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1.
This paper documents a phreatomagmatic flank eruption that occurred 18 700 ± 100 a BP , on the lower north-eastern slope of Etna during the Ellittico volcano activity, which produced fall and surge deposits. This type of eruption is connected to a sedimentary basement ridge at Etna. The interaction between the rising magma and the shallow groundwater hosted in the volcanic pile overlying the impermeable sediments resulted in phreatomagmatic instead of strombolian activity. Three eruptive phases are distinguished based on field and analytical data: (i) an explosive phreatomagmatic opening, (ii) a main phase producing coarse lithic-rich fallout and a strombolian deposit, and (iii) the final pulsating surge-forming phase. The discovery of this phreatomagmatic flank eruption, which occurred at lower altitude, raises important issues for previous hazard assessments at Etna.  相似文献   

2.
An anomalous behaviour of the scaling exponent derived from the detrended fluctuation analysis (DFA) of the time series of low frequency variations of the horizontal and vertical magnetic field components has been recently reported as being observed 2 months prior to the Mw 6.3 earthquake on 6 April 2009, close to L’Aquila city, Italy. Here, we suggest a possible physical explanation of this effect based on the experience from similar measurements in Greece. In particular, for example, we compare these observations associated with Aquila earthquake with the ones of the Mw 6.6 earthquake on 13 May 1995 at Kozani-Grevena, Greece where both magnetic field variations and seismic electric signals (SES) were recorded. Almost 1 month before the latter earthquake, anomalous variations in both electric and magnetic field were detected, the time series of that were analysed by means of DFA and led to an exponent close to unity. Similarly, the calculated DFA exponent for the Aquila earthquake time series of the anomalous magnetic field variations 2 months before the main shock was also found close to unity. These results could imply that in the case of Aquila, according to the Maxwell’s laws, one should expect to observe simultaneously with the magnetic signal an associated SES activity, provided that an appropriate station to monitoring the earth’s electric field variations in the same area was available. Hence, it seems that similar underlying non-linear dynamic processes in mechanical and as well as electromagnetic sense, with features of criticality, dominated in both pre-focal areas.  相似文献   

3.
Indoor Radon concentrations have been carried out simultaneously at the villages of S. Venerina and Acireale, which are located on the south-eastern flank of Mt. Etna volcano. Both investigation sites are partially affected by the same fault system, which plays an important role in the dynamics of the volcano, especially before and during eruptive periods. Measurements were performed in the period from January 2006 until April 2006, just prior to an eruption which took place on 14th July 2006. Indoor Radon monitoring at S. Venerina, was carried out at two buildings located nearby, characterized by a different type of construction. These buildings were chosen because they can be considered as representative of both the historical centre and the new neighbourhoods of the village. At the same time, a Radon active monitor was operating in-soil near the two aforesaid edifices. Cross-correlation analysis between the in-soil one with both the indoor S. Venerina Radon series indicated different temporal correlation, probably due to the different types of building foundations and constructive materials of their walls, both causing the different indoor accumulation. S. Venerina’s indoor Radon values taken at the new building showed similar trends and the same anomalies as the ones recorded at Acireale. The simultaneous increase in indoor Radon concentration was observed at both sites from the last ten days of March, when a significant increase in the CO2 efflux was recorded. Increases in volcanogenic gases occurred very probably throughout an inflating state of the volcano during the pre-eruptive period, which caused the wide opening of the fractures. Lastly, variations in indoor Radon concentrations observed before an eruption, indicate the suitability of the investigated sites for in-soil Radon monitoring at a low altitude of the south-eastern flank of Mt. Etna. Moreover, in this place repeated and long period Radon indoor measurements should be carried out due to high potential indoor accumulation which depends from the volcanic activity, as this could constitute a serious danger to public health.  相似文献   

4.
Techniques capable of measuring lava discharge rates during an eruption are important for hazard prediction, warning, and mitigation. To this end, we developed an automated system that uses thermal infrared satellite MODIS data to estimate time-averaged discharge rate. MODIS-derived time-varying discharge rates were used to drive lava flow simulations calculated using the MAGFLOW cellular automata model, allowing us to simulate the discharge rate-dependent spread of lava as a function of time. During the July 2006 eruption of Mount Etna (Sicily, Italy), discharge rates were estimated at regular intervals (i.e., up to 2 times/day) using the MODIS data. The eruption lasted 10 days and produced a ~3-km-long lava flow field. Time-averaged discharge rates extracted from 13 MODIS images were utilized to produce a detailed chronology of lava flow emplacement, demonstrating how infrared satellite data can be used to drive numerical simulations of lava flow paths during an ongoing eruptive event. The good agreement between simulated and mapped flow areas indicates that model-based inundation predictions, driven by time-varying discharge rate data, provide an excellent means for assessing the hazard posed by ongoing effusive eruptions.  相似文献   

5.
The 1928 eruption of Etna, Sicily, although the largest such event this century, has not been studied in detail. In this paper the nature of the eruption, the destruction it caused – including the complete devastation of the town of Mascali (pre-eruption population 2,000) – and emergency responses of the authorities to it are reviewed in the context of fascist politics and planning priorities. It is contended that, although at one level the response to the 1928 eruption was successful, at another fascism merely continued and enhanced a reactive, propitiatory approach to hazard mitigation. We argue that this legacy was not successfully overcome until the middle of the nineteen eighties. Finally contemporary Italian moves towards a more proactive approach to disaster planning, both generally and in the context of Etna, are discussed.  相似文献   

6.
During emplacement, lavas modify the pre‐existing topography and release a large amount of heat. In spite of the relevance of both heat and mass release, combined morphological and thermal analyses have been seldom carried out at a flow‐field scale. Here, we consider a channelised lava flow unit formed at Mt Etna during the 2001 flank eruption, and we show that, by combining a morphological analysis of the pre‐ and post‐emplacement topography with the analysis of the syn‐eruptive thermal signature, critical insights about the processes driving mass and heat dissipation can be derived. Our results suggest that, in the considered lava flow, the pre‐emplacement slope controls heat dissipation and can influence the thickness of the final lava deposit, with possible implications for hazard assessment. The width of the lava channel, instead, appears less sensitive to the pre‐emplacement slope, and tends to regularly increase with increasing distance from the vent.  相似文献   

7.
The pyroclastic deposits of Etna have been correlated over the whole volcanic edifice for the first time, allowing the construction of a continuous record of tephra-producing events, which extends from approximately 100 ka to the Present. In this interval, five main periods of explosive activity have been identified: (a) ~100-ka strombolian to subplinian activity; (b) 80- to 100-ka plinian benmoreitic activity; (c) 16- to 80-ka strombolian to subplinian from basaltic to mugearitic activity; (d) 15.5- to 15-ka plinian benmoreitic activity accompanying the caldera-forming eruptions of the Ellittico Volcano; and (e) the most recent 13-ka basaltic explosive activity of strombolian and subplinian type of the present edifice that also includes the 122-B.C. plinian eruption. This study results in a semi-quantitative and in some cases quantitative definition of the intensity and chronology of the explosive activity at Etna. Moreover, this work gives a new significance to the volcanic hazards of Etna, a volcano generally considered to be the site of gentle effusive eruptions.  相似文献   

8.
Here we present a tephrostratigraphic record (core Co1202) recovered from the northeastern part of Lake Ohrid (Republics of Macedonia and Albania) reaching back to Marine Isotope Stage (MIS) 6. Overall ten horizons (OT0702‐1 to OT0702‐10) containing volcanic tephra have been recognised throughout the 14.94 m long sediment succession. Four tephra layers were visible at macroscopic inspection (OT0702‐4, OT0702‐6, OT0702‐8 and OT0702‐9), while the remaining six are cryptotephras (OT0702‐1, OT0702‐2, OT0702‐3, OT0702‐5, OT0702‐7 and OT0702‐10) identified from peaks in K, Zr and Sr intensities, magnetic susceptibility measurements, and washing and sieving of the sediments. Glass shards of tephra layers and cryptotephras were analysed with respect to their major element composition, and correlated to explosive eruptions of Italian volcanoes. The stratigraphy and the major element composition of tephra layers and cryptotephras allowed the correlation of OT0702‐1 to AD 472 or AD 512 eruptions of Somma‐Vesuvius, OT0702‐2 to the FL eruption of Mount Etna, OT0702‐3 to the Mercato from Somma‐Vesuvius, OT0702‐4 to SMP1‐e/Y‐3 eruption from the Campi Flegrei caldera, OT0702‐5 to the Codola eruption (Somma‐Vesuvius or Campi Flegrei), OT0702‐6 to the Campanian Ignimbrite/Y‐5 from the Campi Flegrei caldera, OT0702‐7 to the Green Tuff/Y‐6 eruption from Pantelleria Island, OT0702‐8 to the X‐5 eruption probably originating from the Campi Flegrei caldera, OT0702‐9 to the X‐6 eruption of generic Campanian origin, and OT0702‐10 to the P‐11 eruption from Pantelleria Island. The fairly well‐known ages of these tephra layers and parent eruptions provide new data on the dispersal and deposition of these tephras and, furthermore, allow the establishment of a chronological framework for core Co1202 for a first interpretation of major sedimentological changes. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

9.
3D earthquake locations, focal mechanisms and stress tensor distribution in a 16‐month interval covering the 2018 Mt. Etna flank eruption, enabled us to investigate the relationship between magma intrusion and structural response of the volcano and shed light on the dynamic processes affecting the instability of Mt. Etna. The magma intrusion likely caused tension in the flanks of the volcano, leading to significant ground deformation and redistribution of stress on the neighbouring faults at the edge of Mt. Etna's unstable sector, encouraging the ESE sliding of the eastern flank of the volcano. Accordingly, FPSs of the post‐eruptive events show strike slip faulting mechanisms, under a stress regime characterized by a maximum compressive σ1, NE‐SW oriented. In this perspective, any flank eruption could temporarily enhance the sliding process of both the southern and eastern flanks of the volcano.  相似文献   

10.
The Pb isotopic compositions of phenocrystic phases in young basaltic lavas have been investigated using the Getty-DePaolo method (Getty S. J. and DePaolo D. J. [1995] Quaternary geochronology by the U-Th-Pb method. Geochim. Cosmochim. Acta59, 3267-3272), which allows for the resolution of small isotopic differences. Phenocryst, matrix, and whole rock analyses were made on samples from the 17 Myr-old Imnaha basalts of the Columbia River Group, a zero-age MORB from the Mid-Atlantic Ridge, and a ca. 260 kyr-old tholeiite from Mount Etna. Plagioclase feldspar phenocrysts have low-(U, Th)/Pb, and in each sample the plagioclase has significantly lower 206Pb/207Pb and 208Pb/207Pb values than whole rock, matrix, and magnetite-rich separates. The Pb isotopic contrast between plagioclase and matrix/whole rock is found in three samples with varying grain sizes (0.5-2 cm for the Imnaha basalt and MORB and <1 mm for the Etna sample) from different tectonic settings, suggesting that these results are not unique. The isotopic contrasts are only slightly smaller in magnitude than the variations exhibited by whole rock samples from the region. The Imnaha basalts also have Sr isotopic heterogeneity evident only in plagioclase phenocrysts, but the MORB and Etna lavas do not. The isotopic heterogeneities reflect magma mixing, and indicate that isotopically diverse magmas were mixed together just prior to eruption. The results reinforce indications from melt inclusion studies that magma source region isotopic heterogeneities have large amplitudes at short length scales, and that the isotopic variations imparted to the magmas are not entirely homogenized during segregation and transport processes.  相似文献   

11.
Continuous GPS (CGPS) data, collected at Mt. Etna between April 2012 and October 2013, clearly define inflation/deflation processes typically observed before/after an eruption onset. During the inflationary process from May to October 2013, a particular deformation pattern localised in the upper North Eastern sector of the volcano suggests that a magma intrusion had occurred a few km away from the axis of the summit craters, beneath the NE Rift system. This is the first time that this pattern has been recorded by CGPS data at Mt. Etna. We believe that this inflation process might have taken place periodically at Mt. Etna and might be associated with the intrusion of batches of magma that are separate from the main feeding system. We provide a model to explain this unusual behaviour and the eruptive regime of this rift zone, which is characterised by long periods of quiescence followed by often dangerous eruptions in which vents can open at low elevation and thus threaten the villages in this sector of the volcano.  相似文献   

12.
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13.
Published and new data on the Earth’s past magnetic field have been interpreted in terms of its links with the frequency of magnetic polarity reversals and with tectonic events such as plume-related eruptions and rifting. The paleointensity and reversal frequency variations show an antiphase correlation between 0 and 160 Ma, and the same tendency likely holds for the past 400 Myr. The geomagnetic field intensity averaged over geological ages (stages) appears to evolve in a linearly increasing trend while its variations increase proportionally in amplitude and change in structure. Both paleointensity and reversal frequency patterns correlate with rifting and eruption events. In periods of high rifting activity, the geomagnetic field increases (15 to 30%) and the reversals become about 40% less frequent. Large eruption events between 0 and 150 Ma have been preceded by notable changes in magnetic intensity which decreases and then increases, the lead being most often within a few million years.  相似文献   

14.
广西北海涠洲岛是我国最大的第四纪火山岩海岛。近些年来随着我国核电事业的不断发展,涠洲岛火山最后喷发时代和对区域核电厂址的潜在火山灾害,受到了国内外地学界和核电工业界的广泛关注。我们通过对涠洲岛南部地区射汽岩浆喷发的基浪堆积物的野外地质地貌考察,研究了火山喷发物的岩性特征、沉积结构和堆积规模。同时,对系统采集于不同堆积部位的喷发物样品和上覆的黄土样品进行了电子自旋共振(ESR)年代测试分析,结合前人光释光(OSL)测年结果,得出涠洲岛火山最后一次喷发的时间为晚更新世晚期至全新世早期,距今约13～33ka。  相似文献   

15.
A model for the nonradial motion of an eruptive prominence in the solar corona is proposed. Such motions, which can sometimes be inaccessible to observation, result in an apparent break in the causal link between eruptive prominences and coronal mass ejections. The global magnetic field of the Sun governs coronal plasma motions. The complex structure of this field can form prominence trajectories that differ considerably from a simple vertical rise (i.e., radial motion). A solar filament is modeled as a current-carrying ring or twisted toroidal magnetic rope in equilibrium with the coronal magnetic field. The global field is described using two spherical harmonics. A catastrophic violation of the filament equilibrium followed by its rapid acceleration—eruption—is possible in this nonlinear system. The numerical solution of the equations of motion corresponds well to the eruption pattern observed on December 14, 1997.  相似文献   

16.
 The aim of this paper is to verify whether lichens have the capacity to accumulate atmospheric contaminators linked to volcanic activity. About 100 lichens were collected in 1994 and 1995 from two active volcanic areas in Italy: Mount Etna and Vulcano Island. Twenty-seven elements were analyzed for each individual lichen using Instrumental Neutronic Activation Analysis and Inductively Coupled Plasma-Mass Spectrometry. Lichen composition reflects the contribution of the volcanic particulate material, and the two areas investigated can be distinguished on the basis of the concentration of some lithophile elements. Moreover, the distribution in lichens of the elements (As, Sb, Br, Pb) – derived from gas emissions (plume, fumaroles) – also shows different geochemical trends on Mt. Etna and Vulcano. Received: 20 April 1998 · Accepted: 4 July 1998  相似文献   

17.
利用InSAR技术研究黄土地区滑坡分布   总被引：1，自引：0，他引：1  
InSAR技术能够获取大面积、连续、高精度的地表垂直形变信息,可用来监测地震、火山、滑坡等自然灾害造成的地表形变。文章介绍了InSAR技术在监测陕北黄土地区滑坡中的应用,首先进行野外地质勘察和TM光学遥感影像解译,接着通过EnviSat SAR数据差分干涉处理,获取研究区干涉形变场,提取出滑坡位移量,最后详细分析黄草湾至董家寺沿线一带的滑坡变形范围,并划定出了4个有一定变形的重点监视区。  相似文献   

18.
On December 24th, Mt. Etna volcano underwent a seismic crisis beneath the summit and upper southern flank of the volcano, accompanied by significant ash emission. Eruptive fissures opened at the base of summit craters, propagating SE‐wards. This lateral eruption lasted until December 27th. Despite the small eruption, seismic swarm and ground deformation were very strong. Sentinel‐1 interferograms show a wide and intense ground deformation with some additional features related to volcano‐tectonic structures. We inverted DInSAR data to characterise the magma intrusion. The resulting model indicates that a large dyke intruded but aborted its upraise at about the sea level; however, this big intrusion stretched the edifice, promoting the opening of the eruptive fissures fed by a shallower small dyke, and activating also several faults. This model highlights that a big intrusion beneath a structurally complex volcano represents a main issue even if the eruption is aborted.  相似文献   

19.
The size distributions of crystals of olivine, plagioclase and oxides of the 1991/93 eruption at Mt. Etna (Italy) are analyzed. The simultaneous collection of this information for different minerals gives precious insight into the cooling history of lavas. Three distinct episodes are detectable: a storage of the magma in a deep reservoir, characterized by nearly constant and low nucleation and growth rates (near to equilibrium); an ascent phase, with an ever increasing nucleation rate related to volatile exsolution; and finally a quenching phase. In addition to geochemical and geophysical evidence, the similarity of the crystal size distributions of the present eruption with those of previous ones of this century makes it possible to exclude that crystal size distributions of Etnean lavas are due to mixing of different populations. This strongly suggests that the main features of the volcano feeding system have not changed despite observed variations in the magma output rates.  相似文献   

20.
Spivak  A. A.  Riabova  S. A. 《Doklady Earth Sciences》2020,493(1):526-529
Doklady Earth Sciences - The response of the Earth’s magnetic field and electrical parameters of the atmosphere to the eruption of Stromboli (July 3, 2019, Italy) is studied using the results...  相似文献   

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