The Bengal Fan, also known as the Ganges Fan, is the largest

submarine fan Abyssal fans, also known as deep-sea fans, underwater deltas, and submarine fans, are underwater geological structures associated with large-scale sediment deposition and formed by turbidity currents. They can be thought of as an underwater ver ...

on Earth.

Geography

It is located in Eurasia, being about long, wide with a maximum thickness of . The fan resulted from the uplift and erosion of the

Himalayas The Himalayas, or Himalaya (; ; ), is a mountain range in Asia, separating the plains of the Indian subcontinent from the Tibetan Plateau. The range has some of the planet's highest peaks, including the very highest, Mount Everest. Over 10 ...

and the

Tibetan Plateau The Tibetan Plateau (, also known as the Qinghai–Tibet Plateau or the Qing–Zang Plateau () or as the Himalayan Plateau in India, is a vast elevated plateau located at the intersection of Central, South and East Asia covering most of the Ti ...

produced by the collision between the

Indian Plate The Indian Plate (or India Plate) is a minor tectonic plate straddling the equator in the Eastern Hemisphere. Originally a part of the ancient continent of Gondwana, the Indian Plate broke away from the other fragments of Gondwana , began ...

and the

Eurasian Plate The Eurasian Plate is a tectonic plate that includes most of the continent of Eurasia (a landmass consisting of the traditional continents of Europe and Asia), with the notable exceptions of the Indian subcontinent, the Arabian subcontinent an ...

. Most of the sediment is supplied by the

Ganges The Ganges ( ) (in India: Ganga ( ); in Bangladesh: Padma ( )). "The Ganges Basin, known in India as the Ganga and in Bangladesh as the Padma, is an international river to which India, Bangladesh, Nepal and China are the riparian states." is ...

and

Brahmaputra The Brahmaputra is a trans-boundary river which flows through Tibet, northeast India, and Bangladesh. It is also known as the Yarlung Tsangpo in Tibetan, the Siang/Dihang River in Arunachali, Luit in Assamese, and Jamuna River in Bangla. It ...

rivers which supply the Lower Meghna delta in

Bangladesh Bangladesh (}, ), officially the People's Republic of Bangladesh, is a country in South Asia. It is the eighth-most populous country in the world, with a population exceeding 165 million people in an area of . Bangladesh is among the mo ...

and the Hoogly delta in

West Bengal West Bengal (, Bengali: ''Poshchim Bongo'', , abbr. WB) is a state in the eastern portion of India. It is situated along the Bay of Bengal, along with a population of over 91 million inhabitants within an area of . West Bengal is the fou ...

(India). Several other large rivers in Bangladesh and India provide smaller contributions.

Turbidity current A turbidity current is most typically an underwater current of usually rapidly moving, sediment-laden water moving down a slope; although current research (2018) indicates that water-saturated sediment may be the primary actor in the process. T ...

s have transported the sediment through a series of

submarine canyons A submarine canyon is a steep-sided valley cut into the seabed of the continental slope, sometimes extending well onto the continental shelf, having nearly vertical walls, and occasionally having canyon wall heights of up to 5 km, fro ...

, some of which are more than 1,500 miles (2,414 km) in length, to be deposited in the

Bay of Bengal The Bay of Bengal is the northeastern part of the Indian Ocean, bounded on the west and northwest by India, on the north by Bangladesh, and on the east by Myanmar and the Andaman and Nicobar Islands of India. Its southern limit is a line bet ...

up to 30 degrees

latitude In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north ...

from where it began. To date, the oldest sediments recovered from the Bengal fan are from

Early Miocene The Early Miocene (also known as Lower Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages: the Aquitanian age, Aquitanian and Burdigalian stages. The sub-epoch lasted from 23.03 ± 0.05 annum, Ma to ...

age. Their mineralogical and geochemical characteristics allow to identify their Himalayan origin and demonstrate that the

Himalaya The Himalayas, or Himalaya (; ; ), is a mountain range in Asia, separating the plains of the Indian subcontinent from the Tibetan Plateau. The range has some of the planet's highest peaks, including the very highest, Mount Everest. Over 10 ...

was already a major mountain range 20 million years ago. The fan completely covers the floor of the Bay of Bengal. It is bordered to the west by the continental slope of eastern India, to the north by the continental slope of Bangladesh and to east by the northern part of

Sunda Trench The Sunda Trench, earlier known as and sometimes still indicated as the Java Trench, is an oceanic trench located in the Indian Ocean near Sumatra, formed where the Australian- Capricorn plates subduct under a part of the Eurasian Plate. It is ...

off

Myanmar Myanmar, ; UK pronunciations: US pronunciations incl. . Note: Wikipedia's IPA conventions require indicating /r/ even in British English although only some British English speakers pronounce r at the end of syllables. As John Wells explai ...

and the

Andaman Islands The Andaman Islands () are an archipelago in the northeastern Indian Ocean about southwest off the coasts of Myanmar's Ayeyarwady Region. Together with the Nicobar Islands to their south, the Andamans serve as a maritime boundary between t ...

, the

accretionary wedge An accretionary wedge or accretionary prism forms from sediments accreted onto the non- subducting tectonic plate at a convergent plate boundary. Most of the material in the accretionary wedge consists of marine sediments scraped off from the d ...

associated with

subduction Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, ...

of the

Indo-Australian Plate The Indo-Australian Plate is a major tectonic plate that includes the continent of Australia and the surrounding ocean and extends northwest to include the Indian subcontinent and the adjacent waters. It was formed by the fusion of the Indian an ...

beneath the

Sunda Plate The Sunda Plate is a minor tectonic plate straddling the Equator in the Eastern Hemisphere on which the majority of Southeast Asia is located. The Sunda Plate was formerly considered a part of the Eurasian Plate, but the GPS measurements hav ...

and continues along the west side of the

Ninety East Ridge The Ninety East Ridge (also rendered as Ninetyeast Ridge, 90E Ridge or 90°E Ridge) is a mid-ocean ridge on the Indian Ocean floor named for its near-parallel strike along the 90th meridian at the center of the Eastern Hemisphere. It is approxima ...

. The Nicobar Fan, another lobe of the fan, lies east of the Ninety East Ridge.

History

The fan was first identified by bathymetric survey in the sixties by Bruce C. Heezen and Marie Tharp which identified the abyssal cone and canyon structures. It was delineated and named by Joseph Curray and David Moore following a geological and geophysical survey in 1968.

Biodiversity

A deep sea canyon called Swatch of No Ground (SoNG) is located south of

Sundarbans National Park The Sundarbans National Park is a national park, tiger reserve and biosphere reserve in West Bengal, India. It is part of the Sundarbans on the Ganges Delta and adjacent to the Sundarban Reserve Forest in Bangladesh. It is located to south-w ...

and the island of

Dublar Char Dublar Char is an island in Bangladesh with an area of 66.5 km2, located in the Bagerhat District of the Khulna Division. It's a tourist destination inside Sundarban. Only Teletalk Internet & Mobile Network is available here. Fisherman live ...

. This area hosts important habitats for cetaceans including endangered species such as various species of

dolphin A dolphin is an aquatic mammal within the infraorder Cetacea. Dolphin species belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontoporiidae (the b ...

s and

Bryde's whale Bryde's whale ( Brooder's), or the Bryde's whale complex, putatively comprises three species of rorqual and maybe four. The "complex" means the number and classification remains unclear because of a lack of definitive information and research. ...

s (see Swatch of No Ground Marine Protected Area).

Geography

History

Biodiversity

References

Further reading