Obsidian is a type of igneous rock that is very smooth, glassy, and it contains small crystals. What does this tell you about this type of rock?
It is an extrusive igneous rock, formed beneath the surface of the earth.
It is an intrusive igneous rock, formed outside the surface of the earth.
It is an extrusive igneous rock, formed outside the surface of the earth.
It is an intrusive igneous rock, formed inside the surface of the earth.