Students' Conceptions of Rocks and Rock Formation

Rocks and the rock cycle are among the fundamental ideas in geology because we need to understand them in order to understand Earth's history and processes. To evaluate students' conceptions of rocks and their formation, we disseminated nearly 200 questionnaires to introductory geology students of six different instructors at four different schools.

Most introductory geology students do not have a thorough understanding of rocks. When asked to “Tell me about the rock [granite, basalt, limestone, schist/gneiss],” most of what students describe are related to physical characteristics of the rocks (39% of comments) or labeling the rock type (29%). This makes sense, since this is mostly what students learn in rock labs, but it does not help students realize why rocks are important to the study of the Earth. Of the nearly 1000 statements students used to “Tell me about the rock,” only 75% of the statements were correct. When students chose to use geologic terms (such as sedimentary, mafic, or foliated), they applied the terms correctly 73% of the time.

Many students also have a poor understanding of the basic formation of rocks. In particular, they do not understand that rocks are the consequences of earth processes and not simply a matter of classification. Preliminary results indicate that one of the reasons is that students apply what they can see and observe in their every day lives to rock formation. Because of the immense time scales, depths, and temperatures involved, students cannot easily grasp how rocks form and, therefore, cannot fully understand what rocks tell us about the Earth.

A more holistic approach to teaching rocks, emphasizing why understanding rocks is useful and placing rock formation in a temporal and physical context, is needed to give students a more complete understanding of rocks.