Editing Andaman Sea (section)

==Geology==
[[File:AndamanSeaNASA1.jpg|thumb|left|upright|Satellite image of the Andaman Sea showing the [[green algae]] and silt deposits due to the [[Irrawaddy River]] in its northern part]]
The northern and eastern side of the basin is shallow, as the [[continental shelf]] off the coast of Myanmar and Thailand extends over {{convert|200|km}} (marked by {{convert|300|m}} [[isobath]]). About 45 percent of the basin area is shallower (less than {{convert|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 {{convert|3,000|m}} within a short horizontal distance of a degree. Isobaths corresponding to {{convert|900 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 {{convert|2,500|m}}.<ref name="indjst.org">S. R. Kiran (2017) [http://www.indjst.org/index.php/indjst/article/view/115764 General Circulation and Principal Wave Modes in Andaman Sea from Observations], Indian Journal of Science and Technology {{ISSN|0974-5645}}</ref>

[[File:The Bathymetry (in metres) of A-SEA in 2D and 3D (sectioned along 95E).png|thumb|The bathymetry (in metres) of the Andaman Sea in 2D and 3D (sectioned along 95°E)<ref name="indjst.org"/>]]
[[File:Percentage of total area of A-SEA corresponding to diferent ranges of depth.png|thumb|Percentage of the total area of Andaman Sea corresponding to different depth ranges<ref name="indjst.org"/>]]

The northern and eastern parts are shallower than {{convert|180|m|ft|abbr=off|sp=us}} 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 {{convert|900|–|3,000|m|ft|sp=us}} deep. Less than 5% of the sea is deeper than {{convert|3000|m|ft|abbr=off|sp=us}}, and in a system of submarine valleys east of the Andaman-Nicobar Ridge, the depth exceeds {{convert|4000|m|ft|abbr=off|sp=us}}.<ref name=brit/> The sea floor is covered with pebbles, gravel, and sand.<ref name=bse/>

The western boundary of the Andaman Sea is marked by 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 {{convert|200|km}}, as one moves from the [[Bay of Bengal]] (around {{convert|3,500|m}} deep) to the vicinity of islands (up to {{convert|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 ({{convert|250|m}}) of the three and separates south Myanmar from north Andaman. TDC is {{convert|600|m}} deep and lies between [[Little Andaman]] and [[Car Nicobar]]. GC is {{convert|1,500|m}} deep and separates [[Great Nicobar]] from [[Banda Aceh]].

===Ocean floor tectonics===
[[File:Neic slav fig72narrow.jpg|thumb|left|The Andaman Sea, showing [[tectonic plate]] boundaries]]
[[File:Tectonics Sumatra quake.gif|thumb|Tectonic setting of Sumatra earthquake (2004)]]

Running in a rough north–south line on the seabed of the Andaman Sea is the boundary between two [[tectonic plate]]s, the [[Burma Plate]] and the [[Sunda Plate]]. These plates (or microplates) are believed to have formerly been part of the larger [[Eurasian Plate]], but were formed when [[transform fault]] activity intensified as the [[Indian Plate]] began its substantive collision with the Eurasian [[continent]]. As a result, a [[back-arc basin]] center was created, which began to form the marginal [[Oceanic basin|basin]] which would become the Andaman Sea, the current stages of which commenced approximately 3–4&nbsp;million years ago ([[annum|Ma]]).<ref>{{cite web| author=J.R. Curray| title=2002 Chapman Conference on Continent – Ocean Interactions within the East Asian Marginal Seas| work=Tectonics and History of the Andaman Sea Region (abstract)| url=http://www.agu.org/meetings/cc02cabstracts/curray-p.pdf| access-date=20 September 2010| archive-date=23 March 2005| archive-url=https://web.archive.org/web/20050323100450/http://www.agu.org/meetings/cc02cabstracts/curray-p.pdf| url-status=dead}}</ref>

The boundary between two major tectonic plates results in high seismic activity in the region (see [[List of earthquakes in Indonesia]]). Numerous earthquakes have been recorded, and at least six, in 1797, 1833, 1861, [[2004 Indian Ocean earthquake and tsunami|2004]], 2005, and [[September 2007 Sumatra earthquakes|2007]], had a [[Moment magnitude scale|magnitude]] of 8.4 or higher. On 26 December 2004, a large portion of the boundary between the Burma plate and the Indo-Australian plate slipped, causing the [[2004 Indian Ocean earthquake and tsunami|2004 Indian Ocean earthquake]]. This [[megathrust earthquake]] had a magnitude of 9.3. Between {{convert|1300|and|1600|km}} of the boundary underwent [[thrust fault]]ing and shifted by about {{convert|20|m}}, with the sea floor being uplifted several meters.<ref>{{cite journal|url=http://walrus.wr.usgs.gov/reports/reprints/Geist_BSSA_97.pdf |doi=10.1785/0120050619|title=Implications of the 26 December 2004 Sumatra–Andaman Earthquake on Tsunami Forecast and Assessment Models for Great Subduction-Zone Earthquakes|journal=Bulletin of the Seismological Society of America|year=2007|volume=97|issue=1A|pages=S249–S270|last1=Geist|first1=E. L.|last2=Titov|first2=V. V.|last3=Arcas|first3=D.|last4=Pollitz|first4=F. F.|last5=Bilek|first5=S. L.|bibcode=2007BuSSA..97S.249G}}</ref> This rise in the sea floor generated a massive [[tsunami]] with an estimated height of {{convert|28|m|ft|abbr=off|sp=us}}<ref>Tom Paulson (7 February 2005) [https://web.archive.org/web/20101205010745/http://www.seattlepi.com/local/211012_tsunamiscience07.html New findings super-size our tsunami threat. 80-foot waves blasted Indonesia, scientists now say], ''Seattle Post-Intelligencer''</ref> that killed approximately 280,000 people along the coast of the Indian Ocean.<ref>[http://news.bbc.co.uk/2/hi/asia-pacific/4204385.stm Indonesia quake toll jumps again], BBC, 25 January 2005</ref> The initial quake was followed by a series of aftershocks along the arc of the Andaman and Nicobar Islands. The entire event severely damaged the fishing infrastructure.<ref name=Panjarat>{{cite web|last1=Panjarat|first1=Sampan|title=Sustainable Fisheries in the Andaman Sea Coast of Thailand| url=https://www.un.org/depts/los/nippon/unnff_programme_home/fellows_pages/fellows_papers/panjarat_0708_thailand_PPT.pdf|publisher=United Nations|year=2008|access-date=16 May 2015}}</ref>{{RP|40–42}}

===Volcanic activity===
[[File:Ile Barren, 1995.jpg|thumb|Eruption of the [[Barren Island (Andaman Islands)|Barren Island]] volcano in 1995. Andaman Islands (on top) are c. 90 km distant]]

Within the sea, to the east of the main [[Great Andaman]] island group, lies [[Barren Island (Andaman Islands)|Barren Island]], the only currently [[active volcano]] associated with the [[South Asia|Indian subcontinent]]. This island volcano is {{convert|3|km|0|abbr=on}} in diameter and rises {{convert|354|m}} above sea level. Its recent activity resumed in 1991 after a quiet period of almost 200 years.<ref>D. Chandrasekharam, Jochen Bundschuh (2002) [https://books.google.com/books?id=aRkBJRLV8AwC&pg=PA408 Geothermal energy resources for developing countries], Taylor & Francis {{ISBN|90-5809-522-3}} p. 408</ref> It is caused by the ongoing [[subduction]] of the India plate beneath the Andaman [[island arc]], which forces [[magma]] to rise in this location of the Burma plate. The last eruption started on 13 May 2008 and continues.<ref>[http://www.volcano.si.edu/world/volcano.cfm?vnum=0600-01=&volpage=erupt Barren Island] {{Webarchive|url=https://web.archive.org/web/20201202213229/https://volcano.si.edu/world/volcano.cfm?vnum=0600-01=&volpage=erupt |date=2 December 2020 }}, Smithsonian National Museum of Natural History</ref> The volcanic island of [[Narcondam Island|Narcondam]], which lies further north, was also formed by this process. No records exist of its activity.<ref>[http://www.volcano.si.edu/world/volcano.cfm?vnum=0600-001 Narcondum] {{Webarchive|url=https://web.archive.org/web/20210405015451/http://www.volcano.si.edu/world/volcano.cfm?vnum=0600-001 |date=5 April 2021 }}, Smithsonian National Museum of Natural History</ref>

===Sediments to the Sea===
Collectively, the modern Ayeyarwady (Irrawaddy) and Thanlwin (Salween) rivers deliver >600 Mt/yr of sediment to the sea.<ref name="sciencedirect2020">{{cite journal  |title=Liu, J.P., Kuehl, S.A., Pierce, A.C., Williams, J., Blair, N.E., Harris, C., Aung, D.W., Aye, Y.Y., 2020. Fate of Ayeyarwady and Thanlwin Rivers Sediments in the Andaman Sea and Bay of Bengal. Marine Geology, 106137. |journal=Marine Geology |year=2020|volume=423 |page=106137 |doi=10.1016/j.margeo.2020.106137|doi-access=free|last1=Liu |first1=J. Paul |last2=Kuehl |first2=Steven A. |last3=Pierce |first3=Austin C. |last4=Williams |first4=Joshua |last5=Blair |first5=Neal E. |last6=Harris |first6=Courtney |last7=Aung |first7=Day Wa |last8=Aye |first8=Yin Yin }}</ref> Most recent studies show: 1) There is little modern sediment accumulating on the shelf immediately off the Ayeyarwady River mouths. In contrast, a major mud wedge with a distal depocenter, up to {{convert|60|m}} in thickness, has been deposited seaward in the Gulf of Martaban, extending to approximately {{convert|130|m}} water depth into the Martaban Depression. Further, 2) There is no evidence showing that modern sediment has accumulated or is transported into the Martaban Canyon; 3) a mud drape/blanket is wrapping around the narrow western Myanmar Shelf in the eastern Bay of Bengal. The thickness of the mud deposit is up to {{convert|20|m}} nearshore and gradually thins to the slope at {{convert|−300|m}} water depth, and likely escapes into the deep Andaman Trench; 4) The estimated total amount of Holocene sediments deposited offshore is approximately {{convert|1290 × 109|t}}. If we assume this has mainly accumulated since the middle Holocene highstand (~6000 yr BP) like other major deltas, the historical annual mean depositional flux on the shelf would be {{convert|215|Mt}} per year, which is equivalent to ~35% of the modern Ayeyarwady-Thanlwin rivers derived sediments; 5) Unlike other large river systems in Asia, such as the Yangtze and Mekong, this study indicates a bi-directional transport and depositional pattern controlled by the local currents that are influenced by tides, and seasonally varying monsoons winds and waves.<ref name="sciencedirect2020" />