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Rock Description

This material was originally created for On the Cutting Edge: Professional Development for Geoscience Faculty
and is replicated here as part of the SERC Pedagogic Service.

Initial Publication Date: July 22, 2013

Michael Phillips, Illinois Valley Community College
Course: Historical Geology
15-30 students
My historical geology course is focused on how geologists are able to "read the rocks" and thereby interpret the Earth's history. This activity introduces the students to the importance and difficulties of describing and communicating observations.

As the course progresses, students refine their descriptions and develop a history of their rock's formation. They will the describe and develop a history for two additional rocks. (Ultimately, one of each type.) We then work on correlation and developing histories based on the rocks present in an area.

The first day exercise provides the foundation for the entire course.

The Activity

At the start of class each student is given a rock and asked to describe it in writing on an index card. They are told that the description has to be good enough that another student can select it from a pile of rocks based on the description.

After all of the descriptions are completed, students place their rocks on a table at the front of the room and turn in their cards. The cards are shuffled and handed out to the students who must select a rock from the table based on the description. After everyone has a rock, the instructor goes around the room, holds up each rock, reads the description and asks if the appropriate rock was selected until all rocks are with the correct card.

The class then develops a list of important components of a good description and discusses the importance of those components.