How were the Ganges-Brahmaputra and Godavari underwater canyons formed?

The Ganges-Brahmaputra and Godavari underwater canyons, along with other major features in the Bay of Bengal, were formed as former river estuaries during the Pleistocene Epoch (approximately 2,600,000 to 11,700 years ago).1

During this period, global sea levels were significantly lower, placing the ancient shorelines at the margin of the continental shelf. This allowed rivers to cut these canyons directly into the shelf and slope. While subaerial erosion initiated the formation of many such submarine canyons, their continued development and maintenance are largely attributed to marine processes, specifically the erosion and transportation of sediments by turbidity currents and the slumping of unconsolidated material near the canyon heads.123