Submarine sediment density flows ("turbidity currents") and rivers on land are volumetrically the most important processesfor moving sediment across our planet. However, submarine flows are more episodic and are typically more violent (withspeeds of up to 20m/s) than river floods. Moreover, a single submarine flow is capable of transporting ten times the annualsediment load from all of the world's rivers combined. Submarine flows are important because they produce many of theworld's most extensive and voluminous sedimentary deposits, both on the modern sea floor and in the ancient rock record,but also because they can break seafloor cables that now carry over 95% of global data traffic (that underpin our daily livesthrough the internet and financial markets). Ancient submarine flows created subsurface rock sequences that contain manyof our largest oil and gas reserves. Submarine flows carve canyons, which are deeper than the Grand Canyon, throughprocesses that are still poorly understood, and flows within canyons play a key role in supplying organic carbon andnutrients to benthic ecosystem (that include important diversity hotspots) in the deep sea.