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Understanding Tsunamis image
Understanding Tsunamis
Grade level: 6-8 Subject: Earth Science Duration: One or two class periods
 


lesson plan support
Objectives
Students will
  • Discover the causes of tsunamis in oceans and fjords.
  • Learn that tsunamis in oceans and fjords can create great surges that cause much destruction.
  • Learn why ocean tsunamis and fjord tsunamis behave differently.
Materials
  • Our Changing Earthvideo and VCR, or DVD and DVD player
     
  • For each group: Two plastic containers with the same lengths but different widths; one should be significantly narrower.
  • Water
  • Small rock, ball of clay, or other object to drop in the containers
  • Ruler or tape measure
Procedures
  1. Review what students know about tsunamis. Discuss the causes of a tsunami: undersea earthquakes or landslides, volcanic eruptions, or the impact of a large meteorite in the sea.

  2. Tell students that a tsunami can also occur in a fjord, a narrow ocean inlet surrounded by cliffs. Portions of icebergs breaking, or calving, into the water can cause a fjord tsunami.

  3. Tell students they will perform an experiment to discover how calving icebergs can create different wave patterns in the ocean and in a fjord. Before the experiment, students should write a hypothesis about how wave patterns might differ in the two environments.

  4. Divide the class into groups and distribute materials to each group. Ask students how they can use these materials to test their hypotheses. Remind them that water depth should not be a factor in their experiments; they should consider the widths of water in an open ocean and in a fjord. (The wider plastic container represents the ocean, the narrow container represents a fjord, and the small object represents the calving iceberg.)

  5. Have students fill each container with water, using the ruler to make sure that the depth is the same in both containers.

  6. Next, students will drop an object from the same height into each container and observe the resulting wave patterns. Have students record their results.

  7. Hold a class discussion about the experiment. Ask students how they know that the difference in wave pattern was not due to differences in water depth. Have students hypothesize in which environment a calving iceberg might cause a greater ocean surge.

  8. Have each student draw a diagram showing the results of the experiment. A brief paragraph should describe each diagram.

  9. Hold a discussion to compare the effects of fjord tsunamis as a result of a calving iceberg and ocean tsunamis that are the result of an underwater earthquake.

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Evaluation
Use the following three-point rubric to evaluate students' work during this lesson.
  • Three points:Students' created carefully executed diagrams that clearly showed the experiment's results; wrote clear, accurate, and error-free descriptive paragraphs.
  • Two points:Students created diagrams that somewhat clearly showed the experiment's results; wrote satisfactory descriptive paragraphs that included some errors.
  • One point:Students created unclear diagrams; wrote vague descriptive paragraphs that included numerous errors.

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Vocabulary
crest
Definition:The top of a wave
Context:The crest of a wave may rise only a foot or two above normal.

fjord
Definition:A narrow sea inlet between cliffs or steep slopes
Context:The falling ice creates a wave that spreads rapidly across the fjord.

surge
Definition:A large wave or billow
Context:The water builds and then breaks into a huge surge that rushes ashore.

trough
Definition:The lowest point between waves
Context:For every wave peak is a trough. If the trough appears first, the sea recedes before a wave arrives on land.

tsunami
Definition:A series of catastrophic ocean waves generated by undersea earthquakes or landslides, volcanic eruptions, or the impact of a large meteorite in the sea.
Context:The word "tsunami" comes from the Japanese term for great harbor wave.

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Standards
The National Academy of Sciences provides guidelines for teaching science and a coherent vision of what it means to be scientifically literate for students in grades K-12. To view the standards, visit this Web site:http://books.nap.edu/html/nses/html/overview.html#content.

This teacher's guide addresses the following national standards:

  • Earth and Space Science: Structure of the earth system
  • Physical Science: Motions and forces; Transfer of energy
  • Science in Personal and Social Perspectives: Natural hazards; Risks and benefits

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