Here's why:

* Vesicles: These are the air bubbles trapped within the rock as it cooled.

* Formation: Vesicles form when magma or lava contains dissolved gases. As the molten rock rises to the surface, the pressure decreases, causing the gases to expand and form bubbles. If the rock cools quickly enough, these bubbles get trapped, creating a vesicular texture.

Common examples of vesicular igneous rocks:

* Scoria: Dark-colored, very vesicular rock, often with large, irregular holes.

* Pumice: Light-colored, very vesicular rock, so light it can float on water.

Let me know if you have any other questions about igneous rocks!