Which statement correctly identifies igneous rocks that form at or below the Earth's surface?

• A. Sedimentary rock from compressed sediments
• B. Metamorphic rock formed under high pressure
• C. Igneous rock that forms on the Earth's surface
• D. Igneous rock (intrusive igneous rock when cooling occurs below the surface)

Answer: (D)

Rocks that are igneous form from melted rock that cools and solidifies. When cooling happens beneath the surface, it occurs slowly, so crystals have time to grow larger, creating intrusive (plutonic) igneous rocks. The statement that correctly identifies igneous rocks forming at or below the Earth’s surface describes this intrusive type. If cooling occurred on the surface, the rock would be extrusive igneous, with rapid cooling and very small crystals or glass. Sedimentary rocks come from compressed sediments, and metamorphic rocks form from existing rocks altered by heat and pressure, not from molten rock cooling.