Bay of Bengal 01

Bay of Bengal a northern extended arm of the indian ocean, is located between latitudes 5°N and 22°N and longitudes 80°E and 100°E. It is bounded in the west by the east coasts of Sri Lanka and India, on the north by the deltaic region of the Ganges-Brahmaputra-Meghna river system, and on the east by the Myanmar peninsula extended up to the Andaman-Nicobar ridges. The southern boundary of the Bay is approximately along the line drawn from Dondra Head in the south of Sri Lanka to the north tip of Sumatra. The Bay occupies an area of about 2.2 million sq km and the average depth is 2,600m with a maximum depth of 5,258m. Bangladesh is situated at the head of the Bay of Bengal.

Bottom topography characterised by a broad U-shaped basin with its south opening to the Indian Ocean. A thick uniform abyssal plain occupies almost the entire Bay of Bengal gently sloping southward at an angle of 8°-10°. In many places underwater valleys dissect this plain mass.

Continental Shelf the width of the continental shelf off the coast of Bangladesh varies considerably. It is less than 100 km off the south coast between Hiron Point and the swatch of no ground and more than 250 km off the coast of cox's bazar. sediments are fine seaward and westward with the thickest accumulation of mud near the submarine canyon, the Swatch of no Ground. The shallow part (less than 20m) of the continental shelf off the coast of chittagong and teknaf is covered by sand and the intertidal areas show well-developed sandy beaches. The shallower part of southern continental shelf off the coast of the sundarbans, patuakhali and noakhali is covered by silt and clay; and extensive muddy tidal flats are developed along the shoreline. Some of the shoals and sand ridges present on this part of the continental shelf show an elongation pattern pointed towards the Swatch of no Ground.

Swatch of no Ground also known as Ganga Trough. Swatch of no Ground has a comparatively flat floor 5 to 7 km wide and walls of about 12° inclination. At the edge of the shelf, depths in the trough are about 1,200m. The Swatch of no Ground has a seaward continuation for almost 2,000 km down the Bay of Bengal in the form of fan valleys with levees. The sandbars and ridges near the mouth of the ganges-brahmaputra delta pointing toward the Swatch of no Ground showing sediments are tunnelled through this trough into the deeper part of the Bay of Bengal. The Swatch of no Ground is feeding the Bengal Deep Sea Fan by turbidity currents.

Sunda Trench also known as Java Trench. Running parallel along the west side of the arc of the Nicobar and Andaman islands it is extended northward up to 10°N into the Bay and joins the eastern limit of the Himalayan range. It originated tectonically at the junction of the Indian and Myanmar plates.

Ninety East Ridge major feature of the Indian Ocean which runs in a north-south direction approximately along the longitude 90°E. It lies at the immediate outboard of the Sunda Trench between the Bengal Fan and the Nicobar Fan. The Ninety East Ridge has existed since early in the formation of the Bay of Bengal. The ridge represents the trace of a hot spot formed during the northward flight of India and its associated oceanic lithosphere of the Bay of Bengal.

Eighty-five Ridge a ridge along 85°E longitude. More than 5 km thick sediments have been deposited on either sides of the ridge. The main turbidity current channel of the subaerial drainage pattern lies immediately east of the buried ridge.

Bengal Deep Sea Fan the world's largest submarine fan, also known as Bengal Fan. Together with its eastern lobe, the Nicobar fan, it covers an area of 3106 sq km. It is 2,800 to 3,000 km long, 830 to 1,430 km wide and more than 16 km thick beneath the northern Bay of Bengal. Sediments are tunnelled to the fan via a delta-front trough, the Swatch of no Ground. It can be divided into three parts: upper fan, middle fan and lower fan. Rapid terrigenous sedimentation on an incipient Bengal fan began in the Eocene age (58 to 37 million years ago) as a response to the first intraplate collision and continued to the present, building the world's largest submarine fan. [Mahmood Alam]

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