Here's why:
* Intrusive means the magma (molten rock) cooled and solidified within the Earth's crust.
* Extrusive igneous rocks are formed when lava (magma that has erupted onto the surface) cools and solidifies above ground.
Think of it this way:
* Intrusive: Like a cake batter being baked in the oven. The batter (magma) cools and solidifies within the oven (Earth's crust).
* Extrusive: Like pouring batter onto a baking sheet and letting it cool. The batter (lava) cools and solidifies on the surface (Earth's surface).