Union Lecturers

Chaotic Dynamics and Complexity in Three Geophysical Fluids (Dick Peltier, Canada)
Ozone Depletion and Global Change (Susan Solomon, USA)
Fresh Waters of the World (Uri Shamir, Israel)
New Issues in Climate Change Forcings (Marie-Lise Chanin, France)
Sea Level, Ice Sheets, and the Physics of the Earth (Kurt Lambeck, Australia)

Union Symposia

U 1 Human Impact and the Earth's Environment Looking to the 21st Century and 3rd Millennium

Dynamic processes taking place in the solid Earth, oceans, atmosphere and ionosphere are unstable and sensitive to direct and indirect influence from technogenic activities such as the creation of artificial lakes, extraction of minerals, testing of nuclear devices, launching of heavy rockets, and the pollution of ocean and atmosphere. Such activities cause a complex chain of events whose character differs distinctly from the nondisturbed scenario. These changes are accumulated with time and increasing industrial activity. Eventually they result in an increase of influence anthropogenic component which appears as increased instability of geophysical processes in a broad range of spatial and temporal scales, magnified fluctuations, and an increase in the magnitude of catastrophic events and their frequency. Being mostly passive observers now and apparently in the 21st century, humanity must control and correct the natural and artificial processes in time to mitigate natural disasters. This symposium is devoted to the problems of naturally or artificially induced and triggered processes in and between the lithosphere, oceans, atmosphere, and outer space. Lead Convener: Alexei V. Nikolaev, Institute of Physics of the Earth, Academy of Sciences, Bolshaya Gruzinskaya 10, Moscow (RUSSIA); tel: +7-095-254-9072; fax: +7-095-271-3028; e-mail: sge@adonis.ias.msk.su. Co-convener: Roger G. Bilham, Department of Geological Sciences, Campus Box 250, University Colorado, Boulder, CO 80309 (USA); tel: 1-303-492-6189; fax: 1-303-492-1149; e-mail: bilham@spot.colorado.edu.

U 2 Migration of Chemical Elements in the Earth's System

This symposium will address comprehensive views of how chemical elements are distributed within the solid and fluid domains of the Earth, of the way they are transferred among the different domains, of their use as tracers of fluid dynamics and water quality and of their potential to forecast catastrophic events. Contributed papers will be scheduled as oral or poster presentations at the discretion of the conveners. Lead Conveners: Paolo Gasparini, Dipartimento di Geofisica e Vulcanologia, Largo San Marcellino 10, Universita di Napoli Federico II, 80138 Napoli (ITALY); tel: +39-81-551-6200; fax: +39-81-552-7631. Norman E. Peters, U. S. Geological Survey, Water Resources Division, 6481-B Peach Tree Industrial Blvd., Doreville, GA 30360 (USA);
tel: 1-404-903- 9100; fax: 1-404-903-9199.

U 3 The Hidden Earth as Revealed from Space

The Earth is a dynamic system_it has a fluid, mobile atmosphere and oceans, a continually changing global distribution of ice, snow, and ground water; a fluid core that is undergoing hydromagnetic motion; a mantle both thermally convecting and rebounding from glacial loading of the last ice age; and mobile tectonic plates. In addition, numerous geologic hazards such as volcanic eruptions, landslides, flooding, and earthquakes occur over a variety of time scales. Analysis of modern space-based observations of the Earth system have permitted new and unique insights into the dynamic Earth and its processes and have improved our understanding of the interactions between the Earth's various subsystems. This symposium will focus on the current and anticipated future advances permitted by space-based techniques. The program will feature both invited and contributed papers, with the oral sessions being composed primarily of invited presentations. Lead Convener: Jean O. Dickey, MS 238-332, JPL/Caltech, Pasadena, CA 91109 (USA); tel: 1-818-354-3235; fax: 1-818-393-6890; e-mail: jod@logos.jpl.nasa.gov. Co-conveners: Peter Mouginis-Mark IAVCEI (USA), Jeff Dozier IAHS (USA), F. W. Taylor IAMAS (UK), Kurt Lambeck IASPEI (AUSTRALIA), Susanna Zerbini ILP (ITALY), Jean-Louis Fellous IAPSO (FRANCE), Atsuhiro Nishida IAGA (JAPAN).

U 4 Dynamic Complexity

The evolution of the Earth is governed by intensely nonlinear processes occurring within its core, mantle, atmosphere, and oceans_processes that often lead to chaotic behavior and thus loss of predictability. These subsystems evolve under the action of both forcing and dissipation (and the subtleties of their interconnections) and are seldom amenable to description in terms of models that embody a small number of active degrees of freedom. This symposium will explore a wide range of research in the geophysical sciences in which the challenge of dynamic complexity has come to be seen as central to further progress. Focal issues may include the geodynamo and its mechanism of reversal, the mantle convection process and the extent of its control by phase transition effects, the physics of earthquakes, the thermohaline circulation of the oceans, the breaking-wave-driven circulation of the stratosphere, and the interaction between the solar wind and the Earth's magnetic field across the magnetopause. Contributed papers for this all-Union symposium will be scheduled as oral or poster presentations at the discretion of the conveners. Lead Convener: Richard W. Peltier, Physics Department, University of Toronto, Toronto, ON M5S 1A7 (CANADA); tel: 1-416-978- 2938; fax: 1-416-978-8905; e-mail: peltier@rainbow.physics.utoronto.ca. Co-conveners: John Rundle (USA), D. Rothman (USA).

U 5 Recreating the Solar System

Comparative planetology traditionally emphasizes objects more than processes. But the discovery of ongoing volcanism at Io and Triton; the post-Voyager realization that planetary rings are dynamical, transient features; and the recent planet-shaking cometary impacts with Jupiter have raised processes to a higher level of importance. Within the last two decades, the number of planetary processes seen operating right now at more than one place in the solar system has grown to an impressive list. At one time, planetologists considered the solar system to be like an autonomous machine whose stock is itself, whose product is itself, and whose mechanisms are ongoing planetary processes. What are these processes that are continually recreating the solar system? How do they maintain the semblance of stasis in the face of constant change? Given their dynamic stability, would other planetary systems under their operation resemble ours, and in what ways? This session poses these questions as a complementary approach to the subject of comparative planetology_a process-centered approach instead of the traditional object-centered approach. One can categorize planetary processes in numerous ways. For definiteness, this session groups them under the titles: "Collapse and chaos," "Impacts," "Volcanism," "Convection," "Interactions of surfaces with plasmas," and "Life." Collapse and chaos cover the processes believed to create, at many places in the galaxy, solar systems that are perhaps like ours. Yet these processes also differentiate the locations, masses, and compositions of the objects within these solar systems. Impacts create distinctive interior structures, alter angular moments, and punctuate the histories of solar system objects. Yet impacts also tend to cause similarities in the appearance and composition of surfaces and atmospheres, and they recreate the characteristic rings and dust around the giant planets. Volcanism affects some atmospheres directly, being a major source of volatiles, while in others it may only perturb conditions set by other processes. On surfaces, volcanic landforms are similar throughout the solar system. Convection drives tectonic motions, creates atmospheric zones, and tends to homogenize surfaces through erosion. It also generates magnetism, which gives rise to a similarly structured suite of planetary magnetospheres, differentiated by size and interior features. These magnetospheres are also powered by forms of convection. The interactions of plasmas and charged particles with surfaces and atmospheres tend to erode surfaces and produce auroral phenomena, but they act differently across the solar system. Finally, life differentiates the one atmosphere and surface where it is known to operate. Each process in this short list homogenizes and differentiates, and often does so to more than one class of object. Thus the list of topics to discuss is longer than the list of processes. Speakers will address the topics and give their assessments of the roles various processes have had in creating the solar system and are having in recreating the solar system. Lead Conveners: George L. Siscoe, Department of Atmospheric Science, UCLA, Los Angeles, CA 90024 (USA); tel: 1-310-825-9378; fax: 1-617-377-3160; Torrence V. Johnson, Jet Propulsion Laboratory, MS 183-501, 4800 Oak Grove Drive, Pasadena, CA 91109 (USA); tel: 1-818-393-7957; fax: 1-818-354-6256.

U 6 Origin and Evolution of the Continental Lithosphere

Understanding the nature of the continental crust, especially its lower regions, has long been considered a challenging question. It has become clear in recent years that answering that challenge requires considering the crust and the underlying mantle lithosphere together. It is also important to establish how the continental crust originated and has been subsequently modified. Interactions with other parts of the Earth system, such as the asthenosphere, the hydrosphere, the atmosphere, and oceanic environments, are equally important. The planned interdisciplinary symposium will consider results from seismological, heat-flow, magnetic, gravity, electrical, isotopic, geochemical, and geological studies. Emphasis is sought on integrated, interdisciplinary approaches to attempts to resolve the problems that arise in addressing the origin and evolution of the continental lithosphere. Lead Convener: Kevin Burke, Department of Geosciences, University of Houston, Houston, TX 77204-5503 (USA); tel: 1-713-743-3397; fax: 1-713-748-7906; e-mail: kburke@uh.edu. Co-conveners: S. Ross Taylor (AUSTRALIA), John F. Dewey (UK), Vladimir Cermak (CZECH REP), H. G. Kahle (SWITZERLAND), Tom Jordan (USA).

U 7 Inverse Problems in Geodesy and Geophysics

This symposium is intended to draw together people working on inverse problems in several fields so that new inversion strategies can be brought to the attention of practitioners and the relative merits of popular methodologies examined. Consequently, a central theme will be methodologies and philosophies of inverse theory. Theory and strategies for nonlinear inverse problems are of particular interest, as are papers on deterministic or stochastic methods for constructing acceptable models, or classes of models. Papers are encouraged on inverse problems arising in structural and earthquake seismology, electromagnetics, satellite dynamics, the downward continuation of gravity data from satellite observations, the inverse gravimetric problem, and ionospheric tomography using GPS. Lead Conveners: Fernando Sanso, Dipartmento di Ingegneria Idraulica, Ambientale del Rilevamento, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (ITALY); tel: +39-2-2399-6506; fax: +39-2-2399-6530; Malcolm Sambridge, Research School of Earth Sciences, Australian National University, Canberra, ACT 0200 (AUSTRALIA); tel/fax: +61-62-57-2737; e-mail: malcolm@rses.anu.edu.au.

U 8: Natural Disaster Reduction

A critical assessment is made of the International Decade of Natural Disaster Reduction (IDNDR) at its halfway point. The progress and problems of the IDNDR are evaluated through invited surveys of the present and future scope of each of the main hazards and their global variations. Significant successes of the application of geophysical, hydrologic, and geodetic knowledge to disaster reduction have recently occurred in the case of tsunamis, floods, volcanic eruptions, and earthquakes, and analysis of these cases and unpredicted modern disasters demonstrates the urgency and necessity of basic geophysical research involving new instrumentation and modelling. Astonishing results can be achieved with satellite and airborne measurements with high-precision mapping, for example, of crustal deformation around active faults and volcanoes. The power and need for enhanced global instrumentation for surveillance and monitoring at a wide range of time rates of geological hazards are discussed. The great magnitude of natural dangers in many densely populated regions of the world is addressed in terms of improved transfer of research to engineering practice, zoning, and risk reduction planning. An integrated approach to acceptable preparation against disasters is proposed. Contributed papers will be scheduled as oral or poster presentations at the discretion of the conveners. Lead Convener: Bruce A. Bolt, Seismograph Station, University of California at Berkeley, Berkeley, CA 94702 (USA); tel: 1-510-642-7030; fax: 1-510-643-5811.

U 9: The 1995 Intergovernmental Panel on Climate Change (IPCC) Report

The symposium will give the lead authors of the science chapters for the Intergovenmental Panel on Climate Change 1995 Report the opportunity to present their main results and will permit discussion of these results by the wider scientific community. No contributed papers are sought, but contributions from the floor will be welcomed. Lead Convener: Brian J. Hoskins, Department of Meteorology, University of Reading, Reading RG6 2AU (UK); tel: +41-734-318-950; fax: +41-734-352-604; e-mail: hoskins@swssner1.rdg.ac.uk. Co-convener: Sir John Houghton, Rutherford Appleton Laboratory, Chilton, Didcot, OX11. 0QX, (UK).

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IUGG XXI General Assembly