Question

question 4 (1 point)
why do tsunami waves always behave as shallow water waves?
because they are caused by the gravitational attraction of the sun and moon.
tsunami waves are extremely fast, which means they feel the ocean bottom no matter where they are.
because waves generated by tsunamis do not have the same behavior as normal wind - generated waves.
the statement is incorrect; tsunami waves are never shallow water waves.
their wavelengths are long enough that anywhere in the ocean the water depth is less than their length.

Explanation:

Tsunami waves have very long wavelengths. In the ocean, even in deep - water areas, the water depth is much less than the wavelength of tsunami waves. Shallow - water wave behavior is determined by the relationship between wave length and water depth. When the water depth \(d\) is less than \(\frac{1}{20}\) of the wave length \(L\) (\(d<\frac{L}{20}\)), the wave behaves as a shallow - water wave. For tsunamis, since \(L\) is extremely large (hundreds of kilometers in some cases), and ocean depths (even the deepest parts like the Mariana Trench, about \(11\) km) are much smaller than \(L\), they always meet the condition for shallow - water wave behavior.

• The first option is incorrect because tides (not tsunamis) are mainly caused by the gravitational attraction of the Sun and Moon.
• The second option is wrong as the speed of a tsunami wave is related to water depth (\(v = \sqrt{gd}\), where \(g\) is the acceleration due to gravity and \(d\) is water depth) and the "feeling the ocean bottom" is related to the wavelength - depth relationship, not just speed.
• The third option is a misdirection as the key is the wavelength - depth relationship, not a comparison with wind - generated waves in terms of behavior origin.
• The fourth option is incorrect as tsunamis do behave as shallow - water waves.

Answer:

Their wavelengths are long enough that anywhere in the ocean the water depth is less than their length.