International Association of Volcanology and Chemistry of the Earths Interior (IAVCEI)

G JS2: Geodetic, Remote Sensing, and Seismic Methods for Monitoring of Volcanic Activities (IAG, IASPEI, IAVCEI)

In order to study the volcano-mantle dynamics and volcano-climate connections, the monitoring and analysis of both lava-producing and explosive volcanic eruptions and deposits produced by volcanoes are essential. Terrestrial and space geodetic methods, seismic mentods, as well as aircraft and satellite remote sensing techniques are essential tools to collect data for monitoring and analysis and for the development of early warning systems. Within its three sessions, the symposium will concentrate on instrumental and analytical methodologies which help to obtain better understanding of processes before, during, and following volcanic eruptions and are used or proposed for volcano monitoring, volcanic eruption prediction, and early warning systems. Terrestrial and space geodetic techniques for monitoring horizontal and vertical displacements (laser distance measurements, gravity-meter, tiltmeter, GPS Doris, and PRARE space observations) will be covered in Session 1. Airborne and satellite remote sensing methods for acquiring high-resolution multispectral images and the use of radar interferometry from the ERS 1/2 SAR sensors for mapping small-scale topographic changes due to the growth of volcanic domes or the intrusion of magma at shallow depth will be dealt with in Session 2. Seismic methodologies, aimed at revealing the characteristics and origin of volcanic tremors as well as their relationship to volcanic activity and major eruptions will be discussed in Session 3. Automatic event recording, three-component seismometry, broad band seismometry, and special array techniques are considered to be topics of discussion for this session. Lead Convener: C. Reigber (IAG), GeoForschungs Zentrum (GRZ), Department of Kinematics and Dynamics of the Earth, Telegrafenberg A17, D-14473 Potsdam (GERMANY); tel: +49-331-288-1100 or 1114; fax: +49-331-288-1111; e-mail: Co-conveners: A. Hasegawa, tel: +81-22-223-7087; fax: +81-22-264-3292 (JAPAN), A. Linde, tel: 1-202-686-4370 x439; fax: 1-202-364-8726; e-mail: (USA).

M JS5: Effects of Pinatubo (IAMAS, IAVCEI)

This symposium will concentrate on the atmospheric effects caused by the June 15, 1991, eruption of Mount Pinatubo (15.14oN, 120.35oE) in the Philippines. Enormous amounts of SO2 spewed from the volcano created over 30 megatonnes of stratospheric sulphuric acid aerosol which dispersed globally over the ensuing months, warming stratospheric temperatures and cooling the troposphere. In addition, with human-derived chlorine, record low levels in lower stratospheric ozone have been recorded. Papers are requested which deal with characterization of the formation, dispersal, and removal of aerosols, and the influence of these aerosols on radiative and chemical processes, clouds, dynamics, and remote sensing. Lead Convener: P. Mc Cormick, NASA Langley Research Center, Mail Stop 475, Hampton, VA 23665-5225 (USA); tel: 1-804-864-2669; fax: 1-804-864-2671. Co-conveners: G. Brasseur

M JS6: Atmospheric C02 and 02 The Breathing of the Earth (IAMAS, IAVCEI, OCEANS)

The terrestrial biosphere plays an important role in atmospheric CO2 variations on seasonal and interannual time scales. The purpose of this symposium is to provide a forum for scientists from different disciplines to bring together their different approaches to the problem area of biosphere-atmosphere interaction and how that is affected by global change. The main focus will be to define concrete ways to better assess the role of the terrestrial biosphere in the global carbon cycle. Lead Convener: Ingeborg Levin, Institut fur Umweltphysik, Universitat Heidelberg, Im Neuenheimer Feld 366, D-69120, Heidelberg, Germany; tel: +49-221-56-3330; fax: +49-221-56-3405. Co-conveners: P. Tans, D. Schimel

M JS14: Climatic Variability and Forcing Over the Past Millenium (IAMAS, IASPEI, IAVCEI, OCEANS)

This joint symposium invites presentations describing the climate of the past millennium, including its natural variations and changes induced by natural forcing and by human activities. The symposium will cover the means and techniques for reconstruction of the climate and climate forcings over this period, the spatial and temporal patterns of the climate and its variations, the explanations for and causes of these variations, the extent to which natural and human influences can be distinguished over the past two centuries, and the implications of these findings for distinguishing anthropogenic and natural changes in climate in the future. Session themes are planned to include: methods for reconstructing climate, high-resolution records of volcanism and other forcing factors, the Medieval Climate Optimum, the Little Ice Age, the Industrial Period, and the implications of past climate relationships for the future climate. Lead Convener: Michael MacCracken, Office of the U.S. Global Change Research Project, c/o National Science Foundation 300 D Street, S.W., Suite 840, Washington, DC 20024 (USA); tel: 1- 202-651-8250; fax: 1-202-554-6715, e-mail: Co-conveners: C. Folland (UK), P. D. Jones (UK), H. Pollack (USA), A. Robock (USA), S. Self (USA),
U. Mikolajewicz (GERMANY), G. Zielinski (USA).

Subsession AS8: Use of High-Resolution Records of Volcanism in Paleoclimate Reconstruction

This subsession will bring together investigators who are interested in developing high-resolution records of past volcanism (e. g., ice cores and tree rings) and evaluating the significance of those records in regard to improving the global record of volcanism and in postulating the climatic and atmospheric forcing of volcanic activity. Participants are invited from the fields of ice core research in the Arctic, especially drawing on the recently completed ice cores from Greenland, in Antarctica, and in high-altitude, low-latitude regions. Individuals involved in the paleovolcanic component of tree ring research and particularly those involved in the climatic aspect of the tree-ring signal are also invited. Those who use tree rings to directly date volcanic events/deposits close to the volcano itself are also encouraged to participate, as are individuals working in high-resolution sedimentary environments. Specific topics that may be addressed by the speakers are (1) temporal and spatial variability of records within each discipline; (2) comparisons among all the records available; (3) estimations of stratospheric loading of H2SO4 from ice cores for individual eruptions and comparisons with other techniques; (4) importance of locating and identifying tephra and especially microtephra in ice cores and other sedimentary environments; and (5) potential effect of volcanic aerosols on atmospheric circulation and climate, as developed from these proxy records. Lead Convener: Gregory A. Zielinski, Glacier Research Group, University of New Hampshire, Durham, NH (USA); tel: 1-603-862-1012; fax: 1-603-862-2124; e-mail: Co-convener: Stephen Self (USA).

S JS1 Earthquake Generation Processes_Environmental Aspects and Physical Modelling (IASPEI, IAVCEI)

Earthquake generation processes should eventually be described quantitatively in terms of basic equations, which include a fault constitutive law under realistic environmental conditions. Laboratory-based constitutive laws have been proposed, and quantitative description of the entire processes of tectonic stress accumulation, quasi-static rupture nucleation, and subsequent dynamic rupture propagation based on physical principles is in sight. Quantification may be complicated by the mechanical and chemical interaction of fluids with country rock. This research trend should be encouraged because of its great potential for understanding earthquake generation and its consequences for earthquake prediction. The interdisciplinary nature of the subject and the complexity of the problems necessitate the integrated cooperation and discussion of scientists in relevant fields such as seismology, volcanology, geology, and rock physics. We invite contributions on any aspect of earthquake generation, including but not limited to those noted above. Lead Convener: M. Matsu'ura, Department of Earth and Planetary Physics, University of Tokyo, 2-11-16 Bunkyo-ku, Tokyo 113 (JAPAN); tel: +81-3-3812-2111 (x4318); fax: +81-3-3818-3247; e-mail: Co-conveners: T. Lewis (CANADA), C. J. Marone (USA), S. McNutt (USA), M. Takeo (JAPAN).

S JS2: Physical and Chemical Evolution of the Earth (IASPEI, IAVCEI)

This symposium focuses on the physical and chemical processes which occur within the evolving Earth. We seek observational laboratory and theoretical papers bearing on early Earth formation. Topics of interest include magma oceans, primitive atmospheres, core-mantle separation, the effects of heavy bombardment and giant impact, formation and evolution of the atmosphere and ocean, and initial komatiite magmatism. Post-Hadean differentiation processes (including, for example, crust formation, growth of the inner core and putative core-mantle boundary interactions), as well as small- and large-scale fractionation phenomena and related phase diagrams, and physical and chemical properties of minerals are of interest. Papers are requested on the relation of these processes to the present geodynamic picture of the Earth. Also, papers are invited which consider how some of these processes have led to irreversible differentiation (e. g., formation of the continental crust and inner core growth), while others (e. g., development of mantle plume, ocean island, and MORB and volcanic arc rocks from recycled oceanic lithosphere) may be regenerative in nature. Lead Convener: T. J. Ahrens, Seismological Laboratory 252-21, California Institute of Technology, Pasadena, CA 91125 (USA); tel: 1-818-395-6906; fax: 1-818-564-0715 (568 0935); telex: 675425 Caltech PSD; e-mail: Co-conveners: P. Gillet (FRANCE), W. McDonough (AUSTRALIA), E. Ohtani (JAPAN).

S JS8: Modelling the Earth's Interior (IASPEI, IAVCEI, IAG, SEDI)

This session will focus on current knowledge of the state and dynamical processes of the Earth's interior. The focus will be on the determination of the physical properties, state and composition of the mantle and core, and on the seismological, geomagnetic, geodetic, geochemical, and laboratory data used to infer them, as well as models of dynamical processes such as the geomagnetic field and flow in the mantle and core that relate observations to the state of the interior. Lead Convener: R. O'Connell, Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138 (USA); tel: 1-617-495-2532; fax: 1-617-495-8839; e-mail: Co-conveners: G. Masters (USA), M. Brown (USA), V. Dehant (BELGIUM).

V 1: Origin of Large Igneous Provinces

LIPs are massive sequences of flood basalt and associated rocks erupted rapidly onto continental or oceanic crust. They comprise voluminous iron- and magnesium-rich rocks and include continental flood basalts and associated intrusive rocks, volcanic passive margins, oceanic plateaus, submarine ridges, seamount groups, and ocean basin flood basalts. Such provinces do not originate at "normal" seafloor spreading centers. Continental flood basalts such as Karoo, Deccan, or the Colombia River basalts are well known, but the petrological, geochemical, tectonic, and geophysical characteristics of oceanic LIPs (Ontong Java, Kerguelen, Wangellia) have only recently been appreciated. This interdisciplinary symposium will address the origin and evolution of LIPs from Archean through Quaternary time based on recent research in geochronlogy, volcanology, geodynamics, geochemistry, geophysics, petrology, and paleomagnetism. Important questions concerning the origins of LIPs include the following: (1) Do they arise from melting in mantle plumes or are they due to specific arrangements of lithospheric plates?; (2) What is the average composition, the internal structure, and the age distribution of an oceanic LIP?; (3) Is their source principally in the asthenosphere, the plume or the lithosphere?; (4) Are the unusual chemical features of continental flood basalts inherited from lithospheric mantle, from continental crust, or from the plume itself?; (5) Is there a connection between LIPs and major biological extinctions?; (6) What is the contribution of LIPs to crustal growth through time? Lead Convener: Mike Coffin, University of Texas, Austin, TX 78759-8397 (USA); tel: 1-512-471-0429; fax: 1-512-471-8844; e-mail: Co-conveners: Nicholas Arndt (FRANCE), John Ludden (CANADA).

V 2: Seafloor Volcanism

Recent detailed geological, geophysical, hydrological, and geochemical studies of portions of the mid-ocean ridge, back-arc basins, and seamounts have provided us with new insights into the mechanisms, timing, and scales of submarine volcanism and associated hydrothermal activity. Multidisciplinary studies of active portions of the seafloor have allowed us to better constrain the tectonic, magmatic, hydrothermal, and biologic evolution of ridge segments over short time scales. Although seafloor eruptions are rarely witnessed, volcanic events have been monitored and the effects of submarine volcanism have been documented in a number of places. This interdisciplinary syumposium will focus on the detection and mechanisms of seafloor volcanism and their tectonic, hydrologic, biologic, and geophysical consequences. In particular, the following topics will be addressed: (1) volcanological observations and models of seafloor volcanism; (2) remote detection and response to eruptions; (3) temporal and spatial variability in hydrothermal systems and lava chemistry; (4) associations between magma reservoirs, melt migration, eruptive processes, and hydrothermal/biologic activity; (5) off-axis volcanism; (6) geophysical constraints on seafloor volcanism; (7) magma-volatile interactions; (8) radiometric dating of magmatic and hydrothermal events; (9) relationships between spreading rate, crustal structure, and volcanism. Lead Convener: Mike Perfit, Department of Geology, University of Florida, 1112 Turlington Hall, Gainesville, FL 32611 (USA); tel: 1-904-392-2128; fax: 1-904-374-4473; e-mail:

V 3 Magma Degassing and Explosive Eruptions

As they rise to the Earth's surface, volatile-rich silicic magmas degas, vesiculate, and may explode. The nature of this process is only beginning to be understood through the use of theory, field evidence, experimental petrology, laboratory techniques in fluid dynamics, and computer simulation, as researchers from diverse backgrounds converge on the mechanisms causing explosive eruptions. The session invites contributions in all the above disciplines to create a forum in which to exchange new ideas, methods, and insights. Lead Convener: Marcus Bursik, Department of Geology, SUNY Buffalo, Buffalo, NY 14260-1550 (USA); tel: 1-716-645-6800, e-mail: Co-convener: Andrew W. Woods (UK).

V 4: Evolution of Large Volcanic Systems

This symposium will focus on a comparison of the magmatic, structural, and tectonic evolution of large-volume rhyolitic and basaltic volcanic fields. Both rhyolitic ash-flow calderas and continental flood basalt provinces produce single eruptions of hundreds to thousands of cubic kilometers of magma. What are the similarities and differences between the processes that control accumulation and eruption of such vast quantitites of magma? Contributions that provide an overview to these problems, address climatic effect, discuss crustal setting, and examine individual volcanic fields, as well as geophysical and geochemical studies, theoretical models, and syntheses are invited. Lead Convener: John Pallister, USGS, MS903, Denver Federal Center, Box 25046, Denver, CO 80225 (USA);
tel: 1-303-236-1023; fax: 1-303-236-1414; e-mail: Co-conveners: Ken Hon (USA), Jim Cole (NEW ZEALAND), and Marta Mantovani (BRAZIL).

V 5: Dynamics of the Magma/Hydrothermal Interface

Geoscientists recognize chemical and isotopic evidence for magmatic contributions of mass to active and fossil hydrothermal systems, and very high rates of heat discharge from active magmatic-hydrothermal systems require efficient magma-groundwater heat exchange. However, transfer of mass and heat between magma bodies and groundwater remains less well-understood than transport within the magma and hydrothermal systems proper. This session will emphasize (1) evidence for rates of magma-to-groundwater transport, (2) the evolution of porosity and permeability in the near-magma environment, (3) conceptual and quantitative descriptions of magma-to-groundwater transport, and (4) time scales for magmatic-hydrothermal systems. Papers that address magma-water heat exchange in the context of eruptions (explosive interaction) as well as those that deal with the more static hydrothermal problem (relatively continuous interaction) are encouraged. Lead Convener: Steve Ingebritsen, U.S. Geological Survey, Menlo Park, CA (USA); tel: 1-415-329-4422; fax: 1-415-329-4463; e-mail: Co-convener: Claude Jaupart (FRANCE).

V 6: Arc Volcanism and Sedimentation

The purpose of the symposium is to explore the interconnections between subduction and the onset of volcanism and resultant sedimentation. Sedimentation begins immediately at the onset of volcanism, and volcanism occurs after the onset of subduction or extension. Questions to be addressed are the following: How long does it take for the sedimentary signal to be produced in the stratigraphic record? What is the lag time between subduction and the onset of volcanism? Can the onset of volcanogenic sedimentation be used to determine the onset of tectonic activity? How long does it take for sedimentation to begin after the inception of tectonic activity? What is the nature of the sedimentary record and what criteria identifies tectonism? What are the sedimentation rates and the factors that control sedimentation rate and flux rates in arc environments? What are the principal transportation and depositional processes, and the triggers for sediment mobilization in arc environments? What is the relationship between primary eruption events and processes and sedimentary events and processes in arc environments? Lead Convener: R. V. Fisher, Department of Geological Sciences, University of California, Santa Barbara, Santa Barbara, CA, 93106 (USA); tel: 1-805-893-3946; e-mail: Co-conveners: Ray Cas (AUSTRALIA).

V 7 Volcano Flank Instability

The mechanisms for catastrophic failure of the flanks of volcanoes are poorly understood, and yet may be part of the evolution of basaltic shield volcanoes as well as strato-volcanoes. Flank failures produce debris avalanches, mudflows, lateral blasts, and tsunamis, and consequently constitute a significant hazard to human life and property. The purpose of this session is to bring together researchers working on volcanoes in many parts of the world to discuss common problems of flank instability. In particular, the conveners hope to focus discussions on the mechanisms for instability during volcano growth, existing constraints on these mechanisms (both from field mapping of structure and from observed behavior), and important gaps in our mutual understanding of the failure processes. Lead Convener: Roger Denlinger, Hawaiian Volcano Observatory, P.O. Box 51, Hawaii National Park, HI, 96718 (USA); tel: 1-808-967-8825; fax: 1-808-967-8890; e-mail: Co-conveners: Andrea Borgia (ITALY), Paul Okubo (USA).

V 8: Decade Volcano

As a contribution to the International Decade for Natural Disaster Reduction, IAVCEI in 1990 targeted a small set of high-risk volcanoes, termed Decade Volcanoes, for intensive international and interdisciplinary study in order to improve and demonstrate our ability to mitigate volcanic risk. Fifteen Decade Volcano projects have been endorsed by IAVCEI, seven of which are in developing countries. Most of these projects have begun, either with field work, a planning workshop, or both. This workshop will bring together scientists studying or concerned with these volcanoes, summarize results and progress made to date, and discuss plans for the future. Lead Convener: Donald Swanson, U.S.G.S., Department of Geological Sciences AJ20, University of Washington, Seattle, WA 98195 (USA); tel: 1-206-553-5587; fax: 1-206-524-7764). Co-convener: R. Wally Johnson (AUSTRALIA)

V JS1: Mid-Tertiary To Recent Geodynamic Evolution of the Andean Region (IAVCEI, IASPEI, IGCP, ILP)

The aim of the symposium is to integrate geophysical, geochemical, and tectonic data to evaluate the mid-Tertiary to recent evolution of the Andean subduction zone. The symposium will include both overview presentations on the entire Andean and surrounding oceanic plate system, and specific presentations with emphasis on large-scale regional problems. Examples of possible specific topics include Chile ridge-trench collision, aseismic ridge collision, relation of downgoing and overriding plates, character of the continental lithosphere, seismic characteristics of the downgoing plate, relation between magmatism and the downgoing plate magmatic evolution, plateau uplift, and dynamics of shallow subduction zones. Lead Convener: Suzanne Kay, Department of Geological Sciences, Cornell University, Ithaca, NY 14853 (USA); tel: 1-607-255-4701; fax: 1-607-254-4780; e-mail: Co-conveners: Bryan Isacks (USA), Paul Silver (USA).

V JS2: Subduction Zone Processes At 25-200 Kilometers Depth_The Subducting Slab, Mantle Wedge, and the Slab-Mantle Interface (IAV

This symposium features field, petrologic, experimental, geophysical, and geochemical constraints on subduction-zone processes that occur beneath volcanic arcs and forearc regions. Symposium presentations are invited that cover a broad range of topics, including thermal and geochemical evolution, dynamics, hydrology, mineralogy, and rheology of the subducting slab, overlying mantle wedge, and slab-mantle interface, directed toward a better understanding of such processes as arc magma genesis, crust-mantle recycling, and intermediate-depth earthquakes Lead Convener: Simon M. Peacock, Department of Geology, Arizona State University, Tempe, AZ 85287-1404 (USA); tel: 1-602-965-1733; fax: 1-602-965-8102; e-mail: Co-conveners: Gray E. Bebout (USA), Craig Manning (USA).

V JS3: Volcanic Crater Lakes (IAVCEI, IAHS)

Crater lakes offer a unique opportunity to monitor the evolution of a volcano. When a volcano is in its active phase, a crater lake can be used to monitor changes in heat flow and chemistry which may forewarn of renewed activity, and as activity dies away, a crater lake can be used to monitor that decline. Crater lakes can also represent a major hazard: on the one hand they may be physically unstable and on the other they may contain large quantitites of toxic gas_either way they can pose a serious threat to their immediate environment. Lead Convener: Sam Freeth, Geological Hazards Research Unit, University College of Swansea, Swansea SA2 8PP (UK); tel: +44-792-295522; fax: +44-792-205556; e-mail: Co-convener: F. van de Ven (IAHS) (NETHERLANDS).

V JS4: Geochemical and Geophysical Signatures of Mantle Plumes (IAVCEI, IASPEI, IAG, SEDI)

Mantle plumes are fundamental features of mantle dynamics, but they remain poorly understood. This symposium will integrate geochemical and geophysical observations, laboratory and numerical experiments, and theoretical considerations to address some of the more fundamental questions regarding mantle plumes: From what depth do plumes arise? Do they come from both the 670-km discontinuity and core-mantle boundary or just one of these? What is the ultimate source of material in plumes and how do plumes acquire their unique geochemical signatures? What role do mantle plumes play in heat transport, mantle convection, plate motions? What can mantle plumes tell us about the chemical and physical properties of the deep mantle? How has the plume flux varied with time over the history of the Earth? Are there relationships between the geochemical and geophysical properties of mantle plumes? Lead Convener: W. M. White, Department of Geological Science, Cornell University, Ithaca, NY 14853 (USA); tel: 1-607-255-7466; fax: 1-607-254-4780; e-mail: Co-conveners: L. Fleitout (IASPEI), B. Hager (USA), L. Kellogg (USA).

V JW1: Electromagnetic Effects of Earthquakes and Volcanoes (IAVCEI, IASPEI)

Changes in electromagnetic fields during earthquakes and volcanic eruptions have clearly been observed during the past few decades. More importantly, some of the more recent observations suggest that electromagnetic effects also occur prior to these catastrophic events and, if a causal relationship can be demonstrated consistent with reasonable physical processes in the crust during these times, they might be used to anticipate these events. This session seeks to identify (1) new observations of electromagnetic fields and ionospheric disturbances during earthquakes and volcanic eruptions; (2) experiments that have been or might be done to test causality, or the lack thereof, between electromagnetic fields and earthquakes or volcanic eruption; (3) physical mechanisms for the generation of the electromagnetic fields under various boundary conditions that might explain these data, and how these various mechanisms might be independently identified with other geophysical or geochemical data; and (4) coupling mechanisms that could transform electromagnetic fields generated at the source of earthquake and volcanic activity into larger-scale electromagnetic disturbances. Lead Convener: Malcolm Johnston, U.S. Geological Survey, Mail Stop 977, 345 Middlefield Road, Menlo Park, CA 94025 (USA); tel: 1-415-329-4812; fax: 1-415-329-5163; e-mail: Co-conveners: M. Gokhberg (RUSSIA), M. Parrot (FRANCE), Y. Fujinawa (JAPAN).

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IUGG XXI General Assembly