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1.
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2.
A major seismic swarm occurred near Parícutin volcano between the end of May and early July 2006. More than 700 earthquakes with magnitude (M L ) exceeding 2.4 were located. Parícutin, located in the Michoacán–Guanajuato volcanic field in western Mexico, is well known as the site of the 1943 eruption in which a new 400 m cinder cone was constructed in what had been farmland. The 2006 swarm exhibits all of the characteristics typically associated with swarms of volcanic origins. The earthquake rate showed the typical ramp up and ramp down over the course of several days. Magnitudes were evenly distributed in time with a notably high b-value of 2.45. The earthquake locations cluster around a northeast-striking trend extending approximately 6 km. Over the first two weeks, hypocenters migrated steadily a few hundred meters per day, rising from 9 to 5 km depth and moving northeast about 5 km. On approximately June 7, the ascent of hypocenters stalled. For the next three weeks, hypocenters held their depth while migrating laterally back to the southwest. Focal mechanisms during the first part of the swarm reflected the increased stress caused by dike inflation. Following June 7, the stress orientation changed and became more consistent with the inflation of horizontal sill-like structures. Though only limited information is available from the seismic swarm preceding the 1943 eruption, several features, including the swarm duration and magnitude relationships, were comparable to those of the 2006 episode. The strong indicators of a magmatic origin to the 2006 swarm suggest that at this location there are few, if any, traditional seismic discriminants that could be used to distinguish which seismic swarms and dike emplacement events might culminate in eruption.  相似文献   

3.
At Cotopaxi volcano, Ecuador, rhyolitic and andesitic bimodal magmatism has occurred periodically during the past 0.5 Ma. The sequential eruption of rhyolitic (70–75% SiO2) and andesitic (56–62% SiO2) magmas from the same volcanic vent over short time spans and without significant intermingling is characteristic of Cotopaxi’s Holocene behavior. This study documents the eruptive history of Cotopaxi volcano, presenting its stratigraphy and geologic field relations, along with the relevant mineralogical and chemical nature of the eruptive products, in order to determine the temporal and spatial relations of this bimodal alternation. Cotopaxi’s history begins with the Barrancas rhyolite series, dominated by pumiceous ash flows and regional ash falls between 0.4 and 0.5 Ma, which was followed by occasional andesitic activity, the most important being the ample andesitic lava flows (∼4.1 km3) that descended the N and NW sides of the edifice. Following a ∼400 ka long repose without silicic activity, Cotopaxi began a new eruptive phase about 13 ka ago that consisted of seven rhyolitic episodes belonging to the Holocene F and Colorado Canyon series; the onset of each episode occurred at intervals of 300–3,600 years and each produced ash flows and regional tephra falls with DRE volumes of 0.2–3.6 km3. Andesitic tephras and lavas are interbedded in the rhyolite sequence. The Colorado Canyon episode (4,500 years BP) also witnessed dome and sector collapses on Cotopaxi’s NE flank which, with associated ash flows, generated one of the largest cohesive debris flows on record, the Chillos Valley lahar. A thin pumice lapilli fall represents the final rhyolitic outburst which occurred at 2,100 years BP. The pumices of these Holocene rhyolitic eruptions are chemically similar to those of older rhyolites of the Barrancas series, with the exception of the initial eruptive products of the Colorado Canyon series whose chemistry is similar to that of the 211 ka ignimbrite of neighboring Chalupas volcano. Since the Colorado Canyon episode, andesitic magmatism has dominated Cotopaxi’s last 4,400 years, characterized by scoria bomb and lithic-rich pyroclastic flows, infrequent lava flows that reached the base of the cone, andesitic lapilli and ash falls that were carried chiefly to the W, and large debris flows. Andesitic magma emission rates are estimated at 1.65 km3 (DRE)/ka for the period from 4,200 to 2,100 years BP and 1.85 km3 (DRE)/ka for the past 2,100 years, resulting in the present large stratocone.  相似文献   

4.
The 2007 effusive eruption of Stromboli followed a similar pattern to the previous 2002–2003 episode. In both cases, magma ascent led to breaching of the uppermost part of the conduit forming an eruptive fissure that discharged lava down the Sciara del Fuoco depression. Both eruptions also displayed a ‘paroxysmal’ explosive event during lava flow output. From daily effusion rate measurements retrieved from helicopter- and satellite-based infrared imaging, we deduce that the cumulative volume of lava erupted before each of the two paroxysms was similar. Based on this finding, we propose a conceptual model to explain why both paroxysms occurred after this ‘threshold’ cumulative volume of magma was erupted. The gradual decompression of the deep plumbing system induced by magma withdrawal and eruption, drew deeper volatile-rich magma into the conduit, leading to the paroxysms. The proposed model might provide a basis for forecasting paroxysmal explosions during future effusive eruptions of Stromboli.  相似文献   

5.
Nishinoshima, a submarine volcano in the Ogasawara Arc, approximately 1 000 km south of Tokyo, Japan, suddenly erupted in November 2013, after 40 years of dormancy. Olivine‐bearing phenocryst‐poor andesites found in older submarine lavas from the flanks of the volcano have been used to develop a model for the genesis of andesitic lavas from Nishinoshima. In this model, primary andesite magmas originate directly from the mantle as a result of shallow and hydrous melting of plagioclase peridotites. Thus, it only operates beneath Nishinoshima and submarine volcanoes in the Ogasawara Arc and other oceanic arcs, where the crust is thin. The primary magma compositions have changed from basalt, produced at considerable depth, to andesite, produced beneath the existing thinner crust at this location in the arc. This reflects the thermal and mechanical evolution of the mantle wedge and the overlying lithosphere. It is suggested that continental crust‐like andesitic magma builds up beneath submarine volcanoes on thin arc lithosphere today, and has built up beneath such volcanoes in the past. Andesites produced by this shallow and hydrous melting of the mantle could accumulate through collisions of plates to generate continental crust.  相似文献   

6.
Sierra Negra volcano began erupting on 22 October 2005, after a repose of 26 years. A plume of ash and steam more than 13 km high accompanied the initial phase of the eruption and was quickly followed by a ~2-km-long curtain of lava fountains. The eruptive fissure opened inside the north rim of the caldera, on the opposite side of the caldera from an active fault system that experienced an mb 4.6 earthquake and ~84 cm of uplift on 16 April 2005. The main products of the eruption were an `a`a flow that ponded in the caldera and clastigenic lavas that flowed down the north flank. The `a`a flow grew in an unusual way. Once it had established most of its aerial extent, the interior of the flow was fed via a perched lava pond, causing inflation of the `a`a. This pressurized fluid interior then fed pahoehoe breakouts along the margins of the flow, many of which were subsequently overridden by `a`a, as the crust slowly spread from the center of the pond and tumbled over the pahoehoe. The curtain of lava fountains coalesced with time, and by day 4, only one vent was erupting. The effusion rate slowed from day 7 until the eruption’s end two days later on 30 October. Although the caldera floor had inflated by ~5 m since 1992, and the rate of inflation had accelerated since 2003, there was no transient deformation in the hours or days before the eruption. During the 8 days of the eruption, GPS and InSAR data show that the caldera floor deflated ~5 m, and the volcano contracted horizontally ~6 m. The total eruptive volume is estimated as being ~150×106 m3. The opening-phase tephra is more evolved than the eruptive products that followed. The compositional variation of tephra and lava sampled over the course of the eruption is attributed to eruption from a zoned sill that lies 2.1 km beneath the caldera floor.  相似文献   

7.
A detailed survey of morphological and biological markers of paleo-shorelines has been carried out along the coastal sector of Mt. Etna volcano (eastern Sicily, Italy), in order to better define causes and timing of vertical deformation. We have mapped markers of raised Holocene shorelines, which are represented by beach rocks, wave-cut platforms, balanid, vermetid and algal rims. The timing of coastal uplift has been determined by radiocarbon dating of shells collected from the raised paleo-shorelines and, to correctly assess the total amount of tectonic uplift of the coast during the Late Holocene, we have compared the elevation-age data of sampled shells to the local curve of Holocene sea-level rise. Taking into account the nominal elevation of the associated paleo-shorelines, an uplift rate of 2.5–3.0 mm/year has been estimated for the last 6–7 ka. This general process of uplifting is only locally interrupted by subsidence related to flank sliding of the volcanic edifice, measured at docks and other manmade structures, and by acceleration along the hinge of an active anticline and at the footwall of an active fault. Based on this new data we suggest more precise time–space constraints for the dynamics of the lower eastern flank of Mt. Etna volcano.  相似文献   

8.
The February 1963 to January 1964 eruption of Gunung Agung, Indonesia’s largest and most devastating eruption of the twentieth century, was a multi-phase explosive and effusive event that produced both basaltic andesite tephra and andesite lava. A rather unusual eruption sequence with an early lava flow followed by two explosive phases, and the presence of two related but distinctly different magma types, is best explained by successive magma injections and mixing in the conduit or high level magma chamber. The 7.5-km-long blocky-surfaced andesite lava flow of ～0.1?km3 volume was emplaced in the first 26?days of activity beginning on 19 February. On 17 March 1963, a major moderate intensity (～4?×?107?kg?s?1) explosive phase occurred with an ～3.5-h-long climax. This phase produced an eruption column estimated to have reached heights of 19 to 26?km above sea level and deposited a scoria lapilli to fine ash fall unit up to ～0.2?km3 (dense rock equivalent—DRE) in volume, with Plinian dispersal characteristics, and small but devastating scoria-and-ash flow deposits. On 16 May, a second intense 4-h-long explosive phase (2.3?×?107?kg?s?1) occurred that produced an ～20-km-high eruption column and deposited up to ～0.1?km3 (DRE) volume of similar ash fall and pyroclastic flow deposits, the latter of which were more widespread than in the March phase. The two magma types, porphyritic basaltic andesite and andesite, are found as distinct juvenile scoria populations. This indicates magma mixing prior to the onset of the 1963 eruption, and successive injections of the more mafic magma may have modulated the pulsatory style of the eruption sequence. Even though a total of only ～0.4?km3 (DRE volume) of lava, scoria and ash fall, and scoria-and-ash pyroclastic flow deposits were produced by the 1963 eruption, there was considerable local damage caused mainly by a combination of pyroclastic flows and lahars that formed from the flow deposits in the saturated drainages around Agung. Minor explosive activity and lahar generation by rainfall persisted into early 1964. The climactic events of 17 March and 16 May 1963 managed to inject ash and sulfur-rich gases into the tropical stratosphere.  相似文献   

9.
From 1971 until 1995, the style of seismicity at Ruapehu changed little, reflecting a period of relatively low eruptive activity and consequent long-term stability within the vent system. Volcanic earthquakes and volcanic tremor were both dominated by a frequency of about 2 Hz. Volcanic earthquakes accompanied all phreatic and phreatomagmatic eruptions, but not small hydrothermal eruptions that originated within Crater Lake. Furthermore, more than half of the ML>3 volcanic earthquakes and changes in the reduced displacement of 2 Hz volcanic tremor by as much as a factor of 20 occurred without any accompanying eruptive activity. Three and 7 Hz volcanic tremor were also recorded, although never at lower-elevation seismometers. At times, this tremor was stronger at the summit seismometer than the 2 Hz tremor. Their source regions were independent of the 2 Hz source, and located at shallower depths. Volcano-tectonic earthquakes were generally unrelated to eruptive activity. The seismicity accompanying the 1995–1996 eruptive activity was significantly different from that of the period 1971 to 1995, and included volcanic tremor with a frequency of less than 1 Hz, simultaneous changes in the amplitude of the previously independent 2 Hz and 7 Hz volcanic tremor, and finally a change in the frequency content of volcanic earthquakes and volcanic tremor from 2 Hz to wideband. Path transmission effects play an important role in determining the characteristics of seismograms at Ruapehu. The presence of Crater Lake affects both the style of eruptions and the accompanying seismicity.  相似文献   

10.
Lastarria volcano (25°10′ S, 68°31′ W; 5,697 m above sea level), located in the Central Andes Volcanic Zone (northern Chile), is characterized by four distinct fumarolic fields with outlet temperatures ranging between 80°C and 408°C as measured between May 2006–March 2008 and April–June 2009. Fumarolic gasses contain significant concentrations of high temperature gas compounds (i.e., SO2, HCl, HF, H2, and CO), and isotopic ratios (3He/4He, δ13C–CO2, δ18O–H2O, and δD–H2O) diagnostic of magmatic gas sources. Gas equilibria systematics, in both the H2O-H2-CO2-CO-CH4 and alkane–alkene C3 system, suggest that Lastarria fumarolic gasses emanate from a superheated vapor that is later cooled and condensed at relatively shallow depths. This two-stage process inhibits the formation of a continuous aquifer (e.g., horizontal liquid layer) at relatively shallow depth. Recent developments in the magmatic gas system may have enhanced the transfer and release of heat causing shallow aquifer vaporization. The consequent pressure increase and aquifer vaporization likely triggered the inflation events beginning in 2003 at the Lastarria volcano.  相似文献   

11.
During volcanic explosions, volcanic ballistic projectiles (VBP) are frequently ejected. These projectiles represent a threat to people, infrastructure, vegetation, and aircraft due to their high temperatures and impact velocities. In order to protect people adequately, it is necessary to delimit the projectiles’ maximum range within well-defined explosion scenarios likely to occur in a particular volcano. In this study, a general methodology to delimit the hazard zones for VBP during volcanic eruptions is applied to Popocatépetl volcano. Three explosion scenarios with different intensities have been defined based on the past activity of the volcano and parameterized by considering the maximum kinetic energy associated with VBP ejected during previous eruptions. A ballistic model is used to reconstruct the “launching” kinetic energy of VBP observed in the field. In the case of Vulcanian eruptions, the most common type of activity at Popocatépetl, the ballistic model was used in concert with an eruptive model to correlate ballistic range with initial pressure and gas content, parameters that can be estimated by monitoring techniques. The results are validated with field data and video observations of different Vulcanian eruptions at Popocatépetl. For each scenario, the ballistic model is used to calculate the maximum range of VBP under optimum “launching” conditions: ballistic diameter, ejection angle, topography, and wind velocity. Our results are presented in the form of a VBP hazard map with topographic profiles that depict the likely maximum ranges of VBP under explosion scenarios defined specifically for Popocatépetl volcano. The hazard zones shown on the map allow the responsible authorities to plan the definition and mitigation of restricted areas during volcanic crises.  相似文献   

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13.
Observations of the summit eruption of Klyuchevskoi volcano in the period from February 15, 2007 to July 9, 2007 are considered. This typical (for this volcano) summit eruption was explosive-effusive in character. The ejectamenta volume is estimated at 0.025 km3. Calculation of active phases of the volcano was carried out in accordance with V.A. Shirokov’s technique. The identified active phases agree well with the eruptive periods. The 2007 summit eruption corresponds to an active phase (May 2006 to May 2009) favorable for the volcano’s eruption. Geodetic observations carried out since 1979 along a radial profile have revealed uplifts and subsidences of the northeastern slope of the volcano. The maximum displacement of 23 cm was recorded in 2007 on the site closest to the volcano crater at a distance of 11 km from the summit crater center. In the course of two previous summit eruptions (2003–2004 and 2005) insignificant uplifts and subsidences of the slope were also noted, although the general ascent of the slope remained. This indicated possible repeated eruptions in the nearest future. Changes in the seismicity before, during and after the eruption are also discussed.  相似文献   

14.
A major eruption produced several block-and-ash flows about 4,100 years B.P. at Citlaltépetl volcano (Pico de Orizaba), an ice-capped, 5670-m-high, andesitic, active stratovolcano located at the eastern end of the Mexican Volcanic Belt. Repetitive gravitational collapse of a dacitic dome at the summit crater produced a series of block-and-ash flows, lahars, and floods, which were channeled through two main river-valleys on the west and south flanks of the volcano. The total erupted volume is estimated to be at least 0.27 km3. The deposits in both areas are similar in composition, and size, but they differ in the area covered, distribution, and structure. The western deposits form a large fan, cover a larger area, and include numerous laharic and fluviatile deposits. In contrast, the southern deposits form prominent terraces where confined in narrow channels, and have associated laharic units in distal areas, where the flows reach a maximum distance of 30 km from the vent. Directed disruptions of a central summit dome occurred, possibly first to the west and then to the southeast, perhaps due to minor modifications of the summit dome morphology, producing the voluminous block-and-ash flow deposits documented here. The flows were strongly controlled by topography, influencing the deposition of the moving particles. Grain-size variations along the flow paths are hardly detectable suggesting no evident lateral downstream transformations. Because sudden changes in dome morphology may cause significant variations in the direction of future dome collapse, specific areas of potential affectation cannot be predicted. Therefore, about 350,000 inhabitants living within a radius of 35-km from the vent could be potentially impacted if catastrophic block-and-ash flows were to recur in the future from similar summit dome activity. Recognition of these deposits is therefore important for hazard assessment because some seemingly safe areas may be at high risk.  相似文献   

15.
The long-lived lava lake of Erta ’Ale volcano (Ethiopia) is remotely monitored by moderate resolution imaging spectroradiometers (MODIS) installed on satellites. The Normalised Thermal Index (NTI) (Wright et al. Remote Sens Environ 82:135–155 2002) is shown to be proportional to the volume of the lava lake based on visual observations. The lava lake’s variable level can be plausibly related to a stable foam, i.e. a mixture composed of densely packed non-coalescing bubbles in suspension within a liquid. This foam is trapped at the top of the magma reservoir, and its thickness changes in response to the gas flux feeding the foam being successively turned on and off. The temporal evolution of the foam thickness, and the resulting variation of the volume of the lava lake, is calculated numerically by assuming that the gas flux feeding the foam, initially constant and homogeneous since December 9, 2002, is suddenly stopped on December 13, 2002 and not restarted before May 2003. The best fit between the theoretical foam thickness and the level of the lava lake deduced from the NTI provides an estimate of both the reservoir radius, 155–170 m, and the gas flux feeding the foam, 5.5×10?3–7.2×10?3 m 3 s ?1 when existing. This is in agreement with previous estimates from acoustic measurements (Bouche et al. Earth Planet Sci Lett 295:37–48 2010). The very good agreement between the theoretical foam thickness and that deduced from MODIS data shows for the first time the existence of a regime based on the behaviour of a stable foam, whose spreading towards the conduit (“wide” conduit condition), can explain the long-lived activity. Our predictive model, which links the gas flux at the vent to the foam spreading, could potentially be used on any volcano with a long-lived activity. The underlying gas flux and the horizontal surface area of the magma reservoir can then be deduced by combining modelling to continuous measurements of gas flux. The lava lake, when high, often shows regular rise and fall of its level. We have recognised a minimum of 26 very well marked cycles between January 2001 and December 13, 2002, corresponding to a typical return time of 10.8 ± 2.3 days and a gas volume of 8.3×105 ± 2.0×105 m 3. This corresponds to a gas volume fraction in the reservoir equal to 0.023–0.063 %. The yearly gas flux, estimated between December 13, 2002 and September 27, 2004, varies between 2.3×10?6 and 5.9×10?6 m 3 s ?1 at the depth of the reservoir. The long-time series provided by infra-red sensors mounted on satellites could be used on any persistent volcano to detect potential periodic variations in the level of lava lakes or lava columns, providing that the vent has a funnel shape, as often, and is sufficiently large.  相似文献   

16.
The sequence of large Vulcanian explosions occurring at the andesitic Popocatépetl volcano, Mexico during November 1998 to April 1999 was studied. The size of 26 largest explosions was estimated from broadband seismic records at the distance of 4 km from the crater. The sequence began with the largest explosion (E = 2.6 × 1012 J) occurring on 25 November at 08:05, and following largest daily explosions were characterized by gradual decrease in the energy. The energy of 20 large (E ≥ 1011 J) explosions was distributed as Student's t-distribution with a geometrical mean Log E = 11.81 (J).  相似文献   

17.
The aim of this work is to propose a general model of Piton de la Fournaise volcano using information from geological and geophysical studies. Firstly, we make a graphical compilation of all available geophysical information along a W–E profile. Secondly, we construct a geological section that integrates both the geophysical information and the geological information. The lithosphere beneath Piton de la Fournaise is not significantly flexed, and the crust is underlain by an underplating body, which might represent the deep magma reservoir for La Réunion volcanism. Piton de la Fournaise is a relatively thin volcano lying on a huge volcanic construction attributed mostly to Les Alizés volcano. Indeed, if the differentiated rocks observed at the bottom of the Rivière des Remparts are the top of Les Alizés volcano, the interface with Piton de La Fournaise may be located at about sea level beneath the summit area. The endogenous constructions (intrusive complexes) related to Les Alizés and Piton de la Fournaise volcanoes represent a large volume. The huge intrusive complex of Les Alizés volcano probably rests on the top of the oceanic crust and appears to have a buttressing effect for the present eastern volcano-tectonic activity of Piton de la Fournaise. The early Piton de la Fournaise edifice was built around a focus located beneath the Plaine des Sables area. The center subsequently moved 5–6?km eastward to its current location. The dense, high-velocity body beneath the Plaines des Sables and the western part of the Enclos probably corresponds to the hypovolcanic intrusive complex that developed before the volcanic center shifted to its present-day position. Magma reservoirs may have existed, and may still exist, as illustrated by the March 1998 crisis, at the mechanical and density interface between the oceanic crust and the Les Alizés edifice. Strong evidence also exists for the presence of a shallower magma reservoir located near sea level beneath the summit. The March 1998 pre-eruptive seismic pattern (location and upward migration) seems to be evidence for a transfer of magma between the two reservoirs. The dominant structural feature of the central zone is a collapse structure beneath the summit craters, above the inferred magma reservoir near sea level. The collapsed column constitutes a major mechanical heterogeneity and concentrates most of the seismic, intrusive, and hydrothermal activity because of its higher permeability and weaker mechanical strength.  相似文献   

18.
The tephra fallout from the 12–15 August 1991 explosive eruption of Hudson volcano (Cordillera de los Andes, 45°54 S-72°58 W; Chile) was dispersed on a narrow, elongated ESE sector of Patagonia, covering an area (on land) of more than 100 000 km2. The elongated shape of the deposit, together with the relatively coarse mean and median values of the particles at a considerable distance from the vent, were the result of strong winds blowing to the southeast during the eruption. The thickness of the fall deposit decreases up to 250 km ESE from Hudson volcano, where it begins to thicken again. Secondary maxima are well developed at approximately 500 km from the vent. Secondary maxima, together with grainsize bimodality in individual layers and in the bulk deposit suggest that particle aggregation played an important role in tephra sedimentation. The fallout deposit is well stratified, with alternating fine-grained and coarsegrained layers, which is probably a result of strong eruptive pulses followed by relatively calm periods and/or changes in the eruptive style from plinian to phreatoplinian. The tephra is mostly composed of juvenile material: the coarse mode (mostly pumice) shifts to finer sizes with distance from the volcano; the fine mode (mostly glass shards) is always about 5/6 phi. Glass shards and pumice are mostly light gray to colorless. However, considerable amounts of dark, poorly vesiculated, blocky shards, suggest a hydromagmatic component in the eruption. A land-based tephra volume of 4.35 km3 was estimated, and a total volume of 7.6 km3 arose from an extrapolation, which took into account the probable volume sedimented in the sea. Bulk density ranges from 0.9 to 1.10 gr/cm3 (beyond 110 km from the vent). Rather uniform density values measured in crushed samples (2.45–2.50 gr/cm3 at all distances from the vent) reveal a relatively homogeneous composition. Mean and median sizes decrease rapidly up to 270 km from the vent; beyond that point they are more or less constant, whereas the maximum size (1 phi) shows a steady decrease up to 550 km. A concomitant improvement in sorting is observed. This is attributed to sorting due to wind transport combined with particle aggregation at different times and distances from the vent. The Hudson tephra fallout shares some strikingly similar features with the Mount St. Helens (18 May 1980) and Quizapu (1932) eruptions.  相似文献   

19.
Analysis of the historical records of Etnas eruptive activity for the past three centuries shows that, after the large 1669 eruption, a period of about 60 years of low-level activity followed. Starting from 1727, explosive activity (strombolian, lava fountaining and subplinian) at the summit crater increased exponentially to the present day. Since 1763, the frequency of flank eruptions also increased and this value remained high until 1960; afterward it further increased sharply. In fact, the number of summit and flank eruptions between 1961 and 2003 was four times greater than that of the pre-1960 period. This long-term trend of escalating activity rules out a pattern of cyclic behaviour of the volcano. We propose instead that the 1670–2003 period most likely characterises a single eruptive cycle which began after the large 1669 eruption and which is still continuing.On the basis of the eruptive style, two distinct types of flank eruptions are recognised: Class A and Class B. Class A eruptions are mostly effusive with associated weak strombolian activity; Class B eruptions are characterised by effusive activity accompanied by intense, long-lasting, strombolian and lava fountaining activity that produces copious tephra fallouts, as during the 2001 and 2002–2003 eruptions. Over the past three centuries, seven Class B eruptions have taken place with vents located mainly on the south-eastern flank, indicating that this sector of the volcano is a preferential zone for the intrusion of volatile-rich magma rising from the deeper region of the Etna plumbing system.Electronic Supplementary Material Supplementary material is available for this article at Editorial responsibility: M. Carroll  相似文献   

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