How are igneous rocks primarily formed?

Igneous rocks are primarily formed from the cooling and solidification of magma, which is molten rock found beneath the Earth's surface. When magma rises to the surface, it can either erupt as lava or cool slowly underground. The rate at which it cools significantly affects the characteristics of the resulting igneous rock. For example, if the magma cools slowly beneath the surface, it has time to form large crystals, leading to coarse-grained textures, as seen in granite. If it cools quickly on the surface, such as after a volcanic eruption, it produces fine-grained textures with small crystals, like basalt.

Other processes described in the incorrect options do not relate to the formation of igneous rocks. Sedimentary rocks, for example, are formed from the compression of sediment, while organic materials lead to the formation of sedimentary rocks through processes involving compaction and cementation. Evaporation of water can lead to the formation of evaporite minerals, not igneous rock. Thus, the key process that characterizes igneous rock formation is the cooling of magma.