Just How Faithful is Old Faithful? Finding Order in Random Behavior

Module by: Tom Juster, University of South Florida

Cover Page by: Len Vacher and Denise Davis, University of South Florida

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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 use NPS monitoring data to determine the frequency distribution (histogram) of eruption intervals of Old Faithful. The module stresses the utility of the monitoring data: Development of geothermal energy outside the park could affect the hydrothermal workings of the geyser, and so the data establish a baseline for the eruption interval at Old Faithful. In the process, the students work through material on the concept of probability, the construction of histograms, and the use of Excel functions such as MAX, MIN, COUNT, and COUNTIF. They also watch an animation showing how a geyser works. The QL intent of the module is to introduce Geology of National Parks students to the frequency concept of probability and to have them create a histogram.

This material is based upon work supported by the National Science Foundation under Grant Number NSF DUE-0836566. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

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Learning Goals


Students will:

  • See on a map the relation between Yellowstone's geyser basins and the Yellowstone caldera.
  • See before-and-after photos from Nevada of a geyser turned off by development of a geothermal power plant.
  • Watch an animation adapted from the Yellowstone NP Web site showing how a geyser requires a heat source, water, earthquakes, and plumbing.
  • Follow on a graph from GOSA (Geyser Observation and Study Association) how temperature varies vs. time through an eruption and thus see how one can monitor the precise time of a geyser eruption.
  • Consider the difference between the classic definition of probability and the frequency definition of probability.
  • Be instructed on how to load Excel's Analysis ToolPack Add-in and build a histogram.
  • Create a frequency histogram of eruption intervals at Old Faithful for 2008.
  • Use the histogram to answer questions about the probability of eruptive intervals of various lengths.

In the process the students will:

  • Learn that geysers are fragile. Learn how a geyser works and, therefore, why they are fragile.
  • Be introduced to some of the how and why of the monitoring of thermal resources at Yellowstone.
  • Gain experience with probability, histograms and frequency distributions.

Context for Use


This module is designed for potential use in the Geology of National Parks service course at USF. The course is offered as an online course every semester. It includes readings from Parks and Plates, weekly quizzes based on that textbook, and weekly student activities designed to align the course with the University's general education requirements. This module is intended to be one of those activities, with the specific goal of meeting the gen-ed quantitative literacy dimension.

This module is one of four on Yellowstone NP, one of three on hydrothermal features, and one of two specifically on geysers. From least to most challenging, and most general to most specific, the order of the four modules is: (1) "Yellowstone! A National Park on a Hot Spot," (2) "A Percentage Stroll through Norris Basin," (3) this module, and (4) "Explore the Mean at Riverside Geyser." Much of the introductory material in this module is repeated in "Explore the Mean at Riverside Geyser."

Description and Teaching Materials


The module is a PowerPoint presentation with embedded spreadsheets. Click on the link below to download a copy of the module.

Optimal results are achieved with Microsoft Office 2007 or later; the module will function in earlier versions with slight cosmetic compromises. If the embedded spreadsheets are not visible, save the PowerPoint file to disk and open it from there.

The above PowerPoint presentation file is the student version of the module. It includes a template for students to use to complete the spreadsheet(s) and answer the end-of-module questions, and then turn in for grading.

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

The module is constructed to be a stand-alone resource. It can be used as a homework assignment, lab activity, or as the basis of an interactive classroom activity. This module together with the module about Riverside Geyser form a pair involving frequency distributions and histograms. The pair was used as a week-long out-of-class activity in Computational Geology (a QL course for geology majors) midway through the semester in Fall 2010 and Fall 2011 after the students had worked through a few other modules. The students considered these modules to be at an average level of difficulty, well in line with their expectations, and they appreciated the experience of constructing the histograms in Excel. The modules have not been implemented in the introductory-level Geology of National Parks course.


There is a slide at the end of the presentation that contains end-of-module questions. The end-of-module questions can be used to examine student understanding and learning gains from the module. Pre/post test, pre/post test answer key, and answer key for end-of-module questions are at the end of the instructor version of the module.

References and Resources

Old Faithful

The Geyser Observation and Study Association (GOSA)

SNOTEL website

US National Park Service (NPS)