EarthRef.org Reference Database (ERR) -- Holt et al. 1996

A volcanic record of geomagnetic field inclination for the past similar to 400 kyr at Hilo, Hawaii, has been obtained from the 941.5 m of core recovered by the Hawaii Scientific Drilling Project. The analysis of 195 lava hows reveals six instances of near-zero inclination and two instances of fully negative inclination (reverse polarity) within an otherwise normal-polarity core. In particular, flow unit 23 (similar to 178 m depth) records a horizontal inclination and may be associated with the Laschamp event; flow units 40 and 42 (similar to 260 m depth) record negative inclinations and are close in age to the Flake event; and flow unit 55 (similar to 320 m depth) records a negative inclination with a relative declination change of similar to 75 degrees with respect to the overlying flow and is probably the Jamaica/Biwa I/Pringle Falls event. The five instances of shallow inclination found below 400 m depth appear to have resulted from long-term secular variation as they art: part of inclination swings between similar to 0 degrees and similar to 60 degrees with a periodicity of similar to 10-50 kyr. In contrast, the inclination shifts at similar to 178 m and similar to 320 m depths significantly deviate from long-term trends, suggesting the existence of at least two independent processes producing time variations of the geomagnetic field. The secular variation has a mean of 30.9 degrees (alpha(95) = 2.27 degrees), which is significantly shallower than the expected dipole mean of 36 degrees. The dispersion (sigma = 12.5 degrees) agrees with global paleosecular variation data for 0-5 Ma and secular variation models.