Volcano Type Research Articles

Investigation of Size Sensitivity in the Hydrogen Production from Formic Acid over Carbon‐Supported Pd Nanoparticles

AbstractThe size effect in the hydrogen production from formic acid decomposition has been investigated using a series of carbon‐supported Pd NPs with different particle sizes ranging from 2.7 to 5.5 nm. A volcano type relationship between catalytic activity and NPs size was obtained. This result suggests that there is an optimum relative proportion of low‐ and high‐coordination surface atoms within a regular arrangement of the Pd NPs, which was achieved at 3.9 nm in diameter under the present experimental conditions. By performing calculations on the palladium crystallites, decomposition of formic acid is considered as a structure‐sensitive reaction, and high‐coordination sites principally act as catalytically active species in this size range. Kinetic isotope effect using HCOOD and DCOOH was well corresponded to the catalytic tendency. A kH/kD value obtained with Pd/C with optimal size was smallest among investigated, indicating the positive promoting effect in the rate‐determining C−H bond dissociation step from the Pd‐formate intermediate.

Seismic Envelope‐Based Detection and Location of Ground‐Coupled Airwaves from Volcanoes in Alaska

Abstract Volcanic explosions and other infrasonic sources frequently produce acoustic waves that are recorded by seismometers. Here we explore multiple techniques to detect, locate, and characterize ground‐coupled airwaves (GCA) on volcano seismic networks in Alaska. GCA waveforms are typically incoherent between stations, thus we use envelope‐based techniques in our analyses. For distant sources and planar waves, we use f ‐ k beamforming to estimate back azimuth and trace velocity parameters. For spherical waves originating within the network, we use two related time difference of arrival (TDOA) methods to detect and localize the source. We investigate a modified envelope function to enhance the signal‐to‐noise ratio and emphasize both high energies and energy contrasts within a spectrogram. We apply these methods to recent eruptions from Cleveland, Veniaminof, and Pavlof Volcanoes, Alaska. Array processing of GCA from Cleveland Volcano on 4 May 2013 produces robust detection and wave characterization. Our modified envelopes substantially improve the short‐term average/long‐term average ratios, enhancing explosion detection. We detect GCA within both the Veniaminof and Pavlof networks from the 2007 and 2013–2014 activity, indicating repeated volcanic explosions. Event clustering and forward modeling suggests that high‐resolution localization is possible for GCA on typical volcano seismic networks. These results indicate that GCA can be used to help detect, locate, characterize, and monitor volcanic eruptions, particularly in difficult‐to‐monitor regions. We have implemented these GCA detection algorithms into our operational volcano‐monitoring algorithms at the Alaska Volcano Observatory.

Geological and environmental controls on the change of eruptive style (phreatomagmatic to Strombolian-effusive) of Late Pleistocene El Caracol tuff cone and its comparison with adjacent volcanoes around the Zacapu basin (Michoacán, México)

The 28,300year BP (cal 32,300 BP) El Caracol tuff cone complex is one of the few phreatomagmatic volcanoes in the scoria-cone dominated Plio-Quaternary Michoacán-Guanajuato Volcanic Field (MGVF). It displays a shallow circular crater of ~1km in diameter that is filled with several meter-thick lava flows and is located between two NE–SW trending normal faults dipping NW. It lies directly on top of Pliocene lavas of the San Lorenzo shield volcano that forms part of a tectonic horst (topographic high) separating the Zacapu lake basin (1980m) in the south from the Río Angulo river valley (1760m) to the north. Detailed study of the tephra sequence indicates that the eruption occurred in two stages: 1) Weak phreatomagmatic, in which about 0.1–0.5km3 dense rock equivalent (DRE) of magma was issued within ~1 to 3months at the rate of 4–40m3/s, and 2) purely magmatic (Strombolian-effusive) during which the vent shifted slightly its position toward the NW, forming a small scoria cone (~100m high) on the crater rim of the tuff cone. From this scoria cone lava flows were issued, first into the tuff cone crater occupying its bottom, and subsequently toward the NW, down the outer flank of the tuff cone and into the plain, where they reached a distance of ~3.5km. During this stage ~0.6km3 DRE of magma was produced at the rate of ~4m3/s in a period of ~5months.Although El Caracol displays many features that are characteristic for a phreatomagmatic vent, its morphology, types of deposits, and its complex process of formation makes it strikingly different from the more typical case of the ~21,000year BP (cal 25,300 BP) Alberca de Guadalupe maar volcano, situated not far at the SE margin of the Zacapu basin. The latter was solely phreatomagmatic during the course of its eruption and is formed in its entirety by surge and fallout breccias consisting largely of xenolithic material. In contrast, at El Caracol the hydrogeological environment (namely the low groundwater flow gradient) did not allow for sustained water/magma interactions at ideal conditions (ratio of 0.2). Hence, the system soon dried out due to insufficient groundwater flow toward the eruption site and the eruption turned purely magmatic. This study shows that despite of its proximity to a large water reservoir (Zacapu lake basin) and similarities with Alberca de Guadalupe maar in regard to age, climate, magma composition, and tectonic environment, several other specific parameters play a crucial role in shaping a monogenetic phreatomagmatic volcano. The case of El Caracol (phreatomagmatic style followed by magmatic during the course of a monogenetic eruption) has been reported from other volcanic fields around the globe where it might have similar causes. Furthermore, the general scarcity of this type of volcanoes in the Michoacán–Guanajuato Volcanic Field implies that the conditions required for their formation are rarely met in this region.

Hydrothermal processes related to Triassic and Jurassic submarine basaltic complexes in northeastern Hungary and in the Dinarides and Hellenides

Comparative studies on hydrothermal alteration of submarine peperitic basalt occurrences related to the Triassic early rifting of the Neotethys were carried out in various parts of the Dinarides and Hellenides. The study areas included the displaced fragments of the Dinarides in the Darno Unit, NE Hungary, the Kalnik Mts in Croatia and the Vares-Smreka area in Bosnia and Herzegovina. In the Hellenides, similar environments were studied in the Stragopetra Mts., Greece. Jurassic pillow basalts formed in a back-arc-basin of the Neotethys were also studied (in the Szarvaskő Unit, NE Hungary, which also represents a displaced unit of Dinaridic origin). Within the submarine basaltic lava flows, six volcanic facies were distinguished. The hydrothermal alteration was characterized according to those facies. The first process was the albitization of the rock-forming plagioclase at ~300°C temperature in all localities. During the higher temperature stage of the subsequent cooling, chloritization in the ground mass is typical for all types of basalts, however chlorite and rarely quartz formed in the fractures and amygdales of the Triassic basalts, while chlorite, quartz and prehnite precipitated in the fractures of the Jurassic rocks. At lower temperatures of this cooling-related process, calcite is a common mineral filling up the larger amygdales, jig-saw type fractures and other open spaces, but some epidote, pumpellyite, prehnite and laumontite also occur in the Triassic basalts. The late stage alteration (happened at the lowest temperature) is characterized by argillitization at every locality. The observed hydrothermal alteration patterns also show slight differences according to the volcanic facies as a function of the distal/proximal setting in relation to the eruptive centers and the presence/absence of water-saturated and unconsolidated carbonate or siliciclastic sediments at the time of the emplacement of lava flows. The study revealed that the most important factors influencing mineralogy and zoning of hydrothermal alteration in these short living local hydrothermal systems are the rapid cooling of the hydrothermal fluid, the dominance of the not much evolved seawater as the source of hydrothermal fluid and the local, i.e. effective water/rock ratio, determined by the degree of fracturing in the rock. The mineralogical-textural peculiarities of the highly localized hydrothermal fluid/rock interaction in the studied submarine sea-mount type volcanoes are clearly different from the products of the large-scaled hydrothermal processes occurring at mid-oceanic ridges. Recognition of these differences is important in the evaluation of ore potential of Neotethyan realm or other areas with occurrences of submarine basaltic units

Tandem Lewis acid/Brønsted acid-catalyzed conversion of carbohydrates to 5-hydroxymethylfurfural using zeolite beta

We conduct a combined experimental and computational study to reveal the kinetics of tandem glucose isomerization and fructose dehydration to 5-hydroxymethylfurfural (HMF) over a bifunctional zeolite H-BEA-25 in water. The model accounts for multicomponent adsorption, homogeneous Brønsted acid catalyzed chemistry of fructose, intrinsic heterogeneous Lewis acid catalyzed isomerization, Brønsted acid catalyzed fructose dehydration, HMF rehydration, and humin formation chemistry. The octahedrally coordinated extra-framework Al sites catalyze glucose to fructose isomerization effectively. The activation energy for the isomerization in H-BEA-25 is between those reported for Ti-BEA and Sn-BEA. We reveal that tandem reactions exhibit multiple kinetic regimes. When a bifunctional catalyst with a fixed total number of acid sites is used (e.g., aluminosilicate zeolites), the HMF formation rate exhibits a volcano type curve vs. the Lewis to Brønsted acid site ratio. On the other hand, when the two types of sites are varied independently (e.g., in Sn-BEA and HCl), the HMF formation rate increases and then approaches a plateau with increasing Brønsted acid site density. These appear to be generic features of tandem reactions catalyzed by multiple or multifunctional catalysts. We show that materials with stronger sugar adsorption would produce HMF in significantly higher yields and higher rate than H-BEA. When HMF degradation reactions are suppressed, a ratio of Lewis to Brønsted acid sites of ∼0.3 maximizes the HMF rate produced from glucose and the HMF yield (which is predicted to be ∼60% at 130°C). These predictions provide a framework for understanding and improving tandem reactions catalyzed by heterogeneous catalysts.

Molecular Insight in Structure and Activity of Highly Efficient, Low-Ir Ir–Ni Oxide Catalysts for Electrochemical Water Splitting (OER)

Mixed bimetallic oxides offer great opportunities for a systematic tuning of electrocatalytic activity and stability. Here, we demonstrate the power of this strategy using well-defined thermally prepared Ir-Ni mixed oxide thin film catalysts for the electrochemical oxygen evolution reaction (OER) under highly corrosive conditions such as in acidic proton exchange membrane (PEM) electrolyzers and photoelectrochemical cells (PEC). Variation of the Ir to Ni ratio resulted in a volcano type OER activity curve with an unprecedented 20-fold improvement in Ir mass-based activity over pure Ir oxide. In situ spectroscopic probing of metal dissolution indicated that, against common views, activity and stability are not directly anticorrelated. To uncover activity and stability controlling parameters, the Ir-Ni mixed thin oxide film catalysts were characterized by a wide array of spectroscopic, microscopic, scattering, and electrochemical techniques in conjunction with DFT theoretical computations. By means of an intuitive model for the formation of the catalytically active state of the bimetallic Ir-Ni oxide surface, we identify the coverage of reactive surface hydroxyl groups as a suitable descriptor for the OER activity and relate it to controllable synthetic parameters. Overall, our study highlights a novel, highly active oxygen evolution catalyst; moreover, it provides novel important insights into the structure and performance of bimetallic oxide OER electrocatalysts in corrosive acidic environments.

Late Pleistocene Alberca de Guadalupe maar volcano (Zacapu basin, Michoacán): Stratigraphy, tectonic setting, and paleo-hydrogeological environment

The Late Pleistocene (~21,000yrBP) Alberca de Guadalupe maar is one of the few phreatomagmatic volcanoes occurring within the scoria-cone dominated Plio-Quaternary Michoacán-Guanajuato Volcanic Field. The scarcity of this type of volcano implies that conditions favoring their formation are rarely met in this region. We identify these factors by implementing current methods of investigation with emphasis on hydrogeological conditions. We present the stratigraphy (including a set of 40Ar/39Ar and 14C dates) of the SE margin of the Zacapu intermontane tectonic basin, where the maar just forms a hole (~1km in diameter, ~150m deep, bearing a ~9m deep lake) in the otherwise planar topography of the underlying early Pleistocene lava flows of the Cerro Pelón scoria cone. The maar is composed of typical phreatomagmatic surge deposits that are poorly sorted and rich in accidental lithics (>60wt.% of the deposit) with few juveniles (basaltic andesite, SiO2=54–58wt.%). The entire structure is cut by an ENE–WSW trending normal fault and is underlain by andesite lavas and silicic ignimbrites (partly inferred from xenoliths encountered in the maar deposits) that are Miocene to Early Pleistocene in age.The crater is at the center of a N–S elongated drainage basin surrounded by topographic highlands that channel water with high hydraulic pressure from most directions towards the location of the maar. This geometric configuration was already in existence at the time of the maar-forming eruption, but the climate was different. Colder and more humid conditions during the Last Glacial Maximum (Cw2-climate type, annual precipitation of >1000mm) favored the saturation of the fractured shallow aquifer system (hydraulic conductivity of 10−8 to 10−7m/s) that supplied sufficient groundwater at a high flow rate directed towards the center of the basin. Upon contact near surface (<200m) with the rising dike of basaltic andesite magma, the continuous supply of both dike-fed basaltic andesite magma and groundwater at an optimal ratio of 0.2 allowed explosive interaction for the entire duration of the eruption (17–57days) creating a >150m deep crater with steep inner walls and an underlying shallow diatreme (<300m). Since then, partial collapse of the walls along listric ring-fractures has reduced crater steepness. The present climate is much drier (Cw1 climate conditions with annual precipitation of 697.5–874.8mm) and it seems unlikely that a maar would form if these conditions persist. Nonetheless, precipitation is still high enough to sustain a ~9-m-deep lake in the crater with insignificant seasonal water table fluctuations. These findings lend further support to the notion that maars can be used as paleoclimate indicators in central Mexico.

Size Effect of Carbon-Supported Pd Nanoparticles in the Hydrogen Production from Formic Acid

Abstract Particle size dependence in the H2 production from formic acid was investigated over Pd/C catalysts with nanoparticle sizes ranging from 2.7 to 5.5 nm. A volcano type relationship between catalytic activity and nanoparticle size was obtained and the average size of 3.9 nm exhibited the highest activity under mild reaction conditions.

Hydrogen Electrocatalysis: From Mechanistic Study to Advanced Catalyst Development

H2-based polymer membrane fuel cells, electrolyzers and solar hydrogen generators are key components in a sustainable hydrogen economy. In particular, alkaline membrane based devices are promising alternatives to their acidic counterparts owing to the availability of earth-abundant metal catalysts for the oxygen reactions, while such catalysts have not been reported for the hydrogen reactions. Moreover, previous research on the hydrogen oxidation/evolution reactions (HOR/HER) on the state-of-the-art Pt catalysts has shown significantly reduced kinetics in alkaline environment than in acids, which projects an increased Pt loading in alkaline membrane based devices, and impedes their large scale commercialization.[ 1 ] Developing highly efficient and cost-effective catalysts for the HOR/HER in alkaline media requires identification of the true reaction mechanism of the HOR/HER. However there has been a substantial debate regarding the HOR/HER mechanism in strong bases, which has led to the different approaches in the rational HOR/HER catalyst design. A proposed bi-functional mechanism indicates that the co-existence of adsorbed H and adsorbed OH is required for the HOR/HER in bases[ 2 ] while others attribute the slower HOR/HER kinetics in bases to the strengthened hydrogen binding energy (HBE).[ 3 ] Our previous investigation of the HER on a variety of monometallic surfaces in an alkaline electrolyte shows that the exchange current densities follow a volcano type of relationship with respect to the calculated HBE, suggesting that the HBE is the dominating factor for H2 electrocatalysis in bases.[ 4 ] Furthermore, by examining the HOR/HER on Pt in a wide range pH-buffered solutions from 0 to 13, we demonstrate a monotonic relation between the HOR/HER activities and experimentally measured HBEs, showing decreasing HOR/HER activities with increasing HBEs.[ 5 ] This correlation further confirms that HBE is the sole reaction descriptor, and has to take a leading role in the highly efficient and cost-effective catalyst design. Motivated by these findings and the fact that Ni exhibits certain HOR activity in bases, we have developed NiMo bi-metallic and CoNiMo multi-metallic thin film catalysts. These novel thin film catalysts exhibit 20 fold enhancement of HOR/HER activities over pure Ni, owing to their much weakened HBE values.[ 6 ] These promising materials will greatly alleviate the catalyst cost issue raised by higher Pt loading in alkaline electrolytes, and will facilitate the development of alkaline or alkaline membrane fuel cell technology.

The rise and fall of continental arcs: Interplays between magmatism, uplift, weathering, and climate

Continental arcs, such as the modern Andes or the Cretaceous Sierra Nevada batholith, are some of the highest topographic features on Earth. Continental arc volcanoes may produce more CO2 than most other types of volcanoes due to the interaction of magmas with sedimentary carbonates stored in the continental upper plate. As such, global flare-ups in continental arc magmatism may amplify atmospheric CO2 concentrations, leading to climatic warming. However, the high elevations of continental arcs may also enhance orographic precipitation and change global atmospheric circulation patterns, possibly increasing the efficiency of chemical weathering and drawdown of atmospheric CO2, which may subdue the climatic warming response to volcanic activity. To better evaluate the climatic response, we develop models that integrate magmatic crustal thickening, topographic uplift, isostasy and erosion. The topographic response is used to predict how soil formation rates, soil residence times, and chemical weathering rates vary during and after a magmatic episode. Although magmatism leads to crustal thickening, which requires topographic uplift, highest elevations peak ∼10 My after magmatism ends. Relatively high elevations, which enhance erosion and chemical weathering of the continental arc, persist for tens of million years after magmatism ends, depending on erosion kinetics. It has recently been suggested that the Cretaceous–Paleogene greenhouse (high atmospheric CO2 and warm climate) coincided with a global chain of continental arcs, whereas mid- to late Cenozoic icehouse conditions (low atmospheric CO2 and cold climate) coincided with a lull in continental arc activity after 50 Ma. Application of our models to the Sierra Nevada (California, USA) continental arc, which represents a segment of this global Cretaceous–Paleogene continental arc, reproduces the observed topographic and erosional response. Our models require that the newly formed continental arc crust remained high and continued to erode and weather well after (>50 My) the end of magmatism. Thus, in the aftermath of a global continental arc flare-up, both the total volcanic inputs of CO2 decline and the average weatherability of continents increases, the latter due to the increased proportion of widespread remnant topography available for weathering and erosion. This combination leads to a decrease in the long-term baseline of carbon in the ocean/atmosphere system, leading to cooling. Mid-Cenozoic cooling is often attributed solely to increased weathering rates associated with India–Eurasian collision and the Himalayan orogeny. However, the total area of now-extinct Cretaceous–Paleogene continental arcs is 1.3–2 times larger than that of the Himalayan range front and the Tibetan plateau combined, suggesting that weathering of these remnant volcanic arcs may also play a role in drawing down CO2 through silicate weathering and subsequent carbonate burial. In summary, if global continental arc flare-ups lead to greenhouse conditions, long-lived icehouse conditions should follow in the aftermath due to decreased CO2 inputs and an increase in regional weathering efficiency of remnant arc topography.

Transport and mixing dynamics from explosions in debris-filled volcanic conduits: Numerical results and implications for maar-diatreme volcanoes

Most volcanoes experience some degree of phreatomagmatism during their lifetime. However, the current understanding of such processes remains limited relative to their magmatic counterparts. Maar-diatremes are a common volcano type that form primarily from phreatomagmatic explosions and are an ideal candidate to further our knowledge of deposits and processes resulting from explosive magma–water interaction due to their abundance as well as their variable levels of field exposure, which allows for detailed mapping and componentry. Two conceptual models of maar-diatreme volcanoes explain the growth and evolution of the crater (maar) and subsurface vent (diatreme) through repeated explosions caused by the interaction of magma and groundwater. One model predicts progressively deepening explosions as water is used up by phreatomagmatic explosions while the other allows for explosions at any level in the diatreme, provided adequate hydrologic conditions are present. In the former, deep-seated lithics in the diatreme are directly ejected and their presence in tephra rings is often taken as a proxy for the depth at which that particular explosion occurred. In the latter, deep-seated lithics are incrementally transported toward the surface via upward directed debris jets. Here we present a novel application of multiphase numerical modeling to assess the controls on length scales of debris jets and their role in upward transport of intra-diatreme material to determine the validity of the two models. The volume of gas generated during a phreatomagmatic explosion is a first order control on the vertical distance a debris jet travels. Unless extremely large amounts of magma and water are involved, it is unlikely that most explosions deeper than ∼250 m breach the surface. Other factors such as pressure and temperature have lesser effects on the length scales assuming they are within realistic ranges. Redistribution of material within a diatreme is primarily driven by subsidence following debris jet passage. Natural debris jet deposits often contain wall rock material that originated above the explosion site; likely this material was first transported downward by subsidence associated with preceding explosions and debris jets. The length scales of debris jets decrease with increasing depth, all other factors staying equal. The characteristics of the domains formed from just one explosion along with the difficulty of erupting deep-seated material indicate that erupted material at maar-diatreme volcanoes has a complex history before it is erupted and is mostly sourced from the upper-most part of the diatreme.

Enhancement of the Oxygen Reduction on Nitride Stabilized Pt-M (M = Fe, Co and Ni) Core-Shell Nanoparticle Electrocatalysts

Given the harsh operating conditions in hydrogen/oxygen fuel cells, there has been considerable efforts to make Pt(M) alloy nanoparticles as a stable oxygen reduction reaction (ORR) catalyst that have had a marginal success. Core-shell catalysts have unique properties of reducing the precious metal for the reaction and at the same time increasing the ORR activity by combined geometrical and electronic effects. Multiple mechanism has been proposed to explain the enhanced ORR activity of Pt(M) alloys. Watanabe et al. had explained the enhanced ORR activity based on the lattice parameter changes by alloying non-precious metals to Pt. Their results showed that the ORR activity increased in the order of PtFe/C > PtCo/C > PtNi/C, whereas the calculated lattice parameter decreased in the order of PtFe/C < PtCo/C < PtNi/C. Mukerjee et al. investigated the enhancement mechanism on some PtM alloys for the ORR by using XANES and EXAFS. Based on the d-band calculations that decreased in the order of PtFe/C < PtCo/C < PtNi/C, the ORR activity increased in the order of PtFe/C > PtCo/C > PtNi/C. So overall the trend in ORR activity for Pt(M) alloy nanoparticles have been in the order of PtFe/C > PtCo/C > PtNi/C. Here we report on a new class of catalyst consisting of nitride metal cores enclosed by thin Pt shells that can be easily synthesized. Our theoretical analysis and the experimental data indicate that metal nitride nanoparticle cores could significantly enhance the ORR activity as well as the durability of the core-shell catalysts as a consequence of combined geometrical, electronic and segregation effects on the Pt shells. Adding nitride metal in the core increases the ORR activity in the order of PtNiN/C > PtFeN/C > PtCoN/C. DFT calculations have shown a volcano type behavior with PtNiN/C at the top of the curve revealing the fact that, among the catalysts investigated, it has the best combination of both the surface strain and d-band center shifts. Figure 1

The association of lava dome growth with major explosive activity (VEI ≥ 4): DomeHaz, a global dataset

Investigation of the global eruptive records of particular types of volcanoes is a fundamental and valuable method of understanding what style of activity can be anticipated in the future and can highlight what might be expected or unusual in particular settings. This paper investigates the relationship between large explosions (volcanic explosivity index, VEI ≥ 4) and lava dome growth from 1000 AD to present and develops the DomeHaz database. DomeHaz contains information from 397 dome-forming episodes, including duration of dome growth, duration of pauses in extrusion, extrusion rates, and the timing and magnitude (VEI) of associated large explosions. Major explosive activity, when associated with dome growth, is more likely to occur before dome growth rather than during, or at the end of, dome-forming eruptions. In most cases where major explosive activity has been associated with dome growth, the eruptions occurred at basaltic andesite to andesitic volcanoes (the most common type of dome-forming volcano), but a greater proportion of dacitic and rhyolitic dome growth episodes were associated with large explosions. High extrusion rates (>10 m3 s−1) seem to be associated with large explosions and may inhibit degassing or destabilize existing domes, leading to explosive decompression. Large explosions may, alternatively, be followed by dome growth, which represents the clearing of residual magma from the conduit. Relationships extracted from the global record can be used to construct probability trees for new and ongoing dome-forming eruptions or can be used in conjunction with other types of event trees to aid in forecasting volcanic hazards during a crisis, especially for volcanoes where data are sparse.

ChemInform Abstract: Theory of Surface Chemistry and Reactivity of Reducible Oxides

AbstractReview: 115 refs.

全球热机带和冷机带火山活动的比较研究—兼论对热机带火山预测研究思路的改进

本文根据地震地热说的工作方法，采用Smithsonian Institution的火山资料、Mantleplumes网页的地幔柱资料以及作者的地震柱资料，以地震柱或地幔柱为构造单元和统计单元，对比分析了火山活动与热机带和冷机带的依存性、火山的喷发类型、火山的兴衰史，并讨论了火山的成因和热机带火山预测的可能性，从而为地震地热说火山预测方法的研究奠定了理论基础。研究结果表明，火山的成因与地幔内的地震柱和/或地幔柱有关，火山活动的能量与热物质的补给可能来自地幔的深部，从而构成两类性质差异的火山群落，地震柱型火山和地幔柱型火山，各自具有不同的活动方式与活动规律。热机带及其所包含的地震柱，是全球火山活动的主体，也是全球地质灾变的主体，与人类的生存休戚相关。因此，应该拓展火山的预测研究思路，加强对壳下地震活动的监测与研究，或许能解热机带内的火山预测之困。 According to the Seismo-geothermics working method and using the GVP volcanic material of Smithsonian Institution web, the mantle plume data of mantleplumes web and author’s seismic cone data, this article comparatively studied the dependency of volcanic activity with the hot engine belt and the cooling seismic belt, volcanic eruption type, the rise and fall of volcanic history by tectonic units and statistical unit of cones and plumes, and discussed volcanic origin and possibility of volcano prediction on the hot engine belt, which made the theoretical foundation of Seis-mo-geothermics volcano prediction method study. The study shows that the genesis of volcano is related to mantle hotspots, the seismic cone and/or the mantle plume. The energy and the thermal material of volcanic activity may come from the deep mantle, which constitute the two different types of volcanic communities called as cone type volcano and plume type volcano, and with dif-ferent mode and rule of activity respectively. The hot engine belt and seismic cones thereof are the main body of the global volcanic activity, and the main geological disaster in the world, which affects the human survival. Therefore, we should expand the volcanic prediction research ideas and strengthen the monitoring and study of subcrustal earthquake activity, which perhaps can bring some new hope of volcanic prediction difficulties on the hot engine belt.

Geochemical Characteristics and Genesis Discussion with Rock Metallogenic Belt of Geza Island Arc, Yunnan

Geza island arc located in the southwest Sanjiang tectonic igneous rock belts which was a products of Ganzi-Litang oceanic crust diving to Zhongdian Landmasses in late Triassic. Lithogeochemical characteristics shown that the porphyry(porphyrite) and island-arc granite rocks have the same rock series (high-K calc-alkaline) and the same genetic type (I-type granite); these rocks trace elements similar to the granite of island arc,which enriched in Ba, La, Hf, Au,chalcophile elements Cu,Pb, siderophile elements Mo, Ni, and depleted in Rb, Nb, P, Ti. In this region, the similarities of porphyry and local acidic volcanic rocks in the main elements, REE and other trace elements and the composition suggest that they both have the same or similar magmatic source rocks. It is shown that the characteristics of the rock with the island arc granite partial melting of source rock, that may come from the arc type volcano rock or island arc volcano rock cognate magma evolution.

Common processes at unique volcanoes—a volcanological conundrum

An emerging challenge in modern volcanology is the apparent contradiction between the perception that every volcano is unique, and classification systems based on commonalities among volcano morphology and eruptive style. On the one hand, detailed studies of individual volcanoes show that a single volcano often exhibits similar patterns of behaviour over multiple eruptive episodes; this observation has led to the idea that each volcano has its own distinctive pattern of behaviour (or “personality”). In contrast, volcano classification schemes define eruption “styles” referenced to “type” volcanoes (e.g. Plinian, Strombolian, Vulcanian); this approach implicitly assumes that common processes underpin volcanic activity and can be used to predict the nature, extent and ensuing hazards of individual volcanoes. Actual volcanic eruptions, however, often include multiple styles, and type volcanoes may experience atypical eruptions (e.g., violent explosive eruptions of Kilauea, Hawaii1). The volcanological community is thus left with a fundamental conundrum that pits the uniqueness of individual volcanic systems against generalization of common processes. Addressing this challenge represents a major challenge to volcano research.

Volcanic geomorphological classification of the cinder cones of Tenerife (Canary Islands, Spain)

This paper proposes a method to establish a morphological classification of Tenerife's cinder cones on the basis of a dual analysis of qualitative (existence, geometry and disposition of craters) and quantitative morphometric parameters (major and minor diameters and cone elongation, major and minor diameters and crater elongation). The result obtained is a morphological classification of the cinder cones of Tenerife, which can be sub-divided into four types: ring-shaped-cones, horseshoe-shaped-volcanoes, multiple volcanoes and volcanoes without crater. In Tenerife there is a clear dominance of horseshoe-shaped volcanoes (69.0%) over ring-shaped cones (13.1%), volcanoes without craters (11.4%) and multiple volcanoes (6.4%). The classification presented in this paper is characterized by its simplicity which makes it possible to include all morphological types of volcanoes found in Tenerife. This fact also renders our classification a useful tool to apply in other, both insular and continental volcanic areas to eventually analyze and systematize the study of eruptive edifices with similar traits.

An analysis of the issuance of volcanic alert levels during volcanic crises

Volcano Alert Levels (VALs) are used by volcanologists to quickly and simply inform local populations and government authorities of the level of volcanic unrest and eruption likelihood. Most VALs do not explicitly forecast volcanic activity but, in many instances they play an important role in informing decisions: defining exclusion zones and issuing evacuation alerts. We have performed an analysis on VALs (194 eruptions, 60 volcanoes) to assess how well they reflect unrest before eruption and what other variables might control them. We have also looked at VALs in cases where there was an increase in alert level but no eruption, these we term 'Unrest without eruption' (UwE). We have analyzed our results in the context of eruption and volcano type, instrumentation, eruption recurrence, and the population within 30 km. We found that, 19% of the VALs issued between 1990 and 2013 for events that ended with eruption accurately reflect the hazard before eruption. This increases to ~30% if we only consider eruptions with a VEI ≥ 3. VALs of eruptions from closed-vent volcanoes are more appropriately issued than those from open-vents. These two observations likely reflect the longer and stronger unrest signals associated with large eruptions from closed vents. More appropriate VAL issuance is also found in volcanoes with monitoring networks that are moderately-well equipped (3-4 seismometers, GPS and gas monitoring). There is also a better correlation between VALs and eruptions with higher population density. We see over time (1990 to 2013) that there was an increase in the proportion of `UwE’ alerts to other alerts, suggesting increasing willingness to use VALs well before an eruption is certain. The number of accurate VALs increases from 19% to 55% if we consider all UwE alerts to be appropriate. This higher `success’ rate for all alerts (with or without eruption) is improving over time, but still not optimal. We suggest that the low global accuracy of the issuance of VALs could be improved by having more monitoring networks equipped to a medium level, but also by using probabilistic hazard management during volcanic crisis.

Theory of surface chemistry and reactivity of reducible oxides

The increasing availability of computational data from quantum-chemical calculations on the reactivity and electronic structure of catalytically active oxidic systems make a revisitation of the classical questions on chemical bonding aspects of catalytically reactive systems useful.This Perspective paper starts with a short review of the different available systems. The elementary reactions that are part of the selective oxidation catalysis, such as substrate bond activation or oxygen insertion, are introduced.This is followed by a discussion of basic electronic features of the valence electron structure of oxide materials. We will initially compare the chemical bonding and reactivity of compounds with dominantly ionic versus covalent bonding. Surface reactivity descriptors for the two types of chemical bonds are indicated. It will appear that, except for longer range ionic interactions, binding to the metal cations is dominated by local covalent interactions and that ligand field theory type atomic orbital splitting as well as rehybridisation are important. Trends in bonding as a function of position of reducible metal in the periodic system are emphasized throughout the paper.At the surface, in addition to the changes in electronic structure, atom position relaxation and surface reconstruction effects may also have a large influence on the differences in reactivity.The reactivity of the oxygen atoms varies. They can be proton acceptors and generate Brønsted acidity, can assist heterolytic or radical type CH bond activation or when electrophilic will insert into hydrocarbon double bonds.At the end of the paper trends in catalytic reactivity are analyzed. The double volcano type curve found for the dependence of catalytic reactivity on the position of cation in the third row of the periodic system is shown to relate to the distribution of electrons with high spin over the ligand field split atomic orbitals of the respective cations. This will be discussed in the context of classical catalytic results that are based on Balandin type volcano plots of reactivity versus the catalyst material reactivity parameters.