Igneous rock is formed by the cooling and solidification of molten Earth materials. Igneous rock forms when magma or lava cools. If igneous rock forms above ground after a volcanic eruption, it ________________ forming ____________ igneous rock, such as obsidian which is a naturally occurring volcanic glass.
A) cools quickly, extrusive
B) cools quickly, intrusive
C) cools slowly, extrusive
D) cools slowly, intrusive