Pub. date: 2006 | Online Pub. Date: September 15, 2007 | DOI: 10.4135/9781412952453 | Print ISBN: 9780761930297 | Online ISBN: 9781412952453 | Publisher:SAGE Publications, Inc.About this encyclopedia
Christopher C. Matson
Paleomagnetism is both the fixed orientation of a rock's crystals based on the orientation and direction of the Earth's magnetic field at the time of the rock's formation and the study of such phenomena used as indicators of Earth's paleomagnetic history. The Earth's magnetic field orientation as a dipole is not fixed and is continuously changing by small increments. This leads to an effect known as polar wander. This continuing process is still active today and forces charts of the earth's magnetic field, known as isomagnetic maps, to be redrawn every 5 years. The phenomenon of polar wander has been used extensively in geology as an indicator of global position and the geologic age of iron-bearing rocks known as ferromagnetic rocks. Studying paleomagnetics has, in part, established the position and intensity of the Earth's magnetic pole over geologic time. Geologists use this new sagaciousness to determine aspects of global tectonic ...