The first global map of magnetic peculiarities - or anomalies - on Earth has been assembled by an international team of researchers. Magnetic anomalies are caused by differences in the magnetisation of the rocks in the Earth's crust. Many years of negotiation were required to obtain confidential data from governments and institutes. Scientists hope to use the map to learn more about the geological composition of our planet. The World Digital Magnetic Anomaly Map (WDMAM) is available through the Commission for the Geological Map of the World. The global map shows the variation in strength of the magnetic field after the Earth's dipole field has been removed. After removal of the dipole field, the remaining variations in the field (few hundreds of nT) are due to changes in the magnetic properties of the crustal rocks.
Hot colours (reds) indicate high values; cold colours (blues) indicate low or negative values. As well as revealing ore deposits, magnetic anomalies can also show areas of ground water and sea weakness zones. It is a useful tool for geologists and geophysics, as well as a teaching resource. The information can be viewed as a flat, two-dimensional map or rendered in 3D on a virtual globe. This magnetic data has been gathered by Champ, a German and Russian-built satellite that has been in orbit since 2001. Now coming to the end of its life, it has charted the entire globe. With the publication of the first edition of the map, a second edition is under way. The upcoming Swarm magnetic field satellites, to be flown by the European Space Agency (Esa), will also help build new detail into the map.More information:
http://news.bbc.co.uk/1/hi/sci/tech/6982485.stm