EARTH SCIENCE
TECTONICS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Erosion from continental crust continually forms new oceanic crust.
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The weight of the continents continually presses oceanic crust into the asthenosphere.
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Oceanic crust is continually recycled into the mantle and re-formed at mid-ocean ridges.
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The amount of oceanic crust in a tectonic plate does not change over time.
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Detailed explanation-1: -Oceanic crust is constantly formed at mid-ocean ridges, where tectonic plates are tearing apart from each other. As magma that wells up from these rifts in Earth’s surface cools, it becomes young oceanic crust. The age and density of oceanic crust increases with distance from mid-ocean ridges.
Detailed explanation-2: -Seafloor spreading occurs at divergent plate boundaries. As tectonic plates slowly move away from each other, heat from the mantle’s convection currents makes the crust more plastic and less dense. The less-dense material rises, often forming a mountain or elevated area of the seafloor. Eventually, the crust cracks.
Detailed explanation-3: -As old oceanic crust is subducted and melted into magma, new oceanic crust in the form of igneous rock is formed at mid-ocean ridges and volcanic hotspots.
Detailed explanation-4: -As old oceanic crust is consumed at the trenches, new magma rises and erupts along the spreading ridges to form new crust. In effect, ocean basins are perpetually being “recycled, ” with the creation of new crust and the destruction of old oceanic lithosphere occurring simultaneously.
Detailed explanation-5: -Oceanic crust may collide with a continent. The oceanic plate is denser, so it undergoes subduction. This means that the oceanic plate sinks beneath the continent.