Initial Publication Date: May 1, 2006

Analog Materials

Fun with foam, demonstrating strike and dip in class

Colorful foam sheets are used in a classroom or lab setting to introduce students to the concept of strike and dip. It is interactive, and the instructor or TA's can quickly see which students are 'getting' it and which might need a little more individual assistance.

submitted by Angela Moore, Guilford College

Cake and Pudding Lithosphere and Asthenosphere

As a review of the earth's upper layers, I make a special cake for the students.
Place the following layers in a glass 9 x 13 inch cake pan:
top - vanilla cake
middle - chocolate cake
bottom - chocolate pudding

In this model:

  • The crust is represented by the vanilla "composition".
  • The mantle is represented by the chocolate "composition".
  • The lithosphere is represented by the cake layers, and
  • The asthenosphere is represented by the pudding.
I try to emphasize the difference between rheological layers (cake vs. pudding) and compositional layers (vanilla vs. chocolate) represented by the cake.
submitted by Gayle Gleason

Diggies and Cheese Boudins

These two ingredients can be used to create boudins and nicely demonstrate the concept of "competency contrast." I was introduced to this model of boudin formation in Scotland, so "digestive biscuits" are my first choice, but graham crackers can be substituted.

Place a few layers of pre-sliced American cheese (NOT the cheese-"food" that comes individually wrapped) on a piece of wax paper, place the "diggie" on the cheese. Top with more cheese and another sheet of wax paper. Place a thick textbook on top of the wax paper and push down. Cut the stack to create a "road cut" to see the boudins. You can experiment with the competency of the cheese by warming it in a microwave oven on defrost for a few seconds.
submitted by Gayle Gleason


Desiccated cornstarch-water mixture makes an excellent analogue for jointed rock and provides an interactive introduction to some important features of joints and joint sets. With a jointed "outcrop" in a petri dish, students can interpret relative ages through abutting relationships, examine joint intersection angles, use joint surface textures to determine joint propagation direction, and evaluate the role of flaws in joint initiation.
submitted by Juliet Crider


A block of pottery clay deformed with a standard hydraulic rock trimmer produces beautiful conjugate fractures at approximately 30 degrees to sigma 1. This activity is relevant to multiple discussions such as:

  1. fracture orientation and principle stress directions,
  2. conjugate fractures, and
  3. Mohr-Coulomb failure.
The demonstration can either generate initial discussion about the fracturing of materials or serve as a follow-up activity to drive home the point that the theory really does explain observations.
submitted by Paul Kelso

Chocolate Block

A thick block of chocolate broken with a hammer to illustrate joint ornamentation (e.g. point of origin, plumose structure, arrest lines, hackle fringe). Since they know how the chocolate broke, students are pretty comfortable interpreting similar structures in hand samples.
submitted by Linda Reinen

Cranberry Jelly

Cranberry jelly comes from the can as a nice cylinder to use for measuring Poisson's ratio. This works best if you stick to just jelly (no berries). submitted by Linda Reinen