Encyclopedia of Geomagnetism and Paleomagnetism

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This entirely new Encyclopedia of Geomagnetism and Paleomagnetism is an up-to-date synthesis of the most basic concepts of Paleomagnetism and Geomagnetism. The volume will be of interest to undergraduate and first and second year graduate students and also non-specialists such as Geologists, Engineers, Biologists, Physicists, Mathematicians, who need to consult the book to find the most basic concepts of Paleomagnetism and Geomagnetism in one compendium. To make the book as accessible as possible to students and non-specialists, the mathematics has been kept to a minimum.

Geomagnetism is the study of the Earth's magnetic field, which is unseen but all about us, and affects much of our lives. It is the oldest Earth science, its importance for navigation giving it the highest priority from the 16th to 18th centuries. By the late 19th century geomagnetism was being used to prospect for metal ores and minerals and, together with modern methods involving electromagnetic induction in the Earth, is a major tool in the exploration for oil as well as minerals.


Paleomagnetism, the determination of the magnetic field at the time of formation of rocks and archeological artefacts, was developed at the turn of the 20th century and almost immediately led to the discovery that the magnetic field had experienced large changes in the distant past, including complete reversals of polarity. Careful analysis and dating of many rock samples and in situ over decades led finally to a timescale for these reversals which is used for geological dating: geomagnetism now provides most of the quantitative information available on the movement of tectonic plates. There were long periods in the past when there were no reversals at all, and many times the field attempts to reverse without succeeding, the poles flipping part way briefly before returning. The geomagnetic field changes rapidly yet is astonishingly long lived, the compass direction changes markedly during a single lifetime yet the field is older than life itself.


Economic applications include aeromagnetic and satellite surveys in prospecting for minerals and hydrocarbons; dating and stratigraphy of sediments for investigations into climate and environmental changes; electromagnetic induction studies of electrical conductivity beneath land and ocean; and the traditional uses in navigation.


The magnetic field originates in the Earth's liquid iron core by a dynamo process. Fluid motion, driven by heat escaping from the interior and light elements rising up through the core, induces electric currents that, under the organising influence of the Earth's rotation, constitute the observed dipolar magnetic field. Understanding this process is one of the greatest challenges left to classical Physics, and current research combines ambitious experiments using liquid metals with the theory of magnetohydrodynamics and very large scale numerical computations - similar to but significantly more complicated than those used to forecast the weather.