By going through these Maharashtra State Board Class 11 Geography Notes Chapter 7 Indian Ocean – Relief and Strategic Importance students can recall all the concepts quickly.
Maharashtra State Board Class 11 Geography Notes Chapter 7 Indian Ocean – Relief and Strategic Importance
Indian Ocean – Introduction :
- The Indian Ocean is the third largest ocean in the world. Its average depth is 4000m,
- It is the only ocean in the world named after a particular country, i.e., India.
- It occupies about 20 percent of the total oceanic area.
- The Indian Ocean spreads between Africa in the west, Asia in the north and east, Australia in the east and Southern Ocean in the south.
- It is blocked northwards, resulting in development of monsoon climate of the Indian sub-continent.
Bottom Relief of the Indian Ocean :
- Continental Shelf
- Mid-Oceanic Ridges
- Ocean Basins
- Oceanic Deeps
- Islands
Continental Shelf:
- Continental Shelf is a portion of continents, submerged under oceanic water.
- It is normally occupied by gulfs, seas, bays, straits.
- A continental shelf may be extensive, narrow, wide.
- These shelfs are covered with deposits brought by agents of erosion.
- Some of the sedimentary deposits, remain deposited for a long time, which then forms sedimentary rocks.
Mid-Oceanic Ridges :
- They are submerged mountain ranges that separate deep portions of the sea (ocean) floor.
- The Indian Ocean consists of a Mid Oceanic ridge called as a Mid Indian Oceanic ridge.
- It originates from Gulf of Eden near the Peninsula of Somalia.
- It extends toward the south and at east side of Madagascar.
- This ridge gets divided into two branches :
- The branch diverts towards southwest and extends up to Prince Edward Island. It is known as Southwest Indian Ocean ridge.
- The branch extends southeast up to Amsterdam and St. Paul Island.
- Mid Indian Oceanic ridge has many parallel ridges.
- This ridge does not flow continuously due to fracture zones such as Owen fracture zone, Amsterdam fracture zone, etc.
- Apart from Mid-Oceanic Ridges there is Kerguelen Plateau, in south side of Madagascar is Madagascar Plateau and in south side of Africa is Agulhas Plateau.
Indian Ocean Basins :
- Oman
- Somali
- Mascarene
- West Australian
- Ganga
- Arabian
- Mauritius
- Aguihas-Natal
- Mid-Indian
Ocean Deeps and Trenches:
They are the deepest portions in the oceans.
Ocean Deeps and Trenches:
- Jeva or Sunda Trench
(7,450 m deep) - Ob Trench
(6,875 m deep)
Islands:
land mass surrounded by ocean on all sides.
Distribution of temperature in the Indian Ocean :
- The study of temperature influences the biotic component in the oceans.
- Temperature is also largely responsible for the movement in the oceanic water.
Distribution of salinity in the Indian Ocean :
- Salinity influences the density of the ocean water.
- It cause the movements in the ocean water.
Temperature : of Indian Ocean water depends on the seasons
Pre-Monsoon Season:
- summer solstice
- Temperature increases especially in the southern portion closer to the equator.
South-We st Monsoon Season
- Temperature is lowered in the Arabian Sea because of monsoonal winds.
North-East
- Monsoon Season Winter solstice
- Temperature reduced
- Northern parts of Bay of Bengal record temperature of about 24°C.
Salinity: Salinity is the measure of amount of salts in the sea water. It is expressed as parts per thousand (%o). Average salinity of sea-water is 35%o.
- The salinity is generally high around the Somali Peninsula and closer to the Saudi Arabian Coast due to high temperature and low rainfall; there are very few rivers entering into the sea in this area.
- In the Bay of Bengal, huge discharges from the Ganga system and also from the Peninsular rivers leads to lowering of salinity in this area.
- Salinity is less in the rainy season.
Ocean Currents in the Indian Ocean :
- They are affected by Monsoon Wind System, especially in the northern Indian Ocean.
- They mix waters, transfer heat from one part of the ocean to the other.
- Indian ocean currents are affected by:
- Shape of its coastline
- Extent of coastline
- Peculiar arrangement of the wind system in the region.
Indian Ocean Currents:
- South Equatorial Current
- The West Wind Drift
1. The West Wind Drift
- flows east to west, influenced by easterlies.
- circulation completed by Mozambique-Agulhas currents
2. South Equatorial Current:
- flows east to west, to east, influenced by westerlies
- circulation completed by West Australian Current.
→ In the northern portion of the Indian Ocean, seasonal monsoonal winds drive the currents.
→ These currents mostly follow along the coast lines.
→ During summer they follow in the clockwise direction and during the winter they flow in anticlockwise direction.
Importance of the Indian Ocean :
- The Indian Ocean region connects three continents namely Asia, Africa and Australia.
- It supports some of Asia’s biggest economies.
- It contains three busiest straits — Hormuz, Malacca and Bab-el-Mandeb.
- Majority of crude oil exported by Gulf countries passes through this route via Strait of Hormuz.
- The economy of island countries like Maldives and Seychelles located in the Indian Ocean depends upon the marine ecosystem and marine tourism in the Indian Ocean.
- Indian Ocean region has become important for countries that have military and naval bases, leading to tension in the region.
- Abyssal plains of the Indian Ocean are a source of nickel, copper, manganese, and cobalt.
Importance of the Indian Ocean for India :
- The Indian Ocean provides sea routes connecting the Middle East, Africa, and East Asia with Europe and America.
- It carries heavy traffic of petroleum and petroleum products from the oilfield of the Persian Gulf and Indonesia.
- Large reserves of hydrocarbons tapped in the offshore areas.
- Beach sands, rich in heavy minerals and offshore deposits are actively exploited by bordering countries, particularly India.
- The increasing trade relations with the countries of the East, India has higher stakes in the region in the future.
- The increasing trade has brought about threats of piracy, armed robbery, and maritime terrorism.