Igneous rocks that cool quickly on the surface are called extrusive igneous rocks.

Here's why:

* Extrusive means the rock formed from lava that erupted onto the Earth's surface.

* Intrusive rocks, on the other hand, cool slowly underground.

Here are some characteristics of extrusive igneous rocks:

* Fine-grained texture: The rapid cooling doesn't allow for large crystals to form, resulting in a fine-grained texture, often appearing smooth or glassy.

* Examples: Basalt, rhyolite, andesite, obsidian, pumice, scoria.

Let me know if you'd like to know more about specific types of extrusive igneous rocks!