Imaging the multi-scale landscape of the core-mantle boundary

Theme: Solid Earth Dynamics

Primary Supervisor:

Paula Koelemeijer

Earth Sciences, UCL

Paula Koelemeijer's Profile Picture

Secondary Supervisor:

Ana Ferreira

Earth Sciences, UCL

Ana Ferreira's Profile Picture

Project Description:

The core-mantle boundary (CMB), at nearly 3000 km depth, displays a landscape of hills and troughs induced by dynamic convection and density anomalies in the mantle. This topography affects the flow in the outer core and thus the behaviour of Earth’s magnetic field, while it also provides constraints on the chemical composition of the lowermost mantle. However, no consensus exists on the amplitude and pattern of CMB topography due to uneven sampling of seismic sources and receivers, the lack of high-resolution data and contamination from surrounding heterogeneous mantle structure.

This PhD project will use both short-period and long-period seismic data to investigate the complex landscape of the core-mantle boundary. Normal mode data will be used to study structures at long wavelengths, whereas observations of short-period body waves will provide information on the small-scale characteristics of CMB topography. The PhD student will collect and analyse different data and model their waveforms using 3D wave propagation codes. Combining insights from both data sets is crucial to obtain a consistent CMB topography model and to further our understanding of this enigmatic region inside the Earth.

Depending on the interests of the student, the focus can be more on the gathering and analysis of seismic data sets that are most sensitive to CMB topography, or more on the accurate modeling of wave propagation in the presence of CMB topography. This project is suited for students with strong quantitative skills, notably in mathematical analyses and programming. Interested students should not hesitate to get in touch.

Policy Impact of Research:

At the core-mantle boundary, dynamic processes occurring in the mantle (driving plate tectonics) and core (sustaining the magnetic field) interact – both vital for life on Earth. Improved images of this boundary thus provide critical insights into these dynamic processes, leading ultimately to better constraints on the history of our planet.

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