Do Hotspots blow in the wind? Does the Earth roll about?
Channel: Paul Wessel
Date: 05/02/2020

Dr. Will Sager (University of Houston) gave a guest lecture via Skype in Fall 2008 for a graduate class on Advanced Plate Tectonics in SOEST, University of Hawaii at Manoa.  The students recorded the lecture and produced video podcasts of the event.  This is one of 8 such lectures from the course which was taught by Prof. Paul Wessel.

ABSTRACT:

"The Pacific plate is an excellent location to examine the hotspot reference frame because of its many linear seamount chains.  One may examine the motion of the plate relative to the hotspots and compare with the motion implied by seamount chains.  This requires better definition of the paleomagnetic apparent polar wander path (APWP) for the Pacific plate, which has been the object of recent studies.  The Pacific APWP shows an “backwards-J” shape that indicates the plate initially moved southward, during the Jurassic and Early Cretaceous, before turning around to move northward since.  The APWP shows two intriguing periods of non-uniform polar motion.  Between 94-80 Myr ago, the pole moved rapidly northward, an episode that has been attributed to true polar wander (TPW).  During the period of the Emperor Seamount chain formation, ~80-49 Ma, Pacific paleomagnetic poles show no motion.  This stillstand is the opposite of what would be expected from the apparent northward motion of the Pacific plate implied by the Emperor chain.  The paleomagnetic data imply that the plate had little or no northward motion and that the hotspot moved rapidly southward during the time of the Emperor chain formation.  From the trend of the Emperor chain, this finding also implies that the hotspot had a large component of westward drift.  Paleomagnetic data for 49 Myr and after are in good agreement with motion predicted by the hotspot, indicating that the prior rapid motion had an abrupt termination coincident with the Hawaiian-Emperor Bend.  Although true polar wander does not appear to be a satisfactory explanation for the Hawaiian-Emperor Bend, the apparent “zoom-stop” motion of the hotspot also stretches credulity."