A River Beneath the Waves
Off the coast of Visakhapatnam, the continental shelf is scarred by a series of massive underwater canyons. These are not static relics; they are active conduits for sediment transported from the Indian subcontinent to the deep floor of the Bay of Bengal. The Godavari River, one of peninsular India's largest river systems, discharges enormous volumes of sediment into the bay. This material accumulates on the continental slope until it becomes unstable, triggering powerful underwater avalanches known as turbidity currents.
These currents are dense, sediment-laden flows that race down the steep-sided valleys, carving and shaping them over geological time. The process is similar to how rivers carve canyons on land, but it happens entirely beneath the ocean's surface. The Visakhapatnam canyons are part of a larger system, with some individual canyons measuring 50 to 70 kilometers in length and reaching depths of up to 2,500 meters—deeper than the Grand Canyon. Their walls can be nearly vertical, and they are the main way to move terrestrial sand and mud into the abyssal plain. Research in other submarine canyons shows that these flows can move at speeds up to 70 km/h, though 25 km/h is a more typical speed for the currents here.