EARTH SCIENCE
TECTONICS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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The ocean floor is flat.
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The age of the seafloor gets younger as you move further away from the mid-ocean ridge.
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Newest seafloor is found at the mid-ocean ridge and it gets older as your move away from the ridge.
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The age of the seafloor decreases as you get closer to a continent.
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Detailed explanation-1: -Seafloor spreading was proposed by an American geophysicist, Harry H. Hess in 1960. By the use of the sonar, Hess was able to map the ocean floor and discovered the mid-Atlantic ridge (mid-ocean ridge). He also found out that the temperature near to the mid-Atlantic ridge was warmer than the surface away from it.
Detailed explanation-2: -Hess envisaged that oceans grew from their centres, with molten material (basalt) oozing up from the Earth’s mantle along the mid ocean ridges. This created new seafloor which then spread away from the ridge in both directions.
Detailed explanation-3: -Hess’s bold intuition was subsequently corroborated. Later studies showed that the age of the ocean floor increases with distance from the ridge crests, and seismic studies confirmed that the oceanic crust was indeed sinking into the trenches.
Detailed explanation-4: -Harry Hess was a geologist and Navy submarine commander during World War II. Part of his mission had been to study the deepest parts of the ocean floor. In 1946 he had discovered that hundreds of flat-topped mountains, perhaps sunken islands, shape the Pacific floor.
Detailed explanation-5: -What they discovered was that the magnetism of the ocean floor around mid-ocean ridges was divided into matching “stripes” on either side of the ridge. The specific magnetism of basalt rock is determined by the Earth’s magnetic field when the magma is cooling.