(Geological Science) the study of the fossil magnetism in rocks, used to determine the past configurations of the continents and to investigate the past shape and magnitude of the earth's magnetic field studies of terrestrial lavas that Earth's magnetic field, which is created by the circulation of core materials, had reversed polarity frequently and regularly in the past at intervals of about half a million years, with each reversal probably taking only a few thousand years.
Comparacion entre las direcciones de anisotropia de la susceptibilidad magnetica (ASM) y la lineacion de estiramiento estructural en las peridotitas de Ronda: hacia un metodo identificador de lineaciones en ausencia de marcadores en rocas ultramaficas pole determinations on one hand, and mapped geological relationships and latitudinal interpretations of paleontology on the other, concerning what did or did not happen in the Canadian Cordilleran orogen as it reached a mature stage of its development in Late Cretaceous time.
More precise data and calculations in recent years have substantiated Gauss' conclusion that the "main" geomagnetic field is internal in origin and not from outside the earth.
Could the source of geomagnetic field be charges on the surface of the rotating earth?
His free decay theory is based exclusively on the available direct measurements of the intensity of the earth's field as a function of time (see Figure 8 in PALEOMAGNETISM I).
Mc Donald (1967), Akridge (1980), and Barnes (1971, 1972, 1973a, 1973b, 1975, 1981) have made statistical analyses of the laboratory intensity data which was collected between 18.Could the earth's field be due to ferromagnetism frozen into the rocks of the earth?The temperature gradient observed in the crust is about 30C/km.In addition, recent Magsat satellite data obtained in 19 has been analyzed (Wilford 1980).All of these studies conclude that the intensity of the earth's magnetic field has been decreasing during this period of time.Stacey (1969) and Jacobs (1963) both make estimates of the necessary time for the earth's magnetic field to decay exponentially to 1/e (37%) of its original value and arrive at times of 10 years respectively.The free decay theory has been favored by several creationist groups since it seems to imply a short age for the earth.These theories might best be referred to as the "free decay" model and the "regenerative dynamo" or "dynamo" model. Barnes Free Decay Model The free decay theory assumes that the motion of the charges in the core is simple circular motion around the magnetic polar axis of the earth.In addition it is generally assumed that the energy of the "original" electric currents is being continually dissipated away as heat in the conductor and that none is being supplied to take its place.Perhaps the leading spokesman for this view is Thomas G.Barnes, of the University of El Paso, Texas, who in 1971 wrote an article under the title "Decay of the Earth's Magnetic Moment and the Geochronological Implications," thus launching a new creationist method of dating the age of the earth based on the decay of its magnetic field.