Bottom Relief of Indian Ocean

Indian Ocean is surrounded by Asia in North and East, Australia in East, Antarctica in south and Africa in west.  It's average depth is about 4000m. The major part of the coastal lands of Indian Ocean are parts of Gondwana Rock system hence are compact and solid.

It lacks in numbers of marginal seas, i.e. there are only few number of such seas(like Mozambique channel, Red Sea, Persian Gulf, Bay of Bengal etc.) than Pacific and Atlantic Ocean.

Some big Islands of Indian Ocean are Madagascar, Srilanka, Maldives, Mauritius, Andaman and Nicobar islands. 

According to Johnson Indian Ocean  can be divided into 3 parts:-

1. The western zone - West of Mid-Oceanic Ridge having avg. depth of 3650m, This zone has large number of Islands. 
2. The central Zone -  This zone is less deeper as it contain Mid-Oceanic Ridges.
3. The Eastern zone - This zone is deepest having average depth of 5500 metre. It also contain some Islands like Andaman Nicobar Islands but lesser in number.

Cross Section of Indian Ocean

The Indian Ocean Bottom can be studied in four pats - 

1. Continental Shelf

This is wider along the African coast as wells as along the margins of Arabian Sea and Bay of Bengal . However continental shelf is more wider in western part (640 km) while it is lesser wider in Eastern part (160 km) along the coast of Java and Sumatra.

Even Madagascar is an island in the western margin of the ocean is situated on the Continental shelf of African coastal margins.

2. Mid Oceanic Ridge

In India Ocean almost in middle of the ocean from the southern tip of Peninsular India to Antarctica running almost North to south having multiple branches. Some of the important branches of the Mid-Oceanic Ridge are :- 

I. Laccadive-Chagos Ridge 

Running from Laccadive to Maldives having average width fo 320 km (zero degree North to 30 degree South) 

II. Chagos-St. Paul Ridge

Running from Maldives to St. Paul (from 30° south to 50° South running from North-East to South-West having average depth of 320 km.

III. Amsterdam-St. Paul Plateau

Running from 30° South to 50° South

Average width is about 1600 km. From 50° South Central Ridge is bifurcated into two Ridges given below:-

IV. Kerguelen-Gausberg Ridge

This is the western part of the branch running from 40° South to 63° South.

V. Indian-Antarctic Ridge

From St. Paul to 50° South to 63° South. It connects the Mid-Oceanic Ridge with Antarctica.3. Ocean Basins 

Basically Indian Ocean can be divided into two major parts as follows:-

I. The Western Ocean Basin 

It's average depth of 3650 metre. It has many big Islands like. Madagascar Mauritius, Maldives etc. It has may sub basins:- (1) Oman Basin, (2) Arabian Basin, (3) Somalia Basin, (4) Mauritius Basin, (5) Mascarene Basin, (6) Agulhas-Natal Basin, (7) Atlantic-Indian-Antarctic Basin

Indian Ocean Bottom Relief

II. The Eastern Ocean Basin

This  basin is much deeper than previous basin having average depth of 5500 metre.

It has lesser number of Islands but some of the significant one are Srilanka, Andaman Nicobar Islands.

In this basin continental shelf are lesser extensive only 160 km.

It also has some sub basins:- (1) Eastern Indian - Antarctica Basin, (2) West Australian Basin and (3) Mid-Indian Ocean.

4. Ocean Deeps and Trenches

There are very few number of Deeps and Trenches in Indian Ocean then Antarctica Ocean and Pacific Ocean. 

About 80.1% of the Ocean consists of deep sea plains with depth ranging from 3600m to 5487m. Some important deeps and Trenches are Java-Sunda Trenche (7500 metre), Ob Trenche (6875m), Mauritius Trenche etc.

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