Turbulent water motions are important for the exchange of momentum, heat, nutrients, and suspended matter in the deep sea. The shape of the marine topography influences most water turbulence via breaking internal waves at critically sloping seafloors. In this paper with co-author Henk de Haas, the concept of critical slopes is revisited from a global internal wave turbulence viewpoint using seafloor topography and moored temperature sensor data. The potential robustness of the seafloor–internal wave interaction is discussed. Observations suggest that turbulence generation via internal wave breaking at 5±1.5% of all seafloors is sufficient to maintain ocean-density stratification. However most, >90%, turbulence contribution is found at supercritical, rather than the more limited critical, slopes measured at 1¢-scales that cover about 50% of seafloors at water depths < 2000 m. A reduction in elevation variance seems associated with seafloor-erosion by internal wave breaking, because the corresponding length-scale is equivalent to the internal wave excursion length.