It is widely known that the geomagnetic field shields our planet against highly energetic cosmic particles. The importance of the magnetic field for answering geological, tectonic or even archaeological questions is less known.
Where do large, very old meteorite craters exist like, for example, the one that might have led to the extinction of the dinosaurs? How did the continents move about the globe through geological times? How does the hidden subterranean structure of a volcano look like, i.e. how high is the danger of eruption" Where had towns and buildings of ancient civilizations been located, which have long since been destroyed?
The study of anomalies of the magnetic field of the Earth's crust and upper mantle can provide significant indications to answer such questions. Detailed global mapping of magnetic anomalies has only recently become possible by integrating huge amount of data from different platforms. Mioara Mandea of GeoForschungsZentrum Potsdam (GFZ) and Erwan Thebault of Institut de Physique du Globe de Paris (IPGP) have compiled an overview over the Earth's magnetic field and current research topics on magnetic anomalies in a booklet published in cooperation with UNESCO by the Commission for the Geological Map of the World (CGMW, Paris).
"This summarized state of knowledge is based on current observations, models and interpretations of the Earth's magnetic field and also makes clear that many aspects of the field will remain future topics of research. The Swarm satellite mission planned for 2010 will serve this purpose," says Professor Reinhard Hьttl, chair of the GFZ executive board.
The booklet also is a complement to the recently published World Digital Magnetic Anomaly Map. This is the first global compilation of all available information on magnetic anomalies, based on more than 50 years of data from aeromagnetic and marine surveys, on ground measurements, on high-quality, high-resolution satellite data, like CHAMP of GFZ, and supplemented by values derived from an ocean bottom anomaly model based on crustal ages. -Helmholtz Association of German Research Centres
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#1 Two different types of
Two different types of magnetic poles must be distinguished. There are the "magnetic poles" and the "geomagnetic poles". The magnetic poles are the two positions on the Earth's surface where the magnetic field is entirely vertical. Another way of saying this is that the inclination of the Earth's field is 90° at the North Magnetic Pole and -90° at the South Magnetic Pole. A typical compass that is allowed to swing only in the horizontal plane will point in random directions at either the South or North Magnetic Poles.