This Encyclopedia aims, basically, at summanzmg the wealth of well established facts and outlining the relevant theories in the different branches of physics. With this as goal, the writers were asked to present their specific field in such a way that access is possible to any scientist without special a priori information in that field; the basic concepts of physics are assumed to be known to the reader. The survey given in each paper was also to be long lasting, so that even a few years after publication, each volume would be useful, for example as an introduction for newcomers or as a source of information for workers in a neighbouring field. In the field of geophysics, dealt with in Vols. 47--49 of the Encyclopedia, this task is difficult to achieve because during the last decades there has been a much faster development of basic information and theory than during the decades before. When I came to contribute to this work the famous Julius Bartels, then editor of the geophysical part, told me that Vol. 49 should certainly take into account the results of the "International Geophysical Year" 1957/58 (I. G. Y. ), and that we had better wait until these were accessible than produce a kind of information which might be obsolete in a short time."

In exploration seismology, data are acquired at multiple source and receiver posi tions along a profile line. These data are subsequently processed and interpreted. The primary result of this process is a subsurface image of the exploration target. As part of this procedure, additional information is also obtained about the subsurface material properties, e.g., seismic velocities. The methods that are employed in the acquisition and processing of exploration seismic data are internally consistent. That is, principally near vertical incidence seismic waves are generated, recorded and subsequently imaged. The data processing methods commonly used are based upon a small angle of incidence approximation, thus making the imaging problem tractable for existing data processing technology. Although tremendously successful, the limitations of this method are generally recognized. Current and future exploration goals will likely require the use of additional seismic waves, i.e., both compressional and shear precritical and postcritical reflections and refractions. Also, in addition to making better use of seismic travel times, recent efforts to directly incorporate seismic amplitude variations show that the approach may lead to a better understanding of subsurface rock properties. In response to more demanding exploration goals, recent data acquisition techniques have improved significantly by increasing the spatial aperture and incorporating a large number of closely spaced receivers. The need for better subsurface resolution in depth and position has encouraged the use of 240, 512, and even 1024 recorded data channels with receiver separations of 5 to 25 m."

The idea of writing a textbook on urban surveying and mapping originated with the Commission on Cartography of the Pan American Institute of Geography and History (PAIGH) because of the urgent need for planned and integrated surveying and mapping in urban communities of the American Hemisphere. It is obvious, however, that, with the exception of some European countries, the same situation exists in most cities of the world. The undersigned was asked to undertake the task. The task was not simple. The only available comprehensive text in the field 1 is Geodezja Miejska, which was published recently in Poland and reached the authors only after most of the present text was written. It is tailored to a very specific market and different requirements. Although it is an impressive book, it differs vastly from our own approach. Other reference texts are fragmentary or obsolete. During the last two decades, revolutionary changes have occurred in survey ing and mapping technology which have had a profound effect on actual procedures. In addition, the traditional concepts of urban surveying and map ping are undergoing rapid evolution. It is recognized that administration and planning require a great variety of continuously updated information which must be correlated with the actual physical fabric of the community, as de termined by surveying and mapping. Modern urban surveying and mapping is therefore the foundation of the broad and dynamic information system that is indispensable in any rational municipal effort."

In recent years the significant progress in satellite-based observations of plasma states and associated electromagnetic phenomena in space has resulted in the accumulation of much evidence of various plasma instabilities. Today plasma instabilities are believed to be responsible for electromagnetic radiation as well as for many of the macroscopic dynamics of plasmas in space. Most students who begin to study plasma physics are intrigued by the unstable nature of plasmas compared with other states of matter; however, they often become frustrated because there are so many in stabilities. Such frustration explains in part why there is no textbook which treats this subject exclusively. A description of plasma instabilities in a systematic way is nontrivial and takes a pertinacious effort. This book is an attempt to provide a basic introduction on the subject and covers most of the important instabilities. However, the author must apologize for any omission of references to contributions of individuals who deserve more credit. The reader is assumed to have a general knowledge of plasma physics obtainable in an undergraduate course. The book is intended to be used as a reference text on the subject of plasma instabilities at the under graduate level as well as for a text in a special course in graduate school. Because the book is part of a series on physics and chemistry in space, emphasis is placed on plasma instabilities relevant in space plasmas."

Global climate change is one of the most important environmental issues facing the world today. The United Nations Framework Convention on Climate Change (FCCC) acknowledges the potential for global climate change to have major effects on the world economy. The work of the Intergovernmental Panel on Cli mate Change (lPCC) is focused on evaluating the scientific data on climate change and analyzing the potential responses to it. One of the primary issues in the global climate change debate is how to adapt to any change that might occur. The process ofidentifying adaptation measures and evaluating their effectiveness is the focus of this book. In dealing with climate change adaptation, the sequence of events in conduct ing these types of analyses can be generalized as follows: * Develop scenarios for the possible range of climate change, * Assess the vulnerability of various sectors of the national economy and infrastructure to climate change, and * Identify and evaluate measures in each sector to adapt to the climate change It is this third step that is the subject of this book. In presenting this material, Chapter 1 gives an overview of the concept of climate change adaptation and the general principles guiding the conduct of analyses in this area. Chapters 2-7 give the results of evaluating climate change adaptation options in the agriculture, water resources, coastal resources, forest and ecosystems, fisheries, and human settlements sectors.

Major structural features are used in this study to reconstruct the links which existed between North America, Europe and Africa before the opening of the North Atlantic Ocean. The synthesis of geophysical and geochemical data as well as geological observations allows the recognition of the original geometry of the Grenvillian, Cadomian, Caledonian, Ligerian-Acadian and Hercynian foldbelts and the identification of ancient plate sutures. The reader will find a wealth of information based not only on the English but also on the French and Spanish literature, thus opening less known results to the international community.

This collection of papers is based on a symposium held in 1987 at the Interna tional Union of Geology and Geodesy Congress in Vancouver, British Colum bia. The Symposium was planned as a follow-up to a session at the 1984 Geo logical Society of America Annual Meeting in Reno, Nevada, which dealt with the emplacement of silicic lava domes. In both cases, emphasis was placed on the physical and mechanical rather than chemical aspects of lava flow. The IUGG Symposium consisted of two lecture sessions, a poster session, and two discussion periods, and had 22 participants. The contributions to this volume are all based on papers presented in the various parts of the Sym posium. The motivation for studying lava flow mechanics is both practical and scientific. Scientists and government agencies seek to more effectively predict the hazards associated with active lavas. Recovering mineral resources found in lava flows and domes also requires an understanding of their emplacement. From a more theoretical standpoint, petrologists view lava studies as a way to directly observe the rheologic consequences of mixing crystals, bubbles, and solid blocks of country rock with silicate liquids. This information can then be used to constrain processes occurring in the concealed conduits, dikes, and chambers that feed flows and domes on the surface."

Earthquakes come and go as they please, leaving behind them trails of destruc tion and casualties. Although their occurrence is little affected by what we do or think, it is the task of earth scientists to keep studying them from all possible angles until ways and means are found to divert, forecast, and eventually control them. In ancient times people were awestruck by singular geophysical events, which were attributed to supernatural powers. It was recognized only in 1760 that earthquakes originated within the earth. A hundred years later, first systematic attempts were made to apply physical principles to study them. During the next century scientists accumulated knowledge about the effects of earthquakes, their geographic patterns, the waves emitted by them, and the internal constitution of the earth. During the past 20 years, seismology has made a tremendous progress, mainly because of the advent of modern computers and improvements in data acquisi tion systems, which are now capable of digital and analog recording of ground motion over a frequency range of five orders of magnitude. These technologic developments have enabled seismologists to make measurements with far greater precision and sophistication than was previously possible. Advanced computational analyses have been applied to high-quality data and elaborate theoretical models have been devised to interpret them. As a result, far reaching advances in our knowledge of the earth's structure and the nature of earthquake sources have occurred."

It is now a quarter of a century since Junge and his coworkers recovered the first sample from the sulfate aerosol layer in the stratosphere. Since that time vast strides have been made in determining its physical properties and morphology. These investigations have been performed with instruments on board aircraft and balloon platforms as in the early days, with ground-based lidar (optical radar), and most recently with satellite-borne optical instruments. It will become evident in Chapter 2 that in situ measurements by aircI'aft and, balloon sensors complement rather than duplicate the remote techniques (lidar and satellite). Hence future programs will probably continue to utilize direct as well as indirect experimental techniques. Concurrently, with the observations of the gross properties of the aerosol layer, la oratory and theoretical studies have sought to elucidate the chemical and micro physical processes which influence the formation and growth of the aerosol par ticles. The laboratory investigations have included studies of gas phase chemistry, and particle nucleation and growth mechanisms. Theoretical studies have revolved mainly around a series of models developed by atmospheric scientists. The earliest of these models was constructed by Junge and his colleagues. With the advent of third- and fourth-generation computers, the capacity to solve the quite complex continuity equations whi h govern particle formation, growth, and removal has ad vanced to the point where most of the particle properties can be simulated with reasonable confidence."

The yearbook series Reviews in Modern Astronomy of the Astronomische Gesell three years ago in order to bring the scientific events schaft (AG) was established of the meetings of the society to the attention of the worldwide astronomical community. Reviews in Modern Astronomy is devoted exclusively to the invited reviews, the Karl Schwarzschild lectures, and the highlight contributions from leading scientists reporting on recent progress and scientific achievements at their research institutes. Volume 4 comprises all, eighteen contributions which were presented during the fall meeting of the AG at Preiburg/Breisgau in September 1990. They cover problems in solar research and the solar system as well as the first results of the ROSAT and Hipparcos space missions, stellar and extragalactic studies, and Supernova 1987A in the Large Magellanic Cloud. The Karl Schwarzschild Medal was awarded to Professor Eugene Parker1. His lecture entitled "Convection, Spontaneous Discontinuities, and Stellar Winds and X-Ray Emis*sion" begins this volume.

Geodynamics is commonly thought to be one of the subjects which provide the basis for understanding the origin of the visible surface features of the Earth: the latter are usually assumed as having been built up by geodynamic forces originating inside the Earth ("endogenetic" processes) and then as having been degrad ed by geomorphological agents originating in the atmosphere and ocean ("exogenetic" agents). The modem view holds that the sequence of events is not as neat as it was once thought to be, and that, in effect, both geodynamic and geomorphological processes act simultaneously ("Principle of Antagonism"); however, the division of theoretical geology into the principles of geodynamics and those of theoretical geomorphology seems to be useful for didactic purposes. It has therefore been maintained in the present writer's works. This present treatise on geodynamics is the first part of the author's treatment of theoretical geology, the treatise on Theoretical Geomorphology (also published by the Springer Verlag) representing the second. The present edition is third one of the book. Although the headings of the chapters and sections are much the same as in the previous editions, it will be found that most of the material is, in fact, new."

The message of sunspots from the interior of the Sun to the Earth's climate When Galileo was summoned before the Inquisition on April 12, 1633, the main accusations laid against him concerned the doubts he expressed about Aristotle's theory of the universe. Aristotle's idea was that the Earth was the centre of the cosmos and that all of the stars, including the Sun, turned around it. Moreover, for Aristotle and the world of the Inquisitors, the Sun was a perfect celestial body. Now, Galileo had discovered spots on the Sun. These spots were seen as imperfections, and not just surface markings, but coming from within the Sun. Worse yet, they revolved around the Sun. All this supported the newfangled theory of Copernicus, and undermined a system of thought that had reigned supreme for centuries. Man of science that he was, and a prudent Catholic too, Galileo strived all his life to prove that Copernicus' astronomical concept was compatible with the word of the Bible. He proposed that there were not two truths but a single divine truth. It was just expressed in two different languages : there was the language of the common people, with its imprecision and inconsistencies, but intuitively understandable by everyone; and then there was the precise language of science with its strict regard for observation, which only a chosen few can grasp [L. Geymonat. 1992].

Scientists concerned with the processes occurring in the stratosphere are becoming more and more aware of the role that the stratosphere may play in the global climate and in global change in general. This book focuses on the basic processes taking place in the stratosphere and on the stratospheric changes which may occur from either natural or anthropogenic forcing. Of major concern here is the consequence of the increasing Antarctic Ozone Hole and the possibility of similar processes occurring at northern latitudes. One of the expected consequences of the change in the stratospheric composition, mainly ozone depletion, is the change in the penetration of UV-B in the troposphere, at the surface, and in the top layers of the ocean. Monitoring and modeling of those changes are still in infancy, even though the implications may be of utmost importance for the entire biosphere. Several aspects of these consequences with regard to aquatic ecosystems, terrestrial vegetation and human health are presented by experts in these fields.

The Workshop on the Seismicity and Seismic Risk in the Off shore North Sea Area was intended to bring together experts from a variety of disciplines as well as interest groups with involve ment in siting, design and construction of offshore structures in the region. Participants came from the fields of geology, seismology, oceanography, geotechnical and structural engineering and risk analysis. The wide range of participant affiliations included institutes, Observatories, universities, oil companies, consultants and insurance firms. All nationalities around the North Sea were present, in addition to some experts from outside the region. All participants were present on the basis of personal invitation. The idea of organizing the Workshop stemmed from conside- tions, such as: the rapidly increasing material and personel investments and versatility of type of structures in the basin.during the past decade; - the present-day important role Jf the North Sea oil and gas production in the economy of Western Europe; and - the increase of potential environmental risks in the region. Although devastating earthquakes are almost unknown in the area and seismic hazard is not great, the seismic risk grows with the growing size and number of structures in the area. The study of the potential seismic risks, therefore, cannot be neglected any more. The siting and design of offshore platforms and submarine pipelines are controlled by the degree of their vulnerability as well as the seismic hazard. in the region."

The suggestion by Dr. Franklin S. Harris, Jr., that these books be written arose pursuant to the editor's plaints that despite the implicitly or explicitly ack nowledged importance of both aerosols and particulate matter in innumerable domains of technology and human welfare, investigations of these subjects were generally not supported independently of the narrowest conceivable domains of their appli cations. Frank Harris, who has long been a contributor in one of the important domains of aerosol macrophysics, atmospheric optics, challenged the editor to elaborate his views. Ideally, they would have taken the form of a monograph; however, there is as yet an insufficient body of information to present a unified treatment. At the same time, substantial efforts are in progress in the component fields to hold the promise for the emergence of unifying elements which will even tually facilitate their presentation to be made with a high degree of integrity. There are numerous pertinent and systematic tie-ins between project-oriented aerosol work and basic physical investigations which are themselves quite closely akin to much classical and current work in physical science. The most significant aspect of these tie-ins is their potential for making substantial contributions to the functional needs of the applications areas while stimulating significant questions of basic physics. For this to be possible, it is necessary that the most relevant areas of physics be identified in such a manner as to make clear their re levance for aerosol-related studies and vice versa."

It is now well known that the mid-ocean flow is almost everywhere domi nated by so-called synoptic or meso-scale eddies, rotating about nearly vertical axes and extending throughout the water column. A typical mid ocean horizontal scale is 100 km and a time scale is 100 days: these meso scale eddies have swirl speeds of order 10 cm s -1 which are usually con siderably greater than the long-term average flow. Many types of eddies with somewhat different scales and characteristics have been identified. The existence of such eddies was suspected by navigators more than a century ago and confirmed by the world of C. O'D. Iselin and V. B. Stock man in the 1930's. Measurements from RIV Aries in 1959/60, using the then newly developed neutrally buoyant floats, indicated the main char acteristics of the eddies in the deep ocean of the NW Atlantic while a se ries of Soviet moored current-meter arrays culminated, in POLYGON- 1970, in the explicit mapping of an energetic anticyclonic eddy in the tropical NE Atlantic. In 1973 a large collaborative (mainly U. S., U. K. ) program, MODE-I, produced synoptic charts for an area of the NW At lantic and confirmed the existence of an open ocean eddy field and es tablished its characteristics. Meso-scale eddies are now known to be of interest and importance to marine chemists and biologists as well as to physical oceanographers and meteorologists."

Earth's Rotation from Eons to Days reviews long-term changes, methods of measurement, and the major influences on rotation parameters. In order to understand secular changes, the momentary behavior of ocean tides must be analyzed and appropriately modelled. Researchers and students in astronomy and all fields of geosciences will find a wealth of information related to the interaction of geophysical phenomena and the rotation of the planet Earth.

Little more than ten years have passed since spaceprobe-borne instruments con clusively demonstrated the existence of the solar wind. These observations con firmed the basic validity of a theoretical model, first proposed by E. N. Parker, predicting a continuous, rapid expansion of the solar corona. The subsequent decade has seen a tremendous growth in both the breadth and sophistication of solar wind observations; the properties of the interplanetary plasma near the orbit of the earth are now known in great detail. The theory of the coronal ex pansion has also been highly refilled both in the sense of including additional physical processes, and of treating more realistic (time-dependent and non spheri cally-symmetric) coronal boundary conditions. The present volume is an attempt to synthesize the solar wind observations and coronal expansion models from this decade of rapid development. The ultimate goal is, of course, the interpretation of observed solar wind phenomena as the effects of basic physical processes occurring in the coronal and interplanetary plasma and as the natural manifestations of solar properties and structures. This approach implies an emphasis upon the "large-scale" features revealed by the observations. It requires extensive use of the concepts and methods of fluid mechanics."

The science of Geodesy has undergone far-reaching changes in the last half century. The impact of new technology, from electromag netic distance measurements to the use of artificial satellites, has been great, and is still largely to be felt. These changes have forced the practitioners of the ancient art of Earth measurement to alter their way of thinking about the space that surrounds us, something fundamentally more difficult than absorbing a new technology. A key influence in this modem change in geodetic thinking has been the work of Antonio Marussi, in his scientific publications from 1947 onwards, through his students and collaborators at the Uni versity of Trieste, and in the series of symposia on three-dimensional Geodesy which he organised with his great friend and collaborator, Martin Hotine. His influence on the latter, stemming from their first meeting at the General Assembly of the International Association of Geodesy in Oslo in 1948, was remarkable in itself, leading as it did to the ultimate publication of Hotine's Mathematical Geodesy in 1969."

For many centuries people living on volcanoes have known that the outset of seismic activity is often a forerunner of a volcanic eruption. This understand ing allowed people living close to the sites of the Mt. Nuovo 1538 eruption at Campi Flegrei, Italy, and of the Mt. Usu 1663 eruption, in Hokkaido, Japan (to quote only two examples) to flee before the eruptions started. During the second half of the 19th century seismographs were installed on some volcanoes, and the link between seismic and eruptive activity started to be assessed on a firmer scientific basis. The first systematic observations of the correlations existing between seismic activity and volcanic eruptions were probably those carried out at Mt. Vesuvius by Luigi Palmieri in 1856. Palmieri was the Director of Osservatorio Vesuviano and built an electromagnetic seismograph with the aim of "making visible the smallest ground motions by recording them on paper and indicating direction, intensity and duration." He was able to show the relationship between earthquakes and the different phases of volcanic activity. He identified the harmonic tremor which he indicated was a precursor of volcanic activity: "the characteristic feature of the ground mo tions preceding eruption is its continuity . . . (before the eruption of 1861) the electromagnetic seismograph began to show a continuous tremor." The Palmieri seismograph was also utilized in Japan until 1883, when it was replaced by the new Gray-Milne seismographs, and, later, by the Omori in struments."

Geysers. What makes them work? Many who have seen a geyser in action know only that it spouts hot water into the air. Many others have never seen one. Chapter 1, Geysers of the World, delineates their distinguishing features, locates the geyser regions of the world, and places investigations by world travelers and scientists in historic perspective. One of the quickest ways to become acquainted with a geyser is to observe it. The descriptions of several well known geysers, some based on past observations by others, but frequently by me, do not neces sarily portray current behavior. They do, however, represent general features. Geysers exist as a result of a delicate and unique interplay among the heat, the water, and the rocks of the earth. In essence, heat and water must be available, transported, distributed, stored, and finally released. Chapter 2, The Geologic, Thermal, and Hydrologic State of the Earth, especially that close to its surface, sets the stage for Chapter 3, Fundamentals of Geyser Operation. The geyser is treated here as a simple system consisting of three major interacting elements: a source of water, a source of heat, and a reservoir for storing water. The discus sion centers around the actions occurring within idealized columnar and pool geysers, and more complex systems. Some of the more workable geyser theories are evaluated."

Accretion-collision tectonics in mobile belts is one of the most important new topics in solid earth science. A special seminar on this subject, the Oji International Seminar on Accretion Tectonics, was held from the 10th to 16th September, 1981, in Tomakomai, Hokkaido, Japan. It was sponsored by the Japan Society for the Promotion of Science and the Fujihara Foundation of Science, organizers were S. Uyeda, Earthquake Research Institute, University of Tokyo, Amos Nur, Department of Geophysics, Stanford University, and M. Hashimoto, Department of Geology, National Science Museum, Tokyo. More than fifty geoscientists, thirty from Japan and twenty from abroad, met together to present findings from their recent studies and exchange ideas about accretion-collision phenomena in the circum-Pacific mobile belts. Two field days were also spent in the Horokanai area, central Hokkaido, to examine and the Horokanai ophiolite. The the Kamuikotan high-pressure metamorphic rocks latter is a fragment of ancient ocean floor crust that has been obducted onto the Kamuikotan rocks at the time of collision of the Okhotsk Micro-continent with Asia. The seminar was by no means a large congress. However, to the best of our knowledge, it was the first international conference on accretion-collision tectonics. The meeting was highly successful and we believe that it has opened an important new era in the study of plate tectonics.

The 7th International Conference on Basement Tectonics was held at Queen's University in Kingston, Ontario, Canada, from August 17th to 21st, 1987. Much ofthe conference was devoted to presentations and discussions on "Major Fracture Zones in the Earth's Crust" and "The Tectonic Evolution of North America" . Subsidiary themes at the conference were "Tectonic Controls of Cratonic Basins" and "Basement Structures and Metallogeny" . The conference was characterized by lively discussion amongst a diverse group of participants with a broad spectrum of interests, encouraged by the single-session format of the conference and a generous allotment of time for discussion following each presentation. The following presided over individual sessions and their assistance is greatly acknowledged: D.L. Baars, P.J. Barosh, M.J. Bartholomew, R.e. Bostrom, D.M. Carmichael, E.M. Chown, J.J. Gallagher, M.C. Gilbert, H. Helmstaedt, R.A. Hodgson, Y.O. Isachsen, J. Kutina, P.D. Lowman, S.P. Gay, Jr. and M.J. Rickard.

The subject of this NATO Advanced Study Institute was seismic monitoring under a nuclear test ban - an application of scienti fic knowledge and modern technology for a political purpose. The international political objective of a comprehensive nuclear test ban provided in turn the motivation for our technical and scientific discussions. In order to obtain a historical perspec tive on the progress of the work towards a comprehensive test-ban treaty (CTB), it is necessary to go back to 1958, when a confer ence of scientific experts in Geneva made the first steps toward an international seismic monitoring system. However, agreement on actual capabilities of a monitoring system for verifying compliance with such a treaty was not achieved, and thus the conference did not lead to immediate political results. After the Partial Test Ban Treaty of 1963, which banned nuclear explosions in the atmosphere, outer space and under the seas, renewed interest in the seismological verification of a CTB took place. A number of countries initiated large-scale research efforts toward detecting and identifying underground nuclear explosions, and it was in this context that the large aperture seismic arrays NORSAR and LASA were established. This type of development resulted in excellent seismic data in digital form and was thus of great irnprotance to the seismological com munity."

In this book major construction projects are reviewed. The aim is to present case studies or topics which would stimulate discussion within the areas of environmental policy, economy, ethics or science. By carefully balancing the needs and interests of all involved stakeholders and by observing basic ethical principles, it is possible to resolve the conflicts and to proceed towards constructive cooperation with commonly accepted environmental objectives. The book further contains the key conclusions and recommendations resulting from the "First International Symposium on Large-Scale Constructions in Coastal Environments" held on the island of Norderney from 21-25 April 1997.