Which events can cause a tsunami?

• A. Underwater earthquake, landslide, eruption
• B. Tide currents and wind waves
• C. Oscillation of water in enclosed basin
• D. Rip current

Answer: (A)

A tsunami starts when a large amount of water is displaced rapidly, usually by vertical movement of the seafloor or the water column itself. An underwater earthquake can tilt or lift the seabed, pushing water upward and sending wave trains across the ocean. A submarine or coastal landslide suddenly displaces a huge volume of water, doing the same thing. A volcanic eruption near or beneath the water can also push water aside and generate tsunamis.

In contrast, tide currents and wind waves come from surface forces and regular energy inputs, not the abrupt, large-scale vertical displacement that creates a tsunami. The oscillation of water in an enclosed basin, called a seiche, is a different phenomenon tied to standing waves in that basin. Rip currents are localized surface currents, not a mechanism for generating tsunami waves.