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1.
Over the last 40 years, there have been numerous volcanic eruptions across the North Pacific (NOPAC) region that posed a potential threat to both local communities and transcontinental aircraft. The ability to detect these volcanic clouds using satellite remote sensing and predict their movement by dispersion modeling is a major component of hazard mitigation. The Puff volcanic ash transport and dispersion model, used by the Alaska Volcano Observatory, was used to illustrate the impact that these volcanic ash clouds have made across the NOPAC and entire Polar region over the past 40 years. Nearly, 400 separate ash clouds were analyzed that were either reported or detected to have reached above 6 km (20,000 ft) above sea level, an average of one ash cloud every 1.25 months. Particular events showed that ash clouds can be tracked from Alaska to Greenland (Crater Peak, Mount Spurr in 1992), from Kamchatka to Alaska (Kluvicheskoi Volcano in 1994), from Alaska to California (Mount Cleveland Volcano in 2001) and from multiple events within 1 day (Mount Augustine Volcano in 2006). This study showed the vast number of events that have impacted this Polar region and how tracking them is useful for hazard mitigation.  相似文献   

2.
More than 65 potentially active volcanoes on the Kamchatka Peninsula and the Kurile Islands pose a substantial threat to aircraft on the Northern Pacific (NOPAC), Russian Trans-East (RTE), and Pacific Organized Track System (PACOTS) air routes. The Kamchatka Volcanic Eruption Response Team (KVERT) monitors and reports on volcanic hazards to aviation for Kamchatka and the north Kuriles. KVERT scientists utilize real-time seismic data, daily satellite views of the region, real-time video, and pilot and field reports of activity to track and alert the aviation industry of hazardous activity. Most Kurile Island volcanoes are monitored by the Sakhalin Volcanic Eruption Response Team (SVERT) based in Yuzhno-Sakhalinsk. SVERT uses daily moderate resolution imaging spectroradiometer (MODIS) satellite images to look for volcanic activity along this 1,250-km chain of islands. Neither operation is staffed 24 h per day. In addition, the vast majority of Russian volcanoes are not monitored seismically in real-time. Other challenges include multiple time-zones and language differences that hamper communication among volcanologists and meteorologists in the US, Japan, and Russia who share the responsibility to issue official warnings. Rapid, consistent verification of explosive eruptions and determination of cloud heights remain significant technical challenges. Despite these difficulties, in more than a decade of frequent eruptive activity in Kamchatka and the northern Kuriles, no damaging encounters with volcanic ash from Russian eruptions have been recorded.  相似文献   

3.
Volcanic hazards to airports   总被引：3，自引：1，他引：2  
Volcanic activity has caused significant hazards to numerous airports worldwide, with local to far-ranging effects on travelers and commerce. Analysis of a new compilation of incidents of airports impacted by volcanic activity from 1944 through 2006 reveals that, at a minimum, 101 airports in 28 countries were affected on 171 occasions by eruptions at 46 volcanoes. Since 1980, five airports per year on average have been affected by volcanic activity, which indicates that volcanic hazards to airports are not rare on a worldwide basis. The main hazard to airports is ashfall, with accumulations of only a few millimeters sufficient to force temporary closures of some airports. A substantial portion of incidents has been caused by ash in airspace in the vicinity of airports, without accumulation of ash on the ground. On a few occasions, airports have been impacted by hazards other than ash (pyroclastic flow, lava flow, gas emission, and phreatic explosion). Several airports have been affected repeatedly by volcanic hazards. Four airports have been affected the most often and likely will continue to be among the most vulnerable owing to continued nearby volcanic activity: Fontanarossa International Airport in Catania, Italy; Ted Stevens Anchorage International Airport in Alaska, USA; Mariscal Sucre International Airport in Quito, Ecuador; and Tokua Airport in Kokopo, Papua New Guinea. The USA has the most airports affected by volcanic activity (17) on the most occasions (33) and hosts the second highest number of volcanoes that have caused the disruptions (5, after Indonesia with 7). One-fifth of the affected airports are within 30 km of the source volcanoes, approximately half are located within 150 km of the source volcanoes, and about three-quarters are within 300 km; nearly one-fifth are located more than 500 km away from the source volcanoes. The volcanoes that have caused the most impacts are Soufriere Hills on the island of Montserrat in the British West Indies, Tungurahua in Ecuador, Mt. Etna in Italy, Rabaul caldera in Papua New Guinea, Mt. Spurr and Mt. St. Helens in the USA, Ruapehu in New Zealand, Mt. Pinatubo in the Philippines, and Anatahan in the Commonwealth of the Northern Mariana Islands (part of the USA). Ten countries—USA, Indonesia, Ecuador, Papua New Guinea, Italy, New Zealand, Philippines, Mexico, Japan, and United Kingdom—have the highest volcanic hazard and/or vulnerability measures for airports. The adverse impacts of volcanic eruptions on airports can be mitigated by preparedness and forewarning. Methods that have been used to forewarn airports of volcanic activity include real-time detection of explosive volcanic activity, forecasts of ash dispersion and deposition, and detection of approaching ash clouds using ground-based Doppler radar. Given the demonstrated vulnerability of airports to disruption from volcanic activity, at-risk airports should develop operational plans for ashfall events, and volcano-monitoring agencies should provide timely forewarning of imminent volcanic-ash hazards directly to airport operators.  相似文献   

4.
Remote sensing instruments have been used to identify, track and in some cases quantify atmospheric constituents from space-borne platforms for nearly 30 years. These data have proven to be extremely useful for detecting hazardous ash and gas (principally SO2) clouds emitted by volcanoes and which have the potential to intersect global air routes. The remoteness of volcanoes, the sporadic timings of eruptions and the ability of the upper atmosphere winds to quickly spread ash and gas, make satellite remote sensing a key tool for developing hazard warning systems. It is easily recognized how powerful these tools are for hazard detection and yet there has not been a single instrument designed specifically for this use. Instead, researchers have had to make use of instruments and data designed for other purposes. In this article the satellite instruments, algorithms and techniques used for ash and gas detection are described from a historical perspective with a view to elucidating their value and shortcomings. Volcanic clouds residing in the mid- to upper-troposphere (heights above 5 km) have the greatest potential of intersecting air routes and can be dispersed over many 1,000s of kilometres by the prevailing winds. Global air traffic vulnerability to the threat posed by volcanic clouds is then considered from the perspectives of satellite remote sensing, the upper troposphere mean wind circulation, and current and forecast air traffic density based on an up-to-date aircraft emissions inventory. It is concluded that aviation in the Asia Pacific region will be increasingly vulnerable to volcanic cloud encounters because of the large number of active volcanoes in the region and the increasing growth rate of air traffic in that region. It is also noted that should high-speed civil transport (HSCT) aircraft become operational, there will be an increased risk to volcanic debris that is far from its source location. This vulnerability is highlighted using air traffic density maps based on NOx emissions and satellite SO2 observations of the spread of volcanic clouds.  相似文献   

5.
A critical factor in successfully monitoring and forecasting volcanic ash dispersion for aviation safety is the height reached by eruption clouds, which is affected by environmental factors, such as wind shear and atmospheric instability. Following earlier work using the Active Tracer High Resolution Atmospheric Model for strong Plinian eruptions, this study considered a range of eruption strengths in different atmospheres. The results suggest that relatively weak volcanic eruptions in the moist tropics can trigger deep convection that transports volcanic material to 15–20 km. For the same volcanic strength there can be ~9 km difference between eruption heights in moist tropical and dry subpolar environments (a larger height difference than previously suggested), which appears consistent with observations. These results suggest that eruption intensity should not be estimated from eruption height alone for tropospheric eruptions and also that the average height of volcanic eruptions may increase if the tropical atmospheric belt widens in a changing climate. Ash aggregation is promoted by hydrometeors (particularly liquid water), so the smaller modelled eruptions in moist atmospheres, which have a relatively small ash content for their height and water content, result in a relatively small proportion of fine ash in the dispersing cloud when compared to a dry atmosphere. This in turn makes the ash clouds much more difficult to detect using remote sensing than those in dry atmospheres. Overall, a weak eruption in the tropics is more likely to produce a plume above cruising levels for civil aviation, harder to detect and track, but with a lower concentration of fine ash than a mid-latitude or polar equivalent. There is currently no defined ‘acceptable’ concentration of ash for aircraft, but as these results suggest low-grade encounters in the tropics from undetected clouds are likely, it would be desirable to explore that issue.  相似文献   

6.
中国大陆新生代典型火山区温室气体释放的规模及其成因   总被引：5，自引：5，他引：0  
火山活动能够将地球深部的碳输送到大气圈,是地质碳排放和深部碳循环的重要形式.火山作用不仅在喷发期能够释放大量温室气体,而且在休眠期也能释放巨量的温室气体.在全球变暖的背景下,定量化地研究火山活动对大气圈温室气体含量增加的贡献具有至关重要的意义.本文利用密闭气室法等该领域国际先进的测试技术,测量并计算了长白山、腾冲、五大连池及青藏高原南部的羊八井等典型火山区的温室气体释放规模.结果显示,我国大陆新生代典型火山区向大气圈输送的温室气体总通量约为8.13×106t·a-1,接近107t·a-1级别,相当于全球火山活动导致的温室气体(主要为CO2)释放总量的6%左右.太平洋构造域火山区的温室气体在释放通量与总量方面均低于特提斯构造域,并且太平洋构造域火山气体的地壳混染程度较低,显示出大洋俯冲带与大陆俯冲带火山区温室气体释放的成因差异.  相似文献   

7.
Graphs of the yearly number of volcanoes in eruption from 1900 through 1968 for 21 volcanic areas of the circum‐Pacific belt show fluctuations with statistically significant amplitudes in eight of the areas, and some indication of auto‐correlation and periodicity in 14 of them. Thus, in a total of 16 out of the 21 areas studied, these volcanic pulses appear to be statistically significant. They are best defined in the New Guinea‐Solomons area, Santa Cruz‐New Hebrides‐Matthew Island area, and the West Indies where the numbers of volcanoes in eruption have significant fluctuations in amplitude, are auto‐correlated and tend to be periodic.

The periods (around 17 years) of the western Pacific areas are, with few exceptions, much less than those of the eastern Pacific areas suggesting an overall first‐order cause for these volcanic fluctuations which, in each area, seem to be due to the volcanoes’ responding to regional stress pulses. These may be caused by variations in stress owing to sea‐floor spreading on the East Pacific Rise, the dichotomy of periods being due to a different mantle‐flow regime on either side of it, resulting from the proximity of the Rise to the eastern Pacific margin.

An examination of the years for which the maximum or one less than the maximum number of volcanoes are in eruption suggests that large pulses of volcanic activity tend to migrate southwards.

There are six main pulses in the western Pacific and three in the eastern. The latter are better‐defined and more widely spaced in time. The pulse occurring in the first decade of this century is simultaneous on both sides of the Pacific, a reflexion of the global tectonic instability of this period.

The reason for this southward migration of the volcanic pulses is not yet known. It may be a strain‐release phenomenon.  相似文献   

8.
全球火山活动分布特征   总被引：14，自引：0，他引：14  
根据全球活动火山目录 ,分析研究了全球火山分布的特征 ,描述了各区的火山活动分布 ,总结了火山活动强度的时、空分布特征。全球火山活动可分为三大区 ,西太平洋火山活动区 ,主要与太平洋板块向北西西方向的俯冲活动有关 ;东太平洋火山活动区 ,主要与太平洋东面的小板块 (胡安德富卡板块、科科斯、纳斯卡板块 )向美洲板块的俯冲有关 ;大西洋火山活动区 ,与大西洋和非洲的裂开 ,以及地中海带的活动有关。不同火山区带具有各自的最大喷发等级与相应的复发周期。一条火山弧上活动强度的分布往往是不对称的 ,意味着火山弧在整体上有其动力学的控制机理。火山活动显示了随纬度成带状分布。在 - 10～ 0° ,10 2 0° ,30 4 0°,5 0 6 0°分布有高值带。火山喷发活动还与当地的重力势有关 ,重力势正异常可能与高的正压力有关 ,有利于产生特大喷发。火山活动与大角度的正面俯冲带的弧后火山活动最强 ,当板块运动方向与板块边缘走向成小角度相交时 ,缺少正面俯冲的动力 ,火山活动相对平静。  相似文献   

9.
We studied the volcanic contribution to the global sediment budget in the Pacific Ocean basin. It is the world's oldest (174 m.y.) and largest (≈49% of Earth's surface area) ocean basin and has had a high and continuous tephra influx from intraplate and convergent margin volcanoes through time. Computerized shipboard data from 65 legs of the Deep Sea Drilling Project (DSDP) and the Ocean Drilling Program (ODP) were screened for the presence of volcaniclastic components. Tephra-bearing and tephra-free core sections (standard 1.5- and 0.30-m core catcher sections) were separated, regardless of the mass fraction of tephra present. The percentage of tephra-bearing core sections ("tephra frequency") per site and time span ("age unit") was calculated. The age units were the Quaternary, the subepochs of the Tertiary, and the stages of the Cretaceous. A total of 424 drill sites yielded 1433 usable stratigraphic units. Fifty percent are younger than 13 m.y., corresponding to only approximately 10% of the total interval studied (124.5 m.y.). The percentage of tephra-bearing age units is high throughout (83±6%) and correlates linearly with the total number of age units (R 2 =0.998; n=17). The average tephra frequency (30–50%) fluctuates, because the abundance of age units of different tephra frequency classes (0, 1–33, 34–67, 68–100% tephra frequency) varies with time. This indicates that the Cenozoic increase in tephra production results from increase in volcanicity and not spatial extension of volcanic source areas. The Cenozoic sediments that were recovered are dominated by distal tephra from explosive arc volcanism. Pulses of arc volcanism occurred in the Pliocene–Quaternary (since ≈5 m.y.) and mid-Miocene (≈12–15 m.y.). However, the record of explosive arc volcanism in Paleogene and Cretaceous sediments was either not drilled or has been destroyed by subduction. Except for the Cretaceous (≈70–110 m.y.) volcanic pulse, intraplate volcanism is poorly represented in the tephra record because the drill sites are outside the proximal range (>500–1000 km) of the sources. Thus, the tephra record drilled contains significant gaps that bias the estimate of tephra volume towards the less voluminous distal deposits. Most of the volcaniclastic volume accumulated by mass wasting as volcaniclastic aprons surrounding ocean island volcanoes. Volcaniclastic production rates range from 10,000 to 41,800 km3/m.y. for large intraplate volcanoes and approximately 10–13 km3/km arc length per million years for oceanic island arcs. Extrapolation over the lifetime of major Pacific arcs and hotspot chains, combined with a volume estimate of the distal tephra component, indicates a minimum of 9.3×106 km3 of tephra, corresponding to 23 vol.% of the existing Pacific oceanic sediments. At least two thirds of the tephra volume was deposited in the proximal range and at least half of it is derived from intraplate sources. The large proportion of tephra, its composition, and its localized accumulation causes significant spatial and temporal variation in Pacific oceanic sediments that should have a perceptible impact on the elemental fluxes between ocean, crust, and mantle.  相似文献   

10.
Volcanic ash is the most widespread of all volcanic hazards and has the potential to affect hundreds of thousands, or even millions, of people in the densely populated islands of Indonesia. There is limited information available for this region on the hazard posed by volcanic ash, particularly from volcanoes that have not erupted in recent times. There is a need for computational models capable of accurately predicting volcanic ash dispersal at ground level when coupled with field observations of historical or ongoing eruptive activity. To maximise the effectiveness of such models, they should be readily accessible, easy to use and well tested. Geoscience Australia in collaboration with the Australia-Indonesia Facility for Disaster Reduction and the Indonesian Centre for Volcanology and Geohazard Mitigation has collaboratively adapted an existing open-source volcanic ash dispersion model for use in Indonesia. The core model is the widely used, open-source volcanic ash dispersion model FALL3D. A Python wrapper (name here python-FALL3D) has been developed, which modifies the modelling procedure of FALL3D in order to simplify its use for those with little or no background in computational modelling. The modified procedure does not alter the core functionality of FALL3D, but simplifies the modelling procedure by streamlining the installation process, automating both the pre-processing of input meteorological datasets and configuring and executing each utility program in a single-step process. An application example was presented using python-FALL3D for an active volcano in West Java, Indonesia. The example showed that communities located on the western side of Gunung Gede are always susceptible to volcanic ash ground loading regardless of the seasonal variations in wind conditions, whereas communities on the eastern side of Gunung Gede have a marked increase in susceptibility to ground loading during rainy season conditions when prevailing winds include a strong easterly component.  相似文献   

11.
Olshansky  Robert  Xiao  Yu  Abramson  Daniel 《Natural Hazards》2020,101(1):1-38

Identifying the spatial extent of volcanic ash clouds in the atmosphere and forecasting their direction and speed of movement has important implications for the safety of the aviation industry, community preparedness and disaster response at ground level. Nine regional Volcanic Ash Advisory Centres were established worldwide to detect, track and forecast the movement of volcanic ash clouds and provide advice to en route aircraft and other aviation assets potentially exposed to the hazards of volcanic ash. In the absence of timely ground observations, an ability to promptly detect the presence and distribution of volcanic ash generated by an eruption and predict the spatial and temporal dispersion of the resulting volcanic cloud is critical. This process relies greatly on the heavily manual task of monitoring remotely sensed satellite imagery and estimating the eruption source parameters (e.g. mass loading and plume height) needed to run dispersion models. An approach for automating the quick and efficient processing of next generation satellite imagery (big data) as it is generated, for the presence of volcanic clouds, without any constraint on the meteorological conditions, (i.e. obscuration by meteorological cloud) would be an asset to efforts in this space. An automated statistics and physics-based algorithm, the Automated Probabilistic Eruption Surveillance algorithm is presented here for auto-detecting volcanic clouds in satellite imagery and distinguishing them from meteorological cloud in near real time. Coupled with a gravity current model of early cloud growth, which uses the area of the volcanic cloud as the basis for mass measurements, the mass flux of particles into the volcanic cloud is estimated as a function of time, thus quantitatively characterising the evolution of the eruption, and allowing for rapid estimation of source parameters used in volcanic ash transport and dispersion models.

  相似文献   

12.
Tephrochronology is a powerful tool for dating sedimentary sequences, especially in Patagonia, where a large number of active volcanoes have produced frequent historical eruptions. Short lacustrine sedimentary sequences were extracted from the lakes Moreno Oeste and Ton?ek (Nahuel Huapi National Park). Seventeen volcanic ash layers were identified in both cores, 210Pb and 137Cs were used for dating techniques, and historical volcanic records were employed for correlation. White pumice and glass shards from the tephras were characterised by measuring major and trace element contents by instrumental neutron activation analysis. Two volcanic sources – the Cordón Caulle and the Calbuco volcanoes – were recognised as the prevailing systems that impacted the area in the past 800–1000 a. The Calbuco volcano was mainly responsible for the nine tephras identified in the Lake Ton?ek sequence. Four of these nine tephras also contained material from the Cordón Caulle complex, and could be interpreted as composite tephras or possible reworked ones. The Calbuco volcano showed predominant influences in the Lake Moreno Oeste sequence. Six of the eight tephras identified in such a sequence were from the Calbuco volcano, and three of these six contained material from the Cordón Caulle complex. The other two were from the Cordón Caulle complex, with contributions from the Calbuco volcano in one of them. These findings show that the high frequency of volcanic events in the study region demands an accurate characterisation of the products generated by each source, as well as an evaluation of their spatial distribution, to obtain a consistent framework for dating recent environmental changes. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

13.
《Gondwana Research》2000,3(1):65-77
The late Proterozoic Malani bimodal volcanics constitute the largest suite of anorogenic acid volcanics in India. The volcanism took place during 745±10 Ma ago, succeeding the granitic activity of Abu pluton and ceased before the onset of Marwar sedimentation.On the basis of field evidences, three stages of igneous activity have been recognised. Volcanics of the first stage are mostly basalt with occasional andesite or trachybasalts. These are subsequently covered by the voluminous outpouring of peralkaline and peraluminous rhyolite, basalt, dacite and trachyte flows. The third stage ceased with the outburst of ash flow deposits.The dominant felsic volcanics are rhyolites and rhyodacites spread over an area of about 31, 000 km2. The other rock types associated with rhyolite are trachytes, dacites, pitchstone, welded tuff, vitric, lithic and crystal ash, ignimbrite, obsidian, pyroclastic slates, agglomerate, volcanic breccia and volcanic conglomerates. Majority of the acid volcanics are high potassic and a few are calcalkaline or low potassic in composition.Feldspar geothermometry suggests the temperature of equilibrium to be above 650°C. Similar results were obtained by magnetite-ulvospinel geothermometry. Oxygen fugacity is estimated to be about 10−18 under FMQ-Ni-NiO buffer conditions.Malani volcanism was essentially under terrestrial conditions, although deposition by aqueous conditions are also indicated. The volcanic eruptions have been through fissures, shield volcanoes and central cones. The volcanism was triggered in an extensional tectonic regime of continental crust, where geotherm was raised by the repeated influx of basic magma. The initial basaltic magma was possibly generated at deeper depth by ‘hot spot’ activity. This magma while migrating upwards supplied additional heat for the partial melting of lower sialic crust resulting in the generation of felsic magma. The crustal extension has helped in the upward advancement of the felsic magma.  相似文献   

14.
The Pb and Sr isotope ratios of Plio-Pleistocene volcanic rocks from the Aleutian volcanic arc are used as tracers of the lithospheric subduction process at the converging Pacific and Bering plates. Aleutian arc lavas do not have the same Pb isotopic compositions as volcanic rocks of the subducted Pacific ocean crust or the nearby Pribilof Islands, but appear to contain an ‘old continental crustal component’ with high 207Pb/204Pb ratio, as has been found in some other volcanic arcs.87Sr/86Sr ratios in the Aleutian volcanic arc rocks average 0.70322, slightly higher than fresh volcanic rocks from normal ridge segments, but within the range of values from ‘Icelandic’ ridge segments, oceanic islands and the Pribolof Islands. The Pb and Sr isotopic compositions of Aleutian lavas show a positive correlation and the range of values does not change for volcanoes distributed along strike in the arc, even though the crustal type in the hanging wall of the Benioff zone changes from oceanic in the west to continental in the east. Since the basement of the continental arc segment is older than the basement of the oceanic segment, and probably has a different isotopic character, the constancy of isotopic ratios along the arc argues against contamination by wall rocks of the type exposed in the arc.A sufficient explanation for the isotopic data is the mixture of several per cent of continent-derived sediment with melt derived from the underthrust oceanic crust and overlying mantle. This small amount of contaminant is difficult to document by geophysical observations. Such a model implies extensive recycling of Ba, Pb, K and Rb through volcanism at convergent plate margins like the Aleutians.  相似文献   

15.
《Geodinamica Acta》1999,12(5):279-290
A Digital Elevation Model (DEM) of Mt. Etna is presented; it has altimetric and planimetric resolution of l m and 5 m, respectively, and covers an area of about 120 km2. This 3-D view of Mt. Etna allowed both recognition and location of the main morphostructural and volcano-tectonic features of the volcano. A slope map has been generated from the DEM; on the basis of slope distributions and surface textures, five acclivity domains have been recognized. The largest domain, south of the summit craters, reflects the occurrence of old plateau lavas, distinct from central volcanoes which built the present Etnean volcanic system. Interaction between the central volcanoes, with their summit calderas and failed slopes, produced the other recognised domains. Furthermore, newly identified relevant morphostructural lines are discussed.  相似文献   

16.
Glaciers in the southern province of the Southern Volcanic Zone (SVZ) of Chile (37–46°S) have experienced significant frontal retreats and area losses in recent decades which have been primarily triggered by tropospheric warming and precipitation decrease. The resulting altitudinal increase of the Equilibrium Line Altitude or ELA of glaciers has lead to varied responses to climate, although the predominant volcanic stratocone morphologies prevent drastic changes in their Accumulation Area Ratios or AAR. Superimposed on climate changes however, glacier variations have been influenced by frequent eruptive activity. Explosive eruptions of ice capped volcanoes have the strongest potential to destroy glaciers, with the most intense activity in historical times being recorded at Nevados de Chillán, Villarrica and Hudson. The total glacier area located on top of the 26 active volcanoes in the study area is ca. 500 km2. Glacier areal reductions ranged from a minimum of −0.07 km2 a −1 at Mentolat, a volcano with one of the smallest ice caps, up to a maximum of −1.16 km2 a −1 at Volcán Hudson. Extreme and contrasting glacier–volcano interactions are summarised with the cases ranging from the abnormal ice frontal advances at Michinmahuida, following the Chaitén eruption in 2008, to the rapid melting of the Hudson intracaldera ice following its plinian eruption of 1991. The net effect of climate changes and volcanic activity are negative mass balances, ice thinning and glacier area shrinkage. This paper summarizes the glacier changes on selected volcanoes within the region, and discusses climatic versus volcanic induced changes. This is crucial in a volcanic country like Chile due to the hazards imposed by lahars and other volcanic processes.  相似文献   

17.
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   

18.
Many of the world's most dangerous volcanoes are located in developing countries, which often lack resources for adequate hazard mitigation efforts. Despite technological advances in volcano monitoring, the increasing populations that crowd fertile ash slopes exacerbate the threat of future major volcanic disasters.  相似文献   

19.
基于地下电性结构探讨中国东北活动火山形成机制   总被引：14，自引：2，他引：14  
东北地区是我国现代火山活动最强烈的地区之一，也是许多学者十分关注的地区。本文回顾了前人提出的关于该地区火山成因的研究成果；通过分析在东北活动火山区大地电磁观测研究的地壳上地幔结构和采用大地电磁网观测研究的地幔1000km以上的电性结构成果，发现长白山天池火山区存在地壳岩浆囊，其它活动火山没有发现地壳岩浆囊，但都存在通往地幔的岩浆通道；东北地区在80～120km左右和200～250km可能存在与地幔岩浆囊相关的地幔高温流体。基于电性结构的研究成果，作者提出了一种东北地区可能的活动火山成因假说。认为东北火山的成因可能与西太平洋板块俯冲到中国东北地区的地幔过渡带后产生脱水有密切关系。这种水以矿物组分或流体方式向上运移，在地幔200-250km和80～120km左右聚集，80～120km的聚集区可能是火山喷发的物质来源。  相似文献   

20.
The Indonesian island of Sumatra, located in one of the most active zones of the Pacific Ring of Fire, is characterized by a chain of subduction‐zone volcanoes which extend the entire length of the island. As a group of volcanic geochemists, we embarked upon a five‐week sampling expedition to these exotic, remote, and in part explosive volcanoes (SAGE 2010; Sumatran Arc Geochemical Expedition). We set out to collect rock and gas samples from 17 volcanic centres from the Sumatran segment of the Sunda arc system, with the aim of obtaining a regionally significant sample set that will allow quantification of the respective roles of mantle versus crustal sources to magma genesis along the strike of the arc. Here we document our geological journey through Sumatra's unpredictable terrain, including the many challenges faced when working on active volcanoes in pristine tropical climes.  相似文献   

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