Stirring up understanding of the Earth’s mantle

Scientists from the University of Leicester have a completely new understanding of the movement of the Earth’s mantle.

The new findings suggest that the mantle is actually divided into two different domains that mix only within themselves, contrary to popular belief.

Dr Tiffany Barry, who led the study published in Scientific Reports, said: “This new research overturns our understanding of how the inside of the Earth convects and stirs, and how it is divided up, and for the first time explains observations that were first noted in the late 1980s” 

The researchers believe that one of these domains is found under the Pacific Ocean – with the other existing outside it. What they discovered suggests that upper mantle material flows to lower parts of the mantle when it reaches a subduction zone – where one tectonic plate descends beneath another one. The descending material acts as a barrier, preventing upper material mixing and keeping the two domains apart.

“We have found that when mantle material reaches the bottom of the mantle, at the outer core, it does not spread out and go anywhere around the core, but instead returns to the same hemisphere of the globe from where it came,” explained Dr Barry.

The scientists combined spherical numerical computer models with the most up-to-date information of how the plates have moved over the last 200 million years. These included ‘mathematical’ particles placed at different lengths of the modelled mantle. Having tracked where these particles flowed, the researchers then examined chemical isotope evidence from past ocean basins.

Dr Barry said: “I’m incredibly excited by this work; it has been a research question I’ve been pondering for nearly two decades. It feels like a real privilege to have been able to piece together a robust and convincing model that can explain the feature of the chemical differences in ocean floor crust.”