Seafloor Spreading
Seafloor Spreading
Sea Floor Spreading: In 1872, scientists were surveying the ocean floor for an undersea telegraph cable to be laid between North America and Europe. They measured ocean depth by dropping down very long cables and measuring their length. In the middle of the Atlantic Ocean, they discovered a large mountain ridge that extended a long way south. The extent of the ridge was not investigated then. However, in 1925, German scientists used sonar (echo sounding) to confirm that this ridge ran tine entire length of the Atlantic Ocean.
After 1945, further studies using sonar showed that the underwater ridge continued into other oceans and around Earth. In 1953, the ridges were found to have a series of huge cracks along them. The cracks are called rifts and so the system was named the Great Global Rift system.
In 1962, an American geologist Harry Hess (1906-69), tried to explain what was happening at the ocean ridges. While serving the US Navy during World War II (1939-45). Hess had used sonar to map the floor of the Pacific Ocean. There he had discovered many underwater, flat-topped mountains. When the Great Global Rift found, he thought back to his discoveries of mountains under the sea.
Hess proposed that new rocky crust was being formed at the ocean ridges and spreading outwards. This process was later called seafloor spreading. Hess proposed that the the crust was sinking down into Earth, forming ocean trenches. As the crust sinks, it melts and is destroyed. The process of the crust sinking down like this is called subduction.
The method used by the German scientists to measure the depth of sea was ___________ . | |||
| Right Option : B | |||
| View Explanation | |||
The sinking down of Earth crust inside the crust is called as _______________ . | |||
| Right Option : B | |||
| View Explanation | |||
The rift system present under the sea and spreads around the Earth is called as ______________ . | |||
| Right Option : A | |||
| View Explanation | |||
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Abhyas institute is one of the best coaching institute in the vicinity of Ambala cantt.The institute provides good and quality education to the students.The teachers are well experienced and are very helpful in solving the problems. The major advantages of the institute is extra classes for weak...
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Yogansh Nyasi
7thAbhyas institute is one of the best coaching institute in the vicinity of Ambala Cantt area. The teachers of the institute are well experienced and very helpful in solving the problems of the students.The good thing of the institute is that it is providing extra classes for the students who are w...
Aman Kumar Shrivastava
10thThird consective year,my ward is in Abhyas with nice experience of admin and transport support.Educational standard of the institute recumbent at satisfactory level. One thing would live to bring in notice that last year study books was distributed after half of the session was over,though study ...
Ayan Ghosh
8thMy experience with Abhyas is very good. I have learnt many things here like vedic maths and reasoning also. Teachers here first take our doubts and then there are assignments to verify our weak points.
Shivam Rana
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Aman Kumar Shrivastava
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Shreya Shrivastava
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Ayan Ghosh
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Manish Kumar
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10thMy experience with Abhyas Academy has been very good. When I was not in Abhyas whenever teacher ask questions I could not speak it confidently but when I came in Abhyas, my speaking skills developed and now I am the first one to give the answer of teachers question.
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7thUsually we see institutes offering objective based learning which usually causes a lag behind in subjective examinations which is the pattern followed by schools. I think it is really a work of planning to make us students grab the advantages of modes of examination, Objective Subjective and Onli...
Anika Saxena
8thIn terms of methodology I want to say that institute provides expert guidence and results oriented monitering supplements by requsite study material along with regular tests which help the students to improve their education skills.The techniques of providing education helps the students to asses...
Aman Kumar Shrivastava
10thWe started with lot of hope that Abhyas will help in better understnding of complex topics of highers classes. we are not disappointed with the progress our child has made after attending Abhyas. Though need to mention that we expected a lot more. On a scale of 1-10, we would give may be 7.
