What are igneous rocks?

• A. Rocks formed by deposition of sediments.
• B. Rocks formed from the solidification of molten magma or lava.
• C. Rocks formed by alteration due to heat and pressure.
• D. Rocks formed by precipitation from solution.

Answer: (B)

Igneous rocks form when molten rock material cools and crystallizes, either below the surface as magma (intrusive) or after erupting onto the surface as lava (extrusive). This cooling solidifies the molten material into minerals, creating characteristic textures from coarse-grained in intrusive rocks like granite to fine-grained or glassy in extrusive rocks like basalt or obsidian. This is what sets igneous rocks apart from other rock types.

The option describing rocks formed by deposition of sediments refers to sedimentary rocks. The idea of alteration by heat and pressure points to metamorphic rocks. Rocks formed by precipitation from solution describe chemical sedimentary rocks.