You find a type of volcanic rock that is fairly smooth, and has only a few small holes made when gas and water vapor escaped as the rock cooled. you know that the rock can be classified as ...

This rock is a type of volcanic rock called Scoria. They are generally dark-colored and have bubble-like cavities that are known as vesicles. They can be black, dark gray or deep reddish brown in color that has similar characteristics to basalt rocks. They form when gases and water vapor escape from the rock as it cools from a volcanic eruption when exposed to the outer environment.