What Causes Tsunamis
Title: What Causes Tsunamis?
Suggested prior lesson:
Suggested follow lesson: Tsunami impacts and shore slope
relationship
Grade level : 7-9
Unit : Tectonics, Natural Hazards, Emergency preparedness
Time required: 45 minutes for activity, plus additional for
discussion.
Abstract
In this lesson, students explore the mechanisms behind earthquakes and tsunamis and the relationship between them.
Students conduct experiments to explore tectonic movement and the possible trigger mechanisms for tsunamis. This
lesson involves recreating tectonics boundary interactions and the observing weather or not it is possible to create a
tsunami.
Prior knowledge/ background for students
It is helpful for students to have some background on the mechanics of plate tectonics and geologic processes such as
fault and boundary formation. Students should be aware of earthquakes and their relationship with Richter scale.
Objectives:
 Students will explore which
geological processes create
tsunamis
 Students will recreate tsunamis due
to above and below water
landslides, subduction faults and
impact strikes
Materials:
 Plastic containers (one per group) to
contain and recreate the tsunamis
 Plastic board (one per group) to act as
retainers and tectonic plates
 Sand/ gravel/ dirt to create each slide.
Attachments:
 Experiment
diagrams
 Tsunami fact
sheet
 Student
worksheet
(no answers
provided)
Suggested introductory questions /”Hook”:
If this subject is new to your students, consider introducing tsunamis with this short video explaining the basic life-cycle
of a tsunami. Many clips are available online, and can be used in this lesson.
Ask your students: Earthquakes occur many times a day around the world, and yet we don’t see hundreds of tsunamis
every day. Why not?
 Earthquakes need to be a certain size to generate a noticeable tsunami. Usually, earthquakes need to exceed 7
on the Richter scale in order to create a significant wave.
 The Earthquake will only cause a tsunami if the earthquake displaces water. This relates to where the earthquake
occurs and what kind of fault/geological process caused the earthquake.
Activity outline/ suggested procedure :
In this activity, students explore the mechanisms of tsunamis.
1. For part one, students will recreate a tsunami likely to occur at a subduction zone. Students will fill a container
with water and insert a plastic divider. The students will then lever the divider upward to mimic the release of
energy and material created by a subduction fault. Just as the land ‘snaps forward’ during a subduction
earthquake, the students will use their lever to suddenly push the water in their container outward. This video
highlights the geological process, and may be included during the summary of this experiment:
http://youtu.be/Wt_jJUnTFhg, and http://www.youtube.com/watch?v=bG37DEAb3Bc
2. For the next part of the experiment, have the students construct a small mound of damp sand and rocks on the
Prepared by Monika Pez, Ocean Networks Canada 2013
What Causes Tsunamis
plastic divider used in step one. Instruct the students to lift the divider so it is level with the side of the
container. Once it is level, have them quickly but smoothly lift back of the divider up, forcing the mound to slide
quickly into the container. This is an example of a tsunami caused by a massive landslide. This video contains a
dramatic computer generation of a possible tsunami created by the collapse of mount Mauna Loa.
http://youtu.be/RWbBiVxLzSs
3. For the final tsunami, have the students empty their containers and insert their divider about 2 inches from the
end of their container standing upright. Have students fill the small space with sand and rocks, and then, without
removing the divider, refill the container with water. The water should also cover the sand and rocks, at least
partially. When the set-up is ready, have the students pull the divider out of the container, quickly and smoothly.
This will allow the sand and debris to slip forward creating a tsunami. This video shows this process, but it has no
sound http://youtu.be/ixp704ar-pc
Suggested summary questions
Have the students revisit the initial question “why don’t all earthquakes cause tsunamis?” and allow them to discuss how
their answers may have changed. To further the discussion, have the students consider why strike slip faults (such as the
San Andréa’s fault) would be unlikely to cause a tsunami but a subduction fault (such as the Cascadia fault) is a high
tsunami risk.
You may also want to allow the students to revisit their experiments and discuss the different reactions they had. For
example, all the students will interpret the result differently, and they may want opportunities to retry their experiment
or consolidate their results.
Assessment options
You may ask students to document their results and assess their experiment for both consistency of results and their own
interpretation of their scientific process. You may also wish to challenge students to explore different experiment
parameters (amount of rubble, slope angle, volume of water etc.) you can then use this as an assessment of the critical
thinking skills.
Suggested additional reading, links, further information and connections:
 Monitoring the Cascadia subduction zone: http://www.neptunecanada.ca/news/news-details.dot?id=31191
 Types of tsunamis and their causes http://academic.evergreen.edu/g/grossmaz/springle/
Notes:
Prepared by Monika Pez, Ocean Networks Canada 2013