EARTH SCIENCE
TECTONICS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Earth’s lithosphere is actually growing because much more crust is being created at subduction zones than destroyed.
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Earth’s lithosphere is not shrinking because new crust is being created at mid-ocean ridges.
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The student is correct; Earth’s lithosphere is shrinking.
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Earth’s lithosphere is not shrinking because crust is not actually destroyed at subduction zones; it simply sinks into the mantle before resurfacing elsewhere.
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Detailed explanation-1: -A student concludes that Earth’s lithosphere is gradually shrinking as crust is destroyed at subduction zones. What is wrong with this conclusion? Earth’s lithosphere is actually growing because much more crust is being created at subduction zones than destroyed.
Detailed explanation-2: -often, slices of the old ocean floor are caught in these collision zones (these are called ophiolites), and the process by which they are emplaced over the continents is called obduction (opposite of subduction).
Detailed explanation-3: -These plates collide, slide past, and move apart from each other. Where they collide and one plate is thrust beneath another (a subduction zone), the most powerful earthquakes, tsunamis, volcanic eruptions, and landslides occur.
Detailed explanation-4: -Earth’s lithosphere is not shrinking because crust is not actually destroyed at subduction zones; it simply sinks into the mantle before resurfacing elsewhere.
Detailed explanation-5: -A region where this process occurs is known as a subduction zone, and its surface expression is known as an arc-trench complex. The process of subduction has created most of the Earth’s continental crust.