Geomagnetics

In the geophysical scientific literature there is no lack in elementary textbooks where geomagnetism is treated together with other subjects like gravimetry seismics, seismology, electrical methods etc. There are even some, however few, books which are entirely devoted to subdisciplines of geomagnetism. Most of them are of high physical and mathematic standard. The various sub-disciplines of geomagnetism (main field theory, palaeomagnetism, rock magnetism, magnetic induction, magnetic anomalies) are commonly developed on the basis of the potential theory, Maxwell's equations or solid state physics. Only few authors try to complete their often quite theoretical deductions with practical examples. The authors of this volume try to fill in this gap in the case of applied geomagnetics, i.e. the interpretation of geomagnetic anomalies. Both authors have worked in this field during the last 30 years and have contributed a lot to the development of the method itself. They have now so to say "opened their files" for the scientific community to show what the reality of interpretation of magnetic anomalies really is. They selected various case histories from many places of the world (anomalies of basic and acid intrusions, ore deposits, basement rocks, thermal anomalies, even anomalies due to magnetised sediments) to show the general problems of their interpretation. The crucial unknown quantity in the interpretation of geomagnetic anomalies is ? and will always be ? the direction and intensity of the magnetisation of deep seated, i.e. not outcropping layers. Much effort has therefore been devoted to extract this information from the correlation between ground based, airborne and satellite magnetic measurements. Although the problem is far from being solved, some general constraints can be given for the magnetic properties of various crustal types.