What is the Volume of a Debris Flow?

Module by Chuck Connor, University of South Florida, Tampa. This cover page by Ali Furmall, USF, now at U. Oregon
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This material was originally developed by Spreadsheets Across the Curriculum as part of its collaboration with the SERC Pedagogic Service.


In this Spreadsheets Across the Curriculum activity, students will learn a method by which to estimate the volume of volcanic deposits using data collected from the 2005 Panabaj, Guatemala debris flow. Students will estimate the area inundated by this debris flow and an average flow thickness in order to estimate the volume of the deposit. From this volume, the saturated flow volume may be estimated by examining high water marks on buildings. This is a self-paced activity in which students follow a PowerPoint presentation to create spreadsheets and graphs using Excel.

Used this activity? Share your experiences and modifications

Learning Goals

Students will:
  • Estimate area inundated by a debris flow from a gridded map.
  • Calculate the uncertainty associated with their estimations.
  • Calculate an average flow thickness over the covered area.
  • Learn an alternate geometric method for calculating the area of an irregular shape.
  • Develop a spreadsheet to carry out a calculation.
In the process the students will:
  • Begin to see the value of calculations based on approximate assumptions.
  • Consider relationship between planimetric area inundated by debris flow and debris flow volume.
  • Gain an understanding of uncertainty associated with making area and volume estimations.
  • Become exposed to the hazards and consequences associated with volcanic debris flows.

Context for Use

Equipment: Each student or pair of students needs a computer with Excel and PowerPoint.

Classes: This module has been used in an Introductory Physical Volcanology course with upper level undergraduates.

In the class, the module was introduced during lab to be completed as homework due the following week. Students turned in hard-copies of the Excel spreadsheets and graphs, as well as their working Excel files. This worked well for junior and senior level students with excellent quantitative skills.

Description and Teaching Materials

PowerPoint SSAC-pv2007.QE522.CC2.3-student (PowerPoint 1.3MB Nov10 07)

If the embedded spreadsheets are not visible, save the PowerPoint file to disk and open it from there.

This PowerPoint file is the student version of the module. An instructor version is available by request. The instructor version includes the completed spreadsheet. Send your request to Len Vacher (vacher@usf.edu) by filling out and submitting the Instructor Module Request Form.

Teaching Notes and Tips

This module, like the others in this collection, works best if coordinated with lecture and lab material.

If students have difficulty in getting their equations to produce the correct numbers in the orange cells -- especially if their results are off by orders of magnitude -- tell them to check their unit conversions. You cannot ever emphasize unit conversions enough.

Some students jump ahead to the end-of-module assignments without working through the main part of the module carefully. Those students have trouble.


The end-of-module questions can be used for assessment.

The instructor version contains a pre-test

References and Resources

Some papers using volume estimates in volcanology
  • For eruption magnitude
    Pyle, D., 2000, The sizes of volcanic eruptions, in Encyclopedia of Volcanoes, Academic Press, 263-269.
    Simkin, T., and Seibert, L., 1994, Volcanoes of the World, Geoscience Press.
  • Volcano volumes
    Tibaldi, A., 2001, Multiple sector collapses at Stromboli volcano, Italy: how they work, Bulletin of Volcanology, Volume 63, Issue 2-3, pp. 112-125
  • Debris flows and related phenomena
    Iverson et al., 1998, Objective delineation of lahar-inundation hazard zones, Geological Society of America, Bulletin110: 972-984.
    Siebert, L., 1984, Large volcanic debris avalanches: Characteristics of source areas, deposits, and associated eruptions, Journal of Volcanology and Geothermal Research, 22: 163-197.
  • Lava flows
    Watts et al., 2002, Growth patterns and emplacement of the andesite lava dome at Soufriere Hills Volcano, Montserrat, in The Eruption of Soufriere Hills Volcano, Montserrat, from 1995 to 1999, Geological Society of London Memoir 21, 115-152.
  • Tephra fallout
    Fierstein, J., and M. Nathenson, 1993, Another look at the calculation of tephra fallout volumes, Bulletin of Volcanology, 56: 121-132.