共查询到20条相似文献，搜索用时 15 毫秒
1.
Pyroclastic surge is a dilute and turbulent flow of volcanic gas and tephra that is commonly generated during explosive volcanic eruptions and can threaten lives along its flow paths. Assessing its travel distance and delineating future volcanic hazards have therefore been major concerns of volcanologists. Historical eruptions show that most pyroclastic surges travel a few tens of kilometres or less from their sources. Aeolian or aquagene processes have therefore been evoked for the emplacement of supposed surge deposits much beyond this distance. Here we show that a Cretaceous tuff bed in Korea was emplaced by an exceptionally powerful pyroclastic surge that flowed as far as the most powerful pyroclastic flows that formed the low-aspect-ratio ignimbrites (LARI). This has significant implications for interpreting ancient volcanic eruptions and delineating volcanic hazards by pyroclastic surges, and casts intriguing questions on the eruption dynamics and physics of long-runout pyroclastic surges and their distinction from LARI-forming pyroclastic flows. 相似文献
2.
New factual materials on methane eruptions into the water of Lake Baikal in August 1912 are considered. The regional press
is used as the information source. The spatio-temporal relationship between the gas eruptions and earthquakes, observed in
South Baikal in 1912, is revealed, which permits us to consider this effect as a consequence of seismic activity intensification.
Intensive methane discharge into water is a potential danger for the lake’s ecosystem as was proved by massive death of water
organisms in South Baikal in 1912 during the described phenomena. 相似文献
3.
《Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy》1999,24(11-12):957-961
The process of magma ascent along volcanic conduits during explosive eruptions is numerically simulated by solving the transport equations in the one-dimensional, steady, and isothermal assumptions. The physical model considers the non-equilibrium multiphase flow of a mixture of liquid magma, crystals and/or lithic fragments, and exsolving gas. The liquid magma is treated as a mixture of 10 major oxides plus dissolved water and carbon dioxide, and the gas phase as a mixture of water and carbon dioxide. The model is characterized by a strong coupling between fluid dynamic and constitutive equations, whereby the magma properties like viscosity, density, and gas solubility are calculated on the basis of the chemical composition of the liquid magma and its crystal content, and of the physical conditions along the volcanic conduit. The model predictions obtained by considering many different eruptive conditions reveal complex and sometimes non-intuitive relations between the initial conditions and the predicted flow parameter distribution. The composition of the liquid magma and the amount and composition of volatiles are found to be of major importance in determining the dynamics of magma ascent during explosive eruptions. The results of this modeling can be useful to forecast the volcanic hazard at a given volcano, as the conduit exit flow parameters could constitute initial conditions to study the atmospheric dispersion of the gas-pyroclasts and the dynamics of pyroclastic flows. 相似文献
4.
The examination of the Main Pugachevo gas-water-lithoclastic volcano during the summer of 2005 and GPS-controlled large-scale (1: 1000) mapping revealed its regular but rather peculiar eruption. It was the largest among the eruptions investigated since 1911 and produced a very unusual lithoclastic field with an area of about 100 000 m2 and a volume of about 100 000 m3. The eruption occurred from three distinct active centers and began with a vigorous explosion-like gas burst from one center followed by the noncontemporaneous discharge of a gas-and water-saturated liquid lithoclastic mass from the three centers, which produced a number of flows of different directions and sizes. The flows almost completely covered the smoothed flat open area of the volcano and even invaded the larch forest surrounding the volcano, where they bent, overturned, broke, and occasionally uprooted and dragged over some distance some large trees. The analysis and comparison with all the previously documented eruptions of the Main Pugachevo gas-water-lithoclastic volcano revealed their fairly diverse, sometimes strongly variable character with respect to many parameters: the amount of ejected lithoclastic material; the number of eruption centers; and the proportions of the erupted gaseous, liquid, and solid components. In general, the eruptions show a distinctly multirank periodic character: relatively minor or small low-rank eruptions take place once every 1–2 yr, and large eruptions of a higher rank are much less frequent (supposedly, once in 70 years). 相似文献
5.
Basaltic pyroclastic volcanism takes place over a range of scales and styles, from weak discrete Strombolian explosions (～102–103 kg s?1) to Plinian eruptions of moderate intensity (107–108 kg s?1). Recent well-documented historical eruptions from Etna, Kīlauea and Stromboli typify this diversity. Etna is Europe's largest and most voluminously productive volcano with an extraordinary level and diversity of Strombolian to subplinian activity since 1990. Kīlauea, the reference volcano for Hawaiian fountaining, has four recent eruptions with high fountaining (>400 m) activity in 1959, 1960, 1969 (–1974) and 1983–1986 (–2008); other summit (1971, 1974, 1982) and flank eruptions have been characterized by low fountaining activity. Stromboli is the type location for mildly explosive Strombolian eruptions, and from 1999 to 2008 these persisted at a rate of ca. 9 per hour, briefly interrupted in 2003 and 2007 by vigorous paroxysmal eruptions. Several properties of basaltic pyroclastic deposits described here, such as bed geometry, grain size, clast morphology and vesicularity, and crystal content are keys to understand the dynamics of the parent eruptions.The lack of clear correlations between eruption rate and style, as well as observed rapid fluctuations in eruptive behavior, point to the likelihood of eruption style being moderated by differences in the fluid dynamics of magma and gas ascent and the mechanism by which the erupting magma fragments. In all cases, the erupting magma consists of a mixture of melt and gaseous bubbles. The depth and rate of degassing, melt rheology, bubble rise and coalescence rates, and extent of syn-eruptive microlite growth define complex feedbacks that permit reversible shifts between fragmentation mechanisms and in eruption style and intensity. However, many basaltic explosive eruptions end after an irreversible shift to open-system outgassing and microlite crystallization in melt within the conduit.Clearer understanding of the factors promoting this diversity of basaltic pyroclastic eruptions is of fundamental importance in order to improve understanding of the range of behaviors of these volcanoes and assess hazards of future explosive events at basaltic volcanoes. The three volcanoes used for this review are the sites of large and growing volcano-tourism operations and there is a public need both for better knowledge of the volcanoes’ behavior and improved forecasting of the likely course of future eruptions. 相似文献
6.
7.
中国东北地区新生代火山活动的构造背景 总被引：5，自引：1，他引：4
中国东北地区新生代以玄武岩为主的喷发经历了60~29 Ma、25~15 Ma、＜2 Ma三期及不同喷发期之间的过渡阶段,而每一期又可以分为若干旋回。火山作用形成于不同的构造部位,沿断裂和非断裂分布的玄武岩均有存在,且与不同时期的大陆边缘构造演化相匹配。不同的构造背景下火山活动的分布也不同,且具明显的迁移性。构造环境体现为非造山大陆边缘张裂隙、上地幔上隆的陆内拉张环境、陆内非造山环境等特征。上新世晚期—更新世以来的火山活动与中国西南部地区的大陆板块间的碰撞作用没有关系。 相似文献
8.
J. E. Beget 《Environmental Geology》1983,5(2):83-92
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
9.
年轻火山岩的定年:进展与问题 总被引：1，自引：1，他引：0
年轻火山岩定年对人类的起源与进化、地质年表建立、古环境演化、火山灾害、岩浆演化及地球动力学等研究非常重要。由于年轻样品放射性成因子体积累较少、大气氩含量高,微量的过剩氩极难识别,使得年轻火山岩及其沉积地层高精度定年一直是地质年代学中最具挑战性的课题之一。过去几年,年轻火山岩定年在技术上的进展主要体现在定年精度和准确度不断提升,尤其是利用新型多接收稀有气体质谱对单颗粒样品进行逐步升温~(40)Ar/~(39)Ar定年,是方法学上最重要的进展之一。本文总结了年轻火山岩~(40)Ar/~(39)Ar定年的现状、影响因素和相关定年技术及应用,以引起大家的关注和思考,共同提高我国年轻火山岩定年的技术水平。利用新型多接收质谱和创新的实验方法,通过对全球重要火山喷发事件和年轻国际标准样的研究,广泛开展实验室间的对比是提高国内~(40)Ar/~(39)Ar年代学水平并在年轻火山岩定年中取得突破的重要途径,也是当前~(40)Ar/~(39)Ar年代学研究的重要方向。 相似文献
10.
Alejandro Rodriguez‐Gonzalez Jose L. Fernandez‐Turiel Francisco J. Perez‐Torrado Alex Hansen Meritxell Aulinas Juan C. Carracedo Domingo Gimeno Hervé Guillou Raphaël Paris Martine Paterne 《第四纪科学杂志》2009,24(7):697-709
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
11.
高青油田孔店组火山岩储集特征及成藏规律研究 总被引：4，自引：1，他引：3
应用油藏描述的理论基础和方法。发现高青油田火山岩分为4期喷发,每期均可见气孔玄武岩分布岩层的中上部,致密玄武岩分布于岩层下部。其储集空间中孔隙以气孔、溶孔、长石晶内溶孔为主,裂缝则主要是玄武岩发育的柱状节理与晚期构造缝。储层的发育受岩相、裂缝的发育及不整合面的影响,油气主要沿大断裂两侧及不整合面附近富集,为岩性油藏和裂缝性油藏为主的复合性油藏。 相似文献
12.
Jacqueline Owen 《Geology Today》2016,32(1):30-37
Eruptions beneath ice sheets and glaciers can generate hazardous ash plumes and powerful meltwater floods, as demonstrated by the recent Icelandic eruptions at Eyjafjallajökull in 2010 and at Grímsvötn in 2011. A key scientific objective for volcanologists is to better understand the factors controlling subglacial eruptions, but the eruptions are mostly hidden beneath ice that is often hundreds of metres thick, thereby preventing direct observation. New approaches are therefore needed to reconstruct the factors driving explosive activity and the response of the overlying ice. The dissolved volatile content, preserved in glassy volcanic rock, offers a useful means of reconstructing palaeo‐ice thicknesses. However, for subglacial rhyolite at least, there seems to be little or no correlation between loading pressure and eruptive style. Instead, there is a strong correlation between the pre‐eruptive volatile content, degassing path and eruptive behaviour. It seems that the style of many subglacial eruptions is controlled by the same mechanisms as subaerial eruptions, with explosivity strongly influenced by degassing and magmatic fragmentation. 相似文献
13.
A. Yu. Ozerov 《Petrology》2009,17(7):653-668
Processes in the feeders of basaltic volcanoes during Strombolian-type eruptions were examined with the use of a complex apparatus
for modeling basaltic eruptions (CAMBE), which was designed and manufactured by the authors for this purpose. The experimental
setup consists of modeling and registering units and has a height of 18 m. It was designed with regard for the geometric dimensions
of a natural feeding volcanic system: the ratio of the inner diameter of the feeder to its height is approximately 1: 1000.
CAMBE was the first modeling equipment making possible passing a flow of gas-saturated liquid through the conduit, which allowed
us to study the nucleation of gas bubbles, their growth, coalescence, transformations of the gas structures, and the kinetics
of the gas phase. The experiments were carried out in a manner that made it possible to eliminate effects of structural barriers
and fluctuations in the liquid flow velocity. As a result of the experiments, a new (previously unknown) regime in the flow
of two-phase systems through a vertical conduit was discovered: the cluster regime, which is characterized by systematically
alternating dense accumulations of gas bubbles (bubble clusters) and liquid devoid of a free gas phase. It is demonstrated
that the liquid, bubbly, cluster, and slug regimes systematically grade into one another and are polymorphic modifications
of gas-saturated liquids moving through vertical conduits. Our data led us to propose a new model for the gas-hydrodynamic
movement of magmatic melt through the conduit of a basaltic volcano: depending on the gas-hydrodynamic regime in the volcanic
vent, various types of eruptive activity (up to explosions) may take place. The analyses of basaltic magma explosions allowed
us to describe them from a new standpoint and recognize the following four major modes of their manifestations at the surface:
(1) weak ash explosions early during the cluster regime, (2) strong ash explosions during the mature cluster regime, (3) bomb
explosions during the slug regime, (4) bomb grading to ash explosions during the slug regime associated with trains of small
bubbles. 相似文献
14.
Nabi Musa located at the northern tip of the Dead Sea at 31°48′ N, 35°25′ E is one of fifteen complexes of the Hatrurim Formation or the so-called “Mottled Zone” (MZ) which are fossil mud volcanoes. Self ignition of methane during their eruptions in the Middle–Late Pleistocene caused combustion metamorphism of sediments. Melting foci have been discovered in two craters of Nabi Musa volcano, with numerous veins of paralavas having particular calcic-silicic compositions (Ca2SiO4- and CaSiO3-normative). Their major- and trace-element spectra bear signature of a mixed sedimentary protolith consisting of Cretaceous marine carbonates, marl, and quartz sand. The paralavas inherit high Sr, P, and U enrichments, positive La/La* and Y anomalies, and a negative Ce/Ce* anomaly from calcareous marine sediments, including bituminous and apatite-rich chalks. The presence of quartz arenite in the protolith is responsible for relatively high Ti, Nb, Zr, and Hf while the marl pelitic component accounts for MREE and LREE depletion. The suggested mixing models predict that the Nabi Musa paralavas result from combustion metamorphism of a sediment mixture with 53–60 wt.% chalk, 5–14 wt.% marl, and 27–44 wt.% quartz arenite. The history of mud volcanism at Nabi Musa began with small eruptions that mobilized gas and water from shallow (within 300 m) Turonian carbonate aquifers, and later explosive activity triggered violent gas blowouts from the older terrigenous reservoir of Aptian–Albian Nubian-type sandstone lying as deep as 1300–1500 m. 相似文献
15.
Monitoring for natural hazards like earthquakes, volcanic eruptions and landslides in New Zealand is under taken by GNS Science through the GeoNet project, funded by the Earthquake Commission (EQC). The volcano monitoring function, which includes seismograph and GPS networks, visual observations, webcams, deformation, gas and chemical measurements, assesses the status of New Zealand’s 12 active volcanoes and disseminates warnings as necessary. Interaction with the Wellington VAAC addresses aviation concerns. Near-real-time data is obtained from the monitoring networks and processed via two data centres, with two Duty Officers who respond to pager alerts. Through the National Civil Defence Plan, the volcano monitoring function is delegated to GNS Science, which is responsible for setting the volcanic alert level at each volcano. The Alert level is then used by responding agencies, industries, utility providers and the public to set their response. The New Zealand alert level system is based on the current status of the volcano, and is not necessarily predictive. The aviation industry is one of these responding industries. As a consequence of the 1995 and 1996 eruptions of Ruapehu volcano, it became apparent that the aviation industry required more information than the standard VAAC data and an additional service known as VAAS (NZ Volcanic Ash Advisory System) was established by MetService NZ and GNS Science. This arrangement provides enhanced services to the airlines and ensures rapid dissemination and quantification of information like SIGMET and NOTAM. GNS Science has informal relationships with similar geological based organisations in SW Pacific countries, especially Vanuatu and the Solomon Islands, and is able to quantify information about eruptions in those countries. Similarly, MetService NZ has relationships and is able to obtain pilot reports and updates from the meteorological and air traffic control organisations. 相似文献
16.
Synergy of multiple geophysical approaches to unravel explosive eruption conduit and source dynamics - A case study from Stromboli 总被引：1，自引：0，他引：1
An effective approach to understanding the dynamics of explosive volcanic eruptions and the conduit systems that drive them is through synergy of multiple data sets. Three data sets that lend themselves to ease of integration are seismic, infrasonic and thermal. Although approaches involving these data have been used to record volcanological phenomena since 1862, 1955 and 1965, respectively, their integrated use has only developed since 1999. When combined, these three data sets allow constraint of shallow system geometry and the dynamics of the explosive events that occur within that system. Using Stromboli volcano (Italy) as a case study, we review the complete range of geochemical and geophysical studies that can be applied. In doing so, we aim to show how integration of these diverse studies allows insights into a plumbing system and the dynamics of the eruptive activity that the system feeds. When combined at Stromboli, these data provide constraint of multiple system parameters including chamber depths, gas and magma fluxes, shallow system magma residence times, explosion source depths, and the rise/ejection velocities of ascending gas slugs and ejecta. In turn, these results allow various conduit and eruption dynamic models to be applied and tested.The persistent and repeated mildly explosive events that characterize Stromboli have been modeled in terms of the coalescence of gas within the magma to form large gas slugs that ascend the remaining portion of the conduit to burst at the free surface. Our integrated seismic, infrasonic and thermal data sets indicate that gas coalescence occurs at a depth of ∼260 m, with a typical event frequency of ∼9/h. Infrasonic and thermal data show the explosion source to be located 20-220 m below the vent. Thermal data give emission velocities for the ejected fragments of 8-20 m/s, which converts to gas jet velocities of 23-39 m/s. Tracking these parameters in space and time shows that, although eruptions at Stromboli can be grouped into two characteristic types (simple and complex-each of which characterizes a particular crater, NE and SW, respectively), events within each type show significant short-term variability. The system does, however, appear robust, maintaining its characteristic strombolian eruption style after significant effusive phases and more energetic explosive events. 相似文献
17.
John A. Stevenson Jennie S. Gilbert David W. McGarvie John L. Smellie 《Quaternary Science Reviews》2011,30(1-2):192-209
Rhyolite eruptions in Iceland mostly take place at long-lived central volcanoes, examples of which are found associated with each of the present-day rift-zone ice caps. Subglacial eruptions at Kerlingarfjöll central volcano produced rhyolite tuyas that are notable for their exposures of early-erupted pyroclastic material. Observations from a number of these edifices are synthesised into a general model for explosive rhyolite tuya formation. Eruptions begin with violent phreatomagmatic explosions that generate massive tuff (mT), but the influence of water quickly declines, leading to the formation of massive lapilli-tuffs (mLT) containing magmatically-fragmented vesicular pumice and ash. These are deposited rapidly near the vent, probably by moist pyroclastic density currents, confined by ice but not within a meltwater lake. The explosive-effusive transition is controlled by the ascent rate and gas content of the magma. An unusual obsidian-rich massive lapilli-tuff lithofacies (omLT) is identified and interpreted as pyroclastic material that was intruded into gas-fluidised deposits at the explosive-effusive transition. The effusive phase of eruption involves the emplacement of intrusions and lava caps. Intrusions of lava into the early-erupted phreatomagmatic deposits are characterised by peperitic margins and the formation of hyaloclastite. Intrusions into stratigraphically higher levels of the pyroclastic material show more limited interaction with the host tephra and have microcrystalline cores. Large lava bodies with columnar-jointed margins cap the tuyas and have intrusive basal contacts with the tephras. The main influence of the ice is to confine the rhyolite eruptive products to immediately above the vent region. This is in contrast to subglacial basaltic tuya-forming eruptions, which are characterised by the formation of meltwater lakes, phreatomagmatic fragmentation and subaqueous deposition. The lack of meltwater storage may reduce the potential for large jökulhlaups. 相似文献
18.
We review the current knowledge about Southeast Asian volcanoes and their eruption histories, and focus on identifying tephrochronologic markers representing major explosive eruptions in order to further future palaeoclimate and volcanological studies. Forty-one volcanic edifices in Southeast Asia have been classified as large calderas by Whelley et al. (2015) and thus have, or are likely to have, produced large explosive eruptions with a Volcanic Explosivity Index (VEI) of 6–8. Unfortunately, only 20 such eruptions have known ages, spanning from 1.2 Ma to 1991 ad , and fewer have geochemical data that can be used for tephrostratigraphic correlations. Volcanic products from different geodynamic regions and different sources can generally be distinguished on major element plots (e.g. K2O versus CaO) of matrix glass composition. However, the distinction of multiple eruptions from the same source often requires additional data such as trace element compositions of matrix glass and/or mineral compositions. Biotite, but also magnetite compositions (MgO and TiO2 content in particular) appear to be very discriminating. Up to nine tuffs in addition to the three to four Toba tuffs can be utilised as widespread tephrochronologic markers and span a range from 1.2 to 1.6 Ma to recent. As only a few Holocene major eruptions have been well characterised and dated, many large calderas are still unstudied, and many distal tephra layers are still lacking a source, more tephrochronologic markers can certainly be defined in the future. 相似文献
19.
《International Geology Review》2012,54(9):1059-1097
Kamchatka Peninsula is one of the most active volcanic regions in the world. Many Holocene explosive eruptions have resulted in widespread dispersal of tephra-fall deposits. The largest layers have been mapped and dated by the 14C method. The tephra provide valuable stratigraphic markers that constrain the age of many geological events (e.g. volcanic eruptions, palaeotsunamis, faulting, and so on). This is the first systematic attempt to use electron microprobe (EMP) analyses of glass to characterize individual tephra deposits in Kamchatka. Eighty-nine glass samples erupted from 11 volcanoes, representing 27 well-identified Holocene key-marker tephra layers, were analysed. The glass is rhyolitic in 21 tephra, dacitic in two, and multimodal in three. Two tephra are mixed with glass compositions ranging from andesite/dacite to rhyolite. Tephra from the 11 eruptive centres are distinguished by their glass K2O, CaO, and FeO contents. In some cases, individual tephra from volcanoes with multiple eruptions cannot be differentiated. Trace element compositions of 64 representative bulk tephra samples erupted from 10 volcanoes were analysed by instrumental neutron activation analysis (INAA) as a pilot study to further refine the geochemical characteristics; tephra from these volcanoes can be characterized using Cr and Th contents and La/Yb ratios. Unidentified tephra collected at the islands of Karaginsky (3), Bering (11), and Attu (5) as well as Uka Bay (1) were correlated to known eruptions. Glass compositions and trace element data from bulk tephra samples show that the Karaginsky Island and Uka Bay tephra were all erupted from the Shiveluch volcano. The 11 Bering Island tephra are correlated to Kamchatka eruptions. Five tephra from Attu Island in the Aleutians are tentatively correlated with eruptions from the Avachinsky and Shiveluch volcanoes. 相似文献
20.
《International Geology Review》2012,54(8):712-719
Reports of volcanic eruptions and earthquakes originating from volcanoes indicate that seismic activity preceding the eruption is related not only to eruption magnitude and structure of the volcano, but also to viscosity of the lava at the time of eruption. This follows, since lava of higher viscosity meets greater resistance as it ascends from the magma chamber to the earth's surface and, consequently, greater stress will be produced within and beneath the volcano. The writer gives a condensed statistical breakdown of earthquakes and explosive eruptions of Asama Volcano. The Asama earthquakes treated in the report are mainly those of rather low magnitude (T = 1. 0 sec, V = 350) at the Asama Volcano Observatory, situated 4. 2 km east of the center of the summit crater. This investigation showed that most of the explosive eruptions were preceded by an increase in micro-earthquakes. In addition, an experimental formula for predicting volcanic eruptions, based on the statistical relation between frequency of earthquakes originating from Asama and its explosive eruptions. The forthcoming report (Part II) will discuss the same problem based on seismic observations by more sensitive instruments set nearer the summit crater. — A. Eustus 相似文献