Deep Landscapes

Dr Paula Koelemeijer will deliver the ESE Departmental Seminar on 29 October. Join us online (link tbc).

Deep in the Earth’s mantle, two large structures are present on top of the core. These structures, called large-low-velocity-provinces (LLVPs), or often just called “blobs”, influence large-scale dynamic processes in the mantle and core, including core convection and the thermal evolution of the Earth. Although these structures are consistently imaged amongst different seismic velocity models, it is still not clear what these structures are; how long have they been there, what material are they made out of, how do they interact with the mantle around them? To answer some of these questions, information on their density is crucial, which mostly involves the analysis of Earth’s free oscillations or normal modes. However, the sensitivity of normal modes to density is relatively small and there are trade-offs with the topography on the core-mantle boundary (CMB), which also remains poorly imaged.

Here, Dr Koelemeijer will review efforts from the last decades to constrain the nature of the LLVPs, focusing on density and CMB topography. Specifically, she will discuss how the spatial extent of any dense material may be restricted to smaller regions within the LLVPs. In addition, she will discuss our current knowledge of the large-scale CMB topography, which also holds clues as to what the LLVPs may be. Furthermore, Dr Koelemeijer will demonstrate that including CMB topography also reconciles recent density studies based on normal modes and Earth’s tides, while the presence of a dense layer is able to explain both data types. Together, these results point towards primarily thermal LLVPs with deep, spatially confined dense material present at their base.

About Paula Koelemeijer

I received both my BSc in Earth Sciences (2008) and MSc in Geophysics (2010) from Utrecht University. In the final year of my MSc I conducted a research project in Cambridge with Arwen Deuss and continued there for a PhD in seismology, which was awarded in 2014. I then held some personal fellowships, first moving to Switzerland as an ETH Zurich Postdoctoral Fellow (2014 – 2015), before being based in Oxford as a Junior Research Fellow at University College (2015 – 2018). In 2018, I was awarded a Royal Society University Research Fellowship, which I initially took up at UCL. In 2019, I transferred the fellowship to Royal Holloway to start the DEEPSCAPE seismology group there.