Nineteen new heat flow measurements made across deformed oceanic lithosphere in the Central Indian Ocean, and previously published data show that heat flow is significantly higher than predicted by models for cooling oceanic lithosphere over much of the region. Many of the temperature-depth profiles are nonlinear. Upward convection of water is the most likely explanation for the curvature of the temperature profiles, since other possible causes, including variations in bottom water temperatures, conductivity changes with depth in the sediments, and experimental error, can be eliminated. This interpretation requires water velocities of the order of 7¿10-8 m/s, which is unusual because the lithosphere is relatively old (72-82 m.y.) and a thick sedimentary cover (1-2.5 km) is present. These observations suggest that the processes causing deformation of the plate have increased the heat flux through the sediment-water interface. We infer that extra heat is being generated at shallow depths (perhaps less than 35 km) in the plate, although the specific mechanism by which deformational energy is converted into heat is difficult to determine.