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1.
Domenico Maria Doronzo 《Natural Hazards》2010,55(2):177-179
Particle-laden turbulent flows, called dilute pyroclastic density currents, can be generated during explosive volcanic eruptions.
They are the most hazardous events of interaction with buildings and human environments in volcanic areas. A qualitative comparison
with the dusty turbulent shear currents generated after the Twin Towers collapse on September 11, 2001 shows that turbulent,
multiphase flow-building interaction causes flow separation and recirculation around the buildings. This simple idea could
be applied to dilute pyroclastic density currents, and improved in future by adhoc numerical simulations of flow-building
interaction. 相似文献
2.
The mobility of gravity-driven granular flows such as debris flows or pyroclastic density currents are extremely sensitive
to topographic changes, such as break in slopes, obstacles, or ravine deviations. In hazard assessment, computer codes can
reproduce past events and evaluate hazard zonation based on inundation limits of simulated flows over a natural terrain. Digital
Elevation Model (DEM) is a common input for the simulation algorithm and its accuracy to reproduce past flows is crucial.
In this work, we use TITAN2D code to reproduce past block-and-ash flows at Colima volcano (Mexico) over DEMs with different
cell size (5, 10, 30, 50, and 90 m) in order to illustrate the influences of the resolution on the numeric simulations. Our
results show that topographic resolution significantly affects the flow path and runout. Also, we found that simulations of
past flows with the same input parameters (such as the basal friction angle) over topography with different resolutions resulted
in different flow paths, areas, and thickness of the simulated flows. In particular, the simulations performed with the 5-
and 10-m DEMs produced similar results. Also, we obtained consistent simulation results for the 30- and 50-m DEMs. However,
for the coarser 90-m DEM results are largely different and inaccurate. We recommend generating a benchmark table in order
to acquire characteristic values for the basal friction angle of studied events. In case of rugged topographies, a DEM with
high resolution should be used for more confident results. 相似文献
3.
Pierfrancesco Dellino Fabio Dioguardi Domenico M. Doronzo Daniela Mele 《Sedimentology》2019,66(1):129-145
Large‐scale experiments generating ground‐hugging multiphase flows were carried out with the aim of modelling the rate of sedimentation, of pyroclastic density currents. The current was initiated by the impact on the ground of a dense gas‐particle fountain issuing from a vertical conduit. On impact, a thick massive deposit was formed. The grain size of the massive deposit was almost identical to that of the mixture feeding the fountain, suggesting that similar layers formed at the impact of a natural volcanic fountain should be representative of the parent grain‐size distribution of the eruption. The flow evolved laterally into a turbulent suspension current that sedimented a thin, tractive layer. A good correlation was found between the ratio of transported/sedimented load and the normalized Rouse number of the turbulent current. A model of the sedimentation rate was developed, which shows a relationship between grain size and flow runout. A current fed with coarser particles has a higher sedimentation rate, a larger grain‐size selectivity and runs shorter than a current fed with finer particles. Application of the model to pyroclastic deposits of Vesuvius and Campi Flegrei of Southern Italy resulted in sedimentation rates falling inside the range of experiments and allowed definition of the duration of pyroclastic density currents which add important information on the hazard of such dangerous flows. The model could possibly be extended, in the future, to other geological density currents as, for example, turbidity currents. 相似文献
4.
《Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy》1999,24(11-12):957-961
The process of magma ascent along volcanic conduits during explosive eruptions is numerically simulated by solving the transport equations in the one-dimensional, steady, and isothermal assumptions. The physical model considers the non-equilibrium multiphase flow of a mixture of liquid magma, crystals and/or lithic fragments, and exsolving gas. The liquid magma is treated as a mixture of 10 major oxides plus dissolved water and carbon dioxide, and the gas phase as a mixture of water and carbon dioxide. The model is characterized by a strong coupling between fluid dynamic and constitutive equations, whereby the magma properties like viscosity, density, and gas solubility are calculated on the basis of the chemical composition of the liquid magma and its crystal content, and of the physical conditions along the volcanic conduit. The model predictions obtained by considering many different eruptive conditions reveal complex and sometimes non-intuitive relations between the initial conditions and the predicted flow parameter distribution. The composition of the liquid magma and the amount and composition of volatiles are found to be of major importance in determining the dynamics of magma ascent during explosive eruptions. The results of this modeling can be useful to forecast the volcanic hazard at a given volcano, as the conduit exit flow parameters could constitute initial conditions to study the atmospheric dispersion of the gas-pyroclasts and the dynamics of pyroclastic flows. 相似文献
5.
Pyroclastic surge is a dilute and turbulent flow of volcanic gas and tephra that is commonly generated during explosive volcanic eruptions and can threaten lives along its flow paths. Assessing its travel distance and delineating future volcanic hazards have therefore been major concerns of volcanologists. Historical eruptions show that most pyroclastic surges travel a few tens of kilometres or less from their sources. Aeolian or aquagene processes have therefore been evoked for the emplacement of supposed surge deposits much beyond this distance. Here we show that a Cretaceous tuff bed in Korea was emplaced by an exceptionally powerful pyroclastic surge that flowed as far as the most powerful pyroclastic flows that formed the low-aspect-ratio ignimbrites (LARI). This has significant implications for interpreting ancient volcanic eruptions and delineating volcanic hazards by pyroclastic surges, and casts intriguing questions on the eruption dynamics and physics of long-runout pyroclastic surges and their distinction from LARI-forming pyroclastic flows. 相似文献
6.
实验模拟侧向遮挡对低密度火山碎屑流的影响——对日本云仙岳火山1991年火山碎屑流的启示 总被引：1，自引：1，他引：0
本文将颗粒驱动重力流实验流体与自然界低密度火山碎屑流进行标度化研究,探讨低密度火山碎屑流的流动行为。通过在矩形流体交换水箱中放置占水箱宽度1/4、1/2、3/4比例的侧向遮挡障碍物,调查了颗粒驱动重力流实验流体在遇到侧向遮挡前后的运动模式、流体前锋速度减速特征和颗粒堆积分布特征。实验结果显示出不同比例的部分遮挡对低密度火山碎屑流影响的复杂性。实验表明,1/4比例的部分遮挡能够提高低密度火山碎屑流在通过之后的流速,并增加通过遮挡的颗粒堆积总量,能够解释日本云仙岳火山1991年6月3日喷发形成的碎屑流流动特征。在侧向遮挡比例为1/2时,~100T的时间内流体前锋减速,并在~100T之后加速（T为无量纲时间）;通过遮挡的堆积物总量明显减少。通过3/4比例的侧向遮挡之后,颗粒实验流体前锋持续减速,颗粒堆积总量减少。 相似文献
7.
Sheridan Michael F. Hubbard Bernard Carrasco-núñez Gerardo Siebe Claus 《Natural Hazards》2004,33(2):209-221
Volcán Citlaltépetl (Pico de Orizaba) with an elevation of 5,675 m is the highest volcano in North America. Its most recent catastrophic events involved the production of pyroclastic flows that erupted approximately 4,000, 8,500, and 13,000 years ago. The distribution of mapped deposits from these eruptions gives an approximate guide to the extent of products from potential future eruptions. Because the topography of this volcano is constantly changing computer simulations were made on the present topography using three computer algorithms: energy cone, FLOW2D, and FLOW3D. The Heim Coefficient (), used as a code parameter for frictional sliding in all our algorithms, is the ratio of the assumed drop in elevation (H) divided by the lateral extent of the mapped deposits (L). The viscosity parameter for the FLOW2D and FLOW3D codes was adjusted so that the paths of the flows mimicked those inferred from the mapped deposits. We modeled two categories of pyroclastic flows modeled for the level I and level II events. Level I pyroclastic flows correspond to small but more frequent block-and-ash flows that remain on the main cone. Level II flows correspond to more widespread flows from catastrophic eruptions with an approximate 4,000-year repose period. We developed hazard maps from simulations based on a National Imagery and Mapping Agency (NIMA) DTED-1 DEM with a 90 m grid and a vertical accuracy of ±30 m. Because realistic visualization is an important aid to understanding the risks related to volcanic hazards we present the DEM as modeled by FLOW3D. The model shows that the pyroclastic flows extend for much greater distances to the east of the volcano summit where the topographic relief is nearly 4,300 m. This study was used to plot hazard zones for pyroclastic flows in the official hazard map that was published recently. 相似文献
8.
长白山火山灾害及其对大型工程建设的影响 总被引：2，自引：0，他引：2
长白山火山是世界著名的活火山,历史时期有过多次喷发,有再次爆发的危险.长白山火山最大的一次爆发发生在公元1199-1200年,这次大爆发的火山灰最远到达距其1 000km远的日本北部.依据这次大爆发由火山喷发空中降落堆积物、火山碎屑流和火山泥流造成的巨大火山灾害,预测了长白山火山未来爆发火山灾害的类型、强度和范围,并编制了长白山火山未来爆发火山喷发空中降落堆积物灾害预测图、火山碎屑流灾害预测图和火山泥流灾害预测图.该研究可预防和减轻火山灾害,指导核电站等大型工程选址. 相似文献
9.
10.
火山碎屑密度流是一种危险的火山活动现象,也是一种重要的盆地物源供给方式,对其沉积机制的研究具有灾害预防和油气勘探的双重意义。松辽盆地东南隆起区九台营城煤矿地区白垩系营城组古火山机构保存良好,发育有典型的火山碎屑密度流沉积物。本文在精细刻画火山碎屑岩的岩石结构、沉积构造的基础上,运用薄片观察和沉积物粒度统计的方法,从物质来源、搬运机制和就位方式角度系统地分析了火山碎屑密度流的整个沉积过程,并结合国内外火山学、沉积学的研究进展探讨了不同浓度火山碎屑密度流的沉积机制。研究区内的火山碎屑密度流沉积物可以划分为五种微相:①块状熔结角砾凝灰岩微相;②无序含集块凝灰角砾岩微相;③逆粒序或双粒序角砾凝灰岩微相;④正粒序角砾凝灰岩微相;⑤韵律层理凝灰岩微相。第一种微相具有熔结结构,可能形成于高挥发分岩浆喷发柱的垮塌,火山碎屑密度流的就位温度较高;后四种微相具有正常火山碎屑岩结构,可能形成于火山口的侧向爆炸,火山碎屑密度流的就位温度中等。沉积块状熔结角砾凝灰岩微相的火山碎屑密度流具有黏性碎屑流的流体特征,沉积物整体冻结就位;沉积无序含集块凝灰角砾岩微相和逆粒序或双粒序角砾凝灰岩微相的火山碎屑密度流具有颗粒流的流体特征,沉积物整体冻结就位;沉积正粒序角砾凝灰岩微相和韵律层理凝灰岩微相的火山碎屑密度流具有湍流的流体特征,沉积物连续加积就位。火山碎屑密度流的颗粒浓度是一个连续变量,但流体性质可能会发生突变,稀释的火山碎屑密度流的沉积机制符合下部流动边界模型,稠密的火山碎屑密度流的沉积机制符合层流(碎屑流或颗粒流)模型。 相似文献
11.
Robert Eymard Cindy Guichard Raphaele Herbin Roland Masson 《Computational Geosciences》2012,16(4):987-1005
This paper concerns the discretisation on general 3D meshes of multiphase compositional Darcy flows in heterogeneous anisotropic porous media. Extending Coats’ formulation [15] to an arbitrary number of phases, the model accounts for the coupling of the mass balance of each component with the pore volume conservation and the thermodynamical equilibrium and dynamically manages phase appearance and disappearance. The spatial discretisation of the multiphase compositional Darcy flows is based on a generalisation of the Vertex Approximate Gradient scheme, already introduced for single-phase diffusive problems in [24]. It leads to an unconditionally coercive scheme for arbitrary meshes and permeability tensors. The stencil of this vertex-centred scheme typically comprises 27 points on topologically Cartesian meshes, and the number of unknowns on tetrahedral meshes is considerably reduced, compared with the usual cell-centred approaches. The efficiency of our approach is exhibited on several examples, including the nearwell injection of miscible CO2 in a saline aquifer taking into account the vaporisation of H2O in the gas phase as well as the precipitation of salt. 相似文献
12.
| 1. | Cumulic soils: Rakata: soils mainly derived from the re-deposited 1883 pyroclastic flows. Sertung: several layers of scoria and volcanic ash originating from Anak Krakatau are deposited on the pyroclastic flows. Panjang; cumulic stratification is similar to that of Sertung but the scoria layers are relatively thin compared with those of Sertung. |
| 2. | Properties of the soils. (a) Soil textures of the 1883 pyroclastic flow soils are finer than that of the soil originating from Anak Krakatau deposits. (b) Carbon contents of surface soils on Rakata are about 9% but those of the other soils are below 2%. pHs(N-KC1) of surface —and buried — A horizon originating from pyroclastic flows are about 4.5–5.6. (c) Smectite exists in the clay fraction of sub soils originating from pyroclastic flows but crystalline clay minerals are not detected in the surface soils on Rakata nor in soils originating from Anak Krakatau deposits. (d) The contents of inorganic N and exchangeable K in the soils on Panjang are higher than those on Sertung, and plant succession on Panjang has progressed more rapidly than on Sertung. |
| 3. | Compared with Krakatau soils, Japanese young volcanic ash soils have progressed more rapidly to Andisol than have soils originating from the Anak Krakatau deposits. The clay content of Japanese pyroclastic flows is less than that of Krakatau pyroclastic flows. |
13.
Turbidity currents and pyroclastic density currents may originate as stratified flows or develop stratification during propagation. Analogue, density‐stratified laboratory currents are described, using layers of salt solutions with different concentrations and depths to create the initial vertical stratification. The evolving structure of the flow depends on the distribution of the driving buoyancy between the layers, B* (proportional to the layer volumes and densities), and their density ratio, ρ*. When the lower layer contains more salt than the upper layer, and so has a greater proportion of the driving buoyancy (B* < 0·5), this layer can run ahead leading to streamwise or longitudinal stratification (ρ*→0), or the layers can mix to produce a homogeneous current (ρ*→1). If the upper layer contains more salt and thus buoyancy (B* > 0·5), this layer travels to the nose of the current by mixing into the back of the head along the body/wake density interface to produce a homogeneous flow (ρ*→1) or overtaking, leading to streamwise stratification (ρ*→0). Timescales describing the mixing between the layers and the streamwise separation of the layers are used to understand these flow behaviours and are in accordance with the experimental observations. Distance–time measurements of the flow front show that strongly stratified flows initially travel faster than weakly stratified flows but, during their later stages, they travel more slowly. In natural flows that are stratified in concentration and grain size, internal features, such as stepwise grading, gradual upward fining and reverse grading, could be produced depending on B* and ρ*. Stratification may also be expected to affect interactions with topography and overall fan architecture. 相似文献
14.
《International Geology Review》2012,54(7):661-674
In western Anatolia, a thick volcanic succession of andesitic to rhyolitic lavas and volcaniclastic rocks crops out extensively. On Foça Peninsula, the westernmost part of the region, a dominantly rhyolitic sequence is exposed where massive rhyolites occur as dome or domelike stubby lava flows. These rhyolite domes vertically and laterally pass into blanketing volcaniclastic sequences. The gradational boundary relations and the facies characteristics of the surrounding volcaniclastic sequences indicate that the silicic domes directly intruded a subaqueous environment and were shattered upon sudden contact with water to form hyaloclastic blankets. In and around these rhyolite domes, we have defined six different volcanic and volcaniclastic facies, consisting of: (1) massive rhyolite; (2) massive perlite; (3) hyaloclastic breccias; (4) rhyolite pumice and lithic fragment-bearing volcaniclastic rocks; (5) subaqueous welded ignimbrites; and (6) brecciated perlite. The massive rhyolite facies have distinct structures from the centers to the peripheries of the domes and stubby lava flows. Massive lava facies gradually pass into hyaloclastic breccias and massive perlite facies, indicating water-magma interaction during the emplacement. Phreatomagmatic explosive activity and doming caused the subaqueous pyroclastic flows on the flanks of the volcanic center. Welding in the upper parts of these pyroclastic flow deposits indicates the high-temperature emplacement of the pyroclastic material and relatively slow cooling caused by the cushioning effect of the gas-vapor mixture and rapid deposition of younger pyroclastic units. 相似文献
15.
Geological and volcanological studies were performed in the Herculaneum excavations, 7 km west of Vesuvius, Italy, to reconstruct the main features of the pyroclastic density currents and the temporal sequence of the ad 79 eruptive events that destroyed and buried the town. The identification of two distinctive marker beds allows correlation of these deposits with the better‐known sequences to the south of Vesuvius, along the dispersal axis of the Plinian fall deposit. Detailed observations from stratigraphic sections show that the pyroclastic density current deposits are characterized by several sedimentary facies, each recording different depositional and emplacement mechanisms. Facies analysis reveals both lateral and vertical variations from massive to stratified deposits, which can be related to the combined effects of flow dynamics and local irregularities of the substratum at centimetre or metre scales. These topographic irregularities enhanced turbulence and allowed rapid transition from non‐turbulent to turbulent transport within the flow. Fabric data from these deposits, both from roof tile orientations and anisotropy magnetic susceptibility (AMS) analyses carried out on some of the pyroclastic deposits, suggest that the pyroclastic density currents were strongly affected by the presence of buildings. These obstacles probably caused deflection and separation of flows into multiple lobes that moved in different directions. 相似文献
16.
Guilhem Amin Douillet Benjamin Bernard Mlanie Bouysson Quentin Chaffaut Donald Bruce Dingwell Lukas Gegg Inga Hoelscher Ulrich Kueppers Clia Mato Vanille Ariane Ritz Fritz Schlunegger Patrick Witting 《Sedimentology》2019,66(5):1531-1559
Pyroclastic currents are catastrophic flows of gas and particles triggered by explosive volcanic eruptions. For much of their dynamics, they behave as particulate density currents and share similarities with turbidity currents. Pyroclastic currents occasionally deposit dune bedforms with peculiar lamination patterns, from what is thought to represent the dilute low concentration and fluid‐turbulence supported end member of the pyroclastic currents. This article presents a high resolution dataset of sediment plates (lacquer peels) with several closely spaced lateral profiles representing sections through single pyroclastic bedforms from the August 2006 eruption of Tungurahua (Ecuador). Most of the sedimentary features contain backset bedding and preferential stoss‐face deposition. From the ripple scale (a few centimetres) to the largest dune bedform scale (several metres in length), similar patterns of erosive‐based backset beds are evidenced. Recurrent trains of sub‐vertical truncations on the stoss side of structures reshape and steepen the bedforms. In contrast, sporadic coarse‐grained lenses and lensoidal layers flatten bedforms by filling troughs. The coarsest (clasts up to 10 cm), least sorted and massive structures still exhibit lineation patterns that follow the general backset bedding trend. The stratal architecture exhibits strong lateral variations within tens of centimetres, with very local truncations both in flow‐perpendicular and flow‐parallel directions. This study infers that the sedimentary patterns of bedforms result from four formation mechanisms: (i) differential draping; (ii) slope‐influenced saltation; (iii) truncative bursts; and (iv) granular‐based events. Whereas most of the literature makes a straightforward link between backset bedding and Froude‐supercritical flows, this interpretation is reconsidered here. Indeed, features that would be diagnostic of subcritical dunes, antidunes and ‘chute and pools’ can be found on the same horizon and in a single bedform, only laterally separated by short distances (tens of centimetres). These data stress the influence of the pulsating and highly turbulent nature of the currents and the possible role of coherent flow structures such as Görtler vortices. Backset bedding is interpreted here as a consequence of a very high sedimentation environment of weak and waning currents that interact with the pre‐existing morphology. Quantification of near‐bed flow velocities is made via comparison with wind tunnel experiments. It is estimated that shear velocities of ca 0·30 m.s?1 (equivalent to pure wind velocity of 6 to 8 m.s?1 at 10 cm above the bed) could emplace the constructive bedsets, whereas the truncative phases would result from bursts with impacting wind velocities of at least 30 to 40 m.s?1. 相似文献
17.
Volcanic activity commenced 18 July 1995 at SoufriereHills volcano and has led to the creation of a newlava dome, which has repeatedly collapsed between 1996and 1999 resulting in highly mobile pyroclastic flows. The majority of associated pyroclastic flow phenomenaare consistent with initiation by gravitationalcollapse as blocks fall from oversteepened flanks ofthe new dome. If gravity controls the energy transferof such collapses, then areas likely to be affectedcan be predicted on the basis of topography. We focuson `dense' flows initiated by non-explosive,gravitational collapse (`Merapi-type' pyroclasticflows) and employ a graphical computer model (Flow3D)written to simulate this type of volcanic flow. Theprogram constructs a digital terrain model based upona 3D network of (x, y, z) triplets, which serves as thebasis for the numerical computations. A synthetic domewas added to the topographic model to improve theaccuracy of the simulations. After estimating thesmall number of key adjustable parameters, simulatedflow pathways, runout distances, and velocitiesclosely approximated observed Merapi-type pyroclasticflows on Montserrat. These simulations demonstrate thevalidity of a simple kinematic method to model densepyroclastic flow phenomena. While the simulationspresented here do not elucidate additional physics ofpyroclastic flow phenomena, this type of modeling canbe completed easily and without extensivea priori knowledge of volcano-specific parameters otherthan topography. Accordingly, it may serve as a rapidand inexpensive first-order approach for initialhazard assessment. 相似文献
18.
火山碎屑岩是爆破性火山喷发行为的直接产物,不同的碎屑成分、粒度及结构反映了不同岩相的堆积动力学过程,对火山碎屑岩岩石学和岩相组合的研究发展成了以物理火山学为代表的现代火山学研究体系。作为火山爆发碎屑物质的集合,其中不同成因类型的火山碎屑物往往可以直接对应不同阶段火山作用动力学参数特征。火山碎屑物3个最基本的堆积物成因类型是火山碎屑降落物、火山碎屑流和火山碎屑涌浪。火山喷发时碎屑化过程主要涉及挥发分的出溶和岩浆碎屑化过程以及不同火山流体内部的碎屑化过程。对于岩浆喷发、射汽岩浆喷发以及射汽喷发的直接产物,火山碎屑岩在组成上都包含了岩浆破碎的同源碎屑、火山通道裹进的异源碎屑以及火山流体在地表流动时捕获的表生碎屑。火山碎屑定义为爆破性火山喷发的直接行为产物,而包括坡移、滑坡体、火山泥石流等火山降解过程的表生碎屑与熔岩流在自生、淬碎碎屑化过程产生的碎屑则被定义为火山质碎屑。火山岩岩相的建立,为20世纪80年代后期向火山学研究阶段的转变奠定了基础。在地质研究的基础上探索火山活动过程和控制机制的经验模型、实验模拟和数值模拟研究,其中流体动力学的介入对理解火山喷发的基本过程具有里程碑式的推动意义。由此形成的火山学是研究火山与火山喷发的形成机理、喷发过程和产物特性的科学。 相似文献
19.
火山碎屑岩是爆破性火山喷发行为的直接产物,不同的碎屑成分、粒度及结构反映了不同岩相的堆积动力学过程,对火山碎屑岩岩石学和岩相组合的研究发展成了以物理火山学为代表的现代火山学研究体系。作为火山爆发碎屑物质的集合,其中不同成因类型的火山碎屑物往往可以直接对应不同阶段火山作用动力学参数特征。火山碎屑物3个最基本的堆积物成因类型是火山碎屑降落物、火山碎屑流和火山碎屑涌浪。火山喷发时碎屑化过程主要涉及挥发分的出溶和岩浆碎屑化过程以及不同火山流体内部的碎屑化过程。对于岩浆喷发、射汽岩浆喷发以及射汽喷发的直接产物,火山碎屑岩在组成上都包含了岩浆破碎的同源碎屑、火山通道裹进的异源碎屑以及火山流体在地表流动时捕获的表生碎屑。火山碎屑定义为爆破性火山喷发的直接行为产物,而包括坡移、滑坡体、火山泥石流等火山降解过程的表生碎屑与熔岩流在自生、淬碎碎屑化过程产生的碎屑则被定义为火山质碎屑。火山岩岩相的建立,为20世纪80年代后期向火山学研究阶段的转变奠定了基础。在地质研究的基础上探索火山活动过程和控制机制的经验模型、实验模拟和数值模拟研究,其中流体动力学的介入对理解火山喷发的基本过程具有里程碑式的推动意义。由此形成的火山学是研究火山与火山喷发的形成机理、喷发过程和产物特性的科学。 相似文献
20.
The Irruputuncu is an active volcano located in northern Chile within the Central Andean Volcanic Zone (CAVZ) and that has produced andesitic to trachy-andesitic magmas over the last ∼258 ± 49 ka. We report petrographical and geochemical data, new geochronological ages and for the first time a detailed geological map representing the eruptive products generated by the Irruputuncu volcano. The detailed study on the volcanic products allows us to establish a temporal evolution of the edifice. We propose that the Irruputuncu volcanic history can be divided in two stages, both dominated by effusive activity: Irruputuncu I and II. The oldest identified products that mark the beginning of Irruputuncu I are small-volume pyroclastic flow deposits generated during an explosive phase that may have been triggered by magma injection as suggested by mingling features in the clasts. This event was followed by generation of large lava flows and the edifice grew until destabilization of its SW flank through the generation of a debris avalanche, which ended Irruputuncu I. New effusive activity generated lavas flows to the NW at the beginning of Irruputuncu II. In the meantime, lava domes that grew in the summit were destabilized, as shown by two well-preserved block-and-ash flow deposits. The first phase of dome collapse, in particular, generated highly mobile pyroclastic flows that propagated up to ∼8 km from their source on gentle slopes as low as 11° in distal areas. The actual activity is characterized by deposition of sulfur and permanent gas emissions, producing a gas plume that reaches 200 m above the crater. The maximum volume of this volcanic system is of ∼4 km3, being one of the smallest active volcano of Central Andes. 相似文献