Maharashtra Board Class 11 Geography Solution Chapter 7 – Indian Ocean – Relief and Strategic Importance
Balbharati Maharashtra Board Class 11 Geography Solution Chapter 7: Indian Ocean – Relief and Strategic Importance. Marathi or English Medium Students of Class 11 get here Indian Ocean – Relief and Strategic Importance full Exercise Solution.
Std |
Maharashtra Class 11 |
Subject |
Geography |
Chapter |
7 |
Chapter Name |
Indian Ocean – Relief and Strategic Importance |
1) Complete the chain:
A | B | C |
1) Pacific Ocean | 1) Christmas | 1) Bab-al-Mandeb |
2) Chagos | 2) Atlantic Ocean | 2) Lakshadweep |
3) Ashmore | 3) Maldives | 3) Indian Ocean |
4) Hormuz | 4) Malacca | 4) Cocos |
Answer – The completed chain would be –
A | B | C |
1) Pacific Ocean | 1) Atlantic Ocean | 1) Indian Ocean |
2) Chagos | 2) Christmas | 2) Lakshadweep |
3) Ashmore | 3) Maldives | 3) Cocos |
4) Hormuz | 4) Malacca | 4) Bab-al-Mandeb |
2) Give geographical reasons :
1) Salinity is less in the Bay of Bengal than in Indian Ocean.
Answer – The word salinity refers to the concentration of salts like sodium chloride, or other salts of potassium, magnesium, calcium and sulphur dissolved in oceanic waters. More the concentration of dissolved salts in water the more is the salinity and vice versa. Measurement of salinity is expressed in parts per thousand (%).
There are many factors that could affect the salinity of sea water, the primary one being the rate of evaporation (higher temperatures would mean higher rates of evaporation, in which case the salinity could increase) and the second being the amount or volume of fresh water flowing into the sea (by way of rivers, lakes or streams). More fresh water flowing in would decrease the salt concentration (cause dilution of the sea water), thereby the salinity would decrease.
Average salinity of sea water is 35% but it is observed that in Bay of Bengal it is only about 31%. This is primarily because many large rivers like the Ganga, Padma, Brahmaputra, Godavari, Krishna etc. flow into the Bay of Bengal thereby continually bringing in large volumes of fresh water, which plays a direct role in decreasing the salt concentration of the sea water.
Whereas in Indian Ocean, there are almost no rivers that are flowing into that mighty ocean and it being closer to the equator, the rates of evaporation too are higher, which increases the salt concentration or salinity.
2) The eastern coastal part of Indian Ocean is seismically active.
Answer – The eastern coastal part of the Indian ocean is seismically active because –
In the eastern part of the Indian Ocean, there are the islands like Andaman and Nicobar, which are a chain of islands along the western coast of Sumatra Island of Indonesia. Except a few coral islands in Nicobar Group, most of these islands are volcanically active islands.
Also, these islands are associated with the converging plate boundary. These islands in some cases, are the peaks of submerged mountains and any activity below may eventually result in catastrophic events in the ocean waters.
The volcanic activity as well as the tectonic plate movements make them seismically active and as in the past may result in the cause of tsunamis.
3) Gyre develops in Southern Indian Ocean.
Answer – Circular patterns ocean currents in called gyre. The main factors influencing gyre are the shape of the coastline and the wind conditions prevailing in that region.
The current system or the wind conditions coupled with the prevailing ocean temperatures and pressures in the southern part of the Indian Ocean leads to development of a large gyre. Two major arms of this large gyre are –
a) South equatorial current flowing from east to west direction under the influence of easterlies.
b) The ‘West Wind Drift’ which flows from west to east under the influence of the westerlies. The circulation of these currents are completed in the west by Mozambique – Agulhas currents and in the east by the West Australian current. This is considered to be one of the major gyres on global scale.
4) Temperatures are high in pre-monsoon season in equatorial region in northern Indian ocean.
Answer – Temperatures are high in pre-monsoon season in equatorial region in northern Indian ocean because –
In the pre-monsoon season, especially when the summer solstice (precisely 21st June ) is approaching , it gets warmer, as temperatures generally increase due to the fact that the sun shines above 23 ½ degrees North (or Tropic of Cancer).
The temperature is generally higher near the equatorial region due to the direct rays of the sun, which also happens to be the northern part of the Indian Ocean.
3) Write short notes on :
1) The width of continental shelf in Bay of Bengal and Arabian Sea
Answer – A comparative note on the continental shelf in Bay of Bengal and Arabian Sea, on both the coasts of India are as follows : –
Continental shelf of Bay of Bengal is narrow, while that in the Arabian Sea is wide.
Rivers bringing down sediments that flow into the Arabian Sea are shorter and swifter, therefore, they deposit the sediments along the Continental shelf of Arabian Sea.
Rivers flowing into Bay of Bengal are very long, slower and bring down large volumes of sediments over long distances, which ultimately get deposited along deltas that are formed the distributaries of these rivers. Sediments are not carried on to the continental shelf due to the slow pace and flow of the rivers.
Most rivers flowing into the Arabian sea form estuaries while those flowing into the Bay of Bengal form deltas.
2) Mineral resources in Indian ocean
Answer – Most of the world’s oceans contain tremendous mineral resources which have been only partially exploited till now. Most common resources are sodium chloride i.e. common salt. Many such metallic and non-metallic minerals are found on the ocean floor, e.g. Potassium occurs in large quantities. Limestones are formed extensively in the tropical oceans of the world as a consequence of the precipitate material by corals and certain plants. Gypsum is also formed during evaporation of sea water. Gypsum deposits are often mined and converted into Plaster of Paris which are extensively used for construction and interior decoration, sculptors, etc.
Petroleum and natural gas is another most important natural resource that we are extremely dependant on for day to day life.
Continental shelves often contain the world’s largest reservoirs of natural oil and gas. Minerals in large mineable quantities are also found here. Some such minerals are diamonds, chromite, ilmenite, magnetite, platinum, gold and phosphorite. Sand and industrial silica sand are the most important of hard minerals found here that are now extracted in the near offshore zone.
The abyssal plains are rich with nodules of manganese containing varying amounts of iron, nickel, cobalt, and copper. These nodules, often in the size of a pea or large enough like the size of a potato are formed by the precipitation of minerals from the seawater on rock fragments. At present, the deposits of manganese nodules are not being mined from the ocean floor, but it is quite possible that in the near future, they could be mined for use.
India has the right to mine manganese nodules from the bed of the Indian Ocean from the area which is beyond the exclusive economic zone.
3) Ocean currents in Indian ocean
Answer – Ocean currents are influenced by the shape of the coastline, its extent and the prevailing wind conditions in that area.
In the Indian ocean region, the North equatorial current is weaker than the South equatorial current. Also, in the region to the north of the equator, the currents are influenced by the seasonally occurring monsoon wind systems.
Current system to the south of the Indian Ocean forms a large gyre, with two major arms – a) South Equatorial current which flows from east to west by influence of the easterlies and b) The West Wind Drift, flowing from west to east, influenced by the westerlies.
Circulation of the gyres are completed by Mozambique – Agulhas current in the west and the West Australian current in the east, therefore the gyre is one of the major ones in the world.
The northern part of the Indian ocean is influenced by the seasonal monsoon winds which drives the current, they normally flow along the coastline. They follow clockwise directions during summer and anticlockwise directions in winter.
4) Oil and natural gas in Indian ocean
Answer – Around 40% of the world’s offshore oil production comes from the Indian Ocean which means that there is a huge reserve of oil and natural gas in the Indian Ocean region.
Large reserves of hydrocarbons are being tapped in the offshore areas of countries like Saudi Arabia, Iran, India and Western Australia. Also, beach sands, rich in heavy minerals, and offshore deposits are actively exploited by bordering countries, particularly India, South Africa, Indonesia and Sri Lanka.
4) Answer in detail :
1) Outline the importance of Indian ocean with respect to trade and transport routes
Answer – The Indian ocean geographically connects three major continents viz. Africa, Asia and Australia and serves as an important trade route for the ships.
The Indian Ocean region has three of the busiest straits viz. Homuz, Malaca and Bad-el-Mandeb. Majority of Crude oil being exported worldwide from the Gulf region pass through these routes linking the Persian Gulf, Arabian Sea and then through the Indian Ocean all the way to Australia.
Indian Ocean also connects Middle East, Africa, Europe and the Americas with Asia and Australia, therefore the trade link through this sea route is of immense importance in present times.
Due to the economic significance of this region it is of extreme importance and needs to be protected by all International bodies for ensuring smooth trade and transportation throughout the world.
2) Evaluate the strategic location of India with respect to its location in Indian Ocean.
Answer – India’s location is at the central position, strategically in the Indian Ocean area and therefore the national and economic interests are inseparably linked up with Indian Ocean.
Hence, it has always been India’s prime focus in its Foreign policy goals, to keep the Indian Ocean as a zone of Peace free from superpower rivalry and increasing cooperation among littoral countries in the region. For example Indian Ocean Rim Association for Regional Cooperation, BIMSTEC and Mekong-Ganga Cooperation (MGC). However, it is an important fact, that no industrial development, commercial growth, stable political structure is possible unless countries shores are protected and unfortunately, most of the conflicts since the end of the Cold War have also taken place in or around the Indian Ocean region.
Due to the prevailing conditions, almost all the world’s major powers have placed their military forces in the Indian Ocean region. India, being the fourth largest economy, a major concern of India in the Indian Ocean is energy. India is dependant on oil imports by about 70 percent, major part of which comes from gulf region, to which the Indian Ocean provides major sea routes connecting the Middle East, Africa and East Asia with Europe and Americas. The Indian Ocean carries a heavy traffic of crude oil and petroleum products from as far west as the Persian Gulf. Also, large reserves of hydrocarbons tapped in the offshore regions of countries like Saudi Arabia, Iran, India and Western Australia. It is estimated that around 40% of the world’s offshore oil production comes from the Indian Ocean.
With an ever increasing trade relations with the countries of the East, India has higher stakes in the region, for the future. Trade and business volumes with the ASEAN countries have doubled in a decade from a mere $1484 million in 1993. India has emerged as one of the largest importers of South East Asian goods with imports touching $10,942 million in 2004. Free Trade agreements with countries like Thailand and Singapore are set to contribute to this trend. Expanding markets, larger import flows imply not only economic prosperity but also vulnerability at sea by way of terrorism, piracy and armed robbery which needs to be tackled by the defence systems.
The area to the north of the Indian Ocean is of great significance in economic and strategic terms. India’s foreign policy orientation towards its eastern neighbours has spurred interest and attention there. India’s fast growing economy, now forecasted to become one of the three fastest growing economies in the world entails expansion of existing export and import markets
3) Explain the Indian ocean with respect to following aspects :
a) Ocean Trenches b) Abyssal Plains
c) ridges, d) Ocean Currents
Answer –
a) Ocean Trenches – The deepest portion of the oceans are called the trenches. There are only a few trenches in the Indian Ocean, unlike the other oceans. The ocean trenches of the Indian ocean are located on the eastern boundary, converging the Indo – Australian plate and the Pacific plate.
Java or Sunda Trench (7,450 m) and Ob Trench (6875m deep) are some of the major trenches in the Indian Ocean. Being in the eastern part bordering the tectonic plates, these are supposed to be at a seismically very active zone.
b) Abyssal Plains – Abyssal plains are located beyond the continental slope. They cover around 66 percent of the oceanic floor area and have a very gentle slope. Abyssal plains have deposits of polymetallic nodules which serves as a source of nickel, manganese, copper and cobalt. 2 million square kilometers of polymetallic nodules have been allotted to India for research and excavation purpose by the International Seabed Authority in The Indian Ocean region.
c) Ridges – Submerged mountain ranges that separate the deep portion of the ocean floor are called the Mid Oceanic Ridges. The Mid Oceanic Ridge in the Indian Ocean is called the Mid Indian Oceanic Ridge. It originates in the Gulf of Eden near Somalia and extends towards the South and on the East of Madagascar gets divided into two branches, once of which extends south west up to Prince Edward island, known as South West Indian Ocean Ridge and the other extends South East up to Amsterdam and St Paul Island.
The Mid Indian Oceanic ridge has many parallel ridges. The ridge also has many fractures zones, and is not continuous. Fracture zones are named as Owen fracture Zone, Amsterdam fracture zone, etc.
d) Ocean Currents – Ocean currents in the Indian Ocean differs from those in the Pacific Ocean or Atlantic Ocean currents. Further, the monsoon wind system has an effect in the northern parts of the Indian Ocean. Shape of the coastline, its extent and the prevailing wind system in the region affects the ocean currents in that region.
Equatorial currents play an important role, with the north equatorial current being weaker than the south equatorial current.
Seasonally reversing monsoon wind system to the north of the equator are an important influencing factor.
Current in the south of the equator in the Indian Ocean region develop into a large gyre, with two major arms – One is the South equatorial current flowing from east to west influenced by the easterlies, when the circulation is completed in the west by Mozambique – Agulhas currents. West Wind Drift is the second arm, considered one of the largest gyre on a global scale, flowing from west to east influenced by the westerlies, where circulation is completed in east by West Australian current.
Northern part of the Indian Ocean, seasonal monsoon winds influence the driving of the currents. In summers, they flow in clockwise direction, and anticlockwise they flow in a reversed anticlockwise direction.
5) On an outline map of the world, locate the following and make an index:
1) Sunda Trench
2) Diego Garcia
3) SW Monsoon
4) Agulhas Current
5) West Australian Current
6) Ninety East ridge
7) Strait of Holmuz
8) Chabahar port