Redefining active volcanoes: a discussion   总被引：2，自引：0，他引：2  

Alexandru Szakács 《Bulletin of Volcanology》1994,56(5):321-325

The analysis of the current definitions of active volcanoes indicates that they are empirical, conventional, inaccurate, nongeological, and arbitrarily constraining. Redefinition is therefore needed. One possible approach is to refine the current empirical definitions. A statistically reasonable and practical redefinition using a geologically based time convention-Holocene or 10000 years-is suggested. A set of time conditions according to volcano typology-i.e. 1000; 10000 and 100000 years for high-frequency basaltic shields, andesitic-dacitic composite volcanoes and low-frequency large silicic calderas, respectively-as further refinement of the empirical definition is also envisaged. Devising a phenomenological definition as a theoretical approach is another possibility, but in practice extant diagnostic means are still unsatisfactory to discriminate accurately between dormant and extinct volcanoes. As a consequence of the redefinition, a classification of volcanoes according to their eruptive status is proposed. Redefinition of active volcanoes might increase accuracy in the usage of basic terms in volcanology and influence volcanic hazard assessment and risk mitigation projects.  相似文献   

五大连池第四纪火山岩层序划分及其构造与生态意义     

曾普胜  丘顺帆  李睿哲  刘斯文  王十安  赵九江 《地球学报》2021,42(6):785-802

大量前人成果和1:5万区调钻孔资料证实,五大连池第四纪火山地层属于水平岩层.因此,该地区第四纪火山地层的划分,是在地表岩石层序与钻孔岩石层序充分划分与对比的基础上进行的.从沉积角度看,五大连池火山地层属于松嫩盆地连续沉积过程中的第四纪短暂幕式火山喷发所形成的水平岩层.本文结合K-Ar同位素测年新资料,将该区第四纪岩石地层重新划分为11个组级地层单位.其中的火山岩石地层可以自下而上划分为:下更新统焦得布玄武岩(1.214—1.113 Ma);中更新统尾山玄武岩(0.62—0.285 Ma);中更新统笔架山玄武岩(0.24—0.132 Ma)和全新统老黑山玄武岩(距今290～288 a),对夹于其间的正常沉积地层也进行了相应的划分.对层状火山岩层序的层位划分和空间分布研究对于理解五大连池火山群的构造背景和生态环境具有特别重要的意义,五大连池火山群处于中国大陆内部的大同—大兴安岭火山岩带的最北东端,是地幔流体向北东方向流动的最前缘;这类富钾的碱性玄武岩的火山喷发活动对东北富饶的黑土地的形成具有重要贡献,火山岩在嫩江平原上塑造的台地和火山锥地形地貌对生态多样性和优质地下水的生态要素具有重要影响.  相似文献   

The Holocene tephrostratigraphic record of Lake Shkodra (Albania and Montenegro)     

Roberto Sulpizio  Aurelien Van Welden  Benoit Caron  Giovanni Zanchetta 《第四纪科学杂志》2010,25(5):633-650

Two cores were recovered in the southeastern part of Lake Shkodra (Montenegro and Albania) and sampled for identification of tephra layers. The first core (SK13, 7.8 m long) was recovered from a water depth of 7 m, while the second core (SK19, 5.8 m long) was recovered close to the present‐day shoreline (water depth of 2 m). Magnetic susceptibility investigations show generally low values with some peaks that in some cases are related to tephra layers. Naked‐eye inspection of the cores allowed the identification of four tephra layers in core SK13 and five tephra layers in core SK19. Major element analyses on glass shards and mineral phases allowed correlation of the tephra layers between the two cores, and their attribution to six different Holocene explosive eruptions of southern Italy volcanoes. Two tephra layers have under‐saturated composition of glass shards (foiditic and phonolitic) and were correlated to the AD 472 and the Avellino (ca. 3.9 cal. ka BP) eruptions of Somma‐Vesuvius. One tephra layer has benmoreitic composition and was correlated to the FL eruption of Mount Etna (ca. 3.4 cal. ka BP). The other three tephra layers have trachytic composition and were correlated to Astroni (ca. 4.2 cal. ka BP), Agnano Monte Spina (ca. 4.5 cal. ka BP) and Agnano Pomici Principali (ca. 12.3 cal. ka BP) eruptions of Campi Flegrei. The ages of tephra layers are in broad agreement with eight ¹⁴C accelerator mass spectrometric measurements carried out on plant remains and charcoal from the lake sediments at different depths along the two cores. The recognition of distal tephra layers from Italian volcanoes allowed the physical link of the Holocene archive of Lake Shkodra to other archives located in the central Mediterranean area and the Balkans (i.e. Lake Ohrid). Five of the recognised tephra layers were recognised for the first time in the Balkans area, and this has relevance for volcanic hazard assessment and for ash dispersal forecasting in case of renewed explosive activity from some of the southern Italy volcanoes. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Nonseismic phenomena in the generation and augmentation of tsunamis     

Patricia A. Lockridge 《Natural Hazards》1990,3(4):403-412

While earthquakes generate about 90% of all tsunamis, volcanic activity, landslides, explosions, and other nonseismic phenomena can also result in tsunamis. There have been 53 000 reported deaths as a result of tsunamis generated by landslides and volcanoes. No death tolls are available for many events, but reports indicate that villages, islands, and even entire civilizations have disappeared. Some of the highest tsunami wave heights ever observed were produced by landslides. In the National Geophysical Data Center world-wide tsunami database, there are nearly 200 tsunami events in which nonseismic phenomena played a major role. In this paper, we briefly discuss a variety of nonseismic phenomena that can result in tsunamis. We discuss the magnitude of the disasters that have resulted from such events, and we discuss the potential for reducing such disasters by education and warning systems.  相似文献   

New K–Ar ages for calculating end-of-shield extrusion rates at West Maui volcano,Hawaiian island chain     

David R. Sherrod  Takashi Murai  Takahiro Tagami 《Bulletin of Volcanology》2007,69(6):627-642

Thirty-seven new K–Ar ages from West Maui volcano, Hawai‘i, are used to define the waning stages of shield growth and a brief episode of postshield volcanism. All but two samples from shield-stage strata have reversed polarity magnetization, so conceivably the exposed shield is not much older than the Olduvai Normal-Polarity subchron, or about 1.8 Ma. The oldest ages obtained are in the range 1.9–2.1 Ma but have large analytical error. Shield volcanism ended about 1.35 Ma, and postshield volcanism followed soon thereafter, persisting until about 1.2 Ma. Exposed shield-stage strata were emplaced at a rate of about 0.001 km³ per year, a rate smaller than historic Hawaiian magmatic rates by a factor of 100. Stratigraphic accumulation rates are similar to those measured previously at Wai‘anae volcano (O‘ahu) or the upper part of the Mauna Kea shield sequence (Hilo drill core, Hawai‘i). These rates diminish sharply during the final 0.3–0.5 m.y. of the shield stage. Hawaiian shield volcanoes begin waning well before their last 0.5 m.y. of life, then end quickly, geologically speaking, if West Maui is representative.  相似文献   

火山活动与构造气候旋回   总被引：5，自引：2，他引：3       下载免费PDF全文

刘嘉麒  郭正府 《第四纪研究》1998,18(3):222-228

火山活动是一种重要的地质现象,它的发生总是与构造运动相关联,构造运动有强有弱,持续时间有长有短,具有旋目性,火山活动同样也具有旋回性。大规模的火山喷发往往会对气候变化产生影响,而影响的程度取决于火山所处的位置和喷发的性质及程度。强烈的火山喷发将造成局部地区乃至全球气温下降,由此人们推测火山喷发多发生在冰期,然而统计资料表明,绝大多数火山喷发发生在间冰期,此时的构造运动也比较活跃,而在冰期时很少有火山喷发。至于火山喷发后在短时间内造成的降温与长时间的冰期不能相提并论。火山活动有旋回性,它影响的气候变化也具备有旋回性,这是构造气候旋回的一种表现形式。  相似文献   

The Late Holocene to Pleistocene tephrostratigraphic record of Lake Ohrid (Albania)     

Benoît Caron  Roberto Sulpizio  Giovanni Zanchetta  Giuseppe Siani  Roberto Santacroce 《Comptes Rendus Geoscience》2010,342(6):453-466

We present in this work a tephrostratigraphic record from a sediment piston core (JO 2004) from Lake Ohrid. Five tephra layers were recognised, all from explosive eruptions of southern Italy volcanoes. A multidisciplinary study was carried out, including stratigraphy, AMS ¹⁴C chronology and geochemistry. The five tephra layers were correlated with terrestrial proximal counterparts and with both marine and lacustrine tephra layers already known in the central Mediterranean area. The oldest is from Pantelleria Island (P11, 131 ka BP). Other three tephra layers are from Campanian volcanoes: X6, Campanian Ignimbrite-Y5 and SMP1-Y3 (107, 39 and 31 ka BP respectively). The youngest tephra layer corresponds to the FL eruption from Etna Volcano (3.4 ka BP). In three cases these recognitions confirm previous findings in the Balkans, while two of them were for the first time recognised in the area, with a significant enlargement of the previous assessed dispersal areas.  相似文献   

海洋大地电磁揭示了西太平洋苏达海山的电阻率结构          下载免费PDF全文

姜杰  张涛  蔡晓仙  吴招才 《海洋学研究》2022,40(2):42-52

为了研究海洋板块内火山的深部电阻率结构及其形成过程,在西太平洋苏达海山进行了海洋大地电磁测量。采用主流数据处理方法SSMT2000进行数据处理,分别对旋转后的实测数据以及根据实测数据得到的两组旋转不变量数据进行一维结构假设下的大地电磁响应测试,对响应最好的YX方向数据进行一维反演,并结合一维正演、地质资料对反演结果进行综合解释。反演结果表明,苏达海山区域地壳厚度为21.5 km左右;较厚的火山碎屑岩层表明苏达海山的构建过程以喷发性的岩浆活动为主,其侵入性的岩浆活动较弱。  相似文献   

Mud volcanism and fluid geochemistry in the Cheleken peninsula,western Turkmenistan     

《Marine and Petroleum Geology》2014

A geological and geochemical study has been carried out to investigate the relationships between major mud volcano structures and deep fluid migration in the Cheleken peninsula, in the South Caspian Basin. The fluid geochemistry allowed the origin and migration of the saline waters and the hydrocarbons to be deduced along with the regional source and reservoir rocks. The emitted waters formed by the mixing of deep highly saline water from the main source rocks of the Maykop Fm with the Caspian-like pore water contained in the Pliocene reservoirs. The water composition is very similar to that emitted by the mud volcanoes in Azerbaijan, allowing comparisons to be done between the reservoirs in the western and eastern sides of the South Caspian Basin. The associated oil is derived from a mixed type II/III kerogen deposited in a sub-oxic marine environment and generated during the early oil window. The oil biomarkers indicate that the source rock is the Maykop Fm., as previously determined for the other areas of the South Caspian Basin.The spontaneous emissions, showing different morphologies, are mainly aligned along normal and transtensive fault systems, which provide effective pathways for rapid fluid ascent from deep reservoirs to the surface.  相似文献   

New evidence of extensive active mud volcanism in the Anaximander mountains (Eastern Mediterranean): The “ATHINA” mud volcano     

V. Lykousis  S. Alexandri  J. Woodside  P. Nomikou  C. Perissoratis  D. Sakellariou  G. de Lange  A. Dahlmann  D. Casas  G. Rousakis  D. Ballas  Chr. Ioakim 《Environmental Geology》2004,46(8):1030-1037

A 3000 km² multibeam survey was carried out on the eastern Anaximander Mountains (Mts), (Eastern Mediterranean). The objective was to obtain detailed bathymetry of known mud volcanoes and identify new sites of active mud volcanism in the area. N-NW of the Amsterdam Mud-Volcano (MV) several mounds and cone-like morphological irregularities with a height of few tens of meters to about one hundred meters were detected and considered as potential MVs on the basis of their distinctive backscattered character. A group of two mounds was selected, the northern mound was sampled, documented as active, and named accordingly Athina MV. These new findings strongly support the presence of extensive active mud volcanism in the Anaximander Mountains especially in the area north of the Amsterdam MV.GEM  相似文献