Chapter 14, Problem 84PP

Tsunamis are ocean waves generally produced when earthquakes suddenly displace the ocean floor, and with it a huge volume of water. Unlike ordinary waves on the ocean surface, a tsunami involves the entire water column, from surface to bottom. To a tsunami, the ocean is shallow—and that makes tsunamis shallow-water waves, whose speed is $v=\sqrt{gd}$, where d is the water depth and g the gravitational acceleration. Tsunamis can travel thousands of kilometers across an ocean to reach the shore with their initial energy nearly intact; when they do, they can cause massive damage and loss of life (Fig. 14.39).

FIGURE 14.39 People flee as the devastating tsunami of December 2004 strikes Thailand (Passage Problems 81-84).

For a tsunami to behave as a shallow-water wave, its wavelength

1. a. must be comparable to or longer than the ocean depth.
2. b. must be shorter than the ocean depth.
3. c. can have any value.