Which type of rock is most commonly associated with volcanic activity?

Igneous rocks are formed from the solidification of molten magma or lava, which is a direct result of volcanic activity. When a volcano erupts, lava that flows onto the surface cools and crystallizes to form extrusive igneous rocks, such as basalt. When magma cools beneath the surface of the Earth, it forms intrusive igneous rocks, such as granite. The classification of igneous rocks is fundamentally linked to their origin from volcanic processes, making them the rock type most commonly associated with such activity.

In contrast, metamorphic rocks form from the alteration of existing rocks due to heat, pressure, and chemically active fluids, which can occur in tectonic settings but not specifically from volcanic activity. Sedimentary rocks originate from the accumulation of sediments, which can be derived from the weathering of rocks, including igneous types, but they are not directly formed from volcanic processes. Quartzite is a specific type of metamorphic rock that forms from the metamorphism of quartz-rich sandstone and has no direct link to volcanic activity. Thus, igneous rocks are clearly the most relevant type associated with volcanic eruptions.