UNIVERSE
PLANETARY INTERIORS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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A convection cell can be hundreds of kilometers in diameter
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Convection currents flow at a rate of a few centimeters per year
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It takes approximately 450 million years to make a complete trip around a convection cell
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All of these are true.
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Detailed explanation-1: -The mantle is heated from below (the core), and in areas that are hotter it rises upwards (it is buoyant), whereas in areas that are cooler it sink down. This results in convection cells in the mantle, and produces horizontal motion of mantle material close to the Earth surface.
Detailed explanation-2: -Convection currents drive the movement of Earth’s rigid tectonic plates in the planet’s fluid molten mantle. In places where convection currents rise up towards the crust’s surface, tectonic plates move away from each other in a process known as seafloor spreading (Fig. 7.21).
Detailed explanation-3: -Convection occurs only in fluids. Convection occurs by the movement of particles from the hotter region to the cooler region. For example, boiling water, the heat transfer from the burner to the water occurs through convection.
Detailed explanation-4: -Mantle Convection and Plumes The primary sources of thermal energy for mantle convection are three: (1) internal heating due to the decay of the radioactive isotopes of uranium, thorium, and potassium; (2) the long-term secular cooling of the earth; and (3) heat from the core.
Detailed explanation-5: -Answer and Explanation: Yes. The mantle’s motion occurs through thermal convection, which involves hot rock rising from the mantle towards the top while gravitation pulls the denser rock towards the interior.