EARTH SCIENCE
TECTONICS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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That the crust was made of a plastic-like substance.
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That the crust was thicker in some places than in others.
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That the crust was made of 9 tectonic plates.
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That the crust could be created and destroyed.
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Detailed explanation-1: -Scientists knew that Earth was not getting bigger as new crust was formed at the ridges. What did the discovery of oceanic trenches help scientists understand? That the crust was made of a plastic-like substance.
Detailed explanation-2: -Seafloor spreading creates new crust. Subduction destroys old crust. The two forces roughly balance each other, so the shape and diameter of the Earth remain constant.
Detailed explanation-3: -Maps and other data gathered during the war allowed scientists to develop the seafloor spreading hypothesis. This hypothesis traces oceanic crust from its origin at a mid-ocean ridge to its destruction at a deep sea trench and is the mechanism for continental drift.
Detailed explanation-4: -Hess discovered that the oceans were shallower in the middle and identified the presence of Mid Ocean Ridges, raised above the surrounding generally flat sea floor (abyssal plain) by as much as 1.5 km.
Detailed explanation-5: -By studying ocean trenches, scientists can better understand the physical process of subduction and the causes of these devastating natural disasters.