Evolution of oceanic lithosphere and implications for geodynamics: A comparison of the northern Pacific and Indian Ocean

How the oceanic lithosphere evolves with time (t) is the subject of significant debate. This problem relates the cooling of the overlying rigid plate to interactions with the underlying convecting mantle. Better understanding geodynamics is key to this problem, but also has significant practical implications (e.g., where will oil form). Heat flow (q) and bathymetry (z) are observable surface constraints while seismic tomography is a powerful tool to estimate temperature (T) at depth within the mantle. Based on the sea floor bathymetry beneath old oceans it is clear that the lithosphere does not simply cool as a conductive half space. However, none of the existing models can satisfactorily reconcile all the observations.

An important incompatibility is that almost all seismic tomography models indicate a relationship between the age of the sea floor and the seismic velocity at depths below the modelled base of the plate, i.e., within the asthenosphere (e.g. 125-150km). The role these anomalies play on subsidence depends strongly on the viscosity difference between the rigid plate, and the underlying fluid. This PhD project will use data available online through the Incorporated Research Institutions for Seismology (IRIS), to produce new surface wave tomography models beneath the northern Pacific and the Indian Ocean. The models will be combined with bathymetry and heat flow data to provide new insights on asthenospheric structure and viscosity, which also has important implications for understanding basin development on the margins of the oceans.

We are an equal opportunities employer and particularly welcome applications for Ph.D. places from women, minority ethnic and other under-represented groups.