Write the answers to the following questions in your own words.

1.    What is the difference between intrusive and extrusive rocks regarding the cooling process and the size of the crystals?

2.    Describe the three main classes of rocks.

3.    What criteria are used to categorize rocks into the three classes that you described in question 2?

4.    List two common rock types in each of the three main classes of rocks. Were these rock names familiar to you before you read this unit?