Geologic Time

Question 6 • Biology A (The Living Earth A)

Which best explains how gravity contributes to the formation of layers in protoplanets?

Answer

Gravity attracts materials and causes compaction, which produces heat and leads to the melting, sinking, and rising of materials.

Gravity causes materials to undergo radioactive decay, which produces heat and leads to the melting, sinking, and rising of materials.

Gravity absorbs heat, which cools materials and causes them to sink and rise.

Gravity releases heat into space, which cools materials and causes them to sink and rise.

Explanation

Gravity pulls material in a protoplanet together, compacting it and generating heat. As the interior heats enough to melt, denser materials sink while less-dense materials rise, separating the protoplanet into layers. Radioactive decay can also produce heat, but gravity does not cause radioactive decay.

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