Emplacement mechanisms of the South Kona slide complex,Hawaii Island: sampling and observations by remotely operated vehicle Kaiko     

Hisayoshi?YokoseEmail author  Peter?W.?Lipman 《Bulletin of Volcanology》2004,66(7):569-584

Emplacement of a giant submarine slide complex, offshore of South Kona, Hawaii Island, was investigated in 2001 by visual observation and in-situ sampling on the bench scarp and a megablock, during two dives utilizing the Remotely Operated Vehicle (ROV) Kaiko and its mother ship R/V Kairei. Topography of the bench scarp and megablocks were defined in 3-D perspective, using high-resolution digital bathymetric data acquired during the cruise. Compositions of 34 rock samples provide constraints on the landslide source regions and emplacement mechanisms. The bench scarp consists mainly of highly fractured, vesiculated, and oxidized aa lavas that slumped from the subaerial flank of ancestral Mauna Loa. The megablock contains three units: block facies, matrix facies, and draped sediment. The block facies contains hyaloclastite interbedded with massive lava, which slid from the shallow submarine flank of ancestral Mauna Loa, as indicated by glassy groundmass of the hyaloclastite, low oxidation state, and low sulfur content. The matrix facies, which directly overlies the block facies and is similar to a lahar deposit, is thought to have been deposited from the water column immediately after the South Kona slide event. The draped sediment is a thin high-density turbidite layer that may be a distal facies of the Alika-2 debris-avalanche deposit; its composition overlaps with rocks from subaerial Mauna Loa. The deposits generated by the South Kona slide vary from debris avalanche deposit to turbidite. Spatial distribution of the deposits is consistent with deposits related to large landslides adjacent to other Hawaiian volcanoes and the Canary Islands.  相似文献   

Smithsonian Institution’s Global Volcanism Network     

Devra?WexlerEmail author 《Bulletin of Volcanology》2004,66(6):562-564

Information included in this summary is based on more detailed reports published in the Bulletin of the Global Volcanism Network, vol. 28, No. 9, September 2003 (on the Internet at ). Edited by scientists at the Smithsonian, this bulletin includes reports provided by a worldwide network of correspondents. The reports contain the names and contact information for all sources. Please note that these reports are preliminary and subject to change as events are studied in more detail. The Global Volcanism Program welcomes further reports of current volcanism, seismic unrest, monitoring data, and field observations.  相似文献   

Instability of exogenous lava lobes during intense rainfall   总被引：1，自引：1，他引：0  

John?SimmonsEmail author  Derek?Elsworth  Barry?Voight 《Bulletin of Volcanology》2004,66(8):725-734

On many volcanoes, there is evidence of a relationship between dome collapse and periods of high precipitation. We propose a mechanism for this relationship and investigate the conditions that optimize failure by this process. Observations of elongate lobes that evolve through exogenous growth of lava domes reveal that they commonly develop tensile fractures perpendicular to the direction of motion. These cracks can increase in depth by localized cooling and volumetric contraction. During periods of high rainfall, water can fill these cracks, and the increase in fluid pressure on the base of the lobes and within the crack can trigger the collapse of the hot exogenous lava domes. Using limit-equilibrium analysis, it is possible to calculate the water and vapor forces acting on the rear and base of the potentially unstable part of the lobe. The model presented is rectangular in cross-section, with material properties representative of andesitic dome rocks. Vapor pressures at the base of cracks are sealed by the penetrating rainfall, which forms a saturated cap within the lobe. This leads to an increase in fluid pressurization both through the underlying gas pressure and the downslope component of the liquid water cap. Fluid pressurization increases as the penetration depth increases. This rainfall penetration depth is dependent on the thermal properties of the rocks, antecedent temperature, lobe geometry, and the intensity and duration of precipitation. Dominant parameters influencing the stability of the lobe are principally lobe thickness, duration and intensity of rainfall, and antecedent lobe temperature. Our modeling reveals that thicker lobes are intrinsically more unstable due to the amplification of downslope forces in comparison to cohesive strength. The increase in the duration and intensity of rainfall events also increases the potential for collapse, as it leads to deeper liquid penetration. Deeper penetration depths are also achieved through lower antecedent temperatures since less fluid is lost through vaporization. Thus, the potential for rain-triggered collapse increases with time from emplacement.Editorial responsibility: D. Dingwell  相似文献   

Diffuse CO<Subscript>2</Subscript> degassing at Vesuvio,Italy   总被引：1，自引：0，他引：1  

Francesco?FrondiniEmail author  Giovanni?Chiodini  Stefano?Caliro  Carlo?Cardellini  Domenico?Granieri  Guido?Ventura 《Bulletin of Volcanology》2004,66(7):642-651

At Vesuvio, a significant fraction of the rising hydrothermal–volcanic fluids is subjected to a condensation and separation process producing a CO₂–rich gas phase, mainly expulsed through soil diffuse degassing from well defined areas called diffuse degassing structures (DDS), and a liquid phase that flows towards the outer part of the volcanic cone. A large amount of thermal energy is associated with the steam condensation process and subsequent cooling of the liquid phase. The total amount of volcanic–hydrothermal CO₂ discharged through diffuse degassing has been computed through a sequential Gaussian simulation (sGs) approach based on several hundred accumulation chamber measurements and, at the time of the survey, amounted to 151 t d^–1. The steam associated with the CO₂ output, computed assuming that the original H₂O/CO₂ ratio of hydrothermal fluids is preserved in fumarolic effluents, is 553 t d^–1, and the energy produced by the steam condensation and cooling of the liquid phase is 1.47×10¹² J d^–1 (17 MW). The location of the CO₂ and temperature anomalies show that most of the gas is discharged from the inner part of the crater and suggests that crater morphology and local stratigraphy exert strong control on CO₂ degassing and subsurface steam condensation. The amounts of gas and energy released by Vesuvio are comparable to those released by other volcanic degassing areas of the world and their estimates, through periodic surveys of soil CO₂ flux, can constitute a useful tool to monitor volcanic activity.Editorial responsibility: H. Shinohara  相似文献   

Nature of the Precambrian metamorphic blocks in the eastern segment of Central Tianshan: Constraint from geochronology and Nd isotopic geochemistry   总被引：4，自引：0，他引：4  

LIU Shuwen  GUO Zhaojie  ZHANG Zhicheng  LI Qiugen & ZHENG Haifei The Key Laboratory of Orogenic Belts  Crustal Evolution  Ministry of Education  China  School of Earth  Space Sciences  Peking University  Beijing  China 《中国科学D辑(英文版)》2004,47(12):1085-1094

The Central Tianshan Tectonic Zone (CTTZ) is anarrow domain between an early Paleozoic southernTianshan passive continental margin and a late Paleo-zoic northern Tianshan arc zone, which is character-ized by the presence of numerous Precambrian meta-morphic basement blocks. Proterozoic granitoidgneisses and metamorphic sedimentary rocks,namely Xingxingxia and Kawabulag and Tianhugroups, are the most important lithological assem-blages in these metamorphic basement blocks, and alittle of …  相似文献   

Zonal propagation of kinetic energy and convection in the South China Sea and Indian monsoon regions in boreal summer   总被引：7，自引：0，他引：7  

CHEN Longxun  GAO Hui  HE Jinhai  TAO Shiyan & JIN Zuhui .Chinese Academy of Meteorological Sciences  Beijing  China  .Nanjing Institute of Meteorology  Nanjing  China  .Institute of Atmospheric Physics  Chinese Academy of Sciences  Beijing  China 《中国科学D辑(英文版)》2004,47(12):1076-1084

As early as in the 1980s, Chinese scientists hadfirst proposed that there exits two summer monsoonsystems in Asia, namely the East Asian summer mon-soon (EASM) and the Indian summer monsoon(ISM)[1-4]. The two monsoon systems are quite dif-ferent in characteristics. Since then, such issue andconclusion had been documented and approved by alot of studies in the past two decades, and was appliedin the guideline of the South China Sea summer mon-soon experiment (SCSMEX), which was undertak…  相似文献   

Recent glacial retreat in High Asia in China and its impact on water resource in Northwest China   总被引：48，自引：0，他引：48  

YAO Tandong    WANG Youqing  LIU Shiying    PU Jianchen    SHEN Yongping & LU Anxin  .Institute of Tibetan Plateau Research  Chinese Academy of Sciences  Beijing  China  .Cold  Arid Regions Environmental  Engineering Research Institute  Chinese Academy of Sciences  Lanzhou  China 《中国科学D辑(英文版)》2004,47(12):1065-1075

There are about 46298 glaciers in the High Asiain China, the total glacial area is about 59406 km , andtotal glacial volume about 5590 km3. These glaciersmainly concentrate around the Himalayas Mountains,Nyainqentanglha Mountains, Kunlun Mountains,Karakoram Mountains and Tianshan Mountains. Theglaciers in the Tibetan Plateau are the major compo-nent of the glaciers in the High Asia in China. Theseglaciers extend north to the arid and desert regions,and become the main water resource in …  相似文献   

Geospatial-temporal analysis of land-use changes in the Yellow River Delta during the last 40 years   总被引：5，自引：0，他引：5  

Qinghua?YeEmail author  Gaohuan?Liu  Guoliang?Tian  Shenliang?Chen  Chong?Huang  Shupeng?Chen  Qingshen?Liu  Jun?Chang  Yanan?Shi 《中国科学D辑(英文版)》2004,47(11):1008-1024

Research on land use/land cover changes (LUCC)has been the core project of the Global EnvironmentalChanges since the 1990s[1—6]. Scientists at home andabroad have been laying emphasis on integrationstudies on land-use change by “space and process”features[7—10] as researches on LUCC are in a greatdeal. It is of paramount important for us to studyLUCC at various spatial-temporal scales and build aquantitative assessment of land-use conversion by in-tegrated spatial-temporal features. …  相似文献   

Environmental records of lacustrine sediments in different time scales: Sediment grain size as an example   总被引：2，自引：0，他引：2  

CHEN Jing’an  WAN Guojiang  David Dian Zhang  ZHANG Feng & HUANG Ronggui . State Key Laboratory of Environmental Geochemistry  Institute of Geochemistry  Chinese Academy of Sciences  Guiyang  China  . Department of Geography  Geology  University of Hong Kong  Pokfulam Road  Hong Kong  China 《中国科学D辑(英文版)》2004,47(10):954-960

Understanding the past is the key to know thepresent and to predict the future. As a core project ofthe International Geosphere Biosphere Program, PastGlobal Changes (PAGES) aims to reconstruct theevolution history of global climate, global environ-ment and global ecosystem with resort to all kinds ofnatural records, so as to reveal the change rules(change processes, change amplitude and change rate)of the global environment and thus provide scientificbasis for predicting climate changes p…  相似文献   

Discovery of agglutinated foraminifers from the Longzhaogou Group in eastern Heilongjiang Province   总被引：1，自引：1，他引：0  

LI Gang & YU Shanmao. State Key Laboratory of Paleobiology Stratigraphy  Nanjing Institute of Geology  Paleontology  Chinese Academy of Sciences  Nanjing  China  .th Coal-prospecting Team of Geological Bureau  NE China  Inner Mongolia Coal Company  Jixi  China Correspondence should be addressed to Li Gang 《中国科学D辑(英文版)》2004,47(2):122-127

The low diversity agglutinated foraminifers are recovered from the Qihulin Formation of the Longzhaogou Group in eastern Heilongjiang, China. The foraminiferal fauna consists of 9 species of 5 genera. The common members are Cribrostomoides nonioninoides (Reuss), Haplophragmoides concavus (Chapman), H. gigas minor Nauss. Although the diagnostic zonal taxa are absent in the agglutinated fauna, according to the global stratigraphic distribution of the above-mentioned species, and the associated Pseudohaploceras ammonite fauna, the foraminiferal fauna may be of a Barremian-Aptian (Early Cretaceous) age.  相似文献