What is a characteristic of igneous rock?

Igneous rock is characterized by its formation from the cooling and solidification of molten rock, either magma (below the Earth’s surface) or lava (above the Earth’s surface). When this molten material cools, it crystallizes to form solid rock. This process can occur either slowly beneath the ground, leading to coarse-grained textures, or more rapidly on the surface, resulting in fine-grained textures.

Understanding how igneous rocks originate is fundamental in geology because they play a key role in the rock cycle, which describes the transitions through geological time among the three main rock types: igneous, sedimentary, and metamorphic. Other options pertain to different rock formation processes; for example, the compaction of sediments relates to sedimentary rocks, while metamorphosis is linked to metamorphic rocks. Lastly, the presence of fossils is a characteristic of sedimentary rocks, not igneous. Thus, the unique formation process of igneous rock from cooling molten material is what distinguishes it in the rock classification system.