{"id":118739,"date":"2022-04-28T13:13:31","date_gmt":"2022-04-28T07:43:31","guid":{"rendered":"https:\/\/www.mapsofindia.com\/my-india\/?p=118739"},"modified":"2022-04-28T13:13:31","modified_gmt":"2022-04-28T07:43:31","slug":"chapter-4-distribution-of-oceans-and-continents-questions-and-answers-ncert-solutions-for-class-11-geographyfundamentals-of-physical-geography","status":"publish","type":"post","link":"https:\/\/www.mapsofindia.com\/my-india\/education\/chapter-4-distribution-of-oceans-and-continents-questions-and-answers-ncert-solutions-for-class-11-geographyfundamentals-of-physical-geography","title":{"rendered":"Chapter 4 – Distribution of Oceans and Continents Questions and Answers: NCERT Solutions for Class 11 Geography(Fundamentals of Physical Geography)"},"content":{"rendered":"

1. Multiple choice questions<\/h3>\n

Question 1(i).
\nWho amongst the following was the first to consider the possibility of Europe, Africa and America having been located side by side?
\n(\u0430) Alfred Wegener
\n(b) Antonio Pellegrini
\n(c) Abraham Ortelius
\n(d) Edmond Hess.<\/h2>\n

Answer:
\n(c) Abraham Ortelius<\/h3>\n

Question 1(ii).
\nPolar fleeing force relates to:
\n(a) Revolution of the Earth
\n(b) Gravitation
\n(c) Rotation of the earth
\n(d) Tides.<\/h2>\n

Answer:
\n(c) Rotation of the earth<\/h3>\n

Question 1(iii).
\nWhich one of the following is not a minor plate?
\n(a) Nazca
\n(b) Arabia
\n(c) Philippines
\n(d) Antarctica.<\/h2>\n

Answer:
\n(d) Antarctica<\/h3>\n

Question 1(iv).
\nWhich one of the following facts was not considered by those while discussing the concept of sea floor spreading?
\n(a) Volcanic activity along the mid- oceanic ridges
\n(b) Stripes of normal and reverse magnetic field observed in rocks of ocean floor
\n(c) Distribution of fossils in different continents
\n(d) Age of rocks from the ocean floor.<\/h2>\n

Answer:
\n(c) Distribution of fossils in different continents<\/h3>\n

Question 1(v).
\nWhich one of the following is the type of plate boundary of the Indian plate along the Himalayan Mountains?
\n(\u0430) Ocean-continent convergence
\n(b) Divergent boundary
\n(c) Transform boundary
\n(d) Continent-continent convergence.<\/h2>\n

Answer:
\n(d) Continent-continent convergence.<\/h3>\n

2. Answer the following questions in about 30 words.
\nQuestion 2(i).
\nWhat were the forces suggested by Wegener for the movement of the continents?<\/h2>\n

Answer:
\nWegener suggested that the movement responsible for the drifting of the continents was caused by two forces.
\nPole-fleeing force and
\nTidal force.
\nThe polar-fleeing force relates to the rotation of the earth. The earth is not a perfect sphere; it has a bulge at the equator. This bulge is due to the rotation of the earth.
\nThe tidal force is due to the attraction of the moon and the sun that develops tides in oceanic waters. Wegener believed that these forces would become effective when applied over many million years.<\/h3>\n

Question 2(ii).
\nHow are the convectional currents in the mantle initiated and maintained?<\/h2>\n

Answer:
\nArthur Holmes in 1930s discussed the possibility of convection currents operating in the mantle portion. These currents are generated due to radioactive elements causing thermal differences in the mantle portion. According to Holmes, there exists a system of such currents in the entire mantle portion. This was an attempt to provide an explanation to the issue of force, on the basis of which contemporary scientists discarded the continental drift theory.<\/h3>\n

Question 2(iii).
\nWhat is the major difference between the transform boundary and the convergent or divergent boundaries of plates?<\/h2>\n

Answer:
\nThe major difference between the transform boundary and the convergent or divergent boundaries of plates are as follows:
\nTransform Boundaries: Where the crust is neither produced nor destroyed as the plates slide horizontally past each other.
\nConvergent Boundaries: Where the crust is destroyed as one plate dived under another, it is called convergent boundaries.
\nDivergent Boundaries: Where new crust is generated as the plates pull away from each other, these are called divergent boundaries.<\/h3>\n

Question 2(iv).
\nWhat was the location of the Indian landmass during the formation of the Deccan Traps?<\/h2>\n

Answer:
\nAbout 140 million years before the present, the subcontinent was located as south as 50\u00b0S latitude. During the movement of the Indian plate towards the Asiatic plate, a major event that occurred was the outpouring of lava and formation of the Deccan Traps. This started somewhere around 60 million years ago and continued for a long period of time. Note that the subcontinent was still close to the equator. From 40 million years ago and thereafter, the event of formation of the Himalayas took place. Scientists believe that the process is still continuing and the height of the Himalayas is rising even to this date.
\n3. Answer the following questions in about 150 words.<\/h3>\n

Question 3(i) .
\nWhat are the evidences in support of the continental drift theory?<\/h2>\n

Answer:
\nA variety of evidence was offered in support of the continental drift. Some of these are given below:
\n1. The Matching of Continents (Jig-Saw-Fit): The shorelines of Africa and South America facing each other have a remarkable and unmistakable match.
\n2. Rocks of Same Age Across the Oceans: The belt of ancient rocks of 2,000 million years from Brazil coast matches with those from western Africa. The earliest marine deposits along the coastline of South America and Africa are of the Jurassic age. This suggests that the ocean did not exist prior to that time.
\n3. Tillite: It is the sedimentary rock formed out of deposits of glaciers. The Gondawana system of sediments from India is known to have its counter parts in six -different landmasses of the Southern Hemisphere. At the base the system has thick tillite indicating extensive and prolonged glaciation. Counter parts of this succession are found in Africa, Falkland Island, Madagascar, Antarctica and Australia besides India. Overall resemblance of the Gondawana type sediments clearly demonstrates that these landmasses had remarkably similar histories. The 45 glacial tiilite provides unambiguous evidence of palaeoclimates and also of drifting of continents.
\n4. Placer Deposits: The occurrence of rich placer deposits of gold in the Ghana coast and the absolute absence of source rock in the region is an amazing fact. The gold bearing veins are in Brazil and it is obvious that the gold deposits of the Ghana are derived from the Brazil . plateau when the two continents lay side by side.
\n5. Distribution of Fossils: The observations that Lemurs occur in India, Madagascar and Africa led some to consider a contiguous landmass \u201cLemuria\u201d linking these three landmasses. Mesosaurus was a small reptile adapted to shallow brackish water. The skeletons of these are found only in two localities : the Southern Cape province of South Africa and Iraver formations of Brazil. The two localities presently are 4,800 km apart with an ocean in between them.<\/h3>\n

Question 3(ii).
\nBring about the basic difference between the drift theory and Plate tectonics.<\/h2>\n

Answer:
\nDrift theory: Alfred Wegener a German meteorologist put forth \u201cthe continental drift theory\u201d. According to him, all continents formed a single continental mass called PANGAEA All oceans formed a single universal ocean called PANTHALASSA. He argued that, around 200 million years ago, the super continent, Pangaea, began to split. Pangaea first broke into two large continental masses as Laurasia and Gondwanaland forming the northern and southern components respectively. Subsequently, Laurasia and Gondwan al and continued to break into various smaller continents that exist today.
\nPlate Tectonics: This theory emerged in 1967, by McKenzie and Parker and also Morgan. A tectonic plate is also called lithospheric plate. It is a massive, irregularly-shaped slab of solid rock, generally composed of both continental and oceanic lithosphere. Plates move horizontally over the asthenosphere as rigid units. The lithosphere includes the crust and top mantle with its thickness range varying between 5-100 km in oceanic parts and about 200 km in the continental areas. Pacific plate is largely an oceanic plate whereas the Eurasian plate may be called a continental plate. The theory of plate tectonics proposes that the earth\u2019s lithosphere is divided into seven major and some minor plates.<\/h3>\n

Question 3(iii).
\nWhat were the major post-drift discoveries that rejuvenated the interest of scientists in the study of distribution of oceans and continents?<\/h2>\n

Answer:
\nA number of discoveries during the post\u00acwar period added new information to geological literature. Particularly, the information collected from the ocean floor mapping provided new dimensions for the study of distribution of oceans and continents.
\nThese currents are generated due to radioactive elements causing thermal differences in the mantle portion. Holmes argued that there exists a system of such currents in the entire mantle portion. This was an attempt to provide an explanation to the issue of force, on the basis of which contemporary scientists discarded the continental drift theory.
\nDetailed research of the ocean configuration revealed that the ocean floor is not just a vast plain but it is full of relief.
\nExpeditions to map the oceanic floor in the post-war period provided a detailed picture of the ocean relief and indicated the existence of submerged mountain ranges as well as deep trenches, mostly located closer to the continent margins.
\nThe mid-oceanic ridges were found to be most active in terms of volcanic eruptions. The dating of the rocks from the oceanic crust revealed the fact that they are much younger than the continental areas.
\nRocks on either side of the crest of oceanic ridges and having equi-distant locations from the crest were found to have remarkable similarities both in terms of their constituents and their age.<\/h3>\n

Multiple Choice Questions<\/h3>\n

Question 1.
\nName the smallest continent.
\n(a) Asia
\n(b) Europe
\n(c) Africa
\n(d) Australia.<\/h2>\n

Answer:
\n(d) Australia.<\/h3>\n

Question 2.
\nWho was the profbunder of plate tectonic theory?
\n(a) Arthur Holmes
\n(b) McKenzie, Parker and Morgan
\n(c) Admans Heinz
\n(d) Alfred Wegener.<\/h2>\n

Answer:
\n(b) McKenzie, Parker and Morgan<\/h3>\n

Question 3.
\nWho was the profounder of convection currents theory?
\n(a) Arthur Holmes
\n(b) McKenzie, Parker and Morgan
\n(c) Admans Heinz
\n(d) Alfred Wegener.<\/h2>\n

Answer:
\n(a) Arthur Holmes<\/h3>\n

Question 4.
\n(iii) Pacific Ocean zone is also called:
\n(a) Ring of Fire
\n(b) Ball of Fire
\n(c) Fire rain area
\n(d) Volcanic area.<\/h2>\n

Answer:
\n(a) Ring of Fire<\/h3>\n

Question 5.
\nWhich country has gold bearing veins?
\n(a) Australia
\n(b) Russia
\n(c) Brazil
\n(d) South Africa.<\/h2>\n

Answer:
\n(c) Brazil<\/h3>\n

Question 6.
\nBy which method have facilitated correlating the rock formation from different continents across oceans?
\n(a) The radiometric dating methods
\n(b) Carbon 14 method
\n(c) Radioactive method
\n(d) Fling Method.<\/h2>\n

Answer:
\n(a) The radiometric dating methods<\/h3>\n

Question 7.
\nThe ocean floor may be segmented into how many divisions based on the depth as well as the forms of relief?
\n(a) Three
\n(b) Four
\n(c) Five
\n(d) Seven.<\/h2>\n

Answer:
\n(a) Three<\/h3>\n

Question 8.
\nWhat per cent of the earth is covered with land and water respectively?
\n(a) 29% of the earth is covered with land and 71% is covered with water.
\n(b) 71% of the\u2019earth is covered with land and 29% is covered with water.
\n(c) 36% of the earth is covered with land and 64% is covered with water.
\n(d) 64% of the earth is covered with land and 36% is covered with water.<\/h2>\n

Answer:
\n(a) 29% of the earth is covered with land and 71% is covered with water.<\/h3>\n

Question 9.
\nWhat was the name given by Alfred Wegener to a large continent surrounded with water?
\n(a) Pangaea
\n(b) Panthalassa
\n(c) Angaraland
\n(d) Gondwanaland.<\/h2>\n

Answer:
\n(a) Pangaea<\/h3>\n

Question 10.
\nWho was the profounder of continental drift theory?
\n(\u0430) Arthur Holmes
\n(b) McKenzie, Parker and Morgan
\n(c) Admans Heinz
\n(d) Alfred Wegener.<\/h2>\n

Answer:
\n(d) Alfred Wegener.<\/h3>\n

Question 11.
\nWhat was the name given to massive ocean by Wegener?
\n(a) Pangaea
\n(b) Panthalassa
\n(c) Angara land
\n(d) Gondwanaland.<\/h2>\n

Answer:
\n(b) Panthalassa<\/h3>\n

Question 12.
\nAccording to Wegener, Pangaea was divided into land forms namely:
\n(a) Panthalassa and Angara Land
\n(b) Lurasia and Gondwanaland
\n(c) Livasa and Continent
\n(d) Oceans and Continents.<\/h2>\n

Answer:
\n(b) Lurasia and Gondwanaland.<\/h3>\n

Very Short Answer Type Questions<\/h3>\n

Question 1.
\nWhat was the theory\u2019 profounded by Alfred Wegener, a German meteorologist? With what principle was it associated?<\/h2>\n

Answer:
\nAlfred Wegener, a German meteorologist put forth a comprehensive argument in the form of \u201cthe continental drift theory\u201d in 1912. This was regarding the distribution of the oceans and the continents.<\/h3>\n

Question 2.
\nWhich methods that developed in the recent period have facilitated correlating the rock formation from different continents across the vast ocean?<\/h2>\n

Answer:
\nThe radiometric dating methods developed in the recent period have facilitated correlating the rock formation from different continents across the vast ocean.<\/h3>\n

Question 3.
\nWhat are Abyssal Plains?<\/h2>\n

Answer:
\nThese are extensive plains that lie between the continental margins and mid-oceanic ridges. The Abyssal plains are the areas where the continental sediments that move beyond the margins get deposited.<\/h3>\n

Question 4.
\nWhat are Continental Margins?<\/h2>\n

Answer:
\nThese form the transition between continental shores and deep-sea basins. They include continental shelf, continental slope, continental rise and deep-oceanic trenches.<\/h3>\n

Question 5.
\nWhat are convection currents?<\/h2>\n

Answer:
\nConvection currents are generated due to radioactive elements causing thermal differences in the mantle portion.<\/h3>\n

Question 6.
\nWhat was the condition of India when Pangaea broke? Before that what was the status of India?<\/h2>\n

Answer:
\nIndia was a large island situated off the Australian coast, in a vast ocean. The Tethys sea separated it from the Asian continent till about 225 million years ago. India is supposed to have started her northward journey about 200 million years ago at the time when Pangaea broke. India collided with Asia about 40\u00ac50 million years ago causing rapid uplift of the Himalayas.<\/h3>\n

Question 7.
\nHow was Himalaya formed?<\/h2>\n

Answer:
\nIndia started her northward journey about 200 million years ago at the time when Pangaea broke. India collided with Asia about 40-50 million years ago causing rapid uplift of the Himalayas.<\/h3>\n

Question 8.
\nHow was Deccan Traps formed?<\/h2>\n

Answer:
\nDuring the movement of the Indian plate towards the Asiatic plate, a major event that occurred was the outpouring of lava. It led to formation of the Deccan Traps. This started somewhere around 60 million years ago and continued for a long period of time.<\/h3>\n

Question 9.
\nWhat was emphasised by the sea floor spreading and tectonic plates theory?<\/h2>\n

Answer:
\nIt emphasised that the earth is divided into plates and these plates have been constantly moving over the globe throughout the history of the earth. It is not the continent that moves as believed by Wegener. Continents are part of a plate and what moves is the plate. All the plates, without exception, have moved in the geological past, and shall continue to move in the future as well.<\/h3>\n

Question 10.
\nWhat are the different ways in which convergence can take place?<\/h2>\n

Answer:
\nThere are three ways in which convergence can occur.
\nThese are:
\n1. between an oceanic and continental plate;
\n2. between two oceanic plates; and
\n3. between two continental plates.<\/h3>\n

Question 11.
\nWho was the profounder of plate tectonic theory?<\/h2>\n

Answer:
\nMcKenzie Parker and Morgan<\/h3>\n

Question 12.
\nWho was the profounder of convection currents theory?<\/h2>\n

Answer:
\nArthur Holmes<\/h3>\n

Question 13.
\nAccording to Wegener, what are the causes of drifting of continents?<\/h2>\n

Answer:
\nTwo causes were responsible for the drifting of the continents:
\nPole-fleeing force and
\nTidal force.<\/h3>\n

Question 14.
\nIn how many plates has earth been divided according to plate tectonic theory?<\/h2>\n

Answer:
\nAccording to this theory, the earth has been divided into seven major and some minor plates.<\/h3>\n

Question 15.
\nGive examples of placer deposits.<\/h2>\n

Answer:
\nThe occurrence of rich placer deposits of gold in the Ghana coast and the gold bearing veins in Brazil are examples of placer deposits.<\/h3>\n

Question 16.
\nWith what is fleeing force related?<\/h2>\n

Answer:
\nThe polar-fleeing force relates to the rotation of the earth. The earth is not a perfect sphere; it has a bulge at the equator. This bulge is due to the rotation of the earth.<\/h3>\n

Question 17.
\nWith what is tidal force related?<\/h2>\n

Answer:
\nIt is related to the attraction of the moon and the sun that develops tides in oceanic waters. Wegener believed that these forces would become effective when applied over many million years.<\/h3>\n

Question 18.
\nOn what basis has continent drifting theory been discarded?<\/h2>\n

Answer:
\nArthur Holmes in 1930s discussed the possibility of convection currents operating in the mantle portion. These currents are generated due to radioactive elements causing thermal differences in the mantle portion. Holmes argued that there exists a system of such currents in the entire mantle portion. This was an attempt to provide an explanation to the issue of force, on the basis of which contemporary scientists discarded the continental drift theory.<\/h3>\n

Question 19.
\nThe ocean floor may be segmented into howr many di visions based on the depth as well as the forms of relief?<\/h2>\n

Answer:
\nThe ocean floor may be segmented into three major divisions based on the depth as well as the forms of relief. These divisions are:
\ncontinental margins,
\ndeep-sea basins and
\nmid-oceanic ridges.<\/h3>\n

Question 20.
\nWhat are mid-oceanic ridges?<\/h2>\n

Answer:
\nThis forms an interconnected chain of mountain system within the ocean. It is the longest mountain-chain on the surface of the earth though submerged under the oceanic water. It is characterised by a central rift system at the crest, a fractionated plateau and flank zone all along its length. The rift system at the crest is the zone of intense volcanic activity.<\/h3>\n

Question 21.
\nWhich fact helped the scientists to understand plate movement?<\/h2>\n

Answer:
\nThe rocks equidistant on either sides of the crest of mid-oceanic ridges show remarkable similarities in terms of period of formation, chemical compositions and magnetic properties. Rocks closer to the mid-oceanic ridges have normal polarity and are the youngest. The age of the rocks increases as one moves away from the crest.<\/h3>\n

Short Answer Type Questions<\/h3>\n

Question 1.
\nExplain the movement in Indian plate.<\/h2>\n

Answer:
\nThe Indian plate includes Peninsular India and the Australian continental portions. The Tethys Sea separated it from the Asian continent till about 225 million years ago. India is supposed to have started her northward journey about 200 million years ago at the time when Pangaea broke. India collided with Asia about 40-50 million years ago causing rapid uplift of the Himalayas. About 140 million years before the present, the subcontinent was located as south as 50\u00b0S. latitude.
\nThe two major plates were separated by the Tethys Sea and the Tibetan block was closer to the Asiatic landmass. During the movement of the Indian plate towards the Asiatic plate, a major event that occurred was the outpouring of lava and formation of the Deccan Traps. This started somewhere around 60 million years ago and continued for a long period of time. The subcontinent was still close to the equator. From 40 million years ago and thereafter, the event of formation of the Himalayas took place. Scientists believe that the process is still continuing and the height of the Himalayas is rising even to this date.<\/h3>\n

Question 2.
\nExplain the hypothesis, known as the \u201csea floor spreading\u201d given by Hess.<\/h2>\n

Answer:
\nHess argued that constant eruptions at the crest of oceanic ridges cause the rupture of the oceanic crust forces and the new lava wedges into it, pushing the oceanic crust on either side. The ocean floor, thus spreads. Two facts made Hess think about the consumption of the oceanic crust.
\nThe younger age of the oceanic crust
\nThe spreading of one ocean does not cause the shrinking of the other.
\nHe further maintained that the ocean floor that gets pushed due to volcanic eruptions at the crest, sinks down at the oceanic trenches and gets consumed. The basic concept of sea floor spreading has been depicted in the given figure:<\/h3>\n

\"\"<\/p>\n

Question 3.
\nExplain the distribution of earthquake and volcanic plate on the earth,<\/h2>\n

Answer:
\nEarthquake and Volcanic plate:
\n1. It goes from Atlantic Ocean almost parallel to the coastlines. It further extends into the Indian Ocean. It bifurcates a little south of the Indian subcontinent with one branch moving into East Africa and the other meeting a similar line from Myanmar to New Guiana.
\n2. Another area of concentration coincides with the Alpine-Himalayan system and the rim of the Pacific Ocean. In general, the foci of the earthquake in the areas of mid-oceanic ridges are at shallow depths whereas along the Alpine-Himalayan belt as well as the rim of the Pacific, the earthquakes are deep-seated ones. The map of volcanoes also shows a similar pattern. The rim of the Pacific is also called rim of fire due to the existence of active volcanoes in this area.<\/h3>\n

Question 4.
\nWhat information do we get from the mapping of the ocean floor and palaeomagnetic studies of rocks from oceanic regions?<\/h2>\n

Answer:
\nThe mapping of the ocean floor and palaeomagnetic studies of rocks from oceanic regions gave following information:
\nAlong the mid-oceanic ridges, volcanic eruptions are common and they bring huge amounts of lava to the surface in this area.
\nThe rocks equidistant on either sides of the crest of mid-oceanic ridges show remarkable similarities in terms of period of formation, chemical compositions and magnetic properties.
\nThe ocean crust rocks are much younger than the continental rocks. The age of rocks in the oceanic crust is nowhere more than 200 million years old. Some of the continental rock formations are as old as 3,200 million years.
\nThe sediments on the ocean floor are unexpectedly very thin. Scientists expected that if the ocean floors were as old as the continent, to have a complete sequence of sediments for a period of much longer duration. However, nowhere was the sediment column found to be older than 200 million years.
\nThe deep trenches have deep-seated earthquake occurrences while in the mid-oceanic ridge areas, the quake foci have shallow\u2019 depths.<\/h3>\n

Question 5.
\nExplain the basic concept of continental drift theory.<\/h2>\n

Answer:
\nAlfred Wegener, a German meteorologist, put forth a comprehensive argument in the form of \u201cthe continental drift theory\u201d in 1912. This was regarding the distribution of the oceans and the continents. According to Wegener, all the continents formed a single continental mass and mega ocean surrounded the same. He called the super continent as PANGAEA, meaning all earth. He named mega ocean as PANTHALASSA, meaning all water. According to him. around 200 million years ago, the super continent, Pangaea, began to split. Pangaea first broke into two large continental masses as Laurasia and Gondwanaland forming the northern and southern components respectively. Subsequently, Laurasia and Gondwanalan d continued to break into various smaller continents that exist today. A variety of evidence was offered in support of the continental drift.<\/h3>\n

Question 6.
\nExplain different types of boundaries that form as a result of tectonic plates.<\/h2>\n

Answer:
\nThree types of boundaries are formed as a result of tectonic plates:
\nConvergent Boundaries: Where the crust is destroyed as one plate dived under another, it is called convergent boundaries.
\nDivergent Boundaries: Where new crust is generated as the plates pull away from each other, these are called divergent boundaries.
\nTransform Boundaries: Where the
\ncrust is neither produced nor destroyed as the plates slide horizontally past each other. ,<\/h3>\n

Long Answer Type Questions<\/h3>\n

Question 1.
\nAccording to tectonic plates theory in how many plates has the earth been divided? Explain.<\/h2>\n

Answer:
\nThe theory of plate tectonics proposes that the earth\u2019s lithosphere is divided into seven major and some minor plates. The major plates are as follows:
\nAntarctica and the surrounding oceanic plate
\nNorth American plate
\nSouth American plate
\nPacific plate
\nIndia-Australia-New Zealand plate
\nAfrica with the eastern Atlantic floor plate
\nEurasia and the adjacent oceanic plate. Some important minor plates are:
\nCocos plate: It is between Central America and Pacific plate
\nNazca plate: It is between South America and Pacific plate
\nArabian plate: It includes mostly the Saudi Arabian landmass
\nPhilippine plate: It is between the Asiatic and Pacific plate
\nCaroline plate: It is between the Philippine and Indian plate (North of New Guinea)
\nFuji plate: It includes North-east of Australia.
\nPacific plate is largely an oceanic plate whereas the Eurasian plate may be called a continental plate. Plates are not static. Plates may converge or diverge. Plates may break as well.<\/h3>\n

Question 2.
\nExplain tectonic plate theory and its j working.<\/h2>\n

Answer:
\nThese plates have been constantly moving over the globe throughout the history of the earth.
\nThe theory of plate tectonics was introduced by Mckenzie, Parker and , Morgan in 1967.
\nA tectonic plate is also called as lithosphere plate.
\nIt is a massive irregularly shaped slab of solid rock.
\nConsists of oceanic and continental sphere.
\nPlates move horizontally over the asthenosphere.
\nAverage thickness is 100 km of oceanic part and 200 km of continental part.
\nIt may be oceanic or continental.
\nPacific plate is largest oceanic plate whereas Eurasian plate is the largest continental plate.
\nThese plates are moving constantly throughout geological time not the continent, believed by Wegener.
\nIt creates three types of boundaries.
\n1. Divergent boundaries
\nNew crust is generated
\nPlates move away from each other
\nThese are called spreading sites
\nEx. Mid atlantic ridge
\n2. Convergent boundaries |
\nCrust is destroyed
\nSinking of plate is called \u201csubduction zone\u201d. There are three ways in which subduction occurs (i) between an oceanic and continental plates; (ii) between two oceanic plates; and (iii) between two continental plates.
\nTransform boundaries: Where the crust is neither produced nor destroyed as the plates slide horizontally past each other.<\/h3>\n

Question 3.
\nExplain important theories associated with the movement of continents.<\/h2>\n

Answer:
\nContinental drift: Abraham Ortelius a Dutch map maker in 1596 first proposed the possibility of joining the continents such as America with Europe and Africa. Antonio Pellegrini drew a map showing the three continents together. Alfred Wegener, a German meteorologist put forth the continental drift theory. According to him, all continents formed a single continental mass called Pangaea.
\nAll oceans formed a single universal ocean called Panthalassa around 200 million years ago. The Pangaea began to split into two large continental masses called Laurasia and Gondwanaland. By further splitting Laurasia formed northern continents and Gondwanaland formed southern continents.
\nSea Floor Spreading: The deep trenches have deep-seated earthquake occurrences while in the mid- oceanic ridge areas, the quake foci have shallow depths. These facts and a detailed analysis of magnetic properties of the rocks on either sides of the mid-oceanic ridge led Hess in 1961 to propose his hypothesis. It was called the \u201csea floor spreading\u201d. Hess argued that constant eruptions at the crest of oceanic ridges cause the rupture of the oceanic crust forces and the new lava wedges into it, pushing the oceanic crust on either side. The ocean floor, thus spreads. Two facts made Hess think about the consumption of the oceanic crust.
\nThe younger age of the oceanic crust.
\nThe spreading of one ocean does not cause the shrinking of the other.
\nHe further maintained that the ocean floor that gets pushed due to volcanic eruptions at the crest, sinks down at the oceanic trenches and gets consumed. Plate Tectonics: It was in 1967, McKenzie and Parker and also Morgan, independently collected the available ideas and came out with another concept termed Plate Tectonics. The theory of plate tectonics proposes that the earth\u2019s lithosphere is divided into seven major and some minor plates. These plates have been constantly moving over the globe throughout the history of the earth. It is not the continent that moves as believed by Wegener. Continents are part of a plate and what moves is the plate. All the plates, without exception, have moved in the geological past, and shall continue to move in the future as well.<\/h3>\n

Question 4.
\nThe ocean floor may be segmented into how many divisions based on the depth as well as the forms of relief?<\/h2>\n

Answer:
\nThe ocean floor may be segmented into three major divisions based on the depth as well as the forms of relief. These divisions are:
\n(i) Continental margins,
\n(ii) Abyssal plains and
\n(iii) Mid-oceanic ridges.
\n1. Continental margins
\nForm transitional zone between continental shore and deep sea basins
\nThey include continental slope , shelf, continental rise and deep oceanic trenches
\n2. Abyssal plains
\nExtensive plains
\nFound between continental margin and mid oceanic ridge
\nContinental sediments get deposited
\n3. Mid-oceanic ridges
\nDistribution of volcanoes and earthquakes
\nAll volcanoes and earthquakes are parallel to the coast
\nThis line also co-incides with mid- Atlantic ridge and Alpine Himalayan system
\nAround the Pacific Ocean it is called ring of fire mid oceanic ridges.<\/h3>\n","protected":false},"excerpt":{"rendered":"

Class 11 Geography(Fundamentals of Physical Geography) NCERT book solutions for Chapter 4 – Distribution of Oceans and Continents Questions and Answers.<\/p>\n","protected":false},"author":21830,"featured_media":118724,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[],"class_list":{"0":"post-118739","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-education"},"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.mapsofindia.com\/my-india\/wp-json\/wp\/v2\/posts\/118739","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.mapsofindia.com\/my-india\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.mapsofindia.com\/my-india\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.mapsofindia.com\/my-india\/wp-json\/wp\/v2\/users\/21830"}],"replies":[{"embeddable":true,"href":"https:\/\/www.mapsofindia.com\/my-india\/wp-json\/wp\/v2\/comments?post=118739"}],"version-history":[{"count":1,"href":"https:\/\/www.mapsofindia.com\/my-india\/wp-json\/wp\/v2\/posts\/118739\/revisions"}],"predecessor-version":[{"id":118742,"href":"https:\/\/www.mapsofindia.com\/my-india\/wp-json\/wp\/v2\/posts\/118739\/revisions\/118742"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.mapsofindia.com\/my-india\/wp-json\/wp\/v2\/media\/118724"}],"wp:attachment":[{"href":"https:\/\/www.mapsofindia.com\/my-india\/wp-json\/wp\/v2\/media?parent=118739"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.mapsofindia.com\/my-india\/wp-json\/wp\/v2\/categories?post=118739"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.mapsofindia.com\/my-india\/wp-json\/wp\/v2\/tags?post=118739"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}