Indian Ocean The current circulation in the Indian Ocean is different from those of the Atlantic and the Pacific Oceans. Important, Indian Ocean currents are:
South-West Morisoon Drift In summer, when the dominant wind is the south-west monsoon, the currents are blown from a south-westerly direction as the South-West Monsoon Drift.
North-East Monsoon Drift In winter, the dominant northeast monsoon blows the currents from the north-east as the North-East Monsoon Drift.
West Wind Drift A cold current, the West Wind Drift moves across the ocean in the higher latitudes from west to east. One of the branches of this cold current turns northwards along the west coast of Australia. This current, known as West Australian Current, flows northward to feed the South Equatorial Current.
Regional Currents in the Indian Ocean include the Agulhas current and Mozambique current.
Wednesday, October 28, 2009
Atlantic Ocean
Atlantic Ocean In the Atlantic Ocean, the steady trade winds in north and south of the equator drive two streams of surface water westward. They are known as North and South Equatorial Currents. They are warm currents. Other important currents of the Atlantic Ocean are as follows:
Guinea Current A current called the Equatorial Counter Current flows from west to east between the two main equatorial currents. It is known as the Guinea current off the West African coast.
Brazil Current The South Equatorial Current is split into two branches near Cape de Sao Roque (Brazil). One branch turns south as the warm Brazilian current.
Gulf Stream It is a warm current of sea water. It originates in the eastern Gulf of Mexico before flowing past Florida and the eastern seaboard of the USA. The warm Gulf stream combines with the prevailing south-westerly winds to produce the temperate climate of north-west Europe and keeps the Norwegian coast ice-free during the winter months.
Canary Current It is a cold current which flows southwards past Madeira and the Canaries off the Atlantic coast of North Africa. It is caused by the upwelling of colder water from greater depths owing to the southward deflection of the west wind drift in the North Atlantic and the transference of surface water back across the Atlantic by the North Equatorial Current.
Labrador Current The Labrador current (warm) flows southwards along part of the east coast of Canada and meets the warm Gulf Stream. The confluence of these two currents, one hot and the other cold, produces the famous fogs around Newfoundland.
Benguela Current It is a cold ocean current flowing northwards off the coast of South West Africa. It is characterised by the upwelling of relatively cold water and has an associated effect on the coastal climate of the region.
Florida Current It is one of the important ocean currents of the North Atlantic. It commences as a branch of the North Equatorial Current, which enters the Caribbean and then returns to the Atlantic Ocean through the Florida Straits as the Florida current.
Guinea Current A current called the Equatorial Counter Current flows from west to east between the two main equatorial currents. It is known as the Guinea current off the West African coast.
Brazil Current The South Equatorial Current is split into two branches near Cape de Sao Roque (Brazil). One branch turns south as the warm Brazilian current.
Gulf Stream It is a warm current of sea water. It originates in the eastern Gulf of Mexico before flowing past Florida and the eastern seaboard of the USA. The warm Gulf stream combines with the prevailing south-westerly winds to produce the temperate climate of north-west Europe and keeps the Norwegian coast ice-free during the winter months.
Canary Current It is a cold current which flows southwards past Madeira and the Canaries off the Atlantic coast of North Africa. It is caused by the upwelling of colder water from greater depths owing to the southward deflection of the west wind drift in the North Atlantic and the transference of surface water back across the Atlantic by the North Equatorial Current.
Labrador Current The Labrador current (warm) flows southwards along part of the east coast of Canada and meets the warm Gulf Stream. The confluence of these two currents, one hot and the other cold, produces the famous fogs around Newfoundland.
Benguela Current It is a cold ocean current flowing northwards off the coast of South West Africa. It is characterised by the upwelling of relatively cold water and has an associated effect on the coastal climate of the region.
Florida Current It is one of the important ocean currents of the North Atlantic. It commences as a branch of the North Equatorial Current, which enters the Caribbean and then returns to the Atlantic Ocean through the Florida Straits as the Florida current.
Pacific Ocean
Pacific Ocean North Equatorial Current A warm current, it flows westwiirds in the north of the equator. This current is produced by the north-east trades.
South Equatorial Current A warm. current, it flows westwards in the south of the equator. This current is produced by the south-east trades.
Kuro Siwo Current The north-east trade winds blow the north equatorial current off the coasts of the Philippine~ and Formosa into the East China Sea as the Kuro Siwo 01 Kuroshio or Japan current. It is a warm current.
North Pacific Current From the south-east coast oj Japan, the current flows right across the ocean from wes1 to east as the North Pacific current. North Pacific curren1 is a warm current.
Alaska Current A cold current, Alaska current flows anti-clockwise along the coast of British Columbia and Alaska. This current is a branch of the North Pacific current.
Californian Current A cold current, the Californian current flows southwards along the Pacific coastline of the USA. This current is caused by the upwelling of colder water from greater depths due to the southward deflection of the North Pacific Current. The Californian current eventually joins the North Equatorial Current, thus completing the cycle.
Peru or Humboldt Current Reaching the south western coast of South America, the South Pacific Current turns northward as Peru current. It is a cold current.
Counter Equatorial Current Between the North and the South Equatorial Currents, a current flows from west to east which is known as the Counter Equatorial Current, a warm current.
Oya Siwo or Oyashio Current The Cold Alaskan current or Bering current creeps southwards from the narrow Bering strait and is joined by the Okhotsk current (a cold current) to meet the warm Japan current as the Oya Siwo or Oyashio (a cold current).
South Equatorial Current A warm. current, it flows westwards in the south of the equator. This current is produced by the south-east trades.
Kuro Siwo Current The north-east trade winds blow the north equatorial current off the coasts of the Philippine~ and Formosa into the East China Sea as the Kuro Siwo 01 Kuroshio or Japan current. It is a warm current.
North Pacific Current From the south-east coast oj Japan, the current flows right across the ocean from wes1 to east as the North Pacific current. North Pacific curren1 is a warm current.
Alaska Current A cold current, Alaska current flows anti-clockwise along the coast of British Columbia and Alaska. This current is a branch of the North Pacific current.
Californian Current A cold current, the Californian current flows southwards along the Pacific coastline of the USA. This current is caused by the upwelling of colder water from greater depths due to the southward deflection of the North Pacific Current. The Californian current eventually joins the North Equatorial Current, thus completing the cycle.
Peru or Humboldt Current Reaching the south western coast of South America, the South Pacific Current turns northward as Peru current. It is a cold current.
Counter Equatorial Current Between the North and the South Equatorial Currents, a current flows from west to east which is known as the Counter Equatorial Current, a warm current.
Oya Siwo or Oyashio Current The Cold Alaskan current or Bering current creeps southwards from the narrow Bering strait and is joined by the Okhotsk current (a cold current) to meet the warm Japan current as the Oya Siwo or Oyashio (a cold current).
Movements in the Oceanic Waters
Movements in the Oceanic Waters The movement of ocean waters takes place in three different ways: waves, currents and tides.
Ocean Waves Waves are oscillatory movements in water, manifested by an alternate rise and fall of the sea surface. Waves are mainly produced by winds. When blowing winds impart their energy to the water in the form of friction Md pressure on the surface of the sea, waves are produced. There are three types of wind-generated waves:
(i) Sea Several trains of differing wave lengths and directional movements of sea waves occur simultaneously in the oceans. It results into an overall irregular and chaotic wave pattern called the sea.
(H) Swell Swells are the regular undulating movement of the surface of the open sea. They result from waves that have moved out of the area in which they were generated and have ceased increasing in size.
(iii) Surf The breaking waves in coastal regions are called surf.
Ocean Currents The ocean currents are the most important of the movements in the oceanic water. The ocean current is the general movement of a mass of water in a fairly defined direction over great distances. Ocean currents can broadly be divided into two types: (i) warm current, and (H) cool or cold currents. Those that flow from equatorial regions polewards have a higher surface temperature and are warm currents. Those that flow from polar regions equatorwards have a lower surface temperature and are cold currents.
The origin and nature of the movement of the currents are related to four sets of factors. (i) factors related to earth's rotation (gravitational force and force of deflection), (ii) factors originating outside the sea (atmospheric pressure, winds, etc.), (Hi) factors originating within the sea (pressure, salinity, etc.), and (iv) factors modifying the ocean currents (direction and shape of the coast, seasonal variations, etc.).
In the Northern Hemisphere, the currents move to' their right and in the Southern Hemisphere to their left. However, as an exception, in the northern part of the Indian Ocean, the direction of currents changes in response to the reversal of the monsoon winds. Warm currents move towards the cold; seas and cold currents towards the warm oceans. The direc\ion of currents in the Northern and Southern Hemispheres is determined by Coriolis force or Ferrel's law.
Ocean Waves Waves are oscillatory movements in water, manifested by an alternate rise and fall of the sea surface. Waves are mainly produced by winds. When blowing winds impart their energy to the water in the form of friction Md pressure on the surface of the sea, waves are produced. There are three types of wind-generated waves:
(i) Sea Several trains of differing wave lengths and directional movements of sea waves occur simultaneously in the oceans. It results into an overall irregular and chaotic wave pattern called the sea.
(H) Swell Swells are the regular undulating movement of the surface of the open sea. They result from waves that have moved out of the area in which they were generated and have ceased increasing in size.
(iii) Surf The breaking waves in coastal regions are called surf.
Ocean Currents The ocean currents are the most important of the movements in the oceanic water. The ocean current is the general movement of a mass of water in a fairly defined direction over great distances. Ocean currents can broadly be divided into two types: (i) warm current, and (H) cool or cold currents. Those that flow from equatorial regions polewards have a higher surface temperature and are warm currents. Those that flow from polar regions equatorwards have a lower surface temperature and are cold currents.
The origin and nature of the movement of the currents are related to four sets of factors. (i) factors related to earth's rotation (gravitational force and force of deflection), (ii) factors originating outside the sea (atmospheric pressure, winds, etc.), (Hi) factors originating within the sea (pressure, salinity, etc.), and (iv) factors modifying the ocean currents (direction and shape of the coast, seasonal variations, etc.).
In the Northern Hemisphere, the currents move to' their right and in the Southern Hemisphere to their left. However, as an exception, in the northern part of the Indian Ocean, the direction of currents changes in response to the reversal of the monsoon winds. Warm currents move towards the cold; seas and cold currents towards the warm oceans. The direc\ion of currents in the Northern and Southern Hemispheres is determined by Coriolis force or Ferrel's law.
OCEAN WATERS AND THEIR CIRCULATION
OCEAN WATERS AND THEIR CIRCULATION
The temperature and salinity are two important properties of the ocean water, which determine the movements of large masses of water, their characteristics and the types, and' also the types of marine flora and fauna.
Temperature decreases according to the increasing depth of the ocean. In general, temperature in ocean waters varies from below -5°C to over 33 "c. In the oceans, temperature of the surface water varies from one part to another. Wa!er is hottest near the equator and temperature gradually decreases polewards. The annual range of temperature is greater in the Atlantic than in the Pacific Ocean due to the difference in their size. The highest temperatures are recorded in the enclosed tropical areas. For example, the average summer temperature of the surface water of the Red Sea is about 30 "c.
The amount of salinity also varies from one part of 1200 the ocean to another" The areas of the highest salinity are found near the tropics. In the Atlantic Ocean, the salinity near the tropics is about 37 per cent. From the tropical areas of the oceans, the salinity decreases both towards the equator and towards the poles. In the polar seas, there is less salinity - between 20 per cent and 32 per cent - due to very low amount of evaporation (in the tropics, there is active evaporation owing to clear skies).
The temperature and salinity are two important properties of the ocean water, which determine the movements of large masses of water, their characteristics and the types, and' also the types of marine flora and fauna.
Temperature decreases according to the increasing depth of the ocean. In general, temperature in ocean waters varies from below -5°C to over 33 "c. In the oceans, temperature of the surface water varies from one part to another. Wa!er is hottest near the equator and temperature gradually decreases polewards. The annual range of temperature is greater in the Atlantic than in the Pacific Ocean due to the difference in their size. The highest temperatures are recorded in the enclosed tropical areas. For example, the average summer temperature of the surface water of the Red Sea is about 30 "c.
The amount of salinity also varies from one part of 1200 the ocean to another" The areas of the highest salinity are found near the tropics. In the Atlantic Ocean, the salinity near the tropics is about 37 per cent. From the tropical areas of the oceans, the salinity decreases both towards the equator and towards the poles. In the polar seas, there is less salinity - between 20 per cent and 32 per cent - due to very low amount of evaporation (in the tropics, there is active evaporation owing to clear skies).
Ocean and Oceanography
RELIEF FEATURES OF OCEANS
The floors of the ocean are rugged and complex with long mountain ranges, deep trenches and large plains. The development of the sonic depth recorder has made it possible to measure depth for mapping the ocean floor indirectly with the help of sound waves. The ocean floor can be divided into four major divisions.
(i) Continental Shelf The continental shelf is the gently sloping part of a continent that lies submerged below the sea. The shelf is generally formed due to a relative rise in sea level or marine deposition beneath the water. The average width of continental shelf is about 70 km, while the average depth is about 200 m. In all, about 7.5 per cent of the total area of the oceans is covered by the continental shelves. The North Sea and the Baltic Sea are examples of seas that lie on the continental shelf. Such seas are known as epicontinental or shelf seas.
About 20 per cent of the world production of petroleum and gas comes from shelves.
(ii) Continental Slope The continental slope is the comparatively steep slope that descends from the edge of the continental shelf to the deep-sea platform. There are five type of slopes: (i) fairly steep with the surface dissected by canyons, (ii) gentle slope with elongated hills and basins, (iii) faulted slopes, (iv) slopes with terraces, and (v) slopes with sea-mounts.
(iji) Continental Rise The continental rise or apron is the gently inclined slope which leads up from the deepsea floor (abyssal zone) to the foot of the continental slope. In other words, where the continental slope ends, the continental rise begins. The continental rise has an average slope of between 0.5° to 1° and its general relief is low.
(iv) Abyssal Plain The abyssal plains or abyssal floors are the areas of deep-ocean floor found at a depth of 3,000 to 6,000 metres.
They occupy about 40 per cent of the ocean floor and are present in all major oceans and several seas of the world. Besides, these four broad features, there are many associated features. Submarine ridges are the mountain ranges on the sea floor that rise above the general level of the abyssal plain. These ridges are either broad like a plateau, or gently sloping or steep-sided narrow mountains. The mid-ocean ridges are the largest. Areas of upland smaller than a mountain are found on the deep sea floor.
These upland areas are called abyssal hills. Seamount is an isolated mountain rising abruptly some 1,000 m from the ocean floor but. without extending above sea level. Seamounts are of volcanic origin, and are common in the Pacific Ocean. Flat-topped sea-mounts are known as guyots. The summits of guyots are almost entirely at depths of more than 1,000 m but rise upto 3 km from the ocean floor. The conical shape of the guyot suggests a volcanic origin. Like seamounts, guyots are found in abundance in the Pacific Ocean. A long, narrow and steep-sided depression on the bottom of the ocean is called a trench or a deep. Trenches or deeps are the deepest parts of the oceans with their bottoms far below the average level of the ocean floors.
They are most common in the Pacific Ocean. Submarine canyons are deep gorges on the ocean floor. They occur around all the coasts of the world and are mainly restricted to the continental shelf, slope and rise. Hudson Canyon is the best known canyon in the world. The largest canyons in the world occur in the Bering Sea off Alaska. They are the Bering, Pribilof and Zhemchung canyons.
A bank is a more or less flat-topped elevation located in the continental margins. The depth of water over a bank is relatively small. The Dogger Bank in the North Sea and the Grand Bank in the Atlantic off Newfoundland are famous examples. A shoal is a detached elevation with shallow depths. The shoal is not composed of a rock or coral.
A reef is predominantly organic deposit made by living or dead organisms that forms a mound or a rocky elevation like a ridge. It may be permanently submerged, submerged at high tide, or normally just above the water. The word reef is most commonly used for coral reefs built up in tropical seas by the hard calcareous material secreted by minute sea animals. The largest reef in the world is found off the Queensland coast of Australia.
The floors of the ocean are rugged and complex with long mountain ranges, deep trenches and large plains. The development of the sonic depth recorder has made it possible to measure depth for mapping the ocean floor indirectly with the help of sound waves. The ocean floor can be divided into four major divisions.
(i) Continental Shelf The continental shelf is the gently sloping part of a continent that lies submerged below the sea. The shelf is generally formed due to a relative rise in sea level or marine deposition beneath the water. The average width of continental shelf is about 70 km, while the average depth is about 200 m. In all, about 7.5 per cent of the total area of the oceans is covered by the continental shelves. The North Sea and the Baltic Sea are examples of seas that lie on the continental shelf. Such seas are known as epicontinental or shelf seas.
About 20 per cent of the world production of petroleum and gas comes from shelves.
(ii) Continental Slope The continental slope is the comparatively steep slope that descends from the edge of the continental shelf to the deep-sea platform. There are five type of slopes: (i) fairly steep with the surface dissected by canyons, (ii) gentle slope with elongated hills and basins, (iii) faulted slopes, (iv) slopes with terraces, and (v) slopes with sea-mounts.
(iji) Continental Rise The continental rise or apron is the gently inclined slope which leads up from the deepsea floor (abyssal zone) to the foot of the continental slope. In other words, where the continental slope ends, the continental rise begins. The continental rise has an average slope of between 0.5° to 1° and its general relief is low.
(iv) Abyssal Plain The abyssal plains or abyssal floors are the areas of deep-ocean floor found at a depth of 3,000 to 6,000 metres.
They occupy about 40 per cent of the ocean floor and are present in all major oceans and several seas of the world. Besides, these four broad features, there are many associated features. Submarine ridges are the mountain ranges on the sea floor that rise above the general level of the abyssal plain. These ridges are either broad like a plateau, or gently sloping or steep-sided narrow mountains. The mid-ocean ridges are the largest. Areas of upland smaller than a mountain are found on the deep sea floor.
These upland areas are called abyssal hills. Seamount is an isolated mountain rising abruptly some 1,000 m from the ocean floor but. without extending above sea level. Seamounts are of volcanic origin, and are common in the Pacific Ocean. Flat-topped sea-mounts are known as guyots. The summits of guyots are almost entirely at depths of more than 1,000 m but rise upto 3 km from the ocean floor. The conical shape of the guyot suggests a volcanic origin. Like seamounts, guyots are found in abundance in the Pacific Ocean. A long, narrow and steep-sided depression on the bottom of the ocean is called a trench or a deep. Trenches or deeps are the deepest parts of the oceans with their bottoms far below the average level of the ocean floors.
They are most common in the Pacific Ocean. Submarine canyons are deep gorges on the ocean floor. They occur around all the coasts of the world and are mainly restricted to the continental shelf, slope and rise. Hudson Canyon is the best known canyon in the world. The largest canyons in the world occur in the Bering Sea off Alaska. They are the Bering, Pribilof and Zhemchung canyons.
A bank is a more or less flat-topped elevation located in the continental margins. The depth of water over a bank is relatively small. The Dogger Bank in the North Sea and the Grand Bank in the Atlantic off Newfoundland are famous examples. A shoal is a detached elevation with shallow depths. The shoal is not composed of a rock or coral.
A reef is predominantly organic deposit made by living or dead organisms that forms a mound or a rocky elevation like a ridge. It may be permanently submerged, submerged at high tide, or normally just above the water. The word reef is most commonly used for coral reefs built up in tropical seas by the hard calcareous material secreted by minute sea animals. The largest reef in the world is found off the Queensland coast of Australia.
Facts About Position of States
Facts About Position of States
. Jammu and Kashmir, Himachal Pradesh, Sikkim and Arunachal Pradesh are the states of India lying cor,npletely in the Himalayas, while the state of Uttaranchal lies partly in the Himalayas and partly in the northern plains.
. Madhya Pradesh, Chhattisgarh, Jharkhand, Maharashtra, Orissa, Andhra Pradesh, Karnataka, Kerala and Tamil Nadu together make the great peninsular plateau.
. Arunachal Pradesh, Nagaland, Manipur, Mizoram, Tripura and Meghalaya are the l:1dian provinces made up of hills in the north-east India.
. Gujarat, Maharashtra, Goa, Karnataka, Kerala, Tamil Nadu, Andhra Pradesh, Orissa and West Bengal are states on the coast of India. Among our Union Territories, Daman and Pondicherry have sea boundaries.
. The Indian states on international boundaries (other country/ countries within brackets) are: Gujarat (Pakistan), Rajasthan (Pakistan), Punjab (Pakistan), Jammu and Kashmir (China and Pakistan), Himachal Pradesh (China), Bihar (Nepal), Uttaranchal (China and Nepal), Uttar Pradesh (Nepal), West Bengal (Bhutan and Bangladesh), Sikkim (China, Bhutan and Nepal), Arunachal Pradesh (Bhutan, China and Myanmar), Nagaland (Myanmar), Manipur (Myanmar); Mizoram (Bangladesh and Myanmar), Meghalaya (Bangladesh), Tripura (Bangladesh), and Assam (Bhutan, Bangladesh and Myanmar).
. The states of Haryana, Madhya Pradesh, Chhattisgarh and Jharkhand are the only land-locked states. They are not on an international border either.
. Jammu and Kashmir, Himachal Pradesh, Sikkim and Arunachal Pradesh are the states of India lying cor,npletely in the Himalayas, while the state of Uttaranchal lies partly in the Himalayas and partly in the northern plains.
. Madhya Pradesh, Chhattisgarh, Jharkhand, Maharashtra, Orissa, Andhra Pradesh, Karnataka, Kerala and Tamil Nadu together make the great peninsular plateau.
. Arunachal Pradesh, Nagaland, Manipur, Mizoram, Tripura and Meghalaya are the l:1dian provinces made up of hills in the north-east India.
. Gujarat, Maharashtra, Goa, Karnataka, Kerala, Tamil Nadu, Andhra Pradesh, Orissa and West Bengal are states on the coast of India. Among our Union Territories, Daman and Pondicherry have sea boundaries.
. The Indian states on international boundaries (other country/ countries within brackets) are: Gujarat (Pakistan), Rajasthan (Pakistan), Punjab (Pakistan), Jammu and Kashmir (China and Pakistan), Himachal Pradesh (China), Bihar (Nepal), Uttaranchal (China and Nepal), Uttar Pradesh (Nepal), West Bengal (Bhutan and Bangladesh), Sikkim (China, Bhutan and Nepal), Arunachal Pradesh (Bhutan, China and Myanmar), Nagaland (Myanmar), Manipur (Myanmar); Mizoram (Bangladesh and Myanmar), Meghalaya (Bangladesh), Tripura (Bangladesh), and Assam (Bhutan, Bangladesh and Myanmar).
. The states of Haryana, Madhya Pradesh, Chhattisgarh and Jharkhand are the only land-locked states. They are not on an international border either.
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