Sedimentary Rock Descriptions and Scientific Communication

Thomas Evans, Western Washington University
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This activity challenges students to write three rock descriptions and edit the work of their peers. The goal is for students to realize the importance of rock descriptions, learn how to write them, and gain practice.

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This activity was designed for a 300 (junior) or 400 (senior) level sedimentology and stratigraphy class as one of the first labs during the term (to prepare them for later labs and class exercises). The assumption is that the students have been taught how to write sediment and rock descriptions at some point in previous classes. It is not necessary that this training have happened in the recent past. In addition, this will work better in a smaller class (~20 people or smaller), however, it can be adapted to a larger class if necessary, though you will probably need a few TA's present to make the exercise more effective. The exercise was written for a two hour lab, so will likely take between 1.5 and 2 hours.

This activity also requires an extensive collection of sedimentary rocks. For small schools that do not have an extensive collection, this may not be possible. However, if a small collection is a reality this can be performed with a small class, or by altering the number of specimens to two for each student.

If desired this activity could be modified for an introductory (100 or 200 level) physical geology course and used as a study session exercise before an exam. This would require TA support for large classes to assemble the number of rocks required.

Skills and concepts that students must have mastered

This activity was written assuming students have received training in writing rock descriptions some time in their past. However, it is also assumed that the students have forgotten how to perform this skill. So no prior skill is required to perform this activity.

How the activity is situated in the course

This activity is performed early in the term as part of a lab. It used to teach a skill that is then expected and required of them in future labs, class assignments, and a class project. So this is a foundation laying lesson for the rest of the term.


Content/concepts goals for this activity

  1. Students self identify the importance and reason for learning rock descriptions.
  2. Students learn the parts of a rock description, and how to compose a succinct but thorough description.
  3. Students gain practice in writing and editing rock descriptions.

Higher order thinking skills goals for this activity

This activity helps students understand the importance of quality rock descriptions, and encourages them to reflect on their development throughout the lesson. As such, this lesson helps them develop metacognitive skills they can use in other aspects of their education.

Other skills goals for this activity

  1. Students should understand how to write using normal spelling and grammar.
  2. Students should know how to provide constructive feedback to their peers (in other words, how to play well with others in a professional context).

Description and Teaching Materials

Advance Preparation: (should take about half an hour)

  1. Photocopy a handout for each student (the form is provided on this site)
  2. Collect rock samples for each student. Each student will need three rocks of the same basic rock type (i.e. three different sandstones, or three different fossiliferous limestones, etc.). Having them in trays may facilitate handing them out. What is important is that the rocks be similar but not identical. Because the students tend to rely on color, shape, and size to identify rocks, having three rocks of similar color, shape, and size will be helpful in facilitating this activity.
  3. Pick an unknown rock students will describe as a summative assessment. This will work better if you have many samples of the same rock so multiple students can work on this simultaneously.

Lesson Plan:

  1. Welcome to the class and introduction to the activity. This will vary depending on the individual, so please customize this for your individual class!
  2. Hand out the student worksheet to everyone.
  3. Have the students perform a self-assessment of their own ability to describe rocks and explain the importance of describing sedimentary rocks effectively for others. (This is filling out the first two questions on the student handout.) Intentionally there is no introductory text to explain the importance of the classroom exercise because the students self-identify the importance during the exercise.
  4. Divide the class into groups of 2 students. This works best if the students sit directly across a table from each other. This can also serve as an effective ice breaker if you randomize the class seating before this exercise.
  5. Hand out three rocks to each student. Tell students to hide the rocks from the person sitting across from them. This can be done easily with a three ring binder opened and stood on its end in front of the rocks. Remember that each of the rocks should be similar (all lithic arenites, or all oolitic limestones, etc.), but each different in some way.
  6. 6. Have each student pick one of their three rocks, and ask them to describe it (question 3 on the student handout). Give them no more than 5 minutes, and make sure they write legibly! Watch the class and cut the activity short when student attention drifts. Tell students that the size and shape of the rock sample should not be part of the description (This is really important!!!).
  7. When students are done, have them trade sheets of paper.
  8. Have each student remove the barrier and show each other their set of rocks. The partner must read the rock description and pick which rock their peer described. Emphasize that they should not help each other! This works well if you do not tell them that their partners will be reading their work since it gives them a realistic sense of what it is like when their work is read by other people who they may not know (like in professional geoscience).
  9. Have students return the papers to their respective owners
  10. Have students reflect on the identification they performed by thinking about what they needed to know to identify the rock and what information was missing from the rock description (questions 4 and 5 on the student handout).
  11. Have students reflect on the rock description they wrote. What should they have added and why (questions 6 and 7 on the student handout)?
  12. Transition from a student activity to a lecture or class discussion. Here is my lesson plan for this short lecture (I have also posted the powerpoint I use when I introduce the concept):
    • Explain the context of the lesson (the big picture slide) to give the students a framework in which to assimilate the information.
    • Discuss why we should personally care about rock descriptions (future applicability, communication between peers, etc.).
    • Discuss the learning goals briefly.
    • Introduce the concept of rock descriptions; what they are, why they are needed, etc.
    • Teach description mechanics: Start with a rock name, and work from specific observations to more general observations.
    • Point out the second page of the handout lists all the possible things that could be in a sedimentary rock description, and has the content of this lecture in it. (It is also a cheat sheet for field camp rock descriptions!)
    • Provide advice on common mistakes and generally how to write descriptions.
  13. Transition from lecture/discussion to student work by telling students to pick another one of their three rocks and describing it with the new information (5 minutes). Make sure they write legibly!
  14. Have students trade their rock descriptions with their partner and edit them for 5 minutes.
  15. Have students return the edited rock descriptions.
  16. Have students read the edits, then describe the last of their three rocks, again 5 minutes and written legibly.
  17. Students trade rock descriptions and edit them, again for 5 minutes.
  18. Have students return their edits, read over them, and reflect on how they have improved in writing rock descriptions (question #8 on the handout).
  19. Have students turn in two typed and edited professional quality rock descriptions of two of their three rock samples, and a third rock description of an unknown rock (they observe and write the description of the unknown rock without any help).

Note: If you have enough time you can extend this in to teaching how to write rock interpretations.

Lesson Plan in a Word Document (Microsoft Word 2007 (.docx) 16kB Jun30 14)
Student Handout for the Rock Description Lab (Microsoft Word 2007 (.docx) 524kB Jun30 14)
Powerpoint Lesson for Rock Description Lab (PowerPoint 2007 (.pptx) 5.6MB Jun30 14)

Teaching Notes and Tips

I have written teaching notes direction in to the lesson plan for each section of the lesson. That way you can see the advice for each part of the lesson, rather than general advice on the lab as a whole.


Students turn in the following:
  1. 2 typed and edited rock descriptions that they worked on in class with their peers.
  2. 1 rock description of a rock they describe without a peer's help.
  3. The filled out first two pages of the lab.

These items demonstrate students have reached the desired proficiency with rock descriptions, and are an opportunity to show the instructor how they are thinking about their learning.

References and Resources