Tsunami-Time

Tom Juster
University of South Florida, Tampa
Created: April 14, 2012
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Summary

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In this Spreadsheets Across the Curriculum activity, students use the shallow-water wave equation to compute the time it takes for a tsunami to travel across the ocean. Students are first introduced to the idea of shallow-water waves, and shows how they are defined and how their velocity is computed. They then compute travel times are computed from the velocity and distance. Using these skills, they finally apply these concepts to a hypothetical tsunami originating off the west coast of Portugal (where a giant earthquake occurred in 1755) by computing the travel time along several paths by dividing each into segments, each with a characteristic depth and therefore velocity.

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Learning Goals

Students will

  • Learn what tsunami are: how they form, what their characteristics are, and why they can cause damage so far from their sources.
  • Learn about the properties of shallow-water waves vs. deep-water waves, and why tsunami are shallow-water waves.
  • Use a spreadsheet to calculate whether or not a wave traveling in a basin of known depth is a shallow-water wave and, if it is, what its velocity would be.
  • Calculate the velocity of tsunami waves in different parts of the ocean.
  • Calculate travel times given a distance and a velocity, and apply this principle to the transport of sound waves from Krakatoa Volcano to Rodriquez Island in 1883. The relationship between travel time, velocity, and distance is the main quantitative concept in this module.
  • Use a spreadsheet to calculate the travel times for a hypothetical tsunami generated near Lisbon, Portugal, across the Atlantic Ocean.

In the process the students will

  • Learn that tsunami are singular waves caused by a disturbance that can travel across entire oceans at great speed.
  • Discover that the velocity of a shallow-water wave depends only on the water depth.
  • Discover that tsunami are shallow-water waves throughout the entire ocean, by virtue of their enormous wavelength.
  • Learn about tsunami risk to the eastern US.
  • Learn about the bathymetric regions of the oceans, and the different depths found in each.
  • Discover how the arrival time of a tsunami depends on its path, particularly how long it spends on shallow vs. deep parts of the ocean.

Context for Use

This module was designed for use in the Hazards of the Earth's Surface service course at USF. It assumes that students are familiar with basic Excel operations, especially the use of relative and absolute cell references and functions. The topic of tsunami would be appropriate in other geology courses as well.

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 is the student version of the module. The embedded spreadsheet consists of a template for students on which students complete their work and answer the end-of-module questions, and then turn in for grading. Since this module is designed as a stand-alone resource, instructions for extracting and saving the embedded spreadsheet are included in the PowerPoint presentation.

This module is offered in two versions: a traditional SSAC version and a new auto-feedback/graded (AFG) version. The AFG version: (a) provides automatic and immediate feedback to incorrect answers, including formulas; (b) requires students to complete tasks sequentially by not allowing them to advance until they've completed a task perfectly; and (c) automatically computes a grade and encrypts it into a code the students submit to verify successful completion. The files needed for this version can be accessed here .

Teaching Notes and Tips

This 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. It has been used as a mid-course module in Hazards of the Earth's Surface, an online service course at USF designed for non-majors, for the last two years. Students should be somewhat familiar with the concept of earthquakes, faults, and tsunami waves, though the needed math is introduced and explained in the module.

Assessment

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. The answer key for the end-of-module questions is at the end of the instructor version of the module.

References and Resources

Gutscher, M-A., 2004, What caused the great Lisbon earthquake? Science 305 (5688) 1247-1248.

Gutscher, M-A., 2006, The great Lisbon earthquake and tsunami of 1755: lessons from the recent Sumatra earthquakes and possible link to Plato's Atlantis, European Review 14, 181-191.

Tsunamis in the Atlantic Ocean, from the Maine Geological Survey, available at: https://www.maine.gov/DACF/mgs/hazards/tsunamis/index.shtml

Ward, S.N. and Day, S., 2001, Cumbre Vieja Volcan--potential collapse and tsunami at La Palma, Canary Islands, Geophysical Research Letters 28, 3397-3400.