Fractional Crystallization of an M&M Magma Chamber Modified for Large Courses

Tuesday 1:30pm-1:50pm Northrop Hall: 340
Teaching Demonstration Part of Tuesday B


Euan Mitchell, Miami University-Oxford


This demo will feature modifications for using the 'M&M® Magma Chamber to Illustrate Magmatic Differentiation' in large classes. All of the files (Word document instructions, PowerPoint magma chamber, Excel file for calculations) associated with this activity, including a completed 'answer key' will be available for participants to work through any or all of the activity for themselves.

Student Handout (Microsoft Word 2007 (.docx) 22kB Jun22 17)

Data Sheet (Excel 2007 (.xlsx) 31kB Jun22 17)

Starting Magma Chamber (PowerPoint 2007 (.pptx) 44kB Jun22 17)


This activity is a modification of the existing SERC activity "Using an M&M® Magma Chamber to Illustrate Magmatic Differentiation." The modification makes the activity more suitable for use in large enrollment courses without unreasonable numbers of M&Ms. The 'magma chamber' is contained within a PowerPoint slide, and M&Ms are replaced with colored circles. After identifying the chemistry of each mineral and the appropriate elements needed to form it, the magma chamber is crystallized in 10 steps, with circles representing the appropriate number and composition of minerals being removed to the bottom of the PowerPoint slide. After each step the slide is copied and pasted to provide the starting point for the next step. In this way students have a permanent record of both liquid and cumulate mineral compositions at each stage of the activity. After completing all 10 steps students perform some calculations of liquid composition and make plots of trends of each of the six elements involved. Reflection questions guide students to think about the process they have just represented, as well as prompting them to consider the level of realism of the model and potential improvements.


I have used this activity as an in-class exercise, with a homework follow-up, in an introductory Geology of U.S. National Parks class, and plan on using it again in a traditional physical geology class in the future. Both are large (~90-200 student) enrollment courses targeted at non-science majors fulfilling a degree requirement.

The original activity was developed for a petrology course and this modification could be similarly edited to make the activity more or less demanding as individual instructors see fit.

Why It Works

The process of fractional crystallization is one that students routinely struggle to understand in introductory geology courses. The original hands-on activity made the process much more tangible. This modification allows even students in very large enrollment courses a similar tangible experience, without the need for huge numbers of M&Ms or unreasonably large groups.