Paleomagnetism of Midway Atoll lavas and northward movement of the Pacific plate

Two deep drill holes through the reef limestones of Midway Atoll penetrated 120 m and 19 m of basaltic lavas that were dated by the KAr method at 18 my. Inclinations of natural remanent magnetization have been measured in 173 specimens cut from 57 core samples from 13 of the lava flows. The mean paleomagnetic inclination is27.6° ± 6.8°, corresponding to a paleolatitude of14.7° ± 4.2°. The present latitude of Midway is 28°, suggesting a northward component of motion of the Pacific plate of approximately 13° or 1400 km in the last 18 my. The paleolatitude of Midway is thus not significantly different from the present latitude (19°) of the active volcanic island of Hawaii. The paleomagnetic data from the Midway basalts thus support the hypothesis of Wilson and Morgan that volcanic heat sources are fixed with respect to the Earth's mantle below the asthenosphere and their apparent migration with time is due to plate motion.