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UPSC GS notes Distribution of oceans and continents A lfred Wegener, A German Metro largest who put forth the comprehensive ornament in the form of the continental drift theory in 1912. This was the first query regarding distribution of the oceans and continents. According to Wegener, all continents formed a single continental mass and mega ocean surrounded the same. The supercontinent was named PANGAEA, which meant all earth. The mega ocean was called PANTHALASSA, meaning or water. He argued that around 200 million year ago, the supercontinent, Pangaea, begin to split. Pangaea first broke into two large Continental masses as Laurasia and Gondwanaland forming the northern and south and components respectively. Subsequently. Laurasia and Gondwanaland continued to break into various smaller continents that exist today. Evidence in support of continental driftThe matching of continent ( Jig-Saw-Fit)The shorelines lines of Africa and South America said to have unmistakable match according to the map presented through computer program by Bullard in 1964.Rocks of same age across the oceansThe radiometric dating methods developed in the recent years have facilitated correcting the rock formation from different continents across the vast ocean. The belt of ancient rocks of 2000 million years from Brazil coast matches with those of western Africa. Tillite It is the sedimentary rock formed out of deposit of glaciers. The Gondwana system of sentiment from India is known to have its counterparts in six different land masses of the Southern Hemispheres. Placer depositsThe occurrence of rich placer deposits of gold in Ghana cost and the absolute absence of source rock in the region is an amazing fact. The gold wearing veins are in Brazil and it’s obvious that the gold deposit of Ghana are derived from Brazil Plateau when the two continents lay side-by-side.Distribution of fossilsWith identical species of plants and animals adapted to living on land or in freshwater or found on either side of the Marine barrier, a problem arises regarding accounting for such distribution. The observation that Lemurs occurs in India, Madagascar and Africa led some to consider a contiguous landmass “Lemuria” linking these three land masses.Concept of sea floor spreadingThe mapping of ocean floor and paleomagnetic studies of rock from organic regions revealed the following facts:i. It was realised that all along the mid oceanic ridges, volcanic eruption are common and they bring huge amounts of lava to the surface in this area.ii. The rock equidistance on either side of the crest of the meat oceanic ridges so remarkable similarities in the term of freedom of formation, chemical compositions and magnetic properties. Draw 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.iii. The 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 rocks formation are as old as 3200 million years.iv. The sediments on the ocean floor are unexpectedly very thin. Scientists expecting, 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.v. The deep trenches have deep-seated earthquake occurrence while in the mid-oceanic ridge areas, the quack foci have shallow depth.Hess, based on the above facts, propounded his hypothesis of “sea floor spreading”. Hess argue that constant eruptions at the crest of oceanic ridges cause the rapture of oceanic crust and the new lava wedges into it, pushing the oceanic crust on either side. The ocean floor, that is traits. The younger age of the oceanic crust as well as the fact that the spreading of One ocean does not cause the sinking of other, made him think about the consumption of oceanic crust. He further mentioned that the ocean floor that gets washed due to volcanic eruption at the crest, since down at the trenches and get consumed. Major players that led to the foundation of the world we see today are:1. Antarctica and the surrounding oceanic plate2. North American3. South American4. Pacific plate5. India Australia New Zealand plate6. Africa with eastern Atlantic floor plate7. Eurasia and the adjacent oceanic plateThis place has been constantly moving over the globe throughout the history of the earth. It is not the continent that moves as believed by Wagner. Continents are part of a plate and what is the plate. Divergent boundariesWe are crust is generated as the plates pull away from each other. The sites where the plates move away from each other or called spreading sites. The best known example of diverging boundaries is the mid-Atlantic Ridge. At this, the American players are separated from her Asian and African leaders.Convergent boundariesWhere the crust is destroyed as one plate dived under another. The location where sinking of the plate occurs is called subduction zone. There are three ways in which convergence can occur. This car, first, between and Oceanic and continental plates, second, between two oceanic plates, and third, between two continental plates.Transform boundariesWhere the trust is neither produced nor destroyed as the plates slide horizontally past each other. Transform faults are the planes of separation generally perpendicular to the oceanic ridges. As the election do not take all along the entire press at the same time, there is differential moment of a portion of the plate away from the axis of the earth. Also, the rotation of the earth has its effect on separated blocks of the plate portions.The movement of Indian platesThe Indian states include Penninsular India and the Australian continental oceans. The subjects in June along the himalayan forms the northern play pondering in the form of continent- continental convergence. In the east, it extends through Rakinyoma Mountains of the Myanmar towards the island or a long jumper trench. The eastern margin is spreading site link to the east of Australia in the form of oceanic ridge in the SW Pacific. The western margins follows Kirthar mountain of Pakistan. It further extends along the Makrana coast and joins the speeding side from Red Sea rift southeastward along the Chagla Archipelago. The boundary between India and the Antarctic plate is marked by oceanic ridge (divergent boundary) running in roughly West East direction and merging into spreading site, a little south of New Zealand. India was a large Island situated of the Australian coast, in a vast ocean. The Tethys Sea separated 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 year ago causing rapid uplift of the Himalaya. The position of India since about 71 million years till project is what we see today in the map.
UPSC GS notes
Distribution of oceans and continents
A
lfred Wegener, A German Metro largest who put forth the comprehensive ornament in the form of the continental drift theory in 1912. This was the first query regarding distribution of the oceans and continents.
According to Wegener, all continents formed a single continental mass and mega ocean surrounded the same. The supercontinent was named PANGAEA, which meant all earth. The mega ocean was called PANTHALASSA, meaning or water. He argued that around 200 million year ago, the supercontinent, Pangaea, begin to split. Pangaea first broke into two large Continental masses as Laurasia and Gondwanaland forming the northern and south and components respectively. Subsequently. Laurasia and Gondwanaland continued to break into various smaller continents that exist today.
Evidence in support of continental drift
The matching of continent ( Jig-Saw-Fit)
The shorelines lines of Africa and South America said to have unmistakable match according to the map presented through computer program by Bullard in 1964.
Rocks of same age across the oceans
The radiometric dating methods developed in the recent years have facilitated correcting the rock formation from different continents across the vast ocean. The belt of ancient rocks of 2000 million years from Brazil coast matches with those of western Africa.
Tillite
It is the sedimentary rock formed out of deposit of glaciers. The Gondwana system of sentiment from India is known to have its counterparts in six different land masses of the Southern Hemispheres.
Placer deposits
The occurrence of rich placer deposits of gold in Ghana cost and the absolute absence of source rock in the region is an amazing fact. The gold wearing veins are in Brazil and it’s obvious that the gold deposit of Ghana are derived from Brazil Plateau when the two continents lay side-by-side.
Distribution of fossils
With identical species of plants and animals adapted to living on land or in freshwater or found on either side of the Marine barrier, a problem arises regarding accounting for such distribution. The observation that Lemurs occurs in India, Madagascar and Africa led some to consider a contiguous landmass “Lemuria” linking these three land masses.
Concept of sea floor spreading
The mapping of ocean floor and paleomagnetic studies of rock from organic regions revealed the following facts:
i. It was realised that all along the mid oceanic ridges, volcanic eruption are common and they bring huge amounts of lava to the surface in this area.
ii. The rock equidistance on either side of the crest of the meat oceanic ridges so remarkable similarities in the term of freedom of formation, chemical compositions and magnetic properties. Draw 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.
iii. The 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 rocks formation are as old as 3200 million years.
iv. The sediments on the ocean floor are unexpectedly very thin. Scientists expecting, 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.
v. The deep trenches have deep-seated earthquake occurrence while in the mid-oceanic ridge areas, the quack foci have shallow depth.
Hess, based on the above facts, propounded his hypothesis of “sea floor spreading”. Hess argue that constant eruptions at the crest of oceanic ridges cause the rapture of oceanic crust and the new lava wedges into it, pushing the oceanic crust on either side. The ocean floor, that is traits. The younger age of the oceanic crust as well as the fact that the spreading of One ocean does not cause the sinking of other, made him think about the consumption of oceanic crust. He further mentioned that the ocean floor that gets washed due to volcanic eruption at the crest, since down at the trenches and get consumed.
Major players that led to the foundation of the world we see today are:
1. Antarctica and the surrounding oceanic plate
2. North American
3. South American
4. Pacific plate
5. India Australia New Zealand plate
6. Africa with eastern Atlantic floor plate
7. Eurasia and the adjacent oceanic plate
This place has been constantly moving over the globe throughout the history of the earth. It is not the continent that moves as believed by Wagner. Continents are part of a plate and what is the plate.
Divergent boundaries
We are crust is generated as the plates pull away from each other. The sites where the plates move away from each other or called spreading sites. The best known example of diverging boundaries is the mid-Atlantic Ridge. At this, the American players are separated from her Asian and African leaders.
Convergent boundaries
Where the crust is destroyed as one plate dived under another. The location where sinking of the plate occurs is called subduction zone. There are three ways in which convergence can occur. This car, first, between and Oceanic and continental plates, second, between two oceanic plates, and third, between two continental plates.
Transform boundaries
Where the trust is neither produced nor destroyed as the plates slide horizontally past each other. Transform faults are the planes of separation generally perpendicular to the oceanic ridges. As the election do not take all along the entire press at the same time, there is differential moment of a portion of the plate away from the axis of the earth. Also, the rotation of the earth has its effect on separated blocks of the plate portions.
The movement of Indian plates
The Indian states include Penninsular India and the Australian continental oceans. The subjects in June along the himalayan forms the northern play pondering in the form of continent- continental convergence. In the east, it extends through Rakinyoma Mountains of the Myanmar towards the island or a long jumper trench. The eastern margin is spreading site link to the east of Australia in the form of oceanic ridge in the SW Pacific. The western margins follows Kirthar mountain of Pakistan. It further extends along the Makrana coast and joins the speeding side from Red Sea rift southeastward along the Chagla Archipelago. The boundary between India and the Antarctic plate is marked by oceanic ridge (divergent boundary) running in roughly West East direction and merging into spreading site, a little south of New Zealand.
India was a large Island situated of the Australian coast, in a vast ocean. The Tethys Sea separated 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 year ago causing rapid uplift of the Himalaya. The position of India since about 71 million years till project is what we see today in the map.