共查询到18条相似文献，搜索用时 953 毫秒
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用分形理论分析了吉林龙岗火山碎屑物粒度的分形结构特征。结果显示,射气喷发碎屑物分维值>射气岩浆喷发碎屑物分维值>岩浆喷发碎屑物分维值,分维值可作为区分火山不同喷发类型的定量参数。而对于龙岗岩浆喷发碎屑物,不同火山喷发的碎屑物其分维值也有差别,晚期喷发的金龙顶子火山碎屑分维值>2,早期喷发的小金龙顶子碎屑分维值>2,火山碎屑物分维值可作为区分不同喷发源和划分火山喷发地层序列的一种指标。研究表明,分维值<2的火山碎屑中有不同含量的非等轴颗粒,且分维值与非等轴颗粒的含量呈负相关 相似文献
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锡林浩特-阿巴嘎火山群内的玛珥式火山 总被引：4，自引：0，他引：4
锡林浩特-阿巴嘎火山群位于内蒙古自治区锡林郭勒盟,处于大兴安岭-大同新生代火山喷发带中段。火山群内发育300余座不同类型的第四纪玄武质火山,其中玛珥式火山属首次发现,以阿巴嘎旗东南部的浩特乌拉、西北部的车勒乌拉和额斯格乌拉玛珥式火山最具代表性,其火山规模较大,锥体直径一般为3～4km,大者约6.5km。火山结构较完整,具有相似的双轮山地貌景观和明显的阶段性喷发过程,喷发阶段早期为强烈的射汽-岩浆爆发,晚期均转变为弱岩浆爆发,最后为玄武质熔岩流的溢出。这种喷发序列反映了岩浆与水相互作用以及岩浆上升速度和溢出率变化的过程。火山喷发形成的基浪堆积物覆盖在中更新统河谷砂砾石之上,其中近火口溅落堆积物中上新世砂泥岩"包体"的热释光年龄为(0.112±0.0096)Ma,表明玛珥式火山喷发时代属晚更新世早期。 相似文献
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高温岩浆在上升过程中遇到地下水或地表水发生水岩相互作用,产生大量水蒸汽导致的爆炸式喷发作用,可称为射汽岩浆喷发作用,是一种较为特殊的火山活动,主要产物为低平火山口和基浪堆积物。国内外许多火山学家对射汽岩浆喷发作用的喷发过程和产物开展了岩相学、沉积学、火山物理学和地球化学综合研究,通过实验、计算机模拟等方法探究了射汽岩浆喷发过程的影响因素。文中介绍了国内外研究人员的相关研究成果,以便更好地了解射汽岩浆喷发这种特殊的火山作用形式,以期能将其应用于现代火山灾害预防和监测工作中,保护人们的生命和财产安全。 相似文献
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琼北地区北西方向长流-仙沟断裂带晚第四纪活动及与火山活动关系的讨论 总被引：2，自引：0，他引：2
琼北地区的火山活动以裂隙喷溢为主,晚更新世道堂期的射气岩浆喷发形成了众多的低平火山口,全新世雷虎岭期火山口主要分布于石山、永兴一带,沿NW向长流-仙沟断裂带分布。近2年在石山一带的射气岩浆喷发物中揭露出多条大规模的断裂,这些断裂带的单个断面虽然类似于地震活断层,但它们缺少断错地貌和断层方向的稳定性,一些断层组合成弧形。尽管这些断裂断面清晰,断距达4m,仍被认为是伴随火山喷发活动后期塌陷而形成的次级断层。此外,位于非火山岩分布区跨长流-仙沟断裂带的钻孔联合剖面探测表明,该断裂带在晚更新世晚期以来不活动。长流-仙沟断裂带晚更新世晚期以来的活动主要表现在作为深部岩浆的上涌通道。 相似文献
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本文对五大连池火山群14座火山喷发口的喷发活动期、喷出的火山熔岩特征,岩浆活动期序进行了初步划分与概述,并通过火山地质地貌、新构造活动、火山口周围活化迹象进行初步调查后认为:德都地震与火山尚无直接联系. 相似文献
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长白山西坡—火山地质科考、旅游胜地 总被引：1，自引：0，他引：1
长白山火山是一座中国最大的第四纪层状复式火山,是１０００年前世界上最大的火山喷发之一。至今保留着完好的火山地貌景观,是研究火山活动机制、岩浆演化及火山灾害等方面的重要基地,也是旅游胜地。 相似文献
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长白山天池火山是中国最具有潜在灾害性喷发危险的活动火山。在开展长白山天池火山近代喷发历史的研究中,通过野外考察、粒度分析、岩石化学研究,识别出了一套新的火山喷发物。这套喷发物分布于天池水面东北侧,为一套灰色多层火山碎屑堆积,厚约9.2m。下伏公元1668年的火山空降堆积。粒度分析表明,天池火山最近一次喷发物以空降堆积为主,夹一层薄层涌浪堆积,火山喷发类型为射气岩浆型。涌浪堆积碎屑物的分数维值为2.71。空降堆积的分数维值小于涌浪堆积,综合投点求出的分数维值为2.36。显微镜下可观察到鸡骨架状玻屑,无黏土矿物,为原生火山爆发堆积。火山碎屑堆积物中的浮岩岩石化学分析结果表明岩浆成分为粗面质。根据历史记录、地层层序关系、堆积物特征的综合分析,推测堆积物的形成时间为公元1903年 相似文献
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Field investigation and lab analysis on samples were carried out for Quaternary volcanoes, including Xiaoshan volcano, Dashan volcano and Bianzhuang hidden volcano, in Haixing area, east of North China. Results show that Xiaoshan volcano with the eruptive material of volcanic scoria, crystal fragments and volcanic ash is a maar volcano, the eruptive pattern is pheatomagmatic eruption, and the influence scope is near the crater. Dashan volcano exploded in the early stage, and then the magma intruded, forming the volcanic neck. The eruption strength and scale are limited, and the eruptive materials are scoria, volcanic agglomerate and dense lava neck. The volcanic rocks in Bianzhuang are porosity and dense volcanic rocks and volcanic breccia, reflecting the pattern of weak explosive eruption and lava flow, and the K-Ar age dating on volcanic rocks indicates that the eruption happened in early Pleistocene. Xiaoshan volcanic scoria and Bianzhuang hidden volcanic rocks are mainly basaltic, Dashan volcanic rocks with lower SiO2 content are nephelinite in composition. Their oxide contents have no linear relationship, indicating that there is no magma evolution relationship between these magmas from the three places. Three volcanic rocks all have enrichment of light rare earth. The Bianzhuang volcanic rocks are rich in large ion lithophile elements, and have no high field strength elements Zr and Hf, Ti losses. The volcanic materials from Xiaoshan and Dashan are intensively rich in Th, U, Nb and Ta, and significantly poor in K and Ti. Although the magmas from these three places in Haixing area may all come from asthenosphere, the volcanic materials have different petrological and geochemical features, and relatively independent volcanic structures, therefore, they experienced different magma processes. 相似文献
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The monitoring of the state of active volcanoes, carried out using different parameters, including geochemical, is very important for studies of deep processes and geodynamics. All changes which occur within the crater before eruptions reflect the magma activation and depend on the deep structure of volcano. This paper gives the results of prolonged monitoring of Ebeko volcano, located in the contact zone between the oceanic and continental plates (the Kurile Island Arc). The geochemical method has been used as the basis for eruption prediction because the increase in the activity of the Ebeko in the period from 1963 to 1967 that ended in a phreatic eruption was not preceded by seismic preparation. Investigations carried out at Ebeko volcano give evidence that change of all the chosen geochemical parameters is a prognostic indicator of a forthcoming eruption. This change depends on the type of eruption, and the deep structure and hydrodynamic regime of the volcano. 相似文献
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海口地区的马鞍岭-雷虎岭火山群是中国为数不多的几个休眠火山群之一。通过对区域火山活动期次划分、深部岩浆囊探测以及对火山类型、规模、物质组成和溶岩覆盖面积的分析,总结了海口地区火山活动的时、空、强特征。结合对火山区地震、地磁、体应变和地热等观测资料的分析,对火山区深部岩浆活动的状态进行了初步评估。研究认为海口全新世火山区最后一次火山喷发距今约4 000a左右,其现今火山活动已趋于平静,未来的火山活动可能向1605年琼州7.5级大地震震中区迁移 相似文献
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Wataru Kanda Yoshikazu Tanaka Mitsuru Utsugi Shinichi Takakura Takeshi Hashimoto Hiroyuki Inoue 《Journal of Volcanology and Geothermal Research》2008
The 1st crater of Naka-dake, Aso volcano, is one of the most active craters in Japan, and known to have a characteristic cycle of activity that consists of the formation of a crater lake, drying-up of the lake water, and finally a Strombolian-type eruption. Recent observations indicate an increase in eruptive activity including a decrease in the level of the lake water, mud eruptions, and red hot glows on the crater wall. Temporal variations in the geomagnetic field observed around the craters of Naka-dake also indicate that thermal demagnetization of the subsurface rocks has been occurring in shallow subsurface areas around the 1st crater. Volcanic explosions act to release the energy transferred from magma or volcanic fluids. Measurement of the subsurface electrical resistivity is a promising method in investigating the shallow structure of the volcanic edifices, where energy from various sources accumulates, and in investigating the behaviors of magma and volcanic fluids. We carried out audio-frequency magnetotelluric surveys around the craters of Naka-dake in 2004 and 2005 to determine the detailed electrical structure down to a depth of around 1 km. The main objective of this study is to identify the specific subsurface structure that acts to store energy as a preparation zone for volcanic eruption. Two-dimensional inversions were applied to four profiles across the craters, revealing a strongly conductive zone at several hundred meters depth beneath the 1st crater and surrounding area. In contrast, we found no such remarkable conductor at shallow depths beneath the 4th crater, which has been inactive for 70 years, finding instead a relatively resistive body. The distribution of the rotational invariant of the magnetotelluric impedance tensor is consistent with the inversion results. This unusual shallow structure probably reflects the existence of a supply path of high-temperature volcanic gases to the crater bottom. We propose that the upper part of the conductor identified beneath the 1st crater is mainly composed of hydrothermally altered zone that acts both as a cap to upwelling fluids supplied from deep-level magma and as a floor to infiltrating fluid from the crater lake. The relatively resistive body found beneath the 4th crater represents consolidated magma. These results suggest that the shallow conductor beneath the active crater is closely related to a component of the mechanism that controls volcanic activity within Naka-dake. 相似文献
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An eruption on the eastern flank of Piton de la Fournaise volcano started on 16 November, 2002 after 10 months of quiescence.
After a relatively constant level of activity during the first 13 days of the eruption, lava discharge, volcanic tremor and
seismicity increased from 29 November to 3 December. Lava effusion suddenly ceased on 3 December while shallow earthquakes
beneath the Dolomieu summit crater were still recorded at a rate of about one per minute. This unusual activity continued
and increased in intensity over the next three weeks, ending with the formation of a pit crater within Dolomieu. Based on
ground deformation, measured by rapid-static and continuous GPS and an extensometer, seismic data, and lava effusion patterns,
the eruptive period is divided into five stages: 1) slow summit inflation and sporadic seismicity; 2) rapid summit inflation
and a short seismic crisis; 3) rapid flank inflation, onset of summit deflation, sporadic seismicity, accompanied by stable
effusion; 4) flank inflation, coupled with summit deflation, intense seismicity, and increased lava effusion; and finally
5) little deflation, intense shallow seismicity, and the end of lava effusion. We propose a model in which the pre-intrusive
inflation of Stage 1 in the months preceding the eruption was caused by a magma body located near sea level. The magma reservoir
was the source of an intrusion rising under the summit during Stage 2. In Stage 3, the magma ponded at a shallow level in
the edifice while the lateral injection of a radial dike reached the surface on the eastern flank of the basaltic volcano,
causing lava effusion. Pressure decrease in the magmatic plumbing system followed, resulting in upward migration of a collapse
front, forming a subterranean column of debris by faulting and stoping. This caused intense shallow seismicity, increase in
discharge of lava and volcanic tremor at the lateral vent in Stage 4 and, eventually the formation of a pit crater in Stage
5. 相似文献
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STUDY OF THE LAVA FLOW HAZARD ZONING BASED ON THE KINEMATIC THERMO-RHEOLOGICAL MODEL:EXAMPLE STUDY FOR THE ASHIKULE VOLCANO,XINJIANG 
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下载免费PDF全文 The lava flow hazard is an important and frequent disaster for residents in the volcanic area. In this paper, we focus on the lava flow inundation hazard zoning based on the example case of the Ashikule volcano in Xinjiang, China. Firstly, the parameters of magma such as density, viscosity and temperature are calculated by the empirical formula of magma utilizing results of previous field geological survey and petrology analysis. Then, using the kinematic thermo-rheological model, we simulated the inundation area of lava flow from Ashi volcano at the effusion rates of 200m3/s and 500m3/s. The simulation results of Ashi volcano well coincide to the geological map and verify that the method and parameters are valid. Then the applied simulations were carried out to calculate the lava flow inundation area in future eruption at Ashi, Wuluke and Daheishan crater with different effusion rates. At last, according to the analysis of the applied simulation results and drawing lessons from the foreign disaster zoning method, the four-level hazard zoning was built and set with different colors. The first level with red color is the extra-dangerous zone that is always inundated in any eruption but only distributes near the lava spillway of the crater. The second level with orange color is the dangerous zone that is inundated in the medium scale eruption. The third level with yellow color is the sub-dangerous zone that is corresponding to the large eruption. The fourth level with blue color is the potential dangerous zone that is only inundated in the extra-large eruption. In addition, we put forward the suggestion to respond to and avoid the disaster in future. Although China has not been affected by the lava flow for nearly three hundred years, the prospective study in this paper will lay the foundation for the study of related disasters, and provide the reference for the major construction projects in the volcanic area. 相似文献
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Haraldur Sigurdsson 《Journal of Volcanology and Geothermal Research》1977,2(2):165-186
During the 1971–1972 eruption of Soufrière volcano on St. Vincent Island, a lava mass was extruded subaqueously in the crater lake. An investigation of the chemistry of the lake indicates that over 50,000 tons of dissolved solids were taken into solution during the eruption, in addition to 9000 tons of iron precipitated as ferric oxide in syngenetic metalliferous sediments on the crater floor. Leaching of hot disintegrating lava and volcanic glass is the principal source of cations dissolved in the lake (Na, Ca, Mg, Si and K), whereas chlorine and sulfur were introduced during injection of acid volcanic gases from the submerged lava mass. Concentrations of the common cations in the lake are not affected by mineral solubility, except in the case of Fe3+, but rather by the rate of leaching, evaporation, and water-rock reactions. Variations in Cl/Na, total Cl and acidity have aided in identification of distinct fumarolic phases during the eruption, which may correlate with observed increase in frequency of minor volcanic tremors in the crater. Accumulation of ferric oxide in sediments on the crater floor is thought to be due to leaching of ferrous iron at high temperature from the lava mass, followed by oxidation and precipitation of hematite in the cooler lake. 相似文献
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Systematic measurements of the height of the summit crater rim on the active Karymskii Volcano showed that the variation of that parameter has been greater during its last eruption, lasting, with short intermissions, from January 1, 1996 until now (October 2007) compared with the earlier eruptions. The periodic increases in the height of Karymskii Volcano were due to explosion discharges of unconsolidated pyroclastic material, with most of this falling on the volcano’s cone. The increased seismicity of Karymskii Volcano intensified the slope movement processes, resulting in a comparatively flat area forming periodically on the crater rim; during separate, not very long, periods the height of the volcanic cone was increasing in discrete steps and at a greater rate. The periodic decrease in the height of Karymskii Volcano is due to compaction of pyroclastic material and, to a much greater extent, after violent explosions which expand the crater by removing its nearsummit circumference. The other contributing factor consists in sagging of the magma column due to partial emptying of the peripheral magma chamber, which makes the internal crater slope steeper, hence causes cone collapse and the cone lower. These occurrences are generally similar to the processes of crater and caldera generation described by previous investigators for other volcanoes of the world. 相似文献