Коллективная монография, опубликованная в США под эгидой Международного комитета по Проекту верхней мантии. В книге, написанной виднейшими специалистами различных стран (в том числе и СССР), суммированы новейшие данные и представления о строении, составе, физическом состоянии и развитии земной коры и верхней мантии с учетом результатов последних теоретических и экспериментальных исследований. Характер изложения в книге точный, доступный для специалистов других областей наук о Земле. Ряд идей, приводимых в книге, имеет остро дискуссионный характер.

Книга будет исключительно полезна для самых широких кругов советских геологов, геофизиков и геохимиков, как научных работников, так и практиков.

Представляемое учебное пособие составлено в соответствии с программой дисциплины "Геофизические методы поисков и разведки месторождений полезных ископаемых, геофизическая, интерпретация геофизических данных" (для специальности 0801 "Геологическая съемка, поиски и разведка месторождений полезных ископаемых") 

Интерпретация геофизических данных может быть качественной и количественной. При качественной интерпретации по графикам,-  разрезам, картам распределения соответствующею: параметров определяют примерное положение исследуемых объектов в геологическом разрезе, При количественной интерпретации определяют геометрические параметры искомых объектов (размеры, форму, глубину залегания) и физические свойства объектов ж вмещавдюс горных порол« Количественная интерпретация - это, в первую очередь, решение так называемых прямых и обратных задач. Под прямой задачей понимают нахождение элементов геофизического поля над известным геолого-физкческим разрезом. Прямая задача решается однозначно, т*еР  определенной заданной геолого-физической модели соответствует строго определенное (однозначное) распределение геофизического поля. Анализ графиков физических полей, полученных при решении прямой задачи, позволяет решать многие методические вопросы, которые возникают яри проектировании работ, в частности: выбирать оптимальную сеть наблюдений, планировать необходимую точность съемки, решать вопрос о сравнительной эффективности отдельных методов и др. <...>

Излагаются современные представления о методах геофизических исследований, происхождения, размерах, форме и составе геосфер, их взаимодействиях, движениях и геофизической роли.

Геофизику в разном объеме изучают студенты геологических, физических, географических и ряда других специальностей, применительно к каждой из которых обычно основное внимание уделяется какой-то одной оболочке Земли. Но для студентов гидрометеорологических специальностей (гидрология суши, метеорология, климатология, океанология, агрометеорология) недостаточно знать только одну геосферу—атмосферу, гидросферу или литосферу. Такое исключение определяется характером практической деятельности по анализу и прогнозу состояния водной и воздушной оболочек планеты и самой сущностью процессов. Нельзя понять, а тем более предвидеть ни один природный процесс в какой-либо одной геосфере, если его рассматривать изолированно, вне связи с процессами других оболочек Земли, без учета состояния всех геосфер. Поэтому в ходе подготовки гидрометеорологов разных специальностей детальное изучение ими свойств и процессов какой-либо одной оболочки Земли должно опираться на знание ими всех других взаимодействующих между собой геосфер.

Выпускаемая 4-м изданием книга включает в себя итоги важнейших, преимущественно отечественных исследований, а также наиболее существенных иностранных.

Новое содержание получила 3-я глава «Кинематика, динамика и расчет ветровых волн». В ней приведены результаты отечественных исследований, позволивших заложить физические основы расчета и прогноза элементов ветровых волн по заданной скорости ветра, времени его воздействия, расстоянию от наветренной границы шторма, заданной глубине моря — при заданной обеспеченности волн. В книгу включена глава «Магнитные и электрические явления в море». Эти явления представляют большой интерес как в теоретическом, так и в практическом отношении и требуют постановки все новых и новых исследований в океане и во внутренних морях. Переработаны и дополнены 5-я глава «О физических корнях климата и погоды», а также и другие главы.

Humanity has always been fascinated with the wandering stars in the sky, the planets. Ancient astrologists have observed and used the paths of the planets in the sky to time the seasons and to predict the future. Observations of the planets helped J. Kepler to formulate his laws of planetary motion and revolutionize the perception of the world. With the advent of the space age, the planets have been transferred from bright spots in the sky to worlds of their own right that can be explored, in part by using the in situ and remote-sensing tools of the geosciences. The terrestrial planets are of particular interest to the geoscientist because comparison with our own planet allows a better understanding of our home, the Earth. Venus offers an example of a runaway greenhouse that has resulted in what we would call a hellish place. With temperatures of around 450C and a corrosive atmosphere that is also optically nontransparent, Venus poses enormous difficulties to spacecraft exploration. Mars is a much friendlier planet to explore but a planet where greenhouse effects and atmospheric loss processes have resulted in a cold and dusty desert. But aside from considerations of the usefulness of space exploration in terms of understanding Earth, the interested mind can visit astounding and puzzling places. There is the dynamic atmosphere of Jupiter with a giant thunderstorm that has been raging for centuries. There is Saturn with its majestic rings and there are Uranus and Neptune wit complicated magnetic fields. These giant planets have moons that are similarly astounding. There is the

volcanic satellite of Jupiter, Io that surpasses the Earth, and any other terrestrial planet in volcanic activity and surface heat flow. This activity is powered by tides that twist the satellite such that its interior partially melts. A much smaller moon of Saturn, Enceladus, also has geysers that could be powered by tidal heating. Its volcanic activity releases water vapor not lava. There is another moon of Saturn, Titan, that hides its surface underneath a layer of photochemical smog in a thick nitrogen atmosphere and there are  moons of similar sizes that lack any comparable atmosphere. Miranda, satellite of Uranus, appears as if it has been ripped apart and reassembled. Triton, a satellite of Neptune, has geysers of nitrogen powered by solar irradiation. Magnetic field data suggest that icy moons orbiting the giant planets may have oceans underneath thick ice covers.These oceans can, at least in principle, harbor or have harbored life. Moreover, there are asteroids with moons and comets that may still hold the clues to how the solar system and life on Earth formed. This volume of the Treatise on Geophysics discusses fundamental aspects of the science of the planets. It is focused on geophysical properties of the Earth-like planets and moons, those bodies that consist largely of rock, iron, and water, and the processes occurring in their interiors and on their surfaces. But it goes further by discussing the giant planets and their satellites as well. The better part of the volume is dedicated to the interior structure and evolution of the terrestrial planets and to their physical properties such as gravity and magnetic fields, rotation and surface–atmosphere interactions. What is the planetological context of life?

Evolutionary science is for the most part based on observation and indirect inference. It is not experimental science, even though experiments can certainly play a role in our understanding of processes. We can never hope to have the resources to build our own planet and observe how it evolves; we cannot even hope (at least in the foreseeable future) to observe an ensemble of Earth-like planets elsewhere in the universe and at diverse stages of their evolution (though there is certainly much discussion about detection of such planets; e.g., Seager (2003)). There are two central ideas that govern our thinking about Earth and its history. One is ‘provenance’: the nature and origin of the material that went into making Earth. This is our cosmic heritage, one that we presumably share with neighboring terrestrial planets, and (to some uncertain extent) we share with the meteorites and the abundances of elements in the Sun. The other is ‘process’: Earth is an engine and its current structure is a consequence of those ongoing processes, expressed in the form it takes now. The most obvious and important of these processes is plate tectonics and the inextricably entwined process of mantle convection. However, this central evolutionary process cannot be separated from the nature of the atmosphere and ocean, the geochemical evolution of various parts of Earth expressed in the rock record, and life. Figure 1 shows conceptually the ideas of Earth evolution, expressed as a curve in some multidimensional space that is here simplified by focusing on two variables (‘this’ and ‘that’), the identities of which are not important. They could be physical variables such as temperature, or chemical variables (composition of a particular reservoir) or isotopic tracers. The figure intends to convey the idea that we have an initial condition, an evolutionary path, and a present state. The initial condition is dictated not only by provenance but also by the physics of the formation process. By analogy, we would say that the apples from an apple tree owemuch of their nature not only to the genetics of apples (the process of their formation) but also, to some extent, the soil and climate in which the tree grew.We are informed of this initial condition by astronomy, which tells us about how planets form in other solar systems, by geochemistry (a memory within Earth of thematerials and conditions of Earth formation), and by physical modeling: simulations and analysis of what may have occurred. Notably, we do not get information on the initial condition from geology since there are no rocks or landforms that date back to the earliest history of Earth. Geology, aided by geochemistry and geobiology, plays a central role informing us about Earth history. Though some geophysicists study evolution, nearly all geophysical techniques are directed toward understanding a snapshot of present Earth, or a very short period prior to present Earth, and it is only through modeling (e.g., of geological data) that the physical aspects of evolution are illuminated.

For as long as man has speculated about the interior of the Earth, it has been presumed that there exists a central core. Centuries before the rise of modern science, philosophers, and theologians had concluded that the Earth has a hot region at its center, with properties distinct from all other parts of the planet. For nearly as long a time it has been known that the Earth is also magnetic, but the cause of the Earth’s agnetism remained just as mysterious as the nature of the deep interior. Scientific inquiry about the core grew from early investigations of the properties of the geomagnetic field, which began during the era of global exploration. Although the ancient Chinese deserve the credit for discovering Earth’s magnetism, Gilbert (1600) was the first to demonstrate that the compass needle is controlled by a force originating within the Earth (Figure 1). He showed that the pattern of magnetic field lines on a uniformly magnetized sphere approximate the known directions of the compass needle over the Earth’s surface. Three hundred and fifty years later, Sidney Chapman characterized Gilbert’s demonstration as ‘‘the only successful experiment in the history of geomagnetism!’’ Later it was observed that Earth’s magnetic field changes slowly with time. In his famous explanation for this secular variation, Halley (1683, 1692) proposed that the geomagnetic field has its origin near the Earth’s center, in a region separated from the solid crust by a cavernous, fluidfilled shell. Halley (Figure 2) envisioned that both the crust and the central region or core rotate in the prograde sense, but the core spins slightly slower, causing the magnetic field to drift systematically westward as seen at the surface. Thus, two important and long-lasting concepts were born: the basic three-layer model of Earth’s interior (solid crust and mantle, liquid outer and solid inner core), and the association between the westward geomagnetic drift and westward motion of the fluid outer core with respect to other parts of the Earth system. Halley’s model implicitly assumed that the magnetic field originated in a solid inner core (Evans, 1988), akin to Gilbert’s uniformly magnetized sphere. Subsequently, it was shown that Halley’s model is at variance with the ferromagnetic properties of Earth materials, which lose their permanent magnetization at the Curie temperature at depths of a few tens of kilometers beneath the surface (see Chapter 5.06). However, by then the physical connection between magnetic fields and electric currents had been established, providing an alternative explanation for the geomagnetic field that relied on free electric currents rather than permanent magnetization.

Much of what we refer to as geology, or more accurately geological activity on Earth, is due to the simple act of our planet cooling to space. What allows this activity to persist over the lifetime of the solar system is that the major and most massive portion of the planet, namely the mantle, is so large, moves so slowly, and cools so gradually that it sets the pace of cooling for the whole Earth.

It has been known since the pioneering work of Joseph Barrell during the early part of the last century that the outermost layers of the Earth comprise a strong upper layer, the lithosphere, which overlies a weak lower layer, the asthenosphere. Barrell (1914a) argued that because river deltas such as the Niger and Nile lack a flanking topographic depression, they must be supported by the strength of the lithosphere. He used (Barrell, 1914b) Pratt isostatic gravity anomalies over North America as a proxy for the magnitude of the stress differences that could be supported by the lithosphere and showed, using the equations of Darwin (1882), that stresses increase and then decrease with depth, passing by transition into the weak underlying asthenosphere. Today, we distinguish the lithosphere from the asthenosphere not only on the basis of its strength, but its physical properties such as temperature, density, and seismic velocity structure. The lithosphere, for example, is generally associated with cooler temperatures, higher average densities, and higher average S-wave velocities than the asthenosphere. Plate tectonics is based on the assumption that the lithosphere is rigid on long timescales and is moving across the surface of the Earth with the plates. The positive density contrast between the lithosphere and the asthenosphere suggests, however, that the rigid layer may be gravitationally unstable. Indeed, oceanic lithosphere – after it is created at a mid-oceanic ridge – cools, subsides, and sinks into the underlying asthenosphere, for example, at a deep-sea trench–outer-rise system.Continental lithosphere may also be unstable. In rifts (e.g., East Africa) the lithosphere is regionally heated, thinned, and uplifted and only subsides locally below sea level. In collisional systems (e.g., Himalaya, Betics), however, continental lithosphere is thickened (Molnar et al., 1998) or is infiltrated by fluids released during metamorphic reactions (Le Pichon et al., 1997). Both processes may cause dense rocks of the lower crust to enter the eclogite stability field. As a result, the lower crust becomes denser than the underlying mantle, detaches, and, as at trenches, may sink into the underlying asthenosphere. Isostatic considerations, however, suggest that the crust – which comprises the uppermost part of the lithosphere – is buoyant and is in a state of flotation on the underlying mantle. Furthermore, flexure studies suggest that when it is subject to long-term geological loads such as volcanoes and sediment, the lithosphere, rather than behaving as a number of independent floating blocks, as local models of isostasy such as Airy and Pratt predict, responds by bending – in a similar manner as would an elastic plate that overlies an inviscid fluid substrate.

The Earth has its own magnetic field (the geomagnetic field), which is confined by the action of the solar wind into a volume called the magnetosphere (see Chapter 5.03). This field is not steady, but varies with time due partly to the interaction with the solar wind, but more importantly by its own physical processes. Direct observation of such changes has been carried out only in the last few centuries, but with indirect measurements we can understand the field behavior millions of years back in time. In this extended time frame, there is evidence that the polarity of the magnetic field reversed frequently, and that the magnetic dipole axis in very ancient times was significantly displaced from the present rotational axis (the North and South geographic Poles). It is of considerable interest how such knowledge was acquired over several centuries. We will take a brief tour of the historical events that provided important steps in formulating our understanding of the geomagnetic field. In doing so, we have to rely solely on the written records, which is the reason why only the European and Chinese histories are referred. There are many works on this topic; among them, the important ones are Mitchell (1932–46), Harradon (1943–45), Needham (1962), and Yamamoto (2003). The English translations of Chinese literature below were taken from Needham (1962). Chinese sentences given together with English were taken from the Japanese translation of this book (Hashimoto et al., 1977). When we talk about the earliest recognition of the magnetism of the Earth, we should be careful to discriminate two separate issues; that is, the attractive force exerted by a magnet on iron, and the north- (or south-) seeking property of the magnet. The former can be taken as the forerunner to the science of magnetism, while the latter is the basis for appreciation of the magnetic field associated with the Earth. Our main interest is in the geomagnetic field, but it is necessary to look into magnets first.