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 sinking down of Earth crust inside the crust is called as _______________ . | |||
| Right Option : B | |||
| View Explanation | |||
Oceanic trenches are ______________ . | |||
| Right Option : A | |||
| 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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