page_title: Andaman Sea
section_title: Geology
hierarchical_section_title: Andaman Sea / Geology
caption_attribution_description: English: Satellite image of the Andaman Sea showing the green-algae and silt deposits due to the Irrawaddy River in its northern part
context_page_description: The Andaman Sea is a marginal sea of northeastern Indian Ocean bounded by the coastlines of Myanmar and Thailand along the Gulf of Martaban and west side of the Malay Peninsula, and separated from the Bay of Bengal to its west by the Andaman Islands and the Nicobar Islands. Its southernmost end is defined by Breueh Island, an island just north of Sumatra, and communicates with the Malacca Strait.
  Traditionally, the sea has been used for fishery and transportation of goods between the coastal countries and its coral reefs and islands are popular tourist destinations. The fishery and tourist infrastructure was severely damaged by the 2004 Indian Ocean earthquake and tsunami.
context_section_description: The northern and eastern side of the basin is shallow, as the continental shelf off the coast of Myanmar and Thailand extends over 200 km (marked by 300 m isobath). About 45 percent of the basin area is shallower (less than 500 m depth), which is the direct consequence of the presence of the wider shelf. The continental slope which follows the eastern shelf is quite steep between 9°N and 14°N. Here, the perspective view of the submarine topography sectioned along 95°E exposes the abrupt rise in depth of sea by about 3,000 m within a short horizontal distance of a degree. Isobaths corresponding to 900 m and 2000 m are also shown in the figure to emphasize the steepness of the slope. Further, it may be noted that the deep ocean is also not free from sea mounts; hence only around 15 percent of the total area is deeper than 2,500 m.
  The northern and eastern parts are shallower than 180 meters (590 feet) due to the silt deposited by the Irrawaddy River. This major river flows into the sea from the north through Myanmar. The western and central areas are 900–3,000 meters (3,000–9,800 ft) deep. Less than 5% of the sea is deeper than 3,000 meters (9,800 feet), and in a system of submarine valleys east of the Andaman-Nicobar Ridge, the depth exceeds 4,000 meters (13,000 feet). The sea floor is covered with pebbles, gravel, and sand.
  The western boundary of the Andaman Sea is marked by volcanic islands and sea mounts, with straits or passages of variable depths that control the entry and exit of water to the Bay of Bengal. There is a drastic change in water depth over a short distance of 200 km, as one moves from the Bay of Bengal (around 3,500 m deep) to the vicinity of islands (up to 1,000 m depth) and further into the Andaman Sea. Water is exchanged between the Andaman Sea and the Bay of Bengal through the straits between the Andaman and Nicobar Islands. Out of these, the most important straits (in terms of width and depth) are: Preparis Channel (PC), Ten Degree Channel (TDC), and Great Channel (GC). PC is the widest but shallowest (250 m) of the three and separates south Myanmar from north Andaman. TDC is 600 m deep and lies between Little Andaman and Car Nicobar. GC is 1,500 m deep and separates Great Nicobar from Banda Aceh.
caption: Satellite image of the Andaman Sea showing the green algae and silt deposits due to the Irrawaddy River in its northern part
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