Andaman Sea

Off Myanmar, the Andaman Sea receives a vast burden of sediment from the Ayeyarwady and Salween systems. Together the two rivers deliver more than 600 million tonnes each year. Much of this material does not remain immediately outside the Ayeyarwady mouths; currents and tides shift it seaward and alongshore, creating a broad muddy environment around the Gulf of Martaban. The most striking deposit is a major mud wedge with its thickest distal section in the Gulf of Martaban.

It reaches up to sixty metres thick and extends into the Martaban Depression at water depths of roughly 130 metres. This broad body of mud shows how sediment can accumulate far from the river mouths that supply it. A narrower blanket covers the western Myanmar shelf, thinning from about twenty metres near shore toward the continental slope. The shelf and deep basin meet over a short distance, so muddy coastal water contrasts with steep slopes and dark offshore depths.

Rivers eroding the Southeast Asian mainland tie this sea to distant mountain catchments. Seasonal currents redistribute the load, while fishing communities work among channels, mudflats and changing coastal shallows. The buried sediment also preserves finds of sea-level and coastline change over thousands of years.