Michael Clark

PhD thesis

Mapping Small-Scale Heterogeneity in the Lowermost Mantle

Nearly 2,900 kilometres beneath our feet, the Earth’s rocky mantle meets its liquid outer core. This boundary is one of the most mysterious parts of our planet, and contains unusual regions where seismic waves slow down or scatter. My research uses waves from earthquakes to detect and map these hidden features, including Ultra-Low Velocity Zones (ULVZs), which may contain iron-rich material, partial melt or remnants of ancient tectonic plates. I also study small-scale variations in the deep mantle beneath volcanic hotspots such as Hawai‘i, where rising plumes may transport distinct material from close to the core–mantle boundary towards the surface. By understanding where these regions are, what they are made of and how they interact with the surrounding mantle, we can learn more about how material moves through Earth, how mantle plumes and volcanic hotspots form, and how the deep interior has evolved over billions of years.

Who or what inspired you to pursue your research interests?

Before coming to Cambridge, I completed an MSci in Earth and Planetary Science at Imperial College London, where I discovered a passion for research and seismology. For my Masters project, I analysed seismic data from NASA’s InSight mission—the first working seismometer sent to Mars—to study a region of the Martian crust that is rifting apart. From this, I was able to learn about ongoing processes occurring beneath the surface of a planet 225 million kilometres away from us! This experience revealed to me the power of seismology and inspired me to pursue a PhD exploring the Earth’s interior.