English: Igneous rocks form by the cooling & crystallization of hot, molten rock (magma & lava). If this happens at or near the land surface, or on the seafloor, they are extrusive igneous rocks. If this happens deep underground, they are intrusive igneous rocks. Most igneous rocks have a crystalline texture, but some are clastic, vesicular, frothy, or glassy.

Volcanic breccias are clastic-textured, extrusive igneous rocks. They generally appear as multicolored, jumbled masses of angular grains. Volcanic breccias have violent origins. They form from explosive volcanic eruptions (cf. effusive eruptions/lava flows). Volcanoes having felsic or intermediate chemistries typically erupt violently. Powerful volcanic ash eruptions result in deposits with mixes of large & small grains. Upon burial & lithification, these deposits become volcanic breccias.

The clastic texture of volcanic breccia is often termed pyroclastic or volcaniclastic.