Delicious Differential Weathering

Mary C. Gorte
Delta College (Modified from Mark Francek, Central Michigan University)
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In this activity students are exposed to the concept of both physical and chemical weathering while eating a Baby Ruth candy bar. This is compared to the weathering of a piece of granite. The strength of this activity is that students are engaged with food and is an excellent illustrator of how minerals are selectively weathered.

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Introduction to Geology at a community college.

Skills and concepts that students must have mastered

Students must understand what a mineral is and perhaps what minerals compose a granite.

How the activity is situated in the course

This exercise is situated after students have been exposed to minerals, rock types and their formation.


Content/concepts goals for this activity

The goal of this exercise is for students to
  1. understand the difference between chemical and physical weathering of rocks by comparing it to eating a Baby Ruth candy bar
  2. understand the difference between weathering and erosion
  3. understand the concept of Bowen's reaction series and how that plays a part in differential weathering
  4. understand the relationship between weathering and climate

Higher order thinking skills goals for this activity

Other skills goals for this activity

Description of the activity/assignment

Students are asked to place a Baby Ruth candy bar in their mouths but are asked not to bite it. Once they have sucked off all the chocolate and caramel the students are given permission to bite the peanuts. After lecturing on the differences between chemical and physical weathering students are asked to list the order of ingredients they tasted. Each group is given a sample of granite. Students are asked to list three visible minerals in the granite. Relate the minerals of the granite (hornblende, feldspar, and quartz) to the ingredients of the candy bar. Explain Bowen's reaction series and how different minerals will weather first and how climate will affect weathering rates.

Determining whether students have met the goals

Students take visual measurements of candy bars submerged in different temperature waters and see that weathering rates are accelerated in warmer waters.

More information about assessment tools and techniques.

Teaching materials and tips

Other Materials

Supporting references/URLs

This activity was originally designed by Mark Francek, Department of Geography and Earth Science, Central Michigan University