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1.
Mount Etna is an open conduit volcano, characterised by persistent activity, consisting of degassing and explosive phenomena at summit craters, frequent flank eruptions, and more rarely, eccentric eruptions. All eruption typologies can give rise to lava flows, which represent the greatest hazard by the volcano to the inhabited areas. Historical documents and scientific papers related to the 20th century effusive activity have been examined in detail, and volcanological parameters have been compiled in a database. The cumulative curve of emitted lava volume highlights the presence of two main eruptive periods: (a) the 1900–1971 interval, characterised by a moderate slope of the curve, amounting to 436 × 106 m3 of lava with average effusion rate of 0.2 m3/s and (b) the 1971–1999 period, in which a significant increase in eruption frequency is associated with a large issued lava volume (767 × 106 m3) and a higher effusion rate (0.8 m3/s). The collected data have been plotted to highlight different eruptive behaviour as a function of eruptive periods and summit vs. flank eruptions. The latter have been further subdivided into two categories: eruptions characterised by high effusion rates and short duration, and eruptions dominated by low effusion rate, long duration and larger volume of erupted lava. Circular zones around the summit area have been drawn for summit eruptions based on the maximum lava flow length; flank eruptions have been considered by taking into account the eruptive fracture elevation and combining them with lava flow lengths of 4 and 6 km. This work highlights that the greatest lava flow hazard at Etna is on the south and east sectors of the volcano. This should be properly considered in future land-use planning by local authorities.  相似文献   

2.
Potential Hazards of Eruptions around the Tianchi Caldera Lake, China   总被引：8，自引：0，他引：8  
Since the eruption of the Tianchi volcano about 1000 years ago, there have been at least 3 to 5 eruptions of small to moderate size. In addition, hazardous avalanches, rock falls and debris flows have occurred during periods between eruptions. A future eruption of the Tianchi volcano is likely to involve explosive interaction between magma and the caldera lake. The volume of erupted magma is almost in a range of 0.1-0.5 km3. Tephra fallout may damage agriculture in a large area near the volcano. If only 1% of the lake water were ejected during an eruption and then precipitated over an area of 200 km2, the average rainfall would be 100 mm. Moreover, lahars are likely to occur as both tephra and water ejected from the caldera lake fall onto flanks of the volcano. Rocks avalanching into the caldera lake also would bring about grave hazards because seiches would be triggered and lake water with the volume equal to that of the landslide would spill out of the existing breach in the caldera and cause flooding  相似文献   

3.
Errors in the interpretation of clouds, fumarolic activity and forest fires as volcanic eruptions in Tenerife, mainly in relation with Teide volcano, are common in references by passing navigators and other eyewitness accounts from the fifteenth and sixteenth centuries. In the case of the most common, historical, multiple‐vent fissure eruptions in the Canaries, vent locations provided by these accounts are frequently uncertain or are clearly erroneous and often conflict with geological evidence. Significant examples are the general association of the latest eruption of Teide volcano, dated at 1150 ± 140 bp , with the reference made by Christopher Columbus in 1492 to an eruption ‘on the flanks of Teide’, which actually corresponds to an eruptive vent (Boca Cangrejo volcano) situated in the NW Rift, dated at 400 ± 110 bp . Similar conflicting vent locations occurred in the 1730–36 eruption of Lanzarote and the 1677 eruption of La Palma. This article considers the volcanic cones located in the Orotava Valley, erroneously assigned by Chevalier de Borda and Alexander von Humboldt to a 1430 ad eruption. Geological evidence and radiocarbon dating of charcoal underlying the lapilli, and 40Ar/39Ar dating of one of the lava flows, show that these volcanic cones and lavas correspond to an eruption that took place about 30 000 yr bp . Analysis of the influence of these erroneous ages for the recent volcanism of Tenerife shows an overestimation of eruptive hazards of this island.  相似文献   

4.
Previous published data, combined with our results of 13 new radiocarbon ages and extensive geological fieldwork, indicate that during the past 11 ka 24 monogenetic basaltic eruptions occurred in the north sector of Gran Canaria. These eruptions can be grouped into three periods of eruptive activity: 1900–3200 14C a BP; 5700–6000 14C a BP; and an older period represented by only one eruption, El Draguillo, dated at 10 610 ± 190 14C a BP. Archaeological studies have shown that the more recent eruptions affected prehistoric human settlements on the island. Field studies demonstrate that the eruptions typically built strombolian cones (30–250 m in height) and associated relatively long lava flows (100–10 350 m in length); a few eruptions also produced tephra fall deposits. The total erupted volume of these eruptions is about 0.388 km3 (46.1% as tephra fall, 41.8% as cinder cone deposits and 12.1% as lava flows). The relatively low eruption rate (～0.04 km3 ka?1) during the past 11 ka is consistent with Gran Canaria's stage of evolution in the regional volcano‐tectonic setting of the Canary Archipelago. The results of our study were used to construct a volcanic hazards map that clearly delimits two sectors in the NE sector of Gran Canaria, where potential future eruptions would pose a substantial risk for densely populated areas. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

5.
The geological-geophysical data on the Pugachevo mud volcano group located in the zone of the submeridional Central Sakhalin Fault (CSF) are analyzed. The results of the density and geothermal modeling along two orthogonal profiles passing through the central part of the Pugachevo area are examined. It is found that the Late Cretaceous sequence of this fault-related area contains a subvertical narrow anomalous deconsolidation cone-shaped zone widening from 1 km on the surface to 4 km at its base (at the depths more than 6 km). The density of the deconsolidation blocks is 2.20–2.22 g/cm3, whereas that of the adjacent blocks reaches around 2.4–2.5 g/cm3. The largest deconsolidation block is located in the Lower Cretaceous Ai Formation, where a vast reservoir zone with mainly hydrocarbon gas (HC) is inferred at depths of more than 4400 m with temperatures of more than 140°C. The modeling results showed that the main reservoir of gases periodically ejected from the Pugachevo mud volcano is localized in the Ai Formation sequence in the tectonically weakened zone of the CSF at depths of 4.5–5.6 km. The overlying sequences contain smaller intermediate reservoirs. The Pugachevo area is promising for economic hydrocarbon reservoirs.  相似文献   

6.
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  
刘松雪  刘祥 《世界地质》2005,24(3):289-292
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   

7.
This paper reports detailed evidence on the dynamics of the gryphon activity of the Yuzhno-Sakhalinsk gas-water lithoclastic (mud) volcano. It was obtained by visual observations during periods between the short-term eruptions of 1959, 1979, and 2001 and, especially, during continuous monitoring between June 18 and September 3, 2005. In addition to the direct observations, the monitoring included measurements (three times per day) of the air temperature and pressure, the temperature of the liquid lithoclastic mass filling the crater hollows of several gryphons of various types, and the amounts of gases released by the two largest and most active gryphons. Liquid lithoclastic mass was collected daily in the crater of the largest (main or central) gryphon for the subsequent ICP AES analysis for five elements (Al, Fe, Ca, Mn, and Ba). The results of the monitoring were compared with the measurements of natural seismicity using the system of Dat and Datamark digital seismic stations. The acquired information was used to unequivocally demonstrate the existence of a direct causal relation between the activity of the Yuzhno-Sakhalinsk mud volcano, the dynamics of the chemical composition of the liquid lithoclastic mass ejected from its main gryphon, and the regional and local natural seismicity, which was previously conjectured. The dynamics of one of the measured elements (Al) is potentially useful for the prediction of eruptions.  相似文献   

8.
Levin  B. W.  Rybin  A. V.  Vasilenko  N. F.  Prytkov  A. S.  Chibisova  M. V.  Kogan  M. G.  Steblov  G. M.  Frolov  D. I. 《Doklady Earth Sciences》2010,435(1):1507-1510
In June 2009, one of the greatest eruptions of the Sarychev Peak volcano in Matua Island (48°06′ N, 153°12′ E) for the recent historical period occurred. With the help of satellite sounding methods, the first signs of volcanic activity were recorded and all the stages of the explosive eruption were traced. During the expeditionary investigations in the active volcano, unique data on the character of the eruption were obtained. The volume of erupted material was 0.4 cubic km, which lead to an increased area of Matua Island by 1.4 square km. The GPS observation station set at the distance of 7 km from the volcano recorded the rapid displacement of the Earths’s surface during the first two days of the active phase of eruption. This eruption of the Sarychev Peak volcano occurred 2.5 years after the catastrophic Simushir earthquakes in the period of intensive relaxation of stresses in the middle of the central part of the Kurile island arc.  相似文献   

9.
活火山是指1万年来有过喷发历史的全新世火山。火山的高分辨年代学对火山灾害评估和火山分类具有重要意义。对于缺乏历史记载的全新世火山,直接对火山岩进行同位素定年很困难。本文利用具有高时间分辨率的镭-钍-铀非平衡确定中国东部年轻火山的年龄。根据镭-钍-铀同位素,海南岛的马鞍岭和雷虎岭是全新世火山(马鞍岭:4.3ka;雷虎岭:4.7ka);镜泊湖火山(4.9ka)也是全新世火山;龙岗火山存在晚更新世和全新世活动(7.0ka,15.0ka);大兴安岭阿尔山和诺敏河Ra/Th非平衡消失但~(230)Th/~(238)U非平衡显著,属于晚更新世喷发(阿尔山:63ka;诺敏河:71ka)。海南岛的马鞍岭火山、雷虎岭火山和东北地区的龙岗火山、镜泊湖火山,是4座活火山。至于东北地区的阿尔山和诺敏河火山是否是活火山,有待测试更多样品的Ra/Th同位素。五大连池老黑山和火烧山有历史喷发记录,这与它们都存在显著Ra/Th非平衡一致。五大连池老黑山和火烧山的岩浆滞留年龄分别小于4.2ka和3.2ka,岩浆上升速率 18～23m/y。  相似文献   

10.
Recent field studies of postglacial volcanic deposits at Glacier Peak indicate the volcano has erupted more often, more voluminously, and more recently than previously thought. These past eruptions produced pyroclastic flows, extensive lahars, and widely distributed tephra falls. Analysis of the magnitude of past eruptions and the distribution of volcanic sediments indicates that future eruptions at Glacier Peak as large as those of the last several thousand years would dramatically affect people and property downstream and downwind from the volcano. Pyroclastic flows and lateral blasts would primarily affect uninhabited valleys within a few tens of kilometers of the volcano. Lahars and floods constitute the major hazard to populated areas from future eruptions, and could affect areas at low elevation along valley floors and in the Puget lowland as far as 100 km downvalley west of the volcano. Air-fall tephra from future eruptions will probably be deposited primarily east of Glacier Peak because of prevailing westerly winds.  相似文献   

11.
A detailed 90,000-year tephrostratigraphic framework of Aso Volcano, southwestern Japan, has been constructed to understand the post-caldera eruptive history of the volcano. Post-caldera central cones were initiated soon after the last caldera-forming pyroclastic-flow eruption (90 ka), and have produced voluminous tephra and lava flows. The tephrostratigraphic sequence preserved above the caldera-forming stage deposits reaches a total thickness of 100 m near the eastern caldera rim. The sequence is composed mainly of mafic scoria-fall and ash-fall deposits but 36 silicic pumice-fall deposits are very useful key beds for correlation of the stratigraphic sequence. Explosive, silicic pumice-fall deposits that fell far beyond the caldera have occurred at intervals of about 2500 years in the post-caldera activity. Three pumice-fall deposits could be correlated with lava flows or an edifice in the western part of the central cones, although the other silicic tephra beds were erupted at unknown vents, which are probably buried by the younger products from the present central cones. Most of silicic eruptions produced deposits smaller than 0.1 km3, but bulk volumes of two silicic eruptions producing the Nojiri pumice (84 ka) and Kusasenrigahama pumice (Kpfa; 30 ka) were on the order of 1 km3 (VEI 5). The largest pyroclastic eruption occurred at the Kusasenrigahama crater about 30 ka. This catastrophic eruption began with a dacitic lava flow and thereafter produced Kpfa (2.2 km3). Total tephra volume in the past 90,000 years is estimated at about 18.1 km3 (dense rock equivalent: DRE), whereas total volume for edifices of the post-caldera central cones is calculated at about 112 km3, which is six times greater than the former. Therefore, the average magma discharge rate during the post-caldera stage of Aso Volcano is estimated at about 1.5 km3/ky, which is similar to the rates of other Quaternary volcanoes in Japan.  相似文献   

12.
This retrospective study focuses on the fine silicate particles (<62 µm in diameter) produced in a large eruption that was otherwise well studied. Fine particles represent a potential hazard to aircraft, because as simple particles they have very low terminal velocities and could potentially stay aloft for weeks. New data were collected to describe the fine particle size distributions of distal fallout samples collected soon after eruption. Although, about half of the mass of silicate particles produced in this eruption of ~1 km3 dense rock equivalent magma were finer than 62 µm in diameter, and although these particles were in a stratospheric cloud after eruption, almost all of these fine particles fell to the ground near (<300 km) the volcano in a day or two. Particles falling out from 70 to 300 km from the volcano are mostly <62 µm in diameter. The most plausible explanation for rapid fallout is that the fine ash nucleates ice in the convective cloud and initiates a process of meteorological precipitation that efficiently removes fine silicates. These observations are similar to other eruptions and we conclude that ice formation in convective volcanic clouds is part of an effective fine ash removal process that affects all or most volcanic clouds. The existence of pyroclastic flows and surges in the El Chichón eruption increased the overall proportion of fine silicates, probably by milling larger glassy pyroclasts.  相似文献   

13.
Cerro Machín is a dacitic tuff ring located in the central part of the Colombian Andes. It lies at the southern end of the Cerro Bravo–Cerro Machín volcanic belt. This volcano has experienced at least six major explosive eruptions during the last 5000 years. These eruptions have generated pyroclastic flows associated with Plinian activity that have traveled up to 8 km from the crater, and pyroclastic flows associated with Vulcanian activity with shorter runouts of 5 km from the source. Today, some 21,000 people live within a 8 km radius of Cerro Machín. The volcano is active with fumaroles and has shown increasing seismic activity since 2004, and therefore represents a potentially increasing threat to the local population. To evaluate the possible effects of future eruptions that may generate pyroclastic density currents controlled by granular flow dynamics we performed flow simulations with the TITAN2D code. These simulations were run in all directions around the volcano, using the input parameters of the largest eruption reported. The results show that an eruption of 0.3 km3 of pyroclastic flows from a collapsing Plinian column would travel up to 9 km from the vent, emplacing a deposit thicker than 60 m within the Toche River valley. Deposits >45 m thick can be expected in the valleys of San Juan, Santa Marta, and Azufral creeks, while 30 m thick deposits could accumulate within the drainages of the Tochecito, Bermellón, and Coello Rivers. A minimum area of 56 km2 could be affected directly by this kind of eruption. In comparison, Vulcanian column-collapse pyroclastic flows of 0.1 km3 would travel up to 6 km from the vent depositing >45 m thick debris inside the Toche River valley and more than 30 m inside the valleys of San Juan, Santa Marta, and Azufral creeks. The minimum area that could be affected directly by this kind of eruption is 33 km2. The distribution and thickness of the deposits obtained by these simulations are consistent with the hazard map presented by INGEOMINAS (Geological Survey of Colombia) in 2002. The composite map of the simulated flow deposits suggests that after major explosive events such as these, the generation of lahars is probable.  相似文献   

14.
Nyamulagira (3058 m a.s.l.), a volcano of the Virunga volcanic province in the western branch of the East African Rift, is Africa’s most active volcano with one eruption every 2–4 years. It represents a hazard for the Virunga National Park and its vicinity. Despite such a frequent activity, Nyamulagira remains poorly studied. The only existing volcanological map was produced in the sixties by Thonnard et al. (1965). The occurrence of 19 eruptions since its publication makes it obsolete. In the present study we mapped the Nyamulagira lava flows from 1938 up to the last eruption to date in 2010 using optical (Landsat, ASTER) and radar (ENVISAT-ASAR, ERS, JERS) imagery. The results are integrated into a Geographical Information System (GIS) and coupled with additional data sources. GIS use makes the new database a flexible – and easy-to-update – tool for scientific purposes as well as for risk, environmental and humanitarian management. Here a new lava flow map was produced. Volumes of the successive lava flows and affected areas of the Virunga National Park were estimated.  相似文献   

15.
Volcanic hazards from Pico de Orizaba volcano are presented here tor the first time. Some 1.3 million people live within the hazard zone, which in the most severe case would encompass the Mexican Gulf coast, east of the volcano. Three major cities located in the eastern part of the hazard zone account for 800 000 of this population and about 200 000 people live within a 20 km radius of the volcano. Probability calculations are presented as an attempt to quantify the hazards in the surroundings of the volcano. Such quantification can be of use in planning for future land use within the hazard zones.A zone of about 10 km radius centred on the top crater is a high hazard zone for gravity-driven flows and fallout ejecta. For large volume eruptions, the radius could be extended to 120 km to the east and 60 km to the west. The asymmetrical distribution is related to the topography of the volcano. Hazards from Pyroclastic-fall deposits are principally to the west of the volcano, since easterly winds are dominant in the area lava-flow hazards are greatest within a 10 km radius from the summit crater. Pyroclastic flow hazards are high up to 20 km from the volcano summit.In the case of reactivation of the volcano, melting of a glacier covering the summit of Pico de Orizaba having a volume equivalent to some 45 × 109 litres of water, would produce lahars which would descend the flanks of the volcano.  相似文献   

16.
The total area of debris flow territories of the Russian Federation accounts for about 10% of the area of the country. The highest debris flow activity areas located in Kamchatka-Kuril, North Caucasus and Baikal debris flow provinces. The largest debris flow events connected with volcano eruptions. Maximum volume of debris flow deposits per one event reached 500 × 106 m3 (lahar formed during the eruption of Bezymyanny volcano in Kamchatka in 1956). In the mountains of the Greater Caucasus, the maximum volume of transported debris material reached 3 × 106 m3; the largest debris flows here had glacial reasons. In the Baikal debris flow province, the highest debris flow activity located in the ridges of the Baikal rift zone (the East Sayan Mountains, the Khamar-Daban Ridge and the ridges of the Stanovoye Highland). Spatial features of debris flow processes within the territory of Russia are analyzed, and the map of Debris Flow Hazard in Russia is presented. We classified the debris flow hazard areas into 2 zones, 6 regions and 15 provinces. Warm and cold zones are distinguished. The warm zone covers mountainous areas within the southern part of Russia with temperate climate; rain-induced debris flows are predominant there. The cold zone includes mountainous areas with subarctic and arctic climate; they are characterized by a short warm period, the occurrence of permafrost, as well as the predominance of slush flows. Debris flow events are described for each province. We collected a list of remarkable debris flow events with some parameters of their magnitude and impact. Due to climate change, the characteristics of debris flows will change in the future. Availability of maps and information from previous events will allow to analyze the new cases of debris flows.  相似文献   

17.
全球主要火山灾害及其分布特征   总被引：1，自引：0，他引：1  
本文研究了火山灾害各种致灾因子的物理过程和灾害特点,根据文献中记载的全球火山灾害,在进行火山灾害分区研究的基础上,研究了全球火山灾害分布特征.全球主要的火山灾害分布在8个主要区域.有记载的火山灾害在热带占73%,远高于火山喷发分布于热带区的比例.全球两个最强烈的火山灾害分布区都是围绕着位于板块结合部表现为复杂构造结的班达海和加勒比海,而且每一个灾害区都有3条分支.热带区第3个灾害区为中非区,地幔上隆是这里主要的动力学背景.本文还研究了1700年以来火山灾害时间分布特征,以及1993年以来各种火山灾害发生频次.  相似文献   

18.
Merapi is Indonesia's most dangerous volcano with a history of deadly eruptions. Over the past two centuries, the volcanic activity has been dominated by prolonged periods of lava dome growth and intermittent gravitational or explosive dome failures to produce pyroclastic flows every few years. Explosive eruptions, such as in 2010, have occurred occasionally during this period, but were more common in pre‐historical time, during which a collapse of the western sector of the volcano occurred at least once. Variations in magma supply from depth, magma ascent rates and the degassing behaviour during ascent are thought to be important factors that control whether Merapi erupts effusively or explosively. A combination of sub‐surface processes operating at relatively shallow depth inside the volcano, including complex conduit processes and the release of carbon dioxide into the magmatic system through assimilation of carbonate crustal rocks, may result in unpredictable explosive behaviour during periods of dome growth. Pyroclastic flows generated by gravitational or explosive lava dome collapses and subsequent lahars remain the most likely immediate hazards near the volcano, although the possibility of more violent eruptions that affect areas farther away from the volcano cannot be fully discounted. In order to improve hazard assessment during future volcanic crises at Merapi, we consider it crucial to improve our understanding of the processes operating in the volcano's plumbing system and their surface manifestations, to generate accurate hazard zonation maps that make use of numerical mass flow models on a realistic digital terrain model, and to utilize probabilistic information on eruption recurrence and inundation areas.  相似文献   

19.
内蒙锡林浩特鸽子山火山地质研究   总被引：4，自引：3，他引：1  
鸽子山火山位于内蒙古自治区锡林浩特市东南,处于大兴安岭-大同新生代火山喷发带中段,是锡林浩特-阿巴嘎火山群中保存最为完好的一座玄武质火山。火山喷发物的分布面积约55km2,主要为降落火山渣、溅落熔结火山碎屑岩和熔岩流,成分主要为碧玄岩,晚期有少量的橄榄拉斑玄武岩,碧玄岩中含有较多二辉橄榄岩包体和辉石及歪长石巨晶。火山由锥体、熔岩流和火山碎屑席组成,锥体由早期的降落锥和晚期溅落锥复合而成。火山口经历多次塌陷而成为破火口。锥体西侧及北东侧出露两个仍保留了原始形态的熔岩溢出口,熔岩流类型为结壳熔岩,由多个岩流单元组成,局部地区的熔岩流中发育较多保存完好的喷气锥、喷气碟或喷气塔。火山碎屑席主要分布在锥体的东侧,厚度由锥体向外逐渐减薄。火山活动可分为早、晚两个阶段,早期为爆破式喷发,形成火山渣锥和碎屑席,属亚布里尼型喷发,晚期主要为溢流式喷发,形成溅落锥和大规模熔岩流,其活动时代为晚更新世末-全新世。  相似文献   

20.
云南腾冲大六冲火山机构的发现及意义   总被引：1，自引：0，他引：1  
腾冲火山群位于我国云南省西部和缅甸交界处的腾冲县境内,是我国著名的第四纪火山群,既有黑空山、打鹰山、马鞍山等一系列晚第四纪新期火山,也有早更新世以来有过喷发活动的大六冲、余家大山、来凤山等老火山。其中,位于腾冲火山区中东部的大六冲山势高峻,其顶峰是本区内的最高峰。野外地质调查发现,大六冲山体由一系列巨厚层爆发相火山碎屑堆积物和少量溢流相熔岩类岩石构成,喷发物类型极其丰富。在大六冲最高峰以南约100m处,首次发现存在着一个直径超百米的火山通道,可能是区内早期火山喷发的主通道,火山颈、熔岩穹丘、岩墙、爆发相与溢出相堆积物构成了大六冲完整的火山机构,在其周边多处地方还发现了因山体岩石破碎后形成的垮塌和滑坡堆积物。大六冲火山机构及其滑塌物的发现,不仅可以解释腾冲火山区大范围分布的火山碎屑岩的来源,也为防治以后类似大规模喷发可能造成的次生地质灾害提供了理想的研究样本和未来灾害预警。  相似文献   

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