Given a scientific passage and an answer, generate a question for the given answer.
Q: Passage: Extrusive igneous rocks form above the surface. The lava cools quickly as it pours out onto the surface ( Figure below ). Extrusive igneous rocks cool much more rapidly than intrusive rocks. The rapid cooling time does not allow time for large crystals to form. So igneous extrusive rocks have smaller crystals than igneous intrusive rocks. Extrusive igneous rocks are also called volcanic rocks . Answer: volcanic rocks
A:
Extrusive igneous rocks are also called what?