What is the primary cause of tsunamis?

The primary cause of tsunamis is underwater earthquakes or volcanic eruptions. When tectonic plates shift, especially at subduction zones where one plate is forced below another, it can result in a sudden displacement of a large volume of water. This displacement generates waves that can travel across entire ocean basins at high speeds.

In addition to earthquakes, volcanic eruptions occurring under the sea can also displace water enough to create tsunamis. The energy released during these geological events is significant enough to produce waves that can grow in height as they approach shallower coastal areas, leading to destructive tidal waves upon reaching shore.

High tides and storms, while capable of causing large waves, do not generate tsunamis in the same way; they are usually localized phenomena rather than the result of geological instabilities. Glacial melting and overfishing do not produce the rapid, large-scale water displacements necessary to create tsunami waves, making them irrelevant in this context.