, México (United States)

    Capra, L.; Norini, G.; Groppelli, G.; Macías, J. L.; Arce, J. L.


    The Nevado de Toluca is a quiescent volcano located 20 km southwest of the City of Toluca and 70 km west of Mexico City. It has been quiescent since its last eruptive activity, dated at ˜ 3.3 ka BP. During the Pleistocene and Holocene, it experienced several eruptive phases, including five dome collapses with the emplacement of block-and-ash flows and four Plinian eruptions, including the 10.5 ka BP Plinian eruption that deposited more than 10 cm of sand-sized pumice in the area occupied today by Mexico City. A detailed geological map coupled with computer simulations (FLOW3D, TITAN2D, LAHARZ and HAZMAP softwares) were used to produce the volcanic hazard assessment. Based on the final hazard zonation the northern and eastern sectors of Nevado de Toluca would be affected by a greater number of phenomena in case of reappraisal activity. Block-and-ash flows will affect deep ravines up to a distance of 15 km and associated ash clouds could blanket the Toluca basin, whereas ash falls from Plinian events will have catastrophic effects for populated areas within a radius of 70 km, including the Mexico City Metropolitan area, inhabited by more than 20 million people. Independently of the activity of the volcano, lahars occur every year, affecting small villages settled down flow from main ravines.

  1. Paleoclimate change in the Nakuru basin, Kenya, at 119 - 109 ka derived from δ18Odiatom and diatom assemblages and 40Ar/39Ar geochronology (United States)

    Bergner, Andreas; Deino, Alan; Leng, Melanie; Gasse, Francoise


    A 4.5m-thick diatomite bed deposited during the cold interval of the penultimate interglacial at ~119 - 109 ka documents a period in which a deep freshwater lake filled the Nakuru basin in the Central Kenya Rift (CKR), East Africa. Palaeohydrological conditions of the basin are reconstructed for the paleolake highstand using δ18Odiatom and characterization of diatom assemblages. The age of the diatomite deposit is established by precise 40Ar/39Ar-dating of intercalated pumice tuffs. The paleolake experienced multiple hydrological fluctuations on sub-orbital (~1,500 to 2,000 years) time scales. The magnitude of the δ18Odiatom change (+/- 3‰) and significant changes in the plankton-littoral ratio of the diatom assemblage (+/- 25%) suggest that the paleolake record can be interpreted in the context of long-term climatic change in East Africa. Using 40Ar/39Ar age control and nominal diatomite-sedimentation rates we establish a simplified age model of paleohydrological vs. climatic change, from which we conclude that more humid conditions prevailed in equatorial East Africa during the late Pleistocene over a relatively long time interval of several thousands years. Then, extreme insolation at eccentricity maximum and weakened zonal air-pressure gradients in the tropics favored intensified ITCZ-like convection over East Africa and deep-freshwater lake conditions.

  2. Mineralization of reactive azo dyes present in simulated textile waste water using down flow microaerophilic fixed film bioreactor. (United States)

    Balapure, Kshama; Bhatt, Nikhil; Madamwar, Datta


    The present research emphasizes on degradation of azo dyes from simulated textile wastewater using down flow microaerophilic fixed film reactor. Degradation of simulated textile wastewater (COD 7200mg/L and dye concentration 300mg/L) was studied in a microaerophilic fixed film reactor using pumice stone as a support material under varying hydraulic retention time (HRT) and organic loading rate (OLR). The intense metabolic activity of the inoculated bacterial consortium in the reactor led to 97.5% COD reduction and 99.5% decolorization of simulated wastewater operated under OLR of 7.2kgCODm(3)/d and 24h of HRT. FTIR, (1)H NMR and GC-MS studies revealed the formation of lower molecular weight aliphatic compounds under 24h of HRT, leading to complete mineralization of simulated wastewater. The detection of oxido-reductive enzyme activities suggested the enzymatic reduction of azo bonds prior to mineralization. Toxicity studies indicated that microbial treatment favors detoxification of simulated wastewater.

  3. Analysis of Regolith Simulant Ejecta Distributions from Normal Incident Hypervelocity Impact (United States)

    Edwards, David L.; Cooke, William; Suggs, Rob; Moser, Danielle E.


    The National Aeronautics and Space Administration (NASA) has established the Constellation Program. The Constellation Program has defined one of its many goals as long-term lunar habitation. Critical to the design of a lunar habitat is an understanding of the lunar surface environment; of specific importance is the primary meteoroid and subsequent ejecta environment. The document, NASA SP-8013 'Meteoroid Environment Model Near Earth to Lunar Surface', was developed for the Apollo program in 1969 and contains the latest definition of the lunar ejecta environment. There is concern that NASA SP-8013 may over-estimate the lunar ejecta environment. NASA's Meteoroid Environment Office (MEO) has initiated several tasks to improve the accuracy of our understanding of the lunar surface ejecta environment. This paper reports the results of experiments on projectile impact into powdered pumice and unconsolidated JSC-1A Lunar Mare Regolith simulant targets. Projectiles were accelerated to velocities between 2.45 and 5.18 km/s at normal incidence using the Ames Vertical Gun Range (AVGR). The ejected particles were detected by thin aluminum foil targets strategically placed around the impact site and angular ejecta distributions were determined. Assumptions were made to support the analysis which include; assuming ejecta spherical symmetry resulting from normal impact and all ejecta particles were of mean target particle size. This analysis produces a hemispherical flux density distribution of ejecta with sufficient velocity to penetrate the aluminum foil detectors.

  4. Comparison of Ejecta Distributions from Normal Incident Hypervelocity Impact on Lunar Regolith Simulant (United States)

    Edwards, David L.; Cooke, William; Scruggs, Rob; Moser, Danielle E.


    The National Aeronautics and Space Administration (NASA) is progressing toward long-term lunar habitation. Critical to the design of a lunar habitat is an understanding of the lunar surface environment; of specific importance is the primary meteoroid and subsequent ejecta environment. The document, NASA SP-8013, was developed for the Apollo program and is the latest definition of the ejecta environment. There is concern that NASA SP-8013 may over-estimate the lunar ejecta environment. NASA's Meteoroid Environment Office (MEO) has initiated several tasks to improve the accuracy of our understanding of the lunar surface ejecta environment. This paper reports the results of experiments on projectile impact into powered pumice and unconsolidated JSC-1A Lunar Mare Regolith stimulant (JSC-1A) targets. The Ames Vertical Gun Range (AVGR) was used to accelerate projectiles to velocities in excess of 5 km/s and impact the targets at normal incidence. The ejected particles were detected by thin aluminum foil targets placed around the impact site and angular distributions were determined for ejecta. Comparison of ejecta angular distribution with previous works will be presented. A simplistic technique to characterize the ejected particles was formulated and improvements to this technique will be discussed for implementation in future tests.

  5. Transport and Emplacement of the 15.4 Ma Rhyolitic Ignimbrites from Gutai Mts., Eastern Carpathians

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    Alexandrina Fulop


    Full Text Available The 15.4 Ma rhyolitic ignimbrites are the first volcanic products from Gutâi Mts. The study of their sedimentary structures reflects the mechanisms involved in the transport and emplacement of the parental flows, essential to inffering the style of eruption and the source evolution and location. Primary sedimentary structures show massive deposits emplaced from mass flows, sequence of units showing the normal coarse-tail grading of the dense clasts and the reverse coarse-tail grading of the pumice clasts. They reflect concentrated laminar flows or dilute, subcritical flows emplaced by progressive aggradation. Secondary sedimentary structures are represented by the eutaxitic texture or welding, cooling textures (columnar jointings, spherulitic textures and gas-escape pipes. They assess the hot state deposition with low degree of fluidization, low cooling rates and gas-retention regime. Secondary sedimentary structures are represented by the eutaxitic texture or welding, cooling textures (columnar jointings, spherulitic textures and gas-escape pipes. They assess the hot state deposition with low degree of fluidization, low cooling rates and gas-retention regime.

  6. Effect of different surface treatments on microtensile bond strength of two resin cements to aged simulated composite core materials. (United States)

    Esmaeili, Behnaz; Alaghehmand, Homayoon; Shakerian, Mohadese


    Roughening of the aged composite resin core (CRC) surface seems essential for durable adhesion. The aim of this study was to investigate the influence of various surface treatments and different resin cements on microtensile bond strength (µ TBS) between two aged core build-up composites (CBCs) and feldspathic ceramic. A total of 16 composite blocks made of two CBCs, and Build-it were randomly assigned to four surface treatment groups after water storage and thermocycling (2 weeks and 500 cycles). Experimental groups included surface roughening with air abrasion (AA), hydrofluoric acid, pumice, and laser and then were bonded to computer-aided design/computer-aided manufacturing feldspathic ceramic blocks using two resin cements, Panavia F2 (PF), and Duo-link (DL). The µ TBS was tested, and the fracture mode was assessed. The data were analyzed with multiple analysis of variance to estimate the contribution of different surface treatments, resin cements, and two aged CRCs on µ TBS. Statistical significance level was set at α strength (P strength was in AA group cemented with PF (31.83 MPa). The most common failure mode was cohesive fracture in the cement. Different surface treatments had different effects on µ TBS of aged CRCs to feldspathic ceramics. PF was significantly better than DL.

  7. Flow characteristics and sealing ability of fissure sealants. (United States)

    Barnes, D M; Kihn, P; von Fraunhofer, J A; Elsabach, A


    This study evaluated the relationship between fissure sealant viscosity, leakage prevention and the incidence of void formation of five commercially available pit-and-fissure sealants. Seventy-two intact, caries free human pre-molars and molars were divided into six test groups of 12 teeth each. All teeth were cleaned with a flour of pumice prophylaxis followed by etching for 60 seconds with 37% H3PO4, rinsing for 30 seconds and drying with oil-free air. Five commercial, light-cured fissure sealants and an unfilled version of one sealant were applied following manufacturers' instructions. Teeth were thermal cycled for 5000 cycles from 5-50 degrees C with a one-minute dwell time at each temperature. Silver nitrate staining followed by mesiodistal sectioning was performed. Leakage and void formation were evaluated at X50 optical magnification. Viscosity was assessed by syringing the fissure sealants into short pipettes, allowing free flow for 30 seconds and then light curing for one minute. The length of unfilled capillary was measured with a Vernier gauge. All experimental data was subjected to a one-way ANOVA, and where differences were detected, they were identified by a post hoc Tukey hsd test at a priori alpha = 0.05. Based on the conditions of the study, viscosity and flow characteristics had no effect on sealing ability or void formation.

  8. IODP Expedition 331: Strong and Expansive Subseafloor Hydrothermal Activities in the Okinawa Trough

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    the IODP Expedition 331 Scientists


    Full Text Available Integrated Ocean Drilling Program (IODP Expedition 331 drilled into the Iheya North hydrothermal system in the middle Okinawa Trough in order to investigate active subseafloor microbial ecosystems and their physical and chemical settings. We drilled five sites during Expedition 331 using special guide bases at three holes for reentry, casing, and capping, including installation of a steel mesh platformwith valve controls for postcruise sampling of fluids. At Site C0016, drilling at the base of the North Big Chimney (NBCmound yielded low recovery, but core included the first Kuroko-type black ore ever recovered from the modern subseafloor. The other four sites yielded interbedded hemipelagic and strongly pumiceous volcaniclastic sediment, along with volcanogenic breccias that are variably hydrothermally altered and mineralized. At most sites, analyses of interstitial water and headspace gas yielded complex patterns withdepth and lateral distance of only a few meters. Documented processes included formation of brines and vapor-rich fluids by phase separation and segregation, uptake of Mg and Na by alteration minerals in exchange for Ca, leaching of K at high temperature and uptake at low temperature, anhydrite precipitation, potential microbial oxidation of organic matter and anaerobic oxidation of methane utilizing sulfate, and methanogenesis. Shipboard analyses have found evidence for microbial activity in sediments within the upper 10–30 m below seafloor (mbsf where temperatures were relativelylow, but little evidence in the deeper hydrothermally altered zones and hydrothermal fluid regime.

  9. Tsunamis Observed on the Coasts of Greece from Antiquity to Present Time

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    Full Text Available In comparison with the great number of disastrous earthquakes
    which have occurred from antiquity to the present time in Greece, large
    tsunamis are very rare on the coasts of Greece. A really great tsunami
    may have started in the Aegean Sea after the tremendous explosion of
    Santorin volcano, which occurred 3370 ± 100 years ago (13. After the
    deposit of a layer of pumice 20-30 m thick and the emptying of the
    volcanic focus, the roof of the cavern thus formed collapsed. The
    centrai part, consisting of an area of 83 sq km, of the former island
    Stronghyb tlius became a gigantic caldera 300-400 m deep.
    Tliere is no evidence indicating whether the cobapse took place
    graduaby or ab at once. In the second case a huge tsunami should have
    started greater by far than that generated by the explosion of Krakatoa,
    on August 27, 1883. At that time depths of 200-300 m were formed by
    the sinking (24 of 2/3 of the former island of an area of 33 1/2 sq km.
    Thus the cavity formed by the explosion of Santorin is about 4 times
    greater than that of the Krakatoa.

  10. Dental enamel roughness with different acid etching times: Atomic force microscopy study

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    Bruno Bochnia Cerci


    Full Text Available Objective: An important characteristic of human dental enamel not yet studied in detail is its surface roughness in mesoscopic scale. This study evaluated quantitatively and qualitatively the surface topography of acid etched enamel with different etching times. Materials and Methods: Ninety-six human maxillary bicuspids were randomly distributed into three groups (n=32: T0 (control, pumiced; T15, 35% phosphoric acid etched enamel for 15 s; T30, 35% phosphoric acid etched enamel for 30 s. Roughness measurements Ra, Rz and root mean square (RMS and 3D images of enamel′s topography were obtained with atomic force microscopy (AFM, which is a powerful technique to obtain direct measurements on microscale features. Results and Conclusions: Roughness variables Ra, Rz and RMS presented statistically significant differences to all groups (P<0.000, with values increasing with etching time. This increase was greater from T0 to T15 than from T15 to T30. Enamel surface alterations T15 to T30 occur mainly due to increase in height and deepening of prisms central region.

  11. Volcano-related materials in concretes: a comprehensive review. (United States)

    Cai, Gaochuang; Noguchi, Takafumi; Degée, Hervé; Zhao, Jun; Kitagaki, Ryoma


    Massive volcano-related materials (VRMs) erupted from volcanoes bring the impacts to natural environment and humanity health worldwide, which include generally volcanic ash (VA), volcanic pumice (VP), volcanic tuff (VT), etc. Considering the pozzolanic activities and mechanical characters of these materials, civil engineers propose to use them in low carbon/cement and environment-friendly concrete industries as supplementary cementitious materials (SCMs) or artificial/natural aggregates. The utilization of VRMs in concretes has attracted increasing and pressing attentions from research community. Through a literature review, this paper presents comprehensively the properties of VRMs and VRM concretes (VRMCs), including the physical and chemical properties of raw VRMs and VRMCs, and the fresh, microstructural and mechanical properties of VRMCs. Besides, considering environmental impacts and the development of long-term properties, the durability and stability properties of VRMCs also are summarized in this paper. The former focuses on the resistance properties of VRMCs when subjected to aggressive environmental impacts such as chloride, sulfate, seawater, and freezing-thawing. The latter mainly includes the fatigue, creep, heat-insulating, and expansion properties of VRMCs. This study will be helpful to promote the sustainability in concrete industries, protect natural environment, and reduce the impacts of volcano disaster. Based on this review, some main conclusions are discussed and important recommendations regarding future research on the application of VRMs in concrete industries are provided.

  12. Largest explosive eruption in historical times in the Andes at Huaynaputina volcano, a.d. 1600, southern Peru (United States)

    Thouret, Jean-Claude; Davila, Jasmine; Eissen, Jean-Philippe


    The largest explosive eruption (volcanic explosivity index of 6) in historical times in the Andes took place in a.d. 1600 at Huaynaputina volcano in southern Peru. According to chronicles, the eruption began on February 19 with a Plinian phase and lasted until March 6. Repeated tephra falls, pyroclastic flows, and surges devastated an area 70 × 40 km2 west of the vent and affected all of southern Peru, and earthquakes shook the city of Arequipa 75 km away. Eight deposits, totaling 10.2 13.1 km3 in bulk volume, are attributed to this eruption: (1) a widespread, ˜8.1 km3 pumice-fall deposit; (2) channeled ignimbrites (1.6 2 km3) with (3) ground-surge and ash-cloud-surge deposits; (4) widespread co-ignimbrite ash layers; (5) base-surge deposits; (6) unconfined ash-flow deposits; (7) crystal-rich deposits; and (8) late ash-fall and surge deposits. Disruption of a hydrothermal system and hydromagmatic interactions are thought to have fueled the large-volume explosive eruption. Although the event triggered no caldera collapse, ring fractures that cut the vent area point to the onset of a funnel-type caldera collapse.

  13. Effects of Chairside Polishing and Brushing on Surface Roughness of Acrylic Denture Base Resins

    Institute of Scientific and Technical Information of China (English)

    Seung-Kyun Kim; Ju-Mi Park; Min-Ho Lee; Jae-Youn Jung; Shipu Li; Xinyu Wang


    The effects of 3 chairside polishing kits and mechanical brushing on the surface roughness of 3 different acrylic denture base resins were compared. Acrylic denture base resins (auto-polymerizing, heat-polymerizing, injected heat-polymerizing resins) were examined after a tungsten carbide bur, and after chairside polishing using 3 polishing kits and pumice. The specimens were subjected to mechanical brushing using a wear tester to simulate 30 000 strokes of brushing. The surface roughness of the acrylic denture base resin specimens was measured using a contact pro-filometer. After the test, the random polished acrylic resins were evaluated by scanning electron mi-croscopy (SEM) and atomic force microscopy (AFM). Acrylic denture base resins polished using the 3 types of polishing kits had a smoother surface than those finished with the tungsten carbide bur (p <0.05). The surface of the resin polished by a TC cutter exceeded the Ra of 0.2 μm (p<0.05). The auto-polymerizing resin showed a significantly higher surface roughness than the heat-polymerizing resin and injected heat-polymerizing resin (p>0.05). In the case of polishing step wise, there was almost no change in surface roughness after brushing (p>0.05).

  14. Evaluating Complex Magma Mixing via Polytopic Vector Analysis (PVA in the Papagayo Tuff, Northern Costa Rica: Processes that Form Continental Crust

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    Guillermo E. Alvarado


    Full Text Available Over the last forty years, research has revealed the importance of magma mixing as a trigger for volcanic eruptions, as well as its role in creating the diversity of magma compositions in arcs. Sensitive isotopic and microchemical techniques can reveal subtle evidence of magma mixing in igneous rocks, but more robust statistical techniques for bulk chemical data can help evaluate complex mixing relationships. Polytopic vector analysis (PVA is a multivariate technique that can be used to evaluate suites of samples that are produced by mixing of two or more magma batches. The Papagayo Tuff of the Miocene-Pleistocene Bagaces Formation in northern Costa Rica is associated with a segment of the Central American Volcanic Arc. While this segment of the arc is located on oceanic plateau, recent (<8 Ma ignimbrites bear the chemical signatures of upper continental crust, marking the transition from oceanic to continental crust. The Papagayo Tuff contains banded pumice fragments consistent with one or more episodes of mixing/mingling to produce a single volcanic deposit. The PVA solution for the sample set is consistent with observations from bulk chemistry, microchemistry and petrographic data from the rocks. However, without PVA, the unequivocal identification of the three end-member solution would not have been possible.

  15. Source identification of volcanic ashes by geochemical analysis of well preserved lacustrine tephras in Nahuel Huapi National Park

    Energy Technology Data Exchange (ETDEWEB)

    Daga, Romina [Laboratorio de Analisis por Activacion Neutronica, Centro Atomico Bariloche, 8400 Bariloche (Argentina)], E-mail:; Ribeiro Guevara, Sergio [Laboratorio de Analisis por Activacion Neutronica, Centro Atomico Bariloche, 8400 Bariloche (Argentina); Sanchez, Maria Lidia [Universidad Nacional de Rio Cuarto, 5800 Rio Cuarto (Argentina); Arribere, Maria [Laboratorio de Analisis por Activacion Neutronica, Centro Atomico Bariloche, 8400 Bariloche (Argentina)


    Well preserved volcanic ashes produced in recent events, recovered from sedimentary sequences extracted from three lakes belonging to Nahuel Huapi National Park, Northern Patagonia, were geochemically characterized in order to reveal patterns that allow the identification of the source. Two water bodies are situated in the direct impact area of volcanoes Calbuco and Puyehue-Cordon Caulle, while the third, lake Moreno, is situated in-between. The sedimentary sequences were dated by {sup 210}Pb and {sup 137}Cs techniques; the elemental composition was determined by Instrumental Neutron Activation Analysis. Distinctive patterns were found out when comparing glass shards, and also white pumice but in a lesser degree, of tephra layers extracted from lake Ilon, related mostly to volcano Calbuco events, and lake Nahuel Huapi (Brazo Rincon site), associated to Puyehue-Cordon Caulle eruptions. The geochemical parameters that showed decisive differences were SiO{sub 2} and Na{sub 2}O+K{sub 2}O contents, the Eu anomaly, Rare Earth element ratios; the concentration of incompatible elements Cs, Rb, Th, Hf, Ta and Zr, and the compatible elements Cr and V. The six upper tephra layers extracted from lake Moreno showed geochemical patterns that allowed clear association with Calbuco and Puyehue-Cordon Caulle sources. These results set up the base for tephrochronological applications in historical periods in Nahuel Huapi National Park area.

  16. Optimization of a procedure for rebonding dislodged orthodontic brackets. (United States)

    Mui, B; Rossouw, P E; Kulkarni, G V


    The purpose of this study was to compare shear bond strength (SBS) of bonded and rebonded orthodontic brackets following a variety of commonly used conditioning treatments and using both light-cured and self-cured composite resin systems. Brackets debonded during the initial determination of SBS were rebonded after the removal of residual resin from enamel surfaces using five different treatments: (1) Remove residual resin using a tungsten carbide bur, re-etch enamel surface, then bond a new bracket; (2) Remove resin from the base mesh with micro-etching then rebond the same bracket, (3) Remove residual resin from the enamel surface using resin-removing pliers, recondition the enamel with an air-powder polisher, then bond a new bracket; (4) Remove residual resin using a rubber cup and pumice, then bond a new bracket; (5) Remove residual resin using pliers alone, then bond a new bracket. The results revealed that the light-cured system produced higher shear bond strength in the initial bond than the self-cured system (ptungsten carbide bur and acid-etching gave the highest SBS (difference 5.8 MPa; pfracture characteristics. The data suggest that the optimal procedure for rebonding dislodged orthodontic brackets is to resurface the enamel using a tungsten carbide bur, acid-etch the enamel, and use a new or re-use an old bracket after microetching.

  17. Kinetics of organic removal in fixed-bed aerobic biological reactor. (United States)

    Borghei, S M; Sharbatmaleki, M; Pourrezaie, P; Borghei, G


    The process kinetics of a lab-scale upflow aerobic immobilized biomass (UAIB) reactor using simulated sugar-manufacturing wastewater as feed was investigated. The experimental unit consisted of a 22l reactor filled with high porosity pumice stone. The UAIB reactor was tested under different organic loads and different hydraulic retention times (HRT) and the substrate loading removal rate was compared with prediction of Stover-Kincannon model, second-order model and the first order substrate removal model. After obtaining steady-state conditions, organic loading rate was increased from 750 to 4500 g COD/m(3) day to resemble wastewater from sugar production lines, and hydraulic retention time was decreased from 1 to 0.5 days, stepwise. Nine different operational conditions were applied changing these two parameters in a certain program. As a result of the calculations, Stover-Kincannon model and second-order model known as "Grau" model were found to be the most appropriate models for this reactor. Stover-Kincannon model and Grau second-order model gave high correlation coefficients, which were 99.7% and 99.4%, respectively. Therefore, these models could be used in predicting the behavior or design of the UAIB reactors.

  18. Tephrochronology of a 70 ka-long marine record in the Marsili Basin (southern Tyrrhenian Sea) (United States)

    Tamburrino, S.; Insinga, D. D.; Pelosi, N.; Kissel, C.; Laj, C.; Capotondi, L.; Sprovieri, M.


    A sequence of tephra layers is studied in a 13.9 m-long deep-sea core (MD01-2474G) from the southern Tyrrhenian Sea. The chronology of the succession is provided by a high-resolution age-depth model based on isotope stratigraphy and AMS radiocarbon dating, which place the succession of events in a time interval spanning the last 70 ka. Based on a precise chronological framework and proximal-distal correlations, the Y-1, Y-6 and Y-7 main marker tephras were identified. Compositional data on fresh micro-pumice or glass shards of selected tephras were correlated with the coeval volcanic activity of Aeolian Arc (Vulcano and Salina), Mt. Etna, Phlegrean Fields Pantelleria and Ischia. The tephra sequence contains a number of deposits documenting recurrent activity on Vulcano Island at ca. 6.9 ka BP (MD3), ca. 16.7 ka BP (MD11), ca. 23.2 ka BP (MD14), ca. 29.6 ka BP (MD15), ca. 36.9 ka BP (MD22) and ca. 42.5 ka BP (MD27). The results presented in this study improve the southern Tyrrhenian Sea tephrostratigraphic framework and provide new insights into chemistry and dispersal area of Aeolian Arc pyroclastic deposits in this sector of the Central Mediterranean.

  19. Social creation of Risk: Flood and Land Subsidence in Guadalajara Metropolitan Zone, México (case study) (United States)

    Zarate-Del Valle, P. F.; Vargas Del Río, D.


    Sanitary sewer of Guadalajara Metropolitan Zone (GMZ) is a project designed in early 1960s for discharges of one million inhabitants, precipitation forecast based in return periods of 25 years, and inflow coefficients based in agricultural land use for areas not yet urbanized. However, population increase —over 400% in 50 years— and associated urbanization modified original design conditions and present discharges have been doubled, exceeding its capacity. On the other hand, the lowest site of GMZ corresponds to the bed of the river San Juan de Dios (1488 m asl) in the historical center of Guadalajara City; meaning it that the pluvial waters in GMZ —because of the lack of an adequate sewer and the presence of physical barriers like buildings, streets, etc.— run superficially. As a consequence, seasonally floods in many places of the GMZ are common. GMZ (20° 40.5’N, 103°20.8’W; ~700 km2; ~4.5M inhabitants; ~1520 m asl in western Mexico) is located 25 km (N90°) far from La Primavera volcanic complex (LP). LP was emplaced at Late Pleistocene and it is made of lavas, air-fall pumice and ash flows of rhyolitic composition knowed as Tala Tuff (TT): an aphyric non welded ash flow erupted by LP, composed by glassy or aphanitic material pumice dominant (> 90%), with a lesser proportion of sand-sized clasts, lythic gravel and broken crystals. Outcrops of LP extend to the basins surrounding it including the basement of most of the GMZ. Maximum thickness of TT is close to 600 m near LP, at western and southern part of GMZ, whereas in northern and eastern GMZ it can be only a few meters. Interaction of drainage and lithology of TT in GMZ conforms an erosional pattern with dendritic drainage pattern and development of creeks- Many of these creeks have been used as sanitary landfills for municipal waste of refilled with lack of control or selection of the fill material; while new residential developments were constructed over them. In this context, besides the

  20. Explosive Origins of Welded Block and Ash Flow Deposits (United States)

    Andrews, G. D.; Michol, K.; Russell, K.


    The 2360 years B. P. eruption of Mount Meager, British Columbia, Canada, produced a succession of rarely- observed, welded block and ash flow deposits and non-welded equivalents, the Pebble Creek Formation. The welded block and ash flow deposits result from accumulation in a narrow, confined river valley; the accumulation was sufficiently rapid to keep the deposits above their glass transition temperature thereby allowing the succession to weld as a single cooling unit. The average integrated strain for vertical sections of the deposit is 31% implying > 50 m shortening of the thickest deposit (from 162 m to the current 112 m). Observations made in the field were supplemented by textural studies with the SEM and microscope, before being quantified by image analysis software. These data were then added to with measurements of connected and isolated porosity from the He-pycnometer at UBC. Only through the integration of these related data sets were we able to explore two significant findings: (1) Unconsolidated deposits have an average matrix porosity of ~41% and clasts have an average porosity of ~32%. Isolated porosity is pervasive (< 8%) in juvenile clasts, but is near absent in samples of matrix (< 1%). Welding and compa