Earth & Space Systems - Pedagogical Connections: Constructing the Rock Cycle
In this activity, constructivist pedagogical principles are used to connect hands-on rock identification skills with an understanding of how different rock types are related through the rock cycle in accord with specific standards derived from the National Science Education Standards.
Developing a Rock Classification System
Large hand samples of the rocks used in standard class sample trays are placed in paper bags labeled with collection location, environment and an identifying code. Collectively the class must decide on criterion for how a novice to geology would classify the rock samples into 1 of 3 groups. While most will immediately try to use igneous, sedimentary and metamorphic designations, they are reminded to look at the problem as a novice would. A variety of possible rock classification categories (HTML File 17kB Jun6 05) results.
During discussion the students are forced to distinguish between secondary characteristics and truly unique identifiers in order for the classification system to create distinct meaningful classification of the rock samples. After a number of false starts the class will settle on method of formation as the best classification system resulting in the 3 traditional rock categories used by geologists. The students will then proceed to identify their own rock samples using dichotomous keys.
Linking Rock Types
With their samples classified and identified, the students are next asked to indicate how the rock types relate to each other. A containing all the rock samples is helpful in guiding this process. Each student is asked to locate their rock sample on the chart and proceed to expose their rock to various conditions from that point. By following through the processes that act at and below the earth's surface, the student can eventually trace their way through the entire rock sample collection, filling in each box with the appropriate rock type along the way.
In the process of going through this activity, the pre-service teachers are exposed to ways in which a task, ostensibly as tedious as rock identification, can be made interesting and meaningful to students while achieving larger content objectives of the instructor. Even the arrangement of the samples in the rock trays is coordinated to form linkages between the different rock types and the processes that connect them. The exercise also serves to reinforce the concepts scientists use to classify items, a skill needed in all science courses.