Piles or plumes? Investigating the Earth’s core-mantle boundary with diffracted seismic waves

Supervisor: Dr Andy Nowacki

Department: School of Earth and Environment, University of Leeds


The core-mantle boundary—about 3000 km below the Earth’s surface—is home to some of the most enigmatic structures in the Earth.  Large, slow regions of material are thought to be either dense piles of material accumulated over billions of years, or perhaps instead clusters of buoyant thermal plumes.  Either way, these features affect the magnetic field, hotspot locations, long-term mantle convection and hence even the climate.

The uncertainty about whether these features are plumes or piles can be addressed by finding out if they are chemically distinct from their surroundings.  One way to constrain this is by comparing the speeds and propagation directions of P and S waves which travel through them.  The project aims to measure these using seismic array analysis of Pdiff and Sdiff—waves which diffract along the core and are hence extremely sensitive to lowermost mantle features.

You will make new measurements of the speed of Pdiff and Sdiff using our new automatic measurement procedures, gathering unexamined data from publicly-accessible databases of seismic data.  You will then analyse your results to determine if there are trends or correlations between the data and existing models of the mantle.  If time allows, you may also try to constrain the nature of the features causing your observations, and thereby for the first time use Pdiff and Sdiff data in this way to try and decide if the lowermost mantle hosts piles, plumes—or maybe both at once.

This project will help you develop data analysis, programming and algorithmic skills as well as a deeper understanding of seismological and deep Earth dynamics theory.  It would suit someone interested in the quantitative study of natural systems who is willing to grow or use their computing skills; geophysical or geological knowledge is not required.  You will work closely with Andy Nowacki and Jamie Ward (School of Earth and Environment, University of Leeds) in the Deep Earth Research Group and be a full member of the team alongside other project students, research postgraduates, postdoctoral researchers and members of academic staff.