In a study published by the journal of tectonophysics researchers describe how the ocean floor sinks in to our planets mantle over millions of years inciting a magnetic pole shift by cooling down the core and causing it to flow more rapidly.
They’ve examined the degree of sinking by conducting global plate reconstruction at the university of sydney – comparing that with evidence of magnetic field reversal in volcanic and sedimentary stone.
“When we were able to compare them, we found that the two records of subduction (sinking) and magnetic reversal rate do appear to be correlated after allowing for a time delay of 120-130 million years for the slabs of ocean floor to go from the surface to a sufficient depth in the mantle where they can cool the core.
“We do not know for sure that the correlation is causal but it does seem to fit with our understanding of how the crust, mantle and core should all be interacting and this value of 120-130 million could provide a really useful observational constraint on how quickly slabs of ancient sea floor can fall through the mantle and affect flow currents within it and in the underlying core.”
Professor Biggin heads up the University’s Determining Earth Evolution from Palaeomagnetism (DEEP) research group.
The amount of time between each subsequent pole shift has sped up over the course of history. During our current time period the poles shift roughly once every 250 000 years whereas one hundred million years ago they would stay the same for 40 million years.
“Based on numerical dynamo simulations and first-order mantle dynamical arguments, it is expected that some time-lagged, positive correlation exists between the global flux of subducting lithosphere and temporal variations in the geomagnetic reversal rate.”
Cover Image: Kay Lancaster, University of Liverpool