Cities create their own micro climates and produce large amounts of solid waste, photo chemical smog, and sewage
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Mountain effect refers to the windward side of the mountain receiving precipitation. It is also the effect of rough terrain on radio-wave propagation. Thus, it caused reflections that produce errors in radio direction-finder indications.
The main mechanism through which the layering happened is gravity: it pulled the heavier, denser material to the center, leaving the less dense material on the surface.
The material that was on the outside cooled quicker, but this was the result, not the cause.
The answer is
<span>2) Gravity caused more-dense material to move toward the center of each planet.</span>
