Science Olympiad Dynamic Planet Practice Test

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What is the main substance that forms the bedrock of the earth's crust?

Magma
Igneous rock
Metamorphic rock
Granite

The correct answer is: Igneous rock

The bedrock of the earth's crust is primarily composed of igneous rock. These rocks form from the cooling and solidification of magma or lava, which contributes significantly to the structure and composition of the earth's crust. Igneous rocks can be classified into two main types: intrusive (or plutonic) rocks, which crystallize below the earth's surface, and extrusive (or volcanic) rocks, which solidify on the surface. Granite, while a specific type of igneous rock, represents just one type of the broader category. The crust includes a variety of both igneous and other types of rocks, but igneous rock as a category more comprehensively encompasses the dominant materials that constitute the bedrock of the crust. Magma and metamorphic rocks, while they play important roles in geological processes, do not form the foundational layer of the crust in the same way that igneous rocks do.