**How Does Sea Floor Topography Affect Tsunami Wave Height?**

Joyce E. Patterson Stark

Albert Einstein Distinguished Educator Fellow

National Oceanic and Atmospheric Administration

Office of Education and Sustainable Development

Herbert Hoover Building Room 6863

14^th^ and Constitution Avenue NW

Washington D.C. 20230

<Joyce.Stark@noaa.gov>

Inquiry involves teaching that incorporates discovery. It will take
longer and the teacher may require more in depth knowledge before doing
the activity.

**Problem**

Students will discover how a V-shaped valley on the sea floor will
affect wave height, run-up and inundation distance, then design changes
in the sea floor and compare results.

**Teacher Preparation**

Using guided inquiry, the teacher will demonstrate the how to measure
wave height, run-up and inundation. Students should be familiar with
experimental design (hypothesis, materials, control, constant,
manipulated and responding variables). The manipulated variable will be
the V-shaped valley or the student's sea floor designs and the
responding variable will be the measurements for wave height, run-up and
inundation distance. The students will construct a V-shaped valley and
then collect data from their experiment. The V- shaped valley will be
narrower as it approaches the shore and wider as it faces the sea. It
will be open and not closed at the narrow end. The control will be a
sand beach with no materials added to the sea floor. Students should
decide what the control will be before starting to experiment. The
experiment should be repeated three times and the data averaged. This
part of the experiment and the data tables should be submitted to the
teacher for approval before beginning the experiment. The next part of
the experiment will be open inquiry. The students will modify the sea
floor using sand, rocks, and pebbles. They should be collected in
advance and kept in buckets or bags for group use. Students will submit
their designs and procedures for teacher approval before experimenting.

This inquiry experiment could be used for grades 6-9 with some
modifications for the younger students. This activity will take more
than one class period. A block of time would be the most effective.
Students should work in groups (3-4) but each student must write the
experimental design in their journal.

**Teacher Background**

[Wave height]{.underline} - vertical measurement of the wave before it
reaches the shore

[Run-up]{.underline} - vertical height a wave reaches above a reference
sea level as it washes ashore.

[Inundation distance]{.underline}- horizontal distance tsunami waves
reach landward from the shoreline

[Bore]{.underline} -- a traveling wave with an abrupt vertical front or
wall of water. Under certain conditions the leading edge of a tsunami
wave may form a bore as it approaches and runs onshore.

Contours of the sea floor and coastline have a profound influence on the
height of waves. In 1993, Okushiri, Japan, the wave run-up on the coast
averaged \~15-20 meters (50-65 feet). In one spot, waves pushed into a
V-shaped valley open to the sea, concentrating the water in a tighter
and tighter space. In the end, water ran up 32 meters (90') above sea
level (the height of an 8 story building).
<http://www.prh.noaa.gov/itic/tsunami_events/historical/summaries/1993.pdf>

When it reaches the coast, the wave can appear as a rapidly rising or
falling tide, a series of breaking waves or a bore. This simulation
shows what happens when a tsunami encounters land.
<http://www.geophys.washington.edu/tsunami/general/physics/runup.html>

Additional information about tsunamis can be found at this website:

[http://www.pmel.noaa.gov](http://www.pmel.noaa.gov/)

**Inquiry-generating Questions**

These are some sample questions to initiate discussion about tsunamis
before beginning the experiment.

1\. Have you ever walked form a sandy beach into the water? Is it always
sandy or does the structure of the sea floor change as you leave the
shoreline?

2\. What do you think run-up means?

3\. What does topography mean? What other word is similar to the ending
"graphy"?

4\. Do you know what a tsunami is? What causes a tsunami?

5\. Ask for ideas about inundation distance.

**Title**:

**Problem**:

**Hypothesis**: I believe ...........

**Materials**:

Stream or erosion tables or long plastic shoe boxes, sand, rocks,
pebbles, modeling clay, water, metric ruler, meter stick crossbar or
wooden doweling.

**Student Procedures**

1\. After setting up the stream table (erosion table), construct a beach
area using just the sand at one end of the table.

2\. Fill the stream table with enough water to cover part of the beach.

3\. Place the cross bar or wooden doweling in the water at the opposite
end of the beach. Move the bar back and forth or up and down to create
waves. Count the number of times the bar was moved (and/ or the
distance) to keep this constant for the experiment.

4\. Each student should have a job. One can record data in their journal
for sharing with other members of the team. One should measure wave
height with a metric ruler or meter stick. The ruler can be placed in
the water away from the shoreline. Another student can measure run-up on
the shore with a metric ruler. Another student can measure inundation
distance on the beach.

5\. The experiment should be repeated three times and the data averaged.
Graph your data.

6\. The control consists of no materials added to the sea floor.

7\. Construct a V-shaped valley from modeling clay and place it on the
sea floor before it reaches the beach. Turn in your experimental design
to your teacher for approval.

8\. After completing the V-shaped design, modify the sea floor by
constructing a design of your own. Turn in your experimental design for
approval before beginning to construct.

**Results**

1\. Compare and contrast the data from wave height, run-up and
inundation distance from your control, V-shaped valley and your design.

2\. Which design would cause more damage onshore?

**Conclusion**

1\. Was your hypothesis accepted or rejected. Explain why.

2\. What did you learn?

3\. In a summary paragraph, discuss the average data from your
experiments.

**Application**

How will your experiment be able to help people who live on coastal
areas prepare for tsunamis?

**Assessment**

The rough draft of the lab will be written in the journal. A 25 point
rubric will be used to evaluate either the rough draft or a final copy
for each student or the group.

Points

Title: 1

Problem: 1

Hypothesis 1

Control 1

Constant 1

Manipulated Variable 1

Responding Variable 1

Procedures: 3

V-shaped Valley

Sea Floor Modifications

Data Tables (2) 4

Graphs (2) 4

Results 3

Conclusion 3

Application 1

\_\_\_\_\_\_\_\_\_\_

25

**National Science Education Standards**

**Grades 5-8**

Content Standard A Abilities to do scientific inquiry

Understanding scientific inquiry

Content Standard B Motion and forces

Transfer of energy

Content Standard D Structure of Earth system

Earth's history

Content Standard F Natural hazards

Risks and benefits

Content Standard G Nature of science

**Grades 9-12**

Content Standard A Abilities to do scientific inquiry

Understanding scientific inquiry

Content Standard B Motions and forces

Conservation of energy and increase in disorder

Interactions of energy and matter

Content Standard D Energy in the Earth's system

Origin and evolution of the Earth system

Content Standard E Natural and human induced hazards