Density of Rocks - Some Applications


This module studies some applications of knowing the density of rocks. One set of applications involves the: stress, strength, and factor of safety for a rock roof resting on one or more columns in an underground room. A second set of applications involves the normal and shear stresses, cohesion force, and inclination angle for a slab of rock resting on an inclined surface. Students recreate spreadsheets shown in the Powerpoint module on their own with formulas that answer various pieces of an overall question. This module is the fourth in a series of six that examine the density of planets and rocks.

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Learning Goals

  • Calculating stresses originating from the weight of overlying rocks.
  • Taking into account the factor of safety.

Context for Use

This module was designed to be used in an undergraduate mathematical geology class where students are asked to look at geological questions mathematically and may spend more time on the math than on the geology.

Description and Teaching Materials

This module is one of several developed by Dr. Vacher. The module presentation can be found at

The Powerpoint file is considered to be the student version. There is also an instructor's version that has active spreadsheets in it. There are instructions for requesting this version on the website.

Teaching Notes and Tips

These modules were developed as essentially self-paced, take-home lab assignments. Students are supposed to work through the modules, slide by slide, building their own worksheets as they go along, taking note of instructions and prompts, hints, and queries.

Students must have access to computers equipped with a spreadsheet program such as Excel.


The easiest way to test student work on this module is to ask students to hand in a copy of their worksheets starting with a different set of input data. The module also ends with homework assignment questions.

References and Resources