Thermochemical anomalies in the Earth’s lowermost mantle

This project is available from the academic year 2020/21 onwards.

Theme: Solid Earth Dynamics

Primary Supervisor:

Saswata Hier-Majumder

Department of Earth Sciences, RHUL

Saswata Hier-Majumder's Profile Picture

Secondary Supervisor:

Carolina Lithgow-Bertelloni

Earth Sciences, UCL

Carolina Lithgow-Bertelloni's Profile Picture

Project Description:

The base of the Earth’s mantle is marked by a patchwork of seismically anomalous structures named UltraLow Velocity Zones (ULVZs), most commonly observed along the edges of two larger antipodal structures, termed Large Low Shear Velocity Provinces (LLSVPs).

The ULVZs are typically 8 to 10% denser than the surrounding mantle and are marked by up to 30% and 10% reductions in shear and compressional wave speeds, respectively. Narrow, elongated ULVZs can span up to several hundreds of kilometers in length while reaching only a few tens of kilometers of height above the CMB. The larger LLSVPs, characterized by up to 3% reduction in shear wave speed, are dynamic and likely chemically distinct structures.

Two key unresolved questions regarding ULVZs are their internal structure, and the ability to retain a distinct chemical signature over geological time periods. This project will focus on using high performance computational tools to study the melt migration and storage within the ULVZs, the resulting seismic signature, and the interaction between ULVZs and flow in the ambient mantle. The work will be carried out in collaboration with the geodynamics and mineral physics group at the University College of London.

Policy Impact of Research:

The research in this project identifies some fundamental problems in the deep interior of the Earth using a number of novel tools. The outcome will lead to high impact articles in top peer-reviewed journals and conference presentations.


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