UPPSC Target PT 90 days Planner

When few months are left for UPPSC Prelims 2021, it becomes very important for every aspirant to be on their toes and follow an organized plan which will help them clear this exam and keep them at ease during the preparation phase.

UPPSC Target PT in 90 Days Planner will provide you with a daily time table, which will comprise of the following:

  • Daily Value added Article
  • Daily subject specific Quiz according to the given schedule
  • Snippets (UP through MAP) for maximizing your Prelims score.

Day 28: Geography - Geography (Day 26 to 36)

Oceanography

Oceans form a single, large, continuous body of water encircling all the landmass of the earth. They account for four- fifth of the Southern Hemisphere and three fifth of the Northern Hemisphere. They contain 97.2 percent of the world’s total water. There are four principal oceans in the world which are separated largely on the basis of their geographical locations. These are the Pacific Ocean, the Indian ocean, the Atlantic Ocean and the Arctic Ocean. All the other seas, inland seas or the arms of the oceans, are counted within these four main oceans.

Relief of the ocean basins

The Ocean basins are broadly divided into four major sub-divisions. They are:

(a) Continental shelf;

(b) Continental slope;

(c) Abyssal plains and

(d) The ocean deeps

Continental Shelf

  • There is no clear or well-defined line separating oceans from continents. Infact, continents do not end abruptly at shoreline. They slope seaward from the coast to a point where the slope becomes very steep. The shallow submerged extension of continent is called the continental shelf. The depth of this shallow sea water over the continental shelf ranges between 120 to 370 metres. The width of the continental shelf varies greatly ranging between a few kilometres to more than 100 kilometres. This variation can be seen even in the context of Indian peninsula. The continental shelf off the eastern coast of India is much wider than that of the western coast.
  • Most of the continental shelves represent land which has been inundated by a rise in sea level. Many regards their formation due to the erosional work of waves or due to the extension of land by the deposition of river borne material on the off-shore terraces. Off the coast regions which were once covered by ice sheets, they may have developed due to glacial deposits.
  • The continental shelves are of great importance to man. The shallow water over the shelf enables sunlight to penetrate through the water to the bottom and encourages growth of microscopic plants and animals called planktons. These planktons are the food for fishes. Continental shelves are the source of fishes, mineral including sand and gravel. A large quantity of the world’s petroleum and natural gas is obtained from these shelves. The Bombay High and the recent discovery of petroleum in the Godavari basin are examples of on shore drilling on the continental shelf. Coral reefs and lipoclastic materials are also common on continental shelves.
  • One of the striking features of the continental shelf is the presence of submarine canyons which extend to the continental slope. These canyons are ‘steepsided valleys’ cut into the floor of the seas. They are very similar to the gorges found on the continents. Godavari Canyon in front of the Godavari river mouth is 502 metres deep.
  • One of the reasons for the formation of submarine canyon is underwater landslide. The sediments collected on the continental shelves get dislodged by a storm or an earthquake.

Continental Slope

  • The continuously sloping portion of the continental margin, seaward ofthe continental shelf and extending down to the deep-sea floor of the abyssal plain, is known as continental slope. It is characterised by gradients of 2.5 degrees. It extends between the depth of 180 to 3600 metres. In some places, for example, off the shore of Philippines, the continental slope extends to a great depth.
  • Continental slopes, mainly due to their steepness and increasing distance from the land have very little deposits of sediments on them. Sea life is also far less here than on the shelf.
  • Along the base of the continental slope is a deposit of sediments. This belt of sedimentary deposits forms the continental rise. In some regions the rise is very narrow but in others it may extend up to 600 km in width.

Abyssal Plain

  • Abyssal plains covering a major portion of ocean floor between the depth of 3000m to 6000m. They were once regarded as featureless plains but modem devices have shown that they are as irregular as the continental plain or surface. They have extensive submarine plateaus, hills, guyots and seamounts.
  • The floor of the abyssal plain is covered by sediments. The plains close to the continents are covered mostly by sediments brought down from the land. But those seas which favour, an abundant growth of organisms have a thick layer of sediments, formed from the remains of living things.
  • These sediments are called oozes. Some of the open seas do not support enough life to produce ooze on the floor. They are covered with a type of sediment called red clay which is of volcanic origin or made up of tiny particles brought by wind and rivers.

Submarine Ridges

  • The lofty mountain systems which exist on the continents are also represented beneath the ocean waters. These oceanic mountains are known as submarine ridges. They are linear belts occurring near the middle of the oceans and are also called mid-oceanic ridges.
  • All the mid oceanic ridges constitute a world-wide system which is interconnected from ocean to ocean. These ridges are intersected by faults. The oceanic ridge is the site of frequent earthquakes.
  • Volcanism is common in ocean ridges and it produces many relief features. The Mid-Atlantic Ridge is the largest continuous submerged mountain ridge which runs from north to south in the Atlantic-Ocean.

Seamounts and Guyots

  • Scattered over the entire sea floor are thousands of submerged volcanoes with sharp tops called seamounts. Sometimes they rise above the sea as isolated Islands. Hawaii and Tahiti Islands are the exposed tops of volcanoes.
  • Volcano rising above the ocean floor whose top has been flattened by erosion and is covered by water is called guyot.

The Ocean Deeps

  • The ocean deeps are the deepest part of the ocean. They are long, narrow, steep sided and flat-floored depressions on the ocean floor. They are generally called submarine trenches.
  • These trenches are not always located in the middle of the ocean basins, as may be generally expected but are situated very close or parallel to the continents bordered by Fold Mountains. They are usually found adjacent to the areas of volcanic and earthquake activity. Great earthquakes and tsunamis are born in them. They occur in all the major oceans.
  • The Pacific Ocean has the largest number of trenches. The Mariana Trench in ‘the Pacific Ocean is the deepest known part of the oceans. This trench is so deep that if we place the highest mountain of the world - the Mt. Everest in it, even this shall have a few kilometres of water above its summit.

Reliefs of Atlantic Ocean

Properties of Ocean Waters

The temperature and salinity are two important aspects of the ocean waters which affect their movements. Therefore, the temperature, salinity and density of the ocean water have special significance in the study of circulation of ocean waters.

Temperature

  • The temperature of the surface water of the oceans varies in much the same way as that of the land surface. This is because insolation is responsible for the varying quantities of heat which are received at different latitudes and in different seasons.
  • Generally, the temperature is higher near the equator and gradually decreases towards the poles. . The mean annual temperatures of about 27°C or higher, are common in tropical seas but there is a general decrease towards the poles where the mean temperature of around 1.8°C is found.
  • However, the decrease of temperature of surface water towards the poles or increase towards the equator is not uniform because drifting warm water from the tropical seas may move into higher latitudes or vice versa and gives a local increase or decrease of temperature.
  • Upwelling of deep, cold water also reduces locally the surface temperature of tropical and subtropical sea waters. The high temperatures of waters are found in enclosed seas in the tropics e.g. the Red Sea.
  • The Arctic and Antarctic waters are so cold that their surface remains permanently frozen down to a depth of several metres. In the summer months, parts of the ice break off as icebergs which dilute the water and lower the surface temperature of surrounding ice free seas.
  • There is also variation in the vertical distribution of temperature. Temperature decreases with increase in depth. This is because the surface of the sea water receives the largest amount of insolation. As the rays penetrate the water, their intensity is reduced by scattering, reflection and diffusion.
  • However, the rate of decrease in the temperature is not equal at all depth. Upto a depth of about 100 metres, the temperature of water is about the same as that of the surface, while it falls from 15°C to about 2°C between the surface and a depth of 1,800 metres. The decrease between 1,800 and 4,000 metres is from 2°C to about 1.6°C.
  • The main process of heating the ocean waters are (1) by absorption of heat from the sun (2) by convection of heat through the ocean bottom from the interior of the earth. The cooling processes are: (1) by loss of heat to the atmosphere, (2) by evaporation.

Salinity

  • One of the most striking characteristics of the ocean water is its salinity or saltiness.
  • When we speak of salinity we have in mind not only common salt or sodium chloride but a great variety of other salts as well. The dominant salts among these are sodium chloride &Magnesium Chloride with 77.7% & 10.9% respectively.
  • Due to the free movement of ocean water, the proportion of different salts remains remarkably constant in all oceans and even to great depth. But the degree of concentration of the salt solution in oceans does vary appreciably in different seas.
  • The salinity of the ocean water is produced by a large number of dissolved chemical compounds.
  • Salinity is defined as the weight in grammes of solid material left after the evaporation of 1000 grammes of sea water. If the weight of solid material is 35 grammes (and it is usually very near this figure), the salinity would be shown 350 / 00 (35 per thousands). Salinity is expressed in this way rather than as percentage.
  • In the Baltic Sea, fresh water enters it from the surrounding land and reduce the salinity to 70 / 00 and it may fall in this sea as low as 20 / 00.
  • But great evaporation combined with a very dry climate in the Red Sea region gives the water of this sea a high salinity of 410 / 00 to 420 / 00.
  • In enclose sea, which are areas of inland drainage such as the Caspian Sea, the salinity is very high, 180 / 00 in the Dead Sea of Jordan. The salinity may be as high as 250 / 00.
  • The variation of salinity in different seas and oceans is affected by (i) The rate of evaporation, (ii) The amount of fresh water added by streams and icebergs, (iii) Mixing of the ocean waters.

Movements of Ocean Waters

The waters of oceans are never still. The oceans actually exhibit three major types of movements - waves, tides and currents.

Waves

  • Waves are oscillatory movements that result in the rise and fall of water surface. Infact, the movement of each water particle in a wave is circular. The movement of the waves is just like the wind blowing across a wheatfield and causing wave like ripples to roll across its surface. The wheat stalk returns to its original position after the passage of each wave of wind. Similarly water also returns to its original position after transmitting a wave.
  • A wave has two major parts. The raised part is called the crest. Between the two crests are low areas called troughs. The vertical distance between trough and crest is called wave height. The horizontal distance between two crests or two troughs is called wave length. The time it takes for two crests to pass a given point is called wave period. Fast moving waves have short period while slow moving waves have long period.
  • The size and force of a sea wave depends on three factors (i) Velocity of the wind, (ii) The length of time the wind blows and (iii) Distance that the wind has travelled across the open sea. This is called a fetch.

Components of Sea waves

Tides

  • Along a coast all over the world, we observe the sea water moving both upwards and downwards at rates varying from place to place. Such a variation in sea level occurs from hour to hour and from day to day. At the time of arising sea level, the incoming tide towards the land is spoken of as a flow tide or a flood tide.
  • At the time of a falling sea level after a few hours, we speak of the tide water going out or withdrawn, is an ebb tide (low tide). The flood tide is a high tide and the ebb tide is a low tide.
  • Tides are really the largest waves keeping the ocean water restless. Twice a day regularly at constant intervals, a tide flows in and twice a day it ebbs away. Twice a month, flow tides are higher and the ebb tides are lower than the average. Also twice a month flow tides are lower and the ebb tides are higher than the average.
  • The factors responsible for bringing about such a variation in the regulation and the size of tides are:
    • The location of the sun, the moon and the earth in relation to each other which is rarely in a straight line.
    • The distances of the sun and the moon from the earth are not constant.
    • Our globe is not entirely covered with water.
    • The outline or shape of the coast may help or hinder the tides.
  • Still the tides follow each other with a great punctuality at any given coast.

Forces that generate the tides

  • The earth attracts and is also attracted by the sun, the moon and by other planetary bodies. It is called the gravitational force and it operates between the sun, moon and the earth. It sets the ocean waters in motion producing a tidal current. Tides are the proof of such a gravitational pull.
  • The moon and the sun both exert their gravitational force on the earth. The Oceans, Submarine Relief and Circulation sun which is bigger in mass than the moon is also at a greater distance from the earth than the moon. Therefore,the gravitational attraction of the moon is more effective on the earth than the gravitational attraction of the sun.
  • Since the water is liquid and mobile, its bulging in the direction facing the moon is easily noticed, yet a lower tidal bulge also develops on the other side of the earth farther from the moon because of moon’s least attraction.

Spring and Neap Tides

  • The moon, as it is closer to the earth, exerts twice the gravitational pull of the sun on the earth. When the sun and the moon are in a line as on a new moon (Amavasya) or a full moon day (Purnima) both of them pull together at the same time in the same direction. This combined pull produces an extra-large tide. It is called a spring tide.
  • In its first quarter (Asthmi Shukla Paksha) and the third quarters (Asthmi-Krishna Paksha) the gravitational force of the two heavenly bodies is at right angle. At this time, the two pulls are opposing each other and are not acting in the same direction. In other words they cancel or neutralize each other’s effect. It produces a weak tide which is called a neap tide.

Effect of Tides

  • Tides act as link between the port and the open sea. Some of the major ports of the world, such as London port on the river Thames and Kolkata port on river Hugli are located on the rivers away from the sea coast.
  • The tidal current clear away the river sediments and slows down the growth of delta. It increases the depth of water which helps ships to move safely to the ports.
  • It also acts as a source for producing electricity.

Currents

  • The ocean currents are horizontal flow of a mass of waters in a fairly defined direction over great distances. They are like stream of water flowing through the main body of the ocean in a regular pattern. The average speed of currentis between 3.2 km to 10 kms per hour.
  • Ocean currents with higher speed are called stream and currents with lower speed are called drift.
  • Ocean currents can be broadly divided into:
  • Those currents which flow from equatorial regions towards poles have a higher surface temperature and are called warm current.
  • Those currents which flow from Polar Regions towards equator have a lower surface temperature and are called cold currents.
  • The origin and the nature of circulation of the ocean currents depend on the following factors:

Differences in Density

  • The sea water’s density varies from place to place according to its temperature and proportion of salinity. The higher the temperature of water, the lesser will be the density. Hence the less dense water of the equator moves towards the poles while the cold and dense waters of the poles move towards the equator. Thus cold currents always move from the poles to the equator while the warm currents move from equator towards the poles.
  • Currents are also produced by changes in the salinity of ocean waters. If the salinity of the water is more, the density of the water increases, and the water sinks. Hence water with Lower salinity flows on the surface of the high salinity water while an under-current of high salinity flows towards the less dense water. The currents caused by difference in salinity are found between the Atlantic Ocean with lower salinity and the Mediterranean Sea with higher salinity.

Earth’s Rotation

  • The earth’s rotation deflects air to its right in the northern hemisphere and to its left in the southern hemisphere. Similarly, ocean water is also affected by Coriolis force and follows the Ferrel’s Law.
  • So all the ocean currents follow clockwise direction in the northern hemisphere and anticlockwise direction in the southern hemisphere.

Planetary Winds

  • The planetary winds like the trade winds and westerlies drive the ocean water in a steady flow in front of them. If we compare the world map of planetary wind system, with that of the ocean currents it will be clear that currents follow the main direction of the planetary wind system.
  • In low latitudes or in the region of the trade winds the ocean currents change their direction according to the change in the direction of summer and winter monsoon winds.

Currents of the Indian Ocean

  • The general pattern of circulation in the southern section of the Indian Ocean is anti clockwise as that of other oceans. But in the northern section there is a clear reversal of currents in winter and summer. These are completely under the influence of the seasonal changes of the monsoon winds. So there is a clear reversal of currents in the winter and summer season i.e/southwestwards during the north-east Monsoon, north-eastwards during the southwest Monsoon and variable during transition season.
  • During winters Srilanka divides the currents of the Arabian Sea from those of the Bay of Bengal. The North Equatorial Current flows westward just south of Srilanka with distinct counter equatorial current flows between itand the South Equatorial Current.
  • At this time in the northern section, the whole of Bay of Bengal and Arabian Sea is under the influence of North East Monsoon. The North East Monsoon drives the water of Bay of Bengal and Arabian Sea west wards to circulate in an anti-clockwise direction. This current is known as North East Monsoon Drift.
  • In summers, the northern section comes under the influences of South West Monsoon. There is an easterly movement of water in the Bay of Bengal and Arabian Sea and produces a clockwise circulation. This current is known as South West Monsoon Drift. In general the summer currents are more regular than those of winter.
  • In the southern Indian Ocean, the South Equatorial Current, strengthened by its corresponding current of the Pacific Ocean, flows from east to west. It turns south-wards along the Coast of Mozambique in Africa. A part of this current which flows between the mainland and the Madagascar Island is known as warm Mozambique Current. After the confluence of these twocurrents, it is called Aghulas Current. It then turns eastwards and merges with the West Wind Drift.
  • The West Wind Drift flows across the ocean in west east direction in the higher latitudes to reach the southern tip of Australia. A branch of this stream turns north to flow along the western coast of Australia as cold West Australian Current. West Australian Current later joins the South Equatorial Current to complete the circuit.

Currents of the Atlantic Ocean

  • To the north and south of equator there are two westward moving currents i.e., the north and south equatorial currents. Between these two equatorial currents is the Counter Equatorial Current which flows from west to east. This counter current replaces the water removed from the eastern side of the oceans by North and South Equatorial Currents.
  • The South Equatorial Current bifurcates into two branches near the Cape De Sao Roque in Brazil. Its northern branch joins the North Equatorial Current. This combined current enters the Caribbean Sea and the Gulf of Mexico, while the remaining current passes along the eastern side of the West Indies as the Antilles Current. The part of the current which enters the Gulf of Mexico, comes out from the Florida strait and joins the Antilles Current. This combined current moves along the south eastern coast of U.S.A.. It is known as Florida Current upto cape of Hatteras. Beyond the Cape Hatteras, upto the Grand Banks, off New Foundland, it is called the Gulf Stream. From the Grand Banks, the Gulf Stream is deflected eastwards under the combined influence of the westerlies and the rotation of the earth. It crosses the Atlantic Ocean as North Atlantic Drift.
  • The North Atlantic Drift bifurcates into two branches on reaching the eastern part of the ocean. The northern branch continues as North Atlantic Drift; reaches the British Isles from where it flows along the coast of Norway as the Norwegian Current and enters the Arctic Ocean. The southern branch flows between Spain and Azores Island as the cold Canaries Current. The Canaries Current finally joins the North Equatorial Current and completes the circuit in the North Atlantic Ocean. Within this circuit lies the Sargasso Sea which is full of large quantities of seaweeds called sargassum, a brown algae.
  • Apart from the clockwise circulation of the currents in the North Atlantic Ocean, there are also two cold currents - the East Greenland Current and the Labrador Current which flow from the Arctic Ocean into the Atlantic Ocean. The Labrador Current flows along the eastern coast of Canada and meets the warm Gulf Stream. The confluence of these two currents, one cold and the other hot, produces fog around Newfoundland and makes it the most important fishing ground of the world. East Greenland current flows between Iceland and Greenland and cools the North Atlantic Drift at the point of their confluence.
  • The northern branch of the South Equatorial Current joins the North Equatorial Current, whereas the southern branch turns south and flows along the eastern coast of South America as Brazil Current. At about 35° south latitude the influence of the westerlies and the rotation of the earth propel the current eastward to merge with the West Wind Drift.
  • Near the Cape of Good Hope, the South Atlantic Current is diverted northward as the cold Benguela Current. It finally joins the South Equatorial Currents thus completing the circuit. Another cold current, known as the Falkland Current, flows along the South eastern coast of South America from south to north.

Currents of the Pacific Ocean

  • In the Equatorial belt of the Pacific Ocean, two streams of equatorial currents flow across the ocean from the Central American Coast. Between these two - the North Equatorial Current and the South Equatorial Current flows a Counter Equational current moves west to east. The North Equatorial Current turns northwards and flows along the Philippines Islands, Taiwan and Japan to form the warm Kuro Shio or Kuro Siwo current. From the southeast coast of Japan, the current comes under the influence of westerlies and flows right across the ocean as North Pacific Current. After reaching the west coast of North America, it bifurcates into two branches. The northern branch flows anti clockwise along the coast of British Columbia and Alaska and is known as the Alaska Current. The warm waters of this current help to keep the Alaska coast ice free in winter.
  • The other branch of the North Pacific Current moves southward along the coast of California as the Cold Californian Current. It eventually joins the North Equatorial Current to complete its circuit. In the northern part of the Pacific Ocean two cold currents also flow. These are the Oya Siwo Current and Okhotsk Current. The cold Oya Siwo Current flows along the coast of the Kamchatka Peninsula. Another cold current, Okhotsk Current flows past Sakhalin to merge with the Oya Siwo Current near Hokkaido Island. It later merges with Kuro Siwo Current and sinks beneath the warm waters of the North Pacific Currents.
  • In the South Pacific Ocean, the South Equatorial Current flows towards west and turns southwards as the East Australian Current. It then meets near Tasmania the cold South Pacific Current which flows from west to east. On reaching the South Western Coasts of South America, it turns north wards as the cold Peru Current. It then meets the South Equatorial Current and completes the circuit. The cold waters of the Peru Current are partly responsible for making the coast of northern Chile and western Peru with very scanty rainfall.

Global ocean currents

Thermohaline circulation

GK through MAP (Snippets)

Agro-Climatic Zones in Utter Pradesh

Agro-Climatic Zones in Utter Pradesh

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90 Days Planner (Day 28 Geography)

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