Final answer:
Igneous rocks are formed by the cooling and solidification of molten material, either magma or lava. These rocks' varied textures, from fine to coarse-grained, depend on the cooling rate and where they solidify, either on Earth's surface or beneath it. The correct answer to how they form is from the cooling and solidification of magma or lava.
Step-by-step explanation:
The characteristics of igneous rocks and their formation are central to understanding Earth's geology. In contrast to sedimentary rocks, which form from particles cemented over time, and metamorphic rocks, which evolve under intense heat and pressure from other rock types, igneous rocks originate directly from molten materials. Specifically, these rocks are formed from the cooling and solidification of magma (if the process occurs beneath the surface of the Earth) or lava (if it occurs at the surface).
Igneous rocks are typically classified based on where they form and how quickly they cool. Extrusive, or volcanic, igneous rocks emerge onto the Earth's surface, cooling rapidly and typically resulting in fine-grained textures due to the short time available for crystal growth. Conversely, intrusive, or plutonic, igneous rocks form below the Earth's surface, where slow cooling allows the growth of larger mineral crystals, giving the rock a coarse-grained texture.
The correct answer to the question regarding how igneous rocks are formed is: Igneous rocks are formed from the cooling and solidification of molten material called magma or lava. This process can result in a wide range of rock types, distinguished by differences in mineral composition and the texture of the cooled rock, which are a reflection of the original molten material's composition and the specifics of the cooling process.