By the end of this topic, students should be able to identify concentric zones of the earth, account for the variation in density and thickness of the concentric zones of the earth‘s crust, describe the characteristics of the earth‘s crust, the mantle and the core, identify types of rocks of the earth‘s crust, explain the mode of formation for each type of rocks and their economic importance, and describe the geological time scale and explain the mode of formation for each type of rocks and their economic importance.