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WELCOME TO THE GEOSCIENCES RESEARCH DIVISION | ||
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Long term variations in geomagnetic intensity
(figure from Tauxe and Staudigel, Geochem., Geophys., Geosyst., 5, Q02H06, doi:10.1029/2003GC000635, 2004. )We know a few things about the geomagnetic field:  The present dipole moment is about 80 ZAm^2. [``Z' stands for Zetta (10^21)]. (dashed line in above diagram. We know that the frequency of reversals has changed profoundly through time from periods of frequent reversals (as for the last 50 million years) to periods of no reversals for some 40 or more million years (as in the mid-Cretaceous [yellow region to left] and the Permian). We know that when the field reverses, its strength drops to extremely low values. We know the field has dropped from extremely high values to the present field precipitously and is continuing to drop rapidly. Is the field heading for reversal? The case against it: The present field is nearly twice the long-term average (Selkin and Tauxe, Phil. Trans. Roy. Soc., 358, 869-1223, 2000. Field intensty since the last reversal has undergone many oscillations very few of which (if any) were associated with a reversal (see below).  The present field is approximately equal to the field during the mid-Cretaceous (see top figure) when it didn't reverse for 40 million years. Related publications (last 5 years): Juarez, M.T., Tauxe, L., Gee, J., and Pick, T., The intensity of the Earth's magnetic field over the past 160 million years, Nature, 394, 878-881, 1998.[reprint] Juarez, M.T. and Tauxe, L., The intensity of the time average geomagnetic field: the last 5 Myr, Earth Planet. Sci. Lett., 175, 169-180, 2000.[reprint] Selkin, P. and Tauxe, L., Long term variations in geomagnetic field intensity, Phil. Trans. Roy. Soc., 358, 869-1223, 2000Selkin, P., Gee, J.S., L., Tauxe, Meurer, W.P., Newell, A.J., Earth Planet. Sci. Let., 183, 403-416, 2000.[reprint] Bowles, J., Gee, J., Hildebrand, J., Tauxe, L., Archeomagnetic intensity results from California and Ecuador: evaluation of regional data, Earth Planet. Sci. Lett., 203, 967-981, 2002.[reprint] Tauxe, L., Love, J.J., Paleointensity in HSDP2: results from submarine basaltic glass, G-cubed, DOI 10.1029/2001GC000276, 2003[reprint] Bowles, J., Tauxe, L., Gee, J., McMillan, D., Cande, S., The source of tiny wiggles in Chron C5: A comparison of sedimentary relative intensity and marine magnetic anomalies, Geochem., Geophys., Geosyst., Vol. 4, No. 6, doi:10.1029/2002GC000489. 2003,[reprint] Tauxe, L. and Staudigel, H., Strength of the geomagnetic field in the Cretaceous Normal Superchron: New data from submarine basaltic glass of the Troodos Ophiolite, Geochem., Geophys., Geosyst., 5, Q02H06, doi:10.1029/2003GC000635, 2004. [reprint] Yu, Y., Tauxe, L., Genevey, A., Towards an optimal geomagnetic field intensity determination technique, Geochem., Geophys., Geosyst., 5, Q02H07, 10.1029/2003GC000630, 2004. [reprint] Recent and ongoing research projects: 1. A paleointensity record from the ocean crust 2. Mapping sea surface magnetic anomalies 3. Characterizing the time-averaged magnetic field 4. Long term variations in geomagnetic intensity 5. Magnetization of meteorites and lunar samples 6. Applications of magnetic data to fabric development in cumulates |
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