Shallow paleomagnetic directions from historic lava flows, Hawaii

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Abstract
A study designed to examine the basic theory of thermoremanent magnetization acquisition parallel to the earth's ambient magnetic field upon cooling and to evaluate intra‐flow variations of very young basalt flows has yielded some startling initial results. Two extensively sampled flows, the 1950 flow of Mauna Loa and the 1972 flow from Mauna Ulu, Kilauea, have been found to have paleomagnetic directions statistically different from the present geomagnetic field direction (PFD) in Hawaii. The 1950 flow shows very consistent, but shallow directions throughout the flow, with a mean inclination 6° shallower than the PFD. Directions from the 1972 flow vary from site to site both along the length of the unit and within vertical sections. Relative between site consistency is low, with all sites but one having paleomagnetic directions distinct from the PFD, however, the mean inclination for this flow, 33.4°, is only about 3° shallower than expected. The source of such anomalous behavior in the recording of ambient field directions is yet unknown, although several possible causes are examined.