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The University of Southampton
Ocean and Earth Science, National Oceanography Centre Southampton

Research project: Passive Imaging of the Lithosphere-Asthenosphere Boundary (PI-LAB)

Currently Active: 

Plate tectonics has been a fundamental tenet of Earth Science for nearly 50 years, but questions remain, such as where is the base of the plate and what makes a plate, “plate-like?”

Schematic of potential mechanisms that define the oceanic lithosphere, from the mid-ocean ridge to 40 My old seafloor.
Figure 1


A better understanding of the transition from the rigid lithospheric plate to the weaker mantle beneath has implications for the driving forces of plate tectonics and mantle dynamics. Ocean lithosphere is the ideal place to study the plate; a thermal plate is predicted to increasing in thickness with age, with a gradual transition at its base. Whereas, a compositional plate might be uniformly thick, ~60 km, with sharp base. If melt weakens the asthenosphere, it may also sharpen the LAB transition. These differences can be mapped using geophysical measurements.

Proposed seismic and MT deployment plan, from the mid-Atlantic Ridge (MAR) to 40 My old seafloor.
Figure 2

Key Objectives

  • Image age-depth dependence of LAB systematically from 0 – 40 My old seafloor with MT & seismic at wide range of resolutions
  • Constrain sharpness of LAB transition
  • Constrain 3D isotropic and anisotropic seismic velocity structure
  • Jointly invert MT & seismic data
  • Perform full-waveform modeling
  • Compare and contrast with global constraints
  • Integrate with experiments & geodynamics
  • Determine what makes a plate, “plate-like”


  • Passive seismic: 30 broad band ocean bottom seismometers (OBS, red triangles)*
  • Active seismic (AS): reflection & refraction (dashed)**
  • 20 MT (Xs and dashed)*,** 

Key Contacts

Dr Nicholas Harmon

Dr Kate Rychert


Prof. Satish Singh (IPGP)
Prof. M. Kendall (Bristol)
Dr Ingo Grevemeyer (Geomar)
Prof. Steve Constable (Scripps)
Dr Kerry Key (Scripps)

PhDs and Other Opportunities


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