Long-term sea level changes
In response to plate tectonics, volcanic activity, and climatic changes, sea level has risen above or fallen below the present sea level many times in the geological past (Fig.11). About 90 million years ago, the sea level was about 300-400 m higher than at present. Sea level rose by about 120 m during the last 18000 years, mostly because of the melting of glacial ice caps in the Polar Regions. The global average rate of rise of sea level is 1-2 mm/year. This is partly caused by continued melting of glaciers and ice caps as a result of warming of the globe, and partly by the expansion of near-surface water caused by the rise in average temperature.
During the most recent sea level minimum, ~120 m below the present level about 19000-15000 years ago, rivers began discharging their sediment load directly near the shelf edge. As a result, many deep channels, called submarine canyons, were cut into the outer shelf/slope by rivers or by turbid currents generated by the sediment-laden waters. In the Bay of Bengal, there are 16 major submarine canyons.