My research focuses on the structure and mechanical behaviour of the Earth’s crust and upper mantle. I use seismology to construct images of the internal structure of the Earth which can then be used to test hypotheses of the Earth’s evolution and dynamics. Although my research has depended heavily on publicly-available seismic data, much of my work is based on data collected in my field experiments in Iceland, New Zealand, Hawaii, Greece, Turkey, Chile and much of the Middle East and central Asia. I combine my seismic results with advances in geochemistry, petrology, and mineral physics to relate the measured seismic wave speeds to temperature and composition. This has allowed me to produce thickness maps of the lithosphere, the cold boundary layer near the Earth’s surface which controls the Earth’s heat loss and the tectonics of the oceans and continents. These lithospheric maps show how extensive regions of thick lithosphere have controlled the geometry of continental deformation; they have also provided significant new insights on the formation and evolution of the continents.