The word “tsunami” is Japanese for “harbor wave.” A tsunami is a series of huge waves caused by events that bring about a displacement of water. One such event is an earthquake. On March 11, 2011, an underwater earthquake (magnitude 9.0 on the Richter scale) occurred off the coast of Japan. The maximum water height when the wave hit land was 40 meters, and over 15,000 lives were lost. As the waves approached the shallower water near land, they slowed down and increased in height. The energy of the waves’ speed was transferred to height and force as it neared the shore.
Students will view before and after satellite images of the Japan event to generate interest and engagement in the phenomenon. Next the teacher will demonstrate a model of an ocean floor earthquake. Students will simulate the formation of an ocean wave and investigate the relationship of water depth to wave speed. They will collect data from their investigation and graph it in order to compare wave speed to water depth. Although the speeds of waves associated with tsunamis cannot be achieved in a wave tank, the mathematical relationship between wave speed and water depth can be demonstrated, resulting in curves on a graph similar to those found using tsunami data. The lesson will conclude with students participating in an online investigation that uses real tsunami data, which they can compare to their experimental data. The lesson includes an extension in which students may design a warning system based upon the information they have learned regarding ocean depth and how it relates to wave speed.
Lesson developed through a grant-funded project through Sweet Briar College and was originally available on STEM4Teachers.org.