Which type of rocks are formed from volcanic activity?

Igneous rocks are formed through the cooling and solidification of magma or lava. When a volcano erupts, the molten rock from beneath the Earth's crust is expelled to the surface, where it cools and crystallizes. This process can occur either underground, producing intrusive igneous rocks, or on the surface, leading to the formation of extrusive igneous rocks.

The key characteristic that distinguishes igneous rocks is their origin from volcanic activity, which can be traced back to a significant geological process where heat and pressure lead to the formation of magma. Once this magma cools down, it results in rocks such as granite (intrusive) and basalt (extrusive).

In comparison, sedimentary rocks are formed from the accumulation and compaction of mineral and organic particles, while metamorphic rocks result from the alteration of existing rocks under heat and pressure without melting. The term "pressure rocks" does not accurately describe a specific type of rock but rather relates to the process of metamorphism without direct volcanic activity. This understanding emphasizes the unique geological processes that lead to the formation of igneous rocks.