Gravity and magnetic field

Bouguer Anomaly: The size of the Bouguer anomaly at a particular location is a measure of the mass deficit or mass excess in the underlying rocks. A mass deficit  exists where  the stratigraphic succession is composed of relatively light rocks; this yields a negative Bouguer anomaly. A mass excess exists where the stratigraphic succession is composed of relatively heavy rocks, this yields a positive anomaly.   

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Bouguer gravity anomaly _2009 _2010 _2010



Earth’s magnetic field: The anomaly of the vertical component of the earth’s magnetic field is an indication of the concentration of ferromagnetic minerals (predominantly  magnetite) in the earth’s crust. The anomalies are larger as the concentrations of these minerals are higher. The highest concentrations are found in igneous and metamorphic rocks. The concentrations are usually low in sedimentary rocks.

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Anomaly of the earth's magnetic field strengt _2009 _2010 _2010