Which rock type forms primarily from the cooling and solidification of molten rock?

• A. Sedimentary
• B. Metamorphic
• C. Weathered
• D. Igneous

Answer: (D)

When molten rock cools and solidifies, it becomes igneous rock. This happens whether the molten material is magma cooling underground or lava erupting at the surface. Crystals form as atoms arrange themselves as the melt loses heat, and the speed of cooling influences crystal size: slow cooling inside the crust creates coarse-grained rocks like granite, while rapid cooling at the surface produces fine-grained rocks like basalt, or even volcanic glass if cooling is extremely fast.

The other options describe different pathways: sedimentary rocks come from particles deposited and compacted or from precipitation, metamorphic rocks arise from existing rocks altered by heat and pressure without melting, and weathered isn’t a rock type at all but a process of breaking down rocks.