Several excellent books on weil log interpretation have already been published. However, I feel that these books do not place enough emphasis on the inherent uncertainties in tool responses or on the related and very practical problern of selecting suitable data points for statistical or quantita tive calculations. Thus, I have written this book not only to introduce the newcomer to this very complex art and science, but also to provide him or her with the necessary tools to produce better interpretations. The problems at the end of each chapter are essential to a more complete understanding of the subject matter and include many practical notes based on problems I have encountered in actual applications. This book emphasizes that you develop your own concepts and understanding of the underlying principles, rather than acquiring a compendium of knowledge based on certain rules of thumb. If you are to successfully interpret welllogs, you need to be able to apply your knowledge to new problems that may not follow the preconceived ideas and approaches you would follow if you approached weil log analysis from a cookbook standpoint.

An accessible account of the ways in which the world's plant life affects the climate. It covers everything from tiny local microclimates created by plants to their effect on a global scale. If you ve ever wondered how vegetation can create clouds, haze and rain, or how plants have an impact on the composition of greenhouse gases, then this book is required reading."

This book is written as a practical field manual to effective. Each geolOgist has to develop his/her be used by geologists engaged in mineral explo own techniques and will ultimately be judged on ration. It is also hoped that it will serve as a text results, not the process by which these results and reference for students in Applied Geology were reached. In mineral exploration, the only courses of universities and colleges. The book 'right' way of doing anything is the way that aims to outline some of the practical skills that locates ore in the quickest and most cost-effective turn the graduate geologist into an explo manner. It is preferable, however, for an individ rationist: . It is intended as a practical 'how to' ual to develop his/her own method of operation book, rather than as a text on geological or ore after having tried, and become aware of, those deposit theory. procedures which experience has shown to work An explorationist is a professional who search well and which are generally accepted in indus try as good exploration practice. es for ore bodies in a scientific and structured way. Although an awkward and artificial term, The chapters of the book approximately fol this is the only available word to describe the low the steps which a typical exploration pro totality of the skills which are needed to locate gramme would go through. In Chapter 1, the and define economic mineralization."

Mineral deposits are non-renewable; they do not grow in the ground. Sustainable use of finite mineral wealth requires that revenues from mineral extraction be invested in renewable wealth, education and infrastructure, machines and other production equipment, or in financial assets. Different countries, states and provinces have done so with a varying degree of success. Investing for Sustainability: The Management of Mineral Wealth highlights mineral rents investment funds in Norway, Alaska and Alberta, all of which derive considerable revenues from the production of petroleum bound to diminish over time. The book examines the institutional and political framework in which these funds are embedded and how successfully they have been used for making non-renewable petroleum wealth permanent. Investing for Sustainability: The Management of Mineral Wealth begins with a discussion of the elusive concept of sustainability. New technology and substitution has made a resource like peat obsolete long before it became exhausted physically. Jevons' famous book "The Coal Question" is discussed at some length as a case of unwarranted concern about the depletion of resources. The book also highlights other cases which strike a less happy note. Nauru, one of the smallest sovereign states in the world, has for decades lived off phosphate resources that are now running out. Nauru attempted to make its phosphate wealth permanent through investment funds but failed. Despite its success with its Permanent Fund, less of the oil wealth of Alaska has been made permanent than would appear warranted, and the same is true of Alberta and Norway. Judging from the experiences of the three funds, and the current political debate in Norway, Investing for Sustainability: The Management of Mineral Wealth suggests that it is essential that the citizenry at large benefit directly from mineral rents investment funds if they are to succeed.

Discussing all aspects of offshore surveying in a single volume, this book provides all algorithms necessary to develop complete software suites, and gives a large number of quality control criteria. It is invaluable to professional surveyors, offshore engineers and geophysicists, providing them with a wealth of data in a single volume. It is also a valuable reference work for hydrographic surveyors, seismic navigators and operations geophysicists. This book brings together information on spheroids, datums, projections and binning; gives a complete listing of UKOOA P1/90 and P2/91 formats for data transfer; a field guide to the calibration of radio navigation systems and compasses, acoustic and laser measuring devices; GPS, including calibration, use and differential techniques; field manual for quality control of all aspects of offshore surveying; listing of typical specifications for inclusion in survey contracts; and a comprehensive glossary of relevant terms for offshore surveying.

Oil shales are broadly dermed as petroleum source rocks containing sufficiently high contents of organic matter (above ca 10-15 wt. %) to make utilisation a possibility. Like coal, the world's reserves of oil shales are vast being many times larger than those proven for crude oil. Indeed, some of the largest deposits occur in the USA and Europe where Estonia and Turkey have large reserves. The first recorded interest in oil shale retorting was an English patent in 1694 (Eele, Hancock and Porter, No. 330) which refers to distilling noyle from some kind of stone." The oil shale retorting industry dates back to the middle of the last century, notably Scotland, Estonia, France and Sweden in Europe. Indeed, my own Department at the University of Strathclyde has a historical link with James "Paraffin" Young, the founder of the Scottish oil shale industry who endowed a chair in Applied Chemistry. The growth of the oil industry saw the demise of the oil shale industry in most countries with the notable exception of Estonia, where kukersite has continued to be used for power generation and retorting. However, oil shale utilisation has attracted renewed attention since the early 1970s as a source of transport fuels and chemical feedstocks due to the the long term uncertainties over crude oil supplies.

Since the Arab oil embargo of 1974, it has been clear that the days of almost limitless quantities of low-cost energy have passed. In addition, ever worsening pollution due to fossil fuel consumption, for instance oil and chemical spills, strip mining, sulphur emission and accumulation of solid wastes, has, among other things, led to an increase of as much as 10% in the carbon dioxide content of the atmosphere in this century. This has induced a warming trend through the 'greenhouse effect' which prevents infrared radiation from leaving it. Many people think the average planetary temperatures may rise by 4 DegreesC or so by 2050. This is probably true since Antarctic ice cores evidence indicates that, over the last 160000 years, ice ages coincided with reduced levels of carbon dioxide and warmer interglacial episodes with increased levels of the gas in the atmosphere. Consequently, such an elevation of temperature over such a relatively short span of time would have catastrophic results in terms of rising sea level and associated flooding of vast tracts of low-lying lands. Reducing the burning of fossil fuels makes sense on both economic and environmental grounds. One of the most attractive alternatives is geothermal resources, especially in developing countries, for instance in El Salvador where geothermal energy provides about a fifth of total installed electrical power already. In fact, by the middle 1980s, at least 121 geothermal power plants were operating worldwide, most being of the dry steam type.

In 1981 Chile's military government dictated a new Water Code that radically changed the country's previous water rights system by strengthening private property rights, favoring market incentives, and reducing state regulation. Against the Current: Privatization, Water Markets, and the State in Chile is the first empirical and interdisciplinary study of water markets in Chile, which is the leading international example of free market water policies. Against the Current: Privatization, Water Markets, and the State in Chile challenges the glowing reports given by neoliberals in Chile and the World Bank, showing that the results of this economic experiment have actually been rather mixed. Within the agricultural sector the Water Code has worked fairly well, although the market incentives to conserve water have been ineffective and water rights trading has been less active than expected. The Code's impact has been more negative at the level of river basins, where the institutional framework has revealed critical flaws in coordinating multiple water users and resolving conflicts. Against the Current: Privatization, Water Markets, and the State in Chile combines law, political economy, and geography to analyze the disadvantages, problems, and wider contexts of water markets. This book will appeal to everyone interested in property rights, market-friendly environmental policies, the political economy of sustainable development, and the intersection of economics with law and institutions.

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."

Here is another contribution in the continuing series on Computer Methods in the Geosciences. As its title suggests, this volume will be of interest to explorational geochemists who want to analyze their own data on a personal computer (PC). To make it easy for the user, the programs and two trial data sets are provided on the accompanying diskettes. And, by supplying the diskettes, another first is accom plished for the series: instant involvement and interaction for the user. Although other books in the series have provided listings of computer pro grams, Exploration-Geochemical Data Analysis with the IBM PC is the first to supply diskettes. The diskettes, along with the instructions outlined in the text, eliminate the bother (and errors) of pu tting the programs in man ually. The suite of programs for handling and sorting data files; computing and displaying summary statistics; and working with logarithms, geochemical thresholds, and regression - will give geochemists a good repertoire for geochemical exploration data analysis. The diskettes are easy to use and have been tested thoroughly."

variegated seismological conditions has been accumulated. The method has been developed further in two main directions: - the perfection of the techniques and equipment of three-component field studies incorporating a continuous control of the identity of equipment both in deep boreholes and on the surface; - the creation of efficient and straightforward software for the automatic processing of PM data. Whereas the early stages of development of the method have been conspicuous chiefly by the use of polarization for the discrimination of the wave field, in recent years the emphasis shifts to the use of polarization parameters to obtain additional information about the Earth. This is especially important, as the polarization parameters are very sensitive to inhomogeneities in cross-section and enable those parameters of the Earth to be studies which cannot be obtained from kinematics. Here one should especially mention the polarization of transverse waves, which can act as one of the most reliable parameters for identifying and studying anisotropic properties of the Earth. At present various modifications of PM are being developed applicable both to uphole - (PM RW = reflected waves method, PM CDP = common-depth-point method, PM refracted-wave method, PM of regional studies utilizing earthquakes) and to downhole observations (PM VSP = vertical seismic profiling). Not all the PM modifications are developing at the same rate. The method which has up to now been developed most extenSively is PM VSP.

GOLD: History and Genesis of Deposits is the product of an effort by the Society of Economic Geologists to publish materials that will expand knowl edge concerning timely, specific topics important to the study of economic geology and to economic geologists. A volume on gold was selected for a general review-type publication because of the importance of the gold mining industry in the 1980s. The officers and council of the Society of Economic Geologists authorized the preparation of this book on gold in 1981, and Dr. Robert W. Boyle was selected as its author. Dr. Boyle has extensive experience in the study of gold deposits. He has an international reputation and a broad interest and understanding of the gold mining industry, the origin of gold deposits, and the history of gold as a metal and ore from prehistoric times to recent. Dr. Boyle uses important publications on gold deposits as source materials to document the various pathways of geological thought over time to introduce the reader to modern concepts. The book contains a wealth of information concerning gold."

Shallow Gas determination, prior to drilling, is carried out using 'Engineering Seismic' survey methods. Seismic acquisition data quality is fundamental in achieving this objective as both the data processing methods and interpretation accuracy are subject to the quality of the data obtained. The recent application of workstation based data analysis and interpretation has clearly demonstrated the importance of acquisition data quality on the ability to determine the risks of gas with a high level of confidence. The following pages summarise the 5 primary issues that influence acquisition data QC, suggests future trends and considers their potential impact. The primary issues covered in this paper are: A. Seismic B. Positioning C. QC Data Analysis D. Communications E. Personnel 90 SAFETY IN OFFSHORE DRll.LING FIELD QC ...................... PRIMARY COMPONENTS COMMERCIAL TECHNICAL 1 OPERATIONAL FIGURE 1 HYDROSEARCH The often complex influences of Technical, Commercial and Operational constraints on the acquisition of high quality data require careful management by the QC supervisor in order to achieve a successful seismic survey data set. The following pages only consider the Technical aspects of QC and assume that no Commercial or Operational restrictions are imposed in the achievement of optimum data quality. It is noted however, that such restrictions are frequently responsible for significant compromise in data coverage and quality during routine rig site surveys.

Tarquin Teale, a sedimentology/stratigraphy postgraduate student at the Royal School of Mines, was killed in a road accident south of Rome on 17 October 1985. Premature death is a form of tragedy which can make havoc of the ordered progress which we try to impose on our lives. As parents, relatives and friends, we all know this, and yet somehow when it touches our own world there is no consolation to be found anywhere. In Tarquin's case the enormity of the loss felt by those of us who knew him can barely be expressed in words. Tarquin had everything which we aspire to. His fellow graduate students envied his dramatic progress in research. We his advisors, in appreciating this progress, marvelled at how refreshingly rare it was to see such precocious talent combined with such a caring, modest and well-balanced personality. He was des tined for the highest honours in geoscience and there is no doubt that he would have lived a life, had he been granted the chance, which would have spread colour, intellectual insight and goodness."

Surface waves form the longest and strongest portion of a seismic record excited by explosions and shallow earthquakes. Traversing areas with diverse geologic structures, they 'absorb' information on the properties of these areas which is best retlected in dispersion, the dependence of velocity on frequency. The other prop erties of these waves - polarization, frequency content, attenuation, azimuthal variation of the amplitude and phase - arc also controlled by the medium between the source and the recording station; some of these are affected by the properties of the source itself and by the conditions around it. In recent years surface wave seismology has become an indispensable part of seismological practice. The maximum amplitude in the surface wave train of virtually every earthquake or major explosion is being measured and used by all national and international seismological surveys in the determination of the most important energy parameter of a seismic source, namely, the magnitude M, . The relationship between M, and the body wave magnitude fI1t, is routinely employed in identification of underground nuclear explosions. Surface waves of hundreds of earthquakes recorded every year are being analysed to estimate the seismic moment tensor of earthquake sources, to determine the periods of free oscillations of the Earth, to construct regional dispersion curves from which in turn the crustal and upper mantle structure in various areas is derived, and to evaluate the dissipative parameters of the mantle material."

This collection of papers originates from a meeting are in current use on board UK research vessels. organized in May 1988 at the Geological Society, Marine geological exploration requires information under three further headings: (i) the "shape" of the London, under the auspices of its Marine Studies Group. The meeting was concerned with reviewing sea floor, (ii) the nature of the rocks and sediments the present state-of-the-art of marine geological and which lie at its surface, and (iii) the nature of deeper geophysical sampling and surveying techniques. structures. Studies of the shape of the sea floor The pace of scientific exploration of the ocean (bathymetry) are based primarily on echo sounder basins has increased dramatically over the past few and side-scan sonar surveying. Technology in this decades in response to interest in the global tectonic field has seen major advances over the past two processes which control their long-term evolution decades, with the development of new ceramic ma and the regional and local sedimentary and tectonic terials to provide more efficient and powerful trans ducers, the increasing use of digital data processing processes which shape them, as well as more practi cal questions such as the nature and extent of off techniques to improve the quality of the signal from shore mineral resources, problems of waste disposal the sea floor, and the introduction of new design at sea and the response of sea level to global climatic concepts to provide higher resolution records."

This volume is a compendium of papers on the subject, as noted in the book title, of modeling and mapping. They were presented at the 25th Anniversary meeting of the International Association for Mathematical Geology (IAMG) at Praha (Prague), Czech Republic in October of 1993. The Association, founded at the International Geological Congress (IGC) in Prague in 1968, returned to its origins for its Silver Anniversary celebration. All in all 146 papers by 276 authors were offered for the 165 attendees at the 3-day meeting convened in the Hotel Krystal. It was a time for remembrance and for future prognostication. The selected papers in Geologic Modeling and Mapping comprise a broad range of powerful techniques used nowadays in the earth sciences. Modeling stands for reconstruction of geological features, such as subsurface structure, in space and time, as well as for simulation of geological processes both providing scenarios of geologic events and how these events might have occurred. Mapping stands for spatial analysis of data, a topic that always has been an extremely important part of the earth sciences. Because both modeling and mapping are used widely in conjunction, the book title should reflect the close relation of the subjects rather than a division. Here, we bring together a collection of papers that hopefully contribute to the growing amount of knowledge on these techniques.

Gorda Ridge presents a primarily technical summary of recent advances in seafloor research related to mineral exploration of the only seafloor spreading center within the United States' Exclusive Economic Zone (EEZ). Spreading centers are known to be the locus of hydrothermal activity and to host mineral deposits of hydrothermal origin. The book includes sections on the results of mineral exploration on Gorda Ridge, the newest technologies for mineral exploration and sampling on the seafloor, and the evolving field of hydrothermal vent biology and ecology. What makes the book unique is that it is: 1) a site book, 2) a truly multidisciplinary summation of the state of the art in complementary areas of deep ocean geology and biology, and 3) a marker in the evolution of federal-state relations concerning ocean development.

This book is the published record of the papers presented at a conference of the Norwegian Petroleum Society (NPF) held in Bergen, Norway, on 3-5 October, 1988. The conference was initially proposed and promoted by the Geology and Geophysics Advisory Committee of the Norwegian Petroleum Society consisting of: A. M. Spencer (Chairman), M. Brink,J. D. Collinson, S. Hanslien, D. M. D.James, T. B. Lund, K. Messel, E. Ormaasen and G. Saeland. The programme and more detailed planning of the conference was carried out by a programme committee consisting of: J. D. Collinson (Chairman), O. Eldholm, E. Holter, D. M. D.James, H. Tykoezinski, D. Worsley and S. M. Aasheim. There were 245 participants at the meeting and 36 papers were presented as talks with a further 9 presented as posters. These proceedings are representative of the range of topics covered. The meeting was characterized by a high level of discussion which has influenced several authors in the final preparation of their written papers. These proceedings have been edi ted on behalf of the Norwegian Petroleum Society by J. D. Collinson with help from H. Tykoezinski. The editor and the organizing committee wish to thank all the referees who reviewed papers and all the authors who responded so fully and promptly to their comments. The NPF is most grateful to the University of Bergen for making available their facilities for the conference.

Trans-boundary water resources are often a cause of conflict among riparian entities. Increasing demand for water resources and deterioration of existing water sources underscore the need to resolve conflicts over the allocation of consumption and pollution rights among conflicting uses and users. Because economic growth of the entities that share a water resource depends on sustainability of the resource, water has great potential as a basis for cooperation among political entities. However, enforcement of cooperation particularly in international settings is limited. Thus, parties sharing a water resource will form and remain in a cooperating coalition only when economic incentives for each can be identified. This book offers an economic approach to resolution of conflicts by identifying economic mechanisms that encourage sustainable cooperation. The book includes discussions on international, interstate, and intrastate disputes regarding both water quantity and water quality issues. It presents mechanisms for facilitating cooperation among users from agricultural, industrial, domestic, and environmental sectors.It considers the experience and potential in many regions around the world including Australia (the Muray-Darling Basin), Latin America (Chile), the Middle East (Israel and the Palestinian Authority), the U.S. (California, Florida's Everglades, Hawaii, and the Chesapeake Bay), and Africa (South Africa, Lesotho). Part I of the book discusses international experience in forming water coalitions and offers an illustrative model of water quality coalitions. It emphasizes the dependence of sustainability of international agreements on the practical ability to create incentives through economic mechanisms and political linkages that overcome the problem of limited enforcement due to sovereignty claims. Part II of the book discusses management of intrastate U.S. water resources involving competing local jurisdictions or user groups and the U.S. and Australian attempts to facilitate state management of interstate water resources through federal cooperation. Part III of the book explores the expanding scope of trans-boundary water resource issues that contribute to complexity of conflict beyond traditional interests such as allocation and navigation rights.In particular, it analyzes the economic implications of nutrient, land, and airshed management in an environment where the interaction of trans-boundary water resources with the ecological system is considered. Trans-boundary water usage and infrastructure are discussed in the context of privatization and political uncertainty. Part IV of the book examines economic solutions to trans-boundary water allocation including water markets, tradable water permits, contractual arrangements, and coordinated management. The interaction between ground and surface water and the interaction between desalinated, recycled, and fresh water is analyzed in the context of optimal water allocation. The book concludes with a critical discussion of the role and potential of the economics profession in contributing to conflict resolution and management of trans-boundary water resources. The strengths and weaknesses of economic analysis are discussed with special consideration of the modern tools of bargaining theory and game theory that go beyond economic efficiency in considering political realities.

The history of gold begins in antiquity. Bits of gold were found in Spanish caves that were used by Paleolithic people around 40,000 B.C. Gold is the "child of Zeus," wrote the Greek poet Pindar. The Romans called the yellow metal aurum ("shining dawn"). Gold is the first element and first metal mentioned in the Bible, where it appears in more than 400 references. This book provides the most thorough and up-to-date information available on the extraction of gold from its ores, starting with the miner alogy of gold ores and ending with details of refining. Each chapter con cludes with a list of references including full publication information for all works cited. Sources preceded by an asterisk (*) are especially recom mended for more in-depth study. Nine appendices, helpful to both students and operators, complement the text. I have made every attempt to keep abreast of recent technical literature on the extraction of gold. Original publications through the spring of 1989 have been reviewed and cited where appropriate. This book is intended as a reference for operators, managers, and designers of gold mills and for professional prospectors. It is also designed as a textbook for extractive metallurgy courses. I am indebted to the Library of Engineering Societies in New York, which was the main source of the references in the book. The assistance of my son, Panos, in typing the manuscript is gratefully acknowledged."

Identificationof rock-forming minerals in thin section is a key skill needed by all earth science students and practising geologists. This translation of the completely revised and updated German second edition (by Leonore Hoke, Institute of Geological and Nuclear Sciences, New Zealand) provides a comprehensive guide to identifying 140 of the most important rock-forming mineral species. The book is divided into three main parts. Part A is a practical guide to the fundamentals of crystal optics, polarization microscopy and the practical use of microscopes. Part B gives a detailed description of the characteristic optical features, special features, and the paragenesis of the most common rock-forming minerals. This well-illustrated part is divided into opaque minerals, isotropic, uniaxial and optical biaxial mineral groups. Part C contains identification tables for the minerals and diagrams showing the international classification of magmatic rocks, as well as a colour plate section showing crystal forms of minerals. The book will provide an invaluable guide to all undergraduate earth scientists, as well as to professional geologists requiring an overview of mineral identification in thin section.

The first North Sea Oil and Gas Reservoirs Conference was held in Trondheim in 1985 as part of the Norwegian Institute of Technology's 75th anniversary celebrations. Favourable reactions from the delegates prompted the Committee to re-run the event some three and a half years later, and it is now intended that the Confe rence be held on a regular basis as long as there is a demand for this type of gathering. The objectives of the 1989 Conference, which were broadly similar to those of the previous one, were: (a) to bring together those engaged in various geoscientific and reservoir engineering aspects of North Sea Oil and gas reservoirs in one forum; (b) to demonstrate wherever poSsible the interdependence of the various disciplines and specializations; (c) to promote innovative, synergistic approaches to research and development programmes aimed at North Sea conditions; and (d) to reflect current trends in the reservoir sciences. Naturally there was no place for specialist parallel sessions in a Conference aimed at encouraging interdisciplinary integration and awareness."

Traditional notions of security are premised on the primacy of state security. In relation to energy security, traditional policy thinking has focused on ensuring supply without much emphasis on socioeconomic and environmental impacts. Non-traditional security (NTS) scholars argue that threats to human security have become increasingly prominent since the end of the Cold War, and that it is thus critical to adopt a holistic and multidisciplinary approach in addressing rising energy needs. This volume represents the perspectives of scholars from across Asia, looking at diverse aspects of energy security through a non-traditional security lens. The issues covered include environmental and socioeconomic impacts, the role of the market, the role of civil society, energy sustainability and policy trends in the ASEAN region.

TECTONlCS AND PHYSICS Geology, although rooted in the laws of physics, rarely has been taught in a manner designed to stress the relations between the laws and theorems of physics and the postulates of geology. The same is true of geophysics, whose specialties (seismology, gravimetIy, magnetics, magnetotellurics) deal only with the laws that govern them, and not with those that govern geology's postulates. The branch of geology and geophysics called tectonophysics is not a formalized discipline or subdiscipline, and, therefore, has no formal laws or theorems of its own. Although many recent books claim to be textbooks in tectonophysics, they are not; they are books designed to explain one hypothesis, just as the present book is designed to explain one hypothesis. The textbook that comes closest to being a textbook of tectonophysics is Peter 1. Wyllie's (1971) book, The Dynamic Earth. Teachers, students, and practitioners of geology since the very beginning of earth science teaching have avoided the development of a rigorous (but not rigid) scientific approach to tectonics, largely because we earth scientists have not fully understood the origin of the features with which we are dealing. This fact is not at all surprising when one considers that the database for hypotheses and theories of tectonics, particularly before 1960, has been limited to a small part of the exposed land area on the Earth's surface.