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

Igneous rocks are most commonly associated with volcanic activity because they form from the solidification and cooling of molten rock, known as magma when it is beneath the earth's surface and lava when it erupts onto the surface. During a volcanic event, lava cools rapidly once it exits the volcano, resulting in the formation of various types of igneous rocks, such as basalt and pumice.

The presence of these rocks is a direct indicator of volcanic activity, as they are formed specifically from processes involving volcanic eruptions. The other types of rock—metamorphic and sedimentary—are formed through different processes unrelated to volcanic activity. Metamorphic rocks arise from the alteration of existing rocks under heat and pressure, while sedimentary rocks result from the accumulation and compaction of mineral and organic debris. Quartzite, specifically, is a type of metamorphic rock formed from the metamorphism of sandstone and is not directly linked to volcanic processes. Thus, igneous rocks are the most relevant choice when discussing rocks associated with volcanic activity.